The contribution of ammonia emissions from agriculture to the deposition of acidifying and eutrophying compounds onto forests

In the vicinity of a large ammonia emission area, dry and wet deposition of acidifying and eutrophying compounds onto Douglas Fir forests was studied by sampling throughfall, stemflow and bulk precipitation. Deposition amounts of NH(4)(+) and SO(4)(2-) were recognised to be among the highest of Central Europe, resulting in extremely high inputs of (potential) acid to the forest soils (13.1 kEq ha(-1) year(-1)). The contribution of NH(3) emissions from agriculture to the total acid deposition to the forests was 52%. The total nitrogen deposition amounted to 115.0 kg ha(-1) year(-1), 83% originating from NH(3) emissions and 17% from NO(x) emissions. Calculated mean dry deposition velocities of NH(3) and SO(2) were much larger than reported in the literature. A synergistic effect between NH(3) and SO(2) in the process of dry deposition is suggested and evidence for this effect is discussed. When deposition models do not take this interaction into account, they will underestimate NH(3) and SO(2) deposition amounts in areas with intensive animal husbandry.     

Chemical climatology of high elevation spruce-fir forests in the southern Appalachian mountains

The physical and chemical climatology of high elevation (> 1500 m) spruce-fir forests in the southern Appalachian mountains was studied by establishing a weather and atmospheric chemical observatory at Mt Mitchell State Park in North Carolina (35 degrees 44' 05" N, 82 degrees 17' 15"W). Data collected during the summer and autumn (May-October) of 1986, 1987, and 1988 are reported. All measurements were made on or near a 16.5 m walk-up tower extending 10 m above the forest canopy on Mt Gibbes (2006 m msl), which is located approximately 2 km SW of Mt Mitchell. The tower was equipped with standard meteorological instrumentation, a passive cloud water collector, and gas pollutant sensors for O3, SO2, NOx. The tower and nearby forest canopy were immersed in clouds 25 to 40% of the time. Non-precipitating clouds were very acidic (pH 2.5-4.5). Precipitating clouds were less acidic (pH 3.5-5.5). The dominant wind directions were WNW and ESE. Clouds from the most common wind direction (WNW) were more acidic (mean pH 3.5) than those from the next most common wind direction (ESE, mean pH 5.5). Cloud water acidity was related to the concentration of SO4(2-), and NO3- ions. Mean concentration of H+, NH4+, SO4(2-), and NO3- ions in the cloud water varied from 330-340, 150-200, 190-200 and 120-140 micromol litre(-1) respectively. The average and range of O3 were 50 (25-100) ppbv (109) in 1986, 51 (26-102) ppbv in 1987, and 66 (30-140) during the 1988 field seasons, respectively. The daily maximum, 1-h average, and 24-h average concentrations were all greatest during June through mid-August, suggesting a correlation with the seasonal temperature and solar intensity. Throughfall collectors near the tower were used to obtain a useful estimate of deposition to the forest canopy. Between 50-60% of the total deposition of SO4(2-) was due to cloud impact.     

Effect of vegetation type on throughfall deposition and seepage flux

This paper compares different vegetation types (coniferous and deciduous forest, grassed and pure heathland) in terms of input (throughfall deposition) and output (seepage flux) in a region with intermediate nitrogen load (+/-20kg Nha(-1)y(-1) via bulk precipitation) in comparable conditions in north Belgium. Coniferous forest (two plots Pinus sylvestris and two plots Pinus nigra) received significantly higher nitrogen and sulphur throughfall deposition than deciduous forest and heathland. Grassed and pure heathland had significantly highest throughfall quantities of Ca(2+) and Mg(2+), respectively. The observed differences in throughfall deposition between the different vegetation types were not univocally reflected in the ion seepage flux. Considerable seepage fluxes of NO(3)(-), SO(4)(2-), Ca(2+) and Al(III) were only found under the P. nigra plots. We discuss our hypothesis that the P. nigra forests already evolved to a situation of N saturation, while the other vegetation types did not.     

