J. J. Cao

Characterizing ionic species in PM2.5 and PM10 in four Pearl River Delta cities,South China

PM2.5 and PM10 samples were collected at four major cities in the Pearl River Delta (PRD), South China, during winter and summer in 2002. Six water-soluble ions, Na+, NH4+, K+, Cl-, NO3- and SO4(2-) were measured using ion chromatography. On average, ionic species accounted for 53.3% and 40.5% for PM2.5 and PM10, respectively in winter and 39.4% and 35.2%, respectively in summer. Secondary ions such as sulfate, nitrate and ammonium accounted for the major part of the total ionic species. Sulfate was the most abundant species followed by nitrate. Overall, a regional pollution tendency was shown that there were higher concentrations of sulfate, nitrate and ammonium in Guangzhou City than those in the other PRD cities. Significant seasonal variations were also observed with higher levels of species in winter but lower in summer. The Asian monsoon system was favorable for removal and diffusion of air pollutants in PRD in summer while highly loading of local industrial emissions tended to deteriorate the air quality as well. NO3-/SO4(2-) ratio indicated that mobile sources have considerably contribution to the urban aerosol, and stationary sources should not be neglected. Besides the primary emissions, complex atmospheric reactions under favorable weather conditions should be paid more attention for the control of primary emission in the PRD region.

PM1.0 and PM2.5 Characteristics in the Roadside Environment of Hong Kong

Daily mass concentrations of PM 1.0 (particles less than 1.0 μm in diameter), PM 2.5 (particles less than 2.5 μm in diameter), organic carbon (OC), and elemental carbon (EC) were measured from January through May 2004 at a heavily trafficked sampling site in Hong Kong (PU). The average concentrations for PM 1.0 and PM 2.5 were 35.9 ± 12.4 μ g cm − 3 and 52.3 ± 18.3 μ g cm − 3 . Carbonaceous aerosols were the dominant species in fine particles, accounting for ∼ 45.7% of PM 1.0 and ∼ 44.4% of PM 2.5 . During the study period, seven fine-particle episodes occurred, due to the influence of long-range transport of air masses from mainland China. PM 1.0 and PM 2.5 responded in similar ways; i.e., with elevated mass and OC concentrations in those episode days. During the sampling period, PM 1.0 OC and EC generally behaved similarly to the carbonaceous aerosols in PM 2.5 , regardless of seasonal variations and influence by regional pollutions. The low and relatively constant OC/EC ratios in PM 1.0 and PM 2.5 indicated that vehicular emissions were major sources of carbonaceous aerosols. PM 1.0 and PM 2.5 had the same dominant sources of vehicular emissions in winter, while in spring PM 2.5 was more influenced by PM 1 − 2.5 (particles 1–2.5 μ m in diameter) that did not form from vehicle exhausts. Therefore, PM 1.0 was a better indicator for vehicular emissions at the Roadside Station.

Carbonaceous aerosols in PM10 and pollution gases in winter in Beijing

An intensive observation of organic carbon (OC) and elemental carbon (EC) in PM10 and gaseous materials (SO2, CO, and O3) was conducted continuously to assess the characteristics of wintertime carbonaceous aerosols in an urban area of Beijing, China. Results showed that the averaged total carbon (TC) and PM10 concentrations in observation period are 30.2 +/- 120.4 and 172.6 +/- 198.3 microg/m3, respectively. Average OC concentration in nighttime (24.9 +/- 19.6 microg/m3) was 40% higher than that in daytime (17.7 +/- 10.9 microg/m3). Average EC concentrations in daytime (8.8 +/- 15.2 microg/m3) was close to that in nighttime (8.9 +/- 15.1 microg/m3). The OC/EC ratios in nighttime ranging from 2.4 to 2.7 are higher than that in daytime ranging from 1.9 to 2.0. The concentrations of OC, EC, PM10 were low with strong winds and high with weak winds. The OC and EC were well correlated with PM10, CO and SO2, which implies they have similar sources. OC and EC were not well correlated with 03. By considering variation of OC/EC ratios in daytime and night time, correlations between OC and O3, and meteorological condition, we speculated that OC and EC in Beijing PM10 were emitted as the primary particulate form. Emission of motor vehicle with low OC/EC ratio and coal combustion sources with high OC/EC ratio are probably the dominant sources for carbonaceous aerosols in Beijing in winter. A simple ratio method was used to estimate the relative contribution of sources to carbonaceous aerosols in Beijing PM10. Motor vehicle source accounts for 80% and 68%, while coal combustion accounts for 20% and 32% in daytime and nighttime, respectively in Beijing. Averagely, the motor vehicle and coal combustion accounted for 74% and 26%, respectively, for carbonaceous aerosols during the observation period. It points to the motor vehicle is dominant emission for carbonaceous aerosols in Beijing PM10 in winter period, which should be paid attention to control high level of PM10 in Beijing effectively.

