Microscopic evaluation of trace metals in cloud droplets in an acid precipitation region

The Easily Overlooked Effect of Global Warming: Diffusion of Heavy Metals

Since industrialization, global temperatures have continued to rise. Human activities have resulted in heavy metals being freed from their original, fixed locations. Because of global warming, glaciers are melting, carbon dioxide concentrations are increasing, weather patterns are shifting, and various environmental forces are at play, resulting in the movement of heavy metals and alteration of their forms. In this general context, the impact of heavy metals on ecosystems and organisms has changed accordingly. For most ecosystems, the levels of heavy metals are on the rise, and this rise can have a negative impact on the ecosystem as a whole. Numerous studies have been conducted to analyze the combined impacts of climate change and heavy metals. However, the summary of the current studies is not perfect. Therefore, this review discusses how heavy metals affect ecosystems during the process of climate change from multiple perspectives, providing some references for addressing the impact of climate warming on environmental heavy metals.

Seasonal variation of mercury in cloud water at a mountaintop in subtropical Hong Kong: Influences of transboundary transport and sea-salt aerosol

Understanding the distribution and controlling factors of mercury (Hg) speciation in cloud water is crucial for predicting the fate of atmospheric Hg and assessing the environmental impacts of Hg in cloud water. In this study, we collected 85 cloud water samples during autumn and spring at a mountaintop (957 m a.s.l.) in Hong Kong, China. The concentrations of total Hg (THg) in cloud water varied from 3.6 to 225.3 ng L-1, with volume-weighted mean values of 32.1 ng L-1 in autumn and 24.4 ng L-1 in spring. Due to the strong acidic condition of the cloud water, dissolved Hg (DHg) contributed to two-thirds of THg, with Hg complexes by dissolved organic matter (DOM) and chloride being the predominant species of DHg according to chemical equilibrium modeling simulations. Moreover, the levels of Hg-DOM were significantly higher in autumn cloud water compared to spring, and the latter contained more Hg(II)-halide complexes. These differences could be attributed to the different air mass pathways and their emission sources. By combining backward trajectories and Positive Matrix Factorization (PMF) models, we found that air masses originating from the inland Pearl River Delta region, which were only present in autumn cloud water and strongly influenced by stationary coal combustion, were responsible for the highest concentrations of THg, DHg, particulate Hg (PHg) and Hg-DOM. Additionally, air masses originating from regions in China-Indochina Peninsula were only found in spring samples and were significantly influenced by stationary coal combustion, industrial and biogenic sources, contributing to elevated proportions of methylmercury (MeHg) and PHg. In contrast, marine air masses mainly from the western Pacific Ocean contributed to high levels of Hg(II)-halide complexes, especially in spring cloud water. The dissolution and conversion of Hg from sea salt aerosols played a significant role in the enhanced DHg levels observed during cloud processing.

High fraction of soluble trace metals in fine particles under heavy haze in central China

Atmospheric trace metals are a key component of particulate matter and significantly influence the atmospheric process and human health. The dissolved fraction of trace metals represents their bioavailability and exhibits high chemical activity. However, the optimum measurement method for detecting the soluble fraction of trace metals is still undetermined. The impact of variations in pollution on the soluble fraction is largely unrevealed. Therefore, in this work, a one-month field observation was conducted in Central China and different extraction solvents were used to determine the proper measurement method for the soluble fraction of trace metals and investigate the variation pattern under different pollution conditions. The findings show that solvents with acidity near that of aerosol water can better reflect the actual soluble fraction of trace metals in fine particulate matter. The soluble fraction of trace metals tends to increase with pollution level increased, demonstrating unexpectedly high health risks and chemical activity under heavy haze conditions. Our results indicate that remediation and trace metal pollution control are urgently needed.

