Speciation of organometallic compounds of Hg, Sn, and Pb in the market garden soil in Ngaoundéré (Cameroon)

The objective of this work is to study the contamination of market garden soils by organomercury compounds (OMC), organotin compounds (OTC), and organolead compounds (OLC) using combustion debris (CD) as fertilizers. Therefore, two parcels of land used for gardening are rented on two sites. Soils were plowed and amended with CD. Samples of non-amended and amended soils were treated and then organometallic compounds of Hg, Sn, and Pb were analyzed by GC–ICP–MS. The results obtained revealed the presence of methyl-mercury (MeHg) in the soil at concentrations varying from non-detected in non-amended soil to 171.6 µg/kg in amended soil. Among the OLC identified, tetra-ethyl-lead (TEtPb) is the most represented in the soil with concentrations ranging from 18.45 to 44,612 µg/kg. OTC has also been identified with a predominance of mono-butyl-tin (MBT) followed by tri-methyl-tin (TMT) and di-methyl-tin (DMT). Soil treatments to CD have a significant influence on soil contamination to OMC, OTC, and OLC. This means that a significant amount of organometallic compounds found in amended soils would come from either direct or indirect CD.