bai_giang_dtm_-1

CHNG IBI M U

Sinh vin cn nm Khi nim c bn v thut ng mi trng. Khi nim v quan trc v phn tch mi trng Xc nh c cc vn lin quan ti cht lng mi trng hin ti v tng lai. Vai tr ca phn tch ho hc trong nh gi cht lng mi trng.

I. MI TRNG V NH GA CHT LNG MI TRNG I.1. Mi trng (Environment) Mi trng bao gm tt c cc yu t l hc, ho hc, cc cht hu c v v c ca kh quyn, thch quyn v i dng. Mi trng sng l tp hp cc iu kin xung quanh c nh hng n c th sng, c bit l con ngi. Mi trng quyt nh cht lng v s tn ti ca cuc sng. I.2. Quan trc mi trng (Monitoring) v phn tch mi trng a/ Quan trc mi trng (Monitoring) Monitoring mi trng c nh ngha l qu trnh thu thp cc thng tin v s tn ti cng nh bin i nng cc cht trong mi trng c ngun gc t ngun thin nhin hay nhn to, qu trnh ny c thc hin bng cc php o lng nhc li nhiu ln v vi mt mu dy v c khng gian v thi gian t c th nh gi cc bin i v xu th cht lng mi trng. Do , monitoring cht lng c hiu l quan trc, o lng, ghi nhn mt cch thng xuyn, lin tc v ng b cc thng s cht lng cng nh cc thng s kh hu thu vn lin quan. Kt qu ca monitoring l nhng s liu. Theo UNEP monitoring mi trng c tin hnh nhm cc mc tiu sau y: (1) nh gi cc hu qu nhim n sc kho v mi trng sng ca con ngi, v nh vy s xc nh c mi quan h nhn qu ca nng cht nhim. (2) m bo an ton cho vic s dng ti nguyn (khng kh, nc, t, sinh thi.v.v) vo cc mc ch kinh t. (3) thu c cc s liu h thng di dng iu tra c bn cht lng mi trng v cung cp ngn hng d liu cho s dng ti nguyn trong tng lai.

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(4) nghin cu v nh gi cc cht nhim v h thng tip nhn chng (xu th, kh nng gy nhim). (5) nh gi hiu qu cc bin php kim sot lut php v pht thi. (6) tin hnh cc bin php khn cp ti nhng vng c nhim c bit. Monitoring ci g?, khi no?, u? v nh th no? c lm r ch khi mc tiu monitoring c xc nh. V vy, iu quan trng nht ca thit k mt chng trnh monitoring l phi thit lp c mc tiu monitoring. Cc bc thit k mt chng trnh monitoring c trnh by trong s di y. C th hn, quan trc mi trng cn cung cp cc thng tin sau: Thnh phn, ngun gc, nng /hm lng/cng cc tc nhn nhim trong mi trng. Kh nng nh hng ca cc tc nhn ny trong mi trng. D bo xu hng in bin v nng v nh hng ca cc nhn t ny.

Trn c s cc thng tin trn, c quan qun l mi trng c bin php cnh bo, qun l mi trng v thi hnh cc bin php khng ch, gim thiu tc ng nhim v s dng hp l cc thnh phn mi trng. V nguyn tc, tt c cc thnh phn mi trng (t, nc, khng kh, sinh vt) u cn c quan trc. Tuy nhin trong thc t hu ht cc quc gia, mng li h thng quan trc mi trng thng thc hin quan trc cc thnh phn mi trng ng (nc, khng kh) v cc thnh phn mi trng ny khng ch nh hng trc tip n cuc sng con ngi, sinh vt m cn c kh nng chuyn ti cc tc nhn nhim t vng ny n vng khc, gy tc hi cho mt khng gian ln, c bit khi c s c nhim mi trng. b/ Phn tch mi trng Phn tch mi trng c th nh ngha l s nh gi mi trng t nhin v suy thoi do con ngi cng nh do cc nguyn nhn khc gy ra. y l vn rt quan trng v qua chng ta c th bit c yu t no cn c quan trc v bin php no cn c p dng qun l, gip chng ta trnh khi cc thm ho sinh thi c th xy ra.


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Trong nhng nm gn y, nghin cu sinh thi khng ch l s tip cn v cht lng m cn v s lng. c th hiu bit v nh gi v mt h sinh thi i hi phi quan trc y s bin ng theo khng gian v thi gian ca cc yu t mi trng, c v s lng v cht lng c lin quan n cu trc v chc nng ca h. l cc tnh cht l ho v sinh hc ca h sinh thi. S di y minh ho cc bc cn thc hin trong qu trnh quan trc mi trng. Mc tiu

V tr v s lng im

Thng s gim st

Tn sut gim st

Phng php ly mu

La chn thit b

K thut phn tch

Phng php hiu chun Phng php ghi s liu

P/p trnh by kt qu

Cng b kt qu c/ Gi tr ca cc s liu trong phn tch mi trng quan trc v phn tch mi trng Cng vic kh khn i vi cc nh nghin cu l phi xc nh c nhng ch tiu phn tch no l cn thit. Vic xc nh thnh phn cc nguyn t l hay cn cn phi phn tch cc phn t hay nhm chc ca cc cht?


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V d: Khi phn tch hm lng t s cc nguyn t nh Hg, Pb, Cd... c th s khng nh gi c ht nguy c gy hi cho sc kho con ngi. iu ny cng tng t nh vic nh gi mi quan h gia hm lng tng s ca cc cht trong t vi kh nng s dng ca cy trng. Bi v, hm lng tng s c th l cao gi tr tiu chun tu thuc vo thnh phn m nhng nguy c gy hi ca chng l khng ln v ngc li. d/ Cc quan im v cht lng mi trng Vic kim sot, khng ch v qun l nhim i vi cc ngun im l tng i n gin. Trong khi i vi cc ngun khng im vic kim sot, khng ch v qun l l ht sc kh khn do khng th xc nh chnh xc cc ngun gc, v tr, qui m lan truyn cc tc nhn nhim. Vi l do nh vy, mt h thng quan trc cht lng mi trng vi mng li cc trm c nh o c, thu mu, phn tch, x l s liu cn c xy dng cho mi quc gia, khu vc hoc ton cu. nh gi cht lng mi trng c th da trn cc tiu ch sau: Cht lng mi trng t nhin c nh gi bng cc tnh cht l ho v sinh hc c trng cho cc thnh phn ca mi trng (t, nc, khng kh ) th hin thng qua cc thnng s v ch s mi trng. Cc yu t nh hng ti cht lng mi trng - ngun gc ca cc cht gy nhim. Tiu chun v cht lng t, nc, khng kh c qui nh da vo mc tiu s dng. Cc tiu chun c p dng i vi tng thnh phn mi trng c th tham kho trong phn ph lc. e/ Mng li quan trc phn tch mi trng ti nc ta Monitoring cht lng mi trng l mt trong nhng nhim v c bn ca k hoch bo v v qun l ti nguyn v mi trng. Theo kinh nghim ca cc nc tin tin, thit k mng li trm monitoring mi trng phi tnh n t nht l 4 yu t sau y:

iu kin t nhin (a hnh, t ai, kh hu, thy vn); iu kin ngun thi;


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iu kin cc h chu tc ng cc cht nhim (ngi, ng vt, cngtrnh,...);

iu kin chi ph (iu kin ny l rt quan trng).Trong monitoring mi trng ngi ta thng phi hp mng li trm c nh vi mng li trm di ng. Cc trm quan trc phi c chun ho v cc mt: v tr, a hnh, phng php ly v phn tch mu, trang thit b sao cho cc cc thng tin thu c phi mang tnh c trng, tin cy, c kh nng so snh. Ngoi ra, mt s vn quan trng khc lin quan n kinh t k thut cn xem xt v cn nhc khi thit k mng li trm, l: kh nng kinh ph u t, cc yu cu v nhn lc, thit b v nh gi s liu, s thnh tho nhn vin.


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II. GII THIU CHUNG V MT S KIN THC LIN QUAN TI QUAN TRC V PHN TCH MI TRNG II.1. Mt s kin thc c bn Cu hi: 1. 2. 3. 4. nh ngha v mi trng, mi trng c bao nhiu thnh phn? Cc vn c bn lin quan ti cc thnh phn mi trng l g? Th no l nhim v cht nhim? Nu mt cht nhim c thi vo mi trng, nguyn nhn (tng lng thi, nng ) gy nh hng ti i sng ca cc c th sinh vt?

Bng 1: Trch dn ngng khuyn co v gii hn ti a cho php ca mt s thng s trong mi trng nc do U ban Chu u khuyn co. STT Thng s 20 21 22 23 24 25 26 27 29 30 n v Ngng Nng Gi khuyn co ti a cho php 25 50 0.1 0.05 0.5 1 2 5 0.1 1000 0.5 Cn c nghin cu do lin quan ti s tng nng ca mt s nguyn t

NO3mg/l NO2 mg/l NH4+ mg/l mg/l N(NO2+NO3) Kh nng xy ho mg/l (O2) Tng Cacbon hu mg/l c (TOC) S Cc cht c chit bng Cloroform Phenol (C6H5OH) Brm (B) g/l mg/l g/l g/l

Cu hi: Nng ti a ca cc cht bng trn c th chp nhn i vi nc ung? Tr li: Nng cc nguyn t l khc nhau, tuy nhin nn quan tm ti nng ti a cho php biu din bng n vi mg l-1 (ppm) hoc g l-1 (ppb). II.2. S cn thit ca phn tch ho hc trong quan trc v phn tch mi trng Nu chng ta ch phn tch n cht v nh gi n, thng tin nhn c ch phn nh mt phn bn cht ca cht phn tch. Do vy, c cc thng tin y v trng thi ca cht, phn tch ho hc nn c thc hin. Cu hi:


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Hy lit k cc bc cn thit trong vic kim sot cc vn nhim bt u t bc nhn nh cht nhim. Ti mi bc vic phn tch ho hc no nn c thc hin? Tr li: 1. Nhn nh vn Nhn nh nn bt u t cc vn c th V d: Ma axt: Nguyn nhn c bn do cc kh SO2 v SO3 pht thi t vic t chy nhin liu than ti mt khu vc c th. Nhu cu nng lng ngy cng tng (giao thng, kh t in nng) dn ti s pht tn SO2 v SO3 sang nhiu khu vc khc. S b sung thm cc thnh phn ho hc khc nh NO v NO2 dn ti hin tng ma axt. 2. Quan trc vi mc ch xc nh phm vi ca vn Nh chng ta bit, trong mi trng tn ti hng nghn nguyn t thng qua cc qu trnh chuyn ho nng ca chng tn ti mc nht nh tu thuc vo tnh cht vn c ca mi trng, tuy nhin cng c cht khng tn ti trong mi trng m ch sinh ra t cc hot ng ca con ngi hoc tn ti trong mi trng dng vt. Quan trc nhm pht hin s thay i bt thng nng cc cht hoc cc cht khng c trong mi trng. Rt nhiu thnh phn ho hc c nghin cu t trc ti nay, tuy nhin rt kh khn trong vic nhn nh th no l mi trng khng b nhim. V d: Dioxin c php hin v chng minh c c tnh cao, Dioxin c ngun gc hon ton t cc hot ng ca con ngi, trong t nhin n ch tn ti dng vt. 3. Xc nh quy trnh kim sot Xc nh cc phng php tin cy trong vic phn tch cc i tng quan trc. 4. m bo cc quy trnh kim sot v thc hin ng lut i vi cc vn c tnh cht khu vc, quy trnh thc hin v kim sot yu cu thc hin ng cc quy nh ca khu vc. i vi cc vn ton cu, quy trnh thc hin v kim sot phi theo cc quy nh c tnh cht quc t. 5. Quan trc m bo cc vn mi trng c kim sot Tun th cc quy nh, tiu chun ban hnh i vi tng i tng c th. Cc kt qu quan trc phi c nh gi theo ng tiu chun ban hnh i vi tng i tng.


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Cu hi: Xem xt t cht thi ca mt nh my, cc cht bn t mt cng on sn xut v trong ton b cng on sn xut. Chng trnh quan trc, phn tch g nn dng nh gi v kim sot cht thi? Tr li: Phn tch ngun thi trc khi thi vo sng gip quan trc cht nhim tn ti trong ngun thi. Phn tch nc sng pha di ngun thi im vi khong cch ln cho php nh gi trc tip nng cht nhim trong nc sng, tuy nhin khng phi nh ng tnh cht ngun thi. Phn tch cht nhim trong cc sinh vt sng trong thu vc cho php xc nh cc ch th cho cc vn v mi trng, tuy nhin ch khi cc mu sinh vt c ly gn ngun thi xc nh v kt qu phn tch rt kh lin h vi cc ngun thi n l. c tnh ngun thi cng cho php m rng cc tng nghin cu. Ngoi ra cc quy nh v ngh nh v quan trc cht thi cng c nhng yu cu c bit i vi quan trc mi trng. II.3. Kin thc v s vn chuyn cc cht nhim trong mi trng Sinh vin cn nm c: D bo s vn chuyn cc cht nhim c th xy ra trong mi trng xut khu vc ly mu i vi cc thnh phn hu c c trng lng phn t cao v kim loi c th tch t. Xc nh ngha ca thut ng nhim bn v nhim


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Nh chng ta bit cc cht nh hng ti mi trng ph thuc vo nng ca chng v iu kin ca mi trng l tnh hay ng. Vt cht lun lun chuyn ho trong ba trng thi ca mi trng: kh, nc v rn. S vn chuyn ti mi trng thi lm thay i nng ca cc cht theo cc cch: vn chuyn, pha long hoc thay i nng .Trc khi bn v cc phng php chng ta cn hiu cc qu trnh chuyn ho ny c th: D bo v tr xut hin nng cht nhim cao nht nh gi nng o c ca cc cht nhim ti cc khu vc khc nhau trong mi trng. Chng ta cn hiu cc tnh cht l ho hc ca cc cht nhim. iu ny gip ch cho vic nhn nh cc dng nhim v gii thch to sao trong mi trng tn ti hng chc nghn ion v thnh phn ca chng nhng ch mt s t cc dng ion c tp chung nghin cu. a/ Ngun, s khuch tn, s tng nng v s phn hu Mi hot ng ca con ngi c nguy c dn ti nhim. Ngun nhim c chia lm hai loi: ngun im v ngun din. Cc cht trong mi trng nc v kh khuch tn theo cch ring ca n.


