Median Nitrate Concentrations Research Articles

IMPACT OF A TURFGRASS SYSTEM ON NUTRIENT LOADINGS TO SURFACE WATER1

ABSTRACT: Turfgrass systems are one of the most intensively managed land uses in the United States. Establishment and maintenance of high quality turfgrass usually implies substantial inputs of water, nutrients, and pesticides. The focus of this work was to quantify the concentration and loading of a typically maintained municipal turfgrass environment on surface water. Water quantity and quality data were collected from a golf course in Austin, Texas, and analyzed for a 13‐month period from March 20, 1998, to April 30, 1999. Twenty‐two precipitation events totaling 722 mm, produced an estimated 98 mm of runoff. Nutrient analysis of surface runoff exiting the course exhibited a statistically significant (p < 0.05) increase in median nitrate plus nitrite nitrogen (NO3+NO2‐N) concentration compared to runoff entering the course, a statistically significant decrease in ammonia nitrogen (NH4‐N), but no difference in orthophosphate (PO4‐P). During the 13‐month period, storm runoff contributed an estimated 2.3 kg/ha of NO3+NO2‐N and 0.33 kg/ha of PO4‐P to the stream. Storm flow accounted for the attenuation of 0.12 kg/ha of NH4‐N. Baseflow nutrient analysis showed a statistically significant increase in median NO3+NO2‐N, a significant reduction in NH4‐N, and no change in PO4‐P. Estimated NO3+NO2‐N mass in the baseflow was calculated as 4.7 kg/ha. PO4‐P losses were estimated at 0.06 kg/ha, while 0.8 kg/ha of NH4‐N were attenuated in baseflow over the study period. Even though nutrient concentrations exiting the system rarely exceeded nutrient screening levels, this turfgrass environment did contribute increased NO3+NO2‐N and PO4‐P loads to the stream. This emphasizes the need for parallel studies where management intensity, soil, and climate differ from this study and for golf course managers to utilize an integrated management program to protect water quality while maintaining healthy turfgrass systems.

THE EFFECT OF RESIDENTIAL DEVELOPMENT ON GROUND‐WATER QUALITY NEAR DETROIT, MICHIGAN1

ABSTRACT: Two water‐quality studies were done on the outskirts of the Detroit metropolitan area to determine how recent residential development has affected ground‐water quality. Pairs of monitor and domestic wells were sampled in areas where residential land use overlies glacial outwash deposits. Young, shallow waters had significantly higher median concentrations of nitrate, chloride, and dissolved solids than older, deeper waters. Analysis of chloride/bromide ratios indicates that elevated salinities are due to human activities rather than natural factors, such as upward migration of brine. Trace concentrations of volatile organic compounds were detected in samples from 97 percent of the monitor wells. Pesticides were detected infrequently even though they are routinely applied to lawns and roadways in the study area. The greatest influence on ground‐water quality appears to be from septic‐system effluent (domestic sewage, household solvents, water‐softener backwash) and infiltration of storm‐water runoff from paved surfaces (road salt, fuel residue). No health‐related drinking‐water standards were exceeded in samples from domestic wells. However, the effects of human activities are apparent in 76 percent of young waters, and at depths far below 25 feet, which is the current minimum well‐depth requirement.

Nutrients in Groundwaters of the Conterminous United States, 1992−1995

Results of a national water quality assessment indicate that nitrate is detected in 71% of groundwater samples, more than 13 times as often as ammonia, nitrite, organic nitrogen, and orthophosphate, based on a common detection threshold of 0.2 mg/L. Shallow groundwater (typically 5 m deep or less) beneath agricultural land has the highest median nitrate concentration (3.4 mg/L), followed by shallow groundwater beneath urban land (1.6 mg/L) and deeper groundwater in major aquifers (0.48 mg/L). Nitrate exceeds the maximum contaminant level, 10 mg/L as nitrogen, in more than 15% of groundwater samples from 4 of 33 major aquifers commonly used as a source of drinking water. Nitrate concentration in groundwater is variable and depends on interactions among several factors, including nitrogen loading, soil type, aquifer permeability, recharge rate, and climate. For a given nitrogen loading, factors that generally increase nitrate concentration in groundwater include well-drained soils, fractured bedrock, and ir...

