Equitable utilisation and effective protection of sharing transboundary water resources: international rivers of western China

Western China includes 12 provincial divisions (the 7 provinces of Sichuan, Guizhou, Yunnan, Shaanxi, Gansu, Qinghai and; 5 autonomous regions of Tibet, Ningxia, Xinjiang, Inner Mongolia and Guangxi; and one city of Chongqing), which comprise 71.4% of the national land area, 28.5% of the national population and produce 17.5% of the national GDP in China. There are 17 countries that have riparian relationships with western China, most of which are water-short countries. All are listed by UN ESCAP as countries with potential water crisis. The co-operative development and coordinated management of international rivers in western China is an important step toward the implementation of the national Great Western Development program. Taking into account of the national strategy and object hierarchy, as well as the development demand of the western region, it is necessary to pursue the multi-disciplinary study of the equitable allocation, utilisation, and eco-environment protection of transboundary water resources in the region. Such efforts will undoubtedly provide scientific evidence and support for the decision-making of the environmental protection and ecological construction and management in the western regions, the enforcement of the sub-regional economic co-operation, mitigation of trans-boundary conflicts, and enhancing bio-diversity conservation.

In-situ stabilisation followed by ex-situ composting for treatment and disposal of heavy metals polluted sediments

An innovative in-situ stabilisation treatment followed by ex-situ sediment composting was tested for its ability to treat and dispose of heavy-metal-polluted sediments in a river near the Chinese Pearl Delta. First, polluted sediments were treated in-situ to stabilise the heavy metals. Then the treated sediments were dredged, dewatered and sent for high temperature aerobic composting （HTAC） treatment. Finally, the compost products were used as a fertiliser for fiver bank plants. The stabilisation efficiency of heavy metals during the process was investigated and the results are as follows： （1） using in-situ stabilisation, the extraction concentrations of Cu, Zn and Pb were reduced by 65.0%, 82.2% and 90.0%, respectively, which are much lower than the national standard given in the Identification Standard for Hazardous Waste （GB5085.3-1996）; （2） chemical fraction analysis showed that heavy metals were further stabilized during the HTAC treatment; （3） the concentrations of Cu, Zn and Pb in rainwater leachate through the river bank met the level of class V in the Environmental Quality Standards for Surface Water in China （GB3838-2002）. Therefore, using this new process, the toxicities of heavy metals in sediments were reduced markedly.