Further research on the factors contributing to oxygen concentration over the Qinghai-Tibet Plateau

Abstract

<p indent=0mm>The oxygen concentration in near-surface air, which has been previously documented to be nearly constant (~20.946%), varies due to photosynthesis, respiration, and combustion processes, including combustion of fossil fuels. As the biggest and highest plateau in the world, the Qinghai-Tibet Plateau (QTP) hosts the largest high altitude population and tourists. The hypoxic environment of the QTP challenges its inhabitants and visitors both physically and psychologically. Health problems associated with the exposure to high altitude have long been observed by the scientific community. However, few studies have investigated the key drivers and their contribution to spatio-temporal oxygen concentration variations over the QTP. To fill this gap, a field investigation conducted along the Qinghai-Tibet National Highway in the summer of 2017 found that, in addition to altitude, vegetation and weather conditions may also impact on oxygen concentrations. Subsequent investigations during 2018−2020 along other national highways and within the Qinghai Lake region, the Qilian Mountains and their vicinities recorded a total of 487 samples. These observations showed clear spatial and seasonal variations in oxygen concentrations. Statistical analysis showed that oxygen concentration is positively affected by air temperature and fractional vegetation cover (FVC) but decreases with altitudes. The Lindeman, Merenda and Gold (LMG) method showed that the relative contributions of altitude, air temperature, and FVC to oxygen concentration were 46.69%, 31.64% and 3.44%, respectively, jointly explaining ~82% of the total variance in oxygen concentration. The remaining unexplained variance could be possibly due to factors such as vegetation net primary productivity (NPP) and soil heterotrophic respiration. Spatio-temporal variations in oxygen concentration are likely caused by the oxygen production from photosynthesis and soil heterotrophic respiration and by changes in atmospheric density resulting from topography and near-surface air temperature. Under a warming climate, improved vegetation cover and higher air temperature over the QTP could increase oxygen concentration and, to some extent, reduce the risks of hypoxia in the populations of the QTP. These findings improve our understanding of the spatio-temporal variations in oxygen concentration over the QTP in the context of climate change. The results can also be used to support the health and safety of residents and tourists and promote the sustainable development of high altitude regions worldwide.