Spatial distribution of the persistent organic pollutants across the Tibetan Plateau and its linkage with the climate systems: a 5-year air monitoring study

Abstract

Abstract. The Tibetan Plateau (TP) has been contaminated by persistent organic pollutants (POPs), including legacy organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) through atmospheric transport. The exact source regions, transport pathways and time trends of POPs to the TP are not well understood. Here polystyrene–divinylbenzene copolymer resin (XAD)-based passive air samplers (PASs) were deployed at 16 Tibetan background sites from 2007 to 2012 to gain further insight into spatial patterns and temporal trends of OCPs and PCBs. The southeastern TP was characterized by dichlorodiphenyltrichloroethane (DDT)-related chemicals delivered by Indian monsoon air masses. The northern and northwestern TP displayed the greatest absolute concentration and relative abundance of hexachlorobenzene (HCB) in the atmosphere, caused by the westerly-driven European air masses. The interactions between the DDT polluted Indian monsoon air and the clean westerly winds formed a transition zone in central Tibet, where both DDT and HCB were the dominant chemicals. Based on 5 years of continuous sampling, our data indicated declining concentrations of HCB and hexachlorocyclohexanes (HCHs) across the Tibetan region. Inter-annual trends of DDT class chemicals, however, showed less variation during this 5-year sampling period, which may be due to the ongoing usage of DDT in India. This paper demonstrates the possibility of using POP fingerprints to investigate the climate interactions and the validity of using PAS to derive inter-annual atmospheric POP time trends.

Occurrence and spatial distribution of neutral perfluoroalkyl substances and cyclic volatile methylsiloxanes in the atmosphere of the Tibetan Plateau

“…the Indian monsoon and westerly winds (Fig. S2, Wang et al, , 2016b. For example, DDT-related chemicals were major chemicals in the atmosphere of the south-eastern TP, which is influenced by the Indian monsoon air masses , whereas the north-western TP was dominated by HCB in the atmosphere caused by the westerly-driven European air masses (Wang et al, 2016b).…”

“…Taking advantage of the Tibetan Observation and Research Platform (Wang et al, 2016a), a passive air monitoring network comprising 16 sampling sites across the TP has been established with good spatial coverage of the TP ( in the Supplement) and has already produced results regarding the spatial and temporal pattern of legacy POPs (Wang et al, , 2016b. In this study, duplicate SIP-PASs were deployed at each sampling site for about 100 days from May to July for sampling PFASs (2011) andcVMSs (2013).…”

“…S2, Wang et al, , 2016b. For example, DDT-related chemicals were major chemicals in the atmosphere of the south-eastern TP, which is influenced by the Indian monsoon air masses , whereas the north-western TP was dominated by HCB in the atmosphere caused by the westerly-driven European air masses (Wang et al, 2016b). Similarly, ice cores collected in different regions of the TP indicated that PFOS existed in the Muztagata glacier (western TP), while in the Zuoqiupu glacier located in the eastern TP, PFOS was below the detection limit, but concentrations of short-chain perfluorobutanoic acid have increased during recent years (Wang et al, 2014).…”

“…In addition to the Arctic and Antarctic, the Tibetan Plateau (TP) is often referred to as the "third pole", isolated in the mid-latitude Northern Hemisphere with a harsh environment and high elevation. The transport (Sheng et al, 2013), distribution (Wang et al, , 2016b, and bioaccumulation (Ren et al, 2016) of legacy POPs in the Tibetan environment have already been investigated; however, there is still a gap in knowledge regarding the distribution of emerging organic contaminants, such as PFASs and cVMSs.…”

Molecular characterization of organic aerosol in Himalayas: insight from ultra-high resolution mass spectrometry

“…Previous studies conducted in the HTP have 62 focused on a limited number of molecular markers such as organic acids which are closely 63 related with biomass burning emission (Cong et al, 2015), and some toxicology species such as 64 polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants (POPs) which are 65 related with anthropogenic activities Wang et al, 2016). In addition, online 66 measurement using Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-67 ToF-AMS) had provided more details on the OA chemistry and sources with high time 68 resolution (Xu et al, 2018).…”