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S khuch tn ca cht nhim trong nc v khng kh chc chn s dn ti s pha long cht nhim. Nh chng ta bit, nh hng ca thnh phn ho hc trong mi trng c th lin quan trc tip ti nng ca chng, do vy qu trnh khuch tn s dn ti pht tn cc cht nhim trn mt din rng tuy nhin t gy nh hng ti im xa ngun thi. iu ny c bit c ngha khi chng ta xem xt ti s phn hu ca vi sinh vt, quang ho hoc cc qu trinh phn hu khc trn ng pht tn cht nhim do t lm tng tnh c. iu ny c th c hiu mt cch khc l s pha long cht nhim. V d: a) Kim loi c nh Cd, c th tm thy trong cc c quan ca chai, s nng ln ti 2 triu ln cao hn nhiu so vi nng Cd tm thy trong mi trng xung quanh. b) DDT, cht nng ho c s dng rng ri trong cc thp k trc, kh nng phn hu trong mi trng chm. Rt t vt cht hu c trn tri t tn ti dng vt (ng l-1) hoc nng ln.

Cu hi: Tnh cht l - ho hc chung nht cha mt cht c kh nng nh hng ti cc vn v mi trng? Tr li: S khuch tn l nguyn nhn ch yu dn ti s vn chuyn cc cht nhim i xa trong mi trng nc v kh. Cc tnh cht nh hng ti s khuch tn bao gm: bay hi, ho tan trong nc, cc ht cht rn v kch thc ht. Kh nng phn hu ca cc cht trong sinh vt bng cc phn ng ho hc. Nu mt cht phn hu nhanh s t c kh nng gy c v tng nng trong mi trng. Tuy nhin trong mt s trng hp cc sn phm phn hu c th gy bt li i vi mi trng. nh hng ca cu trc vt l ca cc vt th c kh nng lm tng nng ca cht nhim v sau nh hng ti i sng ca sinh vt.


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b/ S vn chuyn v tng nng ca cc thnh phn hu c trung tnh Cc cht hu c trung tnh thng rt d tng nng do tnh cht bay hi thp v c trng lng phn t cao (Mr>200). Chng thng cha cc nguyn t Cl trong cu trc phn t. Mt s cht thng thng c trnh by trong bng di y.

Cc cht c trng lng phn t thp thng thy ti cc khu vc b nhim khng kh. c/ Nng sinh hc Ngoi tr mt s cht hu c c cha cc gc phn cc nh OH, hoc -NH2 hoc ion, cc cht ny c kh nng ho tan trong nc thp, kh nng ho tan gim khi tng trng lng phn t (Hnh). Bt c mt cht hu c no b ho tan s d dng chuyn ho trong m cht bo. Cu hi: iu g c rt ra t kh nng ho tan ca mt cht trong nc v kh nng ho tan ca n tch t trong sinh vt? Tr li: Chng ta khng ngc nhin quy lut chung rng kh nng ho tan ca cht hu c trong nc hn nhiu i vi kh nng tch lu ca chng trong cc m cht bo v ln hn th nng gy c. Mt khc, do s ho tan trong nc gim khi tng trng lng phn t lin quan n nhm chc ca cc cht. Chng ta c th rt ra kt lun rng cc cht c trng lng phn t ln s gy ra nhiu vn mi trng hn i vi cc cht c trng lng phn t thp.


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Hnh di y m t kh nng tch lu ca sinh vt c o bng h s nng sinh hc, h s ny c tnh theo cng thc sau: H s nng sinh hc = Nng ca cht trong sinh vt / Nng ca cht trong mi trng nc.

d/ S tch t trong bn cn S tch t trong bn cn lin quan ti kh nng ho tan thp ca cc cht hu c c trng lng phn t cao trong nc cng vi tnh khng a nc ca cc cht hu c khng cha cc nhm chc phn cc. Vt cht hu c khng tan hoc kt ta trong nc s bm cht vo cc thnh phn rn. Din tch b mt ca cht rn ln s lm tng kh nng hp ph cc cht. y l hin tng thc t thng xuyn din ra ti cc khu vc tip nhn nc thi cng nghip v nhiu ht mn. e/ S khych i sinh hc


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ng vt s dng thc vt hoc cc ng vt khc lm thc n, Theo chui thc n nng cc cht c th tng ln tu thuc vo kh nng tiu th thc n ca mi loi. Nu mt cht nhim tn ti trong sinh vt u tin, nng cht nhim s tng trong cc loi k tip khi s dng cc loi ng trc n lm thc n. Hnh di y m t qu trnh khuch i sinh hc.

g/ S phn hu cc cht nhim Mc d cc cht him c xu hng chuyn ho trong sinh vt bng cc con ng c m t phn trn, nng tch t trong sinh vt s khng tng nu nh s phn hu ca cc cht nhim trong mi trng din ra nhanh. Cc cht s b ph v cu trc to thnh cc phn t n l, cc sn phm ny c th ho tan trong nc. S ho tan trong nc c th do cc nhm chc phn cc gn vo phn t hoc cht hu c c trng lng phn t thp. Tc chuyn ho cao ph thuc nhiu vo cu trc phn t. Mt trong nhng l do ti sao rt nhiu cht hu c trong mi trng c cha cc nguyn t Cl- v cc cht hu c ny c c ch phn hu chm. V d:


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C ch phn hu ca DDT xut hin hai trng thi c trnh by trong hnh di y. Trng thi u tin din ra rt nhanh, thng thng ch mt mt vi ngy, trong khi trng thi th hai din ra rt chm (vi thng).

h/ S chuyn ho v tng nng ca cc ion kim loi S ho tan Cc kim loi i vo mi trng thng trng thi khng tan trong nc thi cng nghip hoc mt phn c ngun gc t cc khong trm tch trong t nhin. Kim loi trm tch t khng kh ch yu dng mui khng tan. Tuy nhin, kh nng ho tan ca kim loi tng khi pH gim. Ma axt l nguyn nhn dn ti hin tng ra tri kim loi v hnh thnh cc dng kim loi c trong t. S kt ta kim loi trong bn cn Hm lng kim loi tng trong bn cn khi tng gi tr pH. S trm tch - kt ta xut hin khi nng kim loi ln. Cc ion kim loi cng c th tng tc vi bn cn bng mt s c ch bao gm cc c ch sau: hp ph


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trao i ion (cc khong st l nhng cht trao i ion t nhin) hnh thnh phc trong bn cn

S thay i cc iu kin kh hoc oxi ho trong mi trng nc dn ti s ho tan hoc kt ta cc ion im loi. V d: Fe b ho tan trong iu kin axt yu do vy ion Fe2+ tn ti ch yu trong dung dch trong khi trong mi trng kim, Fe b oxi ho v b kt ta di dng Fe(OH)3. Trong iu kin kh tt c cc ion sunfua (SO42-) b kh thnh sunfit (S2-) v c th dn ti s kt ta cc kim loi nh Pb v Cd di dng cc mui sunfit khng tan. S hp th bi sinh vt Nh tho lun trn, r rng s chuyn ho kim loi theo chui thc n. Nhiu kim loi b gi trong sinh vt dng ion n. Cc kim loi khc, c bit l Cd v Hg c th chuyn ho thnh cc cht c kim ho tr II. Do vy s phn b ca kim loi trong sinh vt ph thuc vo tnh cht ho hc ca chng. Cu hi: So snh l trnh khuch tn v s tng nng ca cc cht hu c c trng lng phn t cao v kim loi c trong mi trng v sinh vt. Tr li: Cht nhim c th c khuch tn trong khng kh v nc. S khuch tn trong khng khi ca kim loi thng dng ht (cc dng mui kim loi), nhng i vi cht hu c s khuch tn hai trng thi rn v bay hi. S phn hu c th din ra trong t v nc. Kh nng ho tan ca cc cht hu c trong nc thng thp, nhng c th lm tng nng sinh hc trong cc sinh vt sng di nc. Kh nng ho tan ca kim loi phc thuc vo cc tnh cht ho hc ca chng, pH gim s lm tng tnh tan ca kim loi. Tuy nhin pH li khng nh hng ti tnh tan ca cc cht hu c trung tnh. Cht nhim ch yu tp trung trong bn cn. C ch tp trung trong bn cn ca cht hu c c trng lng phn t cao v kim loi l rt khc nhau. V d, trong iu kin kh s lm tng s tch t Pb, ngc li khng nh hng ti cc cht hu c trung tnh. u vo trong chui thc n thu vc trong c hai trng hp l ging nhau, tuy nhin c ch chuyn ho trong sinh vt l khc nhau. II.4. Gii hn an ton Vic din gii cc s liu phn tch cn da trn c s mi quan h gia nng phn tch c v nh hng ca chng ti cc loi sinh vt mc d l khng d c th xc nh c mi tng quan ny. nh gi c tnh sinh thi c thc hin vi nhiu cht, tuy nhin khng phi cht no cng gy nh hng ti mi trng. Phng php gi c tnh sinh thi thng s


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dng bng cch xc nh liu lng hoc nng gy cht sinh vt nghin cu. LD50 l liu lng cn thit gy cht 50% sinh vt th nghim. Mt s phng php nh gi khc c th nh gi thng qua cc thng s nh: tc pht trin, t l ny mm, s tng hoc gim qun x II.5. CC THNG S NHIM CN KIM SOT a/ Khi nim chunng nhim mi trng (ONMT): nhim mi trng l s lm thay i trc tip hoc gin tip cc tnh cht vt l, ho hc, sinh hc ca bt k thnh phn mi trng no lm cho tiu chun cht lng ca thnh phn mi trng b vi phm dn n lm nguy hi hoc c kh nng nguy hi cho mi trng v sc kho con ngi (Cc Mi trng, 12/2000). Kim sot nhim mi trng (KSONMT): Kim sot nhim mi trng (KSONMT) l s tng hp cc hot ng, hnh ng, bin php v cng c nhm phng nga, khng ch khng cho s nhim xy ra, hoc khi c s nhim xy ra th c th ch ng x l, lm gim thiu hay loi tr c n. (Cc Mi trng, 2000). b/ Cc nguyn tc chung trong kim sot nhim mi trng: Kim sot nhim mi trng bt k mt lnh vc, i tng no cng u phi tun th nhng nguyn tc chnh sau: m bo s pht trin kinh t - x hi mt cch bn vng. m bo tnh lng ghp: i vi cc nh qun l, mt trong nhng trng tm quan trng i vi cng tc lng ghp l cch tip cn lin ngnh i vi cng tc kim sot nhim. Ngoi ra, nhu cu lng ghp xuyn sut cc trch nhim qun l mi trng nhm m bo tp trung c ngun lc v con ngi, cng ngh v ti chnh cho cc vn c u tin. Lng ghp cc khu vc, cc ngnh, cc i tng kim sot nhim vi nhau s to c hi thun li trong cng tc kim sot nhim, nht l trong khu tng hp, x l mang tnh khu vc tm ra cc quy lut chung nht. Ngn nga nhim mi trng l nguyn tc ch o trong cng tc kim sot nhim. Khc phc v phc hi l quan trng; Cc tiu chun mi trng, cht thi v tiu chun s dng cng ngh l ch da v cn c chnh. Mt s lu c th:


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Phi s dng cc thng s v ch th mi trng kim sot nhim . Phi thc hin nh gi hin trng v tc ng mi trng : phm vi, cc bc tin hnh. Cc tiu chun v mi trng : tiu chun x hay pht thi (emission or effluent standards); tiu chun cht lng mi trng bao quanh hay tiu chun cht lng ca ngun tip nhn cht thi (ambient standards).

-

Cc nguyn tc gim thiu ngay t ngun pht sinh, s dng li cht thi : vic gim thiu lng cht thi l mt hng rt quan trng, c ngha rt ln i vi cc cht thi, c bit nhng cht thi bn vng kh phn hu v nhng cht nguy hi. V vy vic gim thiu v s dng li cc cht thi l nhng vic lm rt cn thit nhng ng thi l nhng vic lm rt phc tp.

