Occurrence of Selected Herbicides and Herbicide Degradation Products in Iowa's Ground Water, 1995

Abstract

Herbicide compounds were prevalent in ground water across Iowa, being detected in 70% of the 106 municipal wells sampled during the summer of 1995. Herbicide degradation products were three of the four most frequently detected compounds for this study. The degradation product alachlor ethanesulfonic acid was the most frequently detected compound (65.1%), followed by atrazine (40.6%), and the degradation products deethylatrazine (34.9%), and cyanazine amide (19.8%). The corn herbicide acetochlor, first registered for widespread use in the United States in March 1994, was detected in a single water sample. No reported herbicide compound concentrations for this study exceeded currem U.S. Environmental Protection Agency's maximum contaminant levels or health advisory levels for drinking water, although the herbicide degradation products examined have yet to have such levels established. The occurrence of herbicide compounds had a significant, inverse relation to well depth and a significant, positive relation to dissolved‐oxygen concentration. It is felt that both well depth and dissolved oxygen are acting as rough surrogates to ground‐water age, with younger ground water being more likely to contain herbicide compounds. The occurrence of herbicide compounds was substantially different among the major aquifer types across Iowa, being detected in 82.5% of the alluvial, 81.8% of the bedrock/ karst region, 40.0% of the glacial‐drift, and 25.0% of the bedrock/nonkarst region aquifers. The observed distribution was partially attributed to variations in general ground‐water age among these aquifer types. A significant, inverse relation was determined between total herbicide compound concentrations in ground water and the average soil slope within a 2‐km radius of sampled wells. Steeper soil slopes may increase the likelihood of surface runoff occurring rather than ground‐water infiltration–decreasing the transport of herbicide compounds to ground water. As expected, a significant positive relation was determined between intensity of herbicide use and herbicide concentrations in ground water.

Persistence of pharmaceutical compounds and other organic wastewater contaminants in a conventional drinking-water-treatment plant

“…This finding demonstrates the importance of analyzing for degradates in order to understand fully the fate of OWCs in a DWT facility as well as the potential human-health issues associated with chronic exposure to these compounds through drinking water. For other classes of organic compounds, such as pesticides, the importance of analyzing for degradates is well established (Thurman et al, 1994;Kolpin et al, 1997;Kalkhoff et al, 1998;Graham et al, 1999;Kolpin et al, 2001). The absence of many OWCs in finished-water supplies, therefore, does not necessarily imply their complete removal from finished water.…”

Stimulation of aerobic degradation of bentazone, mecoprop and dichlorprop by oxygen addition to aquifer sediment

“…Groundwater contamination with herbicides from diffuse sources is widespread, but it is usually at low concentrations in the nano-to microgram per litre concentration range (Kolpin et al, 1995;2000;Thorling et al, 2012). This limits the possibilities for remedial actions in contrast to contamination from a point source characterized by higher concentrations, smaller volumes and distinct plumes (Tuxen et al, 2006a).…”

Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes

“…Due to its widespread use, long-term persistence in soil, greater leaching potential and relatively high solubility in water, atrazine is frequently detected in ground, surface and drinking waters [2,3]. Although atrazine is toxic to animals [4] and humans [5] and its use has been banned in European Union countries since 2003 [6], this chlorotriazine herbicide still remains in use in China.…”