Mercury emission trend influenced by stringent air pollutants regulation for coal-fired power plants in Korea

Regulatory control of mercury emission from anthropogenic sources has become a global concern in the recent past. Coal-fired power plants are one of the largest sources of anthropogenic mercury emission into the atmosphere. This paper summarizes the current reducing trend of mercury emission as co-beneficial effect by more stringent regulation changes to control primary air pollutants with introducing test results from the commercial coal-fired facilities and suggesting a guideline for future regulatory development in Korea. On average, mercury emission concentrations ranged 16.3–2.7 μg Sm^?3, 2.4–1.1 μg Sm^?3, 3.1–0.7 μg Sm^?3 from anthracite coal-fired power plants equipped with electrostatic precipitator (ESP), bituminous coal-fired power plants with ESP + flue gas desulphurization (FGD) and bituminous coal-fired power plants with selective catalytic reactor (SCR) + cold side (CS) ? ESP + wet FGD, respectively. Among the existing air pollution control devices, the best configuration for mercury removal in coal-fired power plants was SCR + CS ? ESP + wet FGD, which were installed due to the stringent regulation changes to control primary air pollutants emission such as SO₂, NOx and dust. It was estimated that uncontrolled and controlled mercury emission from coal-fired power plants as 10.3 ton yr^?1 and 3.2 ton yr^?1 respectively. After the installation of ESP, FGD and SCR system, following the enforcement of the stringent regulation, 7.1 ton yr^?1 of mercury emission has been reduced (nearly 69%) from coal-fired power plants as a co-benefit control. Based on the overall study, a sample guideline including emission limits were suggested which will be applied to develop a countermeasure for controlling mercury emission from coal-fired power plants.     

Physicochemical variations in atmospheric aerosols recorded at sea onboard the Atlantic–Mediterranean 2008 Scholar Ship cruise (Part I): Particle mass concentrations,size ratios,and main chemical components

We report on ambient atmospheric aerosols present at sea during the Atlantic–Mediterranean voyage of Oceanic II (The Scholar Ship) in spring 2008. A record was obtained of hourly PM₁₀, PM_2.5, and PM₁ particle size fraction concentrations and 24-h filter samples for chemical analysis which allowed for comparison between levels of crustal particles, sea spray, total carbon, and secondary inorganic aerosols. On-board monitoring was continuous from the equatorial Atlantic to the Straits of Gibraltar, across the Mediterranean to Istanbul, and back via Lisbon to the English Channel. Initially clean air in the open Atlantic registered PM₁₀ levels <10 μg m^?3 but became progressively polluted by increasingly coarse PM as the ship approached land. Away from major port cities, the main sources of atmospheric contamination identified were dust intrusions from North Africa (NAF), smoke plumes from biomass burning in sub-Saharan Africa and Russia, industrial sulphate clouds and other regional pollution sources transported from Europe, sea spray during rough seas, and plumes emanating from islands. Under dry NAF intrusions PM₁₀ daily mean levels averaged 40–60 μg m^?3 (30–40 μg m^?3 PM_2.5; c. 20 μg m^?3 PM₁), peaking briefly to >120 μg m^?3 (hourly mean) when the ship passed through curtains of higher dust concentrations amassed at the frontal edge of the dust cloud. PM₁/PM₁₀ ratios ranged from very low during desert dust intrusions (0.3–0.4) to very high during anthropogenic pollution plume events (0.8–1).     

Quantifying road dust resuspension in urban environment by Multilinear Engine: A comparison with PMF2