Quan trc cht lng mi trng (Monitoring Environmental Quality). xc nh hiu qu ca cc hot ng ci thin cht lng mi trng cn thit phi lng ho cht lng mi trng theo cc thng s mi trng : cc s liu v ngun thi v lng thi cc cht nhim; cc thng s cn quan trc, tp trung ch yu vo quan trc cc ngun thi gy nhim mi trng. II.5. Cc thng s cht lng hay nhim mi trng cn kim sot II.5.1. Cc cht nhim mi trng Cc cht gy nhim l nhng cht khng c trong t nhin hoc vn c trong t nhin nhng ti mt thi im no c hm lng ln hn v gy tc ng c hi cho mi trng t nhin, cho con ngi cng nh sinh vt sng. Cht gy nhim c th do hot ng ca con ngi (cht thi cng nghip v sinh hot) hoc do cc hin t nhin gy ra. Trong mi trng, cu trc ho hc cng nh nng ca n s quyt nh mc nhim ca mi trng nc, t v khng kh. Vic xc nh cc cht nhim rt quan trng. l c s cho vic xc nh ngun gc v mc nhim mi trng. Theo phng thc xut hin, cht nhim c phn loi thnh cht nhim s cp (xm nhp trc tip t ngun pht sinh) v nhim th cp (l nhng cht nhim c hnh thnh t nhim s cp trong iu kin t nhin). Tuy nhin tin li cho qu trnh kim sot nhim, vic phn loi cc cht nhim c xc nh da vo c tnh ca chng theo cc nhm nh sau: II.5.1. i vi mi trng nc v t


19

a. Cc cht hu c y l nhng cht tiu th xy trong mi trng nc. Do c tnh khng bn, chng c xu hng b xy ho thnh cc dng n gin hn. Qu trnh ny nh hng trc tip n ho tan xy trong nc (DO). Ngoi ra cc ch tiu khc mh BOD (nhu cu xy sinh ho) v COD (nhu cu xy ho hc) c s dng nh gi mc nhim hu c trong nc. Ngun gc cc cht nhim dng hu c c th t cc dng sau: Nc thi sinh hot: Hu ht cc cht hu c dng ny u c kh nng phn hu sinh hc. L nguyn nhn chnh gy ra hin tng thiu ht xy trong nc. Nc cun tri b mt: Thnh phn hp cht hu c rt a dng, tu thuc vo c tnh b mt. Sinh ra do qu trnh pht trin - cht ca ng thc vt ph du, ng thc vt y. y l ngun pht sinh ng k trong cc lu vc giu cht dinh dng. T hot ng ng sn xut hoc sn phm ca cng nghip: Thng thng cc cht hu c dng ny bn, kh nng phn hu sinh hc thp, gy nhim nng n cho cc ngun nc. l cc cht nhin liu, cht do, cht mu, thuc tr su, ph gia dc phm thc phm...m ngun gc t cc nh my thc phm, giy, thuc da, hp, ho cht, hoc do ti tiu.. * Mt s cht hu c tng hp in hnh tn ti trong t nhin gy nhim mi trng nc. l : Ho cht bo v thc vt: Bao gm thuc tr su, thuc dit c, thuc dit nm mc, dit loi gm nhm, thuc tr cn trng... Theo quan im ho hc cc cht bo v thc vt c phn thnh cc dng sau: Hp cht hu c halogen Hp cht hu c pht pho Cc cacbamat Cc clorophennoxyaxit

Cc cht bo v thc vt thm nhp vo c th con ngi thng qua qu trnh pht tn trong nc hoc do tn lu sinh vt, sau khi sinh vt cht b cun tri theo nc. Chng


20

c tch t trong chui thc n m mt xch cui cng l con ngi. Cht bo v thc vt c trong nc s tc ng trc tip n qu trnh pht trin ca sinh vt, thay i cu trc sinh hc, gy ra cc cc bnh l nh ung th, qui thai... * X phng v cc cht ty ra v ph gia: L nhng ngun tim tng cc cht nhim dng hu c do c kh nng to nh tng, to cc cht hu c l lng trong nc. Trong qu trnh ny cc anion to ra cc mixel x phng dng keo. * Cc cht hu c tng hp khc. Tt c cc cht hu c c trong nc u l nhng cht tiu th xy do c tnh khng bn v c xu hng xy ho thnh cht n gii. Trong nc khi ch s DO thp, BOD v COD cao chng t nc b nhim nng bi cc cht hu c tiu th xy. Mt s dng c trng ca cht hu c in hnh trong t, nc cn quan tm nh bng 20: Bng 20. Mt s cht nhim hu c in hnh trong t, nc TT 1 2 Loi hp cht hu c Hp cht hyrocacbon Hp cht halogen hyrocacbon V d Cyclohexen, Benzine, Benzen, toluen, Styren, Naphtalen, Benzopyren Chloroform, Vinyclorua, tetrachloethen, Hexachorychohexan, Hexachlobenxen, polyclorua, Byphenyl 2,3,7,8 tetraclo-dibenzodioxin Tributyphotphat Acrylamid,Acrylnitrit, O-nitrotoluen Methyclorua thu ngn Methyl-mercaptan Alkybenzensunfonat Methyl-hexanol, dipphenylether Formaldehyd, axeton, axitbenzoicPhenol, Cresol M, xt amin, lng trng trng

3 4 5 6 7 8 9 10 11 12 -

Plycloibenzodioxin Hp cht phtpho hu c Hp cht nit hu c Hp cht hu c kim loi Hp cht hu c lu hunh Cht hot ng b mt Alkohole & Ather ALehyt, keton Phenol Hp cht thin nhin

Cc hp cht hu c hyrocacbon mch thng hay mch vng thng thng l sn phm ca du m, thm nhp v lm nhim ngun nc thng qua cc qu


21

trnh khai thc, vn chuyn, gia cng, s dng. nh hng ca cc hp cht thm ny gy ra mi rt kh chu. i vi ngi v thc vt, chng gy nn cc bnh mn tnh v cp tnh nh ung th, nh hng n h thn kinh trung ng, mt, bnh ngoi da. Cc hp cht hyrcacbon a vng c cc ht keo hp th hoc bm dnh trn cc cht hot tnh b mt, do vy chng c kh nng tch t ln v cng c kh nng gy ung th. Cc hp cht hu c halogen l nhng cht v cng c hi. Cc hp cht ny bao gm: Cacbuahydro clorua, polyclorua byphenyl, thuc tr su cha clo, cc phnol clo, PCDD, PCDF. Cc hp cht plyclobiphenyl (PCB). y l nhng cht nhim c tm thy trong cc ngun trn ton th gii, thm ch trong c cc m t bo chim v c. Cc PCB c bn ho hc, nhit v sinh hc rt cao. Ngun gc ca PCB ch yu t dung dch lnh cch in, lm thm thu bng v si aming, lm ho cht do v lm cc cht ph gia cho mt s loi sn. * nhim du m: nhim nc do du m v sn phm ca chng (Xng, mazut, du bi trn,..) th hin nh sau: Lm gim tnh cht l ho ca nc (nh thay i mu, mi, v): Nc s c mi c trng khi nng ca n t ti 0.5 mg/l, cc ch tiu ho hc s thay i mnh khi nng ln hn 100 mg/l. Tc ng n qun th sinh vt: Nc b nhim gy thit hi v cng i vi sinh vt c nhy cm cao, qun th sinh vt gim xung rt nhanh do s phn hu ca du trong c th sng v do lp vng du ngn cn qu trnh trao i xy gia pha nc v kh. Hm lng du trong nc t 20-30mg/l s gy ri lon cc hot ng phn x ca c, hm lng ln hn c th gy cht c. Khi hm lng cc hp cht thm ca du t ti 0.3 mg/l th qun th sinh vt trong nc c th b cht.?? b. Cc cht nhim di dng v c


22

C rt nhiu cht v c gy nhim nc, t. Tuy nhin c mt s nhm in hnh cn lu nh sau: * Cc loi phn bn cht v c l hp cht v c m thnh phn ch yu l cacbon, hyro v xy ngoi ra chng cn cha cc nguyn t nh N, P, K cng cc nguyn t vi lng khc. Cc loi ho cht ny s i vo nc do mt phn phn bn b cun tri khi s dng, bc hi hoc chuyn ho thnh cc dng khc v lu tn trong mi trng. Vic d tha cc cht dinh dng (Pht pht, mui amn, ur, nitrat, mui kali ...) gy nn s pht trin nhanh ca mt s loi thc vt bc thp nh to, rong ru v cc thc vt thn mm, Gy nn hin tng thc vt cht hng lot. Chng b phn hu v to thnh lng ln hp cht hu c. Mt khc do pht trin t, mt lng ln xy trong nc s b tiu th gy nn tnh trng thiu ht xy mt cch trm trng (BOD cao), xut hin cc qu trnh kh, cc cht c tnh kh nh H2S, NH3 tng ln. Cc ion kim loi v HPO4- c chuyn ho t cc cht lng cn, ho tan vo nc gy c cho ngun nc mt. * Cc khong axt Ngun gc chnh l t cc m than khng cn khai thc. FeS2 (c nhiu trong m) l cht bn trong mi trng thiu xy. Khi tip xc vi mi trng khng kh, c s tham gia ca vi sinh vt s to thnh H2SO4 v Fe(OH)3 mu . S xut hin cc cht ny l nguyn nhn gy nn tnh trng mt cn bng sinh thi trong ngun nuc (ng thc vt cht) * Cn Ngun pht sinh do xi mn (ch yu) nc thi sn xut, sinh hot. Cc cht cn y thng trong tnh trng ym kh, tham gia qu trnh kh, gy nn tnh trng thiu ht xy trong nc. Cc cht cn l lng v ht huyn ph l mi trng hp th rt tt, chng nh l cc kho cha cc kim loi nng nh Cr, Cu, Mo, Ni, Co, Mn ...gy c cho ngun nc. * Cc nguyn t vt


23

y l cc nguyn t c rt t trong nc, tuy nhin kh nng gy c rt cao cho h sinh thi v con ngi. Mt s nguyn t vt cn lu trong qu trnh kim sot cht lng nc bao gm: Bng 21. Cc nguyn t vt trong nc Nguyn t Arsen Cadmium K hiu As Cd Ngun gc cc loi khong, thuc tr su, cht thi ho hc Cht thi cng nghip, qung, m kim loi Tc hi c, c kh nng gy ung th Thay th km trong qu trnh sinh ho, gy huyt p cao, au thn, ph hu m t bo mu, nhim c cc sinh vt di nc Vim nga da, ni mn Nhim c mt s thc vt Nhim c thc vt v to Gy hng rng, mm xng c vi thc vt hm lng cao c, nh hng ti thn v thn kinh Rt c c vi hm lng cao

Crom Boren ng Flo Mangan Ch Thu ngn Selen

Cr Bo Cu F Mn Pb Hg Se

M kim loi, sn phm gc Crom Than, cht ty nc, n thi cng nghip M kim loi, tuyn khong, khai m Ngun a cht t nhin, cht thi cng nghip Cht thi cng nghip m Cng nghip, m, than du kh Cht thi cng nghip than, thuc tr su Ngun nc t nhin, qung sunfua, than

Ngoi cc nguyn t vt, cc cht phng x cn c quan tm trong vic kim sot nhim phng x trong mi trng nc trong tng lai. II.5.2. i vi mi trng khng kh Cc cht nhim trong khng kh cng bao gm cc cht hu c, v c v vi sinh vt. Bng 22 l mt s cht nhim khng kh t cng nghip v th. Bng 22 . Mt s cht nhim chnh ca cng nghip v tc ng bnh l ca chng i vi sc khe con ngi TT Cht kh nhim Ngun pht sinh Tc dng bnh l i vi ngi


24

1

Andehyt

2

Amoniac NH3

3

Asin (AsH3)

4

Cacbon oxit CO

5 6

Clo Hydroxyanit

7

Hydroflorua HF

8

Hydrosulfit H2S

9

Nito oxit NOx

10

11 12

Photgen (cacbon oxyclorua) Sulfuro SO2 Tro, mui, khi, bi mn

Gy nguy hi i vi ton b ng h hp v mt. Gy tc hi i vi t bo thn kinh, au u v lm kh hng, m mt. Tinh luyn du kh, khc Gy mt mi ton thn, vim knh bng axit, sn xut da, gy bnh v thn v xng aluminium v phn bn, sn xut snh s, gm, thy tinh Cng nghip ha cht v tinh Mi ging nh mi trng thi, luyn nhin liu c nha gy bun nn, gy kch thch ng, cng nghip cao su, mt v hng. phn bn NG X KHI CA T, Gy nh hng n b my h XE MY, CNG NGH hp, mui xm nhp vo phi lm mm ha than Cng nghip ha hc v Gy ho, bun phin, nguy him nhum i vi ngi bnh h hp. Qu trnh t than v du Gy tc ngc, au u, nn ma, t vong do bnh h hp. Gy bnh kh thng, au mt v c th gy bnh ung th, cc bnh ng h hp. Bnh ng h hp, cc bnh v thn, cc bnh ung th

T phn ly cc cht du, m v glyxerin bng phng php nhit Qu trnh ho hc sn xut phn m, sn hay thuc n. Qu trnh hn ni st thp hoc qu trnh sn xut que hn c cha axit asen (arsenic) NG X KH XE MY, T, NG KHI T than, du Ty vi, si v cc qu trnh ha hc tng t. Khi phun ra t cc l ch bin ha cht, m kim loi

Gy bun phin, cu gt, lm nh hng n b my h hp Gy vim ty ng h hp

Lm gim hng cu trong mu, tc hi thn, gy mc bnh vng da Gim bt kh nng lu chuyn oxi trong mu.

