Nitrate Levels In Groundwater Research Articles

Assessment of nitrogen application limits in agro-livestock farming areas using quantile regression between nitrogen loadings and groundwater nitrate levels

The excessive application of nitrogen in agro-livestock farming areas has led to serious groundwater contamination around the world; thus, the efficient control of N loads is crucial to manage nitrate contamination of groundwater. In this study, to suggest an optimal N application limit as a key guideline of N management, we examine the impact of anthropogenic N loading on nitrate levels of shallow groundwater, using a large dataset (n = 4,000) collected in 2012–2014 from 100 agro-livestock farming districts in South Korea. Not considering the time lag and legacy problem, quantile regression is performed to overall assess the relationship between nitrate contamination and anthropogenic N input across the full range of conditional distribution of groundwater nitrate concentrations because of heteroscedasticity. As a result, positive gradients (βτ) meaning the rates of changes are found between groundwater nitrate concentrations and land-derived N loads at all quantiles; βτ increases as the quantile is higher and is as large as 36.48 ± 10.73 mg NO3−/L per land-derived N input (on a log scale) at the 90% quantile. The quantile map indicates that the high gradient (i.e., the large sensitivity to N loading) is related to agricultural land use, low elevation, and low topographic slopes. In fact, groundwater nitrate concentrations increase as the percentage of agricultural land increases but the percentage of forest, elevation and slope angle decreases, which suggests that land use, elevation, and slope should be considered when attempting to evaluate N application limits. This study suggests the N limits below 170 kg ha-1 year-1 based on the drinking water standard (44.3 mg/L as NO3−) at the quantiles higher than 70% which mostly occur in flat agricultural lowland areas. Our method used in this study can be applied elsewhere to establish efficient management practices for groundwater nitrate contamination, considering local environmental factors.

Irrigation and Nitrogen Fertilizer Rate Impacts on Soil Nitrate in Potato Production

ABSTRACTParts of the Kern County have high nitrate levels in groundwater. A State Water Resources Control Board commissioned report has indicated that crop land agriculture is the main source of nitrates in the groundwater. Annual rainfall is less than 20 cm, thus irrigation is necessary for optimum crop production. A project was undertaken to evaluate current nitrogen fertility and irrigation scheduling in potato production and their contribution, or lack thereof, to nitrate movement in the soil profile and potential nitrate contamination of groundwater. A line-source sprinkler plot area was established to create soil moisture regimes of 120% of target, target (optimum soil moisture for potato growth) and 80% of target. Pre-plant and post-harvest soil samples were collected to a depth of 2 meters. Plant, root and tuber samples were collected and analyzed for nitrogen content. Soil moisture and irrigation amounts were monitored. Plant dry matter and tuber yield increased with each N rate increase. The high N rate increased plant growth disproportionally to the increased tuber yield. Appropriate irrigation scheduling did not produce water movement beyond the effective potato rooting zone. Excessive irrigation moved soil nitrate deeper into the soil profile.

Source characterization and human health risk assessment of nitrate in groundwater of middle Gangetic Plain, India

Nitrate ( $$ {\mathrm{NO}}_3^{-} $$ ) pollution is a global concern as it affects the whole ecosystem: human, livestock, economy, and environment. The elevated levels of nitrate in groundwater can directly pose risks to population. A total of 156 representative groundwater samples were collected from groundwater sources such as hand pumps and bore wells across the study area. To identify the source of nitrate with its associated attributes, multivariate statistical methods (factor analysis (FA), sparse principal component analysis (SPCA)) were used in this study. In addition, empirical Bayesian kriging (EBK) modeling was used to predict the nitrate at ungauged locations of the study area. From the analysis of results, it was found that 5% of the groundwater samples exceeded the acceptable limit (50 mg l−1) of nitrate as specified by the World Health Organization (WHO). The first principal component (PC) indicated by the SPCA was salinity factor, which was significantly contributed by electrical conductivity followed by sulfate. The fourth PC represented the nitrate as a factor and positive loading of nitrate was strongly associated with chloride, sulfate, and calcium. The associated loading of nitrate with water quality attributes indicated that elevated level of nitrate in groundwater may be due to external sources that came through anthropogenic activity. A similar conclusion was drawn from factor analysis as well, indicating that SPCA can be applied as a new method for groundwater geochemistry. Hazard index calculations showed that infants of the study region were at a higher risk compared to the adults and children.

