Preliminary results from the Tunisian monitoring program on POPs in air under the Stockholm Convention

Abstract

Persistent organic pollutants (POPs) have been measured using passive air samplers (PASs) over two years (2017–2018) in the city of Tunis within the framework of the UNEP/GEF GMP2 projects to support Stockholm Convention implementation. Several POPs, although banned for a long time from Tunisia, were registered in relatively high amounts in the atmospheric compartment. The most unexpected compound is hexachlorobenzene (HCB), with concentrations ranging from 5.2 ng/PUF to 16 ng/PUF. Furthermore, the current results seem to confirm the presence of dichlorodiphenyltrichloroethane (DDT) and its transformation products and hexachlorocyclohexanes (HCHs) at relatively high concentrations (4.6 ng/PUF to 9.4 ng/PUF and 2.7 ng/PUF to 5.1 ng/PUF, respectively), followed by hexabromocyclododecane (HCBD), which varies from 1.5 ng/PUF to 7.7 ng/PUF. Nondioxin-like PCB (ndl-PCB) concentrations in Tunis were very high (62.0 ng/PUF to 419.3 ng/PUF), higher than those in other African countries participating in this project. Uncontrolled combustion seems to be one of the most important sources of the emanation of dioxin compounds dl-PCBs and Polychlorinated dibenzodioxins PCDD/polychlorinated dibenzofurans PCDF. Toxic equivalents (TEQs) ranged from 4.1 pg WHO-TEQ/PUF to 6.4 pg WHO-TEQ/PUF. The perfluorinated compounds (PFAS) and congeners of polybrominated diphenyl ethers (PBDEs) show relatively low amounts that remain below the African continent average. The PFAS pattern suggests a local source rather than long-range transport. These results constitute the first exhaustive work capable of providing an overview of the levels of POPs in the air in Tunis. As a result, it will be possible to set up an adequate monitoring program with specific investigations and experimental studies.