Guoshun Zhuang

Mixing of Asian dust with pollution aerosol and the transformation of aerosol components during the dust storm over China in spring 2007

NO3 and NH4 decreased owing to the dilution of the local pollution by the invaded dust. The western dust contained relatively low anthropogenic aerosols, and it mainly derived from the Taklimakan Desert, a paleomarine source. The northwestern dust had a considerable chemical reactivity and mixing with sulfur precursors emitted from the coal mines on the pathway of the long‐range transport of dust. The northeastern dust reached Shanghai with high acidity, and it became the mixed aerosol with the interaction among dust, local pollutants, and sea salts. Comparison of the speciation of the water‐soluble ions on both nondust and dust days at all sites illustrated the evolution of major ion species from different dust sources during the long‐range transport of dust. The mixing mechanisms of the dust with the pollution aerosol on the local, medium‐range, and long‐range scale revealed from this study would improve the understanding of the impacts of Asian dust on the regional/global climate change.

Evidence for High Molecular Weight Nitrogen-Containing Organic Salts in Urban Aerosols

High molecular weight (M(w)) species were observed at substantial intensities in the positive-ion mass spectra in urban Shanghai aerosols collected from a single-particle time-of-flight mass spectrometer (in the m/z range 250-500) during three separate periods over 2007-2009. These species correlate well with the CN(-) mass signal, suggesting that C-N bonds are prevalent and that the observed high-M(w) species are potentially nitrogen-containing organic salts. Anti-correlation with the ambient O(3) concentration suggests that photochemical oxidants are not involved directly in the formation of these species. The Mannich reaction, among amines (or ammonia), formaldehyde, and carbonyls with an adjacent, acidic proton, is proposed as a plausible pathway leading to these organic salts. Although the high-M(w) species observed in the single-particle mass spectra appear to be nitrogen-containing organics, further chemical confirmation is desired to verify if the proposed Mannich reaction can explain the formation of these high-M(w) species in regions where ammonia, amines, and carbonyls are prevalent.

Characteristics and sources of 2002 super dust storm in Beijing

On 20 March, 2002, a super dust storm attacked Beijing, which was stronger than any dust storm ever recorded. The concentration of total suspended particulates (TSP) reached 10.9 mg · m−3, 54 times as high as the national air quality standard. The concentrations of major crustal elements, such as Ca, Al, Fe, Na, Mg and Ti, were 30–58 times higher than those in non-dust storm days. The concentrations of pollution elements, such as Zn, Cu, Pb, As, Cd and S, were also about several or even nearly ten times higher than those in normal days. The enrichment factors of Pb, As, Cd and S in PM2.5 were as high as 12.7, 29.6, 43.5, 28.4, indicating that these pollutants came from the mixing of mineral aerosol with pollution aerosol emitted by pollution sources on the way of dust storm’s long-range transport. The overlap of invaded air mass from dust with pollution air mass from Beijing local area was another reason for the enhancement of pollutants. During dust storm, fine particles (PM2.5) accounted for 30% of TSP and pollutants in PM2.5 accounted for even as high as 45%–69% of TSP. The increase of pollutants after dust storm proved further that mineral aerosol, especially the fine particles from dust storm favored the transformation and accumulation of pollutants. It must be noted that Fe (II) was detected again in this dust storm, which provided new evidence for the mechanism of coupling and feedback between iron and sulfur in the atmosphere and the ocean. The increase of both pollutants and nutrient, Fe(II), during dust storm illuminated that dust storm is an important factor affecting the global environment change.

Iron(II) in rainwater, snow, and surface seawater from a coastal environment

Abstract Using a newly developed HPLC method for the determination of Fe(II) concentration in a variety of aqueous environmental samples we found that Fe(II) accounts for 50–74% of the total filterable Fe in coastal surface seawater, 25–53% in rain samples, and 25–74% in snow collected from the vicinity of Massachusetts Bay, and Boston Harbor. We also found the residence time of Fe(II) in natural seawater to follow pseudo-first-order kinetics with an apparent half-life on the order of 30–70 min, much longer than previously thought. The observation of high Fe(II) concentrations and long apparent half-life reflect the product of as yet undefined chemical processes occurring in either atmosphere and/or seawater environments. These significant concentrations of Fe(II) may represent an important source of Fe influencing phytoplankton growth in coastal seawater.

