Primary Anthropogenic Emissions Research Articles

Legacy impacts of all‐time anthropogenic emissions on the global mercury cycle

Elevated mercury (Hg) in marine and terrestrial ecosystems is a global health concern because of the formation of toxic methylmercury. Humans have emitted Hg to the atmosphere for millennia, and this Hg has deposited and accumulated into ecosystems globally. Here we present a global biogeochemical model with fully coupled atmospheric, terrestrial, and oceanic Hg reservoirs to better understand human influence on Hg cycling and timescales for responses. We drive the model with a historical inventory of anthropogenic emissions from 2000 BC to present. Results show that anthropogenic perturbations introduced to surface reservoirs (atmosphere, ocean, or terrestrial) accumulate and persist in the subsurface ocean for decades to centuries. The simulated present‐day atmosphere is enriched by a factor of 2.6 relative to 1840 levels, consistent with sediment archives, and by a factor of 7.5 relative to natural levels (2000 BC). Legacy anthropogenic Hg re‐emitted from surface reservoirs accounts for 60% of present‐day atmospheric deposition, compared to 27% from primary anthropogenic emissions, and 13% from natural sources. We find that only 17% of the present‐day Hg in the surface ocean is natural and that half of its anthropogenic enrichment originates from pre‐1950 emissions. Although Asia is presently the dominant contributor to primary anthropogenic emissions, only 17% of the surface ocean reservoir is of Asian anthropogenic origin, as compared to 30% of North American and European origin. The accumulated burden of legacy anthropogenic Hg means that future deposition will increase even if primary anthropogenic emissions are held constant. Aggressive global Hg emission reductions will be necessary just to maintain oceanic Hg concentrations at present levels.

Mercury as a Global Pollutant: Sources, Pathways, and Effects

Mercury (Hg) is a global pollutant that affects human and ecosystem health. We synthesize understanding of sources, atmosphere-land-ocean Hg dynamics and health effects, and consider the implications of Hg-control policies. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments. Transfers of Hg emissions to largely unavailable reservoirs occur over the time scale of centuries, and are primarily mediated through atmospheric exchanges of wet/dry deposition and evasion from vegetation, soil organic matter and ocean surfaces. A key link between inorganic Hg inputs and exposure of humans and wildlife is the net production of methylmercury, which occurs mainly in reducing zones in freshwater, terrestrial, and coastal environments, and the subsurface ocean. Elevated human exposure to methylmercury primarily results from consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin but health effects of highly exposed populations and wildlife are also a concern. Integration of Hg science with national and international policy efforts is needed to target efforts and evaluate efficacy.

Identification of marine and continental aerosol sources in Paris using high resolution aerosol mass spectrometry

Major summertime aerosol emission sources in Paris were assessed using a high resolution time‐of‐flight aerosol mass spectrometer (HR‐ToF‐AMS). The application of positive matrix factorization (PMF) to the highly mass and time‐resolved AMS measurements allowed the identification of primary and secondary sources of organic (OA) and sulfate aerosols. Primary anthropogenic emissions contributed on average ~27% (14.7% cooking, 12% traffic) to the total organic mass, while the major contribution to the organic fraction was associated with secondary formation products. Low‐volatility oxygenated OA (LV‐OOA, 25.2%) and semi‐volatile oxygenated OA (SV‐OOA, 32.4%) factors were classified as SOA. An additional component with high S : C and O : C ratios was identified and attributed to marine emissions (marine organic aerosol, MOA), owing to its high correlation with methanesulfonic acid (R2 = 0.84) and contributing on average 15.7% to the total OA mass, even in the continental megacity of Paris. Non‐sea salt sulfate was apportioned by including both organic and sulfate ions in the PMF data matrix. This allowed apportionment of submicron sulfate to continental versus marine sources. A detailed source apportionment of PM1 combining AMS, aethalometer, and filter data is presented.

