Organic persistent toxic substances in soils, waters and sediments along an altitudinal gradient at Mt. Sagarmatha, Himalayas, Nepal

Identification of sources of polycyclic aromatic hydrocarbons based on concentrations in soils from two sides of the Himalayas between China and Nepal

“…Mean concentrations of Fl and Acy in the soils were 53 and 43 ng/g, dw, which accounted for 29% and 22% of the mean concentration of total PAHs, respectively (Table 1). This result differed from that reported by Guzzella et al (2011), who found Phe and Pyr to be dominants in soils of Sagarmatha Nation Park of Nepal. The mean concentration of PAHs in soils from the SSHN, was significantly greater than that in the soils from the NSHC (T test; p < 0.05).…”

“…Altitude is another important factor that can influence the soil PAH distributions in the Himalayan Mountains (Guzzella et al, 2011). For the five soils selected from the NSHC, the concentrations of Phe, Flu and Acy were significantly and positively correlated with altitude (Fig.…”

“…One reason for the weak correlation between the concentrations of LMW-PAHs in the soils of Nepal and altitude is the fact that Nepal is more strongly influenced by the Indian monsoon and has a greater spatial variation of altitude and precipitation than the TPC. However, because HMW-PAHs are less volatile, generally less abundant in suspended aerosols, transported by air over short distances and influenced greatly by local human activities (Wania and Mackay, 1993;Guzzella et al, 2011), it is difficult to determine the complex relationships between their concentrations and the altitude on regional scales. Based on above observations, it is easy to conclude that the significant and positive relationships between S 16 PAH concentrations and altitude occurred in our study because concentrations of LMW-PAHs contributed more than 70% to those of S 16 PAHs in both China and Nepal (Table 1).…”

“…The altitudinal dependence of the concentrations of the more volatile compounds is also called the "cold trap effect" (Wania and Mackay, 1993;Wang et al, 2006). Greater precipitation in the NSHC, often in the form of snow, which is thought to be a very efficient scavenger of more volatile PAHs (Loewen et al, 2005;Guzzella et al, 2011), could provide a significant mechanism for the deposition of PAHs in soils in high altitude areas. One reason for the weak correlation between the concentrations of LMW-PAHs in the soils of Nepal and altitude is the fact that Nepal is more strongly influenced by the Indian monsoon and has a greater spatial variation of altitude and precipitation than the TPC.…”

Altitudinal and Spatial Signature of Persistent Organic Pollutants in Soil, Lichen, Conifer Needles, and Bark of the Southeast Tibetan Plateau: Implications for Sources and Environmental Cycling

“…Sagarmatha, Himalayas. 35 Unlike OCPs, which mainly come to the study area via longrange transport, PAHs may originate also from local combustion sources including residential cooking and heating, transportation vehicles, and road construction. 36 In addition, PAHs, particularly those in the vapor phase, are generally more susceptible to photolysis than OCPs during long-range transport, complicating and weakening the cold-trappingrelated altitudinal trend.…”