This paper describes 2007/2008 inter-annual changes in runoff from the Zhadang Glacier located on the northern slope of Nyainqêntanglha Range,Tibet,and analyzes their causes.Precipitation increased by 17.9%in summer months of 2008 compared with the same period in 2007,drainage basin runoff decreased by 33.3%,and glacial meltwater decreased by 53.8%.Change in positive accumulated air temperature explained approximately half of the inter-annual difference in glacial meltwater using a degree-day model.This suggests that the glacier is extremely sensitive to changes in air temperature.Energy balance analysis showed that change in glacier surface albedo,considered to be caused by difference in precipitation form,resulted in the large inter-annual difference in glacial meltwater.It was shown statistically that precipitation form in the summer months of 2007 was mainly rainfall which comprised 71.5%of total precipitation,while during the same period in 2008 rainfall accounted for 30.7%,with the majority of precipitation falling as snow.Precipitation form should be considered an independent factor when analyzing glacier sensitivity to climate change or forecasting the runoff from certain glaciers.
To assess the seasonality of aerosol deposition and anthropogenic effects on central Himalayas, a 1.85-m deep snow pit was dug on the northern slope of Mt. Qomolangma （Everest）. Based on the morphology and energy dispersive X-ray （EDX） signal, totally 1500 particles were classed into 7 groups： soot; aluminosilicates; fly ash; calcium sulfates; Ca/Mg carbonates; metal oxides; and biological particles and carbon fragments. The size distribution and number fractions of different particle groups exhibited distinct seasonal variations between non-monsoon and monsoon periods, which are clearly related to the differences in air mass pathways. Specifically, the relative abundance of soot in non-monsoon period （25%） was much higher than that in monsoon period （14%）, indicating Mt. Qomolangma region received more anthropogenic influence in non-monsoon than monsoon period.
The Yarlung Zangbo River is the highest river in the world.It flows from west to east through the southern part of Tibet.The mercury(Hg)speciation and distribution in surface waters and soils near the bank of the Yarlung Zangbo River and its two tributaries,the Lhasa and Niyang Rivers,were investigated in June 2007.Simultaneously,major water quality parameters were also measured at the same stations.Total Hg(THg)and total methylmercury(TMeHg)concentrations in surface waters of the Yarlung Zangbo River ranged from 1.46 to 4.99 ng/L and from 0.06 to 0.29 ng/L,respectively,representing the background levels in river systems of the Tibetan Plateau.Particulate Hg(PHg)accounted for 69%of the THg,and the two Hg species had a significant relationship(r=0.990,P<0.01).Approximately 61%of the spatial distribution of THg was controlled by the concentrations of total suspended particles(TSP).Reactive Hg(RHg)concentrations ranged from 0.10 to 0.36 ng/L,and this fraction may play a weak role in terms of the transport and fate of Hg in surface waters.Dissolved methylmercury(DMeHg)constituted 71%of the TMeHg and was significantly correlated with TMeHg(r=0.746,P<0.01).The spatial distribution of TMeHg is not strongly affected by environmental factors such as THg,RHg,temperature,pH,dissolved organic carbon(DOC),and TSP.In addition,the inflow of both the Lhasa and Niyang Rivers probably influences the concentrations of THg in surface waters of the mainstream, but such an effect is not obvious for TMeHg.
