The diagenetic geochemistry and contamination assessment of iron, cadmium, and lead in the sediments from the Shuangtaizi estuary, China

• Published in: Environmental earth sciences Vol. 76; no. 4; pp. 1 - 11
• Main Authors: Liu, Baolin, Nie, Yongsheng, Gao, Xiuhua, Hu, Ke, Yang, Juan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2017; Springer Nature B.V
• Subjects: Anthropogenic factors; Biogeosciences; Cadmium; Chromium; Contamination; Diagenesis; Distribution; Earth and Environmental Science; Earth Sciences; Environmental Science and Engineering; Estuaries; Estuarine dynamics; Fluxes; Geochemistry; Geology; Heavy metals; Human influences; Hydrology/Water Resources; Iron; Iron sulfides; Lead; Manganese; Mathematical analysis; Organic carbon; Organic matter; Original Article; Oxides; Pore water; Pyrite; Sediment; Sediments; Sulfides; Sulfur; Sulphides; Sulphur; Terrestrial Pollution; Tidal flats; Total organic carbon; Water analysis; Water sampling; Shuangtaizi estuary; Sediment; Metal; Contamination
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-017-6481-4

Sediment and pore water samples have been collected from the coastal tidal flat in the Shuangtaizi estuary, China, in order to investigate the geochemical behavior of iron, cadmium, and lead during diagenesis and to assess the degree of contamination. The calculated enrichment factors and geoaccumulation indices for separate elements show that anthropogenic activities have had no significant influence on the distribution of Fe and Pb in the study area, whereas the distribution of Cd has been closely influenced in this way. The high percentage of exchangeable Cd (average of 56.34%) suggests that Cd represents a potential hazard to benthic organisms in the estuary. The calculated diffusive fluxes of metals show that the most mobilized metal is Fe (9.22 mg m −2  a −1 ), followed by Cd (0.54 mg m −2  a −1 ) and Pb (0.42 mg m −2  a −1 ). Low Fe 2+ contents in surface pore water, alongside high chromium-reducible sulfur contents, and low acid-volatile sulfur, and elemental sulfur contents at 0–25 cm depth in sediments show that Fe 2+ is formed by the reduction of Fe oxides and is transformed first to a solid phase of iron monosulfides (FeS) and eventually to pyrite (FeS 2 ). The release of adsorbed Pb due to reductive dissolution of Fe/Mn oxides during early diagenesis could be a source of Pb 2+ in pore water. From the relatively low total organic carbon contents measured in sediments (0.46–1.28%, with an average of 0.94%) and the vertical variation of Cd 2+ in pore water, sulfide or Fe/Mn oxides (instead of organic matter) are presumed to exert a significant influence on carrying or releasing Cd by the sediments.