Recent decline of methyl bromide in the troposphere

Atmospheric methyl bromide (CH₃Br) measured at a remote ground station in the Arctic (mid-1996 to early 2002) and in the free troposphere at mid-latitude (early 1999 to early 2002) showed a steady annual average decrease of 4–6%. The trend was consistent with a simulation of the response to the phase-out schedule of anthropogenic emissions under the Montreal Protocol and its amendments, suggesting that a decrease in CH₃Br abundance in the Northern Hemisphere of as much as 40% from the level of the early 1990s would be possible by the completion date of the program.     

Tropospheric halocompounds and nitrous oxide monitored at a remote site in the Mediterranean

Analysis of time series and trends of nitrous oxide (N₂O) and halocompounds weekly monitored at the Mediterranean island of Lampedusa are discussed. Atmospheric N₂O levels showed a linear upward growth rate of 0.78 ppb yr^?1 and mixing ratios comparable with Northern Hemisphere global stations. CFC-11 and CFC-12 time series displayed a decline consistent with their phase-out. Chlorofluorocarbons (CFCs) replacing compounds and SF₆ exhibited an increasing temporal behaviour. The most rapid growth rate was recorded for HFC-134a with a value of 9.6% yr^?1. The industrial solvents CCl₄ and CH₃CCl₃, banned by the Montreal Protocol, showed opposite trends. While CH₃CCl₃ reported an expected decay of ?1.8 ppt yr^?1, an increasing rate of 5.7 ppt yr^?1 was recorded for CCl₄ and it is probably related to its relatively long lifetime and persisting emissions. Chlorinated halomethanes showed seasonality with a maximum in early April and a minimum at the end of September. Halon-1301 and Halon-1211 displayed a decreasing trend consistent with industry emission estimates.An interspecies correlation analysis gave positive high correlations between HCFC-22 and HFC-134a (+0.84) highlighting the common extensive employment as refrigerants. Sharing sources inferred the high coupling between CH₃Cl and CH₃Br (+0.73) and between CHCl₃ and CH₂Cl₂ (+0.77). A singular strong relationship (+0.55) between HFC-134a and CH₃I suggested the influence of an unknown anthropogenic source of CH₃I.Constraining of source and sink distribution was carried out by transport studies. Results were compared with the European Environment Agency (EEA) emission database. In contrast with the emission database results, our back trajectory analysis highlighted the release of large amounts of HFC-134a and SF₆ from Eastern Europe. Observations also showed that African SF₆ emissions may be considerable. Leakages from SF₆ insulated electrical equipments located in the industrialized Northern African areas justify our observations.     

Nonthermal Plasma Chemical Processing of Bromomethane

ABSTRACT

Nonthermal plasma chemical decomposition of bromomethane (CH₃Br) was investigated with a coaxial type packed-bed plasma reactor. It has been demonstrated that plasma chemical processing is an effective approach to decompose CH₃Br in a wide concentration range. It has been shown that CH₃Br decomposition reactivity depends on reactor operating factors such as background gas, O₂ concentration, and humidification. Higher decomposition efficiencies can be obtained in dry N₂. However, organic byproducts such as BrCN are concurrently produced under deaerated conditions. Water suppresses CH₃Br decomposition and also affects the yields of CO_x (CO and CO₂) and organic byproducts due to the involvement of some active species generated from water. The presence of O₂ retards CH₃Br decomposition by quenching high-energy electrons, while it suppresses organic byproducts and improves CO_x yield. The reacted carbons in CH₃Br are recovered as CO_x almost quantitatively in air. Higher CO₂ selectivities cannot be achieved by increasing O₂ concentration. NO_x formation, which is accompanied by CH₃Br decomposition, can be effectively suppressed by decreasing O₂ concentration down to 2%. Furthermore, reaction mechanisms are discussed by comparing the reactivities of CH₃Br and its congeners.     

