ground water sampling & analysis technique
TRANSCRIPT
Groundwater Quality Analysis
Dr. V. Arutchelvan & Atun RoyChoudhuryProfessor & Head of Civil Engineering, M.E.
Scholar & Research AssistantAnnamalai University
Introduction Indian Ground Water Scenario and Brief Management Groundwater Quality
– Sampling Plan– Field Measured Parameters
• pH• Alkalinity• Conductance• Salinity• Dissolved Oxygen• Turbidity
– Chemical Equivalence– Laboratory QA/QC– Diagrams
• Piper• Stiff
– Water Quality Classification– Ground water Quality & Associated Problems – Irrigation Water
• Sodium• Salinity
– Arsenic– Fluoride– Iron– Nitrates
Recent Advancements & Remedial Measures
• Water is the most important in shaping the land and regulating the climate. It is one of the most important compounds that profoundly influence life.
• In the last few decades, there has been a tremendous increase in the demand for fresh water due to rapid growth of population and the accelerated pace of industrialization.
• Groundwater is used for domestic and industrial water supply and also for irrigation purposes in all over the world.
• According to WHO organization, about 80% of all the diseases in human beings are caused by water.
• Once the groundwater is contaminated, its quality cannot be restored back easily and to device ways and means to protect it.
Groundwater Quality
• Helps us understand the hydrogeologic system
• Indicates comingling of groundwater and surface water
• Helps us interpret groundwater flow dynamics• Delineates groundwater contamination
• Water quality index is one of the most effective tools to communicate information on the quality of water to the concerned citizens and policy makers.
• It, thus, becomes an important parameter for the assessment and management of groundwater.
• The more common soluble constituents include calcium, sodium, bicarbonate and sulphate ions.
WQI Status Possible Usage
0-25
26-50
51-75
76=100
101-150
150
Excellent
Good
Fair
Poor
Very Poor
Unfit for Drinking
Drinking, Irrigation & IndustriesDomestic, Irrigation & IndustriesIrrigation & Industries
Irrigation
Restricted use for Irrigation
Proper Treatment Required
• Another common constituent is chloride ion derived from intruded sea water, connate water, and evapotranspiration concentrating salts, and sewage wastes, for example Nitrate can be a natural constituent but high concentrations often suggest a source of pollution.
• Water quality standards are needed to determine whether ground water of a certain quality is suitable for its intended use.
• Due to increasing urbanization, surface water is getting over contaminated and more stringent treatments would be required to make surface water potable. Therefore, it is required to additional sources for fulfil the requirement of water. Because the ground water sources are safe and potable for drinking and other useful purposes of human being. Hence studies of physic-chemical characteristics of underground water to find out whether it is fit for drinking or some other beneficial uses.
DYNAMIC GROUND WATER RESOURCES OF INDIA
Annual Replenishable Ground Water• Resources 433 BCM.
• Net Annual Ground Water Availability 398 BCM.
• Annual Ground Water Draft for Irrigation, Domestic & Industrial uses 245 BCM.
• Stage of Ground Water Development 62% Categorization of Blocks / Mandals/ Firkka Talukas.
• Total Assessed units 6607
Safe 4530 Semi-Critical 697 Critical 217 Over-Exploited 1071 Saline 92
Precipitation map of India
Annual Recharge & Withdrawal of Ground Water
Ground Water Quality & Depth in Various Parts of Our Country
Ground Water Stage in India
Sampling and Analysis Plan
• Document written in advance of sampling that defines:– Sampling locations and frequency– How field parameters are measured– How samples are collected– Quality control and assurance measures
• Do NOT go to the field without a plan!
Groundwater Sampling• Important Points
– Be sure to take a representative sample– Make sure sample bottles are properly rinsed– Filter and preserve samples in the field– Take field measurements with proper equipment– Store on ice– Send to a certified water chemistry laboratory within
24 hours of sampling– Have a quality control program with duplicates,
blanks, field blanks, or spiked samples
Groundwater Sampling MethodsSampling is the process of obtaining, containerizing, and preserving (if required) a
ground water sample after the purging process is complete. There are few technical methods, which can be adopted for collection of
representative samples are- Sampling Wells With In-Place Plumbing
Samples should be collected following purging from a valve or cold water tap as near to the well as possible, preferably prior to any storage/pressure tanks or physical/chemical treatment system that might be present.