Wetfall Deposition and Precipitation Chemistry for a Central Appalachian Forest

Abstract

Although extensive research on acidic deposition has been directed toward spruce-fir forests, less research has been done on the impacts of air pollution on eastern montane hardwood forests. The purpose of this study was to describe precipitation chemistry for several Appalachian hardwood forest sites at or near the Fernow Experimental Forest (FEF) to assess the potential for problems associated with acidic deposition. Emphasis was placed on seasonal patterns of ionic concentrations (H+, Ca++, NH4+; NO3-, and SO4=) and spatial variability of ionic concentrations and deposition among sites. Seasonal patterns of most ions showed highest concentrations during the summer months and deposition of H+ was especially pronounced during this time. Deposition of all ions was generally greater (related to greater precipitation) at three montane forested sample sites compared to a nonforested riverbottom site. Precipitation chemistry at FEF was similar to other sites throughout the eastern United States and contrasted sharply with mid-western and western sites. Eastern sites, including means for FEF sites, were uniformly 3-4 times higher in H+ and SO4= concentration than the mid-western and western sites. Precipitation at FEF was chronically acidic, more so during the growing season, and highest at higher elevations where environmental stresses can be most severe. Furthermore, there were occasional large discrepancies between the low-elevation site and the higher-elevation forested sites for precipitation chemistry and acidic deposition. These results suggest that synoptic-scale (network) data may greatly underestimate the pollutant conditions to which highelevation forest trees are exposed, since network data rarely take elevation into account and typically are based on annual ionic concentration and deposition means that may be considerably lower than those of the growing season.     

Short-term effects of gaseous pollutants on cause-specific mortality in Wuhan, China

In Asia, limited studies have been published on the association between daily mortality and gaseous pollutants of nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2). Our previous studies in Wuhan, China, demonstrated long-term air pollution effects. However, no study has been conducted to determine mortality effects of air pollution in this region. This study was to determine the acute mortality effects of the gaseous pollutants in Wuhan, a city with 7.5 million permanent residents during the period from 2000 to 2004. There are approximately 4.5 million residents in Wuhan who live in the city's core area of 201 km2, where air pollution levels are highest, and pollution ranges are wider than the majority of the cities in the published literature. We used the generalized additive model to analyze pollution, mortality, and covariate data. We found consistent NO2 effects on mortality with the strongest effects on the same day. Every 10-microg/m3 increase in NO2 daily concentration on the same day was associated with an increase in nonaccidental (1.43%; 95% confidence interval [CI]: 0.87-1.99%), cardiovascular (1.65%; 95% CI: 0.87-2.45%), stroke (1.49%; 95% CI: 0.56-2.43%), cardiac (1.77%; 95% CI: 0.44-3.12%), respiratory (2.23%; 95% CI: 0.52-3.96%), and cardiopulmonary mortality (1.60%; 95% CI: 0.85-2.35%). These effects were stronger among the elderly than among the young. Formal examination of exposure-response curves suggests no-threshold linear relationships between daily mortality and NO2, where the NO2 concentrations ranged from 19.2 to 127.4 microg/m3. SO2 and O3 were not associated with daily mortality. The exposure-response relationships demonstrated heterogeneity, with some curves showing nonlinear relationships for SO2 and O3. We conclude that there is consistent evidence of acute effects of NO2 on mortality and suggest that a no-threshold linear relationship exists between NO2 and mortality.     

Heterogeneous response of central European streams to decreased acidic atmospheric deposition

We investigated the relations between mountain streamwater chemistry and atmospheric pollution in an arca of 1611 km2 of the Czech Republic by comparing concentrations of SO4. NO3, Cl, Ca and the pH at 432 localities at the time of high (1984-1986) and relatively low (1996-2000) acidic atmospheric deposition. Medians of Cl. SO4, and NO3 decreased by 17, 96 and 60 microeq l(-1), or by 23, 17 and 49%, respectively, during 12 +/- 2 years. The decreased Cl corresponds to decreased emission of industrial Cl (as HCl). The decreased stream SO4 was proportionally lower than the 71% decrease in S-emissions due to leaching of previously accumulated SO4 from soils and non-zero background concentrations. Decreases of NO3 up to 60% in streamwaters with pH < or = 6 was greater than the decrease of N emission in central Europe, about 35%. Extensive regional decrease of NO3 is surprising and is probably described for the first time. The difference in NO3 concentrations between the two periods was probably enhanced by (a) an increase of mineralisation of forest floor in the mid-1980s and (b) by higher uptake of N in the late-1990s. The median pH of the 432 streams did not change but the pH of the sub-population with pH < 6 in the mid-1980s recovered substantially. The pH of circum-neutral streams (pH > 6.5) decreased even as acidic atmospheric deposition decreased.     

