The only way to know is to perform all the analysis. Deep well water can be very good drinking water.

In Denmark there is no use of surface water at all - we don't like the taste and disinfection byproducts - and our typical wells are in sandy aquifers below a clay layer. They are typically 20-50 m deep and the age of water is 10 to >100 years. All wells are analysed several times a year.

You have to test in laboratory as per international drinking water standard norms ...if passes in all test then it is safe for drinking.

In rural areas this water is used for irrigation and subsequently for drinking,until they notice health disorders never go for lab tests.

It is risky. Deep groundwater can contain fluoride, radionuclides and heavy metals. Toxic effects are not easy to detect, but the damages are chronic. A new water source should always be tested once.

If Deep groundwater can contain fluoride, radionuclides and heavy metals apart from HPLC Method what other easy procedures can perform by rural area.

Certainly not as the salt, fluoride, radiochemicals and heavy metal concentration appears too high and most times show more than 500 ppm TDS. However, such raw water needs to be tested for hardness and other chemical constituents prior to and after treatment (reverse osmosis). The methods for testing include simple lab methods to check the calcium, etc and the best method to check other elements is ICPMS. AAS can also be used with high precession but ICPMS is preferred over AAS for inorganics and for organics again once test with Accu-ToF or GC-MS or LC-MS.

Rural Area : it is the responsibility of government water resources dept . To test the water and also in India cost is only 3 to 10 dollar only per sample , if requested people may get free of cost testing from laboratories from govt as well as public test lab.

ICP-MS can detect most of the likely natural contaminants.

It is also worth to look into problems detected in other wells from the same geological area.

Fluoride can be measured in the field by several colorimetric assays that are very sensitive.

The groundwater from 800 ft well should not be the problem if it meets the drinking water quality standard (EU or WHO or applicable in your country). Yes ICP-MS ccan give answer to most of these. These samples should also be tested for POPs (including pesticides) and Pharmaceuticals to confirm its adherence to safe drinking limits.

800 ft deep well may not necessarily have fossil water? may be it is recharged and is part of an active growundwater system and is not necessarily connate water.

WHO guidelines for Drinking water (physical, chemical and biological characteristics) can be taken and test results of water sample of 800 ft bore well can be compared.

NO, IT IS NOT SAFE is right answer before water analysis.

Novosibirsk large-scale producer of bottled water from artesian well uses for continuous quality control HACH only.

HACH is most authoritative producer of equipment and reagents for water quality analysis - see at http://www.hach.com/water-analysis-handbook-5th-edition/product-downloads?id=7640185976

Dear Andrei Rogoza

Your book much use for water quality researchers

much debate needed for public water suppliers and consumers and sanitary mangers otherwise water contamination leads to public health .

Andrei HACH is not approved for all the analysis. It is a colorimetric spectrophotometric approach and cannot be considered superior to ICP-MS by any means.

SO first time around it should be a detailed and precise analyses and HACH will not be the best approach.

@Saif Uddin

Dear Saif, I have inform about only "..continuous quality control...., HACH is producer.. equipment and reagents for water quality analysis..." It is mean routine, everyday analysis. ICP-MS is not routine analysis (too expensive) - please consult with local drinking water producers, Coca-Cola for example. This procedure is used by sertification of new well.

You are from wealthy Kuwait, it may be ICP-MS is not expensive and is used permanently.

@Mohan

Water can be contaminated in well independent from depth.

Dear Andrei Rogoza and Dr Henrik Andersen

Greeting

Kindly elaborate discussions in depth for benefit to water consumers and researchers

Mr Mohan, thank you for note, I am Dr. but I feel that my qualification is not sufficient - I see downvote for my answer. Dr. Uggin is great specialist in water so he can to consult you professionaly.

My final message - please consult with exploration geologist about yours borehole. Very often, the filter layer above the well is tight, and then the age of the water is hundreds of years - and there is no anthropogenic pollution. But this does not mean that there are no natural contamination. Our Siberian river Ob starts at the Altai, and there are many deposits of of native (natural) mercury and no industry. But water does not have the drink quality in underground.

Dear Andrei the senstivity of the HACH method is not sufficient to determine the water quality assessment. However every country has its own protocols and several countries are using HACH routinely but most of the methods are not WHO or USEPA approved. When this is a new aquifer which has not been tapped earlier a comprehensive assessment fo water quality is to be done. Also 800ft depth doesnot mean that it will be and should be clean. Contaminants are recorded in much deeper aquifers also.

