Decoupling Natural and Anthropogenic Mercury and Lead Transport from South Asia to the Himalayas

Mercury (Hg) and lead (Pb) accumulation since the Industrial Revolution has been generally observed to increase concurrently in lake sedimentary records around the world. Located downwind during the monsoon season from the rapidly developing South Asia, the Himalayas and the Tibetan Plateau are expe...

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Bibliographic Details
Published in:Environmental Science & Technology
Main Authors: Huang, Jie, Kang, Shichang, Yin, Runsheng, Lin, Mang, Guo, Junming, Ram, Kirpa, Li, Chaoliu, Sharma, Chhatra, Tripathee, Lekhendra, Sun, Shiwei, Wang, Feiyue
Format: Report
Language:English
Published: AMER CHEMICAL SOC 2020
Subjects:
Engineering
Environmental Sciences & Ecology
Environmental
Environmental Sciences
ISOTOPIC COMPOSITION
TIBETAN PLATEAU
ATMOSPHERIC DEPOSITION
ALPINE LAKE
ICE CORE
SEDIMENTS
DUST
PB
SIGNATURES
RECONSTRUCTION
Alpine Lake
Indian
ice core
Online Access:http://ir.gig.ac.cn/handle/344008/59431
https://doi.org/10.1021/acs.est.0c00429
Description
Summary:Mercury (Hg) and lead (Pb) accumulation since the Industrial Revolution has been generally observed to increase concurrently in lake sedimentary records around the world. Located downwind during the monsoon season from the rapidly developing South Asia, the Himalayas and the Tibetan Plateau are expected to receive direct anthropogenic Hg and Pb loadings, yet the source, pathway, and effects of such transport remain poorly known due to logistic challenges in accessing this region. When studying the sediment record from Lake Gokyo (4750 m above sea level (a.s.l.)) in the Himalayas, we find remarkably different Hg and Pb accumulation trends over the past 260 years. Although Hg accumulation has continued to increase since the Industrial Revolution, Pb accumulation peaked during that time and has been decreasing since then. Stable isotope analysis reveals that the decoupling trends between these two elements are due to different sources and pathways of Hg and Pb in the region. Both delta Hg-202 and Delta Hg-199 have been increasing since the Industrial Revolution, suggesting that anthropogenic Hg emissions from South Asia have been continuously increasing and that the Indian monsoon-driven wet deposition of atmospheric Hg is the dominant pathway for Hg accumulation in the sediments. In contrast, analysis of Pb-206/Pb-207 and (208)pb/Pb-207 ratios suggests that Pb accumulation in the sediments originates primarily from natural sources and that the decreasing trend of Pb accumulation is most likely due to a weakening input of atmospheric mineral dust by the westerlies. These decoupling trends highlight the ongoing issue of transboundary Hg transport to the Himalayas and the Tibetan Plateau that are source waters for major freshwater systems in Asia and calls for regional and international collaborations on Hg emission controls in South Asia.

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