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USGS1994

Persistence of metals in soil and selected vertebrates in the vicinity of the Palmerton zinc smelters

Concentration of Cd, Pb, Zn, and Cu in soil and wildlife at the Palmerton zinc smelter site in eastern Pennsylvania were determined 6 yr after zinc smelting was terminated in 1980. Levels of the four metals were higher in litter (01 and 02 horizon) than in soil (A1 horizon), and the metals were at or near levels when the smelters were still in operation. Levels of metals in soil were highest at sites close to the smelters and decreased as distances from the smelters increased. The relation of decreasing amounts of metals in body tissues with increasing distance from the smelters also held true for amphibians and mammals. An exception to this relation was higher level of Cu in red‐backed salamanders ( Plethodon cinereus ) captured ≈17 km downwind than those captured ≈12 km downwind. Levels of Zn, Pb, and Cu in liver, kidney, and muscle tissue of white‐footed mice ( Peromyscus leucopus ) were not different ( P > 0.05) which is reportedly considered an indication of environmental contamination. Levels of Cd in kidneys and liver of white‐tailed deer ( Odocoileus virginianus ) at Palmerton were five times higher than those for whitetailed deer collected 180 km southwest of Palmerton in southcentral Pennsylvania. The abnormal amounts of metals in the tissues of terrestrial vertebrates, and the absence or low abundance of wildlife at Palmerton indicated that ecological processes within 5 km of the smelters were markedly influenced 6 yr after zinc smelting was discontinued.

Pennsylvania↗

USGS1994

Adsorption and desorption of atrazine and deethylatrazine by low organic carbon geologic materials

The adsorption and desorption of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and a primary metabolite, deethylatrazine (2-amino-4-chloro-6-isopropylamino-s-triazine; DEA), by low organic C (≤ 3.3 g kg −1 ) materials were measured by batch-equilibrium techniques. The adsorbents were samples of glacial outwash sand, till, and stream sediments. The adsorption of both atrazine and DEA conformed to linear isotherms. The adsorption of atrazine by most of the adsorbents yielded apparent K oc values that were in excess of those based on surface agricultural soils. Adsorption correlated with only the pH of the sand-water suspensions. The desorption of atrazine was hysteretic under the conditions of the measurement. DEA had a lower affinity for the same adsorbents; the mean ratio of K d values of DEA to those of atrazine was 0.37 ± 0.20. DEA adsorption did not correlate with organic C, surface area, clay content of the adsorbents, or with the pH of the suspensions. DEA adsorption, unlike atrazine, tended to be reversible. There was a linear relationship between the adsorption constants of atrazine and those of DEA.

Journal of Environmental Quality↗

USGS1994

Displacement of soil pore water by trichloroethylene

Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter are very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone.

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USGS1994

Effects of ion exchange on stream solute fluxes in a basin receiving highway deicing salts

At Fever Brook, a 1260-ha forested basin in central Massachusetts, highway deicing salt application increased the solute flux in streamflow by 120% above background flux (equivalent basis) during a 2-yr period. Attempts to isolate the nonsalt component of stream solute fluxes have commonly subtracted salt contributions based on the net Cl flux (Cl output in streamflow minus Cl input in precipitation). In these studies, any net Na flux in excess of the amount needed to balance the net Cl flux has been attributed to weathering. At Fever Brook, however, the net output of Na was less than the net output of Cl, suggesting a loss of Na within the basin. The Na sink was inferred to be cation exchange of Na for Ca and Mg in the soil. A method was developed to quantify the exchange based on a Na budget, which included an independent estimate of the Na flux from weathering. The amount of exchange was apportioned to Ca and Mg based on their relative concentrations in the stream. The background fluxes of Ca and Mg (i.e., those that would occur in the absence of deicing salts) were calculated by subtracting the amounts from ion exchange plus the much smaller direct contributions in deicing salts from the observed fluxes. Ion exchange and direct salt contributions increased the net output fluxes of Ca and Mg, each by 44% above background. In basins that receive deicing salts, failure to account for cation exchange thus may result in an underestimate of the flux of Na from weathering and overestimates of the fluxes of Ca and Mg from weathering.

