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Enhancement of 210pO and 210Pb in the vicinity of Syrian phosphate mines and Tartous port

M. S. AI-Masri*, K. AI-Kharfan, H. Khalili, M. Abdel Haleem, Z. AI­Hares

Department of Protection and Safety, Atomic Energy Commission of Syria, Damascus, P. 0. Box 6091 , SYRIA

Introd Detion

Phosphate rocks contain relatively high concentrations of naturally occurring radioactive materials from the uranium and thorium decay series e38U and 232Th). Mining, milling and transporting of phosphate ores and manufacturing of phosphate fertilizers are ways of exposing the workers, public and the environment to enhanced natural radioactivity. These natural radionuclides are concentrated in the solid waste of phosphate fertilizers industry such as phosphogypsum, the effluent discharges and in the emission of air such as radon gas and dust carrying radioactivity. Many studies on the impact of this industry are carried out to assess the risk on human and the environment (Barisic et al., 1992; Caravalho, 1995; Hamam & Landsberger, 1994; Marovic & Sencar, 1995; Martinez & Garcia, 1996; McCartney et al., 1992; MacDonald et al., 1996; Rutherford et al., 1994; Timmrmanas et al., 1996). Some studies (UNSCEAR, 1998; Othman et al., 1992; Othman, 1993) considered radon gas is most important hazard to workers and public in the mines area and phosphate factory including phosphogypsum piles; the dose due to inhalation of radon daughters can be relatively high.

In Syria, the main phosphate mines are situated near Palmyra. The two open pit mine regions are separated by about 25 km; more than 2000 workers are employed in this industry and live in two villages located near the mines (Othman et al., 1993). The climate is very hot and dry where strong wind may arise. In addition, most of the mined phosphate ore is exported for more than 20 years in large quantities via one of the main Syrian ports (Tartous) situated on the east part of the Mediterranean Sea (34 54 NO, 35 52 EO). However, in both areas (mines and export platform), dust-carrying radioactivity is elevated and transported to the surroundings. Studies (Othman et al., 1994; AI-Masri et al., 2001) have reported high concentrations of 2\opO in sediment collected from Tartous shore. On the other hand, studies (Othman et al., 1992,1993) on the impact of this industry on the environment near the mines were limited to the workplace, where radon concentrations in air, and gamma exposure and hence radiation dose to workers have been determined. The main objective of this study was to assess the impact of mining activities and phosphate loading cargoes on the surrounding environment including workers villages by determination of 2\opO and 2\OPb in air particulates and soils; 2\opO and 2\OPb in the phosphate industry environment are mainly due to 222Rn decay and dust carrying phosphate ores .

• Corresponding author, Email: msmasri@aec.org.sy

1

Materials and MethodsSamplingSampling was carried out during loadings and operations at both sites (Tartous portand the mines). Reference sites in both areas were chosen far from the operations. Airparticulates were collected using high volume air samplers (HVAS) with airflow of4.2 - 102 m' hr-'; whatman EPM 2000 filters (20 cm x 25 cm) being used. soilsamples were also collected from the same locations used for air particulate sampling;only the top 5 cm layer of surface soil being collected and placed in plastic bags fortransportation.

Analytical MethodsTotal suspended particulates in each filter were determined by weighing the filterbefore and after sampling. The collected soil samples were oven-dried at 90 oC for 24hr. Each air filter was cut into small pieces and digested using concentrated nitric acidfor at least 24 hr after addition of a known amount of 208Po (0.2 Bq) as a yield tracerfor determination of 210Po and 2l0Pb. For soil samples anaiysis, d.s g of each soilsample (duplicate) was digested using a combination of mineral acids (nitric andhydrochloric acid) for at least 24h. Concentrations of 210Po and 2t0Pb were measuredusing the st?l9ard technique (the sjfyer disc technique) (Harley, 1978). Alphacounting of 208Po (5.15 Mev) and 2t0Po

15.30 Mevi was done using an alphaspectrometer (Oasis, Oxford) with a passive ion-implanted silicon detector (activearea 300 mm', background counts per day 3.6 and the minimum depletion thickness100 pm). The plating and counting were the! repeated after 6 months of storage of thesolution to measure the ingrowth of new 2'oPo from 2l0Pb and to calculate the 2l0Pb

concentration in the original sample. The lower limit of detection of the method usedwas 0.4 Bq kg-t dry vrt.