Catalytic effect of Ag+ on arsenic bioleaching from orpiment (As2S3) in batch tests with Acidithiobacillus ferrooxidans and Sulfobacillus sibiricus

Orpiment is one of the major arsenic sulfide minerals which commonly occurs in the gold mine environment and the weathering of this mineral can lead to the contamination of arsenic. In this study, chemical leaching experiments using 10g/L Fe(3+) at 35°C and 50°C were carried out and the results show that orpiment can be leached by Fe(3+) and the leaching rate of orpiment was significantly enhanced in the presence of Ag(+). The bioleaching experiments with mesophilic bacteria Acidithiobacillus ferrooxidans and moderate thermophilic bacteria Sulfobacillus sibiricus were carried out, showing that these two strains can survive in the mineral pulp and oxidize Fe(2+) to regenerate Fe(3+). Based on above results, it is believed that the leaching action of the acidic mining drainage by some bacteria can lead to the release of arsenic from orpiment. Different performances of At. ferrooxidans and S. sibiricus in the tests suggest they follow two different mechanisms and this point of view is further confirmed based on analyses of the composition and morphology of the mineral residue by SEM and EDS.

The Anthropocene—A Potential Stratigraphic Definition Based on Black Carbon, Char, and Soot Records

Although the Anthropocene has been well recognized, whether or not it should be endowed the status of a new epoch or a formal unit of the geologic time scale is still debated due to the absence of a stratigraphic definition. In this paper, we review historical variations in wildfires based on the biomarkers of black carbon (BC) and its subtypes, including char and soot over the past 30 million years, to evaluate the possibility of using these as the basis for the stratigraphic definition of the Anthropocene. Wildfire and BC variations throughout the Cenozoic Era are continuously increasing and show some sharp changes in climatic boundary changes, suggesting that they might be useful in stratigraphic definitions. We also summarized glacial–interglacial variations during the Quaternary period from marine sediments, which suggests that soot with the regional and global dispersion may be a useful tool for epoch stratigraphic definitions. However, human-induced wildfires over the Holocene, based on the global charcoal combination data, present a decreasing trend in the past 2000 years, suggesting that their influence on soot emissions may be insignificant. Overwhelming changes occurred in the transition from biomass burning to fossil fuel combustion, leading to the emission of more soot. Although historical variations in soot are not globally uniform in the aftermath of the Industrial Revolution, there has been a global increase over the last hundred years. Thus, if the stratigraphic definition of the Anthropocene is not limited to a specific date, but encompasses a range of periods, soot can be utilized as part of a definition. We also suggest that soot, in conjunction with other markers, could be useful as part of the stratigraphic definition of the Anthropocene.

Column experiments for immobilization of sulfate reducing babteria

In view of the difficulty in treating the bioleaching solutions, the selective precipitation of metals using H2S produced biologically by sulfate reducing bacteria (SRB) was put forward. In this paper, two anaerobic fixed bed bioreactors fabricated from Plexiglas was used to produce hydrogen sulfide by continuous operation, porcelain rings and synthetic sponge (polyurethane foam) were used as immobilization carrier for supporting the biofilm growth. The results showed that high removal rate of SO42− were achieved with both porcelain rings and synthetic sponge as immobilization carrier for continuous treatment. And in view of the stability of process and the removal rate of SO42−, synthetic sponge was better as the immobilized carrier in the experiments, the removal rate of SO42− with it reached 92%, and the process was easily operated.