Bin Qu

River water quality across the Himalayan regions: elemental concentrations in headwaters of Yarlung Tsangbo, Indus and Ganges River

Abstract To study the water quality across the Himalayan region, a total of 43 river water samples were collected in September 2012 from the Yarlung Tsangbo (Brahmaputra), Indus and Ganges basins. We measured the common water quality parameters (pH, EC, TDS, and water temperature) and analyzed the element concentrations (As, Cr, S, Sr, Tl, B, Ba, Ca, Al, Fe, K, Mg, Mn, Na, Rb, and Ti) using ICP-AES. The results show that all the rivers have an alkaline environment with pH from 7.9 to 8.9. TDS has a positive relationship with Ca and Mg concentrations. The elemental contents are comparable among the samples from different river basins. The enrichment factor of As in river water across Himalayas showed a high value at 30, indicating the impacts of anthropogenic activities. The river water quality in this region is under the influence of climate change on the glacier melting, which will affect the water chemistry and the seasonal discharge of river runoff.

Deposition and light absorption characteristics of precipitation dissolved organic carbon (DOC) at three remote stations in the Himalayas and Tibetan Plateau, China

The concentrations, depositions and optical properties of precipitation DOC at three remote stations (Nam Co, Lulang and Everest) were investigated in the Himalayas and Tibetan Plateau (HTP). The results showed that their volume-weighted mean DOC concentrations were 1.05±1.01mgCL-1, 0.83±0.85mgCL-1 and 0.86±0.91mgCL-1, respectively, close to those of other remote areas in the world and lower than those of typical polluted urban cities. Combined with precipitation amounts, the DOC depositions at these three stations were calculated to be 0.34±0.32gCm-2yr-1, 0.84±0.86gCm-2yr-1 and 0.16±0.17gCm-2yr-1, respectively. The annual DOC deposition in the HTP was approximately 0.94±0.87TgC, the highest and lowest values appeared in the southeastern and northwestern plateau, respectively. The sources of DOC in the precipitation at these three stations were remarkably different, indicating large spatial heterogeneity in the sources of precipitation DOC over the HTP. Nam Co presented combustion sources from South Asia and local residents, Lulang showed biomass combustion source from South Asia, and Everest was mainly influenced by local mineral dust. The values of the MACDOC at 365nm were 0.48±0.47m2g-1, 0.25±0.15m2g-1, and 0.64±0.49m2g-1, respectively, for the precipitation at the three stations. All of these values were significantly lower than those of corresponding near-surface aerosol samples because precipitation DOC contains more secondary organic aerosol with low light absorption abilities. Additionally, this phenomenon was also observed in seriously polluted urban areas, implying it is universal in the atmosphere. Because precipitation DOC contains information for both particle-bound and gaseous components from the near surface up to the altitude of clouds where precipitation occurs, the MACDOC of precipitation is more representative than that of near-surface aerosols for a given region.

Aged dissolved organic carbon exported from rivers of the Tibetan Plateau

The role played by river networks in regional and global carbon cycle is receiving increasing attention. Despite the potential of radiocarbon measurements (14C) to elucidate sources and cycling of different riverine carbon pools, there remain large regions such as the climate-sensitive Tibetan Plateau for which no data are available. Here we provide new 14C data on dissolved organic carbon (DOC) from three large Asian rivers (the Yellow, Yangtze and Yarlung Tsangpo Rivers) running on the Tibetan Plateau and present the carbon transportation pattern in rivers of the plateau versus other river system in the world. Despite higher discharge rates during the high flow season, the DOC yield of Tibetan Plateau rivers (0.41 gC m-2 yr-1) was lower than most other rivers due to lower concentrations. Radiocarbon ages of the DOC were older/more depleted (511±294 years before present, yr BP) in the Tibetan rivers than those in Arctic and tropical rivers. A positive correlation between radiocarbon age and permafrost watershed coverage was observed, indicating that 14C-deplted/old carbon is exported from permafrost regions of the Tibetan Plateau during periods of high flow. This is in sharp contrast to permafrost regions of the Arctic which export 14C-enriched carbon during high discharge periods.

Greenhouse gases emissions in rivers of the Tibetan Plateau

Greenhouse gases (GHGs) emissions from streams are important to regional biogeochemical budgets. This study is one of the first to incorporate stream GHGs (CO2, CH4 and N2O) concentrations and emissions in rivers of the Tibetan Plateau. With one-time sampling from 32 sites in rivers of the plateau, we found that most of the rivers were supersaturated with CO2, CH4 and N2O during the study period. Medians of partial pressures of CO2 (pCO2), pCH4 and pN2O were presented 864 μatm, 6.3 μatm, and 0.25 μatm respectively. Based on a scaling model of the flux of gas, the calculated fluxes of CO2, CH4 and N2O (3,452 mg-C m2 d−1, 26.7 mg-C m2 d−1 and 0.18 mg-N m2 d−1, respectively) in rivers of the Tibetan Plateau were found comparable with most other rivers in the world; and it was revealed that the evasion rates of CO2 and CH4 in tributaries of the rivers of the plateau were higher than those in the mainstream despite its high altitude. Furthermore, concentrations of GHGs in the studied rivers were related to dissolved carbon and nitrogen, indicating that riverine dissolved components could be used to scale GHGs envision in rivers of the Tibetan Plateau.

Correction: Aged dissolved organic carbon exported from rivers of the Tibetan Plateau

[This corrects the article DOI: 10.1371/journal.pone.0178166.].