Dynamic Behaviors of Newly Deposited Atmospheric Heavy Metals in the Soil-Pak Choi System

Dynamic behaviors of the newly deposited atmospheric heavy metals in the soil-pak choi (Brassica chinensis L.) system are investigated by a fully factorial atmospheric exposure experiment using soils exposed to 0.5-year and 1.5-year atmospheric depositions. The results showed approximately 17-87%, 19-64%, and 43-84% of the Cu, Cd, and Pb in pak choi edible parts were contributed from the new depositions, respectively. For the newly deposited metals, foliar uptake was the key pathway of shoot bioaccumulation rather than from root uptake of the deposited metals in soils, resulting in no significant soil contribution differences between pak chois growing in 0.5-year and 1.5-year exposed soils. Indeed, highly bioavailable metals in atmospheric deposition significantly increased the soil plant-bioavailable Cu, Cd, and Pb fractions; however, soil aging resulted in similar percentages of the plant-bioavailable fractions in 0.5-year and 1.5-year exposed soils, which indicated the bioavailability of metals deposited into soils rapidly decreased with aging. The soil aging process of the deposited metals was well fitted with the first-order exponential decay model, and soil organic matter and clay were the major driving factors. Our findings highlight high plant bioaccumulation rates and the rapid soil aging process of newly deposited metals during the plant growth period.

An overlooked source of nanosized lead particles in the atmosphere: Residential honeycomb briquette combustion

Atmospheric lead (Pb) pollution has attracted long-term and widespread concerns due to its high toxicity. The definite source identification of atmospheric Pb is the key step to mitigate this pollution. Here, we first report an overlooked source of atmospheric nanosized Pb particles using transmission electron microscopy and bulk sample analyses, finding that residential honeycomb briquette combustion emits large numbers of nanosized Pb-rich particles. We found that 33.7 ± 19.9 % of primary particles by number from residential honeycomb briquette combustion contains the crystalline Pb particles. These Pb-rich particles range in size from 14 to 956 nm with a mean diameter of 117 nm. Compared with raw coal chunks, honeycomb briquette combustion could emit less carbonaceous particles, but largely increase nanosized Pb particle emissions. This result is attributed to two key factors: (1) higher Pb content in honeycomb briquette (63.6 μg g^-1) than that in coal chunk (8.5 μg g^-1), and (2) higher Pb release rate for honeycomb briquette (62.3 %) caused by honeycomb structure than that for coal chunk (20.1 %). This study highlights that atmospheric and health implications of high emissions of toxic nanosized Pb from honeycomb briquette should be paid more attention in future research on ambient and indoor airs.

Influence of strong iron-binding ligands on cloud water oxidant capacity

Iron (Fe) plays a dual role in atmospheric chemistry: it is involved in chemical and photochemical reactivity and serves as a micronutrient for microorganisms that have recently been shown to produce strong organic ligands. These ligands control the reactivity, mobility, solubility and speciation of Fe, which have a potential impact on Fe bioavailability and cloud water oxidant capacity. In this work, the concentrations of Fe-binding ligands and the conditional stability constants were experimentally measured for the first time by Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) technique in cloud water samples collected at puy de Dôme (France). The conditional stability constants, which indicate the strength of the Fe-ligand complexes, are higher than those considered until now in cloud chemistry (mainly Fe-oxalate). To understand the effect of Fe complexation on cloud water reactivity, we used the CLEPS cloud chemistry model. According to the model results, we found that Fe complexation impacts the hydroxyl radical formation rate: contrary to our expectations, Fe complexation by natural organic ligands led to an increase in hydroxyl radical production. These findings have important impacts on cloud chemistry and the global iron cycle.

