RESUMEN
Based on hourly concentration data from six state-controlled air quality monitoring stations in urban area of Changzhou from December 2014 to November 2015, the seasonal variation of PM2.5 pollution was analyzed, and the contributions of PM10, four kinds of gaseous pollutants and seven meteorological factors to daily changes of ρ(PM2.5) were quantified by boosted regression tree (BRT). The results showed that:the seasonal differences of PM2.5 pollution were significant, the pollution was serious in winter and the pollution duration was long, while the pollution was light in summer. The spatial distribution of ρ(PM2.5) in four seasons was different, but the six monitoring stations showed similar trends in each season. Daily average ρ(PM2.5) was simulated and verified by BRT. The correlation coefficient of the training data was 0.981, and the cross-validation correlation coefficient was 0.957. In addition, the mean deviation between the simulated values and the measured values was 1.80%, and the standardized mean error was 10.41%, which showed that the model fitted well. The contribution percentages of four kinds of impact types (PM10, gaseous pollutants, meteorological factors and regional transport and diffusion) to daily average ρ(PM2.5) changes of four seasons were 23.4%, 28%, 36.2% and 12.6%, respectively. So, the most significant affecting factor was meteorological condition, followed by secondary formation, primary emission, and regional transport and diffusion. In the factors with contribution percentages of more than 5%, the daily average ρ(PM2.5) was positively associated with PM10, relative humidity, CO and O3, and was negatively correlated with temperature, SO2 and mixed layer high. In addition, the daily average ρ(PM2.5) had complex relationships with atmospheric pressure and NO2. For regional transport and diffusion, the polluted air flow from southeast, west and north had a relatively great negative impact on PM2.5 pollution of urban area in Changzhou.
RESUMEN
Totally 126 samples of windowsill dust were collected from different floors along elevated road in Changzhou. The concentrations of Cu, Zn, Pb, Cd, Ni and Cr were determined, and the vertical distribution and chemical speciation were analyzed. The enrichment factor, bioaccessiblity, potential ecological risk and health risk were evaluated. The results showed that the average contents of Cu, Zn, Pb, Cd, Ni and Cu were 181.95, 709.99, 211.24, 2.76, 101.59 and 257.55 mg·kg-1 respectively, which were all higher than the background value. The enrichment factor of Cd was 33.05, with enrichment degree of strongly enriched. The enrichment degrees of Cu, Pb and Zn were all significantly enriched. These four heavy metals may come not only from transportation source, but also from natural source and regional industrial polluted gas. The enrichment factors of Ni and Cr were low, which may result from natural source. With the elevation of house height, the concentration of Cd increased, the concentrations of Pb and Zn increased first and then decreased, while Cu showed no significant differences. Zn, Cd, Cu and Pb mainly existed in the active form, while Ni and Cr mainly existed in the residual form. The bioaccessiblity of Zn and Cd was high, while that of other heavy metals was low. The modified potential ecology risk evaluation results showed that the risk of Cd was extremely high, and contributed mainly to the potential risk index of multi-element. The Cd from the windowsill of high height showed higher potential ecological risk. The carcinogenic risk of Cr to children was higher than the threshold value, while the carcinogenic risk and non-carcinogenic risk of other metals to children and adults were all below the safety thresholds.