Modelling the contribution of different sources of sulphur to atmospheric deposition in the United Kingdom

In order to understand relationships between sources and receptors of atmospheric deposition, computer models must be used. This paper describes a Lagrangian acid deposition model that represents emissions of trace species across Northern Europe. The chemistry of sulphur dioxide, dimethyl sulphide and hydrogen sulphide is represented and the model tested against estimates of UK wet and dry deposition. Mean UK wet and dry deposition for the period 1992–1994 was 206 and 145 ktonne S yr^-1, respectively. The model predicted wet and dry deposition of 222 and 166 ktonne S yr^-1, in good agreement with measurements. The model has been used to examine the sources of deposited S to the UK. For a base year of 1992, 86% of the UK's SO₂ emissions are exported. The S deposition attributable from mainland European sources was 36% of the UK total S deposition, in good agreement with other UK models but this differs substantially from the calculations of the EMEP model. Natural sources of S deposition from planktonic emissions of dimethyl sulphide, biological emissions of hydrogen sulphide and non-eruptive volcanic emissions of sulphur dioxide contributed approximately 1% of the modelled UK S deposition, of which 95% originated from dimethyl sulphide. The explicit chemical scheme for dimethyl sulphide incorporated into the model showed that 24% of the resultant deposited S was methane sulphonic acid. Boundary conditions of the model were tested and it was found that initialisation of sulphur dioxide and sulphate concentrations to representative ambient conditions had a very small effect. The modelled contribution of UK and European sources to UK S deposition was approximately 40 and 60%, respectively, showing the dramatic change arising from projected UK SO₂ emissions in 2010. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mega-Development Trends in the Amazon: Implications for Global Change

This paper describes four global-change phenomena that are having major impacts on Amazonian forests. The first is accelerating deforestation and logging. Despite recent government initiatives to slow forest loss, deforestation rates in Brazilian Amazonia have increased from 1.1 million ha yr^–1 in the early 1990s, to nearly 1.5 million ha yr^–1 from 1992–1994, and to more than 1.9 million ha yr^–1 from 1995–1998. Deforestation is also occurring rapidly in some other parts of the Amazon Basin, such as in Bolivia and Ecuador, while industrialized logging is increasing dramatically in the Guianas and central Amazonia.The second phenomenon is that patterns of forest loss and fragmentation are rapidly changing. In recent decades, large-scale deforestation has mainly occurred in the southern and eastern portions of the Amazon — in the Brazilian states of Pará, Maranho, Rondônia, Acre, and Mato Grosso, and in northern Bolivia. While rates of forest loss remain very high in these areas, the development of major new highways is providing direct conduits into the heart of the Amazon. If future trends follow past patterns, land-hungry settlers and loggers may largely bisect the forests of the Amazon Basin.The third phenomenon is that climatic variability is interacting with human land uses, creating additional impacts on forest ecosystems. The 1997/98 El Niño drought, for example, led to a major increase in forest burning, with wildfires raging out of control in the northern Amazonian state of Roraima and other locations. Logging operations, which create labyrinths of roads and tracks in forsts, are increasing fuel loads, desiccation and ignition sources in forest interiors. Forest fragmentation also increases fire susceptibility by creating dry, fire-prone forest edges.Finally, recent evidence suggests that intact Amazonian forests are a globally significant carbon sink, quite possibly caused by higher forest growth rates in response to increasing atmospheric CO₂ fertilization. Evidence for a carbon sink comes from long-term forest mensuration plots, from whole-forest studies of carbon flux and from investigations of atmospheric CO₂ and oxygen isotopes. Unfortunately, intact Amazonian forests are rapidly diminishing. Hence, not only is the destruction of these forests a major source of greenhouse gases, but it is reducing their intrinsic capacity to help buffer the rapid anthropogenic rise in CO₂.     