Regarding age of water should not have much to do with quality.

@Mohan You requested elaboration:

I assume like you that such a deep well yields very old water. As the water ages in the ground trivial quality problems like pathogens, nitrate and high DOC tend to be removed by processes in the aquifer. With time the minerals in the aquifer will get in dissolution equilibrium with their constituting ions. In some cases the equilibrium even shift significantly by the high pressure and partial pressure of CO2 in deep aquifers.

I think the most famous case of this in the field of water supply is Bangladesh there in some areas traditional shallow wells are toxicologically safe but challenged by risk of bacteria contaminations, but deeper wells on the same land contains high fluoride concentrations that affect the villagers health.

My requested on elaborations are to create awareness thous who still use borehole water for drinking water source and to companies supply these water in packed bottle and what are probable health hazards in particular to Human and for society in general

Mohan these issues regarding safety of this aquifer can only be discussed when we see the water quality results. If you have these please do share.

Is borehole water is safe for drinking can this companies supply water in packed bottle what are probable health hazards in particular to Human and for society in general

The only way to know is to perform all the analysis. Deep well water can be very good drinking water.

In Denmark there is no use of surface water at all - we don't like the taste and disinfection byproducts - and our typical wells are in sandy aquifers below a clay layer. They are typically 20-50 m deep and the age of water is 10 to >100 years. All wells are analysed several times a year.

Tottally agree with Dr. Henrik Andersen,

The only way to know is to perform a quality analysis.

In Saudi Arabia, some wells are more than this depth and used in agriculture and drinking. Just analyse to for your safety.

the water quality for drinking purpose has nothing to do with depth. you may get brackish water. You have to do chemical analysis and comapre it with WHO standared.

Is that water quality for drinking purpose has nothing to do with depth as per Dr Emad Al-Karablieh

Yes Mohan, put it this way that a depth of 800 ft which is for your well cannot be an assurance that water is safe for drinking. Now if you want to have a detailed discussion then is this well tapping a confined aquifer? where is the recharge zone for thsi aquifer may be it is under agriculture lands (pesticides and herbicides) might reach this aquifer with the irrigation return flow. if it is recharged by a river? then all sorts of pollutants from pharmaceuticals, trace metals etc are possible/probable.

If this is a connate water then bicarbonate concentration could be high, may be TDS, etc.

I would suggest you get the analyses of this well to get more specific answers.

Dear Saif Uddin

This is not one boar hole story,this is the fate of rural areas of all developing countries. My concern is to elaborate discussion for the benefit of unorganized sector farmers and water quality experts

@ Dr. Mohan

Dr. Mohan - is it right? Correct me if not.

I see that "downvote anathema" is disappear, so my next info-drop :-)

I believe, that in such fuzzy situation with drinking water, geological data can help. Thanks to Dr. Andrsen for upvote about "old water", but main point is not time of filtration but history - because industrial and agro-pollution begins ~ since the early fifties, and this water has not yet reached the underground reservoir.

Geological data can also help to in terms of natural contaminants. This does not in any sense may replace an complete chemical analysis, but allows you quickly and in large areas to determine the most suspicious wells.

Groundwater Arsenic Contamination Throughout China.

Science 23 August 2013:

Vol. 341 no. 6148 pp. 866-868

DOI:10.1126/science.1237484

http://www.sciencemag.org/content/341/6148/866.figures-only

Dear Mohan then the basic fact which should be seen is no water is safe for drinking unless a proper analyses is conducted as per WHO or your local country standard. But in practice no one cares, I have seen hundreds and thousand of wells are dug up and bored in aquifers often much shallower and people drink the water without slighest inhibition.

@ Andrei Rogoza

Thanks for your information on Groundwater Arsenic Contamination Throughout China

Thanks to Dr. Andrsen for upvote about "old water", but main point is not time of filtration but history - yes i believe in his opinion.Our effort to built up network to promote clean and safe water to every one and to coserve water for next generation

Regards

Mohan

Dear Mohan, I would like to stress the importance of conducting besides microbiological analyses, which for water at 800ft depth probably will meet the set standards, to carry out also detailed chemical analyses of the groundwater. Regarding the water quality of deep aquifers, my observations are besides As, also Na, Mn, Fe, U or F could be elements of concern. Surely the natural contamination depends on the geological properties of the region.

