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Pesticide Transport Pathways from a Sloped Litchi Orchard to an Adjacent Tropical Stream as Identified by Hydrograph Separation
Author(s) -
Duffner Andreas,
Ingwersen Joachim,
Hugenschmidt Cindy,
Streck Thilo
Publication year - 2012
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2011.0316
Subject(s) - environmental science , separation (statistics) , orchard , hydrograph , pesticide , hydrology (agriculture) , environmental chemistry , geology , chemistry , ecology , surface runoff , biology , mathematics , geotechnical engineering , statistics
This study was performed to identify the transport pathways of pesticides from a sloped litchi ( Litchi chinensis Sonn.) orchard to a nearby stream based on a three‐component hydrograph separation (baseflow, interflow, surface runoff). Dissolved silica and electrical conductivity were chosen as representative tracers. During the study period (30 d), 0.4 and 0.01% of the applied mass of atrazine and chlorpyrifos, respectively, were detected in the stream after 151 mm of rainfall. Baseflow (80–96%) was the dominant hydrological flow component, followed by interflow (3–18%) and surface runoff (1–7%). Despite its small contribution to total discharge, surface runoff was the dominant atrazine transport pathway during the first days after application because pesticide concentrations in the surface runoff flow component declined quickly within several days. Preferential transport with interflow became the dominant pathway of atrazine. Because chlorpyrifos was detected in the stream water only twice, it was not included in the hydrograph separation. A feature of the surface runoff pathway was the coincidence of pesticide and discharge peaks. In contrast, peak concentrations of pesticides transported by interflow occurred during the hydrograph recession phases. Stormflow generation and pesticide transport depended on antecedent rainfall. The combination of high‐resolution pesticide concentration measurements with a three‐component hydrograph separation has been shown to be a suitable method to identify pesticide transport pathways under tropical conditions.