Air pollution impact on Swedish forests-present evidence and future development

Research during the last five years has provided evidence that there is a long-term influence of air pollutants on forest ecosystems also in the southern parts of North Europe. High loads of acidity, sulphur and nitrogen affect soil conditions, trees as well as other organisms.In South and West Sweden changes in soil acidity (pH) have been registered during the last 60 years. The changes not only occur in the humus layer, but also in the lower part of the mineral soil. These latter changes cannot be explained without the action of strong acids originating from anthropogenic air pollution.Losses of elements like magnesium, calcium and potassium occur and phosphorus become less available to plants. An increased demand for plant mutrients is a consequence of the increased fall-out of nitrogen compounds. Nutrient imbalances of trees seem to be the result. Increased sensitivity to frost and drought as well as insects and pathogens is expected.The increased soil acidity and the eutrophication of soils caused by the continued input of nitrogen contributes to changes in plant communities.If we assume that there are no changes in deposition, land-use and management of the forests in SW Sweden, the better forest soils (brown forest soils) will have a continued acidification of humus and mineral soil layers resulting in high levels of aluminium and low levels of calcium. This will create a critical situation for roots and mycorrhiza. Soils that are already acid may not become more acidified, but will still be subject to losses of essential elements.Critical deposition levels or loads of acids (hydrogen ions) and nitrogen rendering no further deterioration of soils and leaching have been set to 0.1–0.2 keq·ha^-1yr^-1 for S Scandinavia (present level 1 keq·ha^-1yr^-1). For nitrogen the critical load is 10–20 kg N ha^-1yr^-1 (present range 10–25 kg ha^-1yr^-1).Contribution from Fourth World Wilderness Congress — Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.     

Sulphate, Nitrogen and Base Cation Budgets at 21 Forested Catchments in Canada, the United States and Europe

To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s average) for sulphate (SO₄), inorganic nitrogen (NO₃-N; NH₄-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada, the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more than 9 years of data were available (14 regions, 17 sites). Annual average SO₄ deposition during the 1990s ranged between 7.3 and 28.4 kg ha⁻¹ per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha⁻¹ per year, of which 41–67% was nitrate (NO₃-N). Over the period of record, SO₄ concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO₄ in runoff decreased at 14/17 catchments. In contrast, NO₃-N concentrations in deposition decreased in only 1/14 regions, while NH₄-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH₄-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively, which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at 18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31–100%; median 94%) was retained in the catchments, although there was a tendency for greater NO₃-N leaching at sites receiving higher (<7 kg ha^-1 per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for 18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively. Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions in SO₄ and H⁺ deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of Ca and Mg of primary concern. The U.S. Government's right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Characteristic Study of Dry Deposition, Concentration, Compositions for Particulates Mass and Ionic Species During Summer and Autumn Season at a Traffic Sampling Site

Aerosol samples for dry deposition and total suspend particulates (TSP) were collected from August to November of 2003 in central Taiwan. Ion chromatography was used to analyze the related water-soluble ionic species (Cl⁻, NO₃ ⁻, SO₄ ²⁻, Na⁺, NH₄ ⁺, K⁺, Mg²⁺ and Ca²⁺). The results obtained in this study indicated that the ambient air particulate mass concentrations in the daytime period (averaged 975.4 μg m⁻³) were higher than the nighttime period (averaged 542.1 μg m⁻³). And the daytime dry deposition fluxes (averaged 58.12 μg m⁻² sec⁻¹) were about 2.2 times as that of nighttime dry deposition fluxes (averaged 26.54 μg m⁻² sec⁻¹) of the downward dry deposition. The average values downward and upward of dry deposition fluxes for the weekend period were almost higher than the weekday period for either daytime or nighttime period. Furthermore, the average daytime dry deposition fluxes (averaged 26.37 μg m⁻² sec⁻¹) were also about 2.3 times as that of nighttime dry deposition fluxes (averaged 11.52 μg m⁻² sec⁻¹). Moreover, the results also indicate that SO₄ ²⁻ and Ca²⁺ have higher average composition for total suspended particulates in the daytime period while Ca²⁺, SO₄ ²⁻, and Na⁺ have the higher average composition for total suspends particulates in the nighttime period.     

