Comparative Study of Transport Processes of Nitrogen, Phosphorus, and Herbicides to Streams in Five Agricultural Basins, USA

Abstract

Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly affected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland flow. In most cases, overland flow contributed the greatest loads, but a significant portion of the annual load of nitrate and some pesticide degradates can be transported under base‐flow conditions. The highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the effects of climate and geohydrologic conditions. The LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins.

Metolachlor metabolite (MESA) reveals agricultural nitrate-N fate and transport in Choptank River watershed

“…within the Lake Greifensee (Switzerland) epilimnion was 100-200 days (Huntscha et al, 2008). Finally, a similar transport process was responsible for MESA and nitrate-N delivery to streams in several US agricultural watersheds (Domagalski et al, 2008). Thus, because the major metabolite of metolachlor, MESA, is exceptionally stable and soluble, has a low K oc , and is formed in the unsaturated zone where nitrate-N is transported, it is an ideal transport analog for assessing the fate of agricultural nitrate-N.…”

“…Glutathione conjugation is the common detoxification method for metolachlor in plants (Cole, 1994;Field and Thurman, 1996) and for its microbial degradation pathway in soil unsaturated zones (Aga and Thurman, 2001;Aga et al, 1996;Aly and Schröder, 2008;Domagalski et al, 2008). In both plant and microbial degradation, glutathione-S-transferase mediates glutathione nucleophilic substitution at the chlorinated carbon of metolachlor.…”

“…Like nitrate-N, MESA is very soluble (2.12*10 5 mg/L) (Bayless et al, 2008), has a low sorption coefficient (calculated log K oc = 1.13) (Bayless et al, 2008), and has been classified as highly mobile Domagalski et al, 2008;Huntscha et al, 2008). In contrast to nitrate-N, once MESA enters ground water, it is very stable (Phillips Table 1 Conceptual model of landscape characteristics that influence transport, processing, and delivery of nitrate-N and MESA to headwater streams of the Choptank River (Ator et al, 2005;Bachman and Phillips, 1996;Denver et al, 2010, in press;Phillips and Bachman, 1996;Phillips et al, 1993 Steele et al, 2008); MESA persists over decadal time scales (Denver et al, 2010).…”

Suburban Groundwater Quality as Influenced by Turfgrass and Septic Sources, Delmarva Peninsula, USA

“…The USEPA's TMDLs require states and local governmental agencies to decrease or limit the total loads of contaminants to water bodies from both point and nonpoint sources to achieve water-quality standards (e.g., Delaware Department of Natural Resources and Environmental Control, 1998). Groundwater discharge is the primary source of N to streams on the Delmarva Peninsula, providing as much as 70% of the N flux, predominantly as nitrate (Ator and Denver, 2012;Domagalski et al, 2008).…”

Recycling Vertical-Flow Biofilter: A Treatment System for Agricultural Subsurface Tile Water

“…A study of tile drain outlets in southwestern Ohio found an average concentration of nitrate-N of 17 mg L -1 was discharged to receiving waters (Fleming et al, 1998). The crop production system employed, the amount, rate, and timing of fertilizer application, the size and arrangement of drainage tiles, and the presence of cover crops are all known to influence nitrogen inputs to surface waters from tile drainage systems (Kaspar et al, 2007;Kladivko et al, 2004;Nangia et al, 2008;deVos et al, 2000;Domagalski et al, 2008;Dinnes et al, 2002). Agronomic controls such as crop and fertilizer management, however, are not usually sufficient to rectify nutrient pollution resulting from tile drainage systems (Jaynes et al, 2008;Madramootro et al, 2007).…”