Agreement Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the USDA or the Mississippi Agricultural and Forestry Experiment Station and does not imply its approval to the exclusion of other products that may also be suitable.
Water samples from 240 private wells in rural Illinois were collected over one year and analyzed for 39 agricultural chemicals. Sampling was conducted to provide preliminary information to refine a plan for a statewide survey of the agricultural chemical contamination of rural private wells. Wells were sampled according to a stratified random sampling plan that included four classes of depth lo the uppermost aquifer material and two classes of well type. Depth lo uppermost aquifer material was defined as the depth from ground surface to a geologic material that, if saturated, could he used as an aquifer. Occurrence, defined as the presence of one or more target analytes in a well water sample above some specified concentration, was shown to be higher in large‐diameter bored or dug wells than in small‐diameter drilled wells. For small‐diameter wells, occurrence generally decreased as the depth to the uppermost aquifer material increased, In addition, depth to the uppermost aquifer material could be used to predict the occurrence of some individual agricultural chemicals, such as nitrate and atrazine, but could not be used to predict the occurrence of pielorarn or pesticides in small‐diameter wells. Of the 39 target analytes, 10 were detected at concentrations exceeding their respective minimum reporting levels. Nitrate and atrazine were the only compounds found at concentrations exceeding their respective maximum contaminant levels (MCLs) or U.S. EPA lifetime health advisory limits (HAI.s). A nonparametric statistical technique, contingency table analysis, identified factors associated with the occurrence of agricultural chemicals in three of the file study areas. Elevated specific conductance (>500 μmhos/cm) of the sampled water was strongly associated with the occurrence of agricultural chemicals. This association was common to all three study areas analyzed. Identification of the source of the specific conductance could help identify the dominant pathway for transport of agricultural chemicals to ground water.
Studies of polybrominated biphenyl (PBB) uptake by plants have been conducted in hydroponic solutions and in greenhouse experiments with soil. Autoradiograms of corn and soybean seedlings grown in hydroponic solutions showed no translocation of 14C-PBB from 14C-PBB-treated solutions to plant tops or within the leaf from 14C-PBB-treated spots on the upper leaf surface. A significant portion of the 14C-PBB associated with the roots was removed when the roots were dipped in acetone. Three root crops (radishes, carrots, and onions) were grown in two soils, each treated with a mixture of FireMaster BP-6 (PBB) and 14C-PBB to achieve final concentrations of 100 ppm and 100 ppb. All roots showed more PBB when grown in the soil with the lower clay and organic matter content than they did when grown in the soil with more clay and organic matter. In the latter soil (clay loam) no PBB was detected in any roots from the 100 ppb treatment. More PBB was associated with roots of carrot than of radish or onion. Corn leaf whorls containing dust from a PBB contamination soil and washed radishes from a heavily contaminated garden showed no PBB.ImagesFIGURE 1.FIGURE 2.FIGURE 3.FIGURE 4.
Soil samples were collected from 28 fields which had received manure from Michigan's most highly contaminated dairy herds. The number of fields in each concentration range of PBB in soil were: 2, not detectable; 15, 0.0 to 8.0 ppb; 6, 14-102 ppb, and 5, 153 to 371 ppb. Plant tissue sampled from the 10 most highly contaminated fields contained no detectable PBB. No evidence of significant degradation of PBB was noted after 1 year incubation in soil. When 14C hexabromobiphenyl and heptabromobiphenyl isomers were incubated in soil less than 0.2% of the 14C was volatilized. Also gas chromatographic analysis of soil extracts showed no difference in recovery of the six major PBB isomers between sterilized and nonsterilized soil. Analysis of these extracts by thin layer chromatography and autoradiography showed no 14C-PBB intermediates. Photodegradation products of the major hexa- and heptabromobiphenyl isomers showed more but still minor (approximately 3%) biodegradation in soil. Much of the photodegradation products appeared bound to soil, since these products could not be extracted from soil. Photodegradation does not appear to be a significant fate of PBB in manures spread on fields since no change was noted in the relative concentrations of isomers in soil samples from our field survey. Studies with distilled, tap, river, and soil waters showed that PBB solubility was markedly influenced by water composition.ImagesFIGURE 1.FIGURE 2.
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