Sampling Wells Without Plumbing, Within the Limit of Suction The pump of choice for sampling ground water within the limit of suction is the variable- speed peristaltic pump. Its use is described in the following sections. Other acceptable alternatives that may be used under these conditions are the RediFlo2® electric submersible pump (with Teflon® tubing) and a closed-top Teflon® bailer.
(variable speed peristaltic pump/ Peristaltic Pump/ Vacuum jug/ RediFlo2 Electric Submersible Pump/ Bailers)
Sampling Wells without Plumbing, Exceeding the Limit of SuctionRediFlo2® Electric Submersible Pumps, and Bailers, are suitable sample methods
where the water table is too deep to consider the use of a peristaltic pump for sampling.
Micro-Purge or No Purge Sampling Procedures The Micro-Purge or No Purge sampling procedures are usually employed when it
necessary to keep purge volumes to an absolute minimum. Among the Micro-Purge or No Purge procedures that might be employed are:
Low pump rate sampling with peristaltic or submersible pumps (typical Micro-Purge sampling), TM HydraSleeve or Passive diffusion bag (PDB) sampling
WELL SAMPLING
• Calculate Well Volume: – Determine static water level– Calculate volume of water in the well casing
• Purge the well: – A minimum of three casing volumes is
recommended.
Post Sampling Procedures• Sample Preservation Consult the Analytical Support Branch Laboratory Operations and Quality
Assurance Manual (ASBLOQAM) for the correct preservative for the particular analytes of interest.
All samples preserved using a pH adjustment.• Filtering Filtering will usually only be performed to determine the fraction of major
ions and trace metals passing the filter and used for flow system analysis For the purpose of geochemical speciation modeling.• Specific Sampling Equipment Quality Assurance Techniques All equipment used to collect ground water samples shall be cleaned as
outlined in the SESD Operating Procedure for Field Equipment Cleaning and Decontamination (SESDPROC-205).
• Auxiliary Data Collection Well Pumping Rate – Bucket/Stop Watch Method
Typical Field Sampling Form
Sampling Equipments...
Water UsesUse Typical quality parameters
Public Water Supply Turbidity, TDS, inorganic and organic compounds, microbes
Water contact recreation Turbidity, bacteria, toxic compounds
Fish propagation and wildlife DO, chlorinated organic compounds
Industrial water supply Suspended and dissolved constituents
Agricultural water supply Sodium, TDS
Shellfish harvesting DO, bacteria
Abundance of Dissolved Constituents in Surface and Ground Water
• Major Constituents (> 5 mg/L) –Ca–Mg–Na–Cl–Si–SO4
2- - sulfate–H2CO3 - carbonic acid–HCO3
- - bicarbonate
Abundance of Dissolved Constituents in Surface and Ground Water
• Minor Constituents (0.01-10 mg/L)–B–K–F–Sr–Fe–CO3
2- - carbonate–NO3
- - nitrate
Abundance of Dissolved Constituents in Surface and Ground Water
• Trace Constituents (< 0.1 mg/l)–Al–As–Ba–Br–Cd–Co–Cu
– Pb– Mn– Ni– Se– Ag– Zn – others
Water Classification
• How?– Compare ions with ions using chemical equivalence– Making sure anions and cations balance– Use of diagrams and models
• Why?– Helps define origin of the water – Indicates residence time in the aquifer– Aids in defining the hydrogeology– Defines suitability
What is Chemical Equivalence?
