Atmospheric Deposition of Acidifying and Eutrophicating Substances in Dune Slacks

Water, Air, &; Soil Pollution - The atmospheric input of nitrogen and potantial acid, and the composition of the leachate from the topsoil layer are quantified for eight dune slack sites...     

Long-Term Evaluation of Acidic Atmospheric Deposition on Soils and Soil Solution Chemistry in the Daniel Boone National Forest,USA

Combustion of fossil fuels has contributed to many environmental problems including acid deposition. The Clean Air Act (CAA) was created to reduce ecological problems by cutting emissions of sulfur and nitrogen. Reduced emissions and rainfall concentrations of acidic ions have been observed since the enactment of the CAA, but soils continue to receive some acid inputs. Many soils sensitive to acid deposition are found to have low pH, a loss of base cations, and a shift in the mineral phase controlling the activity of Al³⁺ and/or SO₄ ^2?. If inputs continue, soil may be depleted of base cations and saturated with Al and could cause low forest productivity. Soil samples and soil solutions from pan lysimeters were taken on ridge-tops in the Daniel Boone National Forest to evaluate potential impacts of acid deposition recently and in the future. Sample results were compared to historical data from identical locations. Physicochemical characteristics of the soils revealed that sites were very low in base saturation and pH and high in exchangeable acidity, illustrating change since previously sampled. Soil solution data indicated that sites periodically received high acid inputs leading to saturation of Al in soils and the formation of Al-hydroxy-sulfate minerals. Given these conditions, long-term changes in soil chemistry from acid deposition are acknowledged.     

Effects of Atmospheric Sea-Salt Deposition on Soils and Freshwaters in Northeast Scotland

The majority of Scottish upland soils are particularly sensitive to acid deposition because of their low weathering rates. The compositions of the exchangeable base cations of such soils in the United Kingdom are dominated by sea salt inputs rather than by mineral weathering inputs of base cations. Catchments with low mineral weathering rates are also those particularly susceptible to freshwater acidification. Therefore, catchments exhibiting a high sea salt effect should also exhibit the most acid waters under base flow and storm flow conditions. A field evaluation study based on 61 catchments in NE Scotland has shown that this is indeed the case. River water pH under both base flow and high flow conditions is correlated stronhly with the relative contribution of Na+ to the sum of Ca2+, Mg2+ and Na+. From these results, an attempt is being made to produce a quantitative signature of weathering for the soils within the catchment upstream of the sampling point. Representative soil samples from the LFH, AE, B and C horizons and on 4 different parent materials have been obtained from the surrounding catchments to validate the above results for associated soil solutions. Sampling took place on upland moorland podzols under Calluna vulgaris. Tension lysimeters were used to sample the soil solutions so that their chemistry could be compared with that of the relevant river water.     

The Impact of Nitrogen on Forest Soils and Feedbacks on tree Growth

The effects of pollutant nitrogen on forest soils and the potential feedbacks on tree growth are discussed using data from recent plot and catchment manipulation studies. Results indicate that N applied to the soil affects both soil N transformations and base cation status in some forest soils. Whilst reductions in tree growth are infrequently reported, a greater understanding of the effect of increased N deposition on soil N transformations, and associated changes in soil acidification and nutritional balance, is essential if sensitive stands are to identified. In particular, the factors controlling soil N accumulation rates and thus the onset of nitrate leaching are not clearly understood with increased nitrogen availability potentially increasing nitrogen accumulation due to abiotic fixation and lignolytic enzyme suppression, whilst the onset of nitrification as the C/N ratio of forest floor material declines, may reduce N retention efficiency. The switch from increased to decreased tree growth rate in response to N additions in some experiments highlights the need for long-term studies as a necessary component of future research.     

The Impact of Artificial Forest Plantations on Mountain-Meadow Soils of Crimea

A significant change in the properties of mountainous meadow soils of the Ai-Petri Plateau has taken place under the impact of artificial plantations of pine, birch, and larch created in the Crimean highlands in the middle of the 20th century. In comparison with the soils under meadow vegetation, the soils under forest vegetation are characterized by an increased content of large aggregates, a decrease in the humus content, and an increase in the soil acidity and in the iron content of the organomineral compounds. The most dramatic changes in the structural state of the soils are observed under the plantations of pine. The changes in the acidity and the iron content are most pronounced under larch stands. The decrease in the humus content is observed under all tree species. Thus, in the soil layer of 0–10 cm under pine, birch, and larch stands, the content of C_org is 1.2, 1.3, and 1.4 times lower, respectively, than that in the soil under meadow vegetation.     

