Predicting occupational exposure to trace metals from welding by non-air monitoring based models

Key messages

With a view to assess occupational exposure, non-air monitoring based models, that are time and cost saving tools, showed good prediction abilities for trace metal levels near welding emission sources. The use of non-air monitoring based models would help to control the working environment of occupationally exposed populations to welding fumes, which is useful to comply with air quality standards.

Occupational exposure assessment to per and trichloroethylene in dry cleaning in Sfax city (Tunisia)

Key messages

Our study is the first health risk assessment study of the exposure to chlorinated solvents in dry cleaning in Sfax city. It revealed high levels of trichloroethylene that is a carcinogen to humans. The high exposure levels to per and tri-chloroethylene, in dry cleaning in Sfax city, may induce adverse health effects to workers and even the general population due to residential exposure.

Discoloration and detoxicification of a Congo red dye solution by means of ozone treatment for a possible water reuse

The objective of this study was to investigate the degradation and mineralization of an azo-dye, the Congo red, in aqueous solutions using ozone. Phytotoxicity and the inhibitory effects on the microbial activity of the raw and the ozonated solutions were also carried out with the aim of water reuse and environment protection. Decolorization of the aqueous solutions, disappearance of the parent compound, chemical oxygen demand (COD) and total organic carbon (TOC) removal were the main parameters monitored in this study. To control the mineralization of the Congo red, pH of the ozonated solution and heteroatoms released from the mother molecule such NH(4)(+), NO(3)(-) and SO(4)(2-) were determined. It was concluded that ozone by itself is strong enough to decolorize these aqueous solutions in the early stage of the oxidation process. Nonetheless, efficient mineralization had not been achieved. Significant drops in COD (54%) were registered. The extent of TOC removal was about 32%. Sulfur heteroatom was totally oxidized to SO(4)(2-) ions while the central -NN- azo ring was partially converted to NH(4)(+) and NO(3)(-). Results of the kinetic studies showed that ozonation of the selected molecule was a pseudo-first-order reaction with respect to dye concentration. The obtained results also demonstrate that ozone process reduced the phytotoxicity of the raw solution and enhanced the biodegradability of the treated azo-dyes-wastewater. Hence, this show that ozone remains one of the effective technologies for the discoloration and the detoxification of organic dyes in wastewater.

Hydrocarbon contamination of coastal sediments from the Sfax area (Tunisia), Mediterranean Sea

The coastal area off the city of Sfax (730,000 inhabitants), well-known for fisheries and industrial activities, receives high inputs of organic matter mostly anthropogenic. Eighteen stations were selected in the vicinity of the direct discharge of industrial sewage effluents in the sea in order to study the spatial distribution of the organic contamination. Surface sediments sampled in the shallow shelf were analysed for hydrocarbons by Fourier transform infrared spectroscopy, gas chromatography and gas chromatography/mass spectrometry. Total hydrocarbon distributions revealed high contamination as compared to other coastal Mediterranean sites, with an average concentration of 1865 ppm/dry weight sediment. Gas chromatographic distribution patterns, values of unresolved mixture/n-alkane ratio and distributions of steranes and hopanes confirmed a petroleum contamination of the Arabian light crude oil type. Biogenic compounds were also identified with a series of short-chain carbon-numbered n-alkenes in the carbon range 16-24.