Biogenic fluxes of halomethanes from Irish peatland ecosystems

Irish peatland ecosystems have been shown to be important sources of low molecular weight halocarbons. Emission of CH₃Br, CH₃Cl, CH₃I and CHCl₃ was recorded from all peatland sites monitored, with minor flux of other halocarbons at certain sites. Fluxes were found to be highly linked to incident light, with strong diurnal cycles recorded at all open peatland sites. Estimates of halomethane emissions, particularly from coastal peatland and conifer plantation forest floor sites, suggests that these ecosystems may make a significant contribution to the global budgets of several important halocarbons. Global annual fluxes of 4.7 (0.1–151.9), 0.9 (0.1–3.3), 5.5 (0.9–43.4), and 1.4 (0.1–12.8) Gg yr⁻¹ for CHCl₃, CH₃Br, CH₃Cl, and CH₃I, respectively, were determined for peatland ecosystems.     

Methylchloroform: Global distribution,seasonal cycles,and anthropogenic chlorine

It is evident that the global concentrations of methylchloroform (CH₃CCl₃) are increasing although at much lower rates than in the past. The ratio of concentrations in the two hemispheres has varied and is now declining, which reflects the constancy of the industrial emissions over the past 5 years. Observations show that the mid-latitude concentrations in both hemispheres are slightly lower during the summer than at other times, probably reflecting the greater removal of CH₃CCl₃ by OH radicals during summer. Calculations show that the lifetime of CH₃CCl₃ is about 6 (±1.5) years, which is considerably shorter than many previous estimates. It implies that there are probably 8 × 10⁵ molecules of OH/cm₃ of air, although this estimate may be uncertain by ±75%. The shorter lifetime is partly due to a revision of the estimated absolute concentration of CH₃CCl₃ in the atmosphere, which was found to be about 20% less than estimated previously. The relatively short lifetime suggests that in the future CH₃CCl₃ will contribute <15% of the anthropogenic chlorine in the troposphere, which is an approximate measure of its relative contribution to the depletion of the stratospheric ozone layer.     

Identification and quantification of methyl halide sources in a lowland tropical rainforest

In conjunction with the OP3 campaign in Danum Valley, Malaysian Borneo, flux measurements of methyl chloride (CH₃Cl) and methyl bromide (CH₃Br) were performed from both tropical plant branches and leaf litter in June and July 2008. Live plants were mainly from the Dipterocarpaceae family whilst leaf litter samples were representative mixtures of different plant species. Environmental parameters, including photosynthetically-active radiation, total solar radiation and air temperature, were also recorded. The dominant factor determining magnitude of methyl halide fluxes from living plants was plant species, with specimens of the genus Shorea showing persistent high emissions of both gases, e.g. Shorea pilosa: 65 ± 17 ng CH₃Cl h^?1 g^?1 (dry weight foliage) and 2.7 ± 0.6 ng CH₃Br h^?1 g^?1 (dry weight foliage). Mean CH₃Cl and CH₃Br emissions across 18 species of plant were 19 (range, <LOD ?76) and 0.4 (<LOD ?2.9) ng h^?1 g^?1 respectively; fluxes from leaf litter were 1–2 orders of magnitude smaller per dry mass. CH₃Cl and CH₃Br fluxes were weakly correlated. Overall, the findings suggest that tropical rainforests make an important contribution to global terrestrial emissions of CH₃Cl, but less so for CH₃Br.     

Influence of deployment time and surface wind speed on the accuracy of measurements of greenhouse gas fluxes using a closed chamber method under low surface wind speed