Atmospheric Nitrogen Deposition and the Properties of Soils in Forests of Vologda Region

Twenty plots (20 m² each) were selected in coniferous and mixed forests of the industrial Vologda district and the Vytegra district without developed industries in Vologda region. In March, snow cores corresponding to the snow cover depth were taken on these plots. In August, soil samples from the 0- to 20-cm layer of litter-free soddy-podzolic soil (Albic Retisol (Ochric)) were taken on the same plots in August. The content of mineral nitrogen (N_min), including its ammonium (NH⁺₄) and nitrate (NO^-₃) forms, was determined in the snow (meltwater) and soil. The contents of total organic carbon, total nitrogen, and elements (Al, Ca); pH; particle size distribution; and microbiological parameters―carbon of microbial biomass (C_mic) and microbial respiration (MR)―were determined in the soil. The ratio MR/C_mic = qCO₂ (specific respiration of microbial biomass, or soil microbial metabolic quotient) was calculated. The content of N_mic in meltwater of two districts was 1.7 mg/L on the average (1.5 and 0.3 mg/L for the NH⁺₄ and NO^–₃ forms, respectively). The annual atmospheric deposition was 0.6–8.9 kg N_min/ha, the value of which in the Vologda district was higher than in the Vytegra district by 40%. Reliable correlations were found between atmospheric NH⁺₄ depositions and C_mic (–0.45), between NH⁺₄ and qCO₂ (0.56), between atmospheric NO^-₃ depositions and the soil NO^-₃ (–0.45), and between NO^-₃ and qCO₂ (–0.58). The content of atmospheric N_min depositions correlated with the ratios C/N (–0.46) and Al/Ca (–0.52) in the soil. In forests with the high input of atmospheric nitrogen (>2.0 kg NH⁺₄/(ha yr) and >6.4 kg N_min/(ha yr)), a tendency of decreasing C_mic, C/N, and Al/Ca, as well as increasing qCO₂, was revealed, which could be indicative of deterioration in the functioning of microbial community and the chemical properties of the soil.     

典型森林树种对大气颗粒物湿沉降的影响

选择典型森林树种油松和侧柏作为研究对象,通过在2种树的冠层不同高度处(8,6,4,2m)布设湿沉降监测装置进行定位监测,比较单位叶面积滞尘量和降水对叶表面颗粒物冲刷率来分析2种树种对于大气颗粒物湿沉降的影响,并分析了树冠层不同高度颗粒物湿沉降以及不同粒径颗粒物湿沉降通量的变化规律,最后通过叶片显微结构来分析2种树种滞尘差异的原因。结果表明:(1)油松单位叶面积的滞尘量高于栓皮栎;降雨对2种树种叶面上大气颗粒物的冲刷率表现为栓皮栎高于油松。(2)油松枝下高2m处滞尘能力最强,大气颗粒物湿沉降通量最小;栓皮栎树冠中部4m处滞尘能力最强,且湿沉降通量最小。(3)油松冠层下部对于10~100μm污染物具有明显的截留作用,而栓皮栎的树冠上部对其具有更明显的截留作用。对于0.4~3μm和3~10μm颗粒物,油松的截留能力要强于栓皮栎。(4)油松和栓皮栎在叶表面显微结构的差异导致两者吸附颗粒物能力不同,油松叶片具有更多的褶皱、开度和密度较高的气孔以及相对较深的沟槽使其具有更强的吸附颗粒物的能力。     

Determination of Atmospheric Mercury During the North Sea Experiment

Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea Experiment, September 1991. On the F.S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng·m-3 with an average of 1.5 ng·m-3 and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng·m-3 with an average of 1.2 ng·m-3. An average 20% decrease is observed from the up-wind to the downwind ship, which may largely be affected by entrainment into the free troposphere. An overall removal was 0.5 cm·s-1 for dry periods and varied between 1 to 5 cm·s-1 during rain events. Rainwater concentrations varied between 5 and 25 ng·l-1. Based on these data an annual wet deposition flux of 1.08 ng Hg cm-2 yr1- was estimated for the North Sea.     