Best regards

Margriet

Dear Margriet Samwel, Our study area even surface in the water there are traces of pesticide and fluorides.In case along run if these endocrine disturbing chemicals persist what are the prababel digestive/food related problems apart from those already exist.

It is safe. It would also be a good idea to check the quality of water in the area.

Quality need to be determined by analysis. Especially chemical parameters. Then compare the same with WHO standards.

Bacteriological quality is likely to be good as the infiltration of pathogenic and faecal indicator bacteria to a depth of 800ft is rather unlikely. However concentration of dissolved salts and toxic elements may be higher, which has the potential to pose health hazards to the consumer.

It is likely microbiologically safe, but you should do a comprehensive ICP MS analysis to identify the minerals.

Dear Dr. MR Mohan:

I would like to say that I agree with Dr. Andersen, that you must carry out the minerological analysis of the water before determining its potability. Beside the routine analysis for Ca, Mg, Fe etc. other analysis is equally essential. For eg, the table water in different regions of gangetic Delta contains significant quantity of arsenic. However, if you are referring to the table water in a place like Bangalore which is situated on a geological region known as Deccan Trap (which is made up of cooled and condensed volcanic lava) then such contamination will be rare, but it is advisable to check the monerological profile. Microbiological contamination will be a remote possibility due to the high barophilic condition at a depth of 800 ft.

According to my experience in Indus Basin, the groundwater is heterogeneous in quality as well, as it is with respect to aquifer properties. Therefore, variation of groundwater quality is always there, both with depth and areally. The groundwater quality and its variation depends on past and present hydrological, climatic and topographic factors. Also, the present and former positions of stream channels, representing sources of recharge are important. Moreover, differences in the permeability within the alluvial aquifer are the most important.

With this I would like to conclude that 800 ft deep groundwater will certainly be safe from anthropogenic pollution, but the depth can never be an indicator of a good or bad quality, As most of the answers conclude, lab testing is always must.

Dear Dr. Mohan,

Deep well water is generally safer than ground water for drinking but routine water analysis is required for the safety of the water. Following hyperlinks can help you for quality control of the water.

http://water.epa.gov/drink/standardsriskmanagement.cfm

http://water.epa.gov/drink/contaminants/

http://water.epa.gov/lawsregs/rulesregs/sdwa/currentregulations.cfm

http://www.who.int/water_sanitation_health/dwq/en/

http://www.who.int/water_sanitation_health/dwq/gdwq0506.pdf

Please do not forget radioactive, biological and chemical contaminants with the natural, industrial, agro and aero resources.

Dear Dr. Say-yed Hesameddin Tafreshi

Thanks for your information.

Kindly eloberate what are radioactive, biological and chemical contaminants with the natural, industrial, agro and aero resources and their acuurance .

Dear Dr. Mohan,

Geological properties and environmental conditions of the region are very important for decision about the resources of contaminants.

For example, is MtBE added to Gasoline for improvement of octane rating or octane number in your country?

Other examples: Are there Industrial parks, heavy metals, non- heavy metals mines and agricultural lands around the wells? (Sources of toxicological substances, herbicides, pesticides, insecticide and so on).

More explorations are required to compare locations and local properties to come to the conclusions for such situations in other parts of the globe,this discussions are useful to come to conclusions for similar situations

Take bore well water samples in cleaned and dried containers and give for a quality check better to compare with WHO standards for Drinking water before use; The samples should be checked for COD and BOD with in 24 hours; if the water has the accepted levels as compared with WHO standards than use it. The quality check to be done at least once for every 3 months.

Re Dr Doss' comment. It is not likely that there is need to check for chemicals and BOD and COD very frequently if there is no connection to the surface or contamination opportunity. In the US we call it Ground Water Under the Influence of Surface Water. If not then maybe once a year at most for inorganic chemical analysis and more frequently for total coliforms and E.coli. bacteria. Whether you need to check for pesticides more than once is also a question of the potential for contamination from the surface. Those organic chemical analyses are expensive and their utility can be determined based upon circumstances. You should also check Gross Alpha and Gross Beta to determine whether there is any excess natural radioactivity.

it is batter to determine levels of basic parameters such as pH, hardness, TDS and florid. If their levels are above the WHO guidelines better to reject water for drinking. if they are within the guideline then it is better to measure for the all other water quality parameters including heavy metals, and check with the WHO guideline values.

Additional comments: Before doing many testing it is important to estimate the quantity of the water available for the extraction. Also it is important to do a cost benefit analysis before the exaction of water from such deep.