Unveiling the pH-Dependent Yields of H2O2 and OH by Aqueous-Phase Ozonolysis of m-Cresol in the Atmosphere

Hydrogen peroxide (H₂O₂) and hydroxyl radical (OH) are important oxidants in the atmospheric aqueous phase such as cloud droplets and deliquescent aerosol particles, playing a significant role in the chemical transformation of organic and inorganic pollutants in the atmosphere. Atmospheric aqueous-phase chemistry has been considered to be a source of H₂O₂ and OH. However, our understanding of the mechanisms of their formation in atmospheric waters is still incomplete. Here, we show that the aqueous-phase reaction of dissolved ozone (O₃) with substituted phenols such as m-cresol represents an important source of H₂O₂ and OH exhibiting pH-dependent yields. Intriguingly, the formation of H₂O₂ through the ring-opening mechanism is strongly promoted under lower pH conditions (pH 2.5-3.5), while higher pH favors the ring-retaining pathways yielding OH. The rate constant of the reaction of O₃ with m-cresol increases with increasing pH. The reaction products formed during the ozonolysis of m-cresol are analyzed by an Orbitrap mass spectrometer, and reaction pathways are suggested based on the identified product compounds. This study indicates that aqueous-phase ozonolysis of phenolic compounds might be an alternative source of H₂O₂ and OH in the cloud, rain, and liquid water of aerosol particles; thus, it should be considered in future model studies.

Transport route-based cluster analysis of chemical fingerprints and source origins of marine fine particles (PM2.5) in South China Sea

The fingerprints and source origins of marine PM_2.5 at two background islands in the South China Sea were clustered via trajectory analysis and positive matrix factorization. High PM_2.5 concentrations at the Dongsha Islands occurred for the north routes, while Nansha Islands had similar PM_2.5 concentrations amongst the transport routes. However, the chemical characteristics of PM_2.5 varied with the transport routes. Secondary inorganic aerosols (NO₃^-, SO₄^2-, and NH₄⁺) were abundant in water-soluble ions which dominated PM_2.5. Crustal metals were the abundant metals in PM_2.5, while trace metals were primarily originated from man-made sources. Organic carbon was superior to elemental carbon, and high concentrations of levoglucosan and organic acids were observed for the north routes. Overall, marine PM_2.5 at the Dongsha Islands was highly influenced by long-range transport of Asian continental outflows, while particulate air quality at the Nansha Islands was mainly governed by clean air parcels blown from the SCS.

Insights into the source-specific health risk of ambient particle-bound metals in the Pearl River Delta region, China

Quantification of source-specific health risks of PM2.5 plays an essential role in health-oriented air pollution control. However, there is limited evidence supporting the source-based risk apportionment of particle-bound metals. In this study, source-specific cancer and non-cancer risk characterization of 12 particle-bound metals was performed in the Pearl River Delta (PRD) region, China. A combination of health risk assessment model and receptor-based source apportionment modeling with positive matrix factorization (PMF) was applied for characterizing the spatial-temporal patterns for inhalation health risks of particle-bound metals in three main city clusters, inland area and coastal area in the region from December 2014 through July 2016. Results showed that the carcinogenic risk of particle-bound metals for adults (4.13 × 10-5) was higher than that for children (9.53 × 10-6) in the PRD region. The highest and significant non-carcinogenic risk was found in the northwest city cluster. Industrial emission (63.3%) were the dominant contributors to the cancer risk, while the main contributors to the non-cancer risk were the vehicle emission source (33.2%) in the dry season and industrial emission (30.8%) in the wet season. Our results provide important evidence for spatial source-specific health risks with temporal characteristics of particle-bound metals in most densely populated areas in the southern China, and suggest that reduction of industrial and vehicle emissions could facilitate more cost-effective PM2.5 control measures to improve human health.

