Deposition and Critical Loads of Nitrogen in Switzerland

Many ecosystems in Switzerland suffer from eutrophication due to increased atmospheric nitrogen (N) input. In order to get an overview of the problem, critical loads for nutrient N were mapped with a resolution of 1×1 km applying two methods recommended by the UN/ECE: the steady state mass balance method for productive forests, and the empirical method for semi-natural vegetation, such as natural forests, (sub-)alpine or species-rich grassland and raised bogs. The national forest inventory and a detailed atlas of vegetation types were used to identify the areas sensitive to N input. The total N input was calculated as the sum of NO₃ ^?, NH₄ ⁺, NH₃, NO₂ and HNO₃ wet and dry deposition. Wet deposition was determined on the basis of a precipitation map and concentration measurements. Dry deposition was calculated with inferential methods including land-use specific deposition velocities. The concentration fields for NH₃ and NO₂ were obtained from emission inventories combined with dispersion models. Reduced N compounds account for 63% of total deposition in Switzerland. As indicated by exceeded critical loads, the highest risk for harmful effects of N deposition (decrease of ecosystem stability, species shift and losses) is expected on forests and raised bogs in the lowlands, where local emissions are intense. At high altitudes and in dry inner-alpine valleys, deposition rates are significantly lower.     

Calculating Critical Loads of Sulfur Deposition for 100 Surface Waters in China Using the Magic Model

Although decades of acid deposition have apparently not resulted in surface water acidification in China, some surface waters may have the potential trend of being acidified, especially those in southern China. In this paper, a dynamic acidification model–MAGIC was applied to 100 surface waters in southern and northeastern China to evaluate the impact of acid deposition to surface waters and to determine their critical loads of S deposition, both regions having distinguishing soil, geological and acid deposition characteristics. Results indicate that most surface waters included in this paper are not sensitive to acid deposition, with critical loads of S for these waters comparatively high. On the other hand, surface waters in southern China, especially those in Fujian, Jiangxi and Guangdong provinces, are more susceptible to acidification than those in northeastern China, which coincides with their different patterns of soil, geological and acid deposition conditions. Among all the waters, a few small ponds, such as those on top of the Jinyun mountain and Emei mountain, are the most sensitive to acid deposition with critical loads of 1.84 and 3.70 keq·ha^?1·yr^?1, respectively. For the considerable ANC remaining in most 100 surface waters, it is not likely that acidification will occur in the near future for these waters.     

Testing the Feasibility of Using the ForSAFE-VEG Model to Map the Critical Load of Nitrogen to Protect Plant Biodiversity in the Rocky Mountains Region, USA

The ForSAFE-VEG model was used to estimate atmospheric nitrogen deposition and climate effects on soil chemistry and ground vegetation in alpine and subalpine zones of the northern and central Rocky Mountains region in the USA from 1750 to 2500. Model simulations for a generalized site illustrated how the critical load of atmospheric nitrogen deposition could be estimated to protect plant biodiversity. The results appear reasonable compared with past model applications in northern Europe. Atmospheric N deposition critical loads estimated to protect plant biodiversity were 1 to 2 kg N/ha/year. This range could be greater, depending on the values selected for critical site-specific parameters (precipitation, temperature, soil chemistry, plant nutrient uptake, and any eventual harvest of biomass) and the amount of biodiversity change allowed.     

Critical Loads of Acid Deposition for Wilderness Lakes in the Sierra Nevada (California) Estimated by the Steady-State Water Chemistry Model

Major ion chemistry (2000–2009) from 208 lakes (342 sample dates and 600 samples) in class I and II wilderness areas of the Sierra Nevada was used in the Steady-State Water Chemistry (SSWC) model to estimate critical loads for acid deposition and investigate the current vulnerability of high elevation lakes to acid deposition. The majority of the lakes were dilute (mean specific conductance?=?8.0 μS cm^?1) and characterized by low acid neutralizing capacity (ANC; mean?=?56.8 μeq L^?1). Two variants of the SSWC model were employed: (1) one model used the F-factor and (2) the alternate model used empirical estimates of atmospheric deposition and mineral weathering rates. A comparison between the results from both model variants resulted in a nearly 1:1 slope and an R ² value of 0.98, suggesting that the deposition and mineral weathering rates used were appropriate. Using an ANC_limit of 10 μeq L^?1, both models predicted a median critical load value of 149 eq ha^?1 year^?1 of H⁺ for granitic catchments. Median exceedances for the empirical approach and F-factor approach were ?81 and ?77 eq ha^?1 year^?1, respectively. Based on the F-factor and empirical models, 36 (17 %) and 34 (16 %) lakes exceeded their critical loads for acid deposition. Our analyses suggest that high elevation lakes in the Sierra Nevada have not fully recovered from the effects of acid deposition despite substantial improvement in air quality since the 1970s.     

