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Mark E. Savoca

Publications and source records attributed to Mark E. Savoca.

25 records · Page 2Linked to original sources
USGS2000

Water-quality assessment of the Eastern Iowa Basins: Hydrologic and biologic data, October 1996 through September 1998

Hydrologic and biologic data collected from October 1996 through September 1998 in the Eastern Iowa Basins study unit of the U.S. Geological Survey National Water-Quality Assessment Program are presented in this report. Monthly data collected from 12 sites on rivers and streams included measurements of physical properties and determinations of the concentrations of nutrients, major ions, organic carbon, trace elements, suspended sediment, and dissolved pesticides. Fish-tissue samples were collected at two sites in September 1997 and analyzed for organochlorine pesticides. In addition, water-quality assessments were made at 25 sites as part of a synoptic study in August 1997 and May 1998. A ground-water study was conducted to evaluate the effects of agricultural and urban land use on the water quality of shallow alluvial aquifers in the study unit. Samples were collected and analyzed from wells in 31 agricultural and 30 urban land-use areas during June-August 1997. Samples were collected and analyzed from 32 domestic wells during June-July 1998 to provide a broad assessment of the water quality of shallow alluvial aquifers throughout the study unit. Samples were collected during August 1998 from 27 shallow monitoring wells completed in the Iowa River alluvial aquifer to evaluate the effects of changing land use on shallow ground-water quality. Ground-water samples were analyzed for physical properties, nutrients, major ions, organic carbon, trace elements, dissolved pesticides, volatile organic compounds, radon-222, and tritium.

Iowa↗
USGS2000

Effects of land use and hydrogeology on the water quality of alluvial aquifers in eastern Iowa and southern Minnesota, 1997

Ground-water samples were collected from monitoring wells at 31 agricultural and 30 urban sites in the Eastern Iowa Basins study unit during June–August 1997 to evaluate the effects of land use and hydrogeology on the water quality of alluvial aquifers. Ground-water samples were analyzed for common ions, nutrients, dissolved organic carbon, tritium, radon-222, pesticides and pesticide metabolites, volatile organic compounds, and environmental isotopes. Calcium, magnesium, and bicarbonate were the dominant ions in most samples and were likely derived from solution of carbonate minerals (calcite and dolomite) present in alluvial detrital deposits. Chloride and nitrate were dominant anions in samples from several wells. Sodium and chloride concentrations were significantly higher in samples from urban areas, where roads are more numerous and road salts may be more frequently applied, than in agricultural areas. Nitrate was detected in 94 percent of samples from agricultural areas and 77 percent of samples from urban areas. Nitrate concentrations were significantly higher in agricultural areas than in urban areas and exceeded the U.S. Environmental Protection Agency maximum ontaminant level for drinking water (10 milligrams per liter as N) in 39 percent of samples from agricultural areas. Nitrate concentrations in samples from urban areas did not exceed the maximum contaminant level. Greater use of fertilizers in agricultural areas most likely contributes to higher nitrate concentrations in samples from those areas. Tritium-based ages indicate ground water was most likely recharged after the 1950’s at all but one