The Pollution Character Analysis and Risk Assessment for Metals in Dust and PM_(10) around Road from China

INTRODUCTION In recent years, with the gradual improvement of road construction, the rapid increase of the number of motor vehicles, vehicle emissions and the current poor vehicle performance, poor vehicle maintenance, higher emission factor and so on, air pollution caused by the traffic issues becomes the focus of people attention. The harmful substances are gradually accumulated to atmosphere particles surrounding roads due to dust particles （soil dusts, road dusts, construction dusts）, coal emissions, industrial emissions, vehicle emissions, biomass burning, secondary particles, which has a certain harmful influence to the atmosphere, soil and plants surrounding roads.

Thermodynamic analysis of metal dusting on iron in CO-H_2-H_2O atmosphere

This paper provides a calculation method for carbon activity in CO-H2-H2O atmosphere. The thermodynamic parameters （aC）gas （carbon activity in environment） of different compositions at any temperature can be obtained by △G^oT. A theoretical analysis has been conducted into the thermodynamic role of iron and the dependence of possible metal-dusting occurrence on temperature, gas composition and total pressure. In CO-H2-H2O gas mixtures, decreasing the molar fraction of H2O and increasing total pressure expands the temperature region for metal dusting. In CO-H2-H2O gas mixture of different compositions at any temperature and pressure for Fe, depending on relative values of （aC）gas, （aC）Fe3C/Fe and aC= 1, three zones were found to exist.

A Eulerian population balance/Monte Carlo approach for simulating laminar aluminum dust flames

Recently,metal powders have been conceptualized as carbon-free recyclable energy carriers that may form a cornerstone of a sustainable energy economy.The combustion of metal dusts in oxidizing atmospheres is exothermal and yields oxide particles that could,potentially,be retrieved and,subsequently,recharged by conversion to pure metals using green primary energy sources.As a step towards a predictive tool for designing metal dust combustors,we present a fully Eulerian modelling approach for laminar particle-laden reactive flows that is,conceptually,based on a population balance description of the dispersed particles and relies on a stochastic Eulerian solution strategy.While the population balance equation(PBE)is formulated for the number-weighted distribution of characteristic properties among all particles near a spatial location,it is kinetically informed by the rates at which mass,momentum and heat are exchanged between the carrier gas and the particulate phase on the single particle level.Within the scope of the Eulerian Monte Carlo solution scheme,the property distribution is discretely represented in terms of the total number density and a finite number of property samples and the computational work is channelled towards the Eulerian estimation of mean particle properties.For the case of reactive aluminum particles,we combine a kinetic description of the gas-particle heat and mass transfer with a transport-limited continuum formulation to obtain rate expressions that are valid across the entire particle size range from the free molecular through the continuum regime.Besides velocity,the particle properties include only the particle mass,temperature and oxide mass fraction.This set of thermochemical degrees of freedom is retained also as phase transitions due to melting occur,drawing on a smooth blend of the solid and liquid thermodynamic and material properties.The particle-level formulation encompasses aluminum evaporation,surface oxidation,scavenging of oxide smoke,oxide evaporation/dissociation and radiation.After investigating how these effects translate,through the PBE,to the particle population level and affect the combustion in a homogeneous dust reactor,we analyze the combustion of an aluminum dust in a counterflow flame and validate predictions of the particles’centerline velocity profile and the flame speed by comparison with available experimental data.Concomitantly,nitrogen oxide emissions are investigated along with the particle burnout and outlet size distribution.

PM_(2.5), PM_(10) and health risk assessment of heavy metals in a typical printed circuit noards manufacturing workshop

A typical Printed Circuit Board（PCB） manufacturer was chosen as the object of this study.During PCB processing, fine particulate matter and heavy metals（Cu, Zn, Pb, Cr, Cd and Ni）will be released into the air and dust, which then impact workers＇ health and the environment. The concentrations of total suspended particle（TSP）, PM10 and PM2.5in the off-site were 106.3, 90.0 and 50.2 μg/m3, respectively, while the concentrations of TSP, PM10 and PM2.5in the workshops ranged from 36.1 to 365.3, from 27.1 to 289.8 and from 22.1 to212.3 μg/m3, respectively. Almost all six of the heavy metals were detected in all of the particle samples except Cd. For each workshop, it was obvious that Zn was the most enriched metal in TSP, followed by Cu 〉 Pb（Cr） 〉 Ni 〉 Cd, and the same trend was found for PM10 and PM2.5. In the dust samples, Cu（which ranged from 4.02 to 56.31 mg/g） was the most enriched metal, followed by Zn, Cr, Pb, Ni and Cd, and the corresponding concentrations ranged from 0.77 to 4.47, 0.37 to 1.59, 0.26 to 0.84, 0.13 to 0.44 and nd to0.078 mg/g, respectively. The health risk assessment showed that noncancerous effects are unlikely for Zn, Pb, Cr, Cu, Cd and Ni. The carcinogenic risks for Cd and Ni were all lower than 10-6, except for Cr. This result indicates that carcinogenic risks for workers are relatively possible in the workshops. These findings suggest that this technology is advanced from the perspective of environmental protection in the waste PCB＇s recycling industry.

Multi-Source Characteristics of Atmospheric Deposition in Nanjing,China,as Controlled by East Asia Monsoons and Urban Activities

Atmospheric deposition, a major pathway of metals entering into soils, plays an important role in soil environment, especially in urban regions where a large amount of pollutants are emitted into atmosphere through various sources. In order to understand the characteristics of atmospheric deposition in urban area and its relation with natural and anthropogenic sources, a three-year study of atmospheric deposition at three typical sites, industrial zone(IN), urban residential area(RZ) and suburban forested scenic area(FA),was carried out in Nanjing, a metropolitan city in eastern China from 2005 to 2007. The bulk deposition rate and element composition of atmospheric deposition varied spatio-temporally in the urban zones of Nanjing. The concentrations of Cu, Zn, Pb and Ca in the atmospheric deposits were strongly enriched in the whole Nanjing region; however, anthropogenic pollutants in atmospheric deposits were diluted by the input of external mineral dust transported from northwestern China. Source apportionment through principal component analysis(PCA) showed that the background atmospheric deposition at the FA site was the combination of external aerosol and local emission sources. The input of long-range transported Asian dust had an important influence on the urban background deposition, especially in spring when the continental dust from the northwestern China prevailed. Marine aerosol source was observed in summer and autumn, the seasons dominated by summer monsoon in Nanjing. In contrast, the contribution of local anthropogenic emission source was constant regardless of seasons. At the RZ and IN sites, the atmospheric deposition was more significantly affected by the nearby human activities than at the FA site. In addition, different urban activities and both the winter and summer Asian monsoons had substantial impacts on the characteristics of dust deposition in urban Nanjing.