Transport and persistence of pesticides in alluvial soils. I. Simazine

• Published in: Journal of environmental quality 1998-05, Vol.27 (3), p.543-550
• Main Authors: Cogger, C.G. (Washington State Univ., Puyallup, WA.), Bristow, P.R, Stark, J.D, Getzin, L.W, Montgomery, M
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; ALLUVIAL SOILS; Applied sciences; Biological and medical sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; FRAGARIA ANANASSA; Fundamental and applied biological sciences. Psychology; GROUNDWATER POLLUTION; Groundwaters; Herbicides; LEACHING; LESSIVAGE DU SOL; LIXIVIACION; Natural water pollution; Pesticides; Pollution; POLLUTION DE L'EAU SOUTERRAINE; Pollution, environment geology; POLUCION DE AGUAS SUBTERRANEAS; RUBUS IDAEUS; SIMAZINA; SIMAZINE; Soil and sediments pollution; Soil and water pollution; Soil science; SOL ALLUVIAL; SUELO ALUVIAL; WASHINGTON; Water treatment and pollution
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq1998.00472425002700030010x

Pesticide leaching is a concern in the alluvial valleys of western Washington, where high-value crops are grown in soils with water tables 3 m deep. We conducted this project to determine the long-term leaching pattern of simazine [2-chloro-4,6-bis-(ethylamino)-s-triazine] applied to red raspberry (Rubus idaeus L.) and strawberry (Fragaria x ananassa Duch.). Simazine was applied to strawberry and raspberry in paired plots at two sites. Strawberry received a split application (total 2.2 kg ha-1) in August and November, and raspberry received a single 4.5 kg ha-1 application in November. We applied simazine yearly from 1986 to 1989, and sampled soil (to 180 cm) and shallow groundwater monthly until April 1991, and at one site again in 1994. Most of the simazine remained in the surface 15 cm of the soil or degraded, but small amounts moved downward. Preferential flow soon after application was not the main cause of downward movement. Simazine was persistent, with disappearance half lives of 128 and 175 d at the two sites the first year. Some simazine remained in the soil 4 yr after the final application. Simazine was most mobile beneath raspberry at one site. This site had finer texture and slightly more organic matter, but a lower K4 for simazine than the other site. Small amounts of simazine reached shallow groundwater beneath both crops. The observed simazine leaching peak was more asymmetric than the peak predicted by the PRZM-2 model, an indication of nonequilibrium adsorption-desorption effects on simazine movement