Distribution of ozone and other air pollutants in forests of the Carpathian Mountains in central Europe.

Ozone (O3) concentrations were monitored during the 1997-1999 growing seasons in 32 forest sites of the Carpathian Mountains. At all sites (elevation between 450 and 1320 m) concentrations of O3, nitrogen dioxide (NO2), and sulfur dioxide (SO2) were measured with passive samplers. In addition, in two western Carpathian locations, Vychodna and Gubalówka, ozone was continuously monitored with ultraviolet (UV) absorption monitors. Highest average hourly O3 concentrations in the Vychodna and Guba?ówka sites reached 160 and 200 microg/m3 (82 and 102 ppb), respectively (except for the AOT40 values, ozone concentrations are presented as microg/m3; and at 25 degrees C and 760 mm Hg, 1 microg O3/m3 = 0.51 ppb O3). These sites showed drastically different patterns of diurnal 03 distribution, one with clearly defined peaks in the afternoon and lowest values in the morning, the other with flat patterns during the entire 24-h period. On two elevational transects, no effect of elevation on O3 levels was seen on the first one, while on the other a significant increase of O3 levels with elevation occurred. Concentrations of O3 determined with passive samplers were significantly different between individual monitoring years, monitoring periods, and geographic location of the monitoring sites. Results of passive sampler monitoring showed that high O3 concentrations could be expected in many parts of the Carpathian range, especially in its western part, but also in the eastern and southern ranges. More than four-fold denser network of monitoring sites is required for reliable estimates of O3 distribution in forests over the entire Carpathian range (140 points). Potential phytotoxic effects of O3 on forest trees and understory vegetation are expected on almost the entire territory of the Carpathian Mountains. This assumption is based on estimates of the AOT40 indices for forest trees and natural vegetation. Concentrations of NO2 and SO2 in the entire Carpathian range were typical for this part of Europe and below the expected levels of phytotoxicity.     

Fluxes of ions in precipitation, throughfall and stemflow in an urban forest in Kuala Lumpur, Malaysia

A study was carried out to determine the chemical composition of bulk precipitation, throughfall and stemflow in an urban forest in Kuala Lumpur, Malaysia. The mean weekly rainfall recorded during the period of study was 63.2 mm. Throughfall, stemflow and canopy interception of incident precipitation were 77.1%, 1.2% and 21.7% respectively. Bulk precipitation, througfall and stemflow were acidic, the pH recorded being 4.37, 4.71 and 4.15 respectively. In all cases the dominant ions were NO3, SO4, Cl, NH4, K, Ca and Na. Of the ions studied Ca, K, Cl, SO4, Mg and Mn showed net increases in passing through the forest canopy, while NH4, Na, NO3, Zn, H and Fe showed net retention. This study shows that the urban environment of Kuala Lumpur contributes considerable amounts of materials to the atmosphere, as reflected by the high ionic contents in bulk precipitation, throughfall and stemflow.     

Relation between estimated dry deposition and throughfall in a coniferous forest exposed to controlled levels of SO2 and NO2

Throughfall was collected in a Scots pine forest exposed to about 14 microg m(-3) of both SO2 and NO2, and in a control forest with 1 microg m(-3) SO2 and < 1 microg m(-3) NO2. Precipitation was collected in a nearby open field. Collection was performed on an event basis during the whole vegetation period. Exposure was made by an open-air release system during the vegetation period, except during rain and at night. Additional sulfate deposition in the exposed forest (compared to control forest) was nearly equal to dry deposition of sulfur dioxide, as estimated with a stomatal conductance model adapted for the particular forest. It is thus concluded that essentially all of the dry deposited sulfur dioxide is eventually extracted and appears in throughfall-including the fraction that has been deposited through stomata. Attempts to relate net throughfall deposition to dry deposition of sulfate in the control forest were inconclusive, since a minor (10%) uncertainty in the water balance had a major influence on calculated deposition velocity for particulate sulfate. Nitrate throughfall deposition is about half of the open field wet deposition, both for the exposed and control forest. Thus, a long-term exposure with about 14 microg m(-3) NO2 decreased nitrate throughfall deposition.     