模拟氮沉降对森林土壤酚类物质和可溶性糖含量的影响

采用野外原位试验模拟氮沉降,研究其对福建建瓯万木林自然保护区杉木林(CUL)、浙江桂(CIC)和罗浮栲林(CAF)3种林分土壤多酚、单宁和可溶性糖含量的影响。每个林分设置对照(CK,0 kg/(hm2·a))、低氮(LN,30 kg/(hm2·a))和高氮(HN,100 kg/(hm2·a))3个处理。结果表明:针叶杉木林土壤多酚含量最高,单宁和可溶性糖含量最低,且均与另两个阔叶树种林分差异显著。杉木和罗浮栲林土壤多酚含量随着氮添加量的增加而显著降低,浙江桂多酚受HN处理影响不大,仅LN处理显著降低49.4%。氮沉降主要表现为降低土壤单宁含量,LN处理分别显著降低杉木林、浙江桂和罗浮栲林单宁含量43.5%、70.0%和79.5%;而HN处理仅降低阔叶林土壤单宁含量。然而,氮沉降增加土壤可溶性糖含量,与对照处理相比,LN处理分别显著增加杉木、浙江桂和罗浮栲林土壤可溶性糖48.8%、19.2%和19.8%。各林分凋落物中多酚、单宁和可溶性糖含量受氮沉降的影响不显著。     

The Contribution to Nitrogen Deposition and Ozone Formation in South Norway from Atmospheric Emissions Related to the Petroleum Activity in the North Sea

A photochemical puff-trajectory model (Fotoplume) has been applied to simulate emissions, atmospheric transport and chemical transformations of pollutants from offshore oil and gas production in the North Sea. The above model was used in conjunction with the European Monitoring and Evaluation Programme (EMEP) regional Lagrangian oxidant model. The Fotoplume and EMEP models were used to evaluate the effects of the atmospheric emissions from the oil and gas exploration activity in the Norwegian sector of the North Sea. Deposition of nitrogen and formation of boundary level ozone in Southern Norway due to North Sea emissions of nitrogen oxides (NO_x), carbon monoxide (CO) and volatile organic compounds (VOC) have been studied. The petroleum activity in the North Sea is calculated to contribute approximately 20% of the nitrogen deposition in the coastal areas of Norway in 1992. In addition, the models were used to estimate the AOT40 ozone exposure levels. The results indicate that emissions from British and Norwegian oil and gas exploitation sector separately contribute to less than 5% each of the AOT40 values for coniferous forests and meadows. Comparison of model calculations with experimental measurements is quite satisfactory and the models show realistic results for both the nitrogen deposition and AOT40 values.     

The Effect of N Deposition on Nitrous Oxide and Nitric Oxide Emissions from Temperate Forest Soils

Long-term and short-term N deposition effects on N₂O and NO emissions from forest soils were compared. Long-term NH₃ deposition (> 20 years) from a poultry farm to a downwind woodland (decreasing from 73 to 18 kg N ha^-1 y^-1, 30 to 110 m downwind of the farm) resulted in the re-emission of 6% and 14% of NH₃-N deposited as N₂O-N and NO-N, respectively. However, when in short-term (2-3 years) field experiments the atmospheric N deposition to mature conifer plantations was raised by fumigation with NH₃ to 15 kg N ha^-1 y^-1 or by acid mist to 48 and 96 kg N ha^-1 y^-1 the N deposited was immobilised. In the acid mist experiment more than 2 years of acid mist (48 and 96 kg N ha-1 y^-1) were required to significantly increase N₂O emissions from -0.3 μg N₂O-N m^-2 h^-1 (control) to 0.5 and 5.7 μg N₂O-N m^-2 h^-1, respectively. This suggests, that N deposition simulation studies in soil ecosystems, which have previously not been exposed to high rates of N (by deposition or fertilisation), need to be long-term. Also, measurements of N₂O and/or NO may be a non-destructive, quick indicator of the N status of the soil.     

Atmospheric Deposition of Acidifying Components to a Japanese Cedar Forest

One-year field measurements were conducted in a Japanese cedar (Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of the meteorological and atmospheric concentration data, the dry deposition of SO₂, HNO₃, NO₂ and HCl was estimated using the inferential method. The annual dry deposition of H⁺ was estimated at 721 eq ha^?1yr^?1, which was 40% larger than the measured annual wet deposition of H⁺ (514 eq ha^?1yr^?1). Therefore, dry deposition is an important pathway for the atmospheric input of H⁺ to the forest in the study site. The contribution of each gas to the dry deposition of H⁺ was as follows: SO₂, 25%; HNO₃, 32%; NO₂, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H⁺ was taken up by the canopy.     