sampling site. Agricultural and urban land-use areas have remained relatively stable in the study area since the 1950’s; therefore, the effects of current land use should be reflected in ground water sampled during this study. Radon-222 was detected in all samples and exceeded the U.S. Environmental Protection Agency’s previously proposed maximum contaminant level for drinking water (300 picocuries per liter) in 71 percent of samples. Pesticides were detected in 84 percent of samples from agricultural areas and 70 percent from urban areas. Atrazine and metolachlor were the most frequently detected pesticides in samples from agricultural areas; atrazine and prometon were the most frequently detected pesticides in samples from urban areas. None of the pesticide oncentrations exceeded U.S. Environmental Protection Agency maximum contaminant levels or lifetime health advisories for drinking water. Pesticide metabolites were detected in 94 percent of samples from agricultural areas and 53 percent from urban areas. Metolachlor ethane sulfonic acid and deethylatrazine were the most frequently detected metabolites in samples from agricultural areas; metolachlor ethane sulfonic acid and alachlor ethane sulfonic acid were the most frequently detected metabolites in samples from urban areas. Total metabolite concentrations were significantly higher in samples from agricultural areas than in samples from urban areas. Total pesticide concentrations (parent compounds) tended to be higher in samples from agricultural areas; however, this difference was not statistically significant. Metabolites constituted the major portion of the total residue concentration in the alluvial aquifer. Volatile organic compounds were detected in 40 percent of samples from urban areas and 10 percent from agricultural areas. Methyl tertbutyl ether was the most commonly detected volatile organic compound and was present in 23 percent of samples from urban areas. Elevated concentrations (greater than 30 micrograms per liter) of methyl tert-butyl ether and BTEX compounds (benzene, toluene, ethylbenzene, and xylene) in two samples from urban areas suggest the possible presence of point-source gasoline leaks or spills. Factors other than land use may contribute to observed differences in water quality between and within agricultural and urban areas. Nitrate, atrazine, deethylatrazine, and deisopropylatrazine concentrations were significantly higher in shallow wells with sample intervals nearer the water table and in wells with thinner cumulative clay thickness above the sample intervals. These relations suggest that longer flow paths allow for greater residence time and increase opportunities for sorption, degradation, and dispersion, which may contribute to decreases in nutrient and pesticide concentrations with depth. Nitrogen speciation was influenced by redox conditions. Nitrate concentrations were significantly higher in ground water with dissolved-oxygen concentrations in excess of 0.5 milligram per liter. Ammonia concentrations were higher in ground water with dissolved-oxygen concentrations of 0.5 milligram per liter or less; however, this relation was not statistically significant. The amount of available organic matter may limit denitrification rates. Elevated nitrate concentrations (greater than 2.0 mg/L) were significantly related to lower dissolved organic carbon concentrations in water samples from both agricultural and urban areas. A similar relation between nitrate concentrations (in water) and organic carbon concentrations (in aquifer material) also was observed but was not statistically significant.