Multivariate space analysis of the major precipitation ions over Europe, 1986-1997

The annual average concentrations (1986-1997) of the major ions SO4(2-), NO3-, Cl-, NH4+, Na+, Mg2+, Ca2+, and K+ in precipitation are analyzed for selected EMEP stations. The objective is to determine the ion patterns or typologies in precipitation by principal component analysis (PCA) combined with a cluster analysis. SO4(2-) and NO3- ions are predominant in central and eastern Europe. This area corresponds to high emissions of SO2 and NO2. Sea spray ions are predominant in coastal sites. The soil components show an important contribution in southern Europe, possibly due to the soil dust transported from northern Africa.     

Meteorological factors and air pollution in Lithuanian forests: possible effects on tree condition

This study investigates changes in tree condition and environmental factors in Lithuania during the active growing season in 1991-2001. The average crown defoliation and the proportion of healthy trees of Pinus sylvestris, Picea abies, Betula sp., Fraxinus excelsior, Alnus incana, Alnus glutinosa, Populus tremula, and Quercus robur, meteorological (average temperature, amount of precipitation, hydrothermal coefficient) and air pollution data (acidity of precipitation, concentrations of SO2, NO2 and exposure of O3) were analysed. During the period 1991-2001 the condition of Pinus sylvestris, Populus tremula showed a tendency of improvement, while defoliation of Fraxinus excelsior significantly increased. The proportion of healthy trees correlated well with the average temperature and O3 (AOT40), while defoliation correlated well with the acidity of precipitation and the concentrations of SO2 and NO2. Deciduous species appeared to be more sensitive to O3 exposure and conifers to the concentrations of SO2 and NO2.     

Carbon storage and sequestration by urban trees in the USA

Based on field data from 10 USA cities and national urban tree cover data, it is estimated that urban trees in the coterminous USA currently store 700 million tonnes of carbon ($14,300 million value) with a gross carbon sequestration rate of 22.8 million tC/yr ($460 million/year). Carbon storage within cities ranges from 1.2 million tC in New York, NY, to 19,300 tC in Jersey City, NJ. Regions with the greatest proportion of urban land are the Northeast (8.5%) and the southeast (7.1%). Urban forests in the north central, northeast, south central and southeast regions of the USA store and sequester the most carbon, with average carbon storage per hectare greatest in southeast, north central, northeast and Pacific northwest regions, respectively. The national average urban forest carbon storage density is 25.1 tC/ha, compared with 53.5 tC/ha in forest stands. These data can be used to help assess the actual and potential role of urban forests in reducing atmospheric carbon dioxide, a dominant greenhouse gas.     

Hydrogen behaviour and ion concentrations in precipitation of Europe and the United States

Hydrogen ions in precipitation vary primarily with (SO4 + NO3) concentration. However the slope of the H: (SO4 + NO3) relation for high concentrations (0.60 and 0.61) is twice that at low concentrations (0.32 and 0.22) in European and US samples respectively. Sulphuric and nitric acid dominate precipitation in the US. Precipitation in Europe, although nearly equally acid, is dominated by NH4+, Ca2+, and Mg2+ salts at total ionic concentrations 2 and 3 times higher. Ion concentrations in precipitation, other than H, are proportional to their respective emission fluxes.     

