The secondary nature and light absorption properties of water-soluble organic carbon in the winter of Beijing

From December 26th to 28th, 2014, Beijing was hit by the regional severely polluted weather, during which the daily average mass concentration of PM2.5 was three times that of non-polluted days. Water-Soluble Organic Carbon (WSOC) concentrations (6.8 mu g C/m(3)) in the polluted day were four times that of the non-polluted day (1.7 mu g C/m(3)). The high correlation between WSOC and Secondary organic carbon (SOC) indicated that WSOC and SOC shared similar source and formation mechanism. The high correlation between WSOC and biomass burning tracer (K+) indicated that biomass burning was an important source of WSOC in winter. This paper measures the light absorption intensity of water-soluble brown carbon on the average light absorption (Abs(365)) of WSOC between 360mm and 370 nm. The absorption spectrum analysis of WSOC showed that Abs(365) ranged from 0.80-15.26 with an average of 3.7 Mm(-1). The AAE value was 3.42 with the fluctuation range between 1.8 and 7.7. The mean value of MAE was 1.87 m(2)/g, with no significant difference between day and night. The WSOCMAE in polluted days was 1.96 m(2)/g and in the non-polluted day was 1.86 m(2)/g. In general, the absorbance capacity of WSOC in the polluted days was greater than that in the non-polluted days.