Increase of ambient PCDD/F concentrations in northern Taiwan during Asian dust storm and winter monsoon episodes

In the spring, Asian dust storms that originate in the deserts of Mongolia and China eventually reach the populated areas of East Asia. The dust storm particles usually contain diverse organic matter and nutrients that may have an adverse effect on human health. In winter, northeast monsoon episodes that originate in the mainland China not only bring cold air but also transport dust and air pollutants to Taiwan over long distances. Based on the above, the presence of persistent organic pollutants (POPs), including polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs), in the suspended particles undergoing long-range transport needs to be investigated. In this study, the atmospheric concentrations of PCDD/Fs were monitored and investigated during an Asian dust storm episode and northeast monsoon episode in northern Taiwan. The sampling results indicate that the atmospheric PCDD/Fs observed at two remote sampling sites ranged from 7.46 ± 0.7 to 37.2 ± 2.0 fg I-TEQ/m³ during the regular sampling period that covered 2006 and 2007. However, the concentrations of atmospheric PCDD/Fs increase to 61.0 and 69.8 fg I-TEQ/m³ during the Asian dust storm episode of 3^rd March 2008 and during a northeast monsoon episode on 3^rd December 2008, respectively. Specifically, higher levels of PCDFs (by 70%-76%) were measured in northern Taiwan during these long-range transport periods. As no specific dioxin emission sources exist within 20 km of our sampling sites, the increase in PCDD/F concentrations observed at these two remote sampling sites is likely to be related to the Asian dust storm and northeast monsoon episodes and the pollutants would seem to have come from mainland China.