• Chemical analysis of groundwater samples– Concentrations of ions are reported by
• weight (mg/L) • chemical equivalence (meq/L)
• Takes into account ionic charge• Equivalent Concentration
Formula weight• Formula weight
– Multiply atomic weight by # of atoms and add together
• E.g., – Formula weight of water
H2O = 2*(Atomic Wt of H) + 1*(Atomic Wt of O)
2*(1.008) + 1*(16) = 18.01
Atomic Weight (Relative atomic mass) is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12
Ion Balance
• If all ions are correctly determined by a labsum of cations should equal sum of anions (all in
meq/L) • Errors in analysis and chemical reactions in
samples 5% difference is considered acceptable> 5%, question the lab results
Calculating Equivalence
ParameterSandstone Aquifer
mg/L Meq/L
Na+ 19 0.827
Cl- 13 0.367
SO42- 7 0.146
Ca2+ 88 4,391
Mg2+ 7.3 0.6
HCO3- 320 5.245
Total Anions 5.758
Total Cations5.818
% Difference 1%
For instance:
The atomic wt. of Sodium (valence of one) = 22.989
And its charge is one
Dividing the concentration of sodium in the sample (19 mg/L) by its “combining wt.” = 0.827 meq/L or its equivalent concentration.
Use of Diagrams
• There numerous types of diagrams on which anions and cations (in meq/L) can be plotted.
• It is a graphical representation of the chemistry of a water samples in hydro geological studies These include:Piper - comparing the Ionic compounds of the set of water samples
but does not lend to spatial comparison
Stiff – for geographical applications, the stiff diagram are more applicable because they can be used as marker on a map
Pie – statistical graphical representation
Piper Diagram
Stiff Diagrams• Concentrations of
cations are plotted to the left of the vertical axis and anions are plotted to the right (meq/L)
• The points are connected to form a polygon.
• Waters of similar quality have distinctive shapes.
!(!(
!(
!(
yk-31
yk-16
yk-27
yk-101
Stiff Diagrams in Cyprus
Pie Diagrams
Igneous Volcanic
Na
CaMg
Cl
SO4
HCO3
NO3
Sandstone Aquifer
Na
Ca
Mg
Cl
SO4
HCO3
NO3
Shale with Salts
NaCa
MgClSO4
HCO3NO3
Calcium bicarbonate waterCalcium bicarbonate water Magnesium bicarbonate Magnesium bicarbonate waterwater
Sodium chloride waterSodium chloride water Sodium-calcium bicarbonate Sodium-calcium bicarbonate water with nitrateswater with nitrates
Alluvium
Na
Ca
Mg
ClSO4
HCO3
NO3
Average Composition of Sea Water and Mississippi River water
Parameter Sea water (mg/L)
Mississippi River water (mg/L)
Na 10,500 20Cl 19,000 24
SO4 2,700 51Ca 410 38Mg 390 10
HCO3 142 113
Ground Water Quality in Different Aquifers
Parameter Sandstone Aquifer
Limestone Aquifer
Igneous/Volcanic Aquifer
Shale with Salts
Alluvium(Farmland)
pH 7.5 7.8 6.5 7.1 7.4
Na 19 29 184 1220 114
Cl 13 53 6 1980 30
SO4 7 60 7 1000 74
Ca 88 144 34 353 64
Mg 7.3 55 242 159 19
HCO3 320 622 1,300 355 402
NO3 0.4 0.3 0.2 2.4 60
Aquatic Freshwater Protection Criteria (USEPA Guidelines)
Criteria Recommended Standard
pH 6.5-9.5
Alkalinity 20 mg/L or more
Dissolved Oxygen30 day average 5.5 mg/L
(warm water fish)
Suspended Solids Should not reduce Photosynthesis by more than 10% in the water
Drinking Water Criteria(USEPA Guidelines)
Criteria Recommended Standard Reason
Coliform Bacteria 0 colonies/ml Health
pH 6.5-8.5 Aesthetic
Barium 2 mg/LHealth
Nitrate 10 mg/L Health
Total Dissolved Solids 500 mg/L Taste
Basic Water Quality Parameters• pH• Specific conductance (EC)• Salinity• Total dissolved solids (TDS)• Turbidity • Dissolved oxygen (DO)• Biochemical oxygen demand (BOD)• Temperature• Total Hardness
• Magnesium• Sulphate• Nitrate • M.P.N.• Total alkalinity • Chloride• Fluoride• Boron• Phosphates
• C.O.D.• Iron & Manganese• Cadmium• Chromium• Nickel• Zinc• Sodium
pH• Measures hydrogen ion
concentration• Negative log of hydrogen ion
concentration• Ranges from 0 to 14 std. units • pH
– 7 neutral– 0 - 7 acidic – 7 - 14 alkaline
Thanks to Phil Brown
Solubility of Specific IonsBased on Water pH
Toxic metals less available in water at pH 6 to 8. Toxic metals less available in water at pH 6 to 8.
