[Effects of applying sewage sludge on chemical form distribution and bioavailability of heavy metals in soil].

A pot experiment was conducted to study the effects of applying sewage sludge on the chemical form distribution of heavy metals (Cd, Pb, Cu and Zn) in soil and the transfer and accumulation of the heavy metals in soil-plant (ryegrass) system. With the application of sewage sludge, the contents of bioavailable Cd and Zn in soil increased significantly but that of bioavailable Pb in soil had a significant decrease, and the content of residual form Pb in soil increased by 33.3% -74.5%, compared with CK. When the application rate of sewage sludge was 50% (M/M) of soil, the contents of exchangeable and reducible Cu in soil only occupied 0.7% and 0.2% of the total Cu respectively. The application of sewage sludge promoted the Cd, Cu and Zn absorption while inhibited the Pb absorption by ryegrass. Multiple linear regression analysis showed that the Cd, Zn and Cu contents in ryegrass were positively correlated with the reducible Cd and Zn and oxidizable Cu contents in soil, respectively, and Pb content in ryegrass was highly correlated with the soil exchangeable and oxidizable Pb contents. After planting ryegrass, the oxidizable Cd and Cu in rhizosphere soil were transformed into exchangeable Cd and residual form Cu, respectively, the exchangeable and reducible Zn transformed into oxidizable Zn, whereas the bioavailability of Pb was less affected.

[Health assessment on aquatic ecosystem in Liaohe River of Liaoning Province].

Based on the investigation of the hydrology, water quality, periphytic algae, and habitat conditions of 20 hydrologic sections in the Tieling, Shenyang, and Panjin reaches of Liaohe River from June to August 2009, the indicators and their weights for the health assessment of aquatic ecosystem in the River were screened and determined by the method of principal component analysis, and the River's health assessment indicator system and health assessment standard system were constructed. The modified gray correlative degree method was also used to evaluate the aquatic ecosystem health condition at six sections of the River. Among the sections evaluated, three of them had a fair health level, two were worse or worst, and only one reached sub-health degree, suggesting that the aquatic ecosystem in the River was seriously degraded. Special attention should be paid to the ecological recovery of the river system, and comprehensive measures should be taken to control the River' s water pollution.