ALBERT

Description: The total suspended particulate (TSP) samples were collected from April 2013 to April 2014 at the urban location of Pokhara valley in western Nepal. The major aims were to study, quantify, and understand the concentrations and variations of TSP and major water-soluble inorganic ions (WSIIs) in the valley with limited data. The annual average TSP mass concentration was 135.50 ± 62.91 µg/m3. The average analyzed total WSIIs accounted for 14.4% of total TSP mass. Major anions and cations in TSP samples were SO42− and Ca2+, respectively. Seasonal differences in atmospheric conditions explain the clear seasonal variations of ions, with higher concentrations during pre-monsoon and winter and lower concentrations during the monsoon period. Neutralization factor calculations suggested that Ca2+ in the Pokhara valley mostly neutralizes the acidity in the atmosphere. Principle component analysis, NO3−/SO42− ratio, and non-sea salt fraction calculations suggested that the WSIIs in the valley were mostly derived from anthropogenic activities and crustal mineral dust, which was also supported by the results from precipitation chemistry over the central Himalayas, Nepal. In addition, back trajectories analysis has suggested that the air pollution transported from and through Indo-Gangetic Plains (IGP) during the dry periods, which has resulted in high ionic loadings during this period. Average NO3−/SO42− ratio was found to be 0.69, indicating the dominance of stationary sources of TSP in Pokhara valley. Secondary inorganic aerosols can have an adverse health impact on the human population in the valley. The data set from this one-year study provides new insights into the composition of WSIIs in the foothills of the Himalayas, which can be of great importance for understanding the atmospheric environment in the region.

Description: Solid fuel cooking stoves have been used as primary energy sources for residential cooking and heating activities throughout human history. It has been estimated that domestic combustion of solid fuels makes a considerable contribution to global greenhouse gas (GHG) and pollutant emissions. The majority of data collected from simulated tests in laboratories does not accurately reflect the performance of stoves in actual use. This study characterizes in-field emissions of fine particulate matter (PM2.5), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and total non-methane hydrocarbons (TNMHC) from residential cooking events with various fuel and stove types from villages in two provinces in China (Tibet and Yunnan) in the Himalayan area. Emissions of PM2.5 and gas-phase pollutant concentrations were measured directly and corresponding emission factors calculated using the carbon balance approach. Real-time monitoring of indoor PM2.5, CO2, and CO concentrations was conducted simultaneously. Major factors responsible for emission variance among and between cooking stoves are discussed.

Description: The Himalayas were recently identified as a global hotspot for deep stratosphere-to-troposphere transport (STT) in spring. Although the STT in this region may play a vital role in tropospheric chemistry, the hydrological cycle and aquatic ecosystems in Asia, there is no direct measurement of a chemical stratospheric tracer to verify and evaluate its possible impacts. Here, we use cosmogenic 35 S as a tracer for air masses originating in the stratosphere and transported downward. We measure concentrations of 35 S in fresh surface snow and river runoff samples collected from Mt. Everest in April 2013 to be more than 10 times higher than previously reported by any surface measurement, in support of the Himalayas as a gateway of springtime STT. In light of this result, measurements of 35 SO 2 and 35 SO 4 2- at Nam Co in spring 2011 are reanalyzed to investigate the magnitudes of stratospheric air masses from the Himalayas to the tropospheric sulfur cycle and surface O 3 level over the Tibetan Plateau. A simple one box model reveals that the oxidative lifetime of SO 2 is reduced in aged STT plumes. Triple oxygen isotopic measurements of sulfate samples suggest that enhanced O 3 levels may shift the oxidation pathway of SO 2 in the troposphere, which may be constrained by further intensive sampling and measurements. Comparison with surface O 3 measurements and traditional meteorological tracing methods shows that 35 S is a potentially unique and sensitive tracer to quantify the contribution of stratospheric air to surface O 3 levels in fresh or aged STT plumes.

Description: Nature Geoscience 10, 507 (2017). doi:10.1038/ngeo2967 Authors: Yindong Tong, Wei Zhang, Xuejun Wang, Raoul-Marie Couture, Thorjørn Larssen, Yue Zhao, Jing Li, Huijiao Liang, Xueyan Liu, Xiaoge Bu, Wei He, Qianggong Zhang & Yan Lin