Assessment of the Environmental Risk of Pesticides Leaching at the Watershed Scale under Arid Climatic Conditions and Low Recharge Rates

Abstract

The assessment of the vulnerability of soil and groundwater resources to pesticide contamination is important to reduce the risk of environmental pollution. The applicability of the expanded attenuation factor (EAF) to assess leaching potential of 30 pesticides was investigated under four recharge rates (0.0003–0.002 m d−1) in the arid environment of the Jazan watershed. EAF results revealed that Picloram, Carbofuran, Monocrotophos, and 2,4-D pesticides showed high leaching potential, mainly because of their low K O C , and relatively longer t 1 / 2 . In addition, medium leaching potential was observed with six more pesticides (Atrazine, Aldicarb, Simazine, Methomyl, Oxamyl, and Lindane). Regardless of the recharge rate, all other pesticides showed a very low leaching potential in the Jazan watershed. Sensitivity analysis revealed that the output of the EAF index is most sensitive to the fraction of organic carbon ( f o c ) , water content at field capacity ( θ F C ) , recharge rate ( q ) , and partition coefficient ( K O C ) , and least sensitive to soil bulk density ( ρ b ) and air-filled porosity ( n a ). The areal extent of areas with larger leaching potential in the Jazan watershed was consistent with soils having f o c < 0.3, θ F C > 10 m3 m−3, and ρ b < 1450 kg m−3, and were mostly associated with the loamy sand soils, followed by the sand and silt loam soils. EAF index model performed well in assessing relative rankings of leaching potential and delineating areas that are more susceptible to pesticide leaching. At the lowest recharge rate, general risk maps showed that the risk of leaching potential was very low for all pesticides in the entire area of the Jazan watershed. On the other hand, under the worst case scenario (0.002 m d−1), only Picloram and Carbofuran showed very high leaching potential in areas that represented 10.8 and 8.2% from the total area of the Jazan watershed, respectively. The information gained from this research can help farmers and decision-makers to implement regulations and best management practices to reduce the risk of environmental pollution, and protect soil and groundwater resources in Jazan watershed.

Water vulnerability to pesticide contamination in a Brazilian semiarid watershed

“…It is also noteworthy that the solubility of a compound varies with temperature and pH. Among the most used active ingredients in the SRB, cartap, paraquat dichloride, diquat, and methamidophos are the ones with the highest solubility (Supporting Information: Table ), while solubility is the one property that indicates the likelihood of a pesticide to be carried away by rainwater and/or irrigation until it reaches a water body (Akay Demir et al, 2019; Cohen et al, 1995; Ibrahim & Al turki, 2020).…”

“…The following active ingredients have the highest K ow : α-cypermethrin, cypermethrin, λ-cyhalothrin, pyriproxyfen, and profenofos + lufenuron (Supporting Information: Table 1A). Finally, a substance's half-life (in soil or water) refers to the time required for the concentration of this substance to be reduced by half, regardless of the initial concentration (Goss, 1992;Gustafson, 1989;Ibrahim & Al turki, 2020;Papa et al, 2004;Spadotto, 2002). Chlorantraniliprole, diquat, and copper hydroxide showed higher T 1/2 in soil (Supporting Information: Table 1A).…”

Glyphosate and AMPA have low mobility through different soil profiles of the prosecco wine production area: A monitoring study in north-eastern Italy

“…During the experiment, irrigation was not performed. AF ranges between 0 and 1, where AF between 0 and 10 -2 classifies areas at low risk of groundwater leaching (e.g., strongly adsorbed chemicals), AF between 10 -2 and 10 -1 classifies areas at moderate risk, and AF between 10 -1 and 1 classifies areas at high risk (e.g., non-adsorbed chemicals) (de Paz and Rubio, 2006;Ibrahim and Ali, 2020).…”