[Analysis of composition characteristics of municipal solid waste in south China].

Using the MSW (municipal solid waste) sampling and analysis methods, the composition characteristics of MSW in south China were investigated. The results showed that: the average MSW bulk density was 0.22 x 10(3) kg x m(-3), the percentages of water, ash and combustible were 55.0%-66.9%, 18.6%-30.3% and 69.7%-81.4%, respectively. The organic contents were 50.1%-58.0%. The waste low caloric value (wet base) ranged 6570-9652 kJ x kg(-1), and the average of waste low caloric value(wet base) was 8272 kJ x kg(-1), which was higher than the recommended value of World Bank(7000 kJ x kg(-1)). The percentage composition of MSW was: 39.8%-53.3% kitchen waste garbage, 16.5%-33.4% rubber and plastics, 5.61%-7.95% paper, 1.14%-5.16% textile products, 2.49%-5.12% bamboo products, 1.10%-1.47% glass, 5.86%-7.57% mixed materials, 2.46%-6.73% dust, 0.1%-0.32% metal, and 0.4%-0.69% ceramic. The correlation analysis and factor analysis showed that: the high proportions of textile, rubber and plastics, paper, and combustible materials had a positive effect on the MSW incineration, while the high proportions of kitchen waste garbage, glass, MSW bulk density, ash, water content and dust had a negative effect on the MSW incineration.

[Evaluation of the heavy metals contamination and its potential ecological risk of the sediments in Beijiang River's upper and middle reaches].

In order to find out the heavy metals concentrations and their potential ecological risks of the sediments in Beijiang river's upper and middle reaches, 25 sediments specimens were sampled from both the trunk stream and tributaries for analyzing Cu, Pb, Zn, Cd, Ni, Cr, As and Hg. The Index of Geoaccumulation and the Potential Ecological Risk Index were then employed to evaluate the pollution degree of heavy metals in the sediments. The results indicate that the sediments in Beijiang River have been severely contaminated by many heavy metals. The descending order of pollution degree of various metals is: Cd >> Hg > Zn > As > Pb approximately to Cu > Ni > Cr; and similarly the potential ecological risk intensity caused by different metals is: Cd >> Hg > Pb approximately to As > Cu > Zn > Cr, and Cd is the predominant element among them. In general, because the trunk stream receives huge waste discharge, the pollution degree of heavy metals is stronger in the trunk stream than that in the tributaries due to long time accumulation. The Maba River is the worst polluted among the tributaries, and the Zhengshui River and Wongjiang River are next to it.