Atmospheric PM pollution from traffic comprises not only direct emissions but also non-exhaust emissions because resuspension of road dust that can produce high human exposure to heavy metals, metalloids, and mineral matter. A key task for establishing mitigation or preventive measures is estimating the contribution of road dust resuspension to the atmospheric PM mixture. Several source apportionment studies, applying receptor modeling at urban background sites, have shown the difficulty in identifying a road dust source separately from other mineral sources or vehicular exhausts. The Multilinear Engine (ME-2) is a computer program that can solve the Positive Matrix Factorization (PMF) problem. ME-2 uses a programming language permitting the solution to be guided toward some possible targets that can be derived from a priori knowledge of sources (chemical profile, ratios, etc.). This feature makes it especially suitable for source apportionment studies where partial knowledge of the sources is available.In the present study ME-2 was applied to data from an urban background site of Barcelona (Spain) to quantify the contribution of road dust resuspension to PM₁₀ and PM_2.5 concentrations. Given that recently the emission profile of local resuspended road dust was obtained (Amato, F., Pandolfi, M., Viana, M., Querol, X., Alastuey, A., Moreno, T., 2009. Spatial and chemical patterns of PM₁₀ in road dust deposited in urban environment. Atmospheric Environment 43 (9), 1650–1659), such a priori information was introduced in the model as auxiliary terms of the object function to be minimized by the implementation of the so-called “pulling equations”.ME-2 permitted to enhance the basic PMF solution (obtained by PMF2) identifying, beside the seven sources of PMF2, the road dust source which accounted for 6.9 μg m^?3 (17%) in PM₁₀, 2.2 μg m^?3 (8%) of PM_2.5 and 0.3 μg m^?3 (2%) of PM₁. This reveals that resuspension was responsible of the 37%, 15% and 3% of total traffic emissions respectively in PM₁₀, PM_2.5 and PM₁. Therefore the overall traffic contribution resulted in 18 μg m^?3 (46%) in PM₁₀, 14 μg m^?3 (51%) in PM_2.5 and 8 μg m^?3 (48%) in PM₁. In PMF2 this mass explained by road dust resuspension was redistributed among the rest of sources, increasing mostly the mineral, secondary nitrate and aged sea salt contributions.     

Active methods of mercury removal from flue gases

Due to its adverse impact on health, as well as its global distribution, long atmospheric lifetime and propensity for deposition in the aquatic environment and in living tissue, the US Environmental Protection Agency (US EPA) has classified mercury and its compounds as a severe air quality threat. Such widespread presence of mercury in the environment originates from both natural and anthropogenic sources. Global anthropogenic emission of mercury is evaluated at 2000 Mg year⁻¹. According to the National Centre for Emissions Management (Pol. KOBiZE) report for 2014, Polish annual mercury emissions amount to approximately 10 Mg. Over 90% of mercury emissions in Poland originate from combustion of coal.

The purpose of this paper was to understand mercury behaviour during sub-bituminous coal and lignite combustion for flue gas purification in terms of reduction of emissions by active methods. The average mercury content in Polish sub-bituminous coal and lignite was 103.7 and 443.5 μg kg⁻¹. The concentration of mercury in flue gases emitted into the atmosphere was 5.3 μg m⁻³ for sub-bituminous coal and 17.5 μg m⁻³ for lignite. The study analysed six low-cost sorbents with the average achieved efficiency of mercury removal from 30.6 to 92.9% for sub-bituminous coal and 22.8 to 80.3% for lignite combustion. Also, the effect of coke dust grain size was examined for mercury sorptive properties. The fine fraction of coke dust (CD) adsorbed within 243–277 μg Hg kg⁻¹, while the largest fraction at only 95 μg Hg kg⁻¹. The CD fraction < 0.063 mm removed almost 92% of mercury during coal combustion, so the concentration of mercury in flue gas decreased from 5.3 to 0.4 μg Hg m⁻³. The same fraction of CD had removed 93% of mercury from lignite flue gas by reducing the concentration of mercury in the flow from 17.6 to 1.2 μg Hg m⁻³. The publication also presents the impact of photochemical oxidation of mercury on the effectiveness of Hg vapour removal during combustion of lignite. After physical oxidation of Hg in the flue gas, its effectiveness has increased twofold.

