Organochlorine Pesticides in Soils from the Middle and Lower Sinú River Basin (Córdoba, Colombia)

After decades of intensive application to the croplands of the lower and middle Sinú River valleys in Córdoba Department, an area of important agricultural activity, organochlorine pesticides (OCPs) were officially banned from agricultural use in Colombia in the 1990s. Until now, no studies of the OCP residue levels and their vertical distributions in the soils of this area had been conducted. In the present study, 83 representative topsoil samples (0–20-cm depth) and four soil cores were collected. The OCP concentrations were quantified via gas chromatography with electron capture detection. The resulting data indicate that the principal pesticide residues in the soil samples from both the middle and lower Sinú River basin were 4,4′-DDT (1.78 ± 4.99 μg kg−1), 4,4′-DDD (3.55 ± 8.27 μg kg−1), α-chlordane (80.0 ± 200.0 μg kg−1), and lindane (280 ± 870.0 μg kg−1), which accounted for approximately 80 % of the total residues detected in both regions. Other pesticide residues, such as β-BCH and β-endosulfan (0.11 ± 0.4 and 2.91 ± 20 μg kg−1, respectively), were also detected. The presence of these organochloride pesticides could be attributed to past agricultural applications and/or the adulteration of pesticides that are not banned. Soil profiles from almost all sampled sites indicate that organochlorine residues remain in surface layers. Because these compounds are highly toxic, persist in the environment, and are strongly enriched through the food chain, these results indicate a substantial environmental risk from organochlorine pesticides in the study area.