Input of Atmospheric Particles into Forest Stands by Dry Deposition

In this study the dry input of atmospheric particles into a forest stand is quantified. A wash-off-method using the natural leaf surfaces as collectors of the dry deposition was chosen. The direct on-site-measurement on living branches were achieved in a spruce stand (Picea abies (L.) Karst) at Solling, Germany. The ion exchange processes occurring on natural branches can reliably be quantified through immediate sequential washings. In order to calculate also the gas dry deposition of those trace elements which occur in both particle and gas phases, a resistance model was used. From these results the deposition velocity of particulate aerosol components into the forest stand was calculated. Dry particle deposition constitutes an important part of the total matter input into the forest ecosystem. Just the nitrogen input into Solling only by dry deposition (from particle-, mist-, and gas-deposition) with about 30 kg N ha^?1 a^?1 already exceeds the critical load of 20 kg N ha^?1 a^?1 by far, and this is without even considering the additional load by wet deposition which amounts to 15 kg ha^?1 a^?1. These findings are of greatest ecological importance, as the damage to the stability of the forest ecosystem caused by increased nitrogen input is considerable. Only a quick and drastic reduction of sulphur and nitrogen emissions could stop the further increase of the nutritient imbalance and the progressing acidification of this ecosystem.     

大气沉降对土壤和作物中重金属富集的影响及其研究进展

以我国农田土壤-作物-大气系统为研究对象,综述了近年来大气沉降中重金属的来源及时空分布规律以及大气沉降对农田土壤和作物中重金属富集的影响及其研究进展。人为活动产生的重金属进入大气后,受多种自然和人为因素及环境保护政策等综合因素的影响,导致大气沉降中的重金属具有明显的时空分异特征:从时间分异来看,大气重金属含量呈现出冬季高于其他季节,供暖期高于非供暖期的特点;从空间分异来看,工业发达地区较高,燃煤为主的城市高于其他城市,城区高于郊区及远郊地区。大气沉降不仅会使土壤重金属含量上升,也会对农作物造成直接和间接的影响。大气中的重金属会通过气孔进入作物细胞,在细胞壁、液泡中积累,当含量过高时会影响作物正常生长或引起作物重金属超标风险,不利于农业安全生产。未来的研究应将传统分析方法与空间和地统计技术、多元同位素示踪技术、数学模型模拟等多种技术手段相结合,在区域尺度和田间自然条件下开展土壤-作物-大气系统重金属循环过程的研究,为区域农田重金属污染防控和环境管理提供科学依据和决策支撑。     

Effects of Acid Deposition on Forest Soils in Northernmost Russia: Modelled and Field Data

In addition to strong natural stresses forest ecosystems in the Kola Subarctic, Russia, receive high loads of sulphur and heavy metals from the nickel smelter. To estimate soil response to acid deposition we compared the soil field data along a pollution gradient and simulated time effects. Multivariate technique was applied to investigate spatial distribution of soil field data. Time response of soils to acid deposition was evaluated with the SMART model. According to field observations there is no evidence for strong soil acidification effects close to the smelter. Concentrations of exchangeable Ca and base saturation increase, while acidity decrease in lower soil mineral horizons towards the pollution source. However, some features seem to reflect the early stages of the started acidification. Most soil profiles have low pH values. Despite increasing of exchangeable Ca and Mg towards the smelter in lower mineral horizons due to geological inheritance, they do not reveal the same trends in the upper ones. Concentration of exchangeable K in organic horizons decreases towards the smelter, thus confirming the starting acidification. As result, exchangeable base cations are depleted in the considerable part of shallow soil profiles. According to model simulation the present acid load does not effect considerably on forest soils in background areas, however, dramatic shift in soil chemistry near the smelter is expected within several decades. Due to low pool of exchangeable base cations and low weathering rate continued acid deposition can lead to increased soil acidification and nutrient imbalance.     

Paramagnetic Properties of Humic Substances in Taiga and Tundra Soils of the European Northeast of Russia