13

14

T l t mi ngnh cng nghip v ng x kh ca xe c Bi, hi ch v Sn xut sn, mu, m kim cc kim loi nng loi, luyn kim, t cht thi rn y t v cng nghip. khc Cc kh axit (HCl, Cng nghip ha cht, m Bnh ng h hp, chng mt, H2SO4, HNO3...) kim loi, ty ra, t cht bun nn, co git, vim phi, thi nguy hi. vim da, nguy hi i vi h25


15

thn kinh... VOC, HC mch Cng nghip ha du, cc Vim ty mt, d ng da, bnh thng, mch vng, loi dung mi ha m phm, ng h hp, h tun hon Halogen sn xut sn, vecni, xng du mu, h thn kinh xe

II.5.3. Cc ch tiu hay thng s cn kim sot i vi khu vc th v khu cng nghip xc nh mc nhim mi trng nc, cn thit phi xc nh cc ch tiu hay cn gi l cc thng s cht lng nc nh trn. Thng thng cc thng s ny c quan h mt thit vi nhau, v vy khi nghin cu nh gi cht lng nc, cn thit phi xem xt mt cc cn thn, chun xc. Cc thng s ny c chia thnh cc nhm: vt l, ho hc v sinh hc. Nhm ch tiu Vt l : nh gi mc nhim hay cht lng nc theo cc ch tiu ny ngi ta xc nh nhit , mu mi, trong, c hay hm lng cn rn l lng, tng hm lng cc cht rn, dn in,... Mi: Nguyn nhn to ra mi, l cc qu trnh phn hu cht hu c (to mi thi), hoc mi tanh ca st. Nh vy, thng qua mi c th nh gi mc phn hu cht hu c (hiu kh, k kh), qu trnh pht trin ca ng thc vt ph du,... Mu: Cn c ch th mu c th nh gi s b cht lng nc. V d : cn c mu xanh xc nh mc dinh dng trong sng h, nh hng ca nc thi cng nghip c mu c trng, nh hng cc b bi nc thi sinh hot c mu nwu xm, ngun nc trong mi trng k kh H2S tc ng vi Fe+2 to thnh FeS c mu en,... Cc cht rn hay cn l lng thng l cc cht b cun tri theo dng nc, do xc ng thc vt cht hay do hot ng ca ngi, sc vt,... to ra. Hm lng cn ln s lm gim kh nng t lm sch ca ngun nc, cn tr qu trnh sinh thi din ra trong nc hoc cn tr qu trnh dit khun trong nc. Trong qu trnh kim sot cht lng nc, tu tng trng hp c th cng nh c tnh cht pht thi m ta a ra cc cht nhim cn kim sot cng nh cc ch tiu nh gi cht lng ngun nc.


26

Nhm ch tiu ho hc y l nhm ch th rt quan trng. Trng thi tn ti ca chng phn nh r nt cht lng ngun nc cng nh nguyn nhn chnh gy nn. pH: Biu th nng H+ trong nc. nu pH b hn 7, nc c tnh axit; ln hn 7 c tnh kim; bng 7 c tnh trung tnh. Cht nc trng thi bnh thng pH = 6-8.5 (ngun A) v 5.5-9 (ngun loi B) Nhm nhim hu c:

c trng cho nhm ny l BOD ( nhu cu xy ho sinh ho) v DO (xy ho tan). Cc thng s ny phn nh y trng thi nhim cht hu c trong ngun nc cng nh trng thi ca h sinh thi ca n (quan h cht ch vi qu trnh sinh vt trong nc v bn y). ng thi vi BOD cn phi xc nh nhu cu xy ho hc (COD). Ngoi cc hp cht hu c tc ng n nng xy trong nc cn c cc hp cht v c nh ammonia, nitrite, Sulphit, Hydrogen sulphit, Fe2+ . Mc dinh dng:

c trng cho nhm dinh dng l nit v phopho. S c mt ca cc hp cht ny chng t nc ngun b nhim bn bi nc thi sinh hot. Hp cht nit l thnh phn quan trng cho qu trnh sng ca thc vt, ng vt trong nc. Lin quan n hp cht ny l qu trnh ph dng, gy ra hin ti nhim bn ln th hai. Cn c vo nng ca chng ngi ta phn ra cc trng thi ngun nc nh sau: Bng 23. Phn loi ngun nc theo mc dinh dng Trng thi h, sng Thc vt l Tng cacbon hu c (mg/l) lng 3 (mg/cm ) 20 -50 50-100 100-300 >300 3-30 1-3 1-5 5 - 30 Tng P (g/l) 1-5 5-10 10-30 30 - 500 500-5000 Tng N (g/l) 1-250 250 - 500 500-1100 1100-1500 > 1500

Rt ngho dinh dng Ngho dinh dng Dinh dng trung bnh Ph dng Dinh dng qu cao Ngun: Jorgensen, 1980


27

CHNG II. QUAN TRC MI TRNG I. QUAN TRC MI TRNG I.1. CC VN LIN QUAN TI QUAN TRC MI TRNG NC I.1.1. Nc ngm Nc ngm l nc c trong cc lp thm di mt t. Hnh di y m phng qu trnh lu tr nc di cc lp t sau ma. Nc di t tn ti hai tng: tng khng bo ho v tng bo ho (phn lp y cc khe rng), nc ngm tn ti trng thi t do. Tc thm khc nhau tu theo loi vt cht ca lp t di tng t mt: tc dng chy qua cc ht ct l thng t 1 n 5 m/ngy, qua si 6 10 m/ngy v qua t tht v st tc thm ch khong vi mm hoc cm/ngy. Cht lng nc ngm v d nh loi v hm lng cht ho tan c xc nh bng mt s tnh cht ca t, tc thm cng nh thi gian v su.Kt ta Khu vc khng bo ho

Mao qun

Mt nc ngm

Nc khng b gi

Lp khng thm

Nc b gi

Lp khng thm Rock water


28

a- Thnh phn ca nc ngm o c cht lng nc ngm ng vai tr quan trng trong vic xc nh cht lng nc. Yu cu cht lng ph thuc vo d nh v cc mc ch s dng nh nc ung, nc cng nghip, nc ti. M rng ra c th s dng ngun nc ngm cho cc mc ch khc hoc cc hot ng ph thuc vo thnh phn t nhin ca nc ngm v t cc nh hng do hot ng sn xut ca con ngi. Trng thi vn c ca nc ngm trong t nhin cha cc dng kh b ho tan nh O2, CO2, CH4, cc ion v c nh Ca, Mg, Na, K, Cl, NO3, SO4, HCO3, cc thnh phn hu c nh humic, fulvic v amino axt, v khong rng cc dng cht v c khc tn ti di dng vt. Ni chung, cc tnh cht ho hc ca nc ngm s phn nh tnh cht khong vt hc ca lp trong a tng. Kh CO2 b ho tan trong nc ma v thm nhp qua t, hnh thnh mt axt yu phn ng vi cc khong trong cc lp a tng di su. Trong cc a tng c cha cc khong cacbont ( vi hoc ct ccbont) nhng khong ny s b ho tan gii phng ra Ca, Mg v HCO3- trong nc ngm. Nc ngm trong cc a tng hi chua khng cha cc khong cacbont, lng oxy ho tan ban u tn ti trong lp nc ngm pha trn c th b loi b bng s xut hin cc phn ng sinh ho di cc tng su, iu ny dn n cc a tng thiu kh mt cch t nhin. Cc qu trnh ny c th nh hng n nng ca Ca, Mg, K, Na v SO42- thng qua cc phn ng nh: trao i ion, s kh SO42- ca vi khun, s xi ho FeS, v s ho tan ca CaSO4 trong a tng. Nc ngm cng bao gm nhiu thnh phn mui, nng tng theo chiu su v nng ca cc thnh phn b ho tan tng khng i bi s ho tan khong lin tc. Cht lng nc ngm c nh gi thng qua o c cc thnh phn ca nc, kt qu s th hin tnh bn vng i vi cc hot ng ca con ngi v cc mc ch s dng khc. Cc ch tiu phn tch bao gm xc nh cc ch tiu pH, tng cht rn ho tan, dn in, cc mui v c nh c cp trc . Phn tch cc thnh phn ho hc c th kim tra tnh chnh xc thng qua cn bng ion, bng cch so snh nng ca cc cation v anion biu din bng li ng lng trn lt (meq l-1). Thnh phn ca mu nc c o c trn c s cn bng ho hc, tnh bng s lng v du in tch ca cc cation v anion. Mu nc nn c trung ho v nng ng lng meq l-1 ca cc cation v anion cng nn cn bng. S sai lch trong khi cn bng ion c th cho thy sai s trong qu trnh ly mu hoc trong qu trnh phn tch. th din t cc


29

thnh phn ca nc ngm nn s dng cc dng th dng thanh ng, dng mng, v dng tam gic. th dng tam gic c bit hu ch i vi s phn loi cht lng nc ngm. i vi cc nghin cu y v cht lng nc ngm lin qua n s quan trc cht lng v bin php khc phc cc a tng b nhim bn, cn yu cu b xung thm mt s phn tch c bit, ch trng vo vic xc nh cc dng b ho tan bao gm mt khong rng cc cht hu c t nhin hay tng hp, vi khun, x khun, cc sn phm hu c v v c t qa trnh phn hu ca vi sinh vt c th tn ti trong cc a tng b nhim bn. Cu hi: Nc ngm l lp nc di b mt t v hnh thnh nh qu trnh a cht m nc trng thi bo ho. Nu c gi trong tng thm nc c th c ly s dng. Vy, lm th no phn bit thnh phn ca nc ngm khc vi nc mt? Tr li: Nc ngm c th tp trung nhiu mui ra tri t cc trm tch khong. Trong qu trnh chy qua b mt, nc s tip xc vi cc khong hu c c th phn hu. iu ny lm cho thnh phn oxy trong nc ngm thp hn. b- S nhim bn nc ngm S nhim bn cc a tng bi cc cht v c v hu c gy nh hng ti cht lng ngun nc ngm trong mt thi gian di. Cc cht bn i vo nc ngm t cc hot ng ca con ngi v c th thay i nng t ngun nc ngm ny sang ngun nc ngm khc ph thuc vo mt ca cc ngun gy nhim. Cc cht nhim bn c phn nhm nh sau: nhm nuclit phng x, cc nguyn t vt, cc cht dinh dng, cc dng cht v c khc, cc cht nhim bn hu c, cc cht nhim bn vi sinh vt. Mt khong rng cc cht nhim bn i vo nc ngm t cc ngun thi th t cc cng thi v chy trn. T cc hot ng sn xut nng nghip nh s dng phn bn, ho cht bo v thc vt, ph thi l nhng ngun chnh khuch tn NO3- v cc thnh phn hu c vo nc ngm. Cc cht nhim bn dng ho cht hu c tng hp, ph thuc vo cc ngun thi khc nhau m thnh phn cc cht c th khc nhau n hng nghn ln. ban u ca + thu quyn Tnh cht Thay i tnh cht + Dung dch S thay i cht lng nc c th xem xt l do s ph thuc vo cc tnh cht th nhng v a cht vn c trong t. Tng lng cn bng nh sau:


30

Thay i cc iu kin t nhin ca lp di tng su dn n hnh thnh cc vng c cht lng nc c bit. Nhng nhm ny c th d dng nhn ra trong biu dng tam gic di y. Nc ngm di cc tng t cha t cation kim thng tn ti di cc dng sau: a) ch yu dng CO32b) HCO3- v SO42c) Ch yu dng SO42Nc ngm di cc tng t cha nhiu cation kim d) ch yu dng HCO3e) ch yu dng SO42Nc c tnh kim f) ch yu dng HCO3g) ch yu dng SO42- v Cl-

Khong nng ca mt s nguyn t chnh trong nc ngm ph thuc vo loi nc ngm trnh by bng 2 di y. Bng 2. Nng mt s nguyn t chnh trong nc ngm Loi nc ngm tn ti trong mt s loi


31

Thng s bin cht mg/l + Na 5-15 K+ 0.2-1.5 4-30 Ca2+ Mg2+ 2-6 -3 Fe2+ 3-30 Cl NO30.5-5 10-60 HCO321-20 SO4 SiO3 - 40

ct kt mg/l 3-30 0.2-5 5-40 0-30 0.1-5 5-20 0.5-10 2-25 10-30 10-20

cacbont mg/l 2-100 -1 40-90 10-50 - 0.1 5-15 1-20 150-300 5-50 3-8

thch cao mg/l 10-40 5-10 - 100 - 70 - 0.1 10-50 10-40 50-200 - 100 10-30

mn mg/l - 1000 - 100 - 1000 - 1000 -2 - 1000 - 1000 - 1000 - 1000 - 30

C rt nhiu nguyn nhn gy nn nhim bn nc ngm, c bit l cc lp nc pha trn. Mt trong nhng nguyn chnh gy nhim bn nc ngm l thi quen s dng. Nc ngm c s dng trong nhiu mc ch do vy vic la chn cc ch tiu phn tch phi da trn mc ch nghin cu. Bng 3 lit k cc thng s c th tham kho trong cc nghin cu v cht lng nc ngm. Cc thng s thay i tu theo mc ch s dng nc hoc nghin cu v nhim mi trng. Bng 3. La chn cc thng s trong nghin cu cht lng nc ngm Phn tch 1) Nghin cu cm quan Mu, mi, dc 2) Tnh cht L Ho hc Nhit pH dn in (EC) Th kh Cht rn S hp ph ti 254 nm 3) Phn tch theo nhm nguyn t Tn d Bi Kh nng xi ho Cabon hu c b ho tan Ch th phenol cng Nghin cu tng quan v nc ngm X Kim tra Kim tra s tnh n nhim bn mn nc ngm X X Cc nghin cu nng cao X

X X X X X

X

X X X X

X X X X X

X X32

X X

X

X X X X X


c t 4) Cc cation, anion, vt cht khng lin kt Na K NH4+ Ca Mg Fe tng s Fe2+ Mn HCO3ClNO3NO2FCN SO42SO2 PO43Axt Silic Oxi CO2 t do 5) Cht v c dng vt Asen Cadimi Crm ng Ch Thu ngn Nikel Km 6) Cht hu c dng vt Hydro cacbon halogen bay hi Hydro cabon Hydro cacbon halogen khng bay hi Hydro cacbon a vng 7) Cc thng s sinh hc Faecal E Coli Cc c th sinh vt th a bo I.1.2. Nc mt

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

X X X

X X X

X X X

X X X


33

Cu hi: Theo bn c bao nhiu loi nc trn tri t? Tr li: Cc dng nc khc nhau c th c phn loi nh sau Nc mt (sng, h, nc ma chy trn) Nc ngm v nc sui Nc thi Nc nhim mn Nc l v nc mt Nc trm tch v nc ngng t (ma, tuyt) Nc lm mt Nc ung Nc Nc bc hi Nc b gi trong cc tng t pha di Nc r r

Nc mt c th di dng dng chy hoc dng nc ng. Nc mt hng chu cc cht nhim bn i vi mi trng bi vy phi c c bit ch . Mc nhim lun lun ng hnh vi s thay i trng thi ca h sinh thi. Mt thc t l cht lng nc mt ti thiu phi c m bo duy trnh trng thi sch vn c ca n. c tnh ny c th do t nhin hoc cht nhim bn hu c ngoi lai c phn hu t t qu trnh t lm sch. nhng thu vc giu oxy, cc vt cht c th phn hu b ph v cu trc bi cc hot ng ca cc vi sinh vt hiu kh. m bo cho cc hot ng ny, oxy cn cho cc phn ng do vy dn ti gim lng oxi ho tan trong nc. S phn hu cc hp cht hu c dn n sinh khi c hnh thnh, kt ta cc vt cht hu c di dng cn. Cu hi: 1. Theo anh/ch, thng s no thng xuyn thay i nng ? DO NO32. Loi no c thng s DO cao nht?