Future trends in environmental mercury concentrations: implications for prevention strategies

In their new paper, Bellanger and coauthors show substantial economic impacts to the EU from neurocognitive impairment associated with methylmercury (MeHg) exposures. The main source of MeHg exposure is seafood consumption, including many marine species harvested from the global oceans. Fish, birds and other wildlife are also susceptible to the impacts of MeHg and already exceed toxicological thresholds in vulnerable regions like the Arctic. Most future emissions scenarios project a growth or stabilization of anthropogenic mercury releases relative to present-day levels. At these emissions levels, inputs of mercury to ecosystems are expected to increase substantially in the future, in part due to growth in the legacy reservoirs of mercury in oceanic and terrestrial ecosystems. Seawater mercury concentration trajectories in areas such as the North Pacific Ocean that supply large quantities of marine fish to the global seafood market are projected to increase by more than 50% by 2050. Fish mercury levels and subsequent human and biological exposures are likely to also increase because production of MeHg in ocean ecosystems is driven by the supply of available inorganic mercury, among other factors. Analyses that only consider changes in primary anthropogenic emissions are likely to underestimate the severity of future deposition and concentration increases associated with growth in mercury reservoirs in the land and ocean. We therefore recommend that future policy analyses consider the fully coupled interactions among short and long-lived reservoirs of mercury in the atmosphere, ocean, and terrestrial ecosystems. Aggressive anthropogenic emission reductions are needed to reduce MeHg exposures and associated health impacts on humans and wildlife and protect the integrity of one of the last wild-food sources globally. In the near-term, public health advice on safe fish consumption choices such as smaller species, younger fish, and harvests from relatively unpolluted ecosystems is needed to minimize exposure risks.

Substance Flow Analysis of Mercury Affecting Water Quality in the European Union

Knowledge concerning the main flows of priority substances (PSs) and the production systems and consumption structures in the society causing these flows is a prerequisite for any attempt to predict and understand their environmental fate as well as to efficiently minimize future environmental burdens. In this paper, a simple SFA diagram on mercury, including the main European Union (EU-27) source categories, flows and environmental endpoints which in turn affect the mercury concentrations in the EU-27 waters are illustrated. From trend analysis and future projections, it becomes obvious that emissions of mercury as a trace contaminant in fuels and minerals (primary anthropogenic emission sources) are becoming increasingly important to the environmental concentrations compared to emissions from mercury used intentionally (secondary anthropogenic sources). Additional future control strategies should therefore be targeted industrial sources and safe treatment of mercury-containing wastes, wastewater effluents, as well as residues collected from various combustion processes. It was found that knowledge on flows and emission sources on a large geographical scale is limited due to a lack of information on emission factors from various industrial processes and waste systems, especially for the mercury being discharges to water and land.

Primary anthropogenic aerosol emission trends for China, 1990–2005

Abstract. An inventory of anthropogenic primary aerosol emissions in China was developed for 1990–2005 using a technology-based approach. Taking into account changes in the technology penetration within industry sectors and improvements in emission controls driven by stricter emission standards, a dynamic methodology was derived and implemented to estimate inter-annual emission factors. Emission factors of PM2.5 decreased by 7%–69% from 1990 to 2005 in different industry sectors of China, and emission factors of TSP decreased by 18%–80% as well, with the measures of controlling PM emissions implemented. As a result, emissions of PM2.5 and TSP in 2005 were 11.0 Tg and 29.7 Tg, respectively, less than what they would have been without the adoption of these measures. Emissions of PM2.5, PM10 and TSP presented similar trends: they increased in the first six years of 1990s and decreased until 2000, then increased again in the following years. Emissions of TSP peaked (35.5 Tg) in 1996, while the peak of PM10 (18.8 Tg) and PM2.5 (12.7 Tg) emissions occurred in 2005. Although various emission trends were identified across sectors, the cement industry and biofuel combustion in the residential sector were consistently the largest sources of PM2.5 emissions, accounting for 53%–62% of emissions over the study period. The non-metallic mineral product industry, including the cement, lime and brick industries, accounted for 54%–63% of national TSP emissions. There were no significant trends of BC and OC emissions until 2000, but the increase after 2000 brought the peaks of BC (1.51 Tg) and OC (3.19 Tg) emissions in 2005. Although significant improvements in the estimation of primary aerosols are presented here, there still exist large uncertainties. More accurate and detailed activity information and emission factors based on local tests are essential to further improve emission estimates, this especially being so for the brick and coke industries, as well as for coal-burning stoves and biofuel usage in the residential sector.