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USGS1995

Aerodynamic measurements of methyl bromide volatilization from tarped and nontarped fields

Methyl bromide (MeBr) is used extensively in agriculture as a soil fumigant and there is growing concern over the role it may play in the depletion of stratospheric ozone. Methyl bromide is applied using various techniques and very little is known about how much of the applied fumigant volatilizes into the atmosphere after the application. This field study was designed to estimate the post-application methyl bromide volatilization loss rates from two different application practices. The fields were approximately 6 km apart in Monterey County, California, and were treated in conformity with local practices as of 1992. The MeBr was injected at a depth of 25 to 30 cm. One field was covered simultaneously with a high-barrier plastic film tarp during the application, and the other was left uncovered, but the furrows made by the injection shanks were bedded over. Volatilization fluxes were estimated using an aerodynamic-gradient technique immediately following the completion of the application process and continued for 9 d for the tarped field and 6 d for the nontarped field. The cumulative volatilization losses from the tarped field were 22% of the nominal application within the first 5 d of the experiment and about 32% of the nominal application within 9 d including the one day after the tarp was removed on Day 8 after application. In contrast, the nontarped field lost 89% of the nominal application by volatilization in 5 d. The volatilization rate from the tarped field was shown to be significantly lower than the nontarped field at a 95% confidence level.

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USGS1995

Prediction of areas where irrigation drainage may induce selenium contamination of water

The U.S. Department of the Interior has investigated 25 areas in the western USA to determine whether irrigation drainage has caused harmful effects on wildlife or has reduced subsequent beneficial uses of the water. A database of chemical analyses of water, sediment, and biota from the 25 areas was created and supplemented with geologic, climatologic, and hydrologic data. The data were evaluated to identify common features among study areas and principal factors that result in Se contamination of water in lakes, ponds, and streams downgradient of irrigated areas. From the analysis of data, a decision tree that uses readily available geologic, climatologic, and hydrologic data was derived for use by resource managers as a screening tool to predict the likelihood that irrigation drainage will result in Se contamination in areas of the western USA. Irrigation in areas that are not associated with marine sedimentary rocks of late Cretaceous age is unlikely to cause Se contamination. Irrigation in very arid areas that are associated with these Cretaceous sediments is almost certain to cause Se contamination if the irrigation water drains to terminal lakes and ponds. The likelihood that an area will be contaminated with Se because of irrigation drainage can change, particularly with changes in precipitation. During normal or wet periods, Se contamination may not occur in an area, even though it has seleniferous soils, but reduced water deliveries during a drought in such an area may result in Se contamination.

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USGS1995

Off-site movement of pesticide-contaminated fill from agrichemical facilities during the 1993 flooding in Illinois

Twenty retail agrichemical facilities were flooded. There was a concern that pesticide-contaminated road fill at these facilities had been transported into residential areas by the flooding. Forty fill and flood-related sediment samples were collected at six facilities. No significant accumulation of sediments was present at any of the six facilities. At five of the six facilities, it did not appear that road fill had been transported off-site. Pesticides were detected in sediment samples collected off-site adjacent to five of the facilities. Of the 21 samples collected off-site, atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazide) and metolachlor (2-chloro-6′-ethyl- N -(2-methoxy-1-methylethyl)acet- o -toluidine) were detected in 86 and 81% of the samples, respectively. When compared with on-site concentrations, off-site pesticide concentrations were either at similar levels, or were as much as three orders of magnitude less. The interpretation of the pesticide data was difficult and often inconclusive, because there were no background data on the occurrence and distribution of pesticides at each site before flooding.

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USGS1995

Pesticides in near-surface aquifers: An assessment using highly sensitive analytical methods and tritium