As a convenient method, the closed chamber method has been applied to determine gaseous emission fluxes from fully open animal feeding operations despite the measured fluxes being theoretically affected by deployment time, wind speed over the emitting surface and detected gas mass. This laboratory study evaluated the effects of deployment time (0 to 120 min) and external surface wind speed (ESWS) (0.00, 0.25, 0.50, 0.75, 1.00, 1.50 and 2.00 m sec^-1) on the measurement accuracy of a 300 mm (diameter) × 400 mm (height) (D300×H400) closed chamber using methane (CH₄), nitrous oxide (N₂O) and sulfur hexafluoride (SF₆) as reference gases. The results showed that the overall deviation ratio between the measured and reference CH₄ fluxes ranged from 9.99 % to -37.32 % and the flux was overestimated in the first 20 min. The measured N₂O and SF₆ emissions were smaller than the reference fluxes using the chamber. N₂O measurement accuracy decreased from -14.47 to -35.09% with deployment time extended to 120 min, while SF₆ accuracy sharply increased in the first 40 min, with the deviation stabilizing at approximately -5.00%. CH₄, N₂O and SF₆ measurements were significantly affected by deployment time and ESWS (P<0.05), and the interaction of those two factors greatly influenced CH₄ and SF₆ measurements (P<0.05). With the D300×H400 closed chamber, deployment times of 20 to 30 min and 10 to 20 min are recommended to measure CH₄ and N₂O, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec^-1.

Implications: This study recommended the suitable deployment times and wind speeds for using a D300 × H400 closed chamber to measure CH₄, N₂O, and SF₆ in an open system, such as a dairy open lot and manure stockpile, to help researchers and other related industry workers get accurate data for gas emission rate. Deployment times of 20 to 30 min and 10 to 20 min were recommended to measure CH₄ and N₂O emissions using the D300 × H400 closed chamber, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec^?1. For the measurement of SF₆, a typical tracer gas, a deployment of 70 to 90 min was suggested.     

Atmospheric Oxidation of Methyl Chloride Methylene Chloride,and Chloroform

Chlorinated atmospheric pollutants are presently receiving much attention because of expected chlorine-ozone interactions in the stratosphere.^1,2 The fully halogenated pollutants,such as CCI₃F, CCl₂F₂, and CCl₄, have no known removal processes that operate in the troposphere. These compounds are accumulating on a global scale, their atmospheric mixing ratios having reached about 2 X 10^-10 for CCl₂F₂,1.2 X 10^-10 for CCl₃F, and 9 X 10^-11 for CCl4.^3-5     

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.     

活性炭纤维吸附含溴甲烷气体的性能

采用动态吸附法在25℃下,测定了3种活性炭纤维(ACF-1、ACF-2和ACF-3)对含溴甲烷气体的吸附性能和回收效果,并对活性炭纤维的孔结构进行表征.探讨了孔结构、溴甲烷浓度、气体流量、循环使用次数等因素对活性炭纤维吸附溴甲烷性能的影响.结果表明,活性炭纤维比表面积大小及0.4～0.8 nm左右的微孔数量决定了其对溴甲烷吸附性能的优劣;气体中溴甲烷的浓度的提高使活性炭纤维对溴甲烷的穿透和饱和吸附量增加,而气体流量的增加则使活性炭纤维对溴甲烷的穿透和饱和吸附量降低,但两者均使穿透和饱和吸附时间缩短;活性炭纤维多次循环使用后,对溴甲烷的吸附容量明显地降低,循环12次后达到稳定吸附,其稳定吸附值为133.5 mg/g.     

Measurements of trace gases in the tropical tropopause layer

A unique dataset of airborne in situ observations of HCl, O₃, HNO₃, H₂O, CO, CO₂ and CH₃Cl has been made in and near the tropical tropopause layer (TTL). A total of 16 profiles across the tropopause were obtained at latitudes between 10°N and 3°S from the NASA WB-57F high-altitude aircraft flying from Costa Rica. Few in situ measurements of these gases, particularly HCl and HNO₃, have been reported for the TTL. The general features of the trace gas vertical profiles are consistent with the concept of the TTL as distinct from the lower troposphere and lower stratosphere. A combination of the tracer profiles and correlations with O₃ is used to show that a measurable amount of stratospheric air is mixed into this region. The HCl measurements offer an important constraint on stratospheric mixing into the TTL because once the contribution from halocarbon decomposition is quantified, the remaining HCl (>60% in this study) must have a stratospheric source. Stratospheric HCl in the TTL brings with it a proportional amount of stratospheric O₃. Quantifying the sources of O₃ in the TTL is important because O₃ is particularly effective as a greenhouse gas in the tropopause region.     

