Long-range atmospheric transport of persistent organochlorinated compounds from south and mainland south-eastern Asia to a remote mountain site in south-western China

Abstract

A range of organochlorinated compounds have been consumed in China, India and the countries of mainland southeast Asia (MSA). Considering their persistence in the environment and ability in longrange atmospheric transport (LRAT), the potential outflow of these compounds from this region is therefore of great concern in the context of the global distribution of toxic chemicals. As part of a monitoring campaign aimed at investigating the LRAT of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) from southern China, MSA and northern India, atmospheric levels of OCPs and PCBs were measured once a week from October 2005 through December 2006 at Tengchong Mountain (TM), a remote site located in south-western China. The average concentrations of OCPs were found to be higher than those in other remote stations in the Arctic and the Tibetan plateau, except for a-hexachlorocyclohexane (a-HCH). A high level of b-HCH and low a-HCH/b-HCH ratio was attributed to an accidental release of b-HCH from unknown sources, besides obvious evidence of lindane (g-HCH) and technical HCH usage. Temporal variations of chlordanes and endosulfan were related to the usage pattern of these compounds, as well as LRAT. In contrast, dichlorodiphenyltrichloroethane (DDT) exhibited a relatively minor seasonal variation. The OCP levels at the monitoring site were found to be related to the air parcel back trajectories on the basis of four distinct clusters. Elevated levels of HCHs and DDTs were observed when air parcels originated from northern India where considerable OCP usage was reported recently, while high levels of g-HCH and TC (trans-chlordane) were mainly associated with air masses from southern China and northern MSA. The study highlighted the high background level of OCPs as well as their temporal patterns of trans-boundary LRAT in the MSA region.

Current status of persistent organic pesticides residues in air, water, and soil, and their possible effect on neighboring countries: A comprehensive review of India

“…In contrast to this, Li et al (2006) found the source of OCPs in Lhasa to be current use and local emission. Xu et al (2011) studied the transportation characteristics of OCPs and their potential sources at remote stations, such as Tengchong Mountain (TM) in the south-western part of China, and found elevated levels of HCHs and DDTs in the air. Potential source contribution function (PSCF) analysis suggests that high levels of OCPs at TM are mainly caused by LRAT from India and Southern China.…”

Ambient Air Levels of Organochlorine Pesticides at Three High Alpine Monitoring Stations: Trends and Dependencies on Geographical Origin

“…Becker et al (2011) estimated that in the Arctic environment, air masses from temperate, subtropical, and tropical regions may contribute to the amount of endosulfan I in the ratio of 57:40:3, respectively, and of endosulfan II in the ratio of 66:33:1, respectively. For a remote mountain site in southwestern China, Xu et al (2011) found that HCH and DDT levels increased when air masses originated from India and Southeast Asia during the summer monsoon. Generally, the movement of air masses containing OCPs to Europe and the European Alps may occur during warmer seasons, when higher temperatures increase the mobility of semivolatile compounds.…”

Boundaries of air mass trajectory clustering: key points and applications

“…Two types of sites have been the object of such analyses. The first comprises remote areas where measurements are scarce or are assumed to be clean (Xu et al 2011), and the second comprises areas that are especially polluted (Lv et al 2015).…”