Environ Monit Assess (2012) 184:1359–1369 DOI 10.1007/s10661-011-2046-2 Pollution by organochlorine pesticides in Navachiste-Macapule, Sinaloa, Mexico Adriana M. Montes · Fernando A. González-Farias · Alfonso V. Botello Received: 6 July 2010 / Accepted: 18 March 2011 / Published online: 12 April 2011 © Springer Science+Business Media B.V. 2011 Abstract The lagoon system of Navachiste- Macapule is located in northern Mexico, in the state of Sinaloa, with an area of 24,000 ha. The main economic activity in the area is agriculture, and the lagoon lies next to the irrigation district ID-063 which covers 116,615 ha. The purpose of this study is to evaluate the levels of pollution generated by organochlorine pesticides (OC) in the surface sediments of the lagoon and in the agricultural drains of the ID-063 that are supposedly transported into the system as a result of agricultural activities and runoff from adjacent land. For this, between 2006 and 2007, 45 surface sediment samples were collected (warm dry, rainy and cold dry) from 15 sampling sites, during the three climatic seasons. Of these, eight were located inside the lagoon in marine conditions (salinity >31 PSU) and seven in the agricultural drains of the ID-063 in freshwater conditions (salinity <5 PSU). The average concentration of the OC in the sediments was 44.75 ng g −1 , among which the group of the alicyclic compounds presented the greatest concentrations. The aver- A. M. Montes (B ) · F. A. González-Farias · A. V. Botello Marine Pollution Laboratory, Institute of Marine Sciences and Limnology, National Autonomous University of Mexico, P.O. Box 70-305, Mexico City 04510, Mexico e-mail: amayanina@yahoo.com.mx age value of the total organic carbon (TOC) in the sediments of the system was 0.90%. The sediments collected inside the lagoon had an average OC concentration of 18.97 ng g −1 , and the predominant type of sediment was fine to very fine sand. The average OC concentration in the sediments collected in the agricultural drains was 75.69 ng g −1 , where fine sediments (silt) were predominant. The presence of methoxychlor, endrin and heptachlor suggested that these compounds were continuously used in the system, even though their use is forbidden in Mexico. Keywords Organochlorine pesticides · Coastal lagoon · Total organic carbon · Sediment · Mexico Introduction Tropical coastal lagoons are ecologically relevant because they provide feeding grounds, as well as reproductive and protection areas for many species, some of which are endangered. They are also important from the economic point of view, mainly for fisheries and aquaculture (Flores- Verdugo 1989). However, increases in human set- tlements and agricultural wastes such as pesticides and the direct discharge of sewage into the la- goons have generated severe pollution problems that jeopardise the ecology and biodiversity of these areas (Botello et al. 2000).