     

Simulating the fine and coarse inorganic particulate matter concentrations in a polluted megacity

A three dimensional chemical transport model (PMCAMx) is applied to the Mexico City Metropolitan Area (MCMA) in order to simulate the chemical composition and mass of the major PM₁ (fine) and PM_1–10 (coarse) inorganic components and determine the effect of mineral dust on their formation. The aerosol thermodynamic model ISORROPIA-II is used to explicitly simulate the effect of Ca, Mg, and K from dust on semi-volatile partitioning and water uptake. The hybrid approach is applied to simulate the inorganic components, assuming that the smallest particles are in thermodynamic equilibrium, while describing the mass transfer to and from the larger ones. The official MCMA 2004 emissions inventory with improved dust and NaCl emissions is used. The comparison between the model predictions and measurements during a week of April of 2003 at Centro Nacional de Investigacion y Capacitacion Ambiental (CENICA) “Supersite” shows that the model reproduces reasonably well the fine mode composition and its diurnal variation. Sulfate predicted levels are relatively uniform in the area (approximately 3 μg m^?3), while ammonium nitrate peaks in Mexico City (approximately 7 μg m^?3) and its concentration rapidly decreases due to dilution and evaporation away from the urban area. In areas of high dust concentrations, the associated alkalinity is predicted to increase the concentration of nitrate, chloride and ammonium in the coarse mode by up to 2 μg m^?3 (a factor of 10), 0.4 μg m^?3, and 0.6 μg m^?3 (75%), respectively. The predicted ammonium nitrate levels inside Mexico City for this period are sensitive to the physical state (solid versus liquid) of the particles during periods with RH less than 50%.     

Source apportionment of wintertime secondary organic aerosol during the California regional PM10/PM2.5 air quality study

The UCD/CIT air quality model with the Caltech Atmospheric Chemistry Mechanism (CACM) was used to predict source contributions to secondary organic aerosol (SOA) formation in the San Joaquin Valley (SJV) from December 15, 2000 to January 7, 2001. The predicted 24-day average SOA concentration had a maximum value of 4.26 μg m^?3 50 km southwest of Fresno. Predicted SOA concentrations at Fresno, Angiola, and Bakersfield were 2.46 μg m^?3, 1.68 μg m^?3, and 2.28 μg m^?3, respectively, accounting for 6%, 37%, and 4% of the total predicted organic aerosol. The average SOA concentration across the entire SJV was 1.35 μg m^?3, which accounts for approximately 20% of the total predicted organic aerosol. Averaged over the entire SJV, the major SOA sources were solvent use (28% of SOA), catalyst gasoline engines (25% of SOA), wood smoke (16% of SOA), non-catalyst gasoline engines (13% of SOA), and other anthropogenic sources (11% of SOA). Diesel engines were predicted to only account for approximately 2% of the total SOA formation in the SJV because they emit a small amount of volatile organic compounds relative to other sources. In terms of SOA precursors within the SJV, long-chain alkanes were predicted to be the largest SOA contributor, followed by aromatic compounds. The current study identifies the major known contributors to the SOA burden during a winter pollution episode in the SJV, with further enhancements possible as additional formation pathways are discovered.     

Zinc accumulation potential and toxicity threshold determined for a metal-accumulating Populus canescens clone in a dose–response study

The effect of increasing soil Zn concentrations on growth and Zn tissue concentrations of a metal-accumulating aspen clone was examined in a dose–response study. Plants were grown in a soil with a low native Zn content which was spiked with Zn salt solutions and subsequently aged. Plant growth was not affected by NH₄NO₃-extractable soil Zn concentrations up to 60 μg Zn g^?1 soil, but it was completely inhibited at extractable concentrations above 90 μg Zn g^?1 soil. From these data an effective concentration of 68.5 μg extractable Zn g^?1 soil was calculated at which plant growth was reduced by 50%. The obtained information on toxicity threshold concentrations, and the relation between plant Zn accumulation and extractable soil Zn concentrations may be used to assess the suitability of the investigated Populus canescens clone for various phytoremediation strategies. The potential risk of metal transfer into food webs associated with P. canescens stands on Zn-polluted sites may also be estimated.     