Alkalinity
• “acid neutralizing capacity”• Important because it buffers the water against
changes in pH• For most waters, alkalinity includes the
bicarbonate ion (HCO3-)
• Other ions such as orthophosphate (HPO4-),
borates, may contribute to alkalinity but in small amounts
Conductivity• Measures electric
conductivity (EC) of water• Higher value means water
is a better electrical conductor
• Increases when more salt (e.g., sodium chloride) is dissolved in water
• Indirect measure of salinity• Units are μmhos/cm at 25o
C or μsiemens/cm
Thanks to Phil Brown
Electrical conductivity of GW due to presence of salts
Conductivity at Barton Springs• Specific conductance is an indication of the hardness of water. The specific
conductance declines in spring water when rainfall enters the aquifer and later discharges in the spring. Below is a graph demonstrating this effect in Barton Springs. Rainfall is indicated in red, and specific conductance in blue.
Salinity
• Classification of Ground Water• Composition Based on Total Dissolved
Solids Content
Salts in Sea Water
Type of Water Dissolved salt content (mg/l)Fresh water < 1,000 mg/l
Brackish water 1,000 - 3,000 mg/l
Moderatly saline water
3,000 - 10,000 mg/l
Highly saline water 10,000 - 35,000 mg/l
Sea water > 35,000 mg/l
Dissolved Oxygen• Amount of gaseous oxygen
(O2) dissolved in water • Oxygen gets into water by
diffusion from the surrounding air, by aeration, and through photosynthesis
• DO range from 0-18 mg/l• Need 5-6 mg/l to support a
diverse population• DO < 2 mg/l - Hypoxia
Thanks to Phil Brown
Turbidity• Measured in Nephelometric
Turbidity Units (NTU)• Estimates light scattering by
suspended particles• Photocell set at 90o to the
direction of light beam to estimate scattered rather than absorbed light
• Good correlation with concentration of particles in water
Thanks to Phil BrownYSI 556 MPS
HF Scientific MicroTPI – Turbidity Meter
Total Dissolved Solids
• One measure of the quality of the water in lakes, rivers, and streams is the total amount of solids dissolved in the water. High amounts of dissolved solids can indicate poor water quality. The same is true for drinking water.
Methods:• Gravimetric method.• Electrical Conductivity.
Gravimetric method. • Gravimetric means "by weighing". Balances
require gravity to weigh something. You will weigh the total dissolved solids after water is boiled away. This will be done using just one water sample.
Procedure:• To measure TDS using this method, the water
sample is first passed through a filter that blocks anything bigger than 2 microns ( 2 micrometers or 2 millionths of a meter).
• This ensures the test measures dissolved solids not solids suspended in the water. Such things as sediment or specks of plant material are filtered out and therefore not counted in the "total dissolved solids“
• A certain amount of the filtered water is then weighed out and the water is boiled away leaving the dissolved solids behind as a solid residue. This residue is weighed. This is called the gravimetric method because a balance is used. Balances need gravity to find the mass. So that's why it's called a gravimetric method.
NitrateSources:• Fertilizers and manure• Decayed vegetable• Animal feedlots• Municipal wastewater and sludge disposal to land • Industrial discharges• Leachates from refuse dumps• Septic systems
Methods for Nitrate Estimation
Ultraviolet Spectrophotometric Method• Filter the sample.• Add 1 ml of 1N HCl per 50 ml of sample.• Read absorbance or transmittance at 220 nm
and 275 nm.• Set 0 absorbance or 100% transmittance with
distilled water.