Estimation of Critical Loads of Acidity for Lakes in Northeastern United States and Eastern Canada

The New England Governors and Eastern Canadian Premiers (NEG/ECP) adopted the Acid Rain Action Plan in June 1998, and issued a series of action items to support its work toward a reduction of sulfur dioxide (SO₂) and nitrogen oxide (NO_x) emissions in northeastern North America. One of these action items was the preparation of an updated critical load map using data from lakes in the NEG/ECP area. Critical load maps provide a more complete index of the surface water sensitivity to acidification. Combined sulfur and nitrogen critical loads and deposition exceedances were computed using Henriksen's Steady-State Water Chemistry (SSWC) model. Results show that 28% of all 2053 lakes studied have a critical load of 20 kg/ha/year or less, making them vulnerable to acid deposition. Emission reductions, and more specifically SO₂ emission reductions have proven beneficial because critical loads were exceeded in 2002 for 12.3% of all studied lakes. Those lakes are located in the more sensitive areas where geology is carbonate-poor. Of these lakes, 2.9% will never recover even with a complete removal of SO₄ deposition. Recovery from acidification for the remaining 9.4% of the lakes will require additional emission SO₂ reductions.     

Monitoring the results of Canada/U.S.A acid rain control programs: some lake responses

Aquatic acidification by deposition of airborne pollutants emerged as an environmental issue in southeastern Canada during the 1970s. Drawing information from the extensive research and monitoring programs, a sequence of issue assessments demonstrated the necessity of reducing the anthropogenic emissions of acidifying pollutants, particularly sulphur dioxide (SO₂). The 1991 Canada-U.S. Air Quality Agreement (AQA) was negotiated to reduce North American SO₂ emissions by 40% relative to 1980 levels by 2010, and at present, both countries have reduced emissions beyond their AQA commitment. In response to reduced SO₂ emissions, atmospheric deposition of sulphate (SO₄ ^2–) and SO₄ ^2– concentrations in many lakes have declined, particularly in south-central Ontario and southern Québec. Sulphate deposition still exceeds aquatic critical loads throughout southeastern Canada however. Increasing pH or alkalinity (commonly deemed recovery) has been observed in only some lakes. Several biogeochemical factors have intervened to modify the lake chemistry response to reduced SO₄ ^2– input, notably release of stored SO₄ ^2– from wetlands following periods of drought and reduction in the export of base cations from terrestrial soils. Three examples from Ontario are presented to illustrate these responses. Significant increases in pH and alkalinity have been observed in many lakes in the Sudbury area of Ontario due to the large reductions in local SO₂ emissions; early-stage biological recovery is evident in these lakes. An integrated assessment model predicts that AQA emission reductions will not be sufficient to promote widespread chemical or biological recovery of Canadian lakes. Monitoring and modeling are mutually supporting assessment activities and both must continue.     

The predicted effect of SO2 emission controls on the water quality of eastern Canadian lakes

Changes in SO _inf4 ^sup2- deposition predicted to occur in response to implementation of announced SO₂ emission control programs in Canada and the U.S.A. have been used as input to water chemistry models thereby giving an estimate of the changes in lake acid neutralizing capacity (ANC) and pH that can be expected from these programs. Eastern Canada has been divided into 22 subregions for the purpose of this analysis. Relative to the current level (1982–86) of SO _inf4 ^sup2- deposition (Scenario 1), the effect of the Canadian SO₂ emission control program alone (Scenario 2) is compared to that obtained when controls are implemented throughout North America (Scenarios 3 and 4). SO₂ emission reduction will effect a shrinkage of the high wet SO _inf4 ^sup2- deposition field in NE North America such that under Scenario 4 conditions, almost no area will remain in Canada that receives >20 kg ha^-1 yr^-1. The greatest decrease in deposition and resulting change in lake chemistry occurs in southern Ontario and southwestern Quebec. ANC distributions shift to higher concentrations and the percentage of lakes having pH<6 decreases in these areas. The Atlantic Provinces will obtain only a minor benefit from the control programs, i.e. experiencing only a small decrease in deposition and improvement in water quality. High sensitivity of the terrain in many parts of Atlantic Canada means that large numbers of lakes will remain acidic (i.e. ANC<0) and/or have pH<6 (an important biological threshold) even after full implementation of the current plans for SO₂ control in Canada and the U.S.     