Loi sng no c kh nng thm nhp oxy nhanh?


34

o Sui c dng chy mnh o Sng c dng chy chm trong khu vc c hot ng cng nghip nng o Sng c dng chy chm ti cc vng nng thn Tr li: 1. Oxy l sn phm c to ra t qu trnh quang hp trong ngy, tuy nhin n b ly i bi s h hp hoc s oxy ho lin tc ca cc vt cht hu c. iu ny s din ra lin tc nhng thay i rt chm trong khng kh. Nng oxy h xung vo ban m. S bin i ca Nitrat rt phc tp. y l cht dinh dng cn thit cho s sng v nng gim vo ma h v tng vo ma ng; tuy nhin, nu s dng qu mc phn bn Nit s lm tng bt thng nng ca n ti cc thu vc ln cn do qu trnh thot nc. 2. S bt thng v a hnh ti cc sng, sui m bo lng oxy c thm nhp nhanh v nc lun c bo ho oxy. iu ny khng ging vi sng c cha lng ln cc vt cht hu c hoc nc thi t cc khu cng nghip. Nhu cu oxy lun thp. Sng c dng chy chm, kh nng thm nhp oxy chm. Ti cc khu vc cng nghip nng, dng thi tiu thu oxy do vy s lm tng nhu cu oxy ti ngun nc tip nhn. Sng ti cc khu vc nng thn t cha cc cht thi tiu thu xy nhng vn c nhu cu oxy cao do cc vt cht lng ng v cc vt cht b vn chuyn ti cui ngun. Kim tra cc tnh cht l ho hc cung cp cc thng tin quan trng v tnh trng ca nc, nhng cht c th gy nhim hoc bn cht ca chng v chc nng ca qu trnh t lm sch. Tuy nhin, trong cc trng hp c bit cng cn kim tra b thm mt s tnh cht sinh hc cung cp cc thng tin y v cn thit cho vic nh gi cht lng nc. c th so snh cc kt qu phn tch, xin c gii thiu ch s Saprobic Index th hin s sng hoc s tn ti trong mi trng giu cht hu c nhng thiu oxy. Ch s ny da trn vic bit trc cc sinh vt xc nh hay ni cch khc l sinh vt ch th ch c th nhn thy c trong nc khi nc c cht lng tt. Cc kt qu o cc ch s sinh hc thng c km theo mt s thng s khc nh nng NH4, O2 v nhu cu oxy sinh ho (BOD) thc hin nh gi. Loi sinh vt tn ti thay i trong t nhin t vng ny sang vng khc. Bng 4: Phn loi cht lng nc mt theo mt s thng s c trng Phn loi cht lng I Mc ca ch s Saprobic Khng nhim bn n nhim bn nh Thnh phn ca mi trng sinh hc mt s loi vi khun; qun x tha tht ca to si, to , ru; trng tm, c; ch yu BOD5 mg/l 1 NH4+-N mg/l vt O2 mg/l 8


35

II

vo ma xun nhim bn hu c nh; rt nhiu loi v dy c to, chai, c, cua v u trng; phong ph thc vt nc; c nc III nhim nng tp trung ng c cc vi khun hnh que, mt s loi to v thc vt bc cao, nhiu a, bt, b nc; t c IV Cc k nhim ch c vi khun, nm, ng vt nguyn sinh; khng c sinh vt bc cao Nhng am hiu v cht lng nc c th cho thy s Nhim bn va

2-6

0,3

6

7-13

0,5

2

15

mt vi mg/l

2

thay i bt thng v cht

lng, tuy nhin phi tnh n trng thi tn ti ca nc ng (tnh) rt nhy cm i vi s thay i cht nhim hn l nc chy lin tc. Do vy, s ph dng thng xut hin ti cc h v p cha. Ti nhng khu vc ny, nng PO43- ng vai tr quyt nh, tuy nhin PO43- ch l mt nhn t nh dn ti s pht trin mnh ca to thm tr khi nng ca n rt nh. Ngun sn sinh ra PO43- bao gm nc thi sinh hot hoc xi mn b mt ti nhng ni s dng nhiu phn bn. Cng nh vy, hm lng N tng dn ti tng s lng to v dn ti suy gim cht lng nc.

Cu hi: 1. Cc thng s BOD v COD c p dng trong cc trng hp no? 2. Hy gii thch l do ti sao cc thng s BOD5, NH4+-N v O2 li c chn l cc thng s chnh, c trng cho cht lng nc mt? Tr li:


36

1. BOD p dng cho quan trc di hn i vi nc t nhin COD p dng cho trng hp phn tch nhanh cc mu nhim nng, v d: dng thi cng nghip.

2. Cc thng s trn th hin cho mc dinh dng v s thoi ho cng nh kh nng t lm sch ca nc mt. S xut hin cc sinh vt gy bnh trong nc mt cn c lu tm i vi nhng ni nc mt c s dng cho mc ch sinh hot. Cc ch tiu sinh hc cn c xc nh l: Tng s vi khun Coliform Vi khun Faecal Coliform Faecal Streptococci Salmonella Cc vi rt ng rut

Cc vi sinh vt gy bnh c th i vo nc mt qua cc cng nc thi sinh hot hoc nc thi t cc bnh vin, l m... Ti nhit 37oC, nc cung cp cc iu kin khng thun li v cc sinh vt kh pht trin hn na. Tuy nhin, tnh ly nhim c th vn c duy tr bi cc dng cn sng st. Trong cc nh my x l bn thi sinh hc thng thng, cc sinh vt gy bnh c th khng bao gi b loi b bi vy nc thi lun gy ra nhng nh hng bt li i vi nc mt. Cc thng s kim tra tnh cht l ho hc i vi nc mt thng rt nhiu. Chng xut pht t cc yu cu v lut nh hoc cc mc tiu nghin cu khoa hc - k thut. Hn 1000 thng s c nghin cu i vi nc mt, v khong 100 trong s thng xuyn c xem xt. Tuy nhin, nghin cu mang tnh cht thm d thng khng pht huy c tc dng ti nhng ni c cc thng tin v loi v dng nhim. Nhiu thng s c lit k lin quan n cc quan trc nc ngm cng c thc hin i vi nc mt. Thm vo , theo mc ch quan tm c bit i vi nc mt: hnh nh, su, hm lung O2 (O2 bo ho v tn tht), cc cht nhim bn hu c (BOD, COD), cc thng s sinh hc, cc lp vt cht c bit nh cht hot ng b mt, du m, ho cht bo v thc vt. Cc yu cu ti thiu i vi vic quan trc nc mt, cc thng s c th s dng o c l:


37

Nhit Nhu cu oxi ho hc COD Nhu cu oxi sinh ho BOD Hm lng Cu

pH P tng s Fe tng s Hm lng Cr

Thnh phn oxi Thnh phn NH4 Zn tng s Hm lng Ni

I.1.3. Nc thi Nc thi l nc qua s dng t cc hot ng sng ca con ngi c thnh phn v tnh cht thay i. Nc thi c th gy nhim nc ngm v nc mt. S nhim bn ch yu gy ra bi cc h thng cng thi ca cc thnh ph, th trn, cc khu cng nghip, v khu vc sn xut nng nghip. Cc nguy c gy nn bi nc thi lm gim thnh phn oxy trong nc thng qua s ho tan cc cht dinh dng (v d: cc thnh phn hu c, NH4, sunft. Ngoi ra nh hng ca vic s dng phn bn (ph dng) c th dn ti s tn ti cc cht dinh dng nh Nit v Photpho. c tnh c bit ca nc thi cng nghip l cc thnh phn ca n c th gy cn tr cc qu trnh t lm sch. Cc thnh phn c th c phn nhm theo nhng nh hng bt li nh di y: Cc vt cht gy c c th gy ra c tnh mn tnh hoc tc th i vi cc sinh vt nc. Cc vt cht gy cn tr c th gy ra cc mi kh chu, v, mu, vn c cng nh gy ra cc vn v k thut trong khi vn hnh, phn b v s dng. Cc vt cht c th phn hu c th gy ra gim thnh phn oxy Cc cht dinh dng gy ra ph dng, cn tr dng nc...

Cc r ro do nc thi cng nghip c th gy ra cc nh hng bt li i vi cc ngun nc c bit l cc ngun nc cp cho sinh hot, cho ngnh thu sn, nng nghip v chn nui. Trc khi i vo cc ngun tip nhn, nc thi phi c x l gim thiu cc ri ro c th xy ra. i vi vn ny, nghin cu kim sot nc thi ng vai tr ht sc quan trng. Khng phi tt c cc ngun nc u c chung mt mc ch s dng, do i vi mi ngun tip nhn s c cc yu cu v tnh cht v tiu chun ring bit. Nh vy tiu chun cht lng nc c th c xc inh tu thuc vo nhm mc ch s dng.


38

Phn loi mc nhim nc thi ch c th p dng trong trng hp nc thi sinh hot. Bng 5 ch ra cc thng s c chn i vi cc mc nhim bn: nng, va v yu. Bng 5: Nng trung bnh ca cc thng s o c trong nc thi sinh hot vi cc mc nhim bn khc S nhim bn Nng (mg/l) Va (mg/l) Nh (mg/l) Tng cht rn 1000 500 200 Vt cht c th lng (mg/l) 12 5 4 Nhu cu oxi sinh ho (BOD) 300 200 100 Nhu cu oxi ho hc (COD) 800 600 400 N Tng s 85 50 25 30 30 15 NH4-N Cl 175 100 15 kim 200 100 50 Du, cht bo 40 20 0 Thnh phn ca nc thi t cc nh my x l bn cn thng ngn cn cc qu trnh sinh hc. Khong nng ca mt s cht c c lit k di y: Bng 6: Khong nng ca cc vt cht gy c gy cn tr cc qu trnh sinh hc trong cc nh my x l bn cn Cht gy c Khong nng (mg/l) Cu 13 Cr-III 10 20 Cr-IV 1 10 Cd 3 10 Zn 3 20 Ni 2 10 Co 2 15 CN 0,3 2 5 30 H 2S Nh cp n trn, nghin cu v nc thi c th rt khc nhau. Nhng nghin cu nn c xem xt l: Bng 7. La chn cc thng s trong quan trc nc thi Thng s Mu, mi pH dn in (EC) Phn tch theo thi Phn tch xc Cc phn tch nng im nh mc tiu th cao oxy X X X X X X X Thng s


39

COD BOD Tng ccbon hu c (TOC) Ccbon hu c ho tan (DOC) Nit tng s NH4+, NO2-, NO3Phtpho tng s FSO42Sunfit Cl H2CO3 Na, K Ca, Mg Fe, Mn As, Pb, Cu, Ag, Zn, Cr, Cd, Hg, Ni Kh nng phn hu c tnh vi c c tnh vi vi sinh vt Phenol tng s, phenol bay hi, lin kt ca cht hu c vi Cl, CN HCBVTV

X X

X X

X X X X

X X X

X X X X

X X X X X X

X X X X X X X X X X X X X X X X

X

I.2. CC VN LIN QUAN TI QUAN TRC MI TRNG T t l mi trng h tr cho s sinh trng v pht trin ca thc vt v h sinh thi. Vi mc ch nh vy, tnh bn vng ca t ch yu ph thuc vo khng gian i vi s pht trin ca b r thc vt v kh nng trao i ca n vi nc, khng kh, nhit v cc cht dinh dng. Nhng yu t ny th hin ph nhiu ca t. Khng gian pht trin ca r thng c xc nh bng s vn su (solum) ca r. Tuy nhin, i vi cc loi t, c tnh xp v lin kt khng cht s thc y kh nng m su ca r. Mt r ph thuc ln vi mt s tnh cht t nh s thay i v dung trng, thnh phn rng, mc nc ngm v s phn b ca cc thnh phn nh mui, pH, th kh. bn ca r i vi kh nng m xuyn c xc nh nh sau:


40

su S m xuyn ca r t hn 10 cm rt hp 10-25 cm hp 25-50 cm Trung bnh 50-100 cm Su Ln hn 100 cm Rt su Cc nghin cu v t c th theo mt s hng sau: Xc nh kh nng trao i dinh dng Xc nh cc vt cht c kh nng gy nh hng nguy hi ti nc ngm Xc nh cc tnh cht n mn i vi ng ng Xc nh s mn ho Kim tra hiu qu lc Xc nh cht lng t Xc nh mc nhim bn mi trng t

Hm lng cc cht dinh dng c th trao i t t l yu t quan trng quyt nh kh nng cung cp dinh dng cho cy trng v do vy vic xc nh chng phi s dng phng php thng nht. T c th tnh ton nhu cu cung cp thm cht dinh dng cho cy (bn phn). Kh nng trao i cc cht inh dng c tng kt trong bng 8. Bng 8. Dng cht dinh dng lin kt trong t Xc nh bng Cc cht dinh dng ho tan trong nc D dng Cc cht dinh dng trao i (bao gm phn ho tan trong nc) Khng linh ng, d b linh Kh Cc cht dinh dng trao ng i (bao gm phn ho tan trong nc) Khng linh ng, kh b Rt kh Phn b d li ca cc cht linh ng dinh dng Tuy nhin, t l trao i ca cc cht dinh dng c bn ph thuc vo thnh phn st, hu c, m t, pH, v th kh. Hm lng cc cht b linh ng trong mi trng thc cht ph thuc vo cc iu kin kh hu v tng t. nh gi s nhim bn cc cht v c (kim loi nng) trong t l rt kh khn do nng vn c ca kim loi nng c th ph thuc rt ln vo trng thi khong vt hc Dng lin kt B ho tan nhng khng lin kt trong t Mt phn lin kt vi cc cht trao i Kh nng trao i Rt d


41

(thnh phn m). S dng cc cht dinh dng (bn phn) cng l nguyn nhn dn n nhim bn t. nh gi s nhim bn c th c xem xt t quan im v li nhun hoc hiu qu ca t khi xem n nh l mt lp lc nc t nhin. i vi vn ny cn quan tm cc im sau: Vai tr quan trng ca t nh l vt mang i vi cy trng Kh nng lc ca t i vi vic bo v nc ngm.

