Organic and inorganic contaminants in marine sediments off northern Mozambique

Presents the measurements of grain size, total organic carbon, hydrocarbons and metals in surface sediments collected from 40 locations off the coast of northern Mozambique with the conclusion that no significant oil-related pollution was detected.

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The report presents the results of the measurements of grain size, total organic carbon (TOC),hydrocarbons and metals in surface sediments (greater than 100 samples) collected from 40 locations off the coast of northern Mozambique during an environmental survey in March–April 2018. The survey was carried out from the R/V Dr Fridtjof Nansen in the following areas: (i) Pemba – planned gas industry logistic base, (ii) Ibo Island (Quirimbas National Protected Area) to St. Lazarus Bank – the reference area, and(iii) Palma - gas exploration area. The contents of fine-grained fraction (les than 63 um) of the sediment varied strongly in all areas from coarse sediment to high mud contents, whereas TOC levels were generally low and correlated poorly with fine-grained fraction. Background levels of hydrocarbons and metals were found in most of the samples. Anthropogenic contamination was found at one site in Pemba harbour. No oil-related contamination was demonstrated, including the Palma area where gas exploration is concentrated. Elevated concentrations of barium and total hydrocarbon content at some locations in the Palma area are attributed to drilling activities but are not considered to be of environmental concern. Based on the measured concentrations of chemicals, background concentrations for the studied areas are proposed