Nitrate Electrode Method
• Useful for Nitrate concentration range of 0.14 to 1400 mg/L
• NO3-N• Interferences• Chloride and bicarbonate with weight ratios to
NO3-N >10 or >5 respectively
• NO2, CN, Sulphide, Br, I, Chlorite and Chlorate
Phenoldisulphonic Acid (PDA) Method
• Nitrate reacts with Phenoldisulphonic acid to produce nitro derivatives that in alkaline solution rearranges its structure to form yellow colour compound with characteristics that follows
• Beer’s law• Chloride interferes seriously which can be
overcome by precipitation of chloride with Ag+ as AgCl
Presence of Nitrate • Nitrate is a very common constituent in the ground water, especially in
shallow aquifers due to anthropogenic activities. High concentration of Nitrate in water beyond the permissible limit of 45 mg/l causes health problems.
Chlorides
Source:• Dissolution of salt deposits• Discharges of effluents• Oil well operations• Sewage discharges• Irrigation drainage• Sea water intrusion in coastal area
• Methodology : An Argentometric MethodPrinciple• Chloride is determined in a natural or slightly
alkaline solution by titration with standard silver nitrate, using potassium chromate as an indicator. Silver chloride is quantitatively precipitated before red silver chromate is formed.
• Chloride mg/L = (A-B) x N x 35.45 x 1000ml sample• Where A = ml AgNO3 required for sample• B = ml AgNO3 required for blank• N = Normality of AgNO3 used
Fluoride
Significance:• Dual significance in water• High concentration of F- causes dental
Fluorosis• Concentration < 0.8 mg/L results in dental
Carries• Essential to maintain F- concentration
between 0.8 mg/L to 1.0 mg/L in drinking water
Methods:• Colorimetric SPADNS MethodPrinciple: • Under acidic conditions fluorides (HF) react with
zirconium• SPADNS solution and the lake (colour of SPADNS
reagent) gets• bleached due to formation of ZrF6 . Since
bleaching is a function of• fluoride ions, it is directly proportional to the
concentration of fluoride.• It obeys Beer’s law in a reverse manner.
Ion Selective Electrode MethodPrinciple: • The fluoride sensitive electrode is of the solid
state type, consisting of a lanthanum fluoride crystal; in use it forms a cell in combination with a reference electrode, normally the calomel electrode.
• The crystal contacts the sample solution at one face and an internal reference solution at the other.
• A potential is established by the presence of fluoride ions across the crystal which is measured by a device called ion meter or by any modern pH meter having an expanded milli volt scale.
• Calculate mg F- / L present in the sample using standard curve.
Presence of Fluoride85 % of rural population of the country uses ground water for drinking and domestic purposes, which contains a high concentration of fluorides (> 1.5 mg /litre).
Sulphate
Significance:• Occurs in natural water• High concentration of Sulphate laxative effect• (enhances when sulphate consumed with
magnesium)• Problem of scaling in industrial water supplies• Problem of odour and corrosion in wastewater
treatment due to its reduction to H2S
Spectorphotometric Method
Principle: • Sulfate ions are precipitated as BaSO4 in acidic
media (HCl) with Barium Chloride.• The absorption of light by this precipitated
suspension is measured by• Spectrophotometer at 420 nm or scattering of
light by NephelometerCalculate:• mg / L SO4 = mg SO4 x 1000• ml sample
Ammonia
• Ammonia is present naturally in surface and wastewaters. Its concentration is generally low in ground waters because it adsorbs in soil particles and clays and is not leached readily from soils.
• It is produced largely by de-amination of organic nitrogen containing compounds and by hydrolysis of urea.
• The graduated yellow to brown colors produced by nessler-ammonia reaction absorb strongly over wide wavelength range
• Low ammonia concentration of 0.4 to 5 mg/L can be measured with acceptable sensitivity in wavelength region from 400 to 425 nm with 1cms light path
• A light path of 5 cm extends measurements of ammonia concentrationsrange of 5 to 60 μg/L
• In the chlorination of water, chlorine reacts with ammonia to form mono and dichloramines (combined residual chlorine)
• Ammonia concentration in water vary from less than 10μg in some natural surface and ground waters to more than 30 mg/L in some wastewaters.