Deep well water is usually free from biological contaminations. Total organic matter is also less.

However, the mineral content cannot be described without performing various tests for inorganic matter. In addition, if the upper layers are depleted, then the water may even contain traces of pesticides, fertilizers and, depending on local soil, soluble inorganic materials like arsenic!

Usually testing is advised periodically, e.g., once a year, for all common contaminants.

Whether water is from shallow or deeper depth is not concerned with drinking water quality. As we go deep, the probability of water - rock interaction become more. Thus disintegration-dissociation -dissolution processes become more with chemical kinetic behavior. For this a detailed chemical analysis is must. Dissolved chemical parameters must be within permissible limits.

Deeper wells may be safe from bacterial contamination, but may pose a threat for heavy metal and other chemical contamination. Various factors like levels of environmental contamination (whether agricultural based or industrial) , soil test results and water quality test results must be strictly within the permissible levels allocated by water quality standards, before utilizing a bore water for consumption.

For that purpose, It's necessary to look the drinking water standards of your country.

240m is certainly deep for a borehole. As previously noted the water should have comparatively low concentrations of organic matter. The two main areas for concern are inorganic contaminants such as heavy metals and salt.

I would certainly advise assessing the water for quality using the local guidelines, and also conduct a draw-down test to confirm recharge rate. It is also good practice to repeat these tests regularly to confirm water quality.

This Q is equivalent to "Is it safe to drive a car at 50 mph? Answer" IT DEPENDS WHERE you are driving or drilling!!!

Though, quality of water of deep aquifers is generally good and people in many parts of India are using water from deep aquifers. However, Water quality should meets should meet WHO guidelines. Ecoli or any other bacterial growth is not observed in deep aquifers due to lack of light and air. Also, it is unlikely that concentrated agricultural pollutants will enter such deeper layers.

It's completely depended on the water qualities (biologically and chemically). Nobody can say water is safe for drinking purpose from any sources, (without testing the qualities).

Hi Seyed,

Refs (Andersen, 2013; Aravinna, 2013; ...Katkov, 2014; Shrivastava, 2014) wouldn't hurt, everybody of us wants to rise our RG factor ;-))

C'mom, gentlemen and gentlewomen, how can we have any precise answer on such a VAGUE question?!! Can that water 800 ft deep be safe? - Yes, certainly. Can that water be unsafe? - It definitely can. IS that water safe? - well, go and check THAT particular sample from THAT particular well ;-))

I am reading this thread and getting a feeling that today is the first of April, not Januray. Nevertheless, happy New Year, dear colleagues! ;-))))

No, quality of drinking water never depends on depth. For drinking purpose free floating oxygenated water with out any contamination is best. Now, your question finds itself that high depth may have presence of metal salts, and other mineral elements in excessive amount. However, deep wells in areas where mining minerals show larger presence is never suitable for drinking purpose. The best example is Arsenic poisoning as well as cadmium poisoning. A good quality water must have physiological level of minerals matter or trace elements, a very slight alkaline pH, low BOD and other purity standards according to W.H.O.

In bangalore natural water recharge in slowly detarorating

http://www.dnaindia.com/bangalore/report-when-lakes-vanish-water-tables-dip-1665297

Depending on the rock types penetrated by the bore, you may want to look beyond the biological and consider issues with radon, heavy metals, fracking or well lubricants, and/or particulates such as chrysotile (asbestos).

Fracking lubricants have tested positively for endocrine disrupting compounds. And I meant to write "upon" and not "on" at the beginning of my previous post.

One must start with a liable test and juge from the first result , considering that safety depends on several factors, either natural or anthropic ones...so with the first result analyses our discussion would be much more interesting...

It could be the best to drink since the soil and rock layers would have acted as a filter bed for the water. However, microbial and heavy metal contamination above allowable limits are possible.

Drinking Borehole water created lots of health problems.In this connection university was organised a three-day international conference, Environment Pollution, Water Conservation and Health, in the city from July 29 to celebrate the centenary year of its Department of Zoology Further M. Ramachandra Mohan, Chairman, Zoology Department, said the department was working closely with the Bruhat Bangalore Mahanagara Palike and the Bangalore Development Authority to preserve lakes in the city by suggesting measures to prevent water contamination..