Nitrate Behavior in Ground Waters of the Southeastern USA

AbstractPrincipal components analysis (PCA) was performed with water‐quality data from studies conducted during 1993 to 1995 to explore potential nitrate‐attenuation processes in ground waters of the south‐eastern USA. Nitrate reduction is an important attenuation process in selected areas of the Southeast. A nitrate‐reduction component explains 23% of the total variance in the data and indicates that nitrate and dissolved oxygen (DO) are inversely related to ammonium, iron, manganese, and dissolved organic carbon (DOC). Additional components extracted by PCA include calcite dissolution (18% of variance explained) and phosphate dissolution (9% of variance explained). Reducing conditions in ground waters of the region influence nitrate behavior through bacterially mediated reduction in the presence of organic matter, and by inhibition of nitrate formation in anoxic ground water beneath forested areas. Component scores are consistent with observed water‐quality conditions in the region. For example, median nitrate concentration in ground‐water samples from the Albemarle‐Pamlico Drainage Basin (ALBE) Coastal Plain is <0.05 mg L−1, median DOC concentration is 4.2 mg L−1, and median DO concentration is 2.1 mg L−1, consistent with denitrification. Nitrate reduction does not occur uniformly throughout the Southeast. Median DO concentrations in ground‐water samples from the Apalachicola‐Chattahoochee‐Flint River Basin (ACFB) are 6.2 to 7.1 mg L−1, and median nitrate concentrations are 0.61 to 2.2 mg L−1, inconsistent with denitrification. Similarly, median DO concentration in samples from the Georgia‐Florida Coastal Plain (GAFL) is 6.0 mg L−1 and median nitrate concentration is 5.8 mg L−1.

Seasonal and Spatial Patterns of Nitrate and Silica Concentrations in Canajoharie Creek, New York

AbstractThe impact of nonpoint‐source pollution on surface waters in agricultural watersheds is an emerging environmental issue. As part of the U.S. Geological Survey National Water Quality Assessment program in the Hudson River Basin, Canajoharie Creek was monitored for seasonal and spatial patterns of nutrient chemistry from March 1993 to January 1996. Nitrate and silica concentrations in Canajoharie Creek suggest that seasonal and spatial variations of these nutrients are dominated by biological processes, particularly uptake by phytoplankton. Observed concentration patterns were more typical of those observed in much larger, low‐gradient streams. The median nitrate and silica concentrations in Canajoharie Creek were significantly lower from April through November than during winter. Concentrations of both constituents declined downstream from the headwaters during base‐flow conditions in June 1995. Groundwater and surface water chemistry data support biological causes for downstream decreases in silica. The strong correlation between nitrate and silica in samples collected along the mainstem suggests that most of the nitrate decrease is due to uptake by diatoms. Downstream patterns of chlorophyll‐a in phytoplankton strongly suggest the conversion of in‐stream nutrients to algal biomass. Data collected from Canajoharie Creek outlet during the northeast drought of 1995 indicate that silica concentrations in May had possibly declined to a level that adversely affected the diatom community. This decline in the diatom population and subsequent resurgence is inferred from a sharp rise in silica concentrations between May and July and a reversal of this trend from mid‐July through October without associated changes in hydrology.