Critical Loads of Sulphur and Nitrogen for Terrestrial Ecosystems in Europe and Northern Asia Using Different Soil Chemical Criteria

A critical load data base was developed for Europe and Northern Asia using the latest data bases on soils, vegetation, climate and forest growth. Critical loads for acidity and nutrient nitrogen for terrestrial ecosystems were computed with the Simple Mass Balance model. The resulting critical loads are in accordance with critical loads from previous global empirical studies, but have a much higher spatial resolution. Critical loads of acidity are sensitive to both the chemical criterion and the critical limit chosen. Therefore a sensitivity analysis of critical loads was performed by employing different chemical criteria. A critical limit based on an acid neutralizing capacity (ANC) of zero resulted in critical loads that protect ecosystems against toxic concentrations of aluminium and unfavourable Al/Bc ratios, suggesting that ANC could be an alternative to the commonly used Al/Bc ratio. Critical loads of nutrient nitrogen are sensitive to the specified critical nitrate concentration, especially in areas with a high precipitation surplus. If limits of 3–6 mg N l^?1 are used for Western Europe instead of the widely used 0.2 mg N l^?1, critical loads double on average. In low precipitation areas, the increase is less than 50%. The strong dependence on precipitation surplus is a consequence of the simple modelling approach. Future models should explore other nitrogen parameters (such as nitrogen availability) instead of leaching as the factor influencing vegetation changes in terrestrial ecosystems.     

基于MaxEnt模型预测未来气候变化情景下中国区域水稻潜在适生区的变化

基于双季稻（早稻、晚稻）和一季稻的站点数据以及历史时期（1970−2000年）与未来时期（2081−2100年）气候数据,利用最大熵模型（MaxEnt）,研究影响中国水稻种植分布的主要气候因子,并预测分析水稻在历史与未来时期适生区的变化,为未来气候变化下中国水稻的合理种植提供参考依据。结果表明：（1）影响双季稻分布的主要气候因子为最干旱月降水量、最暖季度平均气温和最干旱季度降水量;影响一季稻分布的主要气候因子为年平均气温和最暖季度降水量。（2）在历史时期,早稻和晚稻适宜种植区主要在长江中下游地区及以南地区,其适宜种植区面积占比分别为14.26%和13.01%,其中大部分地区为较适宜区,占比分别为7.66%和6.62%;一季稻适宜种植区面积占比为45.46%,主要以较适宜和适宜地区为主,面积占比分别为23.47%和18.86%。（3）相比历史时期,未来时期早稻的适宜种植区面积占比在SSP126、SSP245和SSP585情景下将分别增加6.27个、9.26个和16.66个百分点,晚稻分别增加4.26个、5.55个和10.97个百分点,一季稻分别增加11.34个、18.46个和28.31个百分点。到21世纪末,早稻的适宜种植区在空间分布上向川渝、黄淮地区扩张,晚稻的适宜种植区在空间分布上向川渝和长江中下游地区以北小部分地区扩张,一季稻的完全适宜区表现出向华北平原和东北地区扩张。整体而言,未来气候变化有助于扩大中国水稻适宜种植区。     

Chloride Deposition and Distribution in Soils Along a Deiced Highway – Assessment Using Different Methods of Measurement

A comparison was made of the ability of three different methods to describe the deposition and distribution of chloride from deicing salt in the roadside environment along a highway: direct sampling of airborne deposition (including snow ploughing) in containers; soil sampling and analysis of chloride content in the topsoil; and direct current resistivity measurements. Each method showed a distribution with significant decreasing values with increasing distance from the road. Two transport mechanisms, splash and spray, were identified when describing the airborne deposition. A mathematical model that includes these two transport mechanisms was adopted, and the total amount of airborne deposition on the ground 0–100 m from the road was estimated to approximately 45% of the salt applied on the road. The main part of the chloride spread by air and ploughing ended up within 10 m from the road. The soil sampling and resistivity measurements also showed the highest impact within this distance. The variation in chloride content in the soils reflected a poorer drainage ability of fine-grained soils compared to more coarse-grained soils. The resistivity measurements represented an integrated value of the differences in geology, water content and salinity. The increase in resistivity with distance from road in the topsoil was interpreted to reflect the distribution of chloride from deicing salt.     

