Sources Of Nitrate Contamination Research Articles

Source identification of nitrate on Cheju Island, South Korea

Stable isotopes of nitrogen were used to identify sources of nitrate contamination to groundwater on Cheju, a subtropical island off the southernmost tip of the Korean peninsula. The δ15N ranges of potential animal waste and fertilizer N sources on the island were similar to those previously reported in the USA, Europe, and Africa. A total of 108 soil pore water samples were collected between January and October 1998 from fertilized soils below soybean fields and citrus groves. Low concentrations of nitrate below fertilized soybean fields indicated that it is highly unlikely that these fields contribute significant N to the groundwater problem on Cheju. The low average δ15N value of +1.9 ± 2.1‰ in pore-water nitrate and the even lower δ15N values after the fertilizer flush suggest that low levels of mineralized N are released from the bean roots or nodules. Located in the western region, the bean fields received less rainfall than the citrus groves in the southern region. Pore-water below citrus trees contained considerably higher nitrate levels, and the δ15N values became cyclically enriched after the initial fertilizer flush. Although denitrification can be expected in warm, wet soils high in organic-C content in the southern region of Cheju, it was not supported by pore-water or groundwater chemistry. Isotopic enrichment in soil pore-water is caused primarily by volatilization of ammonium-based fertilizers. Since isotopic fractionation in the soils did not exceed +4‰, source identification was possible. The dominant sources of nitrate contamination to Cheju groundwater were identified as commercial N-fertilizer applications to citrus, and, in the Seogwipo municipality, human or animal wastes.

Nitrogen Mass Balance for Municipal Wastewater

Nitrate pollution of ground water is a serious problem in many areas of the United States. One source of nitrate contamination is municipal wastewater effluent. The practice of reusing treated sewage effluent is becoming more prevalent due to limited municipal water supplies. In this study, the discharge and end use of treated effluent in the Phoenix, Ariz., metropolitan area in 1997 were investigated. It was determined that 78% of the total nitrogen in treated wastewater effluent was retained in the local watershed, and 22% was exported from the area in the Gila River. Investigation into the end use of this effluent indicates that increased nitrate contamination of ground water may result from reusing wastewater.

In Situ Septic Tank Effluent Denitrification Using a Sulfur‐Limestone Process

Septic tanks are the second largest source of groundwater nitrate contamination. In this study, the feasibility of coupling a conventional lateral field with a sulfur‐limestone (S/L) layer to treat nitrate in septic tank effluent was investigated using column reactors to simulate the septic tank soil adsorption system. The effects of different hydraulic loading rates, nitrogen loading rates, depth of SIL layers, and ratio of SIL‐to‐gravel on reactor performance were investigated. The profiles of ammonium, nitrite, nitrate, sulfate, calcium, and other parameters along the depth of reactors were measured. Significant nitrification was observed in the sand layer, while significant denitrification was observed in the S/L layer. Sulfate and hardness were produced in accordance with stoichiometric relationships. The results demonstrate that the S/L method is very effective in denitrification, while production of sulfate and hardness and existence of sulfide in effluent may be limiting factors in its application.

Utilization of Intrinsic Boron Isotopes as Co‐Migrating Tracers for Identifying Potential Nitrate Contamination Sources

AbstractThe stable isotopes of the conservative element boron, 11 B and 10 B, have been employed as co‐migrating isotopic tracers to trace potential sources of nitrate observed in ground water pumped from a large capacity 0.167 m 3/s irrigation well in the Avra Valley of southeastern Arizona. The isotopic ratios provided an identifying signature for two nitrogen carrying source waters: municipal waste water and agricultural return flow. Additional chemical parameters were also examined to corroborate the isotopic indications.Boron isotopes provided a superior delineation of mixing processes in the system compared to the general inorganic chemical parameters. Findings of this investigation indicate that the water pumped by the study well at the beginning of the 1993 irrigation season was composed of a mixture of approximately 25 % municipal waste water and 75 % background ground water. As the irrigation season progressed, an increasing proportion of water was contributed by irrigation return flow from neighboring agricultural fields.