NUTRIENTS IN STREAMS DURING BASEFLOW IN SELECTED ENVIRONMENTAL SEVFINGS OF THE POTOMAC RiVER BASIN1

ABSTRACT: A regional assessment of water quality in small streams was conducted within four areas of distinct physiography and lithology in the upper Potomac River Basin. The Potomac River is a major tributary to the Chesapeake Bay, and this study provides new insight on the relationships between nutrient concentrations in small streams and watershed characteristics within this river basin. Nutrient concentrations were compared to land‐use data including categories for agriculture (cropland and pasture), urban areas, and forests. Among agricultural areas, streams draining areas of intense row cropping typically contained higher nitrate concentrations than did those draining pastures. Streams draining forested areas typically had the lowest nutrient concentrations. Streams in areas underlain by carbonate bedrock were more likely to contain elevated concentrations of inorganic nitrogen and potassium than did streams in areas underlain by fractured siliciclastic or crystalline rocks, and we suggest that this is a physical phenomenon related to high hydraulic conductivities in carbonate ground‐water systems. The median nitrate concentrations were highest in the Great Valley portion of the Valley and Ridge physiographic province, particularly in watersheds that have both carbonate bedrock and intensive row cropping. Values of nitrate in these streams ranged up to 8.99 mg/L as nitrogen. The soluble phosphorus concentrations during baseflow were generally low in all sub‐units, even in some settings with potential for high phosphorus inputs such as urban areas with municipal point sources or agricultural areas. The mobility of phosphorus in these environments may be hindered by adsorption and geochemical reactions.

Endogenous nitric oxide and low systemic vascular resistance after cardiopulmonary bypass

Objectives: To investigate the relationship between excessive endogenous production of nitric oxide (NO) and the low systemic vascular resistance (SVR) syndrome after cardiac surgery. Design: Prospective, case-control. Cases defined by low SVR postoperatively (< 750 dyn/s/cm −5), and matched with controls (> 900 dyn/s/cm −5). Setting: Cardiothoracic intensive care unit (ICU) in a tertiary care hospital. Participants: Forty-four patients after cardiac surgery. Interventions: Collection of plasma and urine samples after identification. Measurements and Main Results: Plasma and urine nitrate concentrations were measured as an index of endogenous NO production. Hemodynamic, inotropic, and outcome data were collected. Median nitrate concentrations did not differ between cases and controls (plasma, 58 μmol/L v 62 μmol/L, p = 0.43; urine, 399 μmol/L v 404 μmol/L, p = 0.38). Times to extubation and intensive care unit (ICU) discharge were prolonged in patients with low SVR (17.8 hours v 8.7 hours, p = 0.021; 2.5 days v 1.2 days, p = 0.019, respectively). Conclusions: No association between “low SVR syndrome” and endogenous NO production was found. Patients with low SVR after cardiac surgery required a longer period of inotropic and ventilator support, with delay in discharge from the ICU. The risk and cost implications of this syndrome support further research.

Denitrification and mixing in a stream—aquifer system: effects on nitrate loading to surface water

Ground water in terrace deposits of the South Platte River alluvial aquifer near Greeley, Colorado, USA, had a median nitrate concentration of 1857 μmol l −1. Median nitrate concentrations in ground water from adjacent floodplain deposits (468 μmol l −1) and riverbed sediments (461 μmol l −1), both of which are downgradient from the terrace deposits, were lower than the median concentration in the terrace deposits. The concentrations and δ 15N values of nitrate and N 2 in ground water indicated that denitrifying activity in the floodplain deposits and riverbed sediments accounted for 15–30% of the difference in nitrate concentrations. Concentrations of Cl − and SiO 2 indicated that mixing between river water and ground water in the floodplain deposits and riverbed sediments accounted for the remainder of the difference in nitrate concentrations. River flux measurements indicated that ground-water discharge in a 7.5 km segment of river had a nitrate load of 1718 kg N day − and accounted for about 18% of the total nitrate load in the river at the downstream end of that segment. This nitrate load was 70% less than the load predicted on the basis of the median nitrate concentration in the terrace deposits and assuming no denitrification or mixing in the aquifer. Water exchange between the river and aquifer caused ground water that originally discharged to the river to reenter denitrifying sediments in the riverbed and floodplain, thereby further decreasing the nitrate load in this stream—aquifer system. Results from this study indicated that denitrification and mixing within akluvial aquifer sediments may substantially decrease the nitrate load added to rivers by discharging ground water.

Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA

A survey of the chemical quality of ground water in the unconsolidated alluvial aquifer beneath a major urban center (Denver, Colorado, USA) was performed in 1993 with the objective of characterizing the quality of shallow ground-water in the urban area and relating water quality to land use. Thirty randomly selected alluvial wells were each sampled once for a broad range of dissolved constituents. The urban land use at each well site was sub-classified into one of three land-use settings: residential, commercial, and industrial. Shallow ground-water quality was highly variable in the urban area and the variability could be related to these land-use setting classifications. Sulfate (SO 4) was the predominant anion in most samples from the residential and commercial land-use settings, whereas bicarbonate (HCO 3) was the predominant anion in samples from the industrial land-use setting, indicating a possible shift in redox conditions associated with land use. Only three of 30 samples had nitrate concentrations that exceeded the US national drinking-water standard of 10 mg l −1 as nitrogen, indicating that nitrate contamination of shallow ground water may not be a serious problem in this urban area. However, the highest median nitrate concentration (4.2 mg l −1) was in samples from the residential setting, where fertilizer application is assumed to be most intense. Twenty-seven of 30 samples had detectable pesticides and nine of 82 analyzed pesticide compounds were detected at low concentrations, indicating that pesticides are widely distributed in shallow ground water in this urban area. Although the highest median total pesticide concentration (0.17 μg l −) was in the commercial setting, the herbicides prometon and atrazine were found in each land-use setting. Similarly, 25 of 29 samples analyzed had detectable volatile organic compounds (VOCs) indicating these compounds are also widely distributed in this urban area. The total VOC concentrations in sampled wells ranged from nondetectable to 23 442 μg l −. Widespread detections and occasionally high concentrations point to VOCs as the major anthropogenic ground-water impact in this urban environment. Generally, the highest VOC concentrations occurred in samples from the industrial setting. The most frequently detected VOC was the gasoline additive methyl tert-butyl ether (MTBE, in 23 of 29 wells). Results from this study indicate that the quality of shallow ground water in major urban areas can be related to land-use settings. Moreover, some VOCs and pesitides may be widely distributed at low concentrations in shallow ground water throughout major urban areas. As a result, the differentiation between point and non-point sources for these compounds in urban areas may be difficult.

VARIABLES INDICATING NITRATE CONTAMINATION IN BEDROCK AQUIFERS, NEWARK BASIN, NEW JERSEY1

ABSTRACT: Variables that describe well construction, hydrogeology, and land use were evaluated for use as possible indicators of the susceptibility of ground water in bedrock aquifers in the Newark Basin, New Jersey, to contamination by nitrate from the land surface. Statistical analyses were performed on data for 132 wells located throughout the Newark Basin. Concentrations of nitrate (as nitrogen) did not exceed the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter (mg/L) in any of the water samples (U.S. Environmental Protection Agency, 1991). Variables that describe hydrogeology and well construction were found not to be statistically significant in relation to concentrations of nitrate. This finding can be attributed to the complex nature of flow in bedrock aquifers and mixing of water from shallow and deep water‐bearing zones that occurs within these wells, which are constructed with long open intervals. Distributions of nitrate concentrations were significantly different among land‐use groups on the basis of land use within both a 400 and an 800‐m radius zone of the well. The median concentrations of nitrate (as N) in water from wells in predominantly urban‐residential (2.5 mg/L) and agricultural areas (1.8 mg/L) were greater than the median concentration of nitrate in water from wells in predominantly undeveloped areas (0.5 mg/L).

Well Water Quality, Well Vulnerability, and Agricultural Contamination in the Midwestern United States