In 1992, the U.S. Geological Survey (USGS) determined the distribution of pesticides in near-surface aquifers of the midwestern USA to be much more widespread than originally determined during a 1991 USGS study. The frequency of pesticide detection increased from 28.4% during the 1991 study to 59.0% during the 1992 study. This increase in pesticide detection was primarily the result of a more sensitive analytical method that used reporting limits as much as 20 times lower than previously available and a threefold increase in the number of pesticide metabolites analyzed. No pesticide concentrations exceeded the U.S. Environmental Protection Agency's (USEPAs) maximum contaminant levels or health advisory levels for drinking water. However, five of the six most frequently detected compounds during 1992 were pesticide metabolites that currently do not have drinking water standards determined. The frequent presence of pesticide metabolites for this study documents the importance of obtaining information on these compounds to understand the fate and transport of pesticides in the hydrologic system. It appears that the 56 parent compounds analyzed follow similar pathways through the hydrologic system as atrazine. When atrazine was detected by routine or sensitive analytical methods, there was an increased likelihood of detecting additional parent compounds. As expected, the frequency of pesticide detection was highly dependent on the analytical reporting limit. The number of atrazine detections more than doubled as the reporting limit decreased from 0.10 to 0.01 µg/L. The 1992 data provided no indication that the frequency of pesticide detection would level off as improved analytical methods provide concentrations below 0.003 µg/L. A relation was determined between groundwater age and the frequency of pesticide detection, with 15.8% of the samples composed of pre-1953 water and 70.3% of the samples of post-1953 water having a detection of at least one pesticide or metabolite. Pre-1953 water is less likely to contain pesticides because it tends to predate the use of pesticides to increase crop production in the Midwest. Pre-1953 water was more likely to occur in the near-surface bedrock aquifers (50.0%) than in the near-surface unconsolidated aquifers (9.1%) sampled.

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USGS1996

Uncertainty of groundwater vulnerability assessments for agricultural regions in Hawaii: Review

There are important challenges associated with assessing potential groundwater vulnerability hazards that may result from regional scale applications of agrochemicals. The increasing availability of Geographic Information System (GIS) software to those involved in assisting with landuse decisions has resulted in the widespread production of multicolored risk management maps for many environmentally sensitive issues. Soil-based GIS's have recently been coupled to various solute-leaching models to make near-surface groundwater vulnerability assessments for guidance in pesticide regulation in several states. In general, these assessments rest on soil, climatic, and chemical data that are extremely sparse and contain considerable uncertainty. It is also important to acknowledge the uncertainty associated with the transport/fate processes that are not accounted for by the modeling approach used to make the assessment. In this paper, we review the results from a series of papers that have focused on characterization of uncertainty in pesticide mobility estimates, using the attenuation and retardation indices (AF and RF), for the Pearl Harbor Basin on the Hawaiian island of Oahu. Relative to data error uncertainties, we discuss the impacts of: (i) soil, climatic, and chemical data base uncertainties, (ii) reductions in data base uncertainties, (iii) extrapolation of soil data base information based on soil taxonomy and soil survey, and (iv) importing information from outside the region of interest. Relative to model error uncertainties, we compare pesticide leaching estimates from the simple AF and RF mobility indices with simulations from the EPA's Pesticide Root Zone Model (PRZM) and field observations. Finally, we outline a Regional Integrated Risk Assessment approach for characterizing regional scale groundwater vulnerability for near-surface nonpoint sources.

Hawaii↗

USGS1996

Movement of nitrate fertilizer to glacial till and runoff from a claypan soil

Although water from 20 to 25% of shallow farmstead wells in northern Missouri has concentrations of nitrate (NO3/-) exceeding 10 mg L-1 as nitrogen (N), many potential sources for this NO3/- are usually present. A field experiment was designed to trace and isolate the amount of a single application of N fertilizer lost to a glacial-till aquifer and runoff from a 400 m2 corn (Zea mays L.) plot with bromide (Br-) and isotopically labeled (15N) fertilizer. Soil at the plot is a Albaquic Hapludalf of the Adco Series containing a 61 cm claypan beneath 41 to 43 cm of topsoil. Groundwater levels ranged from 0.38 to 2.40 m below the land surface. Transport of water and NO3/- to the saturated zone was not substantially retarded by the claypan. Labeled-N fertilizer accounted for as much as 8.6 mg L-1 of the NO3/- (as N) in groundwater, but only in the top 1 to 2 m of the saturated zone. After two growing seasons (16 mo), <2% of the labeled-N fertilizer was lost to runoff, about 30% was in the saturated zone, 27.3% was removed with the grain, and about 5% remained in the unsaturated zone. A large part of the remaining labeled N may have been lost in gaseous N forms. The presence of labeled NO3/- only in the top 2 m of the aquifer, slow horizontal transport, and winter recharge indicate grass crops such as wheat (Triticum aestivum L.) or rye (Secale cereale L.) might be used to extract near- surface N during the winter recharge period. Also, fall fertilizations can be expected to readily leach. Because groundwater concentrations of labeled NO3/- were still increasing after two growing seasons, rotation of crops requiring small N inputs could be expected to limit the cumulative effect of large annual fertilizer applications on groundwater.

