The response of mercury (Hg) transformation in soil to sulfurcompounds and sulfur-rich biowaste application
2016
The mobility of mercury and its transformation as affected by
different sulfur-rich amendments were investigated in a model
laboratory incubation experiment. Two soils, Chernozem and
Luvisol, differing in their physicochemical characteristics,
were selected for the experiment. The soils were artificially
contaminated with Hg by adding HgCl2 solution to a final
concentration of 12 mg kg-1 of Hg in the soils. Subsequently,
organic and inorganic amendments: (1) (NH4)2SO4, (2)
L-cysteine, and (3) digestate, a biowaste from a biogas
station, were applied and the soils were incubated for 21 days
in the dark. Soil samples were collected after 1, 7, 14 and 21
days of incubation. At the individual sampling times 30 g of
each soil was collected for determinations of pH, the mobile Hg
pool, carbon derived from microbial biomass, and dehydrogenase
activity. The results confirmed the important role of digestate
application leading to (1) improved nutrient status and
microbiological activity in the contaminated soils and (2) an
increased proportion of methylmercury in the soils as well as a
decrease in mercury volatilization. These findings suggested
that digestate could be applied to Hg contaminated soil for
effective stabilization of this element in the soil. However,
long-term experiments are necessary for an evaluation of
further potential Hg transformations due to the decomposition
of digestate-bearing organic matter.
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