Chemical speciation of trace metals in atmospheric deposition and impacts on soil geochemistry and vegetable bioaccumulation near a large copper smelter in China

Atmospheric deposition is an important source of trace metals to surface environments, but knowledge about plant bioavailability of recently deposited metals and their fate in the soil-plant system is limited. We performed a fully factorial soil and atmosphere exposure experiment with three vegetables (radish, lettuce, and soybean). Treatments included soil profiles collected from three sites located along a strong gradient of atmospheric deposition with each soil type deployed across the three sites for one year, which allowed to effectively distinguish impacts of recently deposited metals (<1 year) from longer-term trace metal exposures in soils. Results showed that recently deposited copper (Cu), cadmium (Cd), and lead (Pb) accounted for 0.5-15.2% of total soil Cu, Cd, and Pb pools at the site most heavily impacted by atmospheric deposition, while recent deposition contributed 15-76% of Cu, Cd, and Pb concentrations in edible parts of vegetables. In addition, soil geochemical extractions showed that bioavailable fractions of trace metals from recent deposition (52-73%) were higher compared to metals previously present in soils (7-42%). These findings highlight a preferential uptake and high rates of bioaccumulation of deposited metals in vegetables and suggest a high potential of environmental risks of food pollution under high atmospheric metal deposition.

Photochemistry of the Cloud Aqueous Phase: A Review

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H₂O₂, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO^• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate.

Study of the bioavailability of heavy metals from atmospheric deposition on the soil-pakchoi (Brassica chinensis L.) system

The objective of this study was to investigate the bioavailability of heavy metals from atmospheric deposition on the soil-pakchoi (Brassica chinensis L.) system near a smelter. Soil reciprocal translocation experiment was conducted with seven groups of pot culture (filled with soils of gradient levels of heavy metals) in three sites of gradient atmospheric heavy metal depositions. Results showed that the newly deposited heavy metals (Cu and Cd) were preferential retention in topsoil (0-4 cm) and presented as higher bioavailable fractions compared to those in original soils. Atmospheric depositions contributed to 20-85% of shoot Cu and Cd in high deposition site, which were likely resulted not only from the direct transfer of contaminants from atmosphere to foliar but also from the atmosphere-soil-root transfer. However, the 52-62% of Pb in shoot from atmospheric depositions was mainly resulted from foliar direct uptake. The increasing atmospheric heavy metal depositions significantly decreased the photosynthetic parameters of pakchoi. Additionally, the potential health risks associated with the consumption of pakchoi were elevated in high deposition site and the bioaccessibility values were observed up to 56-81%. This study will provide useful reference information for the newly deposited heavy metal dynamics in the surface environment.

Magnetic, geochemical characterization and health risk assessment of road dust in Xuanwei and Fuyuan, China

As an accumulation of solid organic and inorganic pollutant particles on outdoor ground surfaces, road dust is an important carrier of heavy metal contaminants and can be a valuable medium for characterizing urban environmental quality. Because the dusts can be an important source of atmospheric particles and take impact on human health, the aim of this study described in detail the mineralogical characteristics, morphology, and heavy metal content of road dust from Xuanwei and Fuyuan, locations with high lung cancer incidence. Our results show that the average concentrations of heavy metals in road dust were higher than their background values. Higher concentrations of heavy metals were found in the magnetic fractions (MFs) than in the non-magnetic fractions (NMFs). Magnetic measurements revealed high magnetic susceptibility values in the road dust samples, and the dominant magnetic carrier was magnetite. The magnetic grains were predominantly pseudo-single domain, multi-domain, and coarse-grained stable single domains (coarse SSD) in size. SEM/XRD analysis identified two groups of magnetic particles: spherules and angular/aggregate particles. Hazard index (HI) values for adults exposure to road dust samples, including MF, Bulk, and NMF, in both areas were lower or close to safe levels, while HI values for childhood exposure to magnetic fractions in both areas were very close or higher than safe levels. Cancer risks from road dust exposure in both areas were in the acceptable value range.

