In agricultural areas, groundwater nitrate levels can be much higher than the drinking water standard, e.g. North China Plain. It seems that a holistic approach is required to solve this problem. What is the best practice to remediate and prevent such pollutants or pollution?
To reduce nitrate pollution of groundwater the best solution is to immediately reduce by half the amount of fertilizer in the watershed upstream of the wellfield and verify the evolution in time. This is a long operation (several years) depending on the hydraulic characteristics of the aquifer underground. Modeling of flow and transport of nitrate can be successfully estimate for the rehabilitation of the water quality.
It is also possible to involve ion negative exchange techniques on organic resins if the volumes to be treated are not too important.
Many thanks to Mania for the answer. It is very reasonable. However, if the farmers refuse to do so for the sake of ensuring food production, what can be done?
We´re testing bioremediation using eucaliptus on the downstream area with good results. The next step is testing native trees.
Phytoremediation and constructed wetlands remedies have been used to address nitrate concentrations in groundwater.
Thanks Barbara for the answer. Wetlands, including constructed, can be very effective in nitrate remiediation. Could you provide cases or references of success stories in the case of groundwater?
Solutions must come from implementation of best management practices first but during the time lag phase implementation of engineered solutions eg denitrifying bio reactors ( but in a holistic fashion) may be avoid start. Wetlands also.
Thanks, Owen. Prevention is better than treatment. So I agree with you that best mangement practice should be in place. Role of governments is essential.
Well, based on my experiences working in the field, reducing excessive nitrate requires mutliple solutions ranging from good farm management strategies, innovative farm irrigation schemes, careful design of farms in relation to land geomorphology & geology, to educating the farmers to use biofertilizers instead of synthetic fertilizers. In addition, a selective planting strategy of plant species that can mop up these nutrients will also be useful if constructed wetlands form part of this nitrate reduction strategy: https://www.researchgate.net/publication/235873867_A_SELECTION_OF_PLANTS_FOR_GREENING_OF_WATERWAYS_AND_WATERBODIES_IN_THE_TROPICS?ev=prf_pub
Book A SELECTION OF PLANTS FOR GREENING OF WATERWAYS AND WATERBOD...
Hello, see a conference part on the evolution of nitrate concentration in time in the alluvial Rhine deposits , Alsace Region in France
Environmental Geology (2009) 57 : 1579-18592
Impact of fertilizer application and urban wastes on the quality of groundwater in the CAMBRAI halk aquifer , Northern France
by Hani SERHAL et al.
Environmental Geology (2009) 57 : 1579-1592
Impact of fertilizer application and urban wastes on the quality of groundwater in the CAMBRAI halk aquifer , Northern France
by Hani SERHAL et al.
I think the first step is to encourage the use of other types of fertilizers among farmers to discontinue the sustained recharge of groundwater with nitrates. Since nitrates are nutrients, with time groundwater will recover through the help of natural microbial activity.
Sir --
As an attorney, I have little direct knowledge upon which to draw in order to provide you with an answer. However, I know people who are very familiar with the nitrate overloading issue. One of them, Karl Czymmek of Cornell University (), provides you with an answer and is very willing to discuss the matter further with you. (Karl works on New York State's Nutrient Management SPEAR program, the research of which serving as the basis for the New York State Environmental Conservation Department's technical standards that address nitrogen applications and protection of groundwater.) What follows is my question to him and his response. Hopefully, this helps:
Charles, there are many facets to your excellent questions. You can forward my contact information to your colleague. Most of my work has focused on beneficial practices that can be implemented to reduce loading. Success here necessarily depends on behavioral change at the farmer level and this is an area where practical knowledge, science and psychology interface. We have had quite good success with this in New York State. Most N is taken up by most plants in the nitrate form. The quandary is based mainly on these two facts: Nitrate is required in fairly high amounts by many crops, and it is water soluble. So optimal plant uptake requires it to be in a plant available, water soluble form, but this is also the most vulnerable to environmental loss, and in an effort to avoid underfertilization, may be over applied. In my view, avoidance of over application is much more practical and cost effective than treatment, and in any case, should be part of a broad solution. My approach in NYS has been to look for conditions where farms can reduce inputs while maintaining high yields, and then demonstrate these to producers in ways they can accept. There are many suitable practices, for both N and P. Beneficial practices vary somewhat by system (crop type, manure, fertilizer, etc) but are fairly well known. Education and outreach, in the right way, is critical for successful adoption. Hope this helps. Let me know if you have additional questions.