Methods for Ammonia Estimation
Nesslerization Method:• Direct nesslerization method is useful for
purified natural water and highly purified wastewater effluents with very light color and having NH3-N concentrations more than 20 μg/L.
• Applicable to domestic wastewater only when errors of 1 to 2 mg/L are acceptable.
Ammonia Selective Electrode Method• The ammonia selective electrode uses a hydro-
phobic gas permeable membrane to separate the sample solution from an electrode internal solution of ammonium chloride
• Dissolved ammonia is converted to NH3(aq) by raising pH to above 11 with a strong base, which diffuses through membrane and changes the internal solution pH that is sensed by a pH electrode
• The fixed level of chloride in the internal solution is sensed by a chloride ion-selective electrode that serves as the reference electrode.
• Applicable to the measurement of 0.03 to 1400 mg NH3-N/L in potable and surface waters and domestic and industrial wastes.
• High concentrations of dissolved ions affect the measurements but color and turbidity do not.
Titrimetric Method
• The method is used only on samples that have
been carried through preliminary distillation.
• Titrate ammonia in distillate using standard
0.02N Sulphuric acid with boric acid indicator
solution.
Phosphates
• Phosphate occurs in traces in many natural waters, and often in appreciable amounts during periods of low biologic productivity. Waters receiving raw or treated sewage agricultural drainage, and certain industrial waters normally contain significant concentrations of phosphate.
Methods for Phosphorus Estimation
Vanadomolybdo phosphoric Acid Method• In a dilute orthophosphate solution, ammonium
molybdate reacts under acid conditions to form a heteropoly acid. In the presence of vanadium, yellow vanadomolybdo phosphoric acid is formed. The intensity of yellow color is proportional to phosphate concentration.
• Minimum detectable concentration is 0.2 mg P/L in 1 cm cell.
Procedure• Sample pH adjustment if pH > 10• Removal of excessive color by shaking with
activated carbon• Colour development with vanadate-
molybdate reagent• Measurement of color absorbance at
wavelength of 400 to 490 nm
Stannous Chloride Method• Molybdo phophoric acid is formed and reduced by
stannous chloride to intensely colored molybdenum blue.
• This method is more sensitive than above method and minimum detectable concentration is about 3 μg P/L.
• Procedure• Sample pH adjustment if pH > 10• Color development with molybdate reagent• Measurement of color absorbance at wavelength of
690 nm
Limit of Iron and Manganese inDrinking Water
• As per WHO guidelines for domestic water, iron should not
• exceed the limit of 0.3 mg/l• Above 200mg/l iron is toxic to human health• Manganese concentration as per WHO guideline
is 0.05 mg/l• However average manganese level in drinking
water range from 5 to 25 ug/l• At concentration exceeding 0.15 mg/l,manganese
imparts undesirable taste
Iron and Manganese• Presence of excess of iron and manganese in water
causes discoloration, turbidity and deposits. • Iron and manganese bearing water have astringent
metallic or bitter taste.• Precipitation of iron and manganese imparts colour to
water from yellow to brownish black, which becomes objectionable to consumers.
• Manganese concentration ranging from 8-14 mg/l is toxic to human.
• Excess of iron facilitates growth of iron bacteria which causes blocking of pipes, meters etc.
Methods for Detection of Iron and Manganese in Water
• Atomic Absorption spectrophotometer (AAS)• Inductively Coupled Plasma (ICP)• Colorimetric method• In colorimetric method iron is detected at
wavelength 510 nm and manganese is detected at 525 nm.
• 1. Iron:- Phenanthroline method• 2. Manganese:- Persulphate method Periodate
method
Presence of IronHigh concentration of Iron (>1.0 mg/l) in ground water has been observed in more than 110 thousands habitations in the country.
T07_04_02
Hardness of Water
ANALYSIS OF WATER SAMPLES
• Field:– pH, specific conductance, temperature,
dissolved oxygen, and alkalinity• Laboratory:
– Cations: sodium, calcium magnesium, potassium, and iron
– Anions: bicarbonate, carbonate, sulfate, and chloride
– Trace Metals, Radioactivity
Ground water Quality & Associated Problems
Indian Sub- Continent is endowed with diverse geological formations from oldest Achaeans to Recent alluviums and characterized by varying climatic conditions in different parts of the country.