The Heidelberg College Cooperative Private Well Testing Program is designed to evaluate water quality in private rural wells. The program inexpensively provides large datasets that reflect relationships between well contamination and associated factors, and support local groundwater protection and education programs. Nearly 35 000 wells have been tested in Ohio, Indiana, Illinois, West Virginia, and Kentucky. Median nitrate concentration was 0.07 mg/L ; 3.4% of wells exceeded the drinking water standard of 10 mg/L ; 23% exceeded 1 mg/L. Triazines were detected in 4.9% of 12 362 samples ; the atrazine MCL of 3.0 μg/L was exceeded in 0.1% of samples. Acetanilides were detected in 9.7% of 10 967 samples ; 1.1% exceeded the alachlor MCL of 2.0 μg/L. Many acetanilide detections, and most higher concentrations, are due to an alachlor breakdown product and involve little or no alachlor. Information supplied by well owners was used to examine the impact of cultural and geological factors on well water quality. Concentrations are higher in wells that are shallower, older, dug, or driven ; located close to cropland, feedlots, or chemical mixing sites ; or located in sandy soils. Where wells combine the most vulnerable alternative for two or three factors, the probability of contamination increases dramatically. Mapping sometimes reveals spatial patterns of contamination that reflect geological influences. River valley aquifers, sandy soils with high water tables, karst areas, and reef structures with surficial expressions are all reflected in county maps of the data.

Well Water Quality, Well Vulnerability, and Agricultural Contamination in the Midwestern United States

AbstractThe Heidelberg College Cooperative Private Well Testing Program is designed to evaluate water quality in private rural wells. The program inexpensively provides large datasets that reflect relationships between well contamination and associated factors, and support local groundwater protection and education programs. Nearly 35 000 wells have been tested in Ohio, Indiana, Illinois, West Virginia, and Kentucky. Median nitrate concentration was 0.07 mg/L; 3.4% of wells exceeded the drinking water standard of 10 mg/L; 23% exceeded 1 mg/L. Triazines were detected in 4.9% of 12 362 samples; the atrazine MCL of 3.0 µg/L was exceeded in 0.1% of samples. Acetanilides were detected in 9.7% of 10 967 samples; 1.1% exceeded the alachlor MCL of 2.0 µg/L. Many acetanilide detections, and most higher concentrations, are due to an alachlor breakdown product and involve little or no alachlor. Information supplied by well owners was used to examine the impact of cultural and geological factors on well water quality. Concentrations are higher in wells that are shallower, older, dug, or driven; located close to cropland, feedlots, or chemical mixing sites; or located in sandy soils. Where wells combine the most vulnerable alternative for two or three factors, the probability of contamination increases dramatically. Mapping sometimes reveals spatial patterns of contamination that reflect geological influences. River valley aquifers, sandy soils with high water tables, karst areas, and reef structures with surficial expressions are all reflected in county maps of the data.

NITRATE CONCENTRATIONS IN KARST SPRINGS IN AN EXTENSWELY GRAZED AREA1

ABSTRACT: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about 18 percent of the Region's land area. An estimated one‐third of the Region's farms, cattle, and agricultural market value are located on karst terrain. Nitrate concentrations were measured in several karst springs in Southeastern West Virginia in order to determine the impact of animal agriculture on nitrate pollution of the karst ground water system. Karst basins with 79, 51, 16, and 0 percent agriculture had mean nitrate concentrations of 15.8, 12.2, 2.7, and 0.4 mg/l, respectively. A strong linear relationship between nitrate concentration and percent agricultural land was shown. Median nitrate concentration increased about 0.19 mg l‐1 per percent increase in agricultural land. Weather patterns were also found to significantly affect the median nitrate concentrations and the temporal variability of those concentrations. Lower nitrate concentrations and lower temporal variability were observed during a severe drought period. It was concluded that agriculture was significantly affecting nitrate concentrations in the karst aquifer. Best management practices may be one way to protect the ground water resource.

Effect of forested wetlands on nitrate concentrations in ground water and surface water on the Delmarva Peninsula