Characterization of aerosol sources at urban and background sites in Lithuania

Size and composition real-time measurements of atmospheric submicron aerosol (PM1) were conducted in the Lithuanian background and urban areas during several months (April–July, 2008) using the Quadrupole aerosol mass spectrometer (QAMS). The average mass concentration of non-refractory PM1 ranged within 8–13 μgm−3. Organic compounds of PM1 were the most abundant constituent ranging from 70 to 83%, nitrate made up 4.0–7.7%, ammonium 1.7–3.9%, sulfate 11–21%, and chloride less than 1%. While sulfate concentrations were comparable at the urban and background sites, concentrations of organic compounds and nitrate in Vilnius city were almost twice as high as those at the background site (Rūgsteliskis). The average aerodynamic diameter for nitrate and organics was about 300 nm at both sampling sites – in Vilnius city and at Rūgsteliskis background site. The average aerodynamic diameter for ammonium was about 355 nm and for sulfate about 400 nm. The main source of organics and nitrates in the city was emission from traffic, however the main source of sulfates at urban and background sites was long-range transport. Positive matrix factorization (PMF) analysis of the unit mass-resolution (UMR) spectra was used to identify sources of organic matter in the urban (Vilnius) and background (Rūgsteliskis) aerosol. Organic aerosol components were identified from AMS spectra for both sites: primary anthropogenic emissions – hydrocarbonlike organic aerosol (HOA), aged oxygenated low volatility organic aerosol (LV-OOA), and less oxygenated, presumably, semivolatile organic aerosol (SV-OOA) at the urban site (Vilnius city) as well as biomass burning organic aerosol (BBOA), aged oxygenated low volatility organic aerosol (LV-OOA), and semivolatile biogenic secondary organic aerosol (SV-OOA) at the background site (Rūgsteliskis). Keywords: atmospheric submicron aerosol, urban and background sites, concentration, composition, size distribution, sources

Assessment of the sources of the inorganic fraction of aerosol in a conurbation

Two intensive sampling campaigns for coarse (PM2.5–10) and fine (PM2.5) particulate matter were carried out in August 2003 and March 2004 in the multi-impacted centre of the Athens (Greece) conurbation. Receptor modelling by means of Positive Matrix Factorization was utilised in order to provide an insight to the poorly characterised sources of the chemically analysed inorganic fraction of the sampled aerosol mass. Using elemental concentrations, seven factors have been resolved for both fractions for August 2003. Combining elemental and ionic concentrations, nine factors were resolved in the coarse particulate matter and eight in the fine particulate matter for March 2004. The greatest contributors of primary origin are (re)suspended dust/soil and sea salt. Secondary aerosol contributions were resolved in the form of secondary sulphate, secondary nitrate as well as an aged sea salt factor which was characterised by the replacement of chloride with sulphate and, secondarily, nitrate. Furthermore, throughout sites and fractions, primary anthropogenic emissions were identified in a series of factors, including a Pb-rich profile, representing non-catalytic exhaust emissions, a Cu-Mo-Sb-rich profile representing brake emissions, a Zn-Ba-rich profile representing tyre-wear and heavy vehicle brakes, and, lastly, a V-Ni-rich factor representing industrial heavy oil-combustion. Local anthropogenic emissions predominated, outweighing long-range transport as it was suggested by the lack of direct relationship between changes in the wind speed and direction and species mass burdens, as well as factor contributions.

Measurements of VOCs by proton transfer reaction mass spectrometry at a rural Ontario site: Sources and correlation to aerosol composition

Proton transfer reaction mass spectrometry (PTR‐MS) volatile organic compound (VOC) measurements were made at the Centre for Atmospheric Research Experiments at Egbert, Ontario, over a five week period in May to June 2007. VOCs were also analyzed by gas chromatography and with a fluorescence detector sensitive to formaldehyde. This is a well positioned site for contrasting biogenic versus anthropogenic sources. In particular, with southerly flow from Southern Ontario, the VOC signal was observed to have strong anthropogenic influence, as seen through high levels of aromatics, acetylene and NOx. With flow from the northwest, the VOCs had substantial biogenic character, with elevated mixing ratios of monoterpenes, isoprene, and possibly 2‐methyl‐3‐buten‐2‐ol (MBO) with increasing temperatures. Positive matrix factorization (PMF) was applied to the PTR‐MS data set yielding two noninstrumental factors, one related to primary anthropogenic emissions and one arising from secondary atmospheric oxidation. There is a tight correspondence between the composition of the submicron organic aerosol and the VOCs. In particular, (1) organic aerosol loadings highly correlate with long‐lived VOC tracers such as acetone, (2) the degree of oxygenation of the organic aerosol scaled with the photochemical age of the air, as determined through the toluene‐to‐benzene ratio, and (3) there is a tight correlation between PMF factors from the AMS and PTR‐MS data sets, with the HOA AMS factor scaling with the anthropogenic emissions PTR‐MS factor and the OOA AMS factor matched to the photochemical oxidation PTR‐MS factor. Finally, the PTR‐MS PMF factors were used for VOC source apportionment.