Spatial distribution, exposure, and potential health risk assessment from nitrate in drinking water from semi-arid region of South India

Elevated nitrate concentration in groundwater is a worldwide problem. Continuous exposure to high levels of nitrate in groundwater may cause adverse health effects among residents who use groundwater for consumption. Therefore, this study was conducted to identify the nitrate distribution and its potential health risk assessment from semi-arid region of Peddavagu in Central Telangana (PCT), South India. Groundwater samples were collected from thirty five locations and analyzed for nitrate and other water quality parameters. Nitrate (NO3-) in groundwater was observed to vary from 17 to 120 mg/L, with a mean of 58.74 mg/L. About 57% of samples exceeded the maximum acceptable limit of Indian drinking water standard. About, 40% of groundwater samples drinking water quality index (DWQI) is good, while 60% of groundwater falls in poor quality for drinking purposes. Health risk maps were created based on hazard quotient to quantify the potential health risk of the residents using US Environmental Protection Agency (US EPA) health risk assessment model. Health risk assessment revealed that mean total hazard index (HItotal) for men, women, and children were found as 1.42E + 00, 1.67E + 00, and 1.95E + 00, respectively. Results exhibited that children are at high health risk than men and women in the PCT. Further, the human exposure to the NO3- contaminated water was above the critical limit of non-carcinogenic risk.

Adapting the EPIK method to Brazilian Hydro(geo)logical context of the São Miguel watershed to assess karstic aquifer vulnerability to contamination

Karst aquifers are, besides important strategic reservoirs of good quality water, heterogeneous and anisotropic, where highly permeable karst networks result in insufficient time for contaminant degradations, and hence the quasi-immediate contamination of the aquifer. The EPIK method is a low-cost technique and was developed to map karst regions based on four main feature indexes: 1) epikarst; 2) protective cover; 3) infiltration conditions; and 4) karst network development. However, the method was developed according to European hydrogeologic and temperate climatic contexts, where its application without adaptations in regions in different contexts may result in possible misunderstandings, such as overlook, underestimate or overestimate significances of some parameters (e.g. soil covers, rainfall regimes, morphological domains). The Brazilian São Miguel watershed, a tropical karst region where the city of Pains is located (southwestern Minas Gerais), is characterized by high levels of thermotolerant coliforms, phosphorus, nitrate, and cadmium in surface water and groundwater. These contaminants come from, agriculture, livestock, and urban areas. Due to these issues and to provide a tool of water resource management and land use planning, the EPIK method was adapted to the hydrogeologic reality of the São Miguel watershed, considering both local vegetation and the current Brazilian speleological heritage protection legislation. Results revealed that 52% of the area has moderate vulnerability and 7% high vulnerability, this latter one concentrated in areas close to mining activities and urban areas. The study provided a reliable map and adapted technique which can be used in other Brazilian karst regions and other tropical karst regions.