The Delmarva Peninsula is an extensively farmed region in which nitrate from commercial fertilizers and poultry has entered the ground water and streams. The peninsula contains forested wetlands in a variety of settings, and their size and location are a result of the surrounding hydrologic and soil conditions. Three regions, here referred to as hydrogeomorphic regions, were selected for study. Each region has characteristic geologic and geomorphic features, soils, drainage patterns, and distribution of farmland, forests, and forested wetlands. In all three regions, forested wetlands generally occupy poorly drained areas whereas farmlands generally occupy well-drained areas. The three hydrogeomorphic regions studied are the well-drained uplands, the poorly drained uplands, and the surficial-confined region. The well-drained uplands have the largest amount of farmland and the smallest amount of forested wetlands of the three regions; here the forested wetlands are generally restricted to narrow riparian zones. The poorly drained uplands contain forested wetlands in headwater depressions and riparian zones that are interspersed among well-drained farmlands. The surficial-confined region has the smallest amount of farmland and largest amount of forested wetlands of the three regions studied. Wetlands in this region occupy the same topographic settings as in the poorly drained uplands. Much of the farmland in the surficial-confined region was previously wetland. Nitrate concentrations in ground water and surface water on the peninsula range widely, and their distribution reflects (1) the interspersion of forests among farmland, (2) hydrogeologic conditions, (3) types of soils, and (4) the ground-water hydrology of forested wetlands. The well-drained uplands had higher median nitrate concentrations in ground water than the poorly drained uplands or the surficial-confined region. The highest nitrate concentrations were in oxic parts of the aquifer, which are beneath well-drained soils that are farmed, and the lowest were in anoxic parts of the aquifer, which are beneath poorly drained soils overlain by forested wetlands. The effect of forested wetlands on water quality depends on the hydrogeologic conditions, extent of farming, and type of soils. The three regions contain differing combinations of these factors and thus are useful for isolating the effects of forested wetlands on water quality.

Effects of Nutrient Management on Nitrate Levels in Ground Water Near Ephrata, Pennsylvania

AbstractEffects of the implementation of nutrient management practices on ground‐water quality were studied at a 55‐acre farm in Lancaster County, Pennsylvania, from 1985‐90. After nutrient management practices were implemented at the site in October 1986, statistically significant decreases (Wilcoxon Mann‐Whitney test) in median nitrate concentrations in ground‐ water samples occurred at four of the five wells monitored. The largest decreases in nitrate concentration occurred in samples collected at the wells that had the largest nitrate concentrations prior to nutrient management. The decreases in median nitrate concentrations in ground‐water samples ranged from 8 to 32 percent of the median concentrations prior to nutrient management and corresponded to nitrogen application decreases of 39 to 67 percent in contributing areas that were defined upgradient of these wells.Changes in nitrogen applications to the contributing areas of five water wells were correlated (Spearman rank‐sum test) with nitrate concentrations of the well water. Changes in ground‐water nitrate concentrations lagged behind the changes in applied‐nitrogen fertilizers (primarily manure) by approximately 4 to 19 months.

A Comparison of Nitrogen in Shallow Ground Water from Sewered and Unsewered Areas, Nassau County, New York, from 1952 through 1976a

ABSTRACTMedian nitrogen concentrations of ground water and water from streams in Nassau County were statistically analyzed on an areal and temporal basis and by individual well to compare concentrations of nitrogen in ground water beneath sewered and unsewered areas. The comparison is discussed in terms of hydrogeologic conditions and major point and nonpoint sources of nitrogen.Although no significant differences in median nitrate concentrations during the 25‐year period of record were observed between the sewered and unsewered areas, recent (1972–76) ammonium and nitrate data suggest a relative improvement in water quality in the sewered area. This finding is based on (1) significantly lower ammonium and nitrate concentrations in stream water of the sewered area during base flow, (2) significantly lower median ammonium concentrations in ground water in the sewered area, (3) significant decreasing long‐term nitrate trends in water from 8 of 13 wells in the sewered area where records were sufficient for analysis, and (4) significantly lower median nitrate concentrations near the water table beneath the sewered area.The lack of significant difference between median nitrate concentrations in the sewered and unsewered areas may be in part due to sampling bias and to the considerable length of time necessary for ground water in the sewered area, which was contaminated by cesspool and septic‐tank effluent before sewering, to reach a point of discharge in a stream or bay.In addition, ammonium leached from landfills and nitrate originating from nonpoint sources such as fertilizers and animal wastes, cannot be removed by sewers and may be obscuring water‐quality improvements brought about by sewering.