Ion chemistry and source identification of coarse and fine aerosols in an urban area of eastern central India

Abstract This work focuses on size segregated atmospheric aerosol mass concentrations and water soluble inorganic components in Chhattisgarh, the eastern central India. Investigation on the monitoring of ambient air levels of atmospheric particulates were done around a large source of primary anthropogenic particulate emissions: the industrial area and coal based power plants. Chemical characterization was carried out for aerosol samples collected in urban area, Raipur, (21°14′N, 81°38′E) of Chhattisgarh region over a period of one year, using cascade impactor. Annual mean of mass concentration for coarse (PM 2.5–10 ) and fine (PM 2.5 ) aerosols were monitored to be 238.1 ± 89.9 and 167.0 ± 75.3 µg m − 3 respectively This work deals with the seasonal variation and meteorological influences of inorganic components of the aerosols viz. NO 3 − , Cl − and SO 4 2− , Mg 2+ , Na + , K + , Ca 2+ and NH 4 + . The annual mean concentration of the inorganic components were monitored to be 3.8 ± 2.5, 8.9 ± 2.7, 10.2 ± 1.5, 2.6 ± 0.6, 8.7 ± 7.2, 4.6 ± 1.8, 16.4 ± 6.9 and 0.4 ± 0.5 µg m − 3 respectively in coarse particles and 8.2 ± 7.1, 6.8 ± 3.6, 46.5 ± 32.8, 1.7 ± 0.6, 7.4 ± 3.6, 5.9 ± 3.4, 10.2 ± 2.9, and 8.8 ± 7.7 µg m − 3 respectively in fine particles, for the above ions. The average distribution of nitrate and sulphate in PM 2.5–10 were found to be 1.6 and 4.2% and in PM 2.5 were 4.9 and 27.9% respectively indicating the dominance of sulphate in both PM 2.5–10 and PM 2.5 particles. Here, industrial emission plays important role for contribution of PM 2.5 particle loading in the atmosphere. The cation–anion rational analysis indicated that the PM 2.5–10 particles were mostly neutralized and PM 2.5 particle were acidic. The major ions were mainly in the form of NaCl > CaSO 4 > K 2 SO 4 > MgSO 4 > KCl > NH 4 Cl > Ca(NO 3 ) 2 > KNO 3 > MgCl 2 > Mg(NO 3 ) 2 > NH 4 NO 3 > (NH 4 ) 2 SO 4 in coarse aerosol particles and (NH 4 ) 2 SO 4 > K 2 SO 4 > CaSO 4 > NaCl > NH 4 NO 3 > CaCl 2 > KNO 3 > MgCl 2 > Ca(NO 3 ) 2 > KCl > NH 4 Cl in fine particles.

Source Identification of Reactive Hydrocarbons and Oxygenated VOCs in the Summertime in Beijing

It is important to identify the sources of reactive volatile organic compounds (VOCs) in Beijing for effective ground-level ozone abatement. In this paper, semihourly measurements of hydrocarbons and oxygenated VOCs (OVOCs) were taken at an urban site in Beijing in August2005. C2-C5 alkenes, isoprene, and C1-C3 aldehydes were determined as "key reactive species" by their OH loss rates. Principal component analysis (PCA) was used to define the major sources of reactive species and to classify the dominant air mass types at the sampling site. Vehicle exhaust was the largest contributor to reactive alkenes. More aged air masses with enriched OVOCs traveled mainly from the east or southeast of Beijing. The OVOC sources were estimated by a least-squares fit approach and included primary emissions, secondary sources, and background. Approximately half of the C1-C3 aldehydes were attributed to secondary sources, while regional background accounted for 21-23% of the mixing ratios of aldehydes. Primary anthropogenic emissions were comparable to biogenic contributions (10-16%).