Nitrate contamination and subsequent hydrogeochemical processes of shallow groundwater in agro-livestock farming districts in South Korea

In last several decades, the nitrogen cycle has been significantly perturbed, largely due to intensification of agricultural activities throughout the world. In this study, we examined the impact of agricultural N inputs on the quality and chemistry of shallow groundwater, based on a large hydrochemical dataset (n ≈ 4000) collected from 100 agro-livestock farming districts in South Korea. The South Korean groundwater, studied mostly in silicate aquifers, shows very high nitrate concentrations (median NO3− = 22.2 mg/L) and acidification (median pH = 5.6). The groundwater nitrate levels tend to increase with the estimated N loadings, and the groundwater pH generally decreases with increasing nitrate levels. The relationship between the concentrations of Ca2+ + Mg2+ and HCO3- has a moderate adjusted R2 value (0.4), and the molar (Ca2+ + Mg2+) / HCO3- ratios (r) tend to increase with nitrate concentrations. This implies that the chemical composition of the groundwater is controlled by multiple hydrogeochemical processes, which include weathering of silicates and carbonates induced by carbonic acid (r = 0.5), nitrification (r ≥ 1) and denitrification (mostly, r < 0.5 in this study). In particular, undrinkable (NO3− > 44.3 mg/L) groundwater (n = 988) shows an average molar ratio of 1.04, indicating that such highly contaminated groundwater experiences the enhanced geochemical weathering of aquifer materials by an anthropogenic process (e.g., addition of N fertilizers). The results of principal component (PC) analysis also support our explanation: the first PC shows significant negative correlations with major components including NO3− while there is a weak positive correlation with pH, indicating anthropogenically enhanced weathering that includes the buffering process by agricultural liming materials, while the second PC shows negative correlations with Eh, DO and NO3− but positive correlations with pH and HCO3−, suggesting the denitrification process. A few groundwater samples (about 4%) experienced heterotrophic denitrification, and they have molar ratios (r) of less than 0.5. The results of this study indicate that 1) geochemical weathering of aquifer materials in shallow groundwater systems is enhanced by nitrate contamination caused by high N loadings in agro-livestock farming districts, causing increased salinity, and 2) in silicate aquifers, the prevailing hydrochemical process can be interpreted by the molar (Ca2+ + Mg2+) / HCO3- ratios of groundwater.

Subacute intoxication with sodium nitrate induces hematological and biochemical alterations and liver injury in male Wistar rats

Nitrate pollution has emerged as a problem of great importance because in recent years, the levels of nitrate in soil and groundwater have increased, mainly through anthropogenic activities, such as the use of fertilizers in agriculture, domestic wastewater and septic tanks, industrial waste and deforestation. In animals, nitrate reduction to nitrite (NO2) and nitric oxide (NO) promote the formation of methemoglobin in the blood and the generation of highly reactive intermediates that induce oxidative stress in target organs. Exposition to nitrates has been associated with methemoglobinemia, reproductive toxicity, metabolic and endocrine alterations and cancer. This study analyzed acute intoxication with sodium nitrate (NaNO3) in male Wistar rats, aged 12–16 weeks. Four groups with n = 10 rats each were formed: group 1 was the control, and group 2, group 3 and group 4 were treated for 10 days with intragastric doses of 19, 66 and 150 mg/kg/d NaNO3, respectively. Hematological, metabolic and histological biomarkers in the liver were analyzed. The results showed high percentages of methemoglobin, an increase in NO2 in the plasma and an accumulation in the liver. Moreover, there were high counts of white blood cells and platelets in all treated groups. Additionally, there was an increase in the spleen weight in group 4. High levels of glucose, triglycerides, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were observed and were significantly increased in groups 3 and 4. For oxidative stress biomarkers, there were increases in Thiobarbituric Acid Reactive Substances (TBARS), total GSH and SOD activity, mainly in group 4. Changes in mitochondrial activity were not significant. Histopathological analyses of the liver showed inflammation, infiltration of mononuclear cells, steatosis, ischemia and necrosis, and these findings were more evident at high doses of NaNO3 in which high of S-nitrosylation were found. In conclusion, NaNO3 was reduced to NO2, thereby inducing methemoglobinemia, whereas other reactive species generated oxidative stress, causing hematological and metabolic alterations and injury to the liver.