Soil samples were also measured by gamma spectrometers using high resolution (1.85kev at 1.33 Mev), high relative efficiency (26Yo and 80%) lo_w background HpGedetectors to determine gamma emitting radionuclides such as "oRa by measuring itsgamma emitting daughters "oPb,and

2laBi.

Quality ControlQuality control procedures were applied using homemade control samples andduplicate analysis. Reference samples supplied by IAEA (IAEA-368, SL-1, soil 7,RGU, RGTH) were also analyzed to ensure the accuracy of the analytical resultsobtained in this study.

Results and Discussion

210Po and 210Pb activity concentration in the vicinity of Knefees and Al-Sharkia minesand worker's villages

Tables I and 2 show the mean values of TSP, 2l0Po and 2l0Pb concentration in airparticulates collected from both mines areas and workers villages. TSP concentrations(Knefees mine) varied between 877 1tg m-3 at the worker village and,24106 pg m-3 atthe factory. While in Al-Sharkia, higher concentrations were observed and found to be

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about 56557 pg m-3 at the factory and 55358 pg m-3 at the storage loading cells. Thisis due to the fact that more milling and mining operations being carried out at Al-Sharkia mine. However, all of the reported values here are much higher than themaximum permissible concentrations (120 pg m-3). TSP in worker viiages in bothareas was found to be 877 pg m-' and 848 pg m-' for Knefees and Al-Sharkiarespectively; these values are 7 times higher than the maximum permissibleconcentrations and they may^.b:.e due to.the dry climate and windy weather of theregion. Moreover, uranium, 2l0Po and 2l0Pb concentrations in air particulates of allsites were found to be relatively higher than the natural levels; the highest 2l0Po and2r0Pb concentration were 47 mnq ma and 50 mBq m-3 for Knefees, respectively.Lower levels of radionuclides in Al-Sharkia worker village were observed and theymay be due to the fact that large particles can hardly reach the villages.

Tsble I Mean values of TSP, 2t0Po and2l0Pb conruntration in air at phosphate mines(Knefees)

Table 2 Mean values of TSP, t"'Po and t"tPb concentration in air at phosphate mines(AI-Sharkia)

*: Two frlters were collected and analyzed

Radioactivity content of soil samples collected from the vicinity of the two minesareas were found to be distance and wind direction dependant; the concentrations ofthe studied radionuclides decrease as the distance from the mines area increases(Table 3). Of course, the effect of mining processes is very clear near the mine areaand air particulates are transported by wind to the villages. Uranium ("oTh) activitycontent in soil samples collected near the village Clinic (Knefees village) was foundto be 194 Bq kg-t . In additio.r, ttoPo and 2l0Pb concentrations were also high in thosesamples collected near the village school; I73 Bqkg-r and 233 Bqkg-r being observed

SiteNo. Site Description

TSP't lSDuq m-'

, t tPo

+1SDmBo m-3

, t uPb

+ISDmBq m-3

Adm in is t rat ion Bui ld ine 3466 !2523 6 . 3 r 1 . 3 3 . 1 1 0 . 72 Maintenance Workshoo 925 !334 1 . 6 ! 0 . 4 t .6 ! 0 .4J Workers'Villase 817 !371 1 .8 r 0 .3 l . l t 0 . 64 Control Room 22304 ! 13399 4 7 ! 2 5 5 0 ! 2 95 The Factory 24106 !7458 42.9 r 13.9 34 .8 ! l t . 26 Mine Area 83t'7 ! 4408 t 1 . 6 ! 3 . 3 14.2 ! 9.0

SiteNo.

Site DescriptionTSP-t ISDug m-'

, . tPo

t ISDmBq m-3

, tupb

t ISDmBo m-3

Storase Cells 55358 !27426 5 7 . 2 X 3 4 . 8 28.8 ! 17.02 Dryer Unit 27348 !.10472 14.2 !9 .9J Chemical Laboratory 215t ! 499 3.7 t 0 .8 2 . 3 ! 0 . 3Aa Austrian Factorv NO. A 56557 !43252 J J . t ! t + . t 2 2 . 1 t 9 . 25 Maintenance Workshop 2570 X t503 3 . 9 I 1 . 8 2 . 2 ! 0 . 76 Administration Buildins 692!280 t .4 t0 .2 l . l t 0 . 27 Factory NO. B 5223X708 6.4 ! t .0 2 .7 t0 .28 Electrical Workshop 4740!t952 6.2!2.02 3 . 1 t 1 . 79 Worker's Villase 84816 I 7 t .6+0.2 1 .20 + 0 .03

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fo. 2l0Po and 2l0Pb respectively. These high levels may be due to high radonconcentrations in the area and not the transport of phosphate dust from the mines bywind to the village. Similar values were also found in Al-Sharkia worker village(Table 3). Therefore, radon gas should be measured in air and monitored in thevillages in order to assess the risk to public and workers arising from inhalations ofradon and its daughters.