Studies of Atmospheric Nitrogen Deposition in a Mire of the German National Park Hochharz Mountains Using Two Different Methods

The purpose of this study was to determine the nitrogen (N) deposition in a mire of the German National Park Hochharz Mountains in regard to different input pathways of open area and forest stand deposition. High N deposition rates strongly affect the development and growth of mires in general. For determination of the open area N deposition two methods were applied: the bulk deposition method and the Integral Total Nitrogen Input (ITNI) method. This method is based on the ¹⁵N isotope dilution technique and was adapted at this study to evaluate its applicability for natural ecosystems as well as to compare with the traditional bulk method. The forest stand deposition included canopy throughfall, stemflow and fog was measured by means of bulk collectors. On the test site, bulk deposition measurements showed an input of 27 kg N ha^{? 1} yr^{? 1} in the open area and 47 kg N ha^{? 1} yr^{? 1} in the forest stand. The higher N input in the forest stand is caused by interception of fog by the canopy. N concentrations in fog were up to more than six times higher than in rain. The ITNI system yielded a total N deposition of 30 kg N ha^{? 1} yr^{? 1} on average in the open area. The small differences between the two simultaneously applied measuring techniques were caused by a minimum biomass development of the autochthonous plant Calamagrostis villosa in the ITNI system. With increasing biomass production the influence of plants on the atmospheric N input also increased. It can be concluded that the ITNI system is beneficial for the application in a natural ecosystem when using more robust and biomass producing plants. The measured atmospheric N deposition exceeds the critical load for nutrient poor mires and represents therefore a potential risk for the continuity of this ecosystem.     

基于两种方法建立辽宁大豆产量丰歉预报模型对比

利用辽宁省56个气象站1992?2016年逐日气象资料和5个代表农业气象站的大豆发育期资料,计算不同生育期关键气象因子和气候适宜度指数,分别建立基于关键气象因子和气候适宜度的辽宁省大豆逐候产量动态预报模型,并进行回代检验和预报检验。结果表明：基于关键气象因子的预报模型在6月16日、7月21日、7月26日、8月1日、8月26日和9月16日可以进行产量预报（P＜0.05）,基于气候适宜度的预报模型在8月16日-10月1日每候可进行1次产量预报（P＜0.05）;两种预报模型的平均回代检验准确率均高于83.0%;基于气候适宜度的预报模型回代检验准确率和预报检验准确率的变幅较小,稳定性更高;应用两种预报模型,辽宁省大豆产量趋势预报业务得分＞0的年份约占60%。说明利用两种模型对辽宁省大豆产量进行动态预报均能满足业务服务需求;进行趋势预报时,可以优先考虑基于关键气象因子的预报模型,而在未出现重大气象灾害的正常年份,可以赋予基于气候适宜度的预报模型更多权重,以减少预报时次。     

Adapting the Profile Model to Calculate the Critical Loads for East Asian Soils by Including Volcanic Glass Weathering and Alternative Aluminum Solubility System

Adaptation of the steady-state soil chemistry model PROFILE was studied, on the following two parts, to calculate the critical loads for East Asian soils: (1) Dissolution rate coefficients of volcanic glass were derived from published experimental data, and calculated field weathering rate was compared with the rate estimated based on Sr isotope analysis. When BET surface area of sand fraction was regarded as mineral surface area, the calculated rates fairly agreed with the estimate, suggesting that sand fraction surface area is a reasonable estimate of weatherable mineral surface area of volcanic soils. (2) In repeated leaching experiments, Al solubility of a number of Japanese soils was explained by a model which assumed complexation of Al to soil organic matters. Such an Al solubility model is more appropriate for predicting soil chemistry than apparent gibbsite dissolution equilibrium.     

