Spatial and Temporal Trends of Paraquat, Diquat, and Difenzoquat Contamination in Water from Marsh Areas of the Valencian Community (Spain)

Abstract

The levels and distribution of diquat, paraquat, and difenzoquat were determined by solid phase extraction (SPE) and high-performance liquid chromatography (HPLC) in water samples from irrigation channels, rivers, and lagoons taken during 1 year from three different marsh areas of the Valencian community. These areas are representative of the typical Mediterranean coastal ecosystems. All three compounds were detected. Diquat was found most frequently at all the sampling sites. Although the spatial distribution of diquat and paraquat showed a maximum concentration near the fields where they were originally applied, their location fluctuated due to irregular large spill and/or loading. The herbicide concentration tended to be highest during the summer (June, July, and August) because these are the months with the least rainfall and highest evaporation rates, when weeds grow best and pesticides are needed more often. The average concentration found for diquat was 0.09 &mgr;g/L, with a maximum of 3.10 &mgr;g/L. The average concentration for paraquat was 0.01 &mgr;g/L, with a maximum of 3.95 &mgr;g/L. Samples that were below the method detection limit are included in the mean calculation as zero. Difenzoquat was only detected in one sample at a concentration of 1.75 &mgr;g/L.

Degradation of the herbicide paraquat by photo-fenton process: optimization by experimental design and toxicity assessment

“…5 It has been found in the range of 2-12 mg L -1 in groundwater, 6 and, for example, at average concentration of 0.78 mg L -1 in surface waters in Spain. 7 In acute toxicity studies performed by US Environmental Protection Agency using laboratory animals, PQT has been shown to be highly toxic by inhalation route, having been classified in toxicity category I (the highest of four levels). The high toxicity of this compound has also been observed in studies involving the use of bacteria, small crustaceans, algae and aquatic plants.…”

Adsorption kinetics of herbicide paraquat in aqueous solution onto a low-cost adsorbent, swine-manure-derived biochar

“…Organic pesticide residues have been reported in drinking water, agricultural water, and groundwater (Fernandez et al 1998;Ritter et al 2002). These pesticides generally penetrate into surface water in runoff from land applications (Khan 1980).…”

Efectos del herbicida Paraquat sobre el zooplancton

“…Las descargas se realizaron en tres ocasiones (24 de febrero, 5 y 13 de marzo de 1998) con un intervalo de 8 días cada una en las siguientes concentraciones 0,1, 0,2, 0,4 y 0,8 mlPQ/L. Las concentraciones utilizadas fueron seleccionadas en relación con los valores de toxicidad citados por ALBERDI et al (1996);FERNÁNDEZ et al (1998);TORTORELLI et al (1989). Se utilizaron dos réplicas para cada concentración y control.…”

“…El Paraquat, al ser soluble en agua y adsorberse a la materia orgánica, puede ejercer su acción tóxica directa o indirectamente por ingestión de microalgas contaminadas. Ha sido estudiado en monitoreo en agroecosistemas (FERNÁNDEZ et al, 1998), en cladóceros mediante bioensayos de toxicidad aguda (Tooby, 1981apud HELLAWELL, 1989ALBERDI et al, 1996), en el barbo (TORTORELLI et al, 1989), anuros (LAJMANOVICH et al, 1997) y peces (PARMA DE CROUX et al, 1999). Existen experimentos que analizan el efecto de herbicidas (Imazapyr y Arsenal N.A.)…”