Concentrations,seasonal variations,and transport of carbonaceous aerosols at a remote Mountainous region in western China

Carbonaceous aerosol concentrations were determined for total suspended particle samples collected from Muztagh Ata Mountain in western China from December 2003 to February 2006. Elemental carbon (EC) varied from 0.004 to 0.174 μg m^?3 (average = 0.055 μg m^?3) while organic carbon (OC) ranged from 0.12 to 2.17 μg m^?3 and carbonate carbon (CC) from below detection to 3.57 μg m^?3. Overall, EC was the least abundant fraction of carbonaceous species, and the EC concentrations approached those in some remote polar areas, possibly representing a regional background. Low EC and OC concentrations occurred in winter and spring while high CC in spring and summer was presumably due to dust from the Taklimakan desert, China. OC/EC ratios averaged 10.0, and strong correlations between OC and EC in spring–winter suggest their cycles are coupled, but lower correlations in summer–autumn suggest influences from biogenic OC emissions and secondary OC formation. Trajectory analyses indicate that air transported from outside of China brings ～0.05 μg m^?3 EC, ～0.42 μg m^?3 OC, and ～0.10 μg m^?3 CC to the site, with higher levels coming from inside China. The observed EC was within the range of loadings estimated from a glacial ice core, and implications of EC-induced warming for regional climate and glacial ice dynamics are discussed.     

Quantification of Saharan dust contribution to PM10 concentrations over Italy during 2003–2005

Italy is frequently affected by Saharan dust intrusions, which result in high PM₁₀ concentrations in the atmosphere and can cause the exceedances of the PM₁₀ daily limits (50 μg m^?3) set by the European Union (EU/2008/50). The estimate of African dust contribution to PM₁₀ concentrations is therefore a key issue in air quality assessment and policy formulation. This study presents a first identification of Saharan dust outbreaks as well as an estimate of the African dust contribution to PM₁₀ concentrations during the period 2003–2005 over Italy. The identification of dust events has been carried out by looking at different sources of information such as monitoring network observations, satellite images, ground measurements of aerosol optical properties, dust model simulations and air mass backward trajectory analysis. The contribution of Saharan dust to PM₁₀ monthly concentrations has been estimated at seven Italian locations. The results are both spatially (with station) and temporally (with month and year) variable, as a consequence of the variability of the meteorological conditions. However, excluding the contribution of severe dust events (21st February 2004, 25th–28th September 2003, 23rd–27th March 2005), the monthly contribution of dust varies approximately between 1 μg m^?3 and 10 μg m^?3 throughout year 2005 and between 1 μg m^?3 and 8 μg m^?3 throughout year 2003. In 2004 the dust concentration is lower than 2003 and 2005 (<5 μg m^?3 at all sites). The reduction in the number of daily exceedances of the limit value (50 μg m^?3) after subtraction of the dust contribution is also calculated at each station: it varies with station between 20% and 50% in 2005 and between 5% and 25% in 2003 and 2004.     

Characterization of size-fractionated particulate mercury in Shanghai ambient air

The size-fractionated particulate mercury in ambient air was collected at the top of a university campus building in Shanghai from March 2002 to September 2003. Wet digestion followed by cold vapor atom adsorption spectroscopy (CVAAS) was employed to analyze total particulate mercury concentration. Two-step extraction was performed to differentiate volatile particle-phase mercury (VPM), reactive particle-phase mercury (RPM) and inert particle-phase mercury (IPM). The average concentrations of mercury in PM_1.6, PM₈ and total suspended particle (TSP) were 0.058–0.252, 0.148–0.398 and 0.233–0.529 ng m⁻³, respectively. About 50%–60% of mercury in PM₈ was in PM_1.6, and about 60%–70% of mercury in TSP was in PM₈. Particulate mercury was mainly concentrated on fine particles. The mercury fraction in fine particulate matters (<1.6 μm) was over 4 μg g⁻¹ while 1–2 μg g⁻¹ in TSP. Both were much higher than background values, suggesting that anthropogenic sources are the predominant emission contributors. Seasonal variation indicated that the mercury in TSP in spring was higher than that in summer; however, the mercury in fine particles (<1.6 μm) varied little. The fact that fine particulate mercury (<1.6 μm) was well correlated with sulfate and elemental carbon, but not with fluoride, chloride, nitrate and organic carbon, demonstrates that fine particulate mercury is closely associated with stationary sources and gas–particle transformation. Speciation analysis of mercury showed that VPM fraction decreased with the decrease of particle size, while IPM fraction increased and occupied over 50% in particle <1.6 μm. The detailed species in VPM, RPM and IPM were discussed. Coal burning was estimated to contribute approximately 80% of total atmospheric mercury.     

