Long-range southeastward transport of Asian biosmoke pollution: Signature detected by aerosol potassium in Northern Taiwan

Total potassium was determined in aerosol particles between 2002 and early 2007 in northern Taiwan (25 degrees 02'N, 121 degrees 31'E). Biosmoke potassium (non-sea-salt/noncrustal) was assessed and used as a tracer of biosmoke pollution, which essentially represents the combination of coal and biofuel combustion and biomass burning. PM10-associated potassium displays a typical seasonality, peaking during the winter and waning during the summer. The size distribution showed a bimodal pattern, peaking at a supermicron size (2.5-5.6 mu m) and at around 1 mu m, demonstrating multiple sources. Size distribution patterns revealed an evident seasonality, indicative of the different domination of natural and biosmoke sources in the two main periods of the northeasterly and summer monsoons, respectively. The relative contributions of biosmoke and natural sources to the total potassium were estimated to be 50-75% and 25-50%, respectively; the seasonality of biosmoke potassium is similar to that of total potassium. Substantial correlations existed between biosmoke potassium and selected trace metals (As, Se, Pb, and Mn), suggesting that the latter are essentially associated with biosmoke pollution. Another significant finding is that the seasonal mean concentrations of aerosol potassium between 2002 and early 2007 tend to increase. This could primarily be attributed to the increased consumption of coal in China, posing an urgent issue relevant to pollution mitigation in China. The southward inflow flux of biosmoke potassium to the south of 25 degrees N during the northeasterly monsoon months has been estimated to be 56-79 mg m(-2) d(-1), which could be applied to the assessment of other biosmoke-related species.