Distribution of organochlorine pesticides in sediment cores from the Bizerte Lagoon (Tunisia)

Abstract

ABSTRACT The present study investigates the vertical distribution of organochlorine pesticides (OCPs), in two sediment cores collected from the Bizerte Lagoon. The sediment core (SC1) is located in the mouth of the channel connecting the lagoon to the Mediterranean Sea and characterized by the industrial and urban activities of zone A and B. The sediment core (SC2) is situated in the zone D known by its intensive metallurgy and naval construction activities. The OCPs concentrations ranged from 26.98 ± 0.04 ng g−1 found at 3 cm depth and 10.23 ± 0.02 ng g−1 at 6 cm depth in SC1, and varied between 11.77 ± 0.11 ng g−1 at 9 cm depth and 1.47 ± 0.02 ng g−1 at 20 cm depth in SC2. The results showed that the SC2 had lower levels of OCPs and total organic carbon (TOC) compared to SC1. Generally, OCPs and TOC % decreased with depth along the two SCs profiles. The different categories of OCPs were in the following order: DDTs> Aldrin >HCB. The principal OCPs in deeper sediment layers were aldrin, endrin, and ∑DDTs for SC1 in addition to HCB and aldrin for SC2. The predominant OCPs in surface sediments were dieldrin, endrin and ∑DDTs for SC1, and HCB, heptachlor, aldrin and ∑DDTs for SC2. Different profiles were observed making evident that the levels of these pollutants depend strongly on anthropological discharges from industrial, urban and farming sources. The temporal trends of OCPs were influenced by their different historical usages, different properties or different degradation conditions in the environment. DDTs was mainly due to historical residue and biodegradation occurred in aerobic conditions. According to the established guidelines for sediment quality, levels of OCPs at most of the SCs layers were below class criteria. However, levels of DDE in SC1 could cause biological damage and ecotoxicological risk.