Teor de nitrato em águas subterrâneas da região metropolitana de Fortaleza, Ceará: um Alerta

Diante do quadro de escassez hídrica em regiões de clima semiárido como é o caso do Estado do Ceará, a exploração de água subterrânea é uma importante medida para abastecimento da população, porém, ações antropogênicas podem comprometer a sua qualidade. Considerando, que o íon nitrato é utilizado mundialmente como indicador de contaminação e que teores de nitrato acima de 10 mg/L N-NO3 acarretam danos à saúde, o presente trabalho objetivou analisar o teor de nitrato em águas subterrâneas da Região Metropolitana de Fortaleza (CE). Por meio de método de espectrofotometria na região do visível foram analisadas 37 amostras de águas subterrâneas oriundas das cidades de Aquiraz, Caucaia, Pacatuba, Horizonte, Eusébio e Fortaleza (CE). As amostras coletadas foram analisadas por profissionais do laboratório da Superintendência Estadual do Meio Ambiente - SEMACE. Os resultados obtidos revelaram que 37,8% das amostras estão em desacordo a legislação nacional em vigor. Os resultados corroboram estudos que apontam elevados teores do íon nitrato encontrados em regiões densamente urbanizadas, como é o caso da Região Metropolitana de Fortaleza (CE), por tanto, o déficit do serviço de esgotamento sanitário seria uma das causas para a presença dessa contaminação.

Unexpected nationwide nitrate declines in groundwater of Korea

AbstractElevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.

Dynamics of nitrate and methane in shallow groundwater following land use conversion from agricultural grain production to conservation easement

Abstract Fertilizer applications on agricultural fields lead to elevated nitrate concentrations in groundwater. This increases nitrate concentrations in the baseflow of streams, enhancing downstream eutrophication. Conservation practices reduce the impacts from agriculture, but little is documented on the recovery time of shallow groundwater after agriculture ceases and conservation practices are applied. Although conservation practices may reduce groundwater nitrate, they may also lead to the production of the greenhouse gas methane. This study investigated the temporal sequence of applying post-agricultural conservation practices and the effects on nitrate and methane concentrations in shallow groundwater. Harleigh Farms is a complex of fields near Oxford, MD (USA) that have been taken out of crop production and placed in conservation programs at various times after 1997. Groundwater nitrate and dissolved methane were sampled monthly from Nov 2012-Nov 2013 using age of the conservation practice as a proxy for time since fertilization. In this chronosequence study, an exponential decline in groundwater nitrate levels was found over the 16 year time period since last fertilization. Within 3–5 years after the cessation of intensive grain production, groundwater nitrate concentrations in the top of the surface unconfined aquifer dropped from 11 mg NO3−-N L−1 to 0.5 mg NO3−-N L−1. Methane only accumulated to high concentrations (2–60 μM CH4) in hydric soils with low nitrate concentrations (≪ 0.1 mg NO3−-N L−1). Our results indicate rapid loss of nitrate in the top of the surficial aquifer after the cessation of intensive agriculture and seasonal accumulations of methane in wetland-based conservation practices. These data indicate that time series of groundwater nitrate concentrations at the top of the unconfined aquifer can be used to evaluate the effectiveness of agricultural conservation practices.

Evaluation of nitrate levels in groundwater under agricultural fields in two pilot areas in central Chile: A hydrogeological and geochemical approach