The main ground water quality problems in India are as follows- Inland Salinity (Rajasthan, Haryana, Gujarat, Andhra Pradesh, Maharashtra,
Tamil Nadu etc.) Coastal Salinity (The Indian subcontinent has a dynamic coastline of about
7500 km length, which stretches from Rann of Kutch in Gujarat to Konkan and Malabar coast to Kanyakumari)
3 probable cases of coastal salinity Saline water overlying fresh water aquifer Fresh water overlying saline water Alternating sequence of fresh water and saline water aquifers
Sodium and Irrigation
• Sodium reacts with soil to reduce permeability.• Alkali soils - High sodium with carbonate• Saline soils – High sodium with chloride or sulphate• Neither support plant growth• Sodium Adsorption Ratio (SAR) is a measure of the suitability of water
for use in agricultural irrigation, as determined by the concentrations of solids dissolved in the water. It is also a measure of the sodicity of soil, as determined from analysis of water extracted from the soil.
Sodium and Irrigation• Low-sodium water
– Used on all soils with little danger of harmful levels of exchangeable sodium.
• Medium-sodium water – appreciable sodium hazard in certain fine-textured soils
• High-sodium water – harmful levels of exchangeable sodium in most soils – require special soil management such as good drainage,
leaching, and additions of organic matter.• Very high sodium water
– unsatisfactory for irrigation unless special action is taken, such as addition of gypsum to the soil
Salinity and irrigation• Low salinity water
– used for most crops• Medium salinity water
– used with moderate amount of leaching (potatoes, corn, wheat, oats, and alfalfa)
• High salinity water – Cannot be used on soils having restricted drainage.
• Very high salinity water – Can be used only on certain crops and then only if
special practices are followed
Arsenic in Groundwater• Long-term exposure to arsenic from drinking
water is directly linked to:– Cancer of the skin, lungs, urinary bladder and kidneys.– Acute gastrointestinal and cardiac damage as well as
vascular disorders such as Blackfoot disease. – Sub-lethal effects include diabetes, keratosis, heart
disease and high blood pressure.• Toxicity is dependent on diet and health, but is
cumulative. Arsenic is excreted very slowly by the body through deposition in the hair and nails.
BACKGROUND• Arsenic (As)
– toxic metal widespread in groundwater• Occurs widely in aquifers
– deltaic sediments near mountain uplift zones– deep sandy aquifer layers originating as riverine, lake
or coastal deposits. – Ganges, Mekong and Red River deltas, sandy alluvial
deposits in South Asia, South East Asia, South America, and in many parts of North America and Europe.
Chemistry
• Arsenic has the ability to switch between two valency forms, – As3+ and As5+.
• As3+ – more soluble and more likely to be absorbed than As5+ – This switching property makes detection and
measurement difficult and frequently unreliable
Arsenic Contamination
• Associated with fluctuating water tables and flooding cycles particularly in – Acidic sulfate soils or – Iron and/or manganese-enriched layers, – saline-layered aquifers
• Levels in water supplies can vary through a year adding to the difficulties of identification and monitoring.
Drinking Water Standards
• Worldwide 50 ppb limit (1942) • US EPA
– Acceptable mortality = 1 death per 1,000 people for carcinogens
– Lifetime risk from exposure to 50 ppb As • 13 cancer-related deaths per year per 1000 people
(1992)
– Current standard = 10 ppb standard
Arsenic in the United States
• USGS analyzed US water quality data • 10 ppb level exceeded by 8% of public ground
waters tested• EPA estimates that the 10 ppb rule affects
about 4,000 water systems• "Hotspots" of high concentration
– Central New England– Midwest – Western states.
Arsenic in the United States
Presence of Arsenic India Arsenic occurs naturally in the environment as an element of the
earth’s crust with an abundance of 1.8 ppm by weight.
