Precipitation chemistry of Lhasa and other remote towns, Tibet

Abstract

The sampling and analysis were based on WMO recommendations for a background network with some modifications according to local conditions and environmental characteristics, which include the following precipitation constituents and related parameters: pH, conductivity, CO 2 partial pressure, total suspended particles, and the content of K

Major ion chemistry of the Yarlung Tsangpo–Brahmaputra river: Chemical weathering, erosion, and CO2 consumption in the southern Tibetan plateau and eastern syntaxis of the Himalaya

“…In tributaries of the Nyang Qu and the Po Tsangpo, greater than 60% of the drainages show no detectable Cl À in solution. Although these concentrations are generally lower than would be expected from studies of Himalayan precipitation (Niehoff et al, 1994;Galy and France-Lanord, 1999;Ping et al, 2000) they are not considerably different from the low Cl À concentrations (2.9 lM) measured in precipitation over the Tibet autonomous region (Table 2; Zhang et al, 2003). As a result, we assume that rain water additions to these two drainages are insignificant with the exception of Na + and Cl À .…”

“…In the lower Brahmaputra, up to 30% of Na + may be derived from marine sources (Sarin and Krishnaswami, 1984). In contrast, in parts of the southern Tibetan plateau, atmospheric deposition of carbonate-rich dust may exceed 150 lg cm À2 yr À1 (Wake et al, 1994a) and can result in precipitation with highly variable quantities of dissolved cations or high ratios of dissolved Ca 2+ to Cl À (Wake et al, 1993;Wake et al, 1994b;Zhang et al, 2003). Given the large degree of spatial variability in potential atmospheric contributions to stream waters over the area of study, we use several approaches to correct for potential atmospheric and hydrothermal additions to stream waters.…”

“…Tributaries draining into the lower and middle Yarlung Tsangpo are corrected for the addition of rain water inputs using the measured ion/Cl À ratio in precipitation in Lhasa (Table 2; Zhang et al, 2003) assuming rain has the Cl À content of the lowest concentrations measured in these streams, which is $1 lM Cl À . For tributaries along the upper Yarlung Tsangpo and for samples of the main stem of the Yarlung Tsangpo, we assumed that rainwater had a Cl À concentration of the stream with the lowest measured Cl À concentration (10 lM) and corrected for rainwater inputs using ion/Cl-ratios in precipitation from Lhasa (Zhang et al, 2003). For tributaries of the Siang-Tsangpo, dissolved Cl À concentrations are relatively constant over a large spatial extent and evaporites or hot springs are not believed to be significant sources of dissolved species.…”

Hydrochemistry of the middle and upper reaches of the Yarlung Tsangpo River system: weathering processes and CO2 consumption

“…The catchment receives most of the rain between June and September, and has its maximum discharge during this period (Huang et al 2011;Liu et al 2007). What is more, the evaporation is high and the average potential evaporation is 2000-2500 mm/year (Zhang et al 2003).…”

“…Since the catchment of middle and upper reaches of the Yarlung Tsangpo is relatively far from marine influence, rainwater data derived from literature are used (Table 3) (Zhang et al 2003). To address the additions of solute cations and Cl -from atmospheric input, the method of multiplying the measured molar concentration of each cation by the corresponding ion/Cl -ratio measured in rainwater is adopted.…”