An observational study of nitrous acid (HONO) in Shanghai, China: The aerosol impact on HONO formation during the haze episodes

Continuous HONO measurement was conducted to study the formation features of HONO during the haze episodes at Shanghai, China. The HONO concentration ranged from 0.26 to 5.84ppb and averaged at 2.31ppb during the measurement period. The HONO concentration during the haze episode (P1), the haze-fog episode (P2) and the clean period (P3) were 2.80, 2.35 and 1.78ppb, respectively. Heterogeneous conversion of NO₂ was the dominate pathway for nocturnal HONO formation, and the heterogeneous conversion efficiency of NO₂ to HONO was closely associated with the PM_2.5 concentration. The averaged heterogeneous conversion rate of NO₂-to-HONO (C_HONO) during the pollution periods (P1+P2) was 1.58×10^-2h^-1, higher than that during the clean period (P3) (0.93×10^-2h^-1), suggesting the higher conversion potential of NO₂ to HONO during the pollution episodes. The daytime unknown HONO production rate (P_unknown) in the pollution period was 2.98ppb/h, higher than 1.78ppb/h in the clean period. Further, aerosol played a role in P_unknown during the transformation of the clean period to the pollution period. At a single particle scale, transmission electron microscopy (TEM) images revealed that most of the particles during P1 and P2 were agglomerated, whereas the particles collected from P3 were uniformly distributed and showed simple morphologies. The number percentage of the S/N-bearing particles during P1 (34%) and P2 (27%) were higher than that during P3 (20%). In addition, particles contained more internally mixed nitrates during P1 and P2 than those during P3, suggesting more intense heterogeneous conversion of NO₂ to HONO on particle surfaces during the pollution episodes. In the present study, the averaged HONO/NO_x ratio (5.60%), especially during P1 (7.80%) and P2 (7.50%) was much higher than that assumed global averaged value of 2.0%, suggesting a potentially important role for the HONO chemistry in Shanghai. This study provides new insights into the HONO formation mechanism in the atmosphere characterized by high fine particle level.

Air pollution-aerosol interactions produce more bioavailable iron for ocean ecosystems

It has long been hypothesized that acids formed from anthropogenic pollutants and natural emissions dissolve iron (Fe) in airborne particles, enhancing the supply of bioavailable Fe to the oceans. However, field observations have yet to provide indisputable evidence to confirm this hypothesis. Single-particle chemical analysis for hundreds of individual atmospheric particles collected over the East China Sea shows that Fe-rich particles from coal combustion and steel industries were coated with thick layers of sulfate after 1 to 2 days of atmospheric residence. The Fe in aged particles was present as a "hotspot" of (insoluble) iron oxides and throughout the acidic sulfate coating in the form of (soluble) Fe sulfate, which increases with degree of aging (thickness of coating). This provides the "smoking gun" for acid iron dissolution, because iron sulfate was not detected in the freshly emitted particles and there is no other source or mechanism of iron sulfate formation in the atmosphere.

Quantitative assessment of metal elements using moss species as biomonitors in downwind area of lead-zinc mine

Distributions of a total of 21 elements were monitored in significantly lead-zinc polluted area using moss species (Hypnum cupressiforme and Camptothecium lutescens) used interchangeably, covering a denser sampling network. Interspecies comparison was conducted using Box-Cox transformed values, due to their skewed distribution. The median concentrations of trace elements in the both mosses examined decreased in the following order: Fe>Mn>Zn>Pb>Cu>Ni∼Cr∼As>Co>Cd>Hg. For almost all analyzed elements, H. cupressiforme revealed higher bio-accumulative abilities. For arsenic contents was obtained ER-value in favor of C. lutescens. The ER for the element contents according to the distance from the pollution source in selected areas was significantly enriched for the anthropogenic introduced elements As, Cd, Cu, Pb and Zn. After Box-Cox transformation of the content values, T_B was significantly different for As (4.82), Cd (3.84), Cu (2.95), Pb (4.38), and Zn (4.23). Multivariate factor analysis singled out four elemental associations: F1 (Al-Co-Cr-Fe-Li-Ni-V), F2 (Cd-Pb-Zn), F3 (Ca-Mg-Na-P) and F4 (Cu) with a total variance of 89%. Spatial distribution visualized the hazardously higher contents of "hot spots" of Cd > 1.30 mg/kg, Cu > 22 mg/kg, Pb > 130 mg/kg and Zn > 160 mg/kg. Therefore, main approach in moss biomonitoring should be based on data management of the element distribution by reducing the effect of extreme values (considering Box-Cox data transformation); the interspecies variation in sampling media does not deviate in relation to H. cupressiforme vs. C. lutescens.