VOC reactivity in central California: comparing an air quality model to ground-based measurements

Abstract. Volatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare calculated and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NOx concentration and VOC reactivity (ROH,VOC), 2) the relationship between ROH,VOC and NOx, 3) total OH reactivity (ROH,total) and speciated contributions, and 4) the relationship between speciated ROH,VOC and NOx. We find that the model predicts ROH,total to within 25–40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NOx and VOC emissions by a factor of 2–3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic ROH,VOC are predicted fairly well over a range of NOx conditions. In suburban and rural locations, anthropogenic and other oxygenated ROH,VOC relationships are reproduced, but calculated biogenic and aldehyde ROH,VOC are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30–50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated ROH,VOC is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity.

Technical Note: Description and Use of the New Jump Mass Spectrum Mode of Operation for the Aerodyne Quadrupole Aerosol Mass Spectrometers (Q-AMS)

A new mode of operation for the Aerodyne Quadrupole Aerosol Mass Spectrometer (Q-AMS) has been developed and used to improve the detection limits and time resolution of the instrument. The Jump Mass Spectrum (JMS) mode works by stepping through a small number of specific user defined positions within the mass spectrum, increasing the time spent scanning specific m/z's. The JMS mode is conceptually similar to the Selected Ion Monitoring mode of some commercial quadrupole-based instrumentation and can be used for direct quantification when the fragmentation pattern is known. The JMS mode can also be used to augment the standard Q-AMS operation in Mass Spectrum mode when the fragmentation pattern is not known, improving the effective signal-to-noise ratio (SNR) and in turn the detection limits and time resolution. A decrease in detection limits for the Q-AMS by factors of 4.6, 3.9, 1.3, and 3.5 for nitrate, sulphate, total organics, and m/z 43 mass loadings respectively was achieved for 1 minute sampling (20 s in each of the three Q-AMS modes, monitoring 10 m/z in JMS mode). Although the benefit to the SNR of the total organic mass concentration measured by the Q-AMS is smaller, sensitivity to organic fragments which can act as markers for various sources and processes (such as fresh primary anthropogenic emissions, aged secondary organics, and biomass burning aerosol), is greatly increased by the JMS mode. Example data from applications that benefit from this technique are presented, including an aircraft platform and in smog chamber experiments, alongside high time-resolution, ground-based data.

Concentrations and sources of organic carbon aerosols in the free troposphere over North America

Aircraft measurements of water‐soluble organic carbon (WSOC) aerosol over NE North America during summer 2004 (ITCT‐2K4) are simulated with a global chemical transport model (GEOS‐Chem) to test our understanding of the sources of organic carbon (OC) aerosol in the free troposphere (FT). Elevated concentrations were observed in plumes from boreal fires in Alaska and Canada. WSOC aerosol concentrations outside of these plumes average 0.9 ± 0.9 μg C m−3 in the FT (2–6 km). The corresponding model value is 0.7 ± 0.6 μg C m−3, including 42% from biomass burning, 36% from biogenic secondary organic aerosol (SOA), and 22% from anthropogenic emissions. Previous OC aerosol observations over the NW Pacific in spring 2001 (ACE‐Asia) averaged 3.3 ± 2.8 μg C m−3 in the FT, compared to a model value of 0.3 ± 0.3 μg C m−3. WSOC aerosol concentrations in the boundary layer (BL) during ITCT‐2K4 are consistent with OC aerosol observed at the IMPROVE surface network. The model is low in the boundary layer by 30%, which we attribute to secondary formation at a rate comparable to primary anthropogenic emission. Observed WSOC aerosol concentrations decrease by a factor of 2 from the BL to the FT, as compared to a factor of 10 decrease for sulfate, indicating that most of the WSOC aerosol in the FT originates in situ. Despite reproducing mean observed WSOC concentrations in the FT to within 25%, the model cannot account for the variance in the observations (R = 0.21). Covariance analysis of FT WSOC aerosol with other measured chemical variables suggests an aqueous‐phase mechanism for SOA generation involving biogenic precursors.