The Rengen Grassland experiment: bryophytes biomass and element concentrations after 65 years of fertilizer application

The Rengen Grassland Experiment in Germany, established in 1941, consists of the following fertilizer treatments applied under a two cut management: control, Ca, CaN, CaNP, CaNP-KCl, and CaNP-K₂SO₄. The aim of this study was (1) to identify effects of fertilizer application on biomass and species composition of bryophytes and (2) to investigate the impact of fertilizer application on macro- (N, P, K, Ca, Mg), micro- (Cu, Fe, Mn, Zn), and toxic (As, Cd, Cr, Pb, Ni) element concentrations in bryophyte biomass. In June 2006, Rhytidiadelphus squarrosus was the only bryophyte species recorded in the control. In treatment Ca, R. squarrosus was the dominant bryophyte species whereas Brachythecium rutabulum occurred sporadically only in a single plot of that treatment. The latter was the only bryophyte species collected in CaN, CaNP, CaNP-KCl, and CaNP-K₂SO₄ treatments. Dry matter accumulation of bryophytes was highest in the control (180 g m^???2) followed by Ca (46 g m^???2), CaNP (25 g m^???2), CaNP-KCl (15 g m^???2), CaNP-K₂SO₄ (9 g m^???2), and CaN (2 g m^???2) treatments. A negative correlation between biomass production of bryophytes and dry matter production of vascular plants was revealed up to a threshold value of 400 g m^???2. Above this limit, biomass production of bryophytes remained obviously unaffected by further increase in biomass production of vascular plants. A significant effect of treatment on As, Cd, Cr, Fe, Mn, Ni, Pb, P, Ca, Mg, K, and N concentrations was revealed. Concentrations of these elements were a function of amount of elements supplied with fertilizers. Bryophytes seem to be promising bio-indicators not only for airborne deposition of toxic element but also for fertilizer introduced as well.     

Quantifying Carbon Budgets Of Conifer Mediterranean Forest Ecosystems, Turkey

Abstact Aboveground biomass, aboveground litterfall, and leaf litter decomposition of five indigenous tree stands (pure stands ofPinus brutia,Pinus nigra,Cedrus libani,Juniperus excelsa, and a mixed stand ofAbies cilicica,P. nigra, andC. libani) were measured in an eastern Mediterranean evergreen needleleaf forest of Turkey. Measurements were converted to regional scale estimates of carbon (C) stocks and fluxes of forest ecosystems, based on general non-site-specific allometric relationships. Mean C stock of the conifer forests was estimated as 97.8± 79 Mg C ha⁻¹consisting of 83.0 ± 67 Mg C ha⁻¹in the aboveground and 14.8 ± 12 Mg C ha⁻¹in the belowground biomass. The forest stands had mean soil organic carbon (SOC) and nitrogen (SON) stocks of 172.0 ± 25.7 Mg C ha⁻¹and 9.2 ± 1.2 Mg N ha⁻¹, respectively. Mean total monthly litterfall was 376.2± 191.3 kg C ha⁻¹, ranging from 641 ± 385 kg C ha⁻¹forPinus brutiato 286 ± 82 kg C ha⁻¹forCedrus libani. Decomposition rate constants (k) for pine needles were 0.0016 forCedrus libani, 0.0009 forPinus nigra, 0.0006 for the mixed stand, and 0.0005 day⁻¹forPinus brutiaand Juniperus excelsa. Estimation of components of the C budgets revealed that the forest ecosystems were net C sinks, with a mean sequestration rate of 2.0 ± 1.1 Mg C ha⁻¹ yr⁻¹ranging from 3.2 ± 2 Mg C ha⁻¹forPinus brutiato 1.6 ± 0.6 Mg C ha⁻¹forCedrus libani. Mean net ecosystem productivity (NEP) resulted in sequestration of 98.4 ± 54.1 Gg CO₂ yr⁻¹from the atmosphere when extrapolated for the entire study area of 134.2 km²(Gg = 10⁹ g). The quantitative C data from the study revealed the significance of the conifer Mediterranean forests as C sinks     