Spatial differences in ambient coarse and fine particles in the Monterrey metropolitan area,Mexico: Implications for source contribution

The ambient air of the Monterrey Metropolitan Area (MMA) in Mexico frequently exhibits high levels of PM₁₀ and PM_2.5. However, no information exists on the chemical composition of coarse particles (PM_c = PM₁₀ – PM_2.5). A monitoring campaign was conducted during the summer of 2015, during which 24-hr average PM₁₀ and PM_2.5 samples were collected using high-volume filter-based instruments to chemically characterize the fine and coarse fractions of the PM. The collected samples were analyzed for anions (Cl^–, NO₃^–, SO₄^2–), cations (Na⁺, NH₄⁺, K⁺), organic carbon (OC), elemental carbon (EC), and 35 trace elements (Al to Pb). During the campaign, the average PM_2.5 concentrations did not showed significance differences among sampling sites, whereas the average PM_c concentrations did. In addition, the PM_c accounted for 75% to 90% of the PM₁₀ across the MMA. The average contribution of the main chemical species to the total mass indicated that geological material including Ca, Fe, Si, and Al (45%) and sulfates (11%) were the principal components of PM_c, whereas sulfates (54%) and organic matter (30%) were the principal components of PM_2.5. The OC-to-EC ratio for PM_c ranged from 4.4 to 13, whereas that for PM_2.5 ranged from 3.97 to 6.08. The estimated contribution of Secondary Organic Aerosol (SOA) to the total mass of organic aerosol in PM_2.5 was estimated to be around 70–80%; for PM_c, the contribution was lower (20–50%). The enrichment factors (EF) for most of the trace elements exhibited high values for PM_2.5 (EF: 10–1000) and low values for PM_c (EF: 1–10). Given the high contribution of crustal elements and the high values of EFs, PM_c is heavily influenced by soil resuspension and PM_2.5 by anthropogenic sources. Finally, the airborne particles found in the eastern region of the MMA were chemically distinguishable from those in its western region.

Implications: Concentration and chemical composition patterns of fine and coarse particles can vary significantly across the MMA. Public policy solutions have to be built based on these observations. There is clear evidence that the spatial variations in the MMA’s coarse fractions are influenced by clearly recognizable primary emission sources, while fine particles exhibit a homogeneous concentration field and a clear spatial pattern of increasing secondary contributions. Important reductions in the coarse fraction can come from primary particles’ emission controls; for fine particles, control of gaseous precursors—particularly sulfur-containing species and organic compounds—should be considered.     

The relation between ozone,NOx and hydrocarbons in urban and polluted rural environments

Research over the past ten years has created a more detailed and coherent view of the relation between O₃ and its major anthropogenic precursors, volatile organic compounds (VOC) and oxides of nitrogen (NO_x). This article presents a review of insights derived from photochemical models and field measurements. The ozone–precursor relationship can be understood in terms of a fundamental split into a NO_x-senstive and VOC-sensitive (or NO_x-saturated) chemical regimes. These regimes are associated with the chemistry of odd hydrogen radicals and appear in different forms in studies of urbanized regions, power plant plumes and the remote troposphere. Factors that affect the split into NO_x-sensitive and VOC-sensitive chemistry include: VOC/NO_x ratios, VOC reactivity, biogenic hydrocarbons, photochemical aging, and rates of meteorological dispersion. Analyses of ozone–NO_x–VOC sensitivity from 3D photochemical models show a consistent pattern, but predictions for the impact of reduced NO_x and VOC in indivdual locations are often very uncertain. This uncertainty can be identified by comparing predictions from different model scenarios that reflect uncertainties in meteorology, anthropogenic and biogenic emissions. Several observation-based approaches have been proposed that seek to evaluate ozone–NO_x–VOC sensitivity directly from ambient measurements (including ambient VOC, reactive nitrogen, and peroxides). Observation-based approaches have also been used to evaluate emission rates, ozone production efficiency, and removal rates of chemically active species. Use of these methods in combination with models can significantly reduce the uncertainty associated with model predictions.     