Over 1,000 delegates were participate in the conference , held on the Central College campus. The Department will try to publish a policy and vision document on issues concerning environment, biodiversity and health at the end of the conference

In this process opinions from global scientests are welcome to improve water quality

http://www.thehindu.com/news/national/karnataka/drop-400-borewells-plan-vc-urges-mayor/article538202.ece

Water from deep down 800 foot is really risky unless it is properly analyzed for heavy metals, radiometals and other daingerous organics too. Water from such deep has been often and often proved to be risky.

With out analysis of that particular bore well water we cannot conclude whether it is safe or not. because ground water can be polluted by various factors such as chemical contaminants (Fertilizers, Herbicides, Pesticides, Heavy metals etc.. ) and several pathogenic microorganisms. so better you can analysis your bore well water if it is taken from 800 ft before you consume it.

Radiometals and other daingerous organics too-eloberate

Radionucleides, Pb, Cr, Ar, Nitrates and besides this Selinium III found in ground water

http://srwqis.tamu.edu/florida/program-information/florida-target-themes/drinking-water-and-human-health.aspx

http://pubs.usgs.gov/wri/wri004273/pdf/wri004273.pdf

http://pa.water.usgs.gov/reports/fs012-00.html

Kindly eloberate probabel levels of Radionucleides, Pb, Cr, Ar, Nitrates and besides this Selinium III found in ground water

It depends to following factors:

1-Type of aquifer (Alluvium or Karst)

2- Time travel that controls the age

2-The hydro-chemical and radioactivity characteristics of water

3- The temperature and other physical characteristics of water

Water experts know that for every water supply abstraction technology, a lot goes in to ensure water gets to be consumed. Therefore, it is critical to subject water abstracted through any means to analysis which of course has been the usual practice. In this very case, its good to extend the analysis to other parameters like the heavy metals and ions which may constitute harm when consumed.

There is no relation between depth of water and its drinking water suitability. Quality of water for drinking purpose depend upon the chemical constituents dissolved in it.All the ionic species must be within the permissible limit of drinking water. Periodic monitoring and chemical analysis is very much required.

@Virendra Saxena Explains There is no relation between depth of water and its drinking water suitability- need to be discussion

Wow, discussion when everybody says practically the same is still alive and active!

Thanks Igor.

Ramachandra, Deapth of bore well is not important. Important is water suitability for drinking. This is depend on dissolved constituents must be in permissible limits of drinking water.

Nice! 13 days after my sarcastic comment we have one more THE SAME and obvious answer; thus, this WELL will never dry ;-))

Igor, Hope fully now the bore well is dried. Appreciate your comments.

Dear Scientists Thanks for your contribution for my question,which will show some lite on bore hole drinking water quality.Further the governance of drilling in dangers places and locations are to strictly prohibited,other wise a common and innocent peoples are suffer from all the valued suggestions made by eminent scientists in this discussions are no valve .

Further any new developments and interesting aspects regarding drinkable water quality in any other country. I also want to emphasize to create awareness amongst developing country. I further extended this aspect that science is not a stagnant.

Yes...depth doesn't matter.

Thanks Lijo.

"Yes...depth doesn't matter"

".t depends on the result of analysis of the water samples!!!!!!!!!!!

Isn't THATALL obvious????????????????????????????????

I am outta here!

Patience, all. Apparently Ramachandra needs some ammunition to make an argument that testing to confirm water quality is necessary no matter the depth of the well. High and low quality waters can be found at nearly any depth, depending on where one drills, and what has occurred before and what occurs after drilling is completed. Not only is testing necessary to confirm water quality in a newly drilled well is safe, but it is also necessary to periodically retest that water to confirm the quality has not been degraded, especially if there are human activities (e.g., waste disposal facilities) or natural phenomena (e.g., seismic activity) that could affect groundwater quality.

Someobody's upgraded my Reserach Gate score: ME as I agree with what Bryce and many others here that have said essentially the same: size, pardonme, depth doesn't matter but the quality tests do; applicable not only for that type of drills ;-))

Normally deep well water is good for drinking purposes. Some quality parameters are varied depends on the geographical distribution of soil strata.

As a whole it can be confirmed after total analyses of water sample.

Thanks a lot.

Soil will filter water from rain, so cleaner water might be found deeper under the Earth surface because of filtering effects. The is probably not the case for ice which is just piling up year after year. Is 800 ft deep ice safer for drinking purpose than ice at the surface (e.g. Antarctic versus Arctic)? Does pollution-free rainfall still exist?

Generalizations that deeper water is safer water is inherently risky.

C'mon fellas, this is coming to circles, and what is the definition of insanity?!

