Twenty‐two aseptically collected sediment core samples were obtained from below the water table (60 to 280 feet deep) at four pristine sites along a major buried‐valley aquifer system in northeastern Kansas. Samples were examined for total numbers of bacteria, viable aerobic bacteria, protozoa, and fungi. Contiguous samples were obtained in some transition zones of sediment texture or color in order to detect possible population shifts over small vertical distances related to changes in sediment characteristics. Total counts of bacteria varied between 106 and 108 per gram of dry sediment. Viable bacterial counts varied between 0 and 108 colony forming units per gram, usually being higher in sandy or gravelly sediments than in silty or clayey sediments. The relationship between sediment texture and microbial population density was confirmed statistically. Total numbers of bacteria correlated highly with variations in sediment sand and clay content. The population densities of viable bacteria and protozoa correlated moderately with these indicators of sediment texture. In some samples, populations of viable bacteria approached the total count of bacteria and the diversity of bacterial colony types appraoched that found in surface soil. Protozoa were found at low population densities in the coarser textured samples. The protozoa were similar to types commonly encountered in surface soil. No actinomycetes, fungi, or algae were detected in any samples.
Glacial buried‐valley aquifers serve as primary sources of potable ground water in northeastern Kansas. A long known problem, however, is that a large percentage of well waters in this region exceed the U.S. Environmental Protection Agency (EPA) limits for nitrate (NO−3). A detailed study of the hydrogeology and water quality of the buried valleys has confirmed the nitrate problem and led to a recognition that some well waters with low ( 5 mg/l) NO−3 concentrations have anomalous ( 0.5 mg/l) ammonium ion (NH+4) levels, with an NH+4 range from <0.1 to 4.8 mg/l. The extractable NH+4 concentrations in related glacial sediments range up to approximately 75 mg/kg, and the amounts generally increase from an average of 2 mg/kg in the topsoil downward to bedrock. Migration of brines from subjacent Permian or Pennsylvanian bedrock into the unconsolidated sediments locally may cause desorption of NH+4 and an increase in its levels in the associated ground waters. Numerous test holes drilled in the study area showed a black scum on the fluid and cuttings, which may be from buried humic materials. Recently measured total organic carbon (TOC) contents of the ground waters confirm a significant level in some areas, with a range from 0.1 to 2.4 mg/l as C. Chlorination of water with dissolved organics may lead to production of halogenated compounds. Two public‐water‐supply well waters contained total trihalomethane (TTHM) levels close to the maximum contaminant level (MCL) of 100 /μg/l in chlorinated samples quenched after one week. The presence of NH+4 inhibits the formation of THMs, but it also can give rise to odor and taste problems in the finished water. The inhibition of THM formation by NH+4 is achieved by reactions which compete with the organics for combination with chlorine. These reactions make maintaining appropriate chlorine residuals difficult and also may lead to production of undesirable side products. Present efforts to evaluate the regional water‐quality problems are focused in Nemaha County, Kansas.
Aquifers found in glacial buried valleys are a major source of good‐quality ground water in northeastern Kansas. The extent and character of many of these deposits are not precisely known, so a detailed study of the buried valleys was undertaken. Test drilling, Landsat imagery, shallow‐earth temperature measurements, seismic refraction, surface electrical resistivity, and gravity data were used to evaluate two sites in Nemaha and Jefferson Counties. Tonal patterns on springtime Landsat imagery and winter/summer anomalies in shallow‐earth temperatures were quick and inexpensive methods for locating some glacial buried aquifers and suggested areas for more intensive field studies. Reversed seismic refraction and resistivity surveys were generally reliable indicators of the presence or absence of glacial buried valleys, with most depth determinations being within 25% of test‐drilling results. The effectiveness of expensive test‐hole drilling was greatly increased by integrating remote sensing, shallow‐earth temperature, seismic, and resistivity techniques in the two buried valley test areas. A gravity profile allowed precise definition of the extent of one of the channels after the other techniques had been used for general information.
Fifty wells in Kansas were sampled to determine the concentrations of total organic carbon (TOC) and trihalomethane formation potential (THMFP) associated with major aquifer systems. The mean TOC and THMFP concentrations were 1.03 ± 0.76 mg/L and 46.7 ± 39.5 μg/L, respectively; THMFP was very strongly correlated with TOC (r = 0.953). Only 8 percent of the THMFP concentrations exceeded 100 μg/L, but 56 percent exceeded 25 μg/L and 90 percent exceeded 10 μg/L, suggesting that many Kansas water utilities using groundwater might have difficulty meeting a substantially lower THM standard. Efforts to control THMs in Kansas groundwater supplies should focus on alluvial aquifers, particularly those with high concentrations of TOC, ammonium, iron, and manganese.
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