Chemical characteristics of precipitation at metropolitan Newark in the US East Coast

To investigate the chemical characteristics of precipitation in the polluted coastal atmosphere, a total of 46 event-based precipitation samples were collected using a wet-only automatic precipitation collector from September 2006 to October 2007 at metropolitan Newark, New Jersey in the US East Coast. Samples were analyzed by ion chromatography for the concentrations of major inorganic ions (Cl⁻, NO₃⁻, SO₄²⁻, F⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺) and organic acid species (CH₃COO⁻, HCOO⁻, CH₂(COO)₂²⁻, C₂O₄²⁻). Selected trace metals (Sb, Pb, Al, V, Fe, Cr, Co, Ni, Cu, Zn, Cd) in samples were determined by ICPMS. Mass concentration results show that SO₄²⁻ was the most dominant anion accounting for 51% of the total anions, controlling the acidity of the precipitation. NH₄⁺ accounted for 48.6% of the total cations, dominating the precipitation neutralization. CH₃COO⁻ and HCOO⁻ were the two dominant water-soluble organic acid species, accounting for 42% and 40% of the total organic acids analyzed, respectively. Al, Zn and Fe were the three major trace metals in precipitation, accounting for 34%, 27%, and 25% of the total mass of metals analyzed. The pH values in precipitation ranged from 4.4 to 4.9, indicating an acidic nature. Enrichment Factor (EF) Analysis showed that Na⁺, Cl⁻, Mg²⁺ and K⁺ in the precipitation were primarily of marine origin, while most of the Fe, Co and Al were from crust sources. Pb, V, Cr, Ni were moderately enriched with EFs ranging 43–410, while Zn, Sb, Cu, Cd and F⁻ were highly enriched with EFs > 700, indicating significant anthropogenic influences. Factor analysis suggests 6 major sources contributing to the observed composition of precipitation at this location: (1) nitrogen-enriched soil, (2) secondary pollution processes, (3) marine sources, (4) incinerations, (5) oil combustions, and (6) malonate–vanadium enriched sources. To further explore the source–precipitation event relationships and seasonality, cluster analysis was performed for all precipitation events. Results show that about half of the precipitation events were characterized by mixed sources. Significant influences of nitrogen-enriched soil and marine sources were associated with precipitation events in spring and autumn, while secondary pollution processes, incineration and oil combustion contributed greatly in summer.     

Source identification of inorganic airborne particle fraction (PM10) at ultratrace levels by means of INAA short irradiation

Many studies have focused their attention on the determination of elements of toxicological and environmental interest in atmospheric particulate matter using analytical techniques requiring chemical treatments. The instrumental nuclear activation analysis technique allows achieving high sensitivity, good precision, and excellent limit of detection without pretreatment, also considering the problems related to the radioisotope characteristics (e.g., half-life time, interfering reactions, spectral interferences). In this paper, elements such as Al, As, Br, Cl, Cu, I, La, Mg, Mn, Na, Sb, Si, Ti, and V are studied in atmospheric PM₁₀ sampled in downtown Rome: The relative radionuclides after activation of the sample are characterized by very short (ranging from 2.24 to 37.2 min) and short (ranging from 2.58 h to 2.70 days) half-lives. Furthermore, As, Br, La, Mn, and Sb were also determined for evaluating the aerosol characteristics. The results, elaborated considering the matrix effects and the interfering reaction contribution to the radioisotope formation (e.g., ²⁸Al generated by both (n,γ) reaction from ²⁷Al and (n,p) reaction from ²⁸Si), show interesting values of As (0.3–6.1 ng m^?3), Cu (22–313 ng m^?3), Mn (17–125 ng m^?3), V (7–63 ng m^?3), higher than those determined in an area not influenced by autovehicular traffic, and significant levels of I (1–11 ng m^?3) and Ti (25–659 ng m^?3) in Rome PM₁₀. The other elements show a pattern similar to the very few data present in the literature. It should be underlined the good correlation (r ²) of Al vs. Mg (0.915) and Al vs. La (0.726), indicating a same sources for these species as well as Br–Sb showing a little lower correlation (0.623). This last hypothesis is confirmed by the study of the enrichment factors: Sb and Br may be attributed to anthropogenic sources; Cu, Cl, and I show a mixed origin (natural and anthropogenic), whereas Al, Si, Ti, Mn, Na, Mg, and As are of crustal origin. For having more information, a statistical approach based on the principal component analysis and the canonical discriminant analysis has been performed: All the samples (except one) are grouped in a cluster, and elements such as As, Br, Cu, I, La, Mn, Sb, Ti, and V are highly correlated, whereas Na and Cl and Mg and Al assemble in two different clusters. Finally, a comparison with other similar studies is reported showing interesting values for Al, As, Mg, Mn, and Ti.     