Tracking changes in carbon monoxide budget over Europe between 1995 and 2000

The variation in carbon monoxide (CO) mixing ratio is of primary interest since it affects the atmospheric abundance of several trace gases, like methane, via extensive chemical feedback mechanisms. From the mid-1990s the global annual average mixing ratio of CO varied by about ±0–1% yr −1 while in 1998 a great pulse of CO emission increased the global CO concentration through mid-1999 by 16% over the background level. This surplus was primarily caused by heavy forest fires in several regions of the world. Our study was performed to reveal the potential causes of changes in the European CO budget and mixing ratio between 1995 and 2000 using a simple tropospheric box model. The primary anthropogenic emission from fossil fuel combustion and industrial processes in Europe showed a fairly constant annual decrease of about 4% yr −1 between 1995 and 2000, while the secondary anthropogenic CO source strength was reduced at a rate of about 3% yr −1. This decrease was partly balanced by sporadic pulses of European forest fire emissions. In spite of the reduction in the sources the region remained a net CO producer. The incremental change in the global CO budget caused by European sources was about 47.2±15.2 Tg CO yr −1 on average. The output of the model was validated against available observational data, both in absolute terms and with respect to the seasonal variation of the CO mixing ratio. The model revealed that the downward tendency of CO mixing ratios in Europe was temporarily offset by the contribution of large-scale forest fires in the northern hemisphere through long-range atmospheric transport.

Budget of organic carbon in a polluted atmosphere: Results from the New England Air Quality Study in 2002

An extensive set of volatile organic compounds (VOCs) and particulate organic matter (POM) was measured in polluted air during the New England Air Quality Study in 2002. Using VOC ratios, the photochemical age of the sampled air masses was estimated. This approach was validated (1) by comparing the observed rates at which VOCs were removed from the atmosphere with the rates expected from OH oxidation, (2) by comparing the VOC emission ratios inferred from the data with the average composition of urban air, and (3) by the ability to describe the increase of an alkyl nitrate with time in terms of the chemical kinetics. A large part of the variability observed for oxygenated VOCs (OVOCs) and POM could be explained by a description that includes the removal of the primary anthropogenic emissions, the formation and removal of secondary anthropogenic species, and a biogenic contribution parameterized by the emissions of isoprene. The OVOC sources determined from the data are compared with the available literature, and a satisfactory agreement is obtained. The observed sub‐μm POM was highly correlated with secondary anthropogenic gas‐phase species, strongly suggesting that the POM was from secondary anthropogenic sources. The results are used to describe the speciation and total mass of gas‐ and particle‐phase organic carbon as a function of the photochemical age of an urban air mass. Shortly after emission the organic carbon mass is dominated by primary VOCs, while after two days the dominant contribution is from OVOCs and sub‐μm POM. The total measured organic carbon mass decreased by about 40% over the course of two days. The increase in sub‐μm POM could not be explained by the removal of aromatic precursors alone, suggesting that other species must have contributed and/or that the mechanism for POM formation is more efficient than previously assumed.

Trends in Secondary Organic Aerosol at a Remote Site in Michigan's Upper Peninsula

The trends in secondary organic aerosol at a remote location are studied using atmospheric fine particulate matter samples collected at Seney National Wildlife Refuge (NWR) in northern Michigan. Detailed analysis of particle-phase organic compounds revealed very low concentrations of primary anthropogenic emissions and relatively high levels of organic di-, tri-, and tetracarboxylic acids thought to be indicators of secondary organic aerosols. Seasonal changes in these organic compounds were tracked by analyzing composites of monthly average samples. The concentration of aromatic and aliphatic dicarboxylic acids peak in July and taper off in the fall, which coincides with fine particle organic carbon concentration. In contrast, a chemical mass balance model used to quantify primary sources of particulate matter shows higher contributions from primary emissions in the winter. Complementing the monthly average concentrations, event-based composites of high volume samples were used to track the different species of secondary organic aerosol at the Seney NWR location. The distribution of aliphatic diacids and the aromatic di- and triacids varied with different atmospheric conditions, which suggests different precursor gases for these secondary organic aerosol components. The aliphatic diacid concentrations track with ambient concentrations of particle-phase pinonic acid. In addition, back-trajectories for the eight event-based composites are compared to the organic acid distributions and are linked to the distribution of organic acids present in the composites.