Tabte 3 Concentration of 210Po, t"'Pb, ttoRa and23tTh in soil samples from workersvillages and mines

2t0Po and2l0Pb activity concentration in the vicinity of Tanous port

Table 4 shows the results of total suspended particulates and mean values of 2lOPo and'toPb concentration in all filters collected from Tartous port area. The results havebeen compared with those obtained for the reference site (ttro. 8), which is 7 km southof the affected area (wind direction in the port area is east north). TSP concentrationswere found to vary between 136 and 2269 1tg m-' at the loading platform. All othervalues were also higher than the reference site value (110 pg m-') and higher than themaximum permissible levels (120 pg m-'). Moreover, it is clear that dust has spreadonly in an area with 500 m radius; this may be due to the fact that large particulatesmay be formed because of the high humidity in air at the coast, therefore it is difficultto travel far distances. However, small air particulates may be carried to far distancesby wind and reach Tartous City.

SiteNo.

Site Description

,roRa

+ISDBo ks-l

,r"Th

+1SDBq ks-r

""Po+ISD

Bq ks-r

""Pb+1SD

Bo ks-lKnefees Mine

I Administration Buildi ne 820 !25 824 ! 100 1455 + 14 1997 ! 1592 Maintenance Workshoo 413 ! t2 432 t 56 7 5 1 t 3 8 l 0 1 l + 8 1J Dryer Unit 821 + 26 824 + 100 1479 + 73 2022 + 1624 The Factorv 3r7 t t0 312 + lg 6 0 1 + 3 1 8 8 5 + 7 15 The Mine Area 5 1 0 r 1 5 5 1 0 + 4 8 760 + 39 1033 + 826 Village, Main Gate 820 + 30 7 5 0 ! 7 0 '1184 ! 62 t557 + 1247 Village, Hieh School 1 2 0 t 5 r z r 1 t z 1 7 3 t 1 0 2 3 3 ! t 98 Vi l lase Cl in ic 193t 6 194 X23 339 ! 17 416 t389 Villaee. Guest House 8 5 i 3 84 r8 1 4 8 r 8 2 1 1 ! t 7

Al-Sharkiu MineI Loadins Cells 413tt2 482!63 731 r 50 809 r 652 Dryer Unit 5 1 0 r 1 5 522+50 7s6! 6 1 847 t68J Chemical Laboratory 382!20 442+53 794 x 63 816 t70A Austrian Factorv NO. A 422t 2 408!52 l l 9 8 t 8 9 1266 ! 1015 Maintenance Division 364! 2 366!46 553 + 41 3 8 8 t 3 16 Adm in is t rat ion Bu i ld ine 396+ 2 366!46 422 + 42 374 + 307 Factory NO. B 408+2 423+55 692 + 36 704 ! s68 Electrical Workshoo 460+ t+ 461t60 749 t39 1048 1 849 lase. Police Station I 28r5 I l 3 r l 5 . 5 z J J ! t z 330 t26l 0 lage, The Mosque 87r3 75t l 0 1 5 3 + 8 235 !291 t The Mine 28018.5 283t34 454 + 23 679 + 54

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2l0Po and 2toPb concentrations in particulates were found to be high in comparison tothe reported values of the reference site. 2l0Po in particulat", r*g.d from 1.b mBq m-'

lTartous City) and 305 mBq m-l at the loading platform; the natural levels Ueingbetween 0.47-3.7 mBq m-' (Eisenbud & Gesell, 1997). Similar relation was observedfor 2l0Pb at the same locations. The highest concentration of 2l0Pb was 160 mBq m:r,which is 43 times higher than the natural levels (3.7 mBq m-3;. However, the highestconcentrations were found to be within the 500 m circle from the loading platform. Itcan be suggested that wind direction and speed in the areamay affect this distribution;air particulate carrying radioactivity can reach other areas situated several km north ofthe port.