Monitoring of Criteria Air Pollutants in Bursa, Turkey

The concentrations of criteria air pollutants such as CO, NO_x (NO + NO₂), SO₂ and PM were measured in the period of May 2001 and April 2003 in the city of Bursa, Turkey. The average concentrations for this period were 1115±1600 μg/m³, 29±50 μg/m³, 51±24 μg/m³, 79±65 μg/m³, 40±35 μg/m³, 98±220 μg/m³, for CO, NO, NO₂, NO_x, SO₂ and PM, respectively. Temporal changes in concentrations were analyzed using meteorological factors. Correlations among pollutant concentrations and meteorological parameters showed weak relations nearly in all data. Lower concentrations were observed in the summer months while higher concentrations were measured in the winter months. The increase in winter concentrations was probably due to residential heating. Pollutants were associated with each other in order to have information about their origin. NO_x/SO₂ ratio was also examined to bring out the source origin contributing on air pollution (i.e., traffic or stationary).     

Detection of sulphur dioxide in the air using Scotch pine needles

Air quality is especially important in surface layers, for it is this layer that provides the living components of environment with the needed oxygen and carbon dioxide. Various air polluting gases penetrate cells affecting and contaminating them. Chloroplast shell of some pine species, for instance, doubles under the impact of carbon dioxide which is followed by tillacoids swelling and reduction.Literature provides opinions of some authors, who consider Scotch pine needle to be a biological indicator of sulphur dioxide. Others object to it basing on the observations of physiological development.The property of a Scotch pine as that of biological indicator manifests in SO₂ absorption by its needles. The analysis of total content of SO₂ in the needles shows an increase of SO₂ concentration.Sulphur in the needles is found in the form of organically bound sulphur, aminoacids, hormones as well as in the form of sulphates.Basing on our previous analysis we have generalized the data on the correlation concentrations of sulphur dioxide in the air and general concentrations of sulphur in the needles. We have supplemented the observations with the analyses of organically bound sulphur and concentrations of nonorganic sulphur. According to research data, needles contain a characteristic and rather stable quantity of organically bound sulphur.So we may state that the SO _inf4 ^sup2– concentration and the amount of SO₂ absorbed from the air are interdependent.Some authors state that SO _inf4 ^sup2– content in the soil doesn't affect sulphur content in pine needles. That is why we studied the affect of SO _inf4 ^sup2– content in the soil on sulphur content in Scotch pine needles.We could prove this statement by means of various kinds of analyses only partially. The ion transport is affected by the presence of other ions, pH and a lot of other factors.What may be said for sure is that different qualities of soils gave only minor and insignificant deviations.Hence our assumption about the SO₂ contamination from air, proved by its effect on the soils, turns to suit approximate measurements.     

固定污染源废气中三氧化硫测试方法初探

建立了异丙醇吸收-分光光度法测试固定污染源中三氧化硫(SO_3)的方法,分别连续9次测试低、中、高3个质量浓度的SO_3烟气。测试结果表明,相对误差分别为7. 5%,-2. 6%和6. 7%,相对标准偏差分别为3. 3%,1. 7%和4. 1%,方法的准确度和精密度较好。方法检出限为0. 1 mg/m~3,测定下限为0. 4 mg/m~3。二氧化硫(SO_2)、一氧化碳(CO)、氮氧化物(NO_x)、硫化氢(H_2S)、含湿量、烟尘等因素对方法的干扰较小,方法适用于现场测试。     

Performances and application of a passive sampling method for the simultaneous determination of nitrogen dioxide and sulfur dioxide in ambient air