Determination of MetalsInductively Coupled Plasma-Atomic
Emission Spectrometer
Instrument set up
• Warm up for 30 min• Check the alignment of plasma torch• Make Cu/Mn ratio adjustment• Calibrate instrument using calibration standards
and blank• Aspirate the standard and blank for 15s• Rinse with calibration blank for at least 60s to
eliminate anycarryover from previous standards• Ensure the concentration values within the 5%
error
Analysis of samples• Analysis the samples using calibration blank.• Analyse samples alternately with analyses of
calibration blank.• Rinse at least for 60s.• Examine each analysis of the calibration blank to
verify that carry over memory effect is no more.• Make appropriate dilutions of the sample to
determine concentrations beyond the linear calibration.
Lab Procedures
• Preparing your filters• Rinse three filters with 20-30 mL DI to
remove any solids that may remain from the manufacturing process. Place the filters in separate, labeled aluminum weight pans, dry them in a 104oC oven for 30 minutes, place them (filter and pan) in a desiccator, and obtain a constant weight by repeating the oven and desiccation steps.
• 2.Filter 100.mL of sample through each pre-weighed filter.
• 3.Place each paper in its aluminum weight pan in the 104oC oven for 1 hour. Cool the filter and pan in a desiccator and obtain a constant weight by repeating the drying and desiccation steps.
• Calculation:• TSS mg/L=• (average weight from step 3 in g - average
inital weight from step 1 in g)(1000mg/L)/(sample volume in L)
Research Institutes in India• Rajiv Gandhi National Ground
Water Training & Research Institute, India
Rajiv Gandhi National Ground Water Training & Research Institute was established during IX thFive Year Plan at Raipur as a training wing of Central Ground Water Board, Ministry of Water Resources, Government of India and is running continuously since 1997.
The RGNGWTRI is envisaged to function as a `Centre of Excellence’ in training ground water resources personnel.
Recent Advancements & Remedial Measures
In order to nullify the ill effects of the anthropogenic activities, which causes depletion and contamination of ground water, the following measures can be implemented-
Heliborne Survey Aquifer Mapping Participatory Ground Water Management Artificial Ground Water Recharge etc.
Heliborne Survey
• In India airborne geophysical surveys have been conducted for mineral prospecting and geological mapping by RSAS (GSI), NGRI, NRSC and AMD.
Aquifer Mapping
Aquifer Map for Cuddalore District• The aquifer disposition and
aquifer characterization has been brought by analysis of 45 lithologs (includes 11 lithologs generated during the pilot project), 22 electrical logs (includes 9 generated in the project) , 56 hydrograph of dugwells (53 established in project study), 35 piezometric head (15 piezometers established in project), 61 hydrochemical data (46 dugwells and 15 zone wells established in the pilot project).
Participatory Ground Water Management
• The scarcity of water resources and ever increasing demand of these vital resources require identification, quantification and management of ground water in a way that prevents overexploitation and consequent economic and environmental damage, while satisfying demand for water supply of competing sectors.
• Participatory ground water management is essential at grass root level to enable the community and stake holders to monitor and manage the ground water as common pool resources themselves.
• It is imperative to have the aquifer mapping activity with a road map for groundwater management plan to ensure its transition into a participatory groundwater management programme for effective implementation.
Artificial Ground Water Recharge• The artificial recharge to ground
water aims at augmentation of ground water reservoir by modifying the natural movement of surface water utilizing suitable civil construction techniques.
Artificial recharge techniques normally address to the following issues:
To enhance the sustainability in areas where over-development has depleted the aquifer.
Conservation and storage of excess surface water for future requirements.
To improve the quality of existing ground water through dilution.
Model BillA Bill to regulate and control the Development and Management of Ground Water and matters
connected therewith or incidental thereto.Workflow- Establishment Of A Ground Water Authority Staff Of The Authority Powers To Notify Areas To Regulate And Control The Development And Management
Of Ground Water Grant Of Permit To Extract And Use Ground Water In The Notified Area Registration Of Existing Users In Notified Areas Registration Of User Of New Wells In Non-notified Area Registration Of Drilling Agencies Power To Alter, Amend Or Vary The Terms Of The Permit/ Certificate Of Registration Cancellation Of Permit / Certificate Of Registration Bar To Claim Compensation Delegation Of Powers And Duties
