[1] In spring 2005, daily particulate matter (PM 2.5 ) aerosol samples were collected at Tongliao, a site in the Horqin sand land of northeastern China. The concentrations of 20 elements, 9 water-soluble ions, and elemental and organic carbon (EC and OC, respectively) were determined in the filter samples. Crustal material was the major contributor to the PM 2.5 mass, but rural biomass burning and local urban pollution also influenced the composition of the aerosol. The mean PM 2.5 mass concentration was 126 ± 71 mg m À3 (arithmetic mean ± standard deviation), with higher loadings during five dust storms (DS, 255 ± 80 mg m À3 ) than for normal days (ND, 104 ± 43 mg m À3) or pollution episodes (PE, 118 ± 52 mg m À3 ). During the DS, crustal material accounted for 69% of the PM 2.5 mass, followed by carbonaceous matter (14%), sulfate (4%), nitrate (2%), ammonium (1%), and chloride (1%). The observed Si/Al, Ca/Al, and Fe/Al ratios during the DS events were different from those in dust from western or central/northern Asia. On normal days the percentage of crustal material decreased to 43%, and the mass of carbonaceous matter increased 2 times over that during DS. During the pollution episodes the contributions of sulfate and nitrate were 3 times those on DS while ammonium increased four-fold. Secondary aerosols (NH 4 + , SO 4 2À, and NO 3 À ) were the dominant species during the pollution episodes, but SO 4 2À and NO 3 À also were important components of the aerosol during DS events, suggesting that mineral dust was mixed with other materials. Ion balance calculations indicate that the DS samples were alkaline, the ND samples were weakly alkaline, and the PE samples were slightly acidic. A deficit of measured anions during DS implied the presence of carbonate; this evidently accounts for $5.5% of the PM 2.5 mass. The average OC and EC concentrations were 16.3 ± 7.3 mg m À3 and 3.4 ± 1.7 mg m À3 , respectively. Noncrustal K was correlated with OC and EC, indicating that biomass burning was a major contributor to the regional carbonaceous aerosol.

Peatlands provide a widespread terrestrial archive for Holocene study. However, little is known about the grain-size characteristics of peaty sediments and their environmental significance. In order to study these phenomena in detail, two sections from the Hani and Gushantun peatlands in the Changbai Mountain Area were cored and sub-sampled. Based on reliable calibrated AMS 14 C ages, we established grain size variations in the peat cores since 15.6 ka cal. BP. Our results showed that the peaty sediments in the Changbai Mountains are mainly composed of silt. Moreover, the grain size component, which is related to paleoclimate variables, can be classified into three groups based on the "Grain size class vs. standard deviation" method. These sensitive grain size components are <37.0 μm (Component 1 or C1), 37.0-497.8 μm (Component 2 or C2) and >497.8 μm (Component 3 or C3). C1 comprises the finest silt in the peaty sediment and is mainly conveyed by the East Asian winter monsoon (EAWM), whereas C2 is transported into the peatland by surface runoff related to the enhancement of the East Asian summer monsoon (EASM). C3 is conveyed in saltation and bed-load mode by strong surface runoff linked to high-energy flow caused by a strong EASM, and perhaps is an indicator of extreme rainfall events in the Changbai Mountains. Our results suggest that the study region was dominated by a cold/dry environment during the late-glacial period under a strong EAWM. However, there was a marked climatic shift from an EAWM-dominated cold/dry climate to an EASM-dominated more mesic environment during the early Holocene. Increased percentage of C2 in peat cores during the Holocene Optimum (9.0-4.5 ka) indicates abundant rainfall in the study region (even with extreme rainfall events) as a result of a significant enhancement of the EASM. Weak monsoon events occurred at 10.5 ka, 9.2 ka, 8.2 ka, 7.2 ka, 6.2ka, 5.5 ka and 4.2 ka shown by sharp decreases in C2, agreeing with the stalagmite δ 18 O records in China. The results obtained from environmentally sensitive grain-size component records are largely consistent with other palaeoenvironmental records in the East Asian monsoon area, substantiating the regional climate patterns and monsoon evolution since late-glacial time. Because intensity of the East Asian monsoon is likely responsible for the grain-size change in the peat samples, the grain size components in peat samples may be used for reconstructions of past environmental conditions and of variability in the East Asian monsoon.

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