Hydrogeochemistry in regional aquifer systems supports agricultural water quality investigations in Iowa

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5815701

Simpkins, W W; Ariffin, A R; Qui, Z ^[1]

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1. Iowa State Univ., Ames, IA (United States). Dept. of Geological and Atmospheric Sciences

In this study, the authors demonstrate conjunctive use of traditional water quality data with environmental isotopes and geochemistry to determine whether present or future application of chemicals at the land surface will affect water quality in deep aquifers. The study area is located in central Iowa in the Walnut Creek Basin, one of three USDA-CSRS Management System Evaluation Area (MSEA) sites in Iowa. Pre-Illinoian gravel, Pennsylvanian sandstone, and Mississippian limestone comprise the major aquifers in this area and they are overlain by at least 50 m of late Wisconsin and Pre-Illinoian glacial sediments. Well depths, water levels, and aquifer units were identified by well construction logs followed by a house-to-house survey of residents. A subset of 125 total wells was sampled for major ions, trace metals, H-3, delta O-18, delta H-2, delta C-13, and C-14-DIC. Results suggest that contamination of deep aquifers from agricultural practices in the basin is unlikely. First, data from this study and the Till Hydrology Site to the northwest suggest that vertical groundwater velocities through the Pre-Illinoian till are too low for recent vertical recharge to reach the aquifers. Second, H-3 and corrected C-14 dates suggest that groundwater recharged both vertically and at outcrop is at least 13,000 years old and may be > 40,000 years old. Third, the groundwater in these aquifers is anaerobic and contains high Fe concentrations, SO[sub 4] concentrations < 1 mmol/L, CH[sub 4] gas, and delta C-13 DIC values between 0.0 and [minus]21.9 [per thousand]. The processes involved suggest a geochemical environment unfavorable for persistence of NO[sub 3]. In contrast, water samples from some wells suggest that some contamination may occur through poorly-constructed wells or deteriorating well casing.

• OSTI ID: 5815701
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540250* -- Environment
Terrestrial-- Site Resource &amp; Use Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
AGE ESTIMATION
AGRICULTURE
AQUIFERS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 13
CARBON 14
CARBON ISOTOPES
CARBONATE ROCKS
CHEMISTRY
DEUTERIUM
DEVELOPED COUNTRIES
ELEMENTS
ENVIRONMENTAL QUALITY
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOCHEMISTRY
GLACIERS
GROUND WATER
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROLOGY
IOWA
ISOTOPES
LAND USE
LIGHT NUCLEI
METALS
NITRATES
NITROGEN COMPOUNDS
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
RADIOISOTOPES
RECHARGE
ROCKS
SEDIMENTARY ROCKS
SEDIMENTS
STABLE ISOTOPES
TRACE AMOUNTS
TRITIUM
USA
WATER
WATER QUALITY
YEARS LIVING RADIOISOTOPES