Identification of the source and fate of nitrate contamination of the Jersey bedrock aquifer using stable nitrogen isotopes

Abstract Measured NO 3 − concentrations in the Jersey bedrock aquifer exceeded 50 mg l −1 in 67% of groundwaters sampled in June 1995. The δ 15 N values of this dissolved NO 3 − showed a total range in composition from + 3.6‰ to + 18.4‰ and exhibited a general, island-wide increase from + 4‰ in the centre of the island to + 9‰ towards coastal districts. The majority of the island is intensively cultivated and most of the sites sampled have δ 15 N values of less than + 7‰ (mean = + 7.7‰, n = 40) indicative of an agricultural source for NO 3 − . There is no apparent evidence for point-source contamination from septic tanks. The progressive seaward increase in δ 15 N is attributed to an increasing volume of deeper, denitrified groundwater mixing with shallow groundwater. Values of δ 15 N greater than + 10‰ are restricted to those coastal and valley locations that abstract, due to their low topographic elevation, the greatest proportion of deeper, denitrified groundwater. An alternative explanation is that sewer leakage enhances the observed δ 15 N values in southern urban areas, although this is considered unlikely to be occurring at present.

Nitrate cycling in streams: using natural abundances of NO3--δ15N to measure in-situ denitrification

Contamination of surface- and groundwaters as a result of anthropogenic nitrate loading is of concern in regions subjected to intense agricultural activities. The capacity of watersheds to absorb, process or release nitrate to outflow drainage waters, however, is poorly constrained. An investigation of in-stream denitrification was conducted in a small stream draining a heavily fertilized agricultural watershed by analyzing natural isotopic abundances of nitrate- nitrogen. Using 15 N isotopic signatures, we show that denitrification plays a large role in reducing nitrate levels during stream transport over a relatively short distance. We found in- situ nitrate losses of up to 50% and a corresponding shift in NO 3 - 15 Nv alues of 10 ‰ over a 600 m distance downstream consistent with denitrification. Our results suggest that in-stream nitrate losses must be considered when examining nitrate cycling and contamination in water- sheds. Not only should attempts to identify nitrate contamination sources using NO 3 - 15 N signatures be carried out with caution (as nitrate-N isotopic values can be altered during stream transport such that they no longer reflect the original nitrate source), but in-stream measures of nitrate concentrations aimed at monitoring contamination levels may underestimate nitrate inputs to surface waters due to denitrification during transport.

Determining the source of nitrate pollution in the Niger discontinuous aquifers using the natural [formula omitted] ratios

In the semi-arid Niamey area (Niger), more than 10% of the deep wells exploiting the fracture network of the Precambrian aquifer are contaminated by nitrates, with concentrations as high as 10 meq l −1. In order to identify the source(s) of this pollution, nitrate and 15N contents in the polluted wells were monitored over a 20-month period. Potential sources of nitrate contamination were also analyzed for their 15N content. The isotopic compositions of nitrate in polluted waters were > + 12‰ and in rare cases exceeded +17‰. Latrines (∼ + 15‰) may be the major nitrate source for wells showing δ 15N values above +15‰. Below this value, waters may be polluted by a combination of nitrates from both latrine and soil sources (∼ + 10‰). In some cases, the soil may account for up to 85% of the groundwater nitrate load. This mode of groundwater pollution is thought to be a consequence of deforestation. Despite their reputation as polluting agents, fertilizers ( +0.5 < δ 15 N < + 3.6‰ ) which are used in rice paddies close to the contaminated areas, do not appear to be a significant source of nitrate contamination. Denitrification is probably not a significant process in the study area. Results suggest that nitrate contamination of the aquifer is a consequence of unregulated urbanization (home-made latrines) and deforestation. While latrines are limited to the urban zones, intensive cutting of the forest to meet the city dwellers' wood demand occurs in an ever increasing area around the capital, threatening the local water supply.

Nitrogen isotope ratios identify nitrate contamination sources

Nitrate contamination of groundwater is becoming a widespread problem in California. To evaluate the utility of stable nitrogen isotopes for identifying sources of nitrate contamination, nitrogen isotope ratios (?15N) were measured on nitrate extracted from core samples taken below natural, fertilizer, on-site sewage disposal (septic) and animal sources in the Sacramento and Salinas valleys. The mean ?15N value from natural sources was not significantly different from that of fertilizer sources. The mean ?15N value from animal sources was significantly different from that of septic sources and natural and/or fertilizer sources. Nitrogen isotope ratios tend to be site specific and should be measured below suspected sources in the subsurface and in groundwater.