Vic chn la cc th nghim i vi vic nghin cu kh nng linh ng ca kim loi nng ang tn ti mt s vn . gii quyt vn ny, cc kt qu o c tnh d tan ca kim loi nng i vi thc vt bng phng php chit cho php s dng so snh vi lng kim loi nng c ht bi r thc vt. S dng axt mnh hoc cc cht to phc mnh chit kim loi nng trong t khng cho kt qu n nh. S dng NH4OH cho kt qu tng i n nh i vi vic xc nh cc dng linh ng ca cc nguyn t vt. Ngy ny, c rt nhiu phng php chit c s dng trong cc nghin cu lin quan n kim loi nng c cng b bi nhiu tc gi. Phng php chit thng dng nht thng c thc hin theo quy trnh chit lin tc c cng b bi Tissier 1979). Kh nng chit hu ht cc kim loi nng t t ln hn hu ht cc nguyn t thng thng (photpho: 1%, Al: 2% n 3%, Na: 0,1 n 0,5%). Tuy nhin, kim loi nng cng c bit n lin kt mnh vi cc vt cht humus hn cc nguyn t c cp trn. Gii hn chng chu ca kim loi nng trong t l rt quan trng. Bng 9 cung cp ngng c tng ng vi nng ca chng trong cy trng. Gii hn ny thay i tu thuc vo loi thc vt. Bng 9. Khong gy c ca mt s kim loi nng trong t Nguyn t Cu Zn Cd Ni Pb Cr Hg Ngng (mg/kg) 200-400 500-5000 10-175 200-2000 500-1500 500-1500 10-1000


42

Hnh 7. V d minh ho vng tun hon thu ngn vcc dng tn ti ca n trong mi trng Nhim bn t do cc cht hu c nh ho cht bo v thc vt cng phi c xem xt n. Trong qu trnh s dng ho cht bo v thc vt, mt phn c a vo hoc di xung trc tip xung t. Lng hp ph vo t thay i theo tuyn v c mi quan h khng ln. S tn ti ca HCBVTV trong t c m phng trong hnh 8.

Hnh 8. S phn ca HCBVTV trong t


43

Khi i vo t, cc vt cht ny thay i c tnh sinh hc l thuc vo mt s tnh cht t, chng b chuyn ho thm tr b khong ho hon ton. Cc lp t b mt c cha cc cht hu c s hp ph HCBVTV. S thm su ca chng ph thuc vo thnh phn khong st, thnh phn Nit, oxt Fe, Al v cc l hng trong t. Nghin cu v cc tnh cht n mn ca t cng nh vic xc nh s mn ho c bit quan trong ti cc khu vc kh hn. Bng 10. Cc ch tiu cn quan trc i vi cc nghin cu c th Thnh phn dinh dng Thnh phn cp ht Thnh phn nc pH Th kh dn in Tnh chua/ kim Hu c ccbon Na K Ca Mg Mn Cu Zn Cr, Ni, Cd, Hg Br Mo N tng s, N hu c NH4 NO3Pht pho tng s ClSO4 Cacbont, Hydro cacbonat S HCBVTV mn X X X X X X X X X X X X X X X X X X X nh gi cc vt cht gy c nh gi tnh cht n mn ng ng X X X X X X X X X X X X X S mn ho

X X X

X X X X X X X X

X X X X

X X X

X

I.3. CC CHT C HI GY NHIM MI TRNG KHNG KH


44

Ngun gc cc cht c hi, gy nhim mi trng khng kh l do sn xut cng nghip, nng nghip v do qu trnh t nhin liu. Cc cht c hi i vo c th ngi qua ng h hp, tiu ho v qua da. Cht c hi trong khng kh i vo c th ngi qua ng h hp l nguy him nht v thng gp nht. N xm nhp qua ph qun v cc t bo i vo mu. Cht c hi thm qua da (ch yu l cc cht c th ho tan trong m v trong nc) vo mu nh benzen, ru etylic. Da vo tc dng ch yu ca cht c hi c th chia ra cc nhm sau: Nhm 1: Cht gy bng, kch thch da, nim mc v d nh axt c, kim c v long (vi ti, amoniac). Nhm 2: Cht kch thch ng h hp trn nh: Clo, NH3, SO3, SO2, NO, HCl, hi fluo Nhm 3: Cht gy ngt Gy ngt n thun nh CO2, etan, metan Gy ngt ho hc: CO ha hp vi cc cht khc lm mt kh nng vn chuyn oxy ca hng cu lm ri lon h hp. Nhm 4: Cht c tc dng thn kinh trung ng, gy m, gy t nh cc loi ru, cc hp cht hydro cacbua, H2S, CS2, xng Nhm 5: Cht gy c Cht gy c tn thng c th: cc loi hydro cacbua, halogen, clorua metin, bromua metin Cht gy c tn thng cho h thng to mu nh benzen, phenol, ch, asen Cc kim loi v kim c nh: ch, thu ngn, mangan, photpho, fluo, cadimi, hp cht asen c tnh ca cc cht nhim trong khng kh c th tham kho trong rt nhiu ti liu lin quan. II. T CHC THC HIN V PHNG PHP LY MU Sinh vin cn nm c mt s kin thc sau: C s trong vic la chn im ly mu i din Cc nguyn tc ly mu t, bn cn, nc v mu khng kh


45

C th xc nh c s lng mu ph hp cho cc khu vc ly mu v hiu c cc hn ch trong vic quyt nh s mu cn ly

II.1. Gii thiu chung V c bn s lng mu c ly cng ln v nhiu thng s mi trng s cng phn nh ng trng thi ca mi trng ti khu vc nh gi (quan trc), tuy nhin trong thc t rt kh thc hin do gnh nng v kinh t, thi gian v iu kin phn tch. Do vy, vic quyt nh thng s nh gi v s lng mu nh gi ng vai tr ht sc quan trng trong vic phn nh trng thi tnh trng ca mi trng. Nh chng ta bit trng thi tn ti ca cc cht trong mi trng c ba trng thi rn, lng v kh. V vy vic ly mu nn tp trung vo cc i tng c th trong qu trnh nh gi v d nh nc h, sng, khng kh. Bn cht ca cc thnh phn trong t nhin lun tn ti ti mt gi tr nng nht nh iu ny tu thuc vo cc vt cht vn c trong mi trng. Do , trc khi quyt nh cc v tr ly mu ngi ly mu phi xc nh r c mc tiu t s gip ch cho vic chn la cc thng s v v tr ly mu ph hp. nh gi cht lng mi trng c th chia ra lm hai dng chnh sau: nh gi cc thnh phn vn c trong t nhin (cha b tc ng bi cc hot ng sng ca con ngi). y l cng vic kh thc hin bi kh nng phn tch v k thut phn tch kh c th xc nh c hng chc nghn thng s mi trng. Vic nh gi ny s gip ch cho vic xc nh cc gi tr nn ca cc thng s mi trng v phn bit gii hn sch - nhim bn nhim. nh gi cc im tip nhn cht thi t cc hot ng sng ca con ngi. loi nh gi ny thng c chia nh theo cc mc ch nh gi. V d: nh gi cht lng nc thi cng nghip thi vo ngun nc cp sinh hot, nng nghip, thu sn, vui chi gii tr So snh vi loi nh gi trn y l cng vic d thc hin hn. Tuy nhin im quan trng trong loi nh gi ny l xc nh c ng c trng v tnh cht ngun thi t mi c th chn la c v tr ly mu v thng s nh gi ph hp nht. Cc kin thc v ngun im v ngun din cng ht sc cn thit. C hai cch ly mu chnh l: Ly mu ngu nhin46


Ly mu theo mc ch nghin cu.

Bt c mt th tc ly mu no bao gm vic la chn im ly mu; kch thc v kiu dng ca khu vc ly mu v s ln ly mu cho mi mu. lm c iu ny, cc thng tin lin quan n s phn b ca cc cht nhim bn ti khu vc nghin cu l rt cn thit. Nhim bn do cc cht v c hoc hu c c th c ly ngu nhin, quy c, di rc, phn tng hoc theo hng dc. Ngoi ra cc thng tin v a hnh, h thng thu vn, cng rt cn thit. Hnh 3 m t mt s k thut ly mu. Trc khi bt u ly mu, ngi ly mu cn phi t t ra mt s cu hi sau: 1. Cn thit phi xin kin ca ch s hu? 2. Vic ly mu c cn phi s dng cc thit b c bit hay khng v iu kin hin c? 3. S mu v s ln lp li l bao nhiu? 4. Yu cu ca mu cn phn tch nh tnh hay nh lng? 5. Ho cht v dng c yu cu l g? 6. Phng php phn tch v thit b phn tch cn l g? 7. Th tch mu yu cu i vi k thut phn tch l bao nhiu? 8. C cn phi p dng cc quy nh chun i vi khu vc ly mu khng? 9. Loi bnh cha mu v yu cu bo qun ca cc thng s phn tch l g, c iu kin thc hin khng? 10. Bnh cha c yu cu cn phi x l trc khi ly mu hay khng v cc x l? 11. Thit b dng bo qun mu l g?


47

Hnh : Gii thiu mt s phng php ly mu II.2. Cng tc chun b cho ly mu 1. Trc khi tin hnh, yu cu ngi ly mu phi quyt nh phng php phn tch. K thut phn tch c s dng nh hng ti kch thc mu cn ly, loi bnh cha mu v phng php bo qun mu. Phi xc nh trc c thi gian hon thnh cng vic ly mu v phn tch ti phng th nghim. Thi gian bo qun mu ti phng khng nn qu lu nhm trnh s thay i tnh cht ca mu nghin cu. Thi gian bo qun ti a tng ng vi tng nguyn t c trnh by trong bng di y. 2. Quyt nh chng trnh ly mu. Tu thuc vo mc ch nghin cu, chng trnh ly mu c th thc hin theo cc chu k theo th t u tin sau: Theo ma: Quan trc nng ca cht nhim nh hng ti cc qu trnh t nhin. Theo tun: Cht nhim c th pht tn tu thuc vo thi gian lm vic ca nh my.


48

Theo ngy: Quan trc nng ca mt s cht c th b thay i do cc qu trnh sinh hc cn tiu th nng lng mt tri.

Chng ta cng c th tin hnh quan trc cc dao ng bt thng, tuy nhin kt qu o thng c s bin ng nng cht nhim ln do s ph thuc vo chng trnh quan trc, s mu ly v thi gian quan trc. 3. Quyt nh tng s mu cn ly, lu phi ly mu nhc li cho mi v tr ly mu. Yu cu s mu phi p ng v mt thng k x l thng kt c ngha. Cng nn cn nhc v thi gian cn hon tt mu phn tch. 4. Quyt nh v tr ly mu v thit b ly mu. V tr ly mu phi c s cho php ca ch s hu. Cn ch , in kin thi tit lun bin ng. V tr ly mu phi l v tr din cho khu vc. Ly mu nc mt yu cu phi ng u trong thit b ly mu. 5. Quyt nh th tch mu cn ly v dng c bo qun mu. Dng c bo qun mu c th l bnh thy tinh hoc bnh polyethylen. Tuy nhin vic la chn bnh cha mu ph thuc vo tnh cht ca mu nghin cu. Bnh polyethylen khng dng cha cc mu xc nh cht hu c, bnh thu tinh khng dng cha cc mu phn tch cc dng cht v c nh Na, Si... Vic ly y mu cng ht sc quan trng c bit i vi cc trng hp cn phn tch cc vt cht bay hi hoc kh ho tan. i vi cc trng hp khc khng nht thit phi ly y, iu ny gip d dng trn u mu trc khi phn tch. 6. Quyt nh phng php bo qun mu. Phng php bo qun chun c th p dng cho hp ht cc cht trnh s mt mu ti a l bo qun lnh 4oC. i vi mt s cht yu cu c iu kin bo qun ring bit: Cu hi: Nitrat - bo qun 4oC hn ch s phn hu t t bi vi sinh vt Ho cht bo v thc vt - bo qun trong bnh ti trnh cc phn ng quan ho. Ion kim loi - bo qun trong iu kin axt hn ch s hp ph ion kim loi ln thnh bnh. Phenol thm vo NaOH hn ch s bay hi. BOD - bo qun lnh ti 4oC, yu cu phn tch cng sm cng tt.


49

Trong phn tch hm lng vt ca mt s dung mi trong nc sng chy qua khu vc b nhim nng. Mu c chuyn ti phng th nghim v phn tch bng my sc k kh. Trong cc bc phn tch bc no cn c kim sot trnh s nhim bn mu? Ti sao quy trnh kim sot cht lng li dn ti kt qu phn tch m bo tin cy? Tr li: Ti khu vc nhim nng, kh nng gy nhim bn mu hon ton c th xy ra. c bit trong trng hp s dng cc dng c ly mu khng c lm sch. S dng bnh cha ng quy cch s hn ch s nhim bn hoc mt mu trong qu trnh vn chuyn v bo qun.. Ti phng th nghim, s nhim bn c th do mt s dung mi trong khng kh. sch v n nh ca thit b phn tch c th gy sai s php o. Mu trng nn c phn tch cng vi mu o khi pht hin thy du hiu mu b nhim bn ti bc ly mu, vn chuyn v bo qun mu. II.3. Cc phng php ly mu v s mu cn ly V tr ly mu c th c xc nh mt cc ngu nhin, theo h thng hoc ngu nhin phn lp (hnh ). Ly mu ngu nhin: S dng giy bng knh k vung v t chng ln bn khu vc nguyn cu. La chn mu hon ton ngu nhin bng cch nh s ln cc sau bc thm. Cch ly mu ny b quan hon ton s bin ng ca cht nhim bn ti khu vc nghin cu. Cc im khng c ly mu nn c ghi li. Kiu ly mu ny thng c p dng i vi cc khu vc c cc cht nhim ng nht trn mi v tr.

Hnh : Gii thiu mt s phng php ly mu ngu nhin


50

Ly mu h thng: Xc nh im ly mu u tin hon ton ngu nhin, cc mu tip theo c ly theo hng v khong cch c nh. V d mu c ly theo cng hng bc v khong cc 5 m. Cch ly mu ny c kh nng cung cp kt qu chnh xc cao hn i vi cch ly mu ngu nhin. Tuy nhin, nu t c s bin ng theo chu k vic lm ny c th dn ti cc mu b cng xu hng. Ngi ly mu nn ch ti mt v khong cch gia cc mu. Ly mu ngu nhin phn lp: c s dng trong trng hp a im ly mu c bit trc v s phn b ca cc cht nhim bn. Phng php ly mu ny thng c s dng nht. Phng php ly mu thc hin bng cch chia nh theo cc khu vc ng nht. Do vy chnh xc ca kt qu s cao hn. Ti cc khu vc chia nh, mu c ly ngu nhin S mu cn ly Trong trng hp khu vc ly mu l ng nht, v c bn s lng mu ly cng ln chnh xc ca kt qu cng cao. Trong thc t phn tch, tnh kinh t lun khng ch s lng mu v cc thng s nh gi. Trong trng hp ny cu hi a ra l liu bao nhiu mu cn ly m bo sai s c th chp nhn. xc nh c s mu cn ly c th p dng bng cch Trc tin phi quyt nh mc sai s, E c th c tnh nh sau:

E = t (V ) 0.5V = S2 /n Trong : t: l gi tr kim tra V: l giao ng S2: tng bnh phng n: s mu Tng bnh phng c tnh bng phng trnh sau:

S =

( xi x) 2 (n 1)

S mu c ly sau c tnh bng cng thc:

n = t 2S 2 / E 2V d:


51

Chng ta c tp hp 10 mu c ly ngu nhin ti mt khu vc. Gi tr o ca Pb c trnh by trong bng di y. S dng cc phng trnh cung cp trn tnh ton mc sai s. Mu 1 2 3 4 5 6 7 8 9 10 Pb (xi) ppm 91 95 104 82 95 103 97 89 85 89 X (trung bnh) 93 93 93 93 93 93 93 93 93 93 (xi-x) -2 2 11 -11 2 10 4 -4 -4 -4 2 (xi-x) 4 4 121 121 4 100 16 16 16 16 Nu mc chnh xc thu c bng trn khng th chp nhn v ch cho php sai s ti a l 2 ppm vy bao nhiu mu cn c ly?

II.3.1. Ly mu ncNu cho rng nc xut hin trng thi ng nht th khng thc t. Nc khng ng nht c v khng gian v thi gian rt kh c th thu c mu i din. S phn tng trong h v sng thng theo dng chy thnh phn ho hc v nhit . S giao ng theo thi gian c th xut hin v d: do hin tng kt ta hoc thay i theo ma. Nh chng ta bit kt qu phn tch ph thuc vo cc mu c ly t khu vc nghin cu. Do , mt im c bit cn ch l phi t chc c cc nhm mu v k thut ly mu. Mc ch thu thp c cc mu i din nht cho ton b khu vc. iu ny c ngha cc mu phi c thu thp v bo qun ng cch tng ng vi tng thng s (ch tiu) d nh quan trc i vi cc mu nh nc mt, nc ngm, nc thi. Mt khc a im v thi gian ly mu phi c la chn tng ng vi phng php phn tch, cc kt qu phn tch s phn nh s thay i tm thi hoc cc b trong cc qu trnh nghin cu trc . Thu thp qa nhiu mu l nhng sai st c hu thng xy ra trong cc nghin cu dn ti gnh nng v kinh ph. Thu thp t dn ti kt qu thiu tnh i din. Thm vo cc thng tin chuyn ti trong cc kt qu ca mu ngu nghin cu ph thuc vo s bin ng ca cc thng s c o c c th. tng kt cc kt qu, kch thc sai s ca mt mu ngu nhin phi c bit n. Sai s mu ngu nhin m t s khc bit gia gi tr mu ngu nhin (trung bnh s hc) v gi tr thc ca ton b tp hp mu (s lng mu). Kch thc sai s mu ngu nhin ph thuc tp hp mu. Trn cc s liu c th, khng th chng minh sai s ngu nhin tr thnh nh khi tng s lng mu. Cc mc tiu cn t c khi ly mu l:


52

Kim sot cht lng Tin hnh d bo Xc nh cc ri ro

Thu thp cc mu ti cc khu vc nhy cm cho mc ch kim sot cht lng thng kt hp vi c quan qun l. D bo t cc s liu thu thp c nhm gii quyt cc vn s xy ra trong tng lai hoc nhn nh cc xu hng gy nhim bn, v d, trc khi xy dng mt nh my x l bn thi, khi d bo yu cu phi xc inh c cc nh hng trong tng lai do nc thi i vi nc mt. Cc mu i din ca nc v nc thi c th thu thp bng mt s cch. Phng php la chn cch ly mu c th lm theo mt s bc sau: La chn mt phng php ly mu trn c s cn nhc mt s thng tin sau: Nng dao ng Nh Ln S thay i dng chy ln S thay i dng chy nh Ly mu ngu nhin Ly mu ngu nhin Mu c chia theo t l ln Mu c chia theo t l th ly tch Cng tng t trong cc trng hp ly mu t, yu cu phi ly i din. Cc mu

ngu nhin v mu trung bnh c th ly ti cc khu vc c din tch ln. C th s c tho lun trong phn sau.

II.3.1.1. T chc mng li ly mu ncTrong nhiu trng hp ni m a im ly mu thiu cc ti liu quan trc c th phi xy dng mi mng lng quan trc dnh cho cc nghin cu v nc, nc thi hoc t (v d: thnh lp mi c quan qun l nhim). Cc k hoch v phng php kim tra ban u i vi mc ch ny nn tin hnh mt cch k lng, chi tit mng li quan trc c th s dng trong mt thi gian di, cc kinh nghim cho thy s thay i v sau i vi mt h thng quan trc s dn n rt nhiu kh khn trong vic so snh cc d liu phn tch. Mc tiu c bit phi c ch ti i vi mng li quan trc l cc mu thu thp phi i din cho tt c cc im trong cng mt khu vc quan trc. H thng hon chnh i vi cc quan trc din rng nh h thng knh mng ca cc thnh ph ln thng bao gm nhiu h thng quan trc ph n l khc nhau v cht lng, phi phn bit r rng gia h thng quan trc ph v c th ca chng bng cc nghin cu tch bit. Trc tin phi s dng cc k thut, phng tin i vi cc nghin cu ban u l:


53

Nghin cu v a hnh v c th ho bng bn (cc bn b mt, cc bn a cht) Cc hnh nh khng gian (xc nh to ) H thng nc

Cc dng bn ny c chng ghp xc nh cc im quan trc i vi tng khu vc c th. Cc thng tin khc cng cn thu thp nh v tr s c thc hin ly mu trn hin trng. iu ny rt quan trng cho vic nh gi cc mu i din ca cc khu vc c la chn ly mu. Nn cn nhc im ly mu xc nh nh hng ca cc ngun thi. V tr ca im ly mu phi bao gm v tr trc khi c dng thi v v tr sau khi c ca dng thi

II.3.1.2. Yu cu thc hin i vi vic thu thp cc mu nc.T chc mng li o c h thng nc v cc ngun thi cn phi c cn nhc k lng. lm c iu ny nn m t h thng theo cc t l nh dn. i vi mng li quan trc nc ngm, cc thng tin lin quan v a cht thu vn s tr gip cho vic xc nh mng li quan trc. Hnh 1 di y l mt v d minh ho v la chn cc a im quan trc i vi mt h thng sng.

4 2 1

3 5

Hnh 1. V d minh ho v la chn im quan trc i vi mt h thng sngTrong c khu vc c th c chia nh thnh nhiu vng, v d c chia lm 5 vng, tng ng vi mi vng s c cc im o c c nh r ph thuc vo nhng yu cu c th, v s khc nhau v c im ca mi khu vc. Nhn trn din rng, h thng


54

dng chy bao gm cc dng chy nh nm ri rc an xen vo l cc im gy nhim v ca x nc thi. Cc a im t b nhim bn thng nm pha trn (thng ngun ca sng), tuy nhin ti a im ny cn xc nh cc tnh cht ca nc t nhin. Mt im khc cng cn phi ch ti l vic xc nh cc im o c ti hai bn b ca h thng sng theo a gii hnh chnh nhm gii quyt cc tranh ci v vn nhim. i vi cc a im gn cc khu cng nghip, nht thit phi c nhiu im o c, thng thng mt im/100 200 Km2. Hnh 2 l mt phn ca ton b h thng sng c trnh by bng s . Cc im o c ti ni din ra s thay i mnh v cht lng nc c khoanh trn. Cc khu vc dn c nh du bng ng gch cho v ca thi nc (nc thi sinh hot, cng nghip...) c nh du bng mi tn.


55

Vng trng Khu vc ly mu Dng thi

Hnh 2. M phng mt phn ca h thng sngCng cn b xung thm cc im o c bit tng ng vi cc ngun im c xc nh trc. Hnh 3 m t mng li quan trc i vi mt nh my x l nc thi trong mt th trn (thnh ph). Bao gm cng thot nc, ni thu gom nc, ni thu gom nc chnh, hng nc, khng gian chy trn, cng chy trn cng nh nh my x l nc cng vi u ra ca dng chy. Vng gch cho th hin khu vc khu cng nghip. Cc im o c trong h thng cng nn b tr ti a im s thi ca cc nh my nm trong mng li, ti cc hng nc chnh v ti cc im pht tn nc thi ca cc nh my, nhng ni nghi ng nc thi c cha cc vt cht nguy hi.


56

1 1 3 1 2 3 2

4 2 1 1 3

5

6

Hnh 3. Mng li quan trc cht lng nc i vi mt th trn Ghi ch: 1. Cng thi2. im thu gom nc 3. im thu gom nc chnh 4. Ngp nc do ma 5. X l nc thi 6. Ni tip nhn im ly mu trn din rng hoc cc knh mng nn t ti cc v tr m dng nc thi c pha trn hon ton. Trnh trng hp hai mu ly cng mt v tr, phi ly theo hng chy ca dng nc. Hnh 4 m phng qu trnh pha trn nc t cc nhnh ph hoc cc ngun vo ca nc thi, qu trnh ny din ra rt chm trong trng hp dng nc trng thi n nh khng c s xo trn mnh m.


57

Dng thi

Dng chy ca sng

1

2

3

4

5

Hnh 4. M phng qu trnh pha trnTrong cc trng hp nh vy, im ly mu c nh nn chuyn ti v tr trc im s 5. Qu trnh ho trn cht thi hon ton ph thuc vo lu tc ca dng sng. Trong qu trnh di chuyn xung h lu, nng cc cht nhim gim rt nhanh do lng nc trong lu vc chy vo sng tng. Nhiu ho cht phn ng v tiu tan do hp th hoc phn r sinh hc. Nng cc cht gy nhim sau khi trn nc thi vi nc sng c th tnh theo cng thc:

C= Trong :

C1.Q1 + C2 .Q2 Q1 + Q2

C: Nng cht nhim trong dng sng ti im pha trn Q1: Lu lng dng chy ca sng C1: Nng cht gy nhim c trong dng Q1


58

Q2: Lu lng nc thi x vo sng C2: Nng cht nhim c trong dng thi Q2

Vn i vi h thng nc (h, h cha) c hnh dng khng ng nht, trc tin cn xem xt tnh khng ng nht i vi cht lng nc theo phng nm ngang. Do vy cn thit phi b tr mt vi im ly mu tu thuc vo iu kin c th, c th gim bt s lng mu ly trong cc ngy k tip. S xo trn mnh m din ra ti im ly mu thng xy ra theo phng thng ng bi vy vic ly mu nn thc hin ti cc su khc nhau, v d: ly mu gn b mt, ly mu ti cc lp xut hin s chnh lch nhit , ly mu gn y (nguyn nhn nh hng do bn cn). la chn cc mu i din trn mt mng li quan trc. Yu cu i vi phng php ly mu phi n nh c th theo thi gian, iu ny c xem nh l mt yu t quan trng nh hng ti kt qu phn tch. Ni nng cc cht cn quan trc trong dng chy ln phi c c bit quan tm, phi tng tun sut ly mu. Trong nc v nc thi c hm lng cc cht nhim bin ng nh, vic ly mu ch cn thc hin mt thng mt ln hoc thm tr ti vi thng. nhng ni bit trc c chu k bin ng theo ngy, thng hoc nm, c th tm ngng vic ly mu trnh s o c b lp i lp li ca cc khong gi tr cao hoc thp. S dng cc phng php ngu nhin chn la im o c, v d: rt thm s gip cho vic nng cao tnh hu ch ca s ln ly mu ngu nhin. Sau mt qu trnh nh gi lu di, cc thng s thng k ht sc quan trong cn phi tnh n l: gi tr trung bnh, s bin ng, ga tr ln nht v cc gi tr ny nn c biu din di dng th. Vic nh gi c th quyt nh gim tn xut ly mu m vn khng mt i cc thng tin quan trng ca cc mu quan trc.