Karl Czymmek
Sent from my iPad
On May 29, 2013, at 10:37 AM, "Sullivan, Charles" wrote:
Hello!
A friend of mine at NYSDEC referred me to you as the expert to write to on the subject topic.
I am a member of a research group that discusses a wide variety of topics. One topic that arose, from a Chinese researcher, is, how to address nitrate contamination of groundwater. This is a major issue in northern China, where the farmers have resisted efforts to have them stop overnitrating their crops.
The question, then, is what is the best way to address nitrate groundwater contamination? While I expect that there's no single "magic bullet," there may be a list of actions that you have devised over time that I could share. For example,
-- are there effective substitute fertilizers to nitrates that would provide the benefits of nitrate application to foodcrops but that, if overapplied, would not harm groundwater and surface water quality?
-- are there foodcrops/foodcrop strains that require a higher than typical nitrate application so that the Chinese government could provide seed for those crops/strains to substitute for the seed the farmers are now using (the idea being that the farmers would continue overnitrating the soil but not increase the overnitration)?
-- are there specific "best farming practices" that could be implemented that reduce invasion of nitrates into the groundwater? For example, since I expect that nitrate intrusion probably is a function not only of the quantity of nitrate applied but also how much water is applied to the soil in the form of rain, irrigation, etc.; so, I wonder whether the answer to this is whether there are limits to how much water should be applied to the land so that the plants get all the water they need to grow but not so much as to allow water not used by the plants to travel down the soil column and into the water table while carrying excess nitrates with the percolation?
-- are there specific farming practices that could be implemented that could reduce dependency on nitrate fertilizers without crop yield reductions?
-- would the Chinese government's simply rationing nitrate fertilizer be a part of the solution?
-- are there examples of successful groundwater nitrate contamination reduction/elimination that could be cited to the Chinese researcher? Ditto for successful surface water contamination reduction/elimination? What are they; and what was the bundle of strategies that were used to achieve the objectives?
Finally, would it be okay for me to refer the Chinese researcher to you for followup?
It is 100% true that the requirements of limited doses of fertilizers
in these protection areas are effective on groundwater in long-term also enhancement of nitrobacter bacteria in the soil are able to reduce nitrate in ground water.
Awareness should be created among farmers for application of fertilizer and manure in relation to essential requirements of the crop taking into account the available nitrogen in the soil.Moreover,Nitrogen depletion and increase of crop yield in agricultural soils can be achieved by rotating crops from year to year. For example, Soybeans (a legume) which fix nitrogen may be rotated with corn, which does not improve soil fertility. The Soybeans will enrich the soil with nitrogen for the corn..In short,according my opinion,above mentioned practices can help in minimizing Nitrate Pollution due to fertilizers.
I will add a new dimension to the discussion. In Sri Lanka, I should say that we have failed miserably in convincing the farmers. While we have serious cases of excessive fertilizer use and nitrate pollution, fertilizer subsidy is being given to the farmers by the Government for political reason. Therefore, I believe that the solution should be advocated at policy level, with genuine interest on the wellbeing of the people.
Removal of fertilizer subsidy, awareness creation on best practices, introduction of sprinkler / drip irrigation to reduce the transport by reducing excessive water application, etc. are some policy options.
In my opinion, bio-remediation has limited scope at regional level. However, individual wells can be remediated for drinking purposes. We achieved success in it to certain extent. Please see the references below.
https://www.researchgate.net/publication/237020751_Bioremediation_of_nitrates_in_groundwater?ev=prf_pub
https://www.researchgate.net/publication/237020677_Restoration_of_the_riparian_zone_of_lake_Richmond_through_landcare?ev=prf_pub
Article Bioremediation of nitrates in groundwater
Article Restoration of the riparian zone of lake Richmond through landcare
I also endorse what Patmarajah mentioned
We can thing of going to bio fertilizer to solve the nitrate problem
I have some doubt about the nitrate levels and fertilizers usage. earlier we made one study between the agriculture lands and village environs vs nitrate concentration in groundwater (Env. Monit. assessment v. 64 pages 481-492) and found that more NO3 conc. is in the village environs. Now I am looking another data set were we worked 3 years and very high agriculture activity, the same result we have seen (but in both the cases there is no paddy cultivation). Hence I feel that we may be blaming the farmers unnecessarily. when village environs have high NO3, even bio-fertiliser may have the same problem. this is my opinion.