Simulated seasonal variations in wet acid depositions over East Asia

The air quality modeling system Regional Atmospheric Modeling System-Community Multi-scale Air Quality (RAMS-CMAQ) was applied to analyze temporospatial variations in wet acid deposition over East Asia in 2005, and model results obtained on a monthly basis were evaluated against extensive observations, including precipitation amounts at 704 stations and SO4(2-), NO3-, and NH4+ concentrations in the atmosphere and rainwater at 18 EANET (the Acid Deposition Monitoring Network in East Asia) stations. The comparison shows that the modeling system can reasonably reproduce seasonal precipitation patterns, especially the extensive area of dry conditions in northeast China and north China and the major precipitation zones. For ambient concentrations and wet depositions, the simulated results are in reasonable agreement (within a factor of 2) with observations in most cases, and the major observed features are mostly well reproduced. The analysis of modeled wet deposition distributions indicates that East Asia experiences noticeable variations in its wet deposition patterns throughout the year. In winter, southern China and the coastal areas of the Japan Sea report higher S04(2-) and NO3- wet depositions. In spring, elevated SO4(2-) and NO3-wet depositions are found in northeastern China, southern China, and around the Yangtze River. In summer, a remarkable rise in precipitation in northeastern China, the valleys of the Huaihe and Yangtze rivers, Korea, and Japan leads to a noticeable increase in SO4(2-) and NO3- wet depositions, whereas in autumn, higher SO4(2-) and NO3-wet depositions are found around Sichuan Province. Meanwhile, due to the high emission of SO2, high wet depositions of SO4(2-) are found throughout the entire year in the area surrounding Sichuan Province. There is a tendency toward decreasing NO3- concentrations in rainwater from China through Korea to Japan in both observed and simulated results, which is a consequence of the influence of the continental outflow from Eurasia. The same tendency is not found for SO4(2-).     

Assessment of environmental impact zones in the Kola Peninsula forest ecosystems

This paper describes the condition of forest ecosystems subjected to smelter pollution in the Kola peninsula. This assessment is based on the parameters of the biogeochemical cycle. The defoliation index was used to delimit three basic forest states: background, defoliating, sparse. Close to the smelter, due to expansion of the area not covered by vegetation, a fourth type of state, so-called "industrial deserts", has been observed. The concentrations of sulphur, copper and nickel in the precipitation in the forests generally declined with distance from the smelter. The defoliating forests are noted for the highest Ca, Mg, K concentrations in the summer precipitation. In sparse forests and industrial deserts a decrease in the Ca, Mg, K concentrations in the summer precipitation in comparison with the defoliating forests, despite the particle emissions, could be attributed to the reduction in forest biomass. The higher levels of soil and soil leachate carbon and acidity in the defoliating forests was due to higher litterfall and to the higher dissolution of fulvic acids by the acidic precipitation. This increase in organic matter levels affects soil cation exchange capacity and cation saturation. The pine trees demonstrated significant changes in the uptake of elements in all types of forests under pollution. Elevated levels of S, Ni, Cu and K and reduced levels of Mg, Mn and Zn were found in the needles of different age classes.     

Effect of climate change on fluxes of nitrogen from the Tovdal River basin, Norway, to adjoining marine areas

The mass transport model TEOTIL was used to project nitrate (NO3) fluxes from the Tovdal River basin, southernmost Norway, given four scenarios of climate change. Forests, uplands, and open water currently account for 90% of the NO3 flux. Climate scenarios for 2071-2100 suggest increased temperature by 2-4 degrees C and precipitation by 3-11%. Climate experiments and long-term monitoring were used to estimate future rates of nitrogen (N) leaching. More water will run through the terrestrial catchments during the winter but less will run in the spring. The annual NO3 flux from the Tovdal River to the adjoining Topdalsfjord is projected to remain unchanged, but with more NO3 delivered in the winter and less in the spring. Algal blooms in coastal waters can be expected to occur earlier in the year. Major sources of uncertainty are in the long-term fate of N stored in soil organic matter and the impacts of forest management.     

Development of the high spatial resolution EMICAT2000 emission model for air pollutants from the north-eastern Iberian Peninsula (Catalonia, Spain)

Ozone (O(3)) pollution episodes take place in Catalonia (NE of the Iberian Peninsula), mainly during summertime. The complex O(3) behaviour could be understood by using a Chemical Transport Model (CTM). Emission inventories provide the spatial and temporal emissions distribution of the O(3) precursors and other pollutants required by this approach. We developed the EMICAT2000 model with high spatial (cells of 1 km(2)) and temporal (1h) resolutions, to estimate the emissions during the year 2000 from Catalonia. Total annual emissions were 107 kt yr(-1) of NO(x), 137 kt yr(-1) of NMVOC, 267 kt yr(-1) of CO, 65 kt yr(-1) of SO(2), 24 kt yr(-1) of TSP and 32,175 kt yr(-1) of equivalent CO(2). Main NO(x) sources are on-road traffic (58%) and industries (38%). Main NMVOC sources are on-road traffic (36%), vegetation (34%) and use of solvents (13%). Speciation was established according to the Carbon Bond IV mechanism. EMICAT2000 generates directly the data files required for the third generation CTM Models-3/CMAQ.     

