Naslov
Solid speciation of mercury in contaminated coastal sediments

Autori
Niessen, Sylvie ; Foucher, Delphine, Fischer, jean-Claude, Mikac, Nevenka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
6th International Conference "Mercury as a Global Pollutant" / - Minamata, 2001

Skup
6th International Conference "Mercury as a Global Pollutant"

Mjesto i datum
Minamata, Japan, 15.10.2001. - 20.10.2001

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
mercury; sediment; speciation

Sažetak
Interactions of trace metals with sulphide in anoxic environment are important in determining their chemical form and mobility in aquatic sediments. It was considered for a long time that Hg in anoxic marine sediments is immobilised as HgS and consequently not available for methylation. However, formation of HgS in saline anoxic sediment is recently questioned from kinetic reasons. In this work solid speciation of mercury was investigated in coastal sediments heavily contaminated by mercury from the chlor-alkali plant. This sediment is anoxic, organic rich and fine-grained, containing significant levels (30-70 umol/g) of acid volatile sulphides (AVS). Speciation of mercury was performed by sequential leaching with, first 1 or 6 M HCl (during 24 h), and second concentrated nitric acid (during 1 h). It was found that less then 10 % of total Hg could be extracted by 1 M HCl, whereas about 90 % of residual Hg is extracted by HNO3. However, 6 M HCl extracts almost all Hg from these sediments (75-100 %). Low levels of Hg extracted with 1 M HCl are presumably the consequence of methodological artefacts, the precipitation of Hg during extraction by reaction with HCl-soluble sulphides (FeS). Model experiments with leaching of HgS (cinnabar) have shown that under the same extraction conditions less than 0.5 or 2 % of HgS is dissolved by 1 or 6 M HCl, respectively. In the second step HNO3 extracts about 20 % or 70 % of HgS after 1M or 6 M HCl, respectively. These results demonstrate that even in these highly anoxic and sulphidic sediments most of the Hg is reactive (HCl-soluble) and only a minor percentage (1-5 % of total Hg which was found in the residue after sequential leaching) is probably in the form of HgS. It is in accordance with recent suggestion that in saline sediments Hg will not form a discrete HgS mineral before FeS forms, as Hg complexation with chloride retards its reactivity with sulphide.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA