[Objective] To study the characteristics and effects of inorganic nitrogen in east water-source and inflow rivers of Chaohu Lake. [Method] The speciation and distribution characteristics of dissolvable inorganic nitrogen （DIN） in east water-source and inflow rivers of Chaohu Lake were investigated, and their effects on water qual- ity were examined. [Result] The concentrations of NH3-N and NO2--N were the high in flood season, and low in non-flood season, while the concentration of NO3--N pre- sented the opposite trend; the concentration of NO3--N was the highest in Shuangqiao estuary, where the pollution was the worst. DIN in Zhegao estuary and Xiaozhegao estuary was mainly caused by domestic sewage and industrial wastewaters; surface runoff and pollution from ships contribute the most to the DIN content in Shuangqiao estuary. [Conclusion] This study provided basic data and theoretical basis for the control and management of eutrophication in Chaohu Lake.
Viciafaba L. seedlings were hydroponically cultivated in 0-12 mg/L of extraneous lanthanum （La） for 15 d to investigate ecotoxicological effects and risk assessment of rare earth elements （REEs）. The results showed that reactive oxygen species （ROS） production such as superoxide radical （O2） and hydrogen peroxide （H202） were overproduced at higher concentrations of La, resulting in oxidatively modi- fied proteins and shoot growth retardation. While, superoxide dismutase （SOD）, catalase （CAT）, ascorbate peroxidase （APX） and guaiacol peroxidase （GPX） isoenzymes were elevated to some extent to eliminate excess of ROS. HSP70 production and endopeptidase isoenzymes were also enhanced, which were involved in repairing or degradation of the oxidatively modified proteins due to La. Thus, the antioxidant isoenzymes, endoprotease isoenzymes and HSP70 worked cooperatively to alleviate the La-induced oxidative damage. The significant en- hancement of CAT and APX isoenzymes and HSP70 could also be used as early bioindicators of La-polluted solution. The threshold dose range was firstly delimited as 1-2 mg/L of extraneous La, corresponding to 7.34-9.37 μg/g dry weight in the leaves. These results would be helpful to further understand the toxicological effects and possible mechanisms of REE（s） on crop seedlings.
