Pedosphere 23(4): 511--522, 2013
ISSN 1002-0160/CN 32-1315/P
©2013 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Spatial and seasonal variations of heavy metals in wetland soils of the tidal flats in the Yangtze Estuary, China: Environmental implications |
HU Xue-Feng1 , DU Yan1，FENG Jian-Wei1, FANG Sheng-Qiong2, GAO Xiao-Jiang3 and XU Shi-Yuan4 |
1Department of Environmental Science and Engineering, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China)
2Department of Environmental Science and Engineering, Fuzhou University, Fuzhou 350002 (China)
3Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China)
4Department of Geography, East China Normal University, Shanghai 200062 (China) |
| ABSTRACT |
| The environment of estuarine wetlands has been attracting worldwide attention. To study the spatial distribution of pollutants in the tidal flats of the Yangtze Estuary, Southeast China, the Eastern Tidal Flat of Chongming Island (EC) and the Jiuduansha Shoal (JS) of the estuary were selected as the study sites. At each of the two sites, a cross-transect from land to sea was established and topsoil and soil core samples in the cross-transect were collected spatially and seasonally to determine their contents of heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, Mn, and Fe) and grain-size characteristics. The results showed that the heavy metal loads were commonly higher in the soils of nearshore high tidal flats and had a tendency of decreasing from land to sea at both of the study sites. The contents of heavy metals in the soils of the high and medial tidal flats were mostly higher in April and November but lower in July. Corresponding spatial and seasonal variations in grain size of the intertidal soils were also observed at the two study sites. The soils in the nearshore high tidal flats were finer and gradually got coarser seawards; they were relatively finer in April and November but coarser in July. Furthermore, the contents of heavy metals in the intertidal soils of both the sites EC and JS were significantly positively correlated with the clay (< 2 μm) and 2--20 μm fractions, but negatively with the sand (> 63 μm) and 20--63 μm fractions, which suggested that the heavy metals in the intertidal soils were primarily combined with the fine particulate fraction (< 20 μm), especially clay, and hence the spatial and seasonal variations in heavy metals were actually caused by the change of the grain-size characteristics of the intertidal soils due to the different sedimentary environments in the estuary. The results of this study may also contribute to a better understanding of the soil formation and classification in the tidal flats of the Yangtze Estuary. |
| Key Words: clay fraction, grain-size characteristics, intertidal soils, pollutants, sedimentary environments |
| Citation: Hu, X. F., Du, Y., Feng, J. W., Fang, S. Q., Gao, X. J. and Xu, S. Y. 2013. Spatial and seasonal variations of heavy metals in wetland soils of the tidal flats in the Yangtze Estuary, China: Environmental implications. Pedosphere. 23(4): 511-522. |
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