59

C A X

t C B X

t

Hnh 5. nh hng ca s bin ng nng i vi cc gi tr d bo t cc mu ngu nghin (A- Ngu nhin; B- chu k) II.3.1.3. Xc nh dng chyCc nghin cu thc nghim cho thy rng vic xc nh dng chy v cht lng ca nc v nc thi c mi lin h ht sc phc tp. V vy ny sinh cc vn i vi cc h thng o c t ng v cc thit b quan trc c s dng. Khi ly mu nc ngm v nc ung vic o c dng chy c th thc hin d dng. i vi cc h thng m nh knh, mng, sui vic o c cn phi c s h tr ca bin php k thut v s dng ton hc tnh ton. xc nh chnh xc thng s dng phng trnh tnh ton dng chy ca Bernoullis. Di y s trnh by chi tit v cch tnh ton dng chy nh sau:

i vi h thng dn c tng xy

Phng php ca Manning-Strickler c th c dng i vi cc knh m. dc ca knh, tng bao quanh v chu vi knh dn l cc thng s phi c. Khi c ba gi tr trn vn tc dng c th c xc nh n gin bng cch o mc nc v c tnh ton theo cng thc sau:


60

v = k .R 2 / 3 . J 1 / 2 ( m / s ) Trong : v: vn tc (m/s) 90-135 85 65-75 R: bn knh ng ng (m) F: din tch (m2) U: Chu vi (m) k: (m1/3/s) J: dc (m/m) i vi cc ng xi mng mi i vi cc ng kim loi v xy bng gch i vi cc ng thng thng

Gi tr k chun c th tham kho di y:

R= Trng : R: chiu rng D: chiu su mc nc

R.D R + 2.D

Lu lng dng c tnh bng: Q = v.F (m 3 / s ) Cc knh m nh sng, sui

Vn tc dng chy c xc nh nh sau Dng phao th tri gia dng nc. o thi gian v khong cch.v= l t

(m/s)

l Q = F .c (m3/s) tTrong : Q: lu lng dng (m3/s) l: khong cch o c (m) t: thi gian o (m) F: din tch dng chy (m2)


61

c: h s

Din tch c th xc nh bng cch o c trc tip hoc bng cch o chiu su ti cc im khc nhau.II.3.1.4. Ly mu, bo qun v ct gi 1. Dng c ly mu

Ly mu v bo qun quyt nh cho tnh chnh xc ca th nghim. Dng c ly mu ph thuc vo loi mu cn ly s yu cu thit b ly mu n gin hay chuyn dng (bm, b ly mu t ng). Cc dng c khc cng cn phi c trong khi ly mu l: ti ni lng, ng, dy, n cn (dng trong cc trng hp cn kh trng trc khi ly mu vi sinh vt), hp nh n... La chn dng c cha mu ng vai tr quan trng. Trong nhiu trng hp, bnh nha polyethylen (PE) hoc bnh thy tinh thng c dng. S dng cc bnh cha lm bng cc vt liu khc yu cu phi c ghi ch c th. Cc mu c cha cc cht nhim bn hu c khng phn cc (du, HCBVTV) khng nn cha trong cc bnh nha, mc khc khng dng bnh cha bng bnh thy tinh cha cc mu nc yu cu xc nh Na, K, Br, Si nng thp. C hai dng bnh cha ny ph hp vi vic xc nh cc cht v c nng ln. Cc bnh cha trc khi s dng phi c ra sch v trng bng nc ct. c bit i vi vic bo quan mu trong thi gian di, cc cht rn c th bn trn thnh bnh v b hp ph mnh vic ra tin hnh bnh thng, sau ra vi axt Crm. Trong cc trng hp khc c th s dng axt HCl long ra. Vt b cc bnh c cc cht bn kh di chuyn bm trn thnh bnh nha khng th loi b hon ton. i vi cc bnh c cha cc vt cht nguy hi, phi a v ni quy nh. i vi cc bnh cha mu nghin cu v vi sinh vt, bnh cha phi l bnh thu tinh v c kh trng trc khi s dng bng ni hp mt vi ln nhit 180oC cng vi np y. C bnh phi c bo v bng l nhm. Tu thuc loi mu s yu cu cc bc bo qun tng ng. Cc phng php bo qun mu s c cp c th trong phn bo qun mu. Mt s bnh cha mu cho cc thng s c th. Bnh nha polypropylene v polyetylene Gi thnh r.


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Bnh Quartz hoc teflon - Loi ny tt nht nhng t nht. Bnh thu tinh Bnh thu tinh l loi thng dng. Trnh s dng bnh thu tinh mng ly mu c cha kim loi vi nng thp mg/l.

Dng c ly mu nc

Dng c ly mu thc vt ph du

Khi pht hin c bc trong mu, ct gi mu trong dng c ti mu nh h phch hoc bnh thu tinh mu nu. Ra bng axit s lm sch hon ton bnh trc khi s dng cha mu.Ra dng c bng axit.

Cc bc ra bng axit: a) Ra sch bnh thu tinh hoc nha bng cc cht ty ra. Cht ty ra c photphat t do l tt nht. (Khi xc nh photphat, phi xc nh lng photphat t do trong nc ty ra trc). b) Ra k bng nc sch. c) Ra bng dung dch axit clohidric 1:1 v dung dch axit nitric 1:1. (Axit nitric l tt nht cho ch v nhng kim loi khc). d) Ra sch bng nc ct. Vi mu cha crm, ra khong 12-15 ln l thch hp. Cn vi mu xc nh lng amni v nit tng s, nn s dng nc ra c amni t do. e) iu kin khng kh kh. Bo qun bnh thu tinh trnh khi cc ngun gy nhim. S dng axit crmic hoc crm t do trao i loi b cht lng hu c khi bnh cha thu tinh. Sau , ra k bng nc loi b tt c cc dng vt ca crm.


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Trnh s c mt ca cc kim loi gy nhiu trong bnh cha, nc ct hoc mng lc.2. Phng php ly mu nc

Ly mu nc c th bng cc thit b t ng hoc bng tay. Thit b ly mu t ng c dng trong cc trng hp ly mu ti cc thi gian c nh hoc ly t l vi tc dng sau c cha trong cc bnh rin r. Ly mu t ng thng c s dng i vi nc sng hoc ngun im. Ngoi ra, ly mu t ng cho php ly mu theo trung bnh thi gian hoc cc mu kt ta. Nguyn tc ly mu nc: s dng bnh sch sc bnh mt vi ln trc khi ly mu. Ghi li a im ly mu, thi gian, khong cch, tnh trng v cc bc tin hnh cho mi ln ly mu. Dc y m t mt s phng php ly mu nc.a- Ly mu nc ngm

Khi ly mu nc ging, phi ly mu nc vi nc gn ging.im quan trc

Trc khi ly mu vo bnh cha loi b phn nc lu tr trong ng ng bng my bm. Thi gian loi b phn nc lu cu trong ng ng ph thuc vo kh nng ca my bm. Nu nc c cha cc cht l lng dng ht nh ct, phi c lc qua giy lc trc khi tin hnh cc phn tch tch cht l ho hc. Mu phi c ly y,


su mc nc ngm su ly mu

Mc nc ngm

Mng lc

Mu

Hnh 6. M phng im ly mu nc ging khoan

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lng mu yu cu thng cho cc phn tch thng thng t 500 ml n 1000 ml, tu thuc vo nghin cu c th ly nhiu hn. Sau khi ly mu, mu phi c y kn v gn nhn. Khi phn tch cc ch tiu vi sinh vt, tt c cc ng c ly mu phi c ra sch v lm kh. S pht trin ca to, nm, vi sinh vt trong cc bnh khng c ra sch c th dn n cc sai s phn tch. Cc bnh cha mu dng ny phi c kh trng trc khi cha mu. Trong qu trnh thu thp mu c sau 5 pht li phi kh trng mt ln. Lng mu cn cho cc phn tch dng ny khong t 100 ml n 1000 ml. Ly mu y bnh v li khong trng trong bnh khong 2 ml, iu ny cho php c th lc u mu sau .b- Cc ly mu t vi nc

Ly mu cng gn ngun cp cng tt. Vic ly mu nc phi ly u vi trnh sai s trong qu trnh ly mu. chy ht phn nc c ri ly mu. Ly y mu t t trnh xut hin bt kh trong bnh cha.

c- Cch ly mu nc mt

Nh phn trn cp ti vic xc nh a im ly mu tng ng vi cc khu vc, mu c ly phi i din cho khu vc nghin cu. Vic ly mu nc mt c th thc hin tng i n gin. Chn la k thut ly mu phc thuc vo mc tiu phn tch. i vi cc mu phn tch vi mc ch kim sot cht lng nc hoc nhim bn mi trng ly mu c th tin hnh n gin, khng cn s dng cc thit b chuyn dng. i vi cc nghin cu xc nh cc c tnh ca nc thng i hi s lng mu ln v thit b ly mu t ng. Thay cho vic ly nhiu mu, c th thu thp d liu ca cc mu n theo chiu su, din tch hoc v tr sau tng hp li. Di y l cc yu cu cn phi thc hin i vi quy trnh ly mu nc mt.


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Mu phi c ly im i din ca khu vc trc quan; tt nht l gia ng ng dn nc hoc gia dng sng, knh, mng. Ly mu di su khng ly nc mt. su yu cu i vi nc mt t nht phi l 20 cm. Nu s dng chai c np, y np di nc trc khi a chai mu ln khi mt nc.

d- Tch, trn mu

Cc mu ngu nhin a phn c ly bng tay t cc ng ng, h cha, sng, sui hoc dng thi. Tuy nhin, cc mu ngu nhin cng c th ly t ng bng cc thit b ly mu chuyn dng. Mi mu s cung cp cc d liu v tnh cht nc thi ti thi im ly mu. Mu tng hp c th c lm bng cch trn u cc mu n hoc c th thu c t cc my ly mu t ng theo cc ln ly v nh lng. Nh vy cc mu c th cho cc kt lun v vic suy gim cht lng nc trong mt khong thi gian di. Trong mt s trng hp, nng cc i khng th xc nh trong cc mu trn ln. T l ln ly mu l hng s gia th tch mu c ly ti cc thi gian xc nh v s phn chia mu. T l nh lng l t s gia vn tc dng chy c thu thp ti mt thi gian xc nh. Khi quan trc dng chy lin tc, vic trn ln mu theo t l nh lng c th c tin hnh (c th lm bng tay) bng cch trn ln lng mu xc nh t cc mu n l khc nhau.Bng 11. V d v vic trn ln mu theo t l nh lng

Thi gian 8 9 10 11 12 13 14 15 16

Vn tc dng chy (m3/s) T l mu ngu nhin c pha trn (L) 1 0,1 2 0,2 1,5 0,15 4 0,4 0,5 0,05 1 0,1 2 0,2 1,5 0,15 0,5 0,05 Tng 1,40 Mu phi c phn tch v chia ra cc bnh khc nhau s dng trong nghin cu,

c xc nh, la chn cng ngh, hoc bo qun mu tham kho, hoc ph v cho cc nghin cu lu di. Quan trng nht l phn tch mu phi chnh xc.

Ly mt th tch ln mu vo mt bnh n v chuyn sang cc bnh nh hn; v

khng nn y cc bnh nh.


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i vi mu c cht rn l lng, yu cu lc mu trc khi chia ra cc phn nh. i vi mu yu cu phi lc trc khi phn tch hoc bo qun, lc ton b mu S dng duy nht mt loi bnh cha cho vic tch mu. Phn tch hot tnh sinh hc trong phn tch cng mt ngy, hoc nhng ngy Bo qun tt c cc mu phn tch trong cng mt phng php; nu khng c Khi xc nh cht nhim bay hi, phi ly y bnh cha mu v y np cn

trc khi phn tch.

gn nu c th. nh trn th vic s dng cc phng php khc nhau phi c ghi li c th. thn. Khng khong trng v khng kh tn ti trong bnh cha.e- Bo qun v lu tr.

Do qu trnh hot ng sinh hc vn tip tc din ra sau khi ly mu nn vic phn tch mu phi c thc hin cng sm cng tt. Vic ny lm gim t l sai s n mc thp nht. Nu khng th phn tch ngay, mu phi c bo qun. Phng php bo qun bao gm bo qun trong iu kin pH ph hp, trong ho cht, trong iu kin lnh.Bng 12. Gii thiu khi qut v phng php bo qun thi gian bo qun cho cc mu c th.

Phn tch Th nghim vi khun Tng s Coliform, phn Phn khun cu chui Th nghim c trong nc c Th nghim ho hc Tnh axit Tnh kim Amni Nhu cu oxi sinh ho (BOD) Bo Brm Nhu cu oxi sinh ho, c

Bnh cha P,G P,G

Bo qun Mt 4oC, Na2S2O3 Mt 4oC, Na2S2O3 Mt 4oC Mt 4oC Mt 4oC Mt 4oC, H2SO4 pH

bai_giang_dtm_-1

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