Quantitative chemical composition and characteristics of aerosols over western India: One-year record of temporal variability

One-year quantitative chemical data set consisting of water-soluble constituents (NH₄⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, NO₃^?, SO₄^2? and HCO₃^?), crustal and trace elements (Al, Fe, Ca, Mg, K, Mn, Zn, Pb) and carbonaceous species (OC, EC) in ambient aerosols, collected over an urban site located in a high-dust semi-arid region of western India, reveals excellent linear relationship (r² = 0.92; slope = 0.96 ± 0.05) between gravimetrically assessed TSP (total suspended particulates) and chemically analyzed aerosol mass. The TSP abundance ranging from 60 to 250 μg m^?3, over a period of 12 months (January–December), is dominated by mineral dust (～70%); whereas contribution from sea-salts, anthropogenic and carbonaceous species exhibits significant temporal variability depending upon the wind regimes. The mineral dust is enriched in Ca, Mg and Fe with respect to upper continental crust (UCC); whereas Zn and Pb exhibit a characteristic anthropogenic source and high enrichment factors. The carbonaceous species show significant seasonality; with dominance of OC (range: 4.6–28 μg m^?3; average: 12.8 μg m^?3; SD: 6.8) and minor contribution from EC (range: 0.3–4.4 μg m^?3; average: 2.4 μg m^?3; SD: 1.4). The observed concentrations are significantly lower than those reported for the metro cities in South Asia but the OC/EC ratios (range: 4.3–35; average: 8.3; SD: 5.7) are significantly higher than the characteristic ratio (～2–4) reported for the urban atmosphere. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and climate change. This study could also be useful in understanding the physical and optical aerosol properties documented from the same site and thus, in validating regional climate models.     

Mercury in United Kingdom topsoils; concentrations, pools, and Critical Limit exceedances

The median total mercury concentration in 898 UK rural topsoils, sampled between 1998 and 2008, was 0.095 μg g⁻¹. Approximate adjustment for unreactive metal produced an estimate of 0.052 μg g⁻¹ for reactive Hg. The highest concentrations were in the north and west, where organic-rich soils with low bulk densities dominate, but the spatial pattern was quite different if soil Hg pools (mg m⁻²) were considered, the highest values being near to the industrial north of England and London. Possible toxic effects of Hg were best evaluated by comparison with soil Critical Limits expressed as ratios of Hg to soil organic matter, or soil solution Hg²⁺ concentrations, estimated by chemical speciation modelling. Only a few percent of the rural UK soils showed exceedance, and this also applied to rural soils from the whole of Europe. UK urban and industrial soils had higher Hg concentrations and more cases of exceedance.     

Effects of soil dust episodes and mixed fuel sources on source apportionment of PM10 particles in Kuopio,Finland

A receptor modeling study was carried out in Kuopio, Finland, between January and April 1994. Near the center of town, the daily mean concentrations were measured for PM10, sulphur dioxide, carbon monoxide and Black Smoke. Elemental concentrations of PM10 samples for 38 days were analyzed by ICP-MS. The main sources and their contributions to the measured concentrations of PM10 particles were solved by receptor modeling using a factor analysis-multiple linear regression (FA-MLR) model. Because a dust episode was very strong during two sampling days, the FA analysis was strongly influenced by this episode and did not give main factors. The factor analysis, when the two episode days were omitted, gave credible factors related to the sources in the study area. The four major sources and their estimated contributions to the average PM10 concentration of 27.2 μg m^-3 were: soil and street dust 46–48%, heavy fuel oil burning 12–18%, traffic exhaust 10–14%, wood burning ca. 11% and unidentified sources 15–25%. However, during spring dust episode days, with maximum PM10 concentration of 150 μg m^-3, the main source of PM10 was soil.     

