Leaching of Diuron, Linuron and their main metabolites in undisturbed field lysimeters

Abstract

The increasing use of pesticides in Morocco raises the potential risk of groundwater contamination, notably in the Gharb area, which has a shallow groundwater table. Thus, the leaching of two phenyl-ureas, diuron and linuron and their metabolites through undisturbed soil columns was studied under outdoor conditions. The soil chosen is a loamy clay soil, representative of the Gharb agricultural area. After four irrigation events were applied from 31/03/2005 to 15/05/2005, leachates contained higher amounts of linuron (from 0.08% to 6.96% of applied linuron) than diuron (from 0% to 0.27%). The greater mobility of linuron might be related to its higher water solubility (64 mg x L(- 1) compared with 42 mg x L(- 1) for diuron) and smaller adsorption coefficient (K(oc) of 400 L x kg(- 1), compared with 480 L x kg(- 1) for diuron). Concerning their metabolites, greater amounts of, N'-(3,4-dichlorophenyl)-N, (DCPMU) than N'-3,4-dichlorophenylurea (DCPU) were detected N-dimethylurea in the percolates, from 0% to 0.046% and from 0% to 0.008%, respectively. At the end of the monitoring period, more linuron residues than diuron residues were recovered in the soil profiles, 25.02% and 16.41%, respectively. The diuron residues were found mainly in the 0-20 cm soil layer, whereas linuron residues reached the 20-40 cm soil layer. Under such experimental conditions, linuron leaching, and thus its potential to contaminate groundwater, is greater than that of diuron.

Adsorption-desorption and leaching behavior of diuron on selected Kenyan agricultural soils

“…Noteworthy, diuron is classified as a known carcinogenic compound (US-EPA, 1999). Owing to its stability in the environment (Dores et al, 2009), groundwater contamination by diuron has been reported as a significant environmental concern in Brazil (Ellmache et al, 2009). Similar findings have been reported in Dutch coastal waters (Lamoree et al, 2002) as well as in France (IFEN, 2002) and the United Kingdom (UK-EPA, 2002).…”

Adsorption and desorption behavior of herbicide diuron on various Chinese cultivated soils

“…Dores's research [8] showed that diuron was detected in concentration decreasing until 70 days after application in runoff water and soil, totalizing 13.9% during the whole sampling period. Because of its high persistence, groundwater contamination by diuron has become a serious problem [9]. In Dutch coastal waters a higher level of diuron than the permitted 430 ng L −1 was detected [10].…”

Urea Pesticides

“…Sample pretreatment processes are crucial steps to achieve clean-up and effective enrichment of the target analytes before analysis. For solid samples, traditionally, Soxhlet and manual/mechanical shaking have been used for ureas extraction (Buszewski et al, 2006;Cydzik et al, 2007;El Imache et al, 2009;Ghanem et al, 2008;Mou et al, 2008;Scheyer et al, 2005;Tamayo et al, 2005a, b;Tamayo & Martin-Esteban, 2005). On the other hand, for aqueous samples the classical methodology is liquid-liquid extraction (Moros et al, 2005).…”