Can PBDE natural formation and degradation processes interfere with the identification of anthropogenic trends and sources? Evidences from sediments of the Nador Lagoon (Morocco).

This paper presents the first results related to PBDE concentrations in sediments of the Nador Lagoon (N-E Morocco), an area endangered by different pollutant sources. Analyses were performed by HRGC-LRMS and confirmed by HRGC-HRMS on selected samples. Total surficial concentrations were 0.059-8.2ngg(-1). The maxima were found close to Nador City. Along the sedimentary records, the highest total concentrations (11 and 2.2ngg(-1)) were found at depths corresponding to times (1930s-1950s) when these chemicals were not yet produced. Dehydroxylation or demethoxylation of naturally occurring structural analogues of PBDEs under reducing conditions was suggested. BDE-47 dominated the congener compositions, while BDE-209, when present, could be detected only by HRGC-HRMS, proving that analytical degradation modified the original assemblage. Microbial anaerobic degradation could have changed congener compositions in sediments deposited from the 1970s to the 2000s. Current values are not harmful, but increasing trends call for constant monitoring.

Recognizing different impacts of human and natural sources on the spatial distribution and temporal trends of PAHs and PCBs (including PCB-11) in sediments of the Nador Lagoon (Morocco).

The Nador Lagoon holds a major interest in present-day Moroccan socioeconomic development. This environment is exposed to a number of potential polluting sources, such as mine tailings, urban and industrial dumping, and untreated wastewater inputs from surrounding cities. The aim of this study was to assess concentrations and trends of persistent contaminants such as PCBs and PAHs and to identify their origin. The non-Aroclor PCB-11 was determined for the first time in the lagoon sediments. Chronology and source assessment helped identifying the timing and nature of inputs and post-depositional processes controlling the two classes of contaminants: PAHs present a typical mixed petrogenic signature, with the exception of sediments deposited in the period 1930-1960 near the city of Nador, when pyrogenic inputs prevailed; PCBs show signs of microbial anaerobic degradation from 1950 to 1990, probably linked to changing hydrodynamic conditions in the South-Western part of the lagoon where agricultural inputs are dominant. The presence of PCB-11 is linked to specific productions and might be affected by degradation processes. Presently, different land uses (e.g., urban and agricultural areas) appear to be the key factors in controlling the level and composition of PAHs and PCBs in lagoon sediments. Total PAH and PCB levels are low (from 21.6 to 108 ng g(-1) and from 2.50 to 20.7 ng g(-1), respectively) but recent increasing values and the potential threat to humans and biota require continuous and constant monitoring.