[Variation Analysis of Daily PM2.5 Concentrations Based on Boosted Regression Tree: A Case Study in Changzhou].

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.

[Pollution Risk of Heavy Metals in Dust from the Building Along Elevated Road: A Case Study in Changzhou].

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.

[Isolation, screening and identification of prometryne-degrading bacteria and their degrading characteristics].

The purpose of this study was to develop some bacterial strains that could degrade prometryne effectively. Bacteria were screened and purified from sediments of a pesticide plant with the method of domestication with gradient concentrations. Two strains were isolated and named P-1 and P-2, respectively. According to their morphology, physiological, biochemical properties and the analysis of their 16S rRNA gene sequences, the strain P-1 is Gram negative and identified as Ochrobactrum; the strain P-2 is Gram positive and identified as Bacillus. GenBank Accession numbers are HM004554 and HM004555, respectively. Degradation rates of the strains P-1 and P-2 for prometryne concentration with 40 mg x L(-1) were 46.5% and 65.4% after 12 days in the liquid culture experiment, respectively. This study provides an essential material and theoretical foundation for the remediation of prometryne contaminated soils.

Release of bioactive active iodine in kelp.

The release process and influencing factors of bioactive iodine of kelp are systemically studied by leaching experiment. The results showed that the bioactive iodine of kelp can be released rapidly and the principal form of iodine in lixivium is I-. There is a dynamic process between the release and absorption of iodine. With the increase of leaching water, the gross amounts of released iodine rise. There also exists a transforming process among I-, IO3- and organic iodine in lixivium.

Capacity and degree of iodine absorbed and enriched by vegetable from soil.

To understand the biogeochemical transfer of iodine, the absorbability and bioaccumulation of iodine in tested vegetables (radish, spinach and Chinese cabbage) are examined by applying iodic fertilizer composed of kelp and diatomaceous earth. The experimental results show that when iodine in soil is not excessive, the concentrations of iodine in tested vegetables increase as the content of iodine in soil increases. The absorbability and enrichment degree of iodine in various vegetables and in various parts of the same vegetable a redifferent, which explains that the concentration of iodine in plant is determined by the plant type and the physiological action of plant. The patience order of tested vegetables to excessive iodine is Chinese cabbage > spinach > radish. These results have theoretical and practical significance in opening up a new way for ameliorating poor iodine environment with artificial means.