Trans-Himalayan transport of organochlorine compounds: Three- year observations and model-based flux estimation

Journal Article · Tue Jun 18 00:00:00 EDT 2019 · Environmental Science & Technology

DOI:https://doi.org/10.1021/acs.est.9b01223· OSTI ID:1567255

Gong, Ping ^[1]; Wang, Xiaoping ^[2]; Pokhrel, Balram ^[3]; Wang, Hailong  ^[4]; Liu, Xiande ^[5]; Liu, Xiaobo ^[1]; Wania, Frank ^[6]

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1. Institute of Tibetan Plateau Research, Chinese Academy of Sciences
2. Chinese Academy of Sciences
3. 1) School of Science, Kathmandu University, Nepal
4. BATTELLE (PACIFIC NW LAB)
5. Chinese Research Academy of Environmental Sciences
6. University of Toronto

Due to their low temperature and high precipitation, high mountains can trap semi-volatile chemicals, such as persistent organic pollutants (POPs), and hinder their dispersion. However, deep convection occurring at high elevation facilitates the upward transport of POPs, and mountain valleys provide channels for regional transport of POPs. The concerted impact of these processes on the transport of contaminants across a mountain range has not been investigated before. In this study, we conducted a three-year passive air sampling campaign along a south-north altitudinal transect (100-5200m) across the central Himalayas, the highest mountain range on Earth. A multi-compartment contaminant fate model was developed to simulate the fate and transport of POPs along this transect and an adjacent mountain valley. The results show that driven by the strong Indian monsoon, POPs emitted in the lowlands at the foot of the Himalayas can be transported northward to high altitudes and further to the inner part of the Tibetan Plateau. Modeling suggests that more than 90% of POPs are trapped along the way due to gaseous deposition to soil and foliage and rainfall scavenging; we estimate that in spite of this removal, 2×10-3 to 1×10-1 Giga-grams of POPs are transported across the Himalayas every year. This indicates that despite their height the Himalayas are not a perfect barrier to the North-bound transport of POPs. We further compared the contributions that valleys and high altitudes make to the transport of POPs. The transport flux along valleys is 2-3 times higher than that across the mountain ridge. However, due to the limited spatial coverage of mountain valleys, the amount of POPs transported through valleys only accounts for a small part of the total transport, demonstrating that high altitude transport across the mountain ridge is the dominant transport pathway. This study shows that POPs can overcome the blocking effect of the Himalayas and the transport does not depend on the ability to pass through lower-lying mountain passes.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1567255
• Report Number(s): PNNL-SA-143688
• Journal Information: Environmental Science & Technology, Vol. 53, Issue 12
• Country of Publication: United States
• Language: English