Journal of Environmental Quality↗

USGS1996

Atrazine concentrations in near-surface aquifers: A censored regression approach

In 1991, the U.S. Geological Survey (USGS) conducted a study to investigate the occurrence of atrazine (2-chloro-4-ethylamino-6- isopropylamino-s-triazine) and other agricultural chemicals in near-surface aquifers in the midcontinental USA. Because about 83% of the atrazine concentrations from the USGS study were censored, standard statistical estimation procedures could not be used. To determine factors that affect atrazine concentrations in groundwater while accommodating the high degree of data censoring. Tobit models were used (normal homoscedastic, normal heteroscedastic, lognormal homoscedastic, and lognormal heteroscedastic). Empirical results suggest that the lognormal heteroscedastic Tobit model is the model of choice for this type of study. This model determined the following factors to have the strongest effect on atrazine concentrations in groundwater: percent of pasture within 3.2 km, percent of forest within 3.2 km (2 mi), mean open interval of the well, primary water use of a well, aquifer class (unconsolidated or bedrock), aquifer type (unconfined or confined), existence of a stream within 30 m (100 ft), existence of a stream within 30 m to 0.4 km (0.25 mi), and existence of a stream within 0.4 to 3.2 km. Examining the elasticities of the continuous explanatory factors provides further insight into their effects on atrazine concentrations in groundwater. This study documents a viable statistical method that can be used to accommodate the complicating presence of censured data, a feature that commonly occurs in environmental data.

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USGS1997

Pesticides in the San Joaquin River, California: Inputs from dormant sprayed orchards

Rainfall-induced runoff mobilized pesticides to the San Joaquin River and its tributaries during a 3.8-cm rainstorm beginning the evening of 7 February and lasting through the morning of 8 Feb. 1993. Two distinct peaks of organophosphate pesticide concentrations were measured at the mouth of the San Joaquin River. These two peaks were attributed to contrasts between the soil texture, basin size, pesticide-use patterns, and hydrology of the eastern and western San Joaquin Valley. The fine soil texture and small size of the western tributary basins contributed to rapid runoff. In western valley streams, diazinon concentrations peaked within hours of the rainfall's end and then decreased because of a combination of dilution with pesticide-free runoff from the nearby Coast Ranges and decreasing concentrations in the agricultural runoff. Peak concentrations for the Merced River, a large tributary of the eastern San Joaquin Valley, occurred at least a day later than those of the western tributary streams. That delay may be due to the presence of well-drained soils in the eastern San Joaquin Valley, the larger size of the Merced River drainage basin, and the management of surface-water drainage networks. A subsequent storm on 18 and 19 February resulted in much lower concentrations of most organophosphate pesticides suggesting that the first storm had mobilized most of the pesticides that were available for rainfall-induced transport.

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USGS1997

Acidic deposition, cation mobilization, and biochemical indicators of stress in healthy red spruce

Dendrochemical and biochemical markers link stress in apparently healthy red spruce trees ( Picea rubens ) to acidic deposition. Acidic deposition to spruce forests of the northeastern USA increased sharply during the 1960s. Previous reports related visible damage of trees at high elevations to root and soil processes. In this report, dendrochemical and foliar biochemical markers indicate perturbations in biological processes in healthy red spruce trees across the northeastern USA. Previous research on the dendrochemistry of red spruce stemwood indicated that under uniform environmental conditions, stemwood concentrations of Ca and Mg decreased with increasing radial distance from the pith. For nine forest locations, frequency analysis shows that 28 and 52% of samples of red spruce stemwood formed in the 1960s are enriched in Ca and Mg, respectively, relative to wood formed prior to and after the 1960s. This enrichment in trees throughout the northeastern USA may be interpretable as a signal of increased availability of essential cations in forest soils. Such a temporary increase in the availability of Ca and Mg could be caused by cation mobilization, a consequence of increased acidic deposition. During cation mobilization, essential Ca and Mg as well as potentially harmful Al become more available for interaction with binding sites in the soil and absorbing roots. As conditions which favor cation mobilization continue, Ca and Mg can be leached or displaced from the soil. A measure of the interaction between Ca and Al is the Al/Ca binding ratio (molar charge ratio of exchangeable Al to exchangeable Ca). As the Al/Ca binding ratio in the root zone increased from 0.3 to 1.9, the foliar concentration of the biochemical stress marker putrescine also increased from 45 to 145 nm g −1 . The correlation of the putrescine concentration to the Al/Ca binding ratio (adj. r 2 = 0.68, P < 0.027) suggests that foliar stress may be linked to soil chemistry.