The aim of this study is to evaluate the impact of the application of industrial fertilizers and liquid swine manure in groundwater in two pilot agricultural areas, San Pedro and Pichidegua, which have been under long term historic use of fertilizers. A comprehensive hydrogeological investigation was carried out to define the geology and the groundwater flow system. Chemical and isotopic tools were used to evaluate the distribution and behavior of the nitrate in the groundwater. The isotopic tools included δ18O, δ2H and 3H, which provide information about the origin and residence time of the groundwater; δ15N-NO3- and δ18O-NO3-, which provide information about nitrate sources and processes that can affect nitrate along the groundwater flow system. The application rate of liquid manure and other fertilizers all together with land uses were also evaluated. The hydrogeological investigation identified the presence of a confined aquifer underneath a thick low permeability aquitard, whose extension covers most of the two study areas. The nitrate concentration data, excepting a few points in zones located near recharge areas in the upper part of the basins and lower areas at the valley outlets (San Pedro), showed nitrate concentration below 10 mgN/L at the regional scale. The isotope data for nitrate showed no influence of the liquid swine manure in the groundwater at the regional scale, except for the high part of the basins and the outlet of the San Pedro valley, which are areas fertilized by manure. This data showed that the regional aquifer on both pilot study areas is protected by the thick low permeability aquitard, which is playing an important role on nitrate attenuation. Evidence of denitrification were also found on both shallow and deep groundwater in the Pichidegua site. This study showed that a comprehensive hydrogeological characterization complemented by chemical and isotope data is key for understanding nitrate distribution and concentration in aquifers from areas with intensive agriculture activities.

CONTRIBUTION OF MULTICRITERIA ANALYSIS AND GIS FOR THE SPECIFIC VULNERABILITY MAPPING TO AGRICULTURAL INPUTS OF GROUNDWATERS IN BONOUA AREA (SOUTHEAST OF CÔTE D'IVOIRE)

&lt;p&gt;This study focuses on the mapping of vulnerable areas to agricultural pollution of Bonoua area where groundwater are envisaged to support the District of Abidjan. Thus to achieve this, the methodological approach adopted involve the use of GIS functionality combined with multi-criteria analysis method. The analysis of groundwater vulnerability map to nitrate in the region of Bonoua highlights five vulnerability classes ranging from very low to very high. The class of "medium vulnerability" is the most dominant and represents 44.21% of the mapped areas. This vulnerability map was validated using the measured nitrate levels in groundwater.&lt;/p&gt;

The role of physical and biological processes in aquifers and their importance on groundwater vulnerability to nitrate pollution

Currently, diffuse pollution by nitrate is considered one of the main causes of groundwater quality deterioration. Many methodologies have been suggested to map aquifer vulnerability to nitrate pollution; however, no standard method has yet been established. Many proposed methods only take into account the aquifer’s protection and do not consider the physical or chemical processes in groundwater. More specifically, recent studies indicate that the fate and concentration of nitrates in aquifers mainly depend on the following: (a) the efficiency of natural attenuation (e.g. biological denitrification), (b) the physical processes of attenuation (e.g. dilution). Both the processes can lower the nitrate levels in groundwater. The aim of this research is to describe the features and role of these processes in aquifers. According to previous studies and our results, dilution and denitrification occurring in aquifers have a key role in the attenuation of nitrate. More specifically, the occurrence and effectiveness of denitrification were evaluated in a plain area in NW Italy through nitrogen isotopic fractionation analysis; the volumetric flow rate per unit width perpendicular to the flow direction, which is a function of the hydraulic gradient, hydraulic conductivity and aquifer thickness, was instead used for the assessment of nitrate attenuation capacity by means of the dilution process. Knowledge and understanding of these processes is essential to the identification of areas where groundwater is more prone to contamination. Thus, the evaluation of groundwater vulnerability to nitrate contamination cannot be separated from the comprehension of these processes.

Nitrate contamination of groundwater in the western Po Plain (Italy): the effects of groundwater and surface water interactions