A four-year size-segregated characterization study of particles PM10, PM2.5 and PM1 depending on air mass origin at Melpitz

PM₁₀ measurements were started in November 1992 at Melpitz site. The mean PM₁₀ concentration in 1993 was 38 μg m^?3 in the summer season (May until October) and about 44 μg m^?3 in the winter season (November until April). The mean PM₁₀ level decreased until 1999 and varies now in ranges from 20–34 μg m^?3 to 17–24 μg m^?3 (minimum and maximum mean values for 1999–2008) in winter and summer seasons, respectively. High volume filter samples of particles PM₁₀, PM_2.5 and PM₁ were characterized for mass, water-soluble ions, organic and elemental carbon from 2004 until 2008. The percentage of PM_2.5 in PM₁₀ varies between summer (71.6%) and winter seasons (81.9%). Mean concentrations of PM₁₀, PM_2.5 and PM₁ in Melpitz were 20, 15, and 13 μg m^?3 in 2004, 22, 18, and 13 μg m^?3 in 2005, 24, 19, and 12 μg m^?3 in 2006 and 22, 17, and 12 μg m^?3 in 2007, respectively. In the four winters the rural background concentration PM₁₀ at Melpitz exceeded the daily 50 μg m^?3 limit for Europe on 8, 8, 7 and 6 days, respectively.Findings for a simple two-sector-classification of the samples (May 2004 until April 2008) using 96-h backward trajectories for the identification of source regions are: Air masses were transported most of time (60%) from the western sector and secondly (17%) from the eastern sector. The lowest daily mean mass concentration PM₁₀ were found during western inflow in summer (17 μg m^?3) containing low amounts of sulphate (2.4 μg m^?3), nitrate (1.7 μg m^?3), ammonium (1.1 μg m^?3) and TC (3.7 μg m^?3). In opposite the highest mean mass concentration PM₁₀ was found during eastern inflow in winter (35 μg m^?3) with high amounts of sulphate (6.1 μg m^?3), nitrate (5.4 μg m^?3), ammonium (3.8 μg m^?3) and TC (9.4 μg m^?3). An estimation of secondary formed OC (SOA) shows 0.8–0.9 μg m^?3 for air masses from West and 2.1–2.2 μg m^?3 from East. The seasonal difference can be neglected.The half-hourly measurements of the particle mass concentration PM₁₀ evaluated as mean daily courses using a TEOM^® show low values (14–21 μg m^?3) in summer and winter for air masses transported from West and the highest concentrations (31–38 μg m^?3) in winter for air masses from East.The results demonstrate the influence of meteorological parameters on long-range transport, secondary particle mass formation and re-emission which modify mass concentration and composition of PM₁₀, PM_2.5 and PM₁. Melpitz site is located in the East of Germany faraway from strong local anthropogenic emissions (rural background). Therefore, this site is suitable for investigation of the influence of long-range transport of air pollution in continental air masses from the East with source regions inside and outside of the European Union.     

Chemical and strontium isotope characterization of rainwater in karst virgin forest,Southwest China

Strontium isotope ratios and concentrations of Ca²⁺, NH₄⁺, Na⁺, K⁺, Mg²⁺, Cl^?, SO₄^2?, NO₃^? and Al³⁺, Sr²⁺ were measured for 52 rainwater samples collected in virgin forest in a rural region between May 2007 and Dec. 2008. The rainwater pH values vary from 4.1 to 7.2 with a volume weight mean (VWM) value of 5.40. 40 of 52 samples have pH value above 5.0, indicating that the regional rainwater was not acidic. Among anions and cations, sulphate concentration (40.4 μeq l^?1, VWM) is the highest in the rainwater, followed by ammonium and calcium (30.2 and 20.8 μeq l^?1, VWM). Rainwater quality is characterized by low salinity and neutralized pH.The chemical compositions and ⁸⁷Sr/⁸⁶Sr ratios of the rainwater samples vary considerably. Using Na⁺ concentration as an indicator of marine origin, the proportions of sea salt and crustal elements were estimated from elemental ratios. The ⁸⁷Sr/⁸⁶Sr ratios were used to characterize different sources base on the data sets of this study and those from literatures. Such sources include weathering of limestone (⁸⁷Sr/⁸⁶Sr = 0.7075), remote soil dust (⁸⁷Sr/⁸⁶Sr > 0.7135) and anthropogenic source (fertilizers: ⁸⁷Sr/⁸⁶Sr = 0.7079). The results of the present study suggest that one likely source for high ammonium and calcium concentration is local soil. Due to a large contribution of these cations to the sulphate neutralization action, the rainwater in this region displays non-acidity, and thus has not significant environmental impact. The wet precipitation in the karst virgin forest in Guizhou province is strongly influenced by natural sources rather than anthropogenic sources.     