Response of needle sulphur and nitrogen concentrations of Scots pine versus Norway spruce to SO2 and NO2

The results of two field studies and an open-top chamber fumigation experiment showed that the response of mature Scots pine to SO(2) and NO(2) differed from that of mature Norway spruce. Moreover, the response of pine seedlings to SO(2) and NO(2) differed from that of mature trees. The greater increase in the needle total S concentrations of pine suggested more abundant stomatal uptake of SO(2) compared to spruce. Both pine seedlings and mature trees also seemed to absorb more N from atmospheric deposition. Mature pine was able to assimilate SO(4)(2-) derived from SO(2) into organic S more effectively than mature spruce at the high S and N deposition sites, whereas both pine and spruce seedlings accumulated SO(4)-S under NO(2)+SO(2) exposure. Spruce, in turn, accumulated SO(4)-S even when well supplied with N. Net assimilation of SO(4)(2-) in conifer seedlings was enhanced markedly by elevated temperature. To protect the northern coniferous forests against the harmful effects of S and N deposition, it is recommended that the critical level for SO(2) as a growing season mean be set at 5-10 microg m(-3) and NO(2) at 10-15 microg m(-3), depending on the 'effective temperature sum' and/or whether SO(2) and NO(2) occur alone or in combination.     

Source identification of atlanta aerosol by positive matrix factorization

Data characterizing daily integrated particulate matter (PM) samples collected at the Jefferson Street monitoring site in Atlanta, GA, were analyzed through the application of a bilinear positive matrix factorization (PMF) model. A total of 662 samples and 26 variables were used for fine particle (particles < or = 2.5 microm in aerodynamic diameter) samples (PM2.5), and 685 samples and 15 variables were used for coarse particle (particles between 2.5 and 10 microm in aerodynamic diameter) samples (PM10-2.5). Measured PM mass concentrations and compositional data were used as independent variables. To obtain the quantitative contributions for each source, the factors were normalized using PMF-apportioned mass concentrations. For fine particle data, eight sources were identified: SO4(2-) -rich secondary aerosol (56%), motor vehicle (22%), wood smoke (11%), NO(3-) -rich secondary aerosol (7%), mixed source of cement kiln and organic carbon (OC) (2%), airborne soil (1%), metal recycling facility (0.5%), and mixed source of bus station and metal processing (0.3%). The SO4(2-) -rich and NO(3-) -rich secondary aerosols were associated with NH(4+). The SO4(2-) -rich secondary aerosols also included OC. For the coarse particle data, five sources contributed to the observed mass: airborne soil (60%), NO(3-)-rich secondary aerosol (16%), SO4(2-) -rich secondary aerosol (12%), cement kiln (11%), and metal recycling facility (1%). Conditional probability functions were computed using surface wind data and identified mass contributions from each source. The results of this analysis agreed well with the locations of known local point sources.     

Atmospheric deposition to the edge of a spruce forest in Denmark

Atmospheric deposition was measured during 1 year at the forest edge of a Norway spruce stand in Denmark. Inside the forest the deposition of H(+), Ca(2+), Mg(2+), Na(+), K(+), Cl(-), NO(3)(-), NH(4)(2) and SO(4)(2-) with canopy throughfall varies with the distance from the forest edge. The deposition at the edge is found to be 10-20 times as high as deposition to an open field and 2-8 times as high as deposition inside the stand. An exponential decrease in deposition as a function of the distance from the forest edge is found. Increased deposition of K(+) and non-sea salt Mg(2+), which mainly originates as a result of leaching from the needles may be explained by a larger leaf area index (LAI) at the forest edge. Deposition of particulate substances, especially Na(+), Cl(-), Mg(2+) and to some extent SO(4)(2-), NH(4)(+) and NO(3)(-) is increased much more than the LAI, which we believe to be caused by changes in wind movements at the forest edge.