My last words here: assuming a simple model, the concentration of a prticular i-th filtrable component at depth h can be expressed (SIMPLIFIED MODEL) as following:

Ci(h) - Ci(0( x exp (-h/hc,i),

where hc is the charecteristic depth, at which Ci drops in e times.

.

We have THREE parameters here: initial concentration of the particular i-th component, Ci(0), flitration ability to this component(1/hc,i), and FINALLY, the actuay depth h. And all 3 parameters are different for different chemicals, for different places on the global surface, and (at some extent) at different time. SO, any general statement that drilling deeper is safer would be flatly WRONG. Some people forgot the 7-th grade Physics here! In reality, the model is even more complaex, and many parameters are unknown. CONCLUSION: only the chemical probe analysis can give the answer about safety, it's too much at stake!

Evidently, there is the quality of the water that you can measure directly with focused chemistry-based research, and the multiple origins of the quality of the water that can be studied with trans-disciplinary research practices (landscape management, quality of rain fall and their origins, geology, soil chemistry, soil physics, etc etc).

Marcel, you lost me. What did you mean by "... the quality of water that can be studied with trans-disciplinary research practices"? How is that quality of water different from water quaiity as indicated by measuring relevant chemical and physical properties?

It really seems to me that since the question has been published, our colleague must have undrestood that analysis of the water, must be undertaken...I hope that he will communicate the results and some comparisons and explanations could be more productful between all of those who are intersted by the matter...

Igor Katkov · 32.24 · 82.02

"My last words here: assuming a simple model, the concentration..."

The fundamental problem with your model is that quality of the water at the surface level is unknown and you are treating water as a chemically inert liquid. For example, is there a layer containing arsenic at some depth, the water containing dissolved oxygen will rapidly leach arsenic from the rock. The water at the surface could have been perhaps much better.

Your model is not realistic.

It is not the depth of the well which determines the quality of water, but the location of the well. To get a good quality of water, the well must be away from industrial activity, city area as well as away from seashore. The hotwater springs also play a role in altering the quality of water.

But how do you handle air pollution contaminating rain and transported over long distances

If there were reliable predictors of the location of good ground water (quality and well yield), then drilling productive wells would not be a challenge, which seems to conflict with experience. Is it not often the case that multiple attempted wells have to be drilled to find a location and depth that is of both adequate quality and volume? There simply is no reliable single predictor, neither location or depth, that assures a well will produce good water. Further, there is no geological or other reason to expect there to be such a single predictor. Finding the location for a productive well can be aided by science, but success often depends on actually drilling wells. When a productive well (location, depth) is found, the quality of the water should still be regarded as unknown until it is confirmed by appropriate testing. Only then should that well be put into use for human consumption, agriculture, or other purposes. At least when human health is concerned, water quality should not be assumed based on well depth or location. If one ponders this issue, one can reason that in the past surface waters in some, but not all, parts of the world were safe for human consumption until human impacts reduced water quality. The apparent principle applies for groundwater as well.

Well generally The deeper, the better..but there are some other factors because safe drinking water is a result of understanding how a well interacts with your local land use patterns, geology, well construction techniques and regular sampling and testing.

"Well generally The deeper, the better" is good response. But, goodness of water depends on geochemistry of aquifers. If you strike salt rich aquifer deep down, it will be difficult to drink it, for example. It may be case for any deep down chemicals in the upper layer of the Earth. It cannot be said with certainty that deep boring will bring in good water as Henrik pointed out "The only way to know is to perform all the analysis."

@Mohammad: The same holds for passed layers with iron.

Does air pollution contaminants are able to reach geochemistry of aquifers

Exactly, Mohammad and Hanno. As far as geological layer chemistry affecting water to your list of salt and iron, add at least arsenic, uranium/radium series, selenium,

Ramachandra,

Why would one assume air pollutants would not reach, or indirectly affect groundwater quality. Acid rain, for example, can substantially alter surface water, which depending on location, is the source of groundwater. The geology of some areas will provide a purification effect as water percolates to depth, but that effect has a capacity limit that varies by geologic materials, and subsurface structure and water percolation pathways, among, I am confident, other factors as well. Natural systems providing ecological services all have limits. When those limits are exceeded, contamination or other such impacts will occur. Challenging that capacity is inadvisable unless one has very reliable knowledge of what the limit is, which is difficult in the first place and more so when the externals, like climate, are changing in unforeseeable ways at unforeseeable rates with unforeseeable impacts on the system of concern.