Characterization of African Dust (PM2.5) across the Atlantic Ocean during AEROSE 2004

An Aerosol and Oceanographic Science Expedition (AEROSE) on the NOAA Ship Ronald H. Brown collected PM_2.5 particles from a Saharan dust storm in March 2004. High levels of PM_2.5 (120 μg m^?3) were measured during this Saharan storm over the Atlantic Ocean. The particles were characterized for trace element content, with Al and Fe the most abundant metals. These metals were detected in high concentrations during the Saharan event and exhibited good correlations with PM_2.5, suggesting its soil origin. Other elements (Pb, Ni, Cd) did not correlate with Al and Fe, indicating their anthropogenic origin. Enrichment factor calculation conducted on these trace elements support our findings. Trace element analyses performed on particulate matter from a reference site on land in Puerto Rico (Fajardo), demonstrated similar results to those obtained in the AEROSE expedition, where high concentrations of PM_2.5 and Fe were present concomitantly with Saharan events at this station.     

Ambient concentrations and dry deposition fluxes of trace elements in Izmir,Turkey

Dry deposition samples were collected using a smooth surrogate surface at the Kaynaklar Campus of the Dokuz Eylul University in Izmir, Turkey. Concurrently ambient aerosol samples were collected. All samples were analyzed for anthropogenic and crustal trace elements. The average trace element concentrations and fluxes measured in this study were generally higher than those reported previously for urban and rural areas. The contribution of local terrestrial and anthropogenic sources were also investigated using enrichment factors (EFs) calculated relative to the local soil. Relatively lower EFs for ambient samples and high ambient concentrations indicated that the local soil was polluted and contributed significantly to ambient trace element concentrations. Deposition samples had higher EFs than the air samples. The EF sequences of trace elements were also different for deposition and ambient samples, probably due to the fact they have different mass median diameters and deposition velocities. The overall dry deposition velocities for trace elements calculated by dividing the particulate fluxes measured with the surrogate surfaces by ambient concentrations ranged from 0.6 (Al) to 6.2 cm s⁻¹ (Fe). The agreement between the experimental dry deposition velocities determined in this study and the previously reported ones using similar techniques for trace elements was good.     

Scenarios of global anthropogenic emissions of air pollutants and methane until 2030

We have used a global version of the Regional Air Pollution Information and Simulation (RAINS) model to estimate anthropogenic emissions of the air pollution precursors sulphur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO), primary carbonaceous particles of black carbon (BC), organic carbon (OC) and methane (CH₄). We developed two scenarios to constrain the possible range of future emissions. As a baseline, we investigated the future emission levels that would result from the implementation of the already adopted emission control legislation in each country, based on the current national expectations of economic development. Alternatively, we explored the lowest emission levels that could be achieved with the most advanced emission control technologies that are on the market today. This paper describes data sources and our assumptions on activity data, emission factors and the penetration of pollution control measures. We estimate that, with current expectations on future economic development and with the present air quality legislation, global anthropogenic emissions of SO₂ and NO_x would slightly decrease between 2000 and 2030. For carbonaceous particles and CO, reductions between 20% and 35% are computed, while for CH₄ an increase of about 50% is calculated. Full application of currently available emission control technologies, however, could achieve substantially lower emissions levels, with decreases up to 30% for CH₄, 40% for CO and BC, and nearly 80% for SO₂.     

