Atrazine fate and transport within the coastal zone in southeastern Puerto Rico Thomas L. Potter a,⇑ , David D. Bosch a , Angel Dieppa b , David R. Whitall c , Timothy C. Strickland a a USDA-ARS, Southeast Watershed Laboratory, Tifton, GA 31793, United States b Jobos Bay National Estuarine Research Reserve, Aguirre, PR 00704, United States c NOAA National Centers for Coastal Ocean Science, Silver Spring, MD 20910, United States article info Keywords: Herbicide Soil Dissipation Runoff Groundwater Tropical Storm abstract Agrichemical transport to coastal waters may have adverse ecological impact. This work examined atrazine fate and transport in a field adjacent to Puerto Rico’s Jobos Bay National Estuarine Research Reserve. The herbicide’s use was linked to residue detection in shallow groundwater and movement toward the estuary; however, data indicated that transport via this pathway was small. In contrast, surface runoff as tropical storm systems moved through the area appeared to have high potential for atrazine transport. In this case, transport to the estuary was limited by runoff event timing rela- tive to atrazine application and very rapid atrazine dissipation (DT 50 = 1–3 days) in field soil. Soil incu- bation studies showed that accelerated degradation conditions had developed in the field due to repeated atrazine treatment. To improve weed management, atrazine replacement with other herbicide(s) is recommended. Use of products that have greater soil persistence may increase runoff risk. Published by Elsevier Ltd. 1. Introduction Pollution from land-based sources is a serious threat to coast- al water quality and ecosystem health worldwide (Halpern et al., 2008). Within the Caribbean basin, agriculture is often identified as a major contaminant source in coastal waters; however, few studies have established direct links between crop production and coastal water quality impairment (Rawlins et al., 1998; Taylor et al., 2003; UNEP-CEP, 2012). In order to address envi- ronmental concerns and design effective management practices that minimize impacts, investigations are needed that delineate contaminant types, sources, and transport pathways (Wilkinson and Brodie, 2011; Brodie et al., 2012). Within coastal zones, pollutant transport pathways include surface runoff and leaching of soluble contaminants to shallow groundwater followed by seepage into Bays and wetlands. Wet and dry atmospheric deposition may also contribute pesticides and nutrients to these environments (Valiela and Bowen, 2002; Alegria and Shaw, 1999). Our work focused on atrazine (6-chloro-N-ethyl-N 0 -(1-methyl- ethyl)-1, 3, 5-triazine-2,4-diamine) an herbicide commonly used in corn (Zea mays), sorghum (Sorghum bicolor), and sugarcane (Saccharum officinarum) production. Due to concerns about the frequent detection of atrazine and selected degradates in surface and groundwater, the European Union (EU) withdrew permission for atrazine use in EU states in 2004; however, intensive atrazine use continues in North and South America and Asia (Pathak and Dikshit, 2012). Widespread atrazine use has also contributed to intense scientific interest in the herbicide’s environmental fate, transport, and residue analysis, and potential for adverse impact in coastal ecosystems. Recent notable work includes detection of residues in Australia’s Great Barrier Reef Ecosystem at levels that have potential for negative ecological impact (Shaw et al., 2010; Smith et al., 2012; Lewis et al., 2012). These studies and related work have indicated that Caribbean and other tropical coastal ecosystems may be adversely impacted by atrazine use in coastal zones (Bell and Duke, 2005; Jones, 2005; Gao et al., 2011; Magnusson et al., 2010; Pinckney et al., 2002; Shaw et al., 2010). We addressed this concern during a 2.5-year investigation of atrazine fate and transport during its use on a 100-ha irrigated farm field adjacent to Jobos Bay National Estuarine Research Re- serve (JBNERR) on Puerto Rico’s southeast coast. The study was part of a USDA Conservation Effects Assessment Project (CEAP) Special Emphasis Watershed project (Zitello et al., 2008). Base- line biological and sediment quality assessments within Jobos Bay and Bay water quality monitoring conducted for CEAP were described in a recent report (Whitall et al., 2011). During the study potential pesticide wet deposition was assessed and will be reported elsewhere. Findings showed that the potential for atrazine transport to the Bay via this pathway was small (Potter unpublished results). 0025-326X/$ - see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.marpolbul.2012.12.004 ⇑ Corresponding author. Tel.: +1 229 386 7073; fax: +1 229 3867294. E-mail address: Tom.Potter@ars.usda.gov (T.L. Potter). Marine Pollution Bulletin xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article in press as: Potter, T.L., et al. Atrazine fate and transport within the coastal zone in southeastern Puerto Rico. Mar. Pollut. Bull. (2013), http://dx.doi.org/10.1016/j.marpolbul.2012.12.004