Source apportionment of secondary organic aerosol during a severe photochemical smog episode

The UCD/CIT air quality model was modified to predict source contributions to secondary organic aerosol (SOA) by expanding the Caltech Atmospheric Chemistry Mechanism to separately track source apportionment information through the chemical reaction system as precursor species react to form condensable products. The model was used to predict source contributions to SOA in Los Angeles from catalyst-equipped gasoline vehicles, non-catalyst equipped gasoline vehicles, diesel vehicles, combustion of high sulfur fuel, other anthropogenic sources, biogenic sources, and initial/boundary conditions during the severe photochemical smog episode that occurred on 9 September 1993. Gasoline engines (catalyst+non-catalyst equipped) were found to be the single-largest anthropogenic source of SOA averaged over the entire model domain. The region-wide 24-h average concentration of SOA produced by gasoline engines was predicted to be 0.34 μg m⁻³ with a maximum 24-h average concentration of 1.81 μg m⁻³ downwind of central Los Angeles. The region-wide 24-h average concentration of SOA produced by diesel engines was predicted to be 0.02 μg m⁻³, with a maximum 24-h average concentration of 0.12 μg m⁻³ downwind of central Los Angeles. Biogenic sources are predicted to produce a region-wide 24-h average SOA value of 0.16 μg m⁻³, with a maximum 24-h average concentration of 1.37 μg m⁻³ in the less-heavily populated regions at the northern and southern edges of the air basin (close to the biogenic emissions sources). SOA concentrations associated with anthropogenic sources were weakly diurnal, with slightly lower concentrations during the day as mixing depth increased. SOA concentrations associated with biogenic sources were strongly diurnal, with higher concentrations of aqueous biogenic SOA at night when relative humidity (RH) peaked and little biogenic SOA formation during the day when RH decreased.     

Impact of gold mining associated with mercury contamination in soil,biota sediments and tailings in Kenya

This work considered the environmental impact of artisanal mining gold activity in the Migori–Transmara area (Kenya). From artisanal gold mining, mercury is released to the environment, thus contributing to degradation of soil and water bodies. High mercury contents have been quantified in soil (140 μg kg^?1), sediment (430 μg kg^?1) and tailings (8,900 μg kg^?1), as expected. The results reveal that the mechanism for transporting mercury to the terrestrial ecosystem is associated with wet and dry depositions. Lichens and mosses, used as bioindicators of pollution, are related to the proximity to mining areas. The further the distance from mining areas, the lower the mercury levels. This study also provides risk maps to evaluate potential negative repercussions. We conclude that the Migori–Transmara region can be considered a strongly polluted area with high mercury contents. The technology used to extract gold throughout amalgamation processes causes a high degree of mercury pollution around this gold mining area. Thus, alternative gold extraction methods should be considered to reduce mercury levels that can be released to the environment.     