Table 3 Mean values of TSP, t"'Po and2t0Pb concentration in air at the vicinitv of Tartousport area

*: Only one measurement*: Two hlters were collected and analyzed

Table 5 shows the results of natural radioactivity concentrations of soil samplescollected from Tartous area. By examining the results,226Ra,23oTh (uranium), 2l0po

and 2l0Pb in soils collected near the loading platform contain high levels, which isalmost phosphate ore. However, it is also clear by moving out of the port area, theconcentrations were decreased and especially for 23aTh and, "uku, while 2l0po and2l0Pb concentrations were found to be relatively high in all other sites, even at thereference site. 2l0Po and 210Pb concentrations varied between 13 and 1175 Bq kg-l and73 and,925 Bqkg-r, respectively. These high concenlrations in soil may be Aue to trigttradon concentrations in the area, and hence high 2l0Pb and 2l0po fluxes, and not thetransport of phosphate dust generated during loading and de-loading operations.Therefore, radon gas, which is generated from the phosphate piles stored near theplatform in large quantities before exporting, can be considered the main hazard inthese sites. Radon gas in air should be measured and monitored and the risk arisingfrom inhalation should be assessed.

SiteNo. Site Description

TSP-+ ISD

(us m-3)

tlupo

t ISD(mBq m-3)

""Pb+ISD

(mBo m-3)Loadine Platform 2263' 305r39 I 6019

z North of Loadine Platform 1779!963 45+0.7 3.7+0.2J 400m East of Loadins Platform t22t!973 10.5 !2 .6 2.6+0.2A De-Loadins Station 2269!t',708 l 3 + l I 1.9r0 .55 Al-Maxer Area l ' 79 ! 27 1.7 t0 .01 1.810.26 Maintenance Workshop 136t57 2t0 .1 1.7010.037 Tartous City l 7 l138 1.0r0.6 0.8t0.18 Tartous Beach Cabins (Ref Site) 1 l 0 r l 5 1.6!0.4 1.6!0.2

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SiteNo.

Site Description

,roRa

t ISDBq ks-r

"'"Pot lSD

Bo ks-r

, tupb

t ISDBq ks-l

-'Th

+ISDBo ks-l

Weather Forecast Center 1 9 1 I 7 3 t 6 7 5 t l 2 1 + 42 Port Custom Buildins I 4 t ! 3 109 r6 121! 6 2 7 ! 6aJ Administration Bui ldine 530 !31 828+ l 5 688 r 96 4001 84Aa Civil Construction Buildins 28 ! 2 105 t2 73 ! 125 Loadine Platform I 656 ! 45 l l 7 5 l t 3 874 + 55 4 1 8 1 8 86 Loadins Platform 2 297 + 20 657 + 68 620 + 407 Port Custom Buildins 2 20.7 + 1 .4 2 0 1 ! 3 1 146 x 16 15 r 38 Tartous City I n .6 r 1 .7 8 l + 7 7 3 + 69 Arwad Island 8.4 r 0.6 2 6 ! 0 . 3 3 l + 2 8 . 3 + 1 . 7t 0 De-Loadins Station 580 t 40 1 0 3 0 r 1 2 8 925 !10 419 t t00u Tanous City 2 144 t t0 2 2 4 + 1 2 3 8 + 5 144 + 30

t2 400 m East of the LoadinsPlatform 4 1 5 r 3 0 641 + 4l 455 + 50 300 r 63

Table 5 Natural radioactivity concentration in soil somples collected from the vicinityof Tartous port

ConclusionEnhanced 2l0Po and 2l0Pb activity concentrations were found to be in air particulatesand soil samples collected from the phosphate mines and export platforms at Tartousport. The highest levels of '''Po and 'ruPb were found to be more located at theworkplace in the mines areas and the export p.latform, where phosphate dust carryingradioactivity being the most important risk. '''Po is also found to be enhanced than'''Pb, which is due to the fact that 2loPo is more volatile than 210pb.

AcknowledgmentMany thanks to Prof. I. Othman (G.D. of AECS) for his encouragement and support.In addition, the authors would like to thank member staff of the low-levelmeasurement for their time spent for measuring of the prepared samples.

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