[Spatial Distribution, Contamination Assessment, and Sources of Heavy Metals in the Urban Green Space Soils of a City in North China].

To study the condition of urban green space soils in the central parts of a city in North China, the spatial distribution, sources, and pollution levels of heavy metals (Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni) within green space soils in the central urban districts of the city were investigated. The results showed that the soil quality was high overall. The mean concentrations of Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni were 0.172, 0.202, 9.02, 34.7, 57.0, 31.2, 85.7, and 26.3 mg·kg-1, respectively. The mean concentrations of Cd, Hg, Pb, and Zn in urban soils exceeded the background value of the Beijing-Tianjin-Tangshan region. All of the samples' heavy metal concentrations were lower than the risk screening values for soil contamination of development land in the national soil environment quality standards. With respect to the spatial distribution, the concentrations of As, Cr, and Ni were higher in the northwest of the study area, the concentrations of Cd and Zn were higher in the northeast, and the concentrations of Hg, Pb, and Cu were higher in the urban core area. As for the different land use types of the soils, the concentrations of Cd, Zn, and Ni were higher in the enterprise soils, while the concentrations of Hg, Pb, and Cu were higher in park and residential soils. Assessments of soil quality showed that 97.2% of soil samples' Nemerow integrated indices were less than 1, indicating that the soils were clean. Indices of potential ecological risk for all soil samples were less than 80, indicating that they posed a slight ecological risk. Multivariate statistical analysis (correlation and principle component analyses) showed that Cu, Pb, and Hg may originate from an anthropogenic source via the painting of ancient buildings and pesticides used to protect ancient trees. Chromium may originate from natural sources via geochemical activity and soil parent material; Cr, Zn, Ni, and As were derived from mixed sources through human and geochemical activities. The receptor model was used for identification and apportionment of pollution sources of elements over the standard. The contribution rates of sources were as follows:source 2(46.1%), source 3(33.1%), source 1(17.7%), and others (3.1%) for Cd, source 1(93.0%) for Cu, source 1(52.4%), source 3(24.2%), source 2(20.0%), and others (3.4%) for Zn, source 1(56.3%), source 2(37.8%), and source 3(5.8%) for Ni. Sources 1 and 3 were anthropogenic, while source 2 was natural.

[Emission Characteristics of Residential Coal Combustion Flue Gas in Beijing].

Honeycomb briquet,biomass briquettes and bituminous coal from suburb of Beijing were chosen as testing samples to carry out combustion experiments. The characteristics of inorganic pollutant emission factors and VOCs emission factors released from the flue gas were studied. The results showed that under the condition of sufficient combustion, the average emission factors of SO2 from these three types of coal respectively were 1.50,1.91,1.62 kg·t-1;NOx 0.420,0.901,2.20 kg·t-1;CO 22.4,37.3,87.3 kg·t-1. Combustion emission factors of gaseous pollutants for NOx and CO were in the order of bituminous coal > biomass briquettes > honeycomb briquet. SO2 emission factors were in the order of biomass briquettes > bituminous coal > honeycomb briquet. The 2014 emissions inventory of the three civil coal combustion pollutants in Beijing was obtained. Bituminous coal emissions of SO2 was more than 5.5×103 tons,NOx was more than 7.5×103 tons,CO was more than 290×103 tons. All these coal types released more kinds and higher concentrations of volatile organic compounds in ignition phase and damp down stage. VOCs emission factor was the highest during ignition phase, followed by damp down phase.

[Testing of Concentration and Characteristics of Particulate Matters Emitted from Stationary Combustion Sources in Beijing].

A self-built monitoring sampling system on particulate matters and water soluble ions emitted from stationary combustion sources and a size separated sampling system on particulate matters based on FPS4000 and ELPI + were applied to test particulate matters in fumes of typical stationary combustion sources in Beijing. The results showed that the maximum concentration of total particulate matters in fumes of stationary combustion sources in Beijing was 83.68 mg · m⁻³ in standard smoke oxygen content and the minimum was 0.12 mg · m⁻³. And particle number concentration was in the 104-106 cm⁻³ number of grade. Both mass and number concentration ranking order of particulate matters emitted from stationary combustion sources in Beijing was: heating gas fired boilers < power plant coal fired boilers < heating coal fired boilers. And two or three peaks existed under 1 µm of particulate size for both number size distribution and mass size distribution. The number concentration for PM2.5 accounted for over 99.8% of that for PM10 and that for PM0.1 accounted for over 83% of that for PM2.5. But the proportions of PM0.1, and PM2.5 in PM10 were significantly lower in quality analysis,the proportion of PM2.5 in PM10 was about 82%, and that of PM0.1 in PM2.5 was about 27%-33%.

[Correlation, seasonal and temporal variation of water-soluble ions of PM2.5 in Beijing during 2012-2013].

A total of 486 daily PM2.5 samples were collected at a background site, 3 urban sites, 4 suburban sites and a boundary transfer site during August 2012-July 2013. Mass concentrations of 9 water-soluble ions were obtained. The average mass concentration of the 9 ions was 60.5 µg x m(-3), and the order of concentration of ions was NO3- > SO4(2-) > NH4(+)- > Cl- > Na+ > K+ > Ca2+ > F- > Mg2+; Secondary inorganic species NO3-, SO4(2-) and NH4+ were the major components of water-soluble ions in PM2.5, with a contribution of 88% to the total ions of PM2.5. NO3- was the most fluctuated anion during the sampling period. With the increase of pollution level, the accumulation of SNA was obvious, the components that contained nitrogen, NO3- and NH4+, occupied the dominant position in the formation of the secondary components. NO3- had a relatively higher contribution to the accumulation of heavy pollution.