The performances and applicability of a diffusion tubesampler for the simultaneous measurements of NO₂ andSO₂ in ambient air were evaluated. SO₂ andNO₂are collected by the passive sampler using triethanolamine astrapping agent and are determined as sulphate and nitrite withion chromatography. The detection limit (2.3 g m^-3 ofNO₂ and 4.2 g m^-3 of SO₂ for two weekssampling) is adequate for the determination of concentrationsin urban and industrial areas. Precision of the method as RSDis in mean 5% for NO₂ and 12% for SO₂ at theconcentration levels in urban areas. Calibration of the methodwas performed in the field conditions by comparison between theresponses of sampler and the concentrations measured by thecontinuous monitors. High degree of linearity (correlationcoefficients > 0.8) is found between the passive sampler tubeand the continuous monitor data for both NO₂ and SO₂.To reduce the wind velocity influence on passive sampling ofdiffusion tubes, a protective shelter was tested in this study.The overall uncertainty of one measure for the optimised methodis estimated at 5 g m^-3 for NO₂ and 6g m^-3 for SO₂. Suitability of this passivesampling method for air pollution monitoring in urban areas wasdemonstrated by the results shown in this paper on a campaigncarried out in the French agglomeration.     

Fluctuations of Climatic Conditions, Elemental Cycling and Forest Growth at the Watershed Scale

The relationships between fluctuations in climatic conditions,forest productivity and elemental cycling were studied from 1994 to 1997 in a headwater catchment of the southern Laurentians dominated by sugar maple (Acer saccharumMarsh.) growing on podzolic soils. Annual budgets show that H⁺, K, and NO₃ were retained in the watershed whileCa, Mg and Na were lost. The magnitude of the net annual budget for Ca, Mg and Na was correlated to annual variationsin precipitation with the absolute budget value decreasing during dry years. Stemwood (r² = 0.85) and total tree biomass production (r² = 0.99) were correlated with mean annual temperature but fine roots and leaf litter werenot. During the growing season, the pH of the organic horizons(FH) decreased as the volumetric water content of soildecreased. A positive association was also found between airtemperature and H₂O-soluble (r² = 0.88) and PO₄-extractable (r² = 0.99) SO₄ in the upper B horizon. On a multi-year scale, we suspect that the decreasein the storage of inorganic SO₄ in the soil results from the cumulative effects of annual variations in climatic conditions superimposed on the long-term decrease in SO₄deposition from the atmosphere. These soil changes were reflected by a decline in SO₄, Ca and Mg concentrationsin the stream. The generalisation of the observed short-term patterns to longer time scales must be approached with caution. Yet, our results indicate that the associations between climatic variations and the biogeochemistry of the ecosystem occur at different spatial and temporal scales and integrate abroad range of chemical components and ecosystem compartments. This reflects the inherent complexity of natural systems and offers a vast palette of indicators of the response of terrestrial ecosystems to variations in the intensity of environmental factors such as climatic conditions.     

Carbon Sequestration Potential of Indian Forests

The forestry sector can not only sustain its carbon but also has the potential to absorb carbon from the atmosphere. India has maintained approximately 64 Mha of forest cover for the last decade. The rate of afforestation in India is one of the highest among the tropical countries, currently estimated to be 2 Mha per annum. The annual productivity has increased from 0.7 m³ per hactare in 1985 to 1.37 m³ per hectare in 1995. Increase in annual productivity directly indicates an increase in forest biomass and hence higher carbon sequestration potential. The carbon pool for the Indian forests is estimated to be 2026.72 Mt for the year 1995. Estimates of annual carbon uptake increment suggest that our forests and plantations have been able to remove at least 0.125 Gt of CO₂ from the atmosphere in the year 1995. Assuming that the present forest cover in India will sustain itself with a marginal annual increase by 0.5 Mha in area of plantations, we can expect our forests to continue to act as a net carbon sink in future.     

Observational and modeling study of dry deposition on surrogate surfaces in a South China city: implication of removal of atmospheric crustal particles

Dry deposition samples collected during 1999–2001 at a South China site using surrogate surfaces were analyzed by capillary electrophoresis. Collector surface properties played important roles to the dry deposition. The deposition velocities for various species ranged from 0.02 to 1.69 cm s^???1, in general agreement with literature values. More than 90% of Ca^2?+? was deposited by sedimentation and its comparable values of dry or wet removal residence times imply that dry deposition is an important atmospheric removal process for the ubiquitous crustal species in South China, compared with precipitation scavenging. Relatively good agreement was found when the species deposition velocities were modeled based on up-to-date knowledge of particle dry deposition. The total depositions for anthropogenic and crustal species in northern China are likely to be much higher than those in the south, including our site where the fluxes of the acidic species SO₄ ^2??? and NO₃ ^??? were 4.4 and 2.2 g m^???2 year^???1, respectively. The sum of dry deposition for cations Na^?+?, Ca^2?+?, Mg^2?+?, and K^?+? contributes 44% of the total flux, which is equivalent to the value estimated in Europe.     