Excellent photocatalytic degradation activities of ordered mesoporous anatase TiO2-SiO2 nanocomposites to various organic contaminants.

Ordered 2-D hexagonal mesoporous TiO(2)-SiO(2) nanocomposites consisted of anatase TiO(2) nanocrystals and amorphous SiO(2) nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO(2)-20SiO(2)-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of SiOH groups and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from TiOH groups, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO(2)-10SiO(2)-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO(2)-SiO(2) nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants.

The implication of carbonaceous aerosol to the formation of haze: Revealed from the characteristics and sources of OC/EC over a mega-city in China

The characteristics and sources of organic carbon (OC) and elemental carbon (EC) in PM(2.5) in 2006-2007 as well as their impact on the formation of heavy haze in Shanghai were investigated. Daily average concentrations of OC and EC ranged from 1.8 to 20.1 μg m(-3) and 0.5-7.8 μg m(-3) with averages of 7.2 and 2.8 μg m(-3), respectively. The carbonaceous aerosol (OC plus EC) contributed to ∼ 27.2% of the total mass of PM(2.5) on annual average. Obvious seasonal variation was observed in both OC and EC. The percentage of secondary organic carbon (SOC) contributed to OC was in a range of 2.4-66.8%, with an average of 40.1%. Three types of haze were classified based on their chemical composition. OC, EC, SO(2)/NO(2) (in turn, SO(4)(2-)/NO(3)(-)) were responsible for the formation of the three types of haze, respectively. The carbonaceous aerosol was one of the key factors in the formation of haze. Local emissions were the dominant sources of OC and EC in warm seasons, and long-range transport had a significant contribution to OC and EC in PM(2.5) in spring and winter in Shanghai.

Risk-based prioritization among air pollution control strategies in the Yangtze River Delta, China.

Background The Yangtze River Delta (YRD) in China is a densely populated region with recent dramatic increases in energy consumption and atmospheric emissions. Objectives We studied how different emission sectors influence population exposures and the corresponding health risks, to inform air pollution control strategy design. Methods We applied the Community Multiscale Air Quality (CMAQ) Modeling System to model the marginal contribution to baseline concentrations from different sectors. We focused on nitrogen oxide (NOx) control while considering other pollutants that affect fine particulate matter [aerodynamic diameter ≤ 2.5 μm (PM2.5)] and ozone concentrations. We developed concentration–response (C-R) functions for PM2.5 and ozone mortality for China to evaluate the anticipated health benefits. Results In the YRD, health benefits per ton of emission reductions varied significantly across pollutants, with reductions of primary PM2.5 from the industry sector and mobile sources showing the greatest benefits of 0.1 fewer deaths per year per ton of emission reduction. Combining estimates of health benefits per ton with potential emission reductions, the greatest mortality reduction of 12,000 fewer deaths per year [95% confidence interval (CI), 1,200–24,000] was associated with controlling primary PM2.5 emissions from the industry sector and reducing sulfur dioxide (SO2) from the power sector, respectively. Benefits were lower for reducing NOx emissions given lower consequent reductions in the formation of secondary PM2.5 (compared with SO2) and increases in ozone concentrations that would result in the YRD. Conclusions Although uncertainties related to C-R functions are significant, the estimated health benefits of emission reductions in the YRD are substantial, especially for sectors and pollutants with both higher health benefits per unit emission reductions and large potential for emission reductions.