Studies in Sri Lanka has clearly indicated nitrate pollution in groundwater is related to agriculture. However, paddy cultivation is not the major contributor. It is the vegetable and other field crop cultivation that contribute the most. I agree with Reddy in that it is not always inorganic fertilizer; even organic fertilizer can contribute, cow dung for example.
Excessive irrigation or heavy rainfall carries nitrate to groundwater. Else. there is no risk.
Studies conducted in In India and Pakistan proved that N-fertilizers and inadequate sewerage system are major root of nitrate leaching towards groundwater,Awareness among farmers is need of the time which force them for balanced use of fertizers. Uptake by crops should be kept in mind while application
Nitrobacter is a genus of mostly rod-shaped, gram-negative, and chemoautotrophic bacteria. Nitrobacter plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil. Unlike plants, where electron transfer in photosynthesis provides the energy for carbon fixation, Nitrobacter use energy from the oxidation of nitrite ions, NO2-, into nitrate ions, NO3- to fulfill their energy needs. Nitrobacter fixes carbon-dioxide (via Calvin cycle) for their carbon requirements. Nitrobacter have an optimum pH between 7.3 and 7.5, and will die in temperatures exceeding 120°F (49°C) or below 32°F (0°C). Some sources regard Nitrobacteraceae to be the family of the genus Nitrobacter. Species in the genus Nitrobacter include Nitrobacter winogradskyi, Nitrobacter hamburgensis, Nitrobacter vulgaris and Nitrobacter alkalicus. Nitrobacter belongs to the α-subclass of the Proteobacteria. Nitrobacter may either be rod shaped, pear-shaped or pleomorphic. Cells normally reproduce by budding . Carboxysomes which aid carbon fixation are found in lithoautotrophically and mixotrophically grown cells. Additional energy conserving inclusions are PHB granules and polyphosphates. When both nitrite and organic substances are present, cells can exhibit biphasic growth, first the nitrite is used and after a lag phase, organic matter is oxidized. Chemoorganotrophic growth is slow and unbalanced thus more poly-β- hydroxybutyrate granules are seen that distort the shape and size of the cells.
Nitrobacter play an essential role in aquaponics. Nitrosomonas bacteria first convert ammonia into nitrites. Nitrobacter convert the nitrites into nitrates, which are readily absorbed by the plants.
A group of bacteria that reduce nitrates or nitrites to nitrogen-containing gases. Potential examples includeThiobacillus denitrificans, Micrococcus denitrificans, Paracoccus denitrificans and Pseudomonas. This is important as it allows nitrogen to be recycled back into the atmosphere.
Denitrifying bacteria form a necessary part of the process known as denitrification as part of the nitrogen cycle, their primary purpose being to metabolise nitrogenous compounds, with the assistance of the nitrate reductase enzyme, to turn oxides back to nitrogen gas or nitrous oxides for energy generation. This process takes place only in the absence of oxygen, as most denitrifying bacteria are facultative aerobes (prefers to use oxygen as their terminal electron acceptors), however, they could also utilize nitrate instead. Therefore, denitrification can only be performed under anaerobic conditions. This is the main reason why denitrification mostly occurs in the deep substrata of the soil, or in areas of stagnant water.
The process of denitrification lowers the fertility of the soil and thus is less common in areas where the land is rather well-cultivated. But this loss of nitrogen to the atmosphere can eventually be regained via introduced food and water, as part of the nitrogen cycle. Some nitrogen may also be fixated by species of nitrifying bacteria and the cyanobacteria.
Denitrification also becomes the key pathway for dissimilative nitrate reduction, which is the process in which nitrates are reduced from the soil, the former being highly toxic for living organisms. Denitrification tends to produce large amounts of by-products.
The most common denitrification process is basically outlined below, with the nitrogen oxides being converted back to gaseous nitrogen (as opposed to that of nitrifying bacteria):
2 NO3- + 10 e- + 12 H+ → N2 + 6 H2O
As can be seen, the result is one molecule of nitrogen (consisting of two atoms) and six molecules of water.