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USGS1997

Agricultural chemicals in groundwater of the midwestern United States: Relations to land use

To determine the relations between land use and concentrations of selected agricultural chemicals (nitrate, atrazine residue [atrazine (2-chloro-4-ethylamino-6-isopropylamino- s -triazine) + deethylatrazinc (2-amino-4-chloro-6-isopropylamino- s -triazine) + deisopropylatrazine (2-amino-4-chloro-6-ethylamino- s -triazine)], and alachlor residue [alachlor, [2-chloro-2′,6′-diethyl- N -(methoxymethyl) acetanilide] + alachlor ethanesulfonic acid (alachlor-ESA; 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethanesulfonic acid)] in groundwater, detailed land use information based on accurate measurements from aerial photographs for the 1991 growing season was obtained within a 2-km radius surrounding 100 wells completed in near-surface unconsolidated aquifers in the midwestern USA. The most significant land use factors to the agricultural chemicals examined were: nitrate (amount of irrigated crop production, positive relation), atrazine residue (amount of irrigated crop production, positive relation), and alachlor residue (amount of highly erodible land, inverse relation). The investigation of smaller buffer sizes (size of circular area around sampled wells) proved insightful for this study. Additional land use factors having significant relations to all three agricultural chemicals were identified using these smaller buffer radii. The most significant correlations (correlation maxima) generally occurred at ≤500-m for nitrate and ≥1000-m for atrazine residue and alachlor residue. An attempt to improve the statistical relations to land use by taking hydrologic considerations into account (removing land outside the estimated most probable recharge area from the statistical analysis) was not as successful as anticipated. Only 45% of the nitrate, 32% of the atrazine residue, and 20% of the alachlor residue correlations were improved by a consideration of the estimated most probable recharge area.

Journal of Environmental Quality↗

USGS1997

Assessing aquifer contamination risk using immunoassay: Trace analysis of atrazine in unsaturated zone sediments

The vulnerability of a shallow aquifer in south-central Kansas to contamination by atrazine (2-chloro-4-ethylamino-6-isopropylamines-triazine) was assessed by analyzing unsaturated zone soil and sediment samples from about 60 dryland and irrigated sites using an ultrasensitive immunoassay (detection level of 0.02 µg/kg) with verification by gas chromatography/mass spectrometry (GC/MS). Samples were collected at depths of 0 to 1.2 m (i.e., the root zone), 1.2 to 1.8 m, and 1.8 to 3.0 m during two time periods-prior to planting and after harvest of crops. About 75% of the samples contained detectable concentrations of parent atrazine. At the shallow sampling depth, atrazine concentrations ranged from 0.5 to approximately 12 µg/kg. Atrazine concentrations at the intermediate (1.2-1.8 m) depth generally were <1.0 µg/kg, with most of the concentrations <0.10 µg/kg, which suggests substantial degradation of parent atrazine in the root zone. Likewise, atrazine concentrations front the deepest (1.8-3.0 m) depth ranged from <0.02 to 0.33 µg/kg. The metabolite deethylatrazine (2-amino-4-chloro-6- isopropylamine-s-triazine) was detected by GC/MS only in 2 of 60 samples with concentrations of 1.4 and 1.5 µg/kg. The reconnaissance survey shows that, in spite of atrazine use ranging from 1 to 5 or more years, there does not appear to he a significant buildup of parent compound below the root zone. Therefore, the unsaturated zone does not appear to be a major storage compartment of atrazine contamination for the underlying shallow aquifer.