Polybrominated diphenyl ethers and their methoxylated and hydroxylated analogs in Brown Bullhead (Ameiurus nebulosus) plasma from Lake Ontario

Polybrominated diphenyl ethers (PBDEs), methoxylated PBDEs (MeO-PBDEs) and hydroxylated PBDEs (OH-PBDEs) were detected and quantified in Brown Bullhead (Ameiurus nebulosus) from Lake Ontario. Samples were collected in 2006 from three different locations near the city of Toronto: Frenchman’s Bay, Toronto Island, and Tommy Thompson Park. A total of 117 plasma samples were pooled into 19 samples, separating males and females by site of capture. Pooled samples were analyzed for 36 PBDEs, 20 MeO-PBDEs and 20 OH-PBDEs, but only six PBDEs, five MeO- and eight OH-compounds were confirmed against standards currently available. These peaks were quantified as “identified” peaks, while peaks matching ion ratios but not matching the retention time of the available standards were quantified as “unidentified” peaks. Both “identified” and “unidentified” concentrations were combined to obtain a total concentration. No significant variations were obtained for total PBDE concentrations, ranging from 3.33 to 9.02 ng g^?1 wet weight. However, OH- and MeO-PBDE totals ranged over 1 order of magnitude among the samples (not detected – 3.57 ng g^?1 wet weight for OH-PBDEs and not detected ?0.10 ng/g wet weight for MeO-PBDE). The results of this study suggested that these compounds are ubiquitous in biota. Source estimation of MeO- and OH-PBDEs in freshwater fish were discussed. Considering that up to date no freshwater sources for MeO- or OH-PBDEs have been reported, concentrations found should be mainly related to bioaccumulation from anthropogenic sources, although other sources could not be dismissed.     

Speciation and diurnal variation of thoracic,fine thoracic and sub-micrometer airborne particulate matter at naturally ventilated office environments

Thoracic (PM₁₀), fine thoracic (PM_2.5) and sub-micrometer (PM₁) airborne particulate matter was sampled during day and night. In total, about 100 indoor and outdoor samples were collected for each fraction at ten different office environments. Energy-dispersive X-ray fluorescence spectrometry and ion chromatography were applied for the quantification of some major and minor elements and ions in the collected aerosols. During daytime, mass concentrations were in the ranges: 11–29, 8.1–24, and 6.6–18 μg m^?3, with averages of 20 ± 1, 15.0 ± 0.9, and 11.0 ± 0.8 μg m^?3, respectively. At night, mass concentrations were found to be significantly lower for all fractions. Indoor PM₁ concentrations exceeded the corresponding outdoor levels during office hours and were thought to be elevated by office printers. Particles with diameters between 1 and 2.5 μm and 2.5 and 10 μm were mainly associated with soil dust elements and were clearly subjected to distinct periods of settling/resuspension. Indoor NO₃^? levels were found to follow specific microclimatic conditions at the office environments, while daytime levels of sub-micrometer Cl^? were possibly elevated by the use of Cl-containing cleaning products. Indoor carbon black concentrations were sometimes as high as 22 μg m^?3 and were strongly correlated with outdoor traffic conditions.     

Possible change in Asian dust source suggested by atmospheric anthropogenic radionuclides during the 2000s

Decades-long monitoring of anthropogenic radionuclides in the atmospheric deposition in Tsukuba, Japan suggests not only the substantial impacts of the Asian dust (Kosa) on the deposition but also the possible change of the Kosa source region, especially during springs of the 2000s. In order to know more about such change, 4 single wet deposition events occurred in the spring of 2007 were scrutinized. The largest anthropogenic radionuclides wet deposition was supplied by the April 2–4 event. It brought several tens % of the monthly depositions (April 2007) of the dust (residue) mass (4.5 g m^?2) and anthropogenic radionulides (⁹⁰Sr: 16, ¹³⁷Cs: 97 and Pu: 3 mBq m^?2). None of the events observed fulfilled both criteria of the specific activities and ⁹⁰Sr/¹³⁷Cs activity ratio to the Tsukuba soil; they did not exhibit local soil dust signature. The Kosa events in fact have extensive impacts on the atmospheric environment over Japan in spring season. Considering the elevated specific activities as well as greater ¹³⁷Cs/⁹⁰Sr activity ratio in the deposited dust, it is hypothesized that the dust source areas in Asian continent would be shifting from the arid zone to the desert-steppe zone suffering from desertification during the 2000s. This type of the Kosa may be called as the ‘new-regime Kosa’. Chemical observation in the far downwind region of the Kosa dust could allow us to know possible shift in the source regions.