Heavy metals widely exist in water, soil, and plant in riparian zone, the intersection of terrestrial and aquatic ecosystems on earth surface. Most of them, i.e., mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr), and arsenic (As), generally existing at low concentrations, can cause damage to the environment when their accumulations exceed certain levels. With the completion of the Three Gorges Dam in 2008, the newly formed water level fluctuation zone (WLFZ) results in various ecological problems including loss of previous vegetation and soil erosion in an area of 350 km2 in the Three Gorges Reservoir (TGR).

To restore the riparian ecosystem, revegetation projects have been carried out in some areas in recent years. The changes of natural environment together with human activities could alter the heavy metal distribution and pollution status in the riparian zone soil. However, little information is available on the evaluation of heavy metal pollution in the WLFZ during the drying period after the completion of the Three Gorges Dam.

Scientist at Wuhan Botanical Garden made an investigation on heavy metals in natural recovery area and revegetation areain the WLFZ of the TGR to assess the spatial variability and evaluate the influence of revegetation on heavy metals. Their results demonstrated significantly lower concentrations for elements of As, Cd, Pb, Zn and Mn in the revegetation area, suggesting the effectiveness of revegetation project on controlling heavy metal pollution in the WLFZ. The geoaccumulation index (I_geo) and factor analysis (FA) revealed moderate pollutants i.e., Cd and the slight pollutant (i.e., Hg) in the WLFZ, and identified pollutant sources of industrial and domestic wastewater, natural rock weathering, traffic exhaust, and crustal materials.

Nevertheless, soil microbial community failed to monitor the soil heavy metal pollution. Thus, combining the geochemical technique with soil microbial community structure approach could be a reliable approach to assess heavy metal pollution in the WLFZ of Three Gorges Reservoir, China. Moreover, other indicators, like soil populations or toxicity tests or metal bioacumulation in vegetation, should be used in the further investigation to better evaluate metals bioavailability.

The study entitled “Assessing heavy metal pollution in the water level fluctuation zone of China’s Three Gorges Reservoir using geochemical and soil microbial approaches” has been published in Environmental Monitoring & Assessment.

Abstract: http://www.springerlink.com/content/w2583777p1162370/