Monitoring of PM10 and PM2.5 around primary particulate anthropogenic emission sources

Investigations on the monitoring of ambient air levels of atmospheric particulates were developed around a large source of primary anthropogenic particulate emissions: the industrial ceramic area in the province of Castelló (Eastern Spain). Although these primary particulate emissions have a coarse grain-size distribution, the atmospheric transport dominated by the breeze circulation accounts for a grain-size segregation, which results in ambient air particles occurring mainly in the 2.5–10μm range. The chemical composition of the ceramic particulate emissions is very similar to the crustal end-member but the use of high Al, Ti and Fe as tracer elements as well as a peculiar grain-size distribution in the insoluble major phases allow us to identify the ceramic input in the bulk particulate matter. PM2.5 instead of PM10 monitoring may avoid the interference of crustal particles without a major reduction in the secondary anthropogenic load, with the exception of nitrate. However, a methodology based in PM2.5 measurement alone is not adequate for monitoring the impact of primary particulate emissions (such as ceramic emissions) on air quality, since the major ambient air particles derived from these emissions are mainly in the range of 2.5–10μm. Consequently, in areas characterised by major secondary particulate emissions, PM2.5 monitoring should detect anthropogenic particulate pollutants without crustal particulate interference, whereas PM10 measurements should be used in areas with major primary anthropogenic particulate emissions.

Characteristics of PM 2.5 carbonaceous aerosol in the Sihwa industrial area, Korea

In order to investigate the characteristics of carbonaceous fine aerosols, PM 2.5 particulate samples were collected in the Sihwa industrial complex area between February 1998 and 1999 and in Seoul between 31 May and 9 June 1999, respectively. The carbonaceous species were analyzed by the selective thermal manganese dioxide oxidation (TMO) method. In Sihwa, average OC and EC concentrations for the entire data set were measured to be 9.8 and 1.8 μg m −3, respectively. The OC concentrations were higher than those measured in other urban environments. The EC concentrations were lower than those of other urban environments. The OC/EC ratio measured at the Sihwa area was higher than those at other urban and rural environments. Backward trajectories of sampled air masses were performed to find out the sources of those higher OC/EC levels. Enrichment in the organic compounds during winter periods can be explained by the combination of primary local emissions from the industrial complex area and long-range transport of organic species from outside the Sihwa area. High OC values in June resulted from primary anthropogenic emissions and secondary organic aerosol formation rather than the atmospheric transport of organic compounds from the outside. In urban area of Seoul, the OC and EC concentrations in PM 2.5 during the summer were higher than those measured at other urban atmospheres. OC/EC ratios obtained in Seoul were lower than Sihwa. It can be concluded that carbonaceous species in Seoul were mainly emitted from primary anthropogenic sources.

Modeling atmospheric concentrations of mercury and deposition to the great lakes

Regional patterns of seasonal and annual average air concentrations and cumulative deposition of mercury to the Great Lakes basin are calculated with the ASTRAP model. The model treats the Hg system as three chemical components: elemental (Hg 0), particulate (Hg-p), and gaseous divalent (Hg-II). Primary anthropogenic emission inventories (i.e. emissions resulting from current activities) include surface and elevated sources of each of the three Hg species for eastern North America. Natural and secondary anthropogenic: emissions (i.e. reemission of Hg deposited or released during earlier anthropogenic activity) over the United States and Canada are estimated by defining an emission term for Hg' that varies with latitude and season. Global background concentrations of Hg 0 and Hg-p are specified to average annually 1.0 and 0.01 ng m −3, respectively. Rates of parameterizations of wet and dry removal are very rapid for Hg-II, intermediate for Hg-p, and very slow for Hg 0. Because of the disparate removal efficiencies, estimates of deposition resulting from anthropogenic emissions are critically dependent upon the speciation of emissions and, for the rapidly depositing Hg-II, the assumptions about effective stack heights. Integration of the Hg deposition field over the Great Lakes produces estimates of direct atmospheric loading from primary anthropogenic emissions of 1.44 and 2.46 t Hg yr −1 by wet and dry deposition, respectively. Estimates of direct loading from natural and secondary anthropogenic emissions of Hg 0 over the continent are 0.09 and 0.15 t Hg yr −1 for wet and dry deposition, respectively, while the corresponding contributions from the global background are estimated to be 0.15 and 0.39 t Hg yr −1, respectively. Although they constitute only 16% of estimated anthropogenic emissions, emissions of Hg-II contribute 78% of the current direct anthropogenic deposition to the Lakes, or 65% of the deposition of Hg from all sources. Revolatilization of Hg 0 from the Lakes is estimated to lie between 2.3 and 13.7 t Hg yr −1. Thus, revolatilization may well be greater than the direct atmospheric loading of all Hg species to the Lakes, 4.7 t Hg yr −1.