The samples of total suspended particle (TSP) from sources and TSP in the ambient atmosphere were collected in 2006 at Tianjin, People's Republic of China and analyzed for 16 chemical elements, two water-soluble ions, total carbon, and organic carbon. On the basis of the chemical mass balance (CMB) model, the contributions of different TSP sources to the ambient TSP were identified. The results showed that resuspended dust has the biggest contributions to the concentration of ambient TSP. The buffering capacity of each TSP source was also determined by an analytical chemistry method, and the result showed that the constructive dust (the dust emitted from construction work) had the strongest buffering capacity among the measured sources, whereas the coal combustion dust had the weakest buffering capacity. A calculation formula of the source of buffering capacity of ambient TSP was developed based on the result of TSP source apportionment and the identification of the buffering capacity of each TSP source in this study. The results of the source apportionment of the buffering capacity of ambient TSP indicated that open sources (including soil dust, resuspended dust, and constructive dust) were the dominant sources of the buffering capacity of the ambient TSP. Acid rain pollution in cities in Northern China might become serious with a decrease of open source pollution without reducing acidic sources. More efforts must be made to evaluate this potential risk, and countermeasures should be proposed as early as possible.
Acid rain is a serious environmental problem that has affected China since the 1980s, especially Southern China. (1), (2) In recent years, the acidity of rain has been increasing in cities of Northern China that were seldom troubled by acid rain before. (1) The trend of increasing acid rain in cities of Northern China requires the attention of the environmental management system.
Northern China's cities often suffer from several kinds of atmospheric pollutants, such as particulate matter (PM) and sulfur dioxide ([SO.sub.2]). PM is the primary atmospheric pollutant in most cities of Northern China. (1) Total suspended particle (TSP; aerodynamic diameter [less than or equal to]100 μm) has a high level of concentration. (1) Earlier research found that TSP had great capacity to buffer acid rain because of its alkaline components, (2-11) and several studies of the buffering capacity of the ambient PM have been implemented. (12-16) The buffering capacity of ambient TSP can be reflected by the pH value and the chemical compositions in the rainwater of this region, as shown in Table 1. Although the concentration of sulfate and nitrate remains at a high level, the pH values of the rainwater are around 6 because of the high concentration of calcium that mainly comes from the washout process of ambient TSP during precipitation. (9), (17), (18)Table 1. Annual variation of chemical compositions in rainwater of Beijing, China (μeq/L). Year [SO.sub.4.sup.2-] [NO.sub.3.sup.-] [Ca.sup.2-] [p.sup.H] 1986 (15) 154.5 39.5 151.6 6.29 1993 (16) 151.9 49.8 143.2 5.98 2003 (9) 380.1 117.9 159.0 6.48
The distribution area of acid...