Denitrifying bacteria themselves include several species of pseudomonas, alkaligenes and bacillus. By their activity the losses of nitrogen into the atmosphere is roughly balanced by that which is released into the soil by nitrifying bacteria, forming a relatively balanced cycle.
Please check out the recent publications from the 2013 Darcy Lecturer, Prof. David Rudolf (University of Waterloo), whose Darcy Lecture is on this topic, namely Managing Groundwater Beneath the Agricultural Landscape.
His talk covers ten years of research focusing on the performance of local/regional-scale "beneficial management practices (BMPs) designed to reduce nutrient loading to the subsurface in the vicinity of an impacted municipal groundwater supply system". I work with pesticides primiarly, but saw his talk at the Groundwater Quality 2013 conference in 2013 and found that his ideas were fantastic, i.e. combining BMPs to reduce the amount of fertlizer used coupled with active remediation to meet water quality guidelines in the short-term. It's worth checking out in any case.
There is a recent Science Special Issue (August 2013) on pesticides, but I find a solution used in Vietnam may apply also to your case in Sri Lanka. Scientists challenged farmers to try an alternative BMP, after spending years trying to convince them of the benefits of reducing pesticide use. So if you can offer an alternative BMP, perhaps similar to the ideas published by Dr. Rudolph, you can convince them to give it a try too. But you are probably correct, that such initiatives may need to be supported from the policy perspective.
Absolutely, and sorry for not adding it to my comment earlier!
http://www.ngwa.org/foundation/darcy/pages/default.aspx
A massive conversion of conventional agricultural systems to organic farming may help reducing the net flux of nitrate from land to aquatic ecosystems and groundwater.
Agree, a major switch to organic fertilizers is indeed very important to reduce the levels of inorganic N enter the waterways. Here in Singapore, we are pilot-testing the use of fast-growing floaters (water hyacinth, water grass) to abosrb the nutrients (mainly N and P) in our waterways.
In addition, we are also pilot-testing the use of terrestrial plants, grown on floating mats, in order to absorb the nutrients (mainly N and P) in our lakes and reservoirs.
Improving nitrogen use efficiency while applying to the agricultural fields is very important to reduce the leaching of N residues that contaminate the groundwater. This will reduce the overuse of N fertiliser to provide optimal dosage to the crops beside input cost reduction to the farmers.
One of my co author Jannen Sivakumar uploaded two articles in RG regarding this. These will be useful to you pl
https://www.researchgate.net/publication/255949240_IMPROVE_QUALITY_OF_BRACKISH_WATER_THROUGH_BIOFILTER_SYSTEM_COMBINE_WITH_CLAY_AND_WASTE_POLYTHENE_LINER
https://www.researchgate.net/publication/255963096_DEVELOPMENT_OF_A_BIOFILTER_SYSTEM_FOR_IMPROVING_QUALITY_OF_BRACKISH_WATER?ev=prf_pub
Conference Paper IMPROVE QUALITY OF BRACKISH WATER THROUGH BIOFILTER SYSTEM C...
Thesis DEVELOPMENT OF A BIOFILTER SYSTEM FOR IMPROVING QUALITY OF B...
We are finding in the Eastern United States that planting a winter cover crop is one of the most effective ways to take up excess nitrate before it reaches the water table.
Loads of mitigation options check out
Cost869 website wim Chardon.
Also denitrifying bioreactors help
The majority of nitrate contamination in groundwater is derived from agricultural fertilizer (potassium nitrate and ammonium nitrate) (main) or from manure storages or septic system failure. Nitrates, which are very soluble and donot bind in soils can easily be leached out to groundwater. There is a need to reduce leaching of nitrates since nitrate contamination of groundwater may cause incidence like methemoglobinemia or blue baby syndrome. In addition, nitrogen based fertiliser, is one of the greenhouse gases having high global warming of potential. Excess nitrogen can also cause eutrophication in surface water. An improved agricultural practices such as adjustment of application rate, application of the right amount of nitrogen, use of slow controlled release fertiliser, applying nitrogen fertilisers when least susceptible to loss, crop rotation, avoiding over-irrigation and storage of manure in concrete pits lagoons can be helpful to prevent nitrogen pollution in groundwater and surface water and climate change mitigation.
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