The study of paramagnetic activity of humic substances in taiga and tundra soils of the Komi Republic and the assessment of the influence of soil hydromorphism on concentrations of free radicals in the structure of humic acids (HAs) and fulvic acids (FAs) have been performed. The concentration of free radicals in HA specimens was up to 11 times higher than that in FA specimens due to a higher content of aromatic and other condensed structures in HA molecules. This fact attests to the high capacity of HAs to polymerization and complexation reactions with participation of radicals. The average value of g-factor is higher for FA specimens than for HA specimens, which attests to a greater electron density shift of unpaired electron to oxygen atom in the structure of FAs because of its spin-orbital interaction with oxygen-containing functional groups, the concentrations of which are significantly higher in FAs than in HAs. An increase in the concentration of free radicals in the molecular structure of HAs is observed in taiga soils with an increase in the degree of their hydromorphism (from automorphic to semihydromorphic soils), which is related to the biohydrothermal conditions of humus formation in bog-podzolic soils with retarded biochemical processes and low degree of plant litter humification. As a result, HAs with the high content of free radicals in their structure are formed. An opposite situation is observed for HAs in tundra soils with a decrease in the content of unpaired electrons under conditions of the increased hydromorphism. The difference in the character of changes in the paramagnetic activity of HAs in taiga and tundra soils with different degrees of hydromorphism may be related to different natures of plant residues participating in humification processes. A tendency for a decrease in the paramagnetic activity in both HAs and FAs from the south to the north is observed, which may be related to a general decrease in the content of poly-conjugated systems in the structure of humic substances in tundra soils.     

Use of the O Horizon of Forest Soils in Monitoring Metal Deposition in Latvia

The concentrations of Cu, Cd, Pb, Zn, V,Ni, Cr, Fe Ca, Mg and K were determined in the organicsoil layer (O horizon) of pine forests in Latvia. Theconcentrations were expressed on a mass, volume andsurface area basis. When concentrations were calculatedper unit mass of the O horizon, significant positivecorrelations between concentrations in the O horizon andPleurozium schreberi were achieved for mostelements (excepting Cr, Ca and K), and to lesser degreesfor Cu, Pb, Zn, V, Ni and Fe when calculated on a volumeor area basis. Non-rotated principal components analysisidentified a major soil factor related to bulk density(volume- and area-based concentrations). The main groupsof related elements defined by varimax-rotated PCAcomponents were similar for the mass- and volume-baseddata, and regions with elevated levels of these elementscould be related to local pollution sources, similar tothe patterns previously reported from surveys based onmoss.     

Modelling Impacts of Atmospheric Deposition,Nutrient Cycling and Soil Weathering on the Sustainability of Nine Forest Ecosystems

To assess the impact of acid deposition on the long-term sustainability of nine oak, pine and spruce stands on sandy to loamy sandy parent material in Sweden, Denmark and The Netherlands, a dynamic soil acidification model (ReSAM) was applied. Two deposition scenarios for the period 1990–2090 were used: a business as usual scenario (BAU) and a restrictive critical load scenario (CL). The BAU scenario leads to a strong decrease in both Al concentrations and pH in the topsoil of the Dutch and the Danish sites due to a decrease in the amount of amorphous Al compounds. The decline in pH leads to an enhanced release of base cations by silicate weathering. Despite the ongoing acidification, base saturation increases during the simulation period, due to both the increase in base cation weathering and an increased input from mineralization with the ageing of the tree stands. No change in Al concentration is predicted for northern Sweden as deposition levels are below critical loads. Soil chemistry at the recently replanted Swedish sites is dominated by changes in N cycling instead of by deposition. The CL scenario leads, especially after 2010, to a stronger decline in Al concentration compared with the BAU scenario, which is mainly caused by a reduction of the acid input. Up to 2010, a considerable acid input to the soil system is maintained as N supply is larger than the consumption of N by the trees. Despite the reduction of the deposition of S and N to critical loads, the readily available cation pools are still declining on the Danish and Dutch sites in 2090. It is concluded that deposition levels above critical loads lead to exhaustion of the pool of amorphous Al compounds and a decline in pH. Base saturation does not decline due to an increase in mineralization with stand age and an increase in weathering rate due to the decline in pH.     

Forest Floor Quality and N Transformations in a Temperate Forest Affected by Avian-Derived N Deposition

To evaluate the effects of avian-derived N deposition on forest C and N status, we investigated quantity and quality of litterfall, and chemical quality and N transformations in the forest floor from five sites that had been exposed to waterbird breeding colonies to differing degrees. The highest litterfall input of 2.6 t ha^?1 month^?1 was observed in the forest stand (Site 2) where intense bird breeding activity had been observed. Litterfall C/N was highest at the control site (no breeding activity) and decreased as the colonization stages advanced. Nitrogen concentration in litterfall and the forest floor was higher at those sites (Sites 3 and 4) where bird breeding had ceased and which represented the 'post-colony' situation, and consequently C/N and lignin/N of forest floor decreased. NH₄-N pool size in the forest floor was higher at Site 2, probably due to ongoing input and mineralization of bird excreta. Nitrification rate and percent nitrification were highest at Sites 3 and 4. From these results we conclude that study sites exposed to bird colonies show signs of N excess even after colonies are abandoned.