Physiochemical characteristics of aerosol particles in the typical microenvironment of hospital in Shanghai, China

Health risk of populations dwelling in the hospital has been a global concern, but has not been adequately examined. PM_2.5 and PM₁ samples were collected in two indoor locations (outpatient department and inpatient department) and one outdoor location (courtyard) of the hospital in Shanghai. The concentrations of size-fractionated trace metals and the morphology of single particles were determined to accurately assess the health risk for populations in the hospital. The results indicated that the mean concentrations of PM_2.5 and PM₁ were in the order of outpatient department>courtyard>inpatient department. The mean concentrations of PM₁ decreased with floors (first floor: 78.0μg/m³, second floor: 64.1μg/m³, fourth floor: 48.4μg/m³). However, the mean PM_2.5 concentrations were in the order of first floor (124.0μg/m³)>fourth floor (91.4μg/m³)>second floor (90.6μg/m³), which was likely associated with the number of patients. The PM_2.5 and PM₁ concentrations have begun to increase rapidly from 9:00am and decreased after 15:00pm in the first floor, whereas they remain relatively stable in the second and fourth floor. The abundance of Mg, Ca, Al and K in the fine particles and coarse particles were both higher than other elements for all floors. The concentrations of trace metals (e.g., Zn, Ba, Fe, Mn, Cr, Ca, Ti, Na, and K) except Mg and Al in the coarse particles (>2.5μm) decreased with floors, whereas Zn, Ba, Fe, and Cr in the fine particles (<2.5μm) displayed opposite variation. Trace metals in the first floor were mainly concentrated in the >2.5μm and 1-2.5μm, whereas they chiefly peaked at 0.25-0.5μm and below 0.25μm in the second and fourth floor. Single particles analysis showed that mineral particles, soot, and Fe-rich particles were mainly concentrated in the first floor, indicating the impacts of walking of patients, traffic emissions, and food cooking, respectively. Sulfate particles were internally mixed with soot, fly ash and Fe-rich particles in the second floor, which suggested that these sulfate particles probably underwent aging processes during the atmospheric long-range transport. In the fourth floor, fly ash, sulfate particles, Zn-rich particles, and biogenic particles were identified under the transmission electron microscopy (TEM). Higher abundance of sulfates and absence of chlorate hinted existence of heterogeneous reactions during long-range transport with the Cl^- replaced by SO₄^2-. The index of average daily intake (ADI), hazard quotient (HQ), and carcinogenic risks (CR) indicated that Cr pose carcinogenic risks to the surrounding populations, while non-carcinogenic risks of Mn, Zn, and Cr were not remarkable.

Multivariate extraction of dominant geochemical markers for deposition of 69 elements in the Bregalnica River basin, Republic of Macedonia (moss biomonitoring)

Atmospheric deposition was investigated using the terrestrial moss species Hypnum cupressiforme (Hedw.) and Homolothecium lutescens (Hedw.) in the Bregalnica River basin, Republic of Macedonia. Long-term emission occurs in this area due to the hydrothermal exploitation of Pb-Zn deposits (Sasa and Zletovo mines) and copper ore exploitation and floatation (Bučim mine). Determination of the chemical elements was conducted using atomic emission spectrometry with inductively coupled plasma (ICP-AES) and mass spectrometry with inductively coupled plasma (ICP-MS). A combination of multivariate techniques (PCA, FA and CA) was applied for data processing and identification of element association with lithogenic/anthropogenic origin. Seven dominant factors were extracted from the total of 69 analysed elements. Spatial distribution maps were constructed for the determination and localisation of smaller areas with higher contents of certain anthropogenic elements. In this way, the influences of selected human activities on local air pollution can be determined. The summarised data show quantification of the element distributions. This not only allows the determination of the distribution of hazardous elements but also presents complete characterisation of element deposition in the environs of mines.

