Risks related to heavy metal pollution in urban construction dust fall of fast-developing Chinese cities.

Urban construction is a major contributor to air pollution, but few studies have examined heavy metal pollution in urban areas caused by construction dust fall. We measured the concentrations of Cr, Ni, Cu, Zn, Pb, Cd, and Hg and particle size distribution in dust fall from various construction activities in seven fast-developing cities in China and conducted a health risk assessment. Mean metal concentrations in construction dust fall were on the order of Zn (246.3 mg/kg) > Cr (94.2 mg/kg) > Pb (56.5 mg/kg) > Cu (53.6 mg/kg) > Ni (22.8 mg/kg) > Cd (0.68 mg/kg) > Hg (0.08 mg/kg). Cu and Zn were positively correlated in areas of subway and building construction, and Pb and Cd were positively correlated in areas of road construction, likely because of the materials specific to these activities. Enrichment factors for heavy metals at all sampling sites were on the order of Cd (10.4) > Zn (6.37) > Cu (4.25) > Pb (3.84) > Hg (2.41) > Cr (2.02) > Ni (1.32). The enrichment factors for all metals except Zn indicated that heavy metal pollution was highest in road construction, followed by building and subway construction. Non-carcinogenic risks to children (hazard index >1) were 1.01-1.08 in four of the seven sampling sites, indicating possible risk from deposition of construction dust fall. In contrast, the hazard index for adults was <1 at the seven cities and total carcinogenic risks (<1 × 10-6) were at acceptable levels. An integrated ecological risk assessment demonstrated that heavy metal particles in construction dust fall in two of the cities (Shijiazhuang and Qingdao) were likely to be suspended in the atmosphere. Our study of heavy metal pollution in construction dust fall provides data on ecological and human health impacts and suggests that extensive measures are required to control construction dust fall in China.

Occurrence of arsenic in brown rice and its relationship to soil properties from Hainan Island, China.

The acquaintance of arsenic concentrations in rice grain is vital in risk assessment. In this study, we determined the concentration of arsenic in 282 brown rice grains sampled from Hainan Island, China, and discussed its possible relationships to the considered soil properties. Arsenic concentrations in the rice grain from Hainan Island varied from 5 to 309 µg/kg, with a mean (92 µg/kg) lower than most published data from other countries/regions and the maximum contaminant level (MCL) for As(i) in rice. The result of correlation analysis between grain and soil properties showed that grain As concentrations correlated significantly to soil arsenic speciation, organic matter and soil P contents and could be best predicted by humic acid bound and Fe-Mn oxides bound As fractions. Grain arsenic rises steeply at soil As concentrations lower than 3.6 mg/kg and gently at higher concentrations.

[On-line method for measurement of the carbon isotope ratio of atmospheric methane and its application to atmosphere of Yakela condensed gas field].

An on-line method for measurement of the 13C/12C ratio of methane by a gas chromatography/high-temperature conversion/ isotope ratio mass spectrometry (GC/C/MS) technique was developed. This method is less laborious, more rapid (45 min), of high precision (+/- 0.4 x 10(-3)) and by using a small amount of sample (about 200 mL of atmosphere). Its application to isotopic characterization, and hence methane source identification, was demonstrated by examination of atmosphere sample collected in Yakela condensed gas field, China. The average 13C/12C ratio of atmospheric methane in Yakela field was -45.0 x 10(-3) heavier by 1.2 x 10(-3) -2.0 x 10(-3) than the global average. This is caused by seepage and diffusing of methane from Yakela condensed gas reservoir. The concentrations of atmospheric methane in daytimes are found to be lower than those in nighttimes, and the corresponding 13C/12C ratios in daytimes are lighter compared to those in nighttimes, a phenomena probably caused by the fact that a small part of methane from Yakela condensate reservoir is consumed in soil's surface under sunlight.