Atmospheric concentrations of nitric acid, sulfur dioxide, particulate nitrate and particulate sulfate, and estimation of their dry deposition on the urban- and mountain-facing sides of Mt. Gokurakuji, Western Japan

Atmospheric concentrations of nitric acid (HNO₃), sulfur dioxide (SO₂), particulate nitrate and particulate sulfate on the urban- and mountain-facing sides of Mt. Gokurakuji were measured from November 2002 to October 2003, in order to evaluate the effects of anthropogenic activity on air quality and dry deposited nitrate and sulfate on the surfaces of pine foliage. The results showed that HNO₃, SO₂ and concentrations were significantly higher (P < 0.05) on the urban-facing side (1.54, 2.48 and 0.65 μg m⁻³, respectively) than the mountain-facing side (0.67, 1.19 and 0.37 μg m⁻³, respectively), while concentrations did not differ significantly between the two sides (urban-facing: 2.80 μg m⁻³; mountain−facing: 2.05 μg m⁻³). Indirect estimates of dry deposition rates of nitrate and sulfate to the surfaces of pine foliage based on the measured concentrations approximately agreed with the measured values determined by the foliar rinsing technique in a previous study. It was found that HNO₃ was the major source (approximately 80%) of dry deposited nitrate on pine foliage, while the contribution from was about equal to that from SO₂. In conclusion, HNO₃ and SO₂ appear to be dominant species reflecting higher dry deposition rates of nitrate and sulfate on the urban-facing side compared to the mountain-facing side of Mt. Gokurakuji.     

Characteristics of CO2 release from forest soil in the mountains near Beijing

CO₂ release from forest soil is a key driver of carbon cycling between the soil and atmosphere ecosystem. The rate of CO₂ released from soil was measured in three forest stands (in the mountainous region near Beijing, China) by the alkaline absorption method from 2004 to 2006. The rate of CO₂ released did not differ among the three stands. The CO₂ release rate ranged from ??341 to 1,193 mg m^???2 h^???1, and the mean value over all three forests and sampling times was 286 mg m^???2 h^???1. CO₂ release was positively correlated with soil water content and the soil temperature. Diurnally, CO₂ release was higher in the day than at night. Seasonally, CO₂ release was highest in early autumn and lowest in winter; in winter, negative values of CO₂ release suggested that CO₂ was absorbed by soil.     

Carbon fixation efficiency of plants influenced by sulfur dioxide

In the land ecosystem, the forest can absorb the carbon dioxide (CO₂) in the atmosphere and turn the CO₂ into organic carbon to store it in the plant body. About 2 × 10¹¹ tons of CO₂ changes through photosynthesis into organic matter by plant annually. In this research, ten kinds of woody plants were selected for assessing the carbon fixation ability influenced by sulfur dioxide (SO₂). The tested trees were put into a fumigation chamber for 210 days in a 40-ppb SO₂ environment. The results of this study showed that there was no clear symptom of tested trees under a 40-ppb SO₂ environment. The tested trees could tolerate this polluted environment, but it will impact their CO₂ absorption ability. The carbon fixation ability will reduce as the polluted period lengthens. The carbon fixation potential of tested trees ranged from 2.1 to 15.5 g·CO₂/m²·d with an average of 7.7 g·CO₂/m²·d. The changes in CO₂ absorption volume for Messerschmidia argentea were more stable during the fumigation period with a variation of 102%. Among the tested trees, Diospyros morrisiana had the best carbon fixation potential of 9.19 g·CO₂/m²·d and M. argentea had the least with 2.54 g·CO₂/m²·d.