Iowa, Minnesota↗
USGS1999

Water-quality assessment of the eastern Iowa basins: Data, September 1995 through September 1996

The U.S. Geological Survey began data-collection activities in the Eastern Iowa Basins study unit of the National Water-Quality Assessment Program in September 1995 with the purpose of determining the status and trends in water quality. Surface-water data were collected, beginning in March 1996, on a monthly basis with occasional extra high- and low-flow samples. Data collected from 12 sites on rivers and streams in the study unit included determinations of the physical properties and concentrations of nutrients, major ions, organic carbon, trace elements, suspended sediment, and dissolved pesticides. Data collected at four additional sites included physical parameters and determination of the concentration of dissolved pesticides. In addition, bed-sediment and fish-tissue samples were collected at 16 sites and analyzed for trace elements and hydrophobic pesticides. There were two ground-water studies conducted in June and July 1996. The first looked at the quality of ground water in the Silurian-Devonian and Upper Carbonate aquifers and sampled 33 wells once, and the second examined the effects of agriculture on shallow ground water of the Iowa River alluvial aquifer and sampled 23 wells once. Ground-water samples were analyzed for physical properties, nutrients, major ions, organic carbon, trace elements, dissolved pesticides, and volatile organic compounds.

Iowa, Minnesota↗
USGS1999

Ground-water quality in the eastern part of the Silurian-Devonian and upper Carbonate aquifers in the eastern Iowa basins, Iowa and Minnesota, 1996

Ground-water samples were collected from 33 domestic wells to assess the water quality of the eastern part of the Silurian-Devonian and Upper Carbonate aquifers in the Eastern Iowa Basins National Water-Quality Assessment Program study unit. Samples were collected during June and July 1996 and analyzed for major ions, nutrients, pesticides and pesticide metabolites, volatile organic compounds, tritium, radon222, and environmental isotopes. Calcium, magnesium, and bicarbonate were the dominant ions in most samples and were likely derived from the solution of carbonate minerals (calcite and dolomite) present in the aquifer materials. The dominance of sulfate in samples from several wells suggests the dissolution of evaporite minerals. Ammonia and orthophosphorus were the most commonly detected nutrients. Nitrate was detected in about half of the samples and exceeded the U.S. Environmental Protection Agency maximum contaminant level (10 milligrams per liter) in 6 percent of samples. Atrazine and metolachlor were the only pesticides detected and were present in 18 percent and 12 percent of samples, respectively. Alachlor ethanesulfonic acid and deethylatrazine were the most commonly detected pesticide metabolites and were present in 16 percent and 9 percent of samples, respectively. Radon-222 was detected in all samples, and 47 percent had concentrations in excess of the U.S. Environmental Protection Agency previously proposed maximum contaminant level (300 picocuries per liter). Radon-222 concentrations were significantly higher in samples from wells that produced recently recharged water. This relation suggests that uranium-bearing glacial deposits (Schumann, 1993) may be a source of radon-222 in the underlying aquifers. The presence of regional confining units and thick overlying Quaternary-age deposits have an effect on water quality in the Silurian-Devonian and Upper Carbonate aquifers in the study area. Tritium-based ground-water ages were significantly older, and dissolved-solids concentrations were significantly higher in relatively well protected areas (where the aquifers are overlain by a bedrock confining unit or more than 100 feet of Quaternary-age deposits). Ammonia concentrations were significantly higher in relatively well protected areas and in samples from wells that produced older water. Higher ammonia concentrations also were observed in ground water with dissolved-oxygen concentrations of 0.5 milligram per liter or less, allowing for the anaerobic reduction of nitrate to ammonia. Nitrate concentrations were significantly higher in relatively poorly protected areas (where the aquifers are not overlain by a bedrock confining unit or are overlain by less than 100 feet of Quaternaryage deposits) and in samples from wells that produced recently recharged water. Pesticide and metabolite concentrations were significantly higher in samples from wells that produced recently recharged water. Atrazine, metolachlor, and deethylatrazine were not detected in any samples from relatively well protected areas of the aquifers.

Iowa, Minnesota↗
USGS1997

Herbicides and nitrates in the Iowa River alluvial aquifer prior to changing land use, Iowa County, Iowa, 1996

The Iowa River alluvial aquifer in Iowa County, Iowa (fig. 1), underlies an area of intensive agricultural activity where pesticides and nitrogen-based fertilizers are extensively used. The effects of changing land use on shallow ground-water quality in part of the Iowa River alluvial aquifer are currently being investigated as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Approximately one-third of the cropland in the study area will be taken out of production over the next few years as part of wetland restoration. Over a three-week period in 1996, the USGS collected water samples from 23 observation wells completed in the Iowa River alluvial aquifer and analyzed the samples for selected agricultural chemicals. Four herbicides (alachlor, atrazine, cyanazine, and metolachlor) and one nutrient (nitrate) were selected for study on the basis of frequent usage in Iowa and high detection rates in ground water (Detroy and Kuzniar, 1988). Alachlor was not detected at concentrations greater than the method detection limit (MDL). Atrazine was detected at concentrations greater than the MDL in samples from 48 percent of the 23 wells, cyanazine from 13 percent, metolachlor from 26 percent, and nitrate from 91 percent. None of the four herbicides were detected at concentrations greater than the respective U.S. Environmental Protection Agency's (USEPA) Maximum Contaminant Level (MCL) for drinking water. Thirteen percent of the samples had nitrate concentrations above the USEPA's MCL of 10 mg/L (milligrams per liter). Relations between constituent concentration and well depth were observed for specific constituents at individual well nests.

Iowa↗