Coupling and feedback between iron and sulphur in air-sea exchange

Iron in surface seawater has been demonstrated to be the limiting nutrient factor for primary productivity in certain oceanic regions. In 1992 we reported inNature at first Fe(II) existence in marine aerosols over the remote Pacific and Atlantic and proposed the hypothesis of coupling and feedback between iron and sulfur in air-sea exchange. We recently detected a considerable amount of Fe(II) in the aerosols collected during dust storm in Beijing. The concentration of Fe(II) in the dust storm was as high as 1.8–4.3 g · m−3 that accounted for 1.4% –2.6% of the total Fe mass concentration in aerosols, while Fe(II) in the aerosols collected from non-dust storm days was 0.7% of the total Fe. Fe and S concentrations in the dust storm aerosol samples represent a very positive correlationship. The size distribution of Fe, Fe(II), and S in either dust storm particles or the normal aerosols showed the same peak at 1–3 μm. The oxidation of S(IV) under natural light and UV in addition of Fe(III) was 6.5 and 14 times faster respectively compared with that of non-addition. The photoreduction of Fe(□) to Fe(II), through the formation of an OH radical, associated with the oxidation of S(IV) to S(VI) could account for ∼3%–20% of the formation of non-sea salt sulfate aerosols at Midway, central Pacific. These results further support the Fe-S coupling hypothesis. From consideration of both the marine biological production of dimethylsulphide (DMS) and the subsequent oxidation of reduced forms of sulfur in the atmosphere, the iron and sulphur cycles in both the atmosphere and the ocean may be closely coupled.

Mixing of dust with pollution on the transport path of Asian dust — Revealed from the aerosol over Yulin, the north edge of Loess Plateau

Both PM(2.5) and TSP were monitored in the spring from 2006 to 2008 in an intensive ground monitoring network of five sites (Tazhong, Yulin, Duolun, Beijing, and Shanghai) along the pathway of Asian dust storm across China to investigate the mixing of dust with pollution on the pathway of the long-range transport of Asian dust. Mineral was found to be the most loading component of aerosols both in dust event days and non-dust days. The concentrations of those pollution elements, As, Cd, Pb, Zn, and S in aerosol were much higher than their mean abundances in the crust even in dust event days. The high concentration of SO(4)(2-) could be from both sources: one from the transformation of the local emitted SO(2) and the other from the sulfate that existed in primary dust, which was transported to Yulin. Na(+), Ca(2+), and Mg(2+) were mainly from the crustal source, while NO(3)(-) and NH(4)(+) were from the local pollution sources. The mixing of dust with pollution aerosol over Yulin in dust event day was found to be ubiquitous, and the mixing extent could be expressed by the ratio of NO(3)(-)/Al in dust aerosol. The ratio of Ca/Al was used as a tracer to study the dust source. The comparison of the ratios of Ca/Al together with back trajectory analysis indicated that the sources of the dust aerosol that invaded Yulin could be from the northwestern desert in China and Mongolia Gobi.

Local and non-local sources of airborne particulate pollution at Beijing

A new element tracer technique has firstly been established to estimate the contributions of mineral aerosols from both inside and outside Beijing. The ratio of Mg/Al in aerosol is a feasible element tracer to distinguish between the sources of inside and outside Beijing. Mineral aerosol, inorganic pollution aerosol mainly as sulfate and nitrate, and organic aerosol are the major components of airborne particulates in Beijing, of which mineral aerosol accounted for 32%―67% of total suspended particles (TSP), 10%―70% of fine particles (PM 2.5 ), and as high as 74% and 90% of TSP and PM 2.5 , respectively, in dust storm. The sources from outside Beijing contributed 62% (38%―86%) of the total mineral aerosols in TSP, 69% (52%―90%) in PM 10 , and 76% (59%―93%) in PM 2.5 in spring, and 69% (52%―83%), 79% (52%―93%), and 45% (7%―79%) in TSP, PM 10 , and PM 2.5 , respectively, in winter, while only ~20% in summer and autumn. The sources from outside Beijing contributed as high as 97% during dust storm and were the dominant source of airborne particulates in Beijing. The contributions from outside Beijing in spring and winter are higher than those in summer, indicating clearly that it was related to the various meteorological factors.