Distribution of Persistent Organic Pollutants in Soil and Grasses Around Mt. Qomolangma, China

Abstract

Previous literature has reported the fate of persistent organic pollutants (POPs) in mountainous regions, but the Himalayas have received little attention, and few results from this region have been published. The present study collected soil and grass samples from the Mt. Qomolangma (Everest) area, central Himalayas, China, from the elevation range 4700 to 5620 m. We analyzed all samples for organochlorine pesticides (OCPs) to determine the level of OCP contamination in the Qomolangma region. The soil samples contained 0.385 to 6.06 ng g(-1) of DDT only, and these concentrations were lower than those from Europe and mountains close to industrial emissions. Our study detected a number of OCPs in the grass samples, such as hexachlorocyclohexane (HCH) (0.354 to 7.82 ng g(-1)), hexachlorobenzene (HCB) (0.0156 to 1.25 ng g(-1)), endosulfan (0.105 to 3.14 ng g(-1)), and DDT components (1.08 to 6.99 ng g(-1)). Their concentrations were higher than those in pine needles from Alberta, Canada. Our measurements of HCH and DDT in grass samples showed the same or slightly higher concentration levels than reported in moss from Mt. Qomolangma 15 years ago. This result and the analysis of isomer ratios (alpha/gamma-HCH and p-p'-DDE/p-p'-DDT) indicate recent releases of OCPs from a nearby region, possibly from dicofol use in India. We also investigated the elevation distribution of OCPs and found that HCH and HCB were progressively concentrated in colder, higher elevation sites. A bioconcentration factor (BCF) of grass was calculated, and the BCF values increased with the increasing elevation, indicating that the cold condensation of POPs at high-elevation sites may increase the potential threat to vegetation and the food chain in the mountain ecosystem.