21st Century Asian air pollution impacts glacier in northwestern Tibet

Abstract. Over the last four decades, Asian countries have undergone significant economic development leading to rapid urbanization and industrialization in the region. Consequently, fossil fuel consumption has risen dramatically worsening the air quality in Asia. Fossil fuel combustion emits particulate matter containing toxic metals that can adversely affect living organisms, including humans. Thus, it is imperative to investigate the temporal and spatial extent of metal pollution in Asia. Recently, we reported a continuous and high-resolution 1650–1991 ice core record from the Guliya ice cap in northwestern Tibet, China showing a contamination of Cd, Pb and Zn during the 20th century. Here, we present a new continuous and high-resolution ice core record of trace metals from the Guliya ice cap that comprises the years between 1971 and 2015, extending the 1650–1991 ice core record into the 21st century. Non-crustal Cd, Pb, Zn and Ni enrichments increased since the 1990s reaching a maximum in 2008. The enrichments of Cd, Pb, Zn, and Ni increased by ~ 75 %, 35 %, 30 %, and 10 %, respectively during the 2000–2015 period relative to 1971–1990. Our analysis suggests that emissions from Pakistan's fossil fuel combustion (by road transportation and the manufacturing and construction industries) became the dominant source of Cd, Pb, Zn, and Ni deposited on Guliya between 1995 and 2015. However, it is possible that emissions from Central Asia, Afghanistan, India, Nepal, and the Xinjiang province in China have also impacted Guliya during the 21st century. The enrichments of Cd, Zn, and Ni declined after 2008 likely due to a coal consumption decrease in Pakistan at that time. This new record demonstrates that the current emissions in Asia are impacting remote high-altitude glaciers in the region and that mitigation policies and technologies should be enforced to improve the air quality as economic development continues in most Asian countries.