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USGS1997

Boron contents and isotopic compositions of hog manure, selected fertilizers, and water in Minnesota

Boron-isotope (δ 11 B) values may be useful as surrogate tracers of contaminants and indicators of water mixing in agricultural settings. This paper characterizes the B contents and isotopic compositions of hog manure and selected fertilizers, and presents δ 11 B data for ground and surface water from two agricultural areas. Boron concentrations in dry hog manure averaged 61 mg/kg and in commercial fertilizers ranged from below detection limits in some brands of ammonium nitrate and urea to 382 mg/kg in magnesium sulfate. Values of δ 11 B of untreated hog manure ranged from 7.2 to 11.2o/oo and of N fertilizers were −2.0 to 0.7o/oo. In 22 groundwater samples from a sand-plain aquifer in east-central Minnesota, B concentrations averaged 0.04 mg/L and δ 11 B values ranged from 2.3 to 41.5o/oo. Groundwater beneath a hog feedlot and a cultivated field where hog manure was applied had B-isotope compositions consistent with the water containing hog-manure leachate. In a 775-km 2 watershed with silty-loam soils in southcentral Minnesota: 18 samples of subsurface drainage from corn ( Zea mays L.) and soybean ( Glycine max L. Merr.) fields had average B concentrations of 0.06 mg/L and δ 11 B values of 5.3 to 15.1o/oo; 27 stream samples had average B concentrations of 0.05 mg/L and δ 11 B values of 1.0 to 19.0o/oo; and eight groundwater samples had average B concentrations of 0.09 mg/L and δ 11 B values of −0.3 to 23.0o/oo. Values of δ 11 B and B concentrations, when plotted against one another, define a curved mixing trend that suggests subsurface drainage and stream water contain mixtures of B from shallow and deep groundwater.

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USGS1997

Logistic model of nitrate in streams of the upper-midwestern United States

Nitrate in surface water can have adverse effects on aquatic life and, in drinking-water supplies, can be a risk to human health. As part of a regional study, nitrates as N (NO3-N) was analyzed in water samples collected from streams throughout 10 Midwestern states during synoptic surveys in 1989, 1990, and 1994. Data from the period immediately following crop planting at 124 sites were analyzed during logistic regression to relate discrete categories of NO3-N concentrations to characteristics of the basins upstream from the sites. The NO3-N data were divided into three categories representing probable background concentrations (<3 mg L-1), elevated concentrations (3-10 mg L-1), and concentrations that exceeded the U.S. Environmental Protection Agency maximum contaminant level (MCL) for drinking water (>10 mg L-1). Nitrate-N concentrations were positively correlated to streamflow, upstream area planted in corn (Zea mays L.), and upstream N- fertilizers application rates. Elevated NO3-N concentrations were associated with poorly drained soils and were weakly correlated with population density. Nitrate-N and streamflow data collected during 1989 and 1990 were used to calibrate the model, and data collected during 1994 were used for verification. The model correctly estimated NO3-N concentration categories for 79% of the samples in the calibration data set and 60% of the samples in the verification data set. The model was used to indicate where NO3-N concentrations might be elevated or exceed the NO3-N MCL in streams throughout the study area. The potential for elevated NO3-N concentrations was predicted to be greatest for streams in Illinois, Indiana, Iowa, and western Ohio.

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USGS1998

Relation between irrigation method, sediment yields, and losses of pesticides and nitrogen

Yields of suspended sediment from watersheds in the Quincy and Pasco Basins of Washington State have been reduced by the use of sprinkler irrigation on cropland previously in furrow irrigation. Mean daily yields of suspended sediment from nine watersheds sampled during April and May 1994 ranged from 0.4 kg/ha of irrigated cropland in a watershed with no furrow irrigation to 19 kg/ha in a watershed where 58% of irritated cropland was in furrow irrigation. About 67% of the variation in the yields can be attributed to irrigation method. Temporal trends also indicated that use of sprinkler irrigation reduced sediment yields. Mean daily yields of suspended solids from one of the watersheds decreased from 0.3 kg/ha in 1975 to <0.2 kg/ha in 1988, corresponding with a decrease from about 65% to <50% in the use of furrow irrigation. Sampling in two watersheds suggests that the use of sprinkler irrigation reduces runoff losses of pesticides and N. For 10 of 13 pesticides and N, runoff losses from a watershed with mostly furrow irrigation exceeded runoff losses from a watershed with mostly sprinkler irrigation.

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