A review of biomarker compounds as source indicators and tracers for air pollution

An overview of the application of organic geochemistry to the analysis of organic matter on aerosol particles is presented here. This organic matter is analyzed as solvent extractable bitumen/ lipids by gas chromatography-mass spectrometry. The organic geochemical approach assesses the origin, the environmental history and the nature of secondary products of organic matter by using the data derived from specific molecular analyses. Evaluations of production and fluxes, with cross-correlations can thus be made by the application of the same separation and analytical procedures to samples from point source emissions and the ambient atmosphere. This will be illustrated here with typical examples from the ambient atmosphere (aerosol particles) and from emissions of biomass burning (smoke). Organic matter in aerosols is derived from two major sources and is admixed depending on the geographic relief of the air shed. These sources are biogenic detritus (e.g., plant wax, microbes, etc.) and anthropogenic particle emissions (e.g., oils, soot, synthetics, etc.). Both biogenic detritus and some of the anthropogenic particle emissions contain organic materials which have unique and distinguishable compound distribution patterns (C₁₄-C₄₀). Microbial and vascular plant lipids are the dominant biogenic residues and petroleum hydrocarbons, with lesser amounts of the pyrogenic polynuclear aromatic hydrocarbons (PAH) and synthetics (e.g., chlorinated compounds), are the major anthropogenic residues. Biomass combustion is another important primary source of particles injected into the global atmosphere. It contributes many trace substances which are reactants in atmospheric chemistry and soot paniculate matter with adsorbed biomarker compounds, most of which are unknown chemical structures. The injection of natural product organic compounds into smoke occurs primarily by direct volatilization/steam stripping and by thermal alteration based on combustion temperature. Although the molecular composition of organic matter in smoke particles is highly variable, the molecular tracers are generally still source specific. Retene has been utilized as a tracer for conifer smoke in urban aerosols, but is not always detectable. Dehydroabietic acid is generally more concentrated in the atmosphere from the same emission sources. Degradation products from biopolymers (e.g., levoglucosan from cellulose) are also excellent tracers. An overview of the biomarker compositions of biomass smoke types is presented here. Defining additional tracers of thermally-altered and directly-emitted natural products in smoke aids the assessment of the organic matter type and input from biomass combustion to aerosols. The precursor to product approach of compound characterization by organic geochemistry can be applied successfully to provide tracers for studying the chemistry and dispersion of ambient aerosols and smoke plumes. Presented at the 6th FECS Conference on Chemistry and the Environment, Atmospheric Chemistry and Air Pollution, August 26–28, 1998, Copenhagen.     

A study on As, Cu, Pb and Zn (bio)availability in an abandoned mine area (São Domingos, Portugal) using chemical and ecotoxicological tools

The aim of this study was to relate the results obtained by chemical methods, used to assess environmental (bio)availability, with the ecotoxic response and bioaccumulation of trace elements (TE) by the earthworm Eisenia fetida exposed to field-contaminated, metal-polluted soils from a sulphide mine. The extracting solution 0.5 M NH₄CH₃COO, 0.5 M CH₃COOH and 0.02 M EDTA (pH 4.7), was able to predict environmental bioavailability of TE to E. fetida. However, the toxicological bioavailability could not be predicted from the results of the chemical extractions or from the bioaccumulation results: E. fetida reproduction was higher in soils where environmental bioavailability of TE and bioaccumulation values were also higher. In this study, the toxic response of the organism seemed to be more influenced by the overall nutritional status of the soil (e.g. pH, organic matter, plant nutrient availability and cation exchange capacity) than by its TE contamination. In the case of anthropogenic multi-contaminated sites, the different soil characteristics exert an important and confounding influence in the toxic response and the relationship between different bioavailable fractions cannot be easily established, emphasising the need to combine results from chemical methods with those from bioassays when evaluating the bioavailability of TE in these soils.