This study aims to investigate the physical and chemical effects of interactions between groundwater and surface water (GW–SW)—particularly in streams—on nitrate contamination. The effects of GW–SW interactions are briefly reviewed, with a particular emphasis on processes and environments that influence increases or decreases in nitrate concentration. Then, this paper analyses nitrate concentrations in groundwater and surface water in the western Po plain (Northwestern Italy); this analysis includes the nitrate concentration profiles across the shallow aquifer and intersecting the main streams on the plain. The investigation highlights how the concentration trends are similar, even when nitrate levels in rivers and groundwater are not comparable. The maximum nitrate concentrations in the surface water were generally measured in areas with high-nitrate levels in groundwater. An analysis of the nitrate concentration profiles highlighted the mutual influences of GW–SW. The most important streams on the plain (the Po River and Stura di Demonte River), both of them gaining streams, seem to reduce the nitrate concentrations of groundwater at a study scale. The proposed conceptual model indicates how the near-stream environment (the riparian zone, wetlands, hyporheic zone and shallow organic-rich soils in the near-stream environment) and the groundwater flow systems in shallow and deep aquifers, from the recharge zone to the streams, could dramatically affect the nitrate concentrations.

Contamination of nitrate in groundwater and its potential human health: a case study of lower Mae Klong river basin, Thailand.

Nitrate contamination in groundwater is a worldwide problem especially in agricultural countries. Environmental factors, such as land-use pattern, type of aquifer, and soil-drainage capacity, affect the level of contamination. Exposure to high levels of nitrate in groundwater may contribute to adverse health effects among residents who use groundwater for consumption. This study aimed to determine the relationship between nitrate levels in groundwater with land-use pattern, type of aquifer, and soil-drainage capacity, in Photharam District, Ratchaburi Province, lower Mae Klong basin, Thailand. Health risk maps were created based on hazard quotient to quantify the potential health risk of the residents using US Environmental Protection Agency (U.S. EPA) health risk assessment model. The results showed the influence of land-use patterns, type of aquifer, and soil-drainage capacity on nitrate contamination. It was found that most of the residents in the studied area were not at risk; however, a groundwater nitrate monitoring system should be implemented.

How much do sod-based rotations reduce nitrate leaching in a cereal cropping system?

Nitrogen is essential to improving agricultural production systems, explaining why the contamination of groundwater by this nutrient is widespread. The aim of this paper was to describe data collected over 9 years on estimated leaching levels using a simple computation procedure and measurements of soil water content and water balance, nitrate concentrations in drainage water and meteorological data, and to assess the impacts of the duration of the grassland phase and the level of nitrogen fertilization on grassland on the drainage water quality. The study was carried out at a site of the Long-term Environmental Research Observation and Experimentation facility (SOERE) for Environmental Research- Agro-ecosystems, Biogeochemical Cycles and Biodiversity, run by the INRA experimental unit of Lusignan. The experimental treatments were sequences of maize, wheat and barley with different grassland rotational periods (a pure arable crop rotation; three or six years of grassland receiving high-level nitrogen applications; six years of grassland with a low N application rate and long-term grassland with nitrogen application). The study covered the period from April 2005 to June 2013, during which most drainage occurred in the autumn and early winter. Treatments with the longest duration of grassland exhibited less drainage than those containing a higher proportion of arable crops. The average nitrate concentration was 52.7±38.63mgNO3L−1 under a pure crop rotation, compared to 14.9±14.76mgNO3L−1 under a permanent grassland treatment. There were significant differences (P<0.0001) in cumulative nitrogen leaching between the different cropping systems, ranging from 9 to 37kgNha−1year−1. The introduction of mowed grassland sequences into this arable crop rotation caused a marked reduction in the nitrate levels in groundwater, and the greater the proportion of grassland within the rotation the more markedly was the NO3− concentration reduced, whatever the level of N fertilization during the grassland sequence.

A interação entre Vigilância Sanitária e Laboratório de Saúde Pública na detecção da contaminação por nitrato em água subterrânea

In Sao Paulo State (Brazil), there is growing concern about nitrate levels in groundwaters because of results from several hydrogeochemical and environmental studies. This study describes the action of health surveillance and the public health laboratory in the detection of nitrate groundwater contamination in the Monte Azul Paulista municipal district located at northeastern Sao Paulo State. Water samples from 75 wells were collected and analyzed. Contaminations were detected (concentrations greater than 10 mgN-NO3−/L) in 38 wells predominantly located at the oldest central urban area. Based on these results, it was possible to decide to restrict groundwater impounding at that municipal district.

