Abstract: In order to make clear whether the sediment in Aha Reservoir was contaminated by the mercury (Hg) from mining wastewater drainage, an investigation was conducted on the vertical distribution patterns of total Hg (THg) and methyl Hg (MeHg) in the sediment. The THg concentration in the sediment ranged from 160 to 252 ng·g^-1, with an average of 210 ng·g^-1, being obviously higher than that in uncontaminated lakes. The THg concentration increased with sediment depth, which was related to the sediment environment. The MeHg concentration varied from 0.2 to 7.2 ng·g^-1, with an average of 1.8 ng·g^-1. In the period with abundant water, the MeHg concentration decreased with sediment depth, and that in sedment surface layer was obviously higher, as compared in low water period, which was related to the increased organic matter content and anaerobic enviroment in sedment surface layer in abundant water period.

Key words: Rice, Free air CO₂ enrichment, Biomass accumulation and partition, Soluble carbohydrates, Leaf area index, Net assimilation rate