Pesticide trends in a tailwater recovery system in the Mississippi Delta

Abstract

AbstractTailwater recovery (TWR) systems are an important best management practice (BMP) used to address both water quality and quantity issues in the Mississippi Delta region. Tailwater recovery systems are surface water capture‐and‐irrigation reuse systems using a combination of ditches to capture surface water, an on‐farm storage (OFS) reservoir to store captured surface water, and pumps to move surface water from ditches to the reservoir and from the reservoir to irrigate nearby fields. It is anticipated that TWR systems improve water quality by allowing agricultural contaminants to settle out in ditches and reservoirs rather than being transported during irrigation to nearby fields and downstream aquatic systems. To determine if TWR systems are an effective way to reduce downstream pesticide transport, water samples from a ditch‐and‐reservoir TWR system in Sunflower County, MS, were routinely collected and analyzed for 5 yr. Objectives of this study were to assess seasonal pesticide and pesticide metabolite concentrations throughout the different components of the TWR system and identify any trends that may exist. Atrazine‐desethyl, atrazine‐desisopropyl, atrazine, clomazone, propanil, fipronil desulfinyl, metolachlor, fipronil, p,p'‐DDT, bifenthrin, beta‐cyfluthrin, and zeta‐cypermethrin were found in every season in both ditch and reservoir samples. Several pesticides that have not been used in the United States for decades were detected including DDT and its metabolites as well as dieldrin, heptachlor, lindane, and methyl parathion, demonstrating their environmental persistence. The reservoir featured more types and higher concentrations of pesticides, indicating a possible risk of cross‐crop injury from the recycling of the water from the reservoir for irrigation.