Nitrate in groundwaters of the Central Valley, Costa Rica

Nitrate contamination of ground water under agricultural areas is a well recognized environmental problem, yet few reports describe the problem in tropical regions. This study evaluated concentrations of NO 3-N in shallow aquifers used to provide drinking water to the inhabitants of the Valle Central in Costa Rica. The watershed that recharges these aquifers is an agricultural and urban catchment that may leach nitrate derived mainly from fertilization (that averages 270 kg/ha per annum as nitrogen applied to coffee) and sewage contamination. Aquifers were sampled on an elevation gradient from 780 to 1440 m, along which land use changes from urban and agricultural uses at low and mid-elevations to unfertilized pastures and forests at the highest elevations. Ground water was sampled once during an extensive survey of 56 wells and springs, and during a monthly collection of 14 wells and springs over a 25-month period. Concentrations of NO 3-N were closely related to elevation and averaged 0.37 μg/mL in aquifers at 1600 to 2300 m, 1.70 μg/mL at 1200 to 1300 m, and 4.45 μg/mL at 900 to 940 m. There were significant variations in concentrations of NO 3-N at the same elevation. Water quality monitoring should be expanded to determine the distribution of wells and springs with high nitrate concentrations throughout the Central Valley and to identify the potential sources of nitrate contamination. Measures directed to improve the efficiency of nitrogen fertilizer and to modernize sewage management practices are needed to help ensure the water quality of these productive aquifers.

N-15 Identification of nonpoint sources of nitrate contamination beneath cropland in the Nebraska Panhandle: two case studies

Monitoring of municipal wells near the town of Sidney and domestic wells near Oshkosh in Nebraska's Panhandle indicated the nitrate-nitrogen (NO 3-N) levels were increasing and exceeded the maximum contaminant level of 10 mg/l NO 3-N in several wells. Both areas are located in narrow stream valleys that are characterized by well-drained soils, highly permeable intermediate vadose zones, shallow depths to groundwater, and intensive irrigated corn production. Both areas also have a large confined cattle feeding operation near the suspected contamination and potentially could be contaminated by more than on nitrate source. At Sidney NO 3-N concentrations were measured in 13 monitoring wells installed along an east-west transect im the direction of groundwater flow, 26 private wells, and eight municipal wells. Nitrate-nitrogen concentrations were homogeneous beneath a 5 km by 1.2 km area and averaged 11.3 ± 1.8 mg/l NO 3-N. The δ 15N-NO 3 values in the monitoring and municipal wells had a narrow range from +5.8 to +8.8%. The isotopic ratios are indicative of a mixed source of nitrate contamination, which originates from agronomic (commercial fertilizer N and mineralized N) N and animal waste. Both commercial fertilizer N and animal wastes are applied to the irrigated fields. Nitrate-nitrogen concentrations in two multilevel samplers installed downgradient from irrigated cornfields at the Oshkosh site averaged 20.1 ± 13.3 mg/l NO 3-N and 37.3 ± 8.2 mg/l NO 3-N. The δ 15N-NO 3 values spanned a narrow range from +3.5 to +5.9% and averaged +4.0 ± 0.5% and +5.0 ± 0.6%. These low values are indicative of leachates from commercial fertilizer applied to the irrigated fields.

Health effects associated with waste treatment, disposal, and reuse

and transfer of fecal indicator organisms (coliforms, enterococci, sulphite-reducing clostridia, and coliphages) downstream of a wastewater treatment plant were investigated at Lake Kallavesi, Finland (R?jala and Heinonen-Tanski, 1998). The observation of indicator organisms up to 18 km from the discharge point and good survival in the summer suggested that direct use of lake water could constitute a health risk. The effect of combined sewer overflows (CSOs) on the occur rence of Giardia and Cryptosporidium was investigated (Gibson et al., 1998). The results suggested that CSOs significantly contribute to the load of Giardia and Cryptosporidium in ambient waters and source waters for drinking and recreational uses. An outbreak of waterborne giardiasis in Temagami, Ontario, in 1994 was assessed (Wallis et al., 1998). The outbreak was traced to leakage from the municipal wastewater system into the lake and exacerbated by spring snow-melt runoff. The influence of rainwater on the con centration of helminth eggs in wastewater was investigated (Capizzi and Schwartzbrod, 1998). Concentrations of parasite eggs vary according to water flow rates and sedimentation; heavy rain following rainless days yielded higher concentrations in raw wastewater at the treatment plant, whereas continuous moderate rain resulted in low variation of parasite eggs. The prevalence of respiratory symptoms, skin disorders, status of spirometric lung functions, and amino acid profiles among wastewater workers were reported (Bener et al., 1998). Wastewa ter workers had a higher prevalence of respiratory symptoms than controls, significant for chronic cough (p < 0.02), chronic phlegm (p < 0.03), chronic bronchitis (p < 0.02), asthma (p < 0.02), dyspneoa (p < 0.001), and nasal catarrh (p < 0.001) and acute symptoms of pruritus (p < 0.003), tinea (p < 0.004), dermatitis (p < 0.001), and nose irritation (p < 0.005). Spirometry tests scored lower in wastewater workers, and most of the plasma amino acids concentrations were elevated among wastewater workers. An investigation examining whether inadequate septic system construction may cause contamination of wells with coliform bacteria or nitrates was reported (Tuthill et al., 1998). The authors found that coliform bacteria and nitrate contamination were neg atively correlated with lot size, and coliform bacteria levels were negatively correlated with casing length, which suggested that septic systems may be a source of coliform bacteria and nitrate contamination in wells. CONTAMINATION OF WATER SUPPLIES