Geogenic and Anthropogenic Moss Responsiveness to Element Distribution Around a Pb-Zn Mine, Toranica, Republic of Macedonia

Moss species (Homalothecium lutescens, Hypnum cupressiforme, Brachythecium glareosum, and Campthotecium lutescens) were used as suitable sampling media for biomonitoring the origin of heavy-metal pollution in the lead-zinc (Pb-Zn) mine "Toranica" near the Kriva Palanka town, Eastern Macedonia. The contents of 20 elements-silver (Ag), aluminum (Al), arsenic (As), barium (Ba), calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), Pb, strontium (Sr), vanadium (V), and (Zn) were determined by atomic emission spectrometry with inductively coupled plasma. Data processing was applied with combinations of multivariate statistical methods: factor analysis, principal component analysis, and cluster analysis. Moss' responsiveness to the atmospheric distribution of the selected elements was investigated in correlation to the specific geology of the region (soil dusting). Lithogenic distribution was characterized with the distribution of three dominant geochemical associations: F1: Al-Li-V-Cr-Ni-Co, F2: Ba-Ca-Sr, and F3: Cd-Zn-Pb-Cu. Spatial distribution was constructed for visualization of the factor deposition. Furthermore, air distribution (passive biomonitoring) versus soil geochemistry of the analyzed elements was examined. Significant correlations were singled out for Pb, Zn, and Cd and for Mg(moss)/Na(soil). Characteristic lithological anomaly characterized the presence of the oldest geological volcanic rocks. Zone 1 (Pb-Zn mine surrounding) presents a unique area with hydrothermal action of Pb-Zn mineralization leading to polymetallic enrichments in soil. This phenomenon strongly affects the environment, which is a natural geochemical imprint in this unique area (described with the strong dominance of the geochemical association Cd-Zn-Pb-Cu).

Characterization of carbonaceous aerosols at Mount Lu in South China: implication for secondary organic carbon formation and long-range transport

In order to understand the sources and potential formation processes of atmospheric carbonaceous aerosols in South China, fine particle samples were collected at a high-elevation mountain site--Mount Lu (29°35' N, 115°59' E, 1165 m A.S.L.) during August-September, 2011. Eight carbonaceous fractions from particles were resolved following the IMPROVE thermal/optical reflectance protocol. During the observation campaign, the daily concentrations of PM2.5 at Mount Lu ranged from 7.69 to 116.39 μg/m(3), with an average of 58.76 μg/m(3). The observed average organic carbon (OC) and elemental carbon (EC) concentrations in PM2.5 were 3.78 and 1.28 μg/m(3), respectively. Secondary organic carbon (SOC) concentration, estimated by EC-tracer method, was 2.07 μg/m(3) on average, accounting for 45.0% of the total OC. The enhancement of secondary organic aerosol (SOA) formation was observed during cloud/fog processing, and heterogeneous acid-catalyzed reactions may have contributed to SOA formation as well. Back trajectory analysis indicated that air masses were mainly sourced from southern China during observation period, and this air mass source was featured by highest values of OC and effective carbon ratio (ECR). Relation of carbonaceous species and principal component analysis indicated that multiple sources contributed to the carbonaceous aerosols at Mount Lu.

