An integrated vegetated ditch system reduces chlorpyrifos loading in agricultural runoff

Abstract

Agricultural runoff containing toxic concentrations of the organophosphate pesticide chlorpyrifos has led to impaired water body listings and total maximum daily load restrictions in California's central coast watersheds. Chlorpyrifos use is now tightly regulated by the Central Coast Regional Water Quality Control Board. This study evaluated treatments designed to reduce chlorpyrifos in agricultural runoff. Initial trials evaluated the efficacy of 3 different drainage ditch installations individually: compost filters, granulated activated carbon (GAC) filters, and native grasses in a vegetated ditch. Treatments were compared to bare ditch controls, and experiments were conducted with simulated runoff spiked with chlorpyrifos at a 1.9 L/s flow rate. Chlorpyrifos concentrations and toxicity to Ceriodaphnia dubia were measured at the input and output of the system. Input concentrations of chlorpyrifos ranged from 858 ng/L to 2840 ng/L. Carbon filters and vegetation provided the greatest load reduction of chlorpyrifos (99% and 90%, respectively). Toxicity was completely removed in only one of the carbon filter trials. A second set of trials evaluated an integrated approach combining all 3 treatments. Three trials were conducted each at 3.2 L/s and 6.3 L/s flow rates at input concentrations ranging from 282 ng/L to 973 ng/L. Chlorpyrifos loadings were reduced by an average of 98% at the low flow rate and 94% at the high flow rate. Final chlorpyrifos concentrations ranged from nondetect (<50 ng/L) to 82 ng/L. Toxicity to C. dubia was eliminated in 3 of 6 integrated trials. Modeling of the ditch and its components informed design alterations that are intended to eventually remove up to 100% of pesticides and sediment. Future work includes investigating the adsorption capacity of GAC, costs associated with GAC disposal, and real-world field trials to further reduce model uncertainties and confirm design optimization. Trials with more water-soluble pesticides such as neonicotinoids are also recommended. Integr Environ Assess Manag 2017;13:423-430. © 2016 SETAC.

Expanding Wetland Mitigation: Can Rice Fields Remediate Pesticides in Agricultural Runoff?

“…Phytoremediation, the use of living vegetation to remove or help foster degradation of contaminants from water or sediment/soil sources (UNEP, 2002), is a successful technology being integrated into various management practices. Selection of vegetation type is a key determinant in the potential success of phytoremediation efforts (Moore et al, 2001, 2007, 2008, 2017; Phillips et al, 2017). Particularly in agricultural settings, vegetation selection is critical so as not to introduce any potential noxious weeds or other plants of concern into the ecosystem.…”

An Integrated Vegetated Treatment System for Mitigating Imidacloprid and Permethrin in Agricultural Irrigation Runoff

“…Vegetated treatment systems are usually drainage ditches that have been planted with grass or similar vegetation that can slow the flow and infiltrate runoff from agricultural fields. Research has demonstrated that VTSs, used individually or as part of a suite of management practices, reduce pesticide loads in tailwater runoff [ 3 , 4 , 5 , 6 , 7 ]. Treating irrigation water with polyacrylamide (PAM), a long-chain polymer used for erosion control, can also reduce the suspended sediments in runoff by more than 90% [ 8 , 9 ].…”

“…Treating irrigation water with polyacrylamide (PAM), a long-chain polymer used for erosion control, can also reduce the suspended sediments in runoff by more than 90% [ 8 , 9 ]. The addition of compost and granulated activated carbon (GAC) to a grass-lined ditch has been shown to reduce the load of chlorpyrifos, an intermediately soluble pesticide, by up to 98% [ 7 ]. Integrated vegetated treatment systems have also been shown to reduce pesticide-associated toxicity to invertebrates in runoff [ 2 , 7 ].…”

“…The addition of compost and granulated activated carbon (GAC) to a grass-lined ditch has been shown to reduce the load of chlorpyrifos, an intermediately soluble pesticide, by up to 98% [ 7 ]. Integrated vegetated treatment systems have also been shown to reduce pesticide-associated toxicity to invertebrates in runoff [ 2 , 7 ]. While these systems are effective at reducing organophosphate and pyrethroid pesticides, they have not been evaluated for treating more soluble insecticides, such as the neonicotinoid imidacloprid.…”

“…Biochar has been used as remediation for contaminated soils [ 17 , 18 ], and some recent research has been conducted applying biochar to treat pesticides in simulated agricultural runoff [ 19 , 20 ]. Recent research demonstrated the removal of chlorpyrifos by activated carbon in simulated agricultural runoff [ 7 ], and a laboratory study showed similar success with imidacloprid and chlorpyrifos removal [ 21 ].…”