Cathode potential and anode electron donor evaluation for a suitable treatment of nitrate-contaminated groundwater in bioelectrochemical systems

Several regions around the world present high levels of nitrate in groundwater. Due to its toxicity, nitrate must be removed before the groundwater is used as drinking-water. This study assessed how a denitrifying bioelectrochemical system could be operated to treat nitrate-polluted groundwater. It evaluated the cathode potential (from +597 to −703mV vs SHE) and the anode electron donor (acetate and water). Similar trends were found regardless of the anode electron donor. The nitrate removal rate increased from 1.05 to 5.44mgN-NO3−LNCC−1h−1 when the cathode potential was lowered from +597 to −403mV vs SHE, where it stabilized. The nitrate reduction end-products (nitrite, nitrous oxide and dinitrogen gas) also changed with the different potentials of the cathode electrode. The World Health Organization nitrates and nitrites standards for drinking-water were reached at cathode potentials between −103 and −203mV vs SHE. The highest rate of nitrate conversion to N2 (2.59mgN-NO3−LNCC−1h−1, 93.9%) occurred at −123mV using water as anode electron donor, with an estimated operational cost similar to conventional technologies (0.68·10-2kWhgN-NO3-removed-1). The long-term stability of proposed operation was demonstrated during 96days, and the rate of nitrate conversion to N2 even increased to 4.09mgN-NO3−LNCC−1h−1. A carbon-free operation for a bioelectrochemical system has been developed to treat nitrate-polluted groundwater at a competitive cost.

Numerical modelling of catchment management options to manage nitrate concentrations in water abstracted from the Chalk aquifer, Cambridgeshire, UK

Catchment management is favoured by the Water Framework Directive as a solution to the problem of rising nitrate levels in groundwater. The directive requires that member countries achieve a good, or improving, status in all water bodies by 2015. Currently, Cambridge Water relies on treatment or blending to reduce end-of-pipe nitrate concentrations to below the drinking water standard. The effectiveness of catchment management measures at 21 boreholes in Cambridgeshire was assessed with a combination of models, representing groundwater and soil zone processes. These sources are in predominantly arable catchments; they abstract from the Chalk aquifer, which is covered by Glacial Till in the south and east. Only seven sources showed a response to the catchment management scenarios within 40 years when compared with the current practice scenario. However, nitrate concentrations were not reduced at any sources by 2015 with the simulated catchment management measures. The seven sources that are most responsive to changes in land use or land management are those already affected by high nitrate levels. Catchment management may need to be used in conjunction with treatment and/or blending in the short to medium term so that Cambridge Water can continue to provide compliant drinking water to customers.

A lysimeters study of Chinese wheat and maize varieties: I. The lysimeters-rain shelter facility and the growth and water use of wheat

Excessive application of N fertilizer contributes substantially to high levels of nitrate (NO3−–N) in surface and groundwater on Northern China. A trial was set up to quantify the fate of N within intensive wheat maize rotation system with a view to improve N and water use efficiencies. This paper describes the construction and testing of a lysimeter facility used for this trial. A 44 lysimeter/rain shelter facility was constructed at Shandong Agricultural University (SDAU). Each lysimeter was equipped with a neutron access tube for soil water monitoring and ceramic solution samplers for soil solutions collection. In order to precisely quantify water input, two rain shelters were used to exclude rainwater. The water balance showed that water outputs and inputs agree within 10% for all lysimeters, and that the average water used being 5% less than the total irrigation water supplied was considered as an acceptable error for such large lysimeters. Wheat grown in these devices was consistently higher than those grown with similar fertilizer management in a field located in Ling Xian due to enhanced soil fertility and irrigation in the devices. The facility was shown to be suitable for investigating water and nutrient balances of the root zone.