Irrigated Agriculture and Water Quality in East

The northeastern and Appalachian states have a diverse array of geology, soils, and climate. Irrigation is concentrated in a few states, with the largest irrigation area in the Coastal Plain soils. Most of these soils are sandy and very susceptible to leaching. The groundwater recharge area in the Coastal Plain is directly above the aquifer. Most of the increase in irrigation has been to irrigate corn in Delaware, Maryland, and Virginia. Groundwater studies have been conducted in Delaware, Maryland, and New York in irrigated regions. Nitrate and aldicarb leaching has occurred on‐Long Island, New York, where potatoes are grown. Poultry manure is the largest source of nitrate contamination of the water table aquifer on the Delmarva Peninsula in Maryland. Both pesticide and nitrate leaching under irrigation have been studied in Delaware. A total water management system that can be used for both drainage and subsurface irrigation has been developed in North Carolina. The system will increase crop yields and h...

A nitrogen-isotope study of the sources of nitrate contamination in groundwater of the pleistocene coastal plain aquifer, Israel

An elevated level of NO 3 (mean value for 1981 was 53 mg l −1 NO 3 as NO 3 − occurs in phreatic groundwater in the Coastal Plain sandy aquifer, Israel. NO 3 − in water with a wide range of concentrations has δ 15N in the range of +4.7 to + 11.4‰ , suggesting derivation from oxidation of soil organic matter and (in specific cases) from animal wastes. Only one sample has δ 15N = −0.3‰ that would indicate derivation through fertilizer application. Water from sewage treatment plant used for irrigation, or for filtration into the aquifer, is highly enriched in 15N ( + 19.2 to +28.8‰), reflecting ammonia volatilization. The isotopic data are consistent with the model presented by Ronen et al. that suggested that the main sources of NO 3 contamination in groundwater in the region are: oxidation of organic matter during cultivation of virgin land and swamp reclamation.

Investigation of sources of groundwater nitrate contamination in the Burbank-Wallula area of Washington, U.S.A.

During the fall and early winter of 1980, groundwater samples were collected from 38 public supply and domestic wells in the Burbank-Wallula area of Washington. Groundwater nitrate-nitrogen (NO 3-N) concentrations ranged from 3.9 to 32 mg l −1 and averaged 10.5 mg l −1. Nitrogen isotope composition ( δ 15N) of the NO 3-N ranged from +1.3 to +16.0‰ and averaged +4.1‰. The preponderance of low δ 15N-values suggests that agricultural leachates (from oxidation of soil humus or use of nitrogen fertilizers) are the primary source of contamination for the area. Fourteen of the 38 wells were sampled at least twice in a four-month period. The relative invariability in NO 3-N levels and δ 15N in these wells suggests little or no temporal change in either the source or the magnitude of the source. Two additional samples collected in May 1981 from monitoring wells on the perimeter of a cropped field spray-irrigated with cattle waste from an anaerobic lagoon had δ 15N-values for the NO 3-N of +12.0 and +18.7‰, respectively. The high δ 15N-values in these wells indicate that the NO 3-N is predominantly derived from animal waste.

Water pollution by nitrates from the agricultural industry

The principal sources of nitrogen in water are domestic sewage, garbage, industrial wastes, and the agricultural industry - animal wastes, nitrogenous fertilizers, and products from the decomposition of plant material in soil. The contribution from precipitation and atmospheric sediments is about 1.0 ppm or 5.8 lb/acre/year at Hamilton (15). In this paper, we present results of our current research on the transport of nitrogen compounds by water in a porous medium. During this transfer, chemical and microbiological reactions take place that determine the concentration and distribution of nitrogen in a soil profile at a given time. Data are presented that indicate the levels of NO3--N in ground waters from several sources as well as a discussion of possible sources of nitrate contamination.