Methyl parathion toxicity in vegetated and nonvegetated wetland mesocosms

Abstract

Methyl parathion (MeP) was introduced into constructed wetlands for the purpose of assessing the influence of emergent vegetation on transport and toxicity of the pesticide. Two vegetated (90% cover, mainly Juncus effusus) and two nonvegetated wetland cells (each with a water body of 50 x 5.5 x 0.2 m) were each dosed with 6.5 m3 of water containing active ingredient of MeP at 6.6 mg/L associated with suspended soil at 400 mg/L to simulate a storm runoff event. Acute toxicity was assessed by sampling benthic macroinvertebrates at 5, 10, 20, and 40 m from the inlet before and 96 h after contamination and by in situ exposure of Chironomus tentans (Diptera) up to 24 h after contamination. Methyl parathion was detected throughout the nonvegetated wetland cells (70 microg/L at 20 m, 8 microg/L at 40 m), whereas the pesticide was not transported through the vegetated wetland cells (20 microg/L at 20 m, < 0.1 microg/L at 40 m). A three-way analysis of variance using contamination (repeated measure variable), location, and vegetation indicated significant negative effects of contamination on various insect taxa, such as mayfly nymphs and caddisfly larvae. Seven out of the total of 15 species revealed a significant contamination x vegetation effect, with individuals in the vegetated wetlands being less affected. Four species showed a significant contamination x location effect, confirming a higher toxicity in the inlet area of the wetlands. A significant three-way interaction of contamination x vegetation x location was detected in Chironomus sp., which was most strongly affected at the inlet area of the nonvegetated wetland cells. The in situ bioassay employing C. tentans confirmed the positive effect of wetland vegetation on MeP toxicity. These results demonstrate the importance of vegetation for pesticide mitigation in constructed wetlands.

Identifying the cause and source of sediment toxicity in an agriculture-influenced creek

“…Control of soil loss from farmland is the key to preventing the sediment degradation observed, and that has long persisted in Del Puerto Creek given the frequent reports of sediment toxicity in the creek over at least the past several years. Recovery and reuse of irrigation runoff, with no discharge to surface waters would be a definitive solution, but substantial improvement may also be possible with relatively simple changes in management practices, such as the use of vegetated drainage ditches [27,28]. Another possible approach is addition of polyacrylamide to irrigation water to minimize erosion and promote flocculation of suspended material [29], a technique that has been shown to be very effective in mitigating soil transport in testing in the vicinity of Del Puerto Creek [30].…”

Effect of Parathion-Methyl on Amazonian Fish and Freshwater Invertebrates: A Comparison of Sensitivity with Temperate Data

“…Because parathion-methyl shows a fast dissipation under field conditions (Schulz et al 2003), the exposure regime in static tests was considered more appropriate than a constant exposure. The tests were performed in 2.5-L glass vessels with five treatment levels and an untreated control.…”

Pesticide Risk Mitigation by Vegetated Treatment Systems: A Meta-Analysis

“…For example, Braskerud and Haarstad (2003) found an improved retention rate with increasing metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4triazin-5-one) and metalaxyl (methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate) concentrations. Th e state of current research on the importance of diff erent design factors of VTSs for pesticide retention indicates that vegetated mitigation systems are more effi cient than nonvegetated systems (Moore et al, 2009b;Schulz et al, 2003;Gill et al, 2008). Furthermore, evidence suggests that the retention rate is positively related to hydraulic retention time and thus to the ratio of VTS volume and water infl ow (Matamoros et al, 2008) and is inversely related to the hydraulic loading rate (defi ned as water infl ow divided by system surface area [Blankenberg et al, 2006;Blankenberg et al, 2007]).…”

“…Plant coverage was the most important VTS characteristic infl uencing the retention performance (Table 3). Th e importance of this variable with regard to pesticide retention has been documented extensively within the scientifi c literature (e.g., Moore et al, 2002;Schulz et al, 2003;Gill et al, 2008;Cooper et al, 2004). Th eir highly eff ective retention eff ects can be explained by physical adsorption of pesticides to the organic plant material.…”