Identification of the typical metal particles among haze, fog, and clear episodes in the Beijing atmosphere

For a better understanding of metal particle morphology and behaviors in China, atmospheric aerosols were sampled in the summer of 2012 in Beijing. The single-particle analysis shows various metal-bearing speciations, dominated by oxides, sulfates and nitrates. A large fraction of particles is soluble. Sources of Fe-bearing particles are mainly steel industries and oil fuel combustion, whereas Zn- and Pb-bearing particles are primarily contributed by waste incineration, besides industrial combustion. Other trace metal particles play a minor rule, and may come from diverse origins. Mineral dust and anthropogenic source like vehicles and construction activities are of less importance to metal-rich particles. Statistics of 1173 analyzed particles show that Fe-rich particles (48.5%) dominate the metal particles, followed by Zn-rich particles (34.9%) and Pb-rich particles (15.6%). Compared with the abundances among clear, haze and fog conditions, a severe metal pollution is identified in haze and fog episodes. Particle composition and elemental correlation suggest that the haze episodes are affected by the biomass burning in the southern regions, and the fog episodes by the local emission with manifold particle speciation. Our results show the heterogeneous reaction accelerated in the fog and haze episodes indicated by more zinc nitrate or zinc sulfate instead of zinc oxide or carbonate. Such information is useful in improving our knowledge of fine airborne metal particles on their morphology, speciation, and solubility, all of which will help the government introduce certain control to alleviate metal pollution.

Trace metals in atmospheric fine particles in one industrial urban city: spatial variations, sources, and health implications

Trace metals in PM2.5 were measured at one industrial site and one urban site during September, 2010 in Ji'nan, eastern China. Individual aerosol particles and PM2.5 samples were collected concurrently at both sites. Mass concentrations of eleven trace metals (i.e., Al, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, and Pb) and one metalloid (i.e., As) were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The result shows that mass concentrations of PM2.5 (130 microg/m3) and trace metals (4.03 microg/m3) at the industrial site were 1.3 times and 1.7 times higher than those at the urban site, respectively, indicating that industrial activities nearby the city can emit trace metals into the surrounding atmosphere. Fe concentrations were the highest among all the measured trace metals at both sites, with concentrations of 1.04 microg/m 3 at the urban site and 2.41 microg/m3 at the industrial site, respectively. In addition, Pb showed the highest enrichment factors at both sites, suggesting the emissions from anthropogenic activities existed around the city. Correlation coefficient analysis and principal component analysis revealed that Cu, Fe, Mn, Pb, and Zn were originated from vehicular traffic and industrial emissions at both sites; As, Cr, and part of Pb from coal-fired power plant; Ba and Ti from natural soil. Based on the transmission electron microscopy analysis, we found that most of the trace metals were internally mixed with secondary sulfate/organic particles. These internally mixed trace metals in the urban air may have different toxic abilities compared with externally mixed trace metals.

Microscopic observation of metal-containing particles from Chinese continental outflow observed from a non-industrial site

Atmospheric metal-containing particles adversely affect human health because of their physiological toxicity. Mixing state, size, phase, aspect ratio, and sphericity of individual metal-containing particles collected in Hong Kong air in winter are examined through transmission electron microscopy (TEM). Eighteen percent of the sulfate particles have one or more tiny metal inclusions. Size distributions of metal and fly ash particles (or inclusions) with diameters from 15 nm to 2.7 μm show the same peak at 210 nm. The major metal particles were classified as Fe-rich (e.g., hematite), Zn-rich (e.g., zinc sulfate and zinc oxide), Pb-rich (e.g., anglesite), Mn-rich, and As-rich, which were likely emitted from industries and coal-fired power plants at high temperatures in mainland China. Compared to fly ash and S-rich particles, metal particles display a lower sphericity of 0.51 and a higher aspect ratio of 1.47, which means their shapes are poorly defined. The elemental mapping of individual particles reveal that sulfate areas without metal inclusions also contain minor Fe, Mn, or Zn. Therefore, the internal mixing of metals and acidic constituents likely solubilize metals and modify metal inclusion shapes. Solubilization of metals in airborne particles can extend their toxicity into nontoxicity parts in the particles. The structure of the metal-containing particles may provide important information for assessing health effects of fine sulfate and nitrate particles with metal inclusions in urban areas.