An Overview of Nitrogen Critical Loads for Policy Makers, Stakeholders, and Industries in the United States

Critical load values are calculated to determine ecosystem responses to deposition in a given area; these values may act as a tool to identify sensitive ecosystems in further need of protection. This overview provides an introduction to nitrogen critical loads for policy makers and parties involved in managing nitrogen deposition including electric utility generators, transportation managers and automobile manufacturers, and large-scale agricultural operators in the United States. It examines the use of the critical loads concept in European nations for establishing policy guidelines, current research on nitrogen critical loads in the U.S., and the development of nitrogen critical loads modeling and mapping.     

Numerical Methods for Estimating the Soil Hydraulic Properties and the Wetting Front in the Soil

Eurasian Soil Science - The unsaturated zone in the soil generally plays an important role in the transfer of water and pollutants in the underground environment. To simulate the water flow in this...     

基于MIKE模型的不同淤地坝型组合情景对小流域侵蚀动力和输沙量的影响

为科学认识黄土高原淤地坝建设对小流域侵蚀动力过程的影响,通过分布式水文模型MIKE SHE和一维水动力模型MIKE 11耦合模拟了王茂沟流域的洪水过程,并计算了流域主沟不同断面的侵蚀动力参数和不同坝型组合的减沙效益。结果表明:(1)淤地坝建设在不同程度上改变了小流域沟道的侵蚀动力分布,坝系建成后沟道的侵蚀动力参数减幅最大。(2)小流域径流侵蚀功率表现为上中游剧烈变化,下游趋于稳定,且下游径流侵蚀功率明显小于上游。(3)淤地坝建设可以有效减小流域的输沙量,其中单独建设骨干、中型、小型坝相比流域未建坝时,输沙模数分别减少24.74%,47.11%,64.11%;流域坝系建成后减沙效益最明显,流域输沙量减少83.92%。研究成果可为黄土高原淤地坝减沙效益评估提供科学参考。     

Base Cation Removal in Harvesting and Biological Limit Terms for Use in the Simple Mass Balance Equation to Calculate Critical Loads for Forest Soils

The Simple Mass Balance (SMB) equation allows critical loadsto be calculated for forest soils such that all the processesresponsible for acidification and buffering are considered(i.e acidic deposition, deposition of base cations andchloride, mineral weathering, base cation uptake and removalat harvest, nitrogen immobilisation, uptake anddenitrification, and acidity leached). The equation is nowused by 11 UNECE countries in mapping forest critical loadsfor consideration under the Convention on Long RangeTransboundary Air Pollution. In the work described here wehave put together suitable stemwood and bark nutrientconcentrations from the literature with new measurements inorder to calculate species' specific base cation removalterms. Critical loads are then calculated for Quercuspetraea, Pinus sylvestris and Picea sitchensis in order to determine the sensitivity of site critical load values to differences in base cation removal at harvest. The alternativeapproaches of using base cation to aluminium or calcium to aluminium for the biological limit term of the SMB equation arealso examined. Soil critical load values are shown to be influenced by the variability in both these terms, placing priority on the need for species and regional (or perhaps site)specific data similar to those presented here for the UK.     

基于遥感技术的植被盖度动态变化在环保验收中的应用研究

基于"3S"技术,利用泰和至井冈山高速公路建设前(2001年)、建设中(2004年)及建设后(2005年)的3个时相的Landsat-TM5遥感数据对公路建设影响区的施工场地、取弃土场地等有人为活动干扰的敏感区域进行植被覆盖动态变化分析,结合GPS野外定位等现场调查实际情况进行比对,结果表明:在公路沿线的各敏感区域内,公路建设前的原始植被覆盖率要整体上高于建设中及建设后的;少数施工场地在公路竣工采取地表恢复后的植被覆盖度仍较低,植被有待于进一步采取措施恢复;基于遥感技术分析的公路建设后各敏感区域植被恢复情况与野外调查的实际状况较吻合,以"3S"为技术手段的植被盖度动态变化分析方法可以用于公路建设影响区的环境保护验收中.     

Calculating Weathering Rates of Stream Catchments in the English Lake District Using Critical Element Ratios, Mass-Balance Budgets and the Magic Model

The weathering rates of forty-seven stream catchments in the English Lake District were calculated using 1) critical element ratios; 2) mass-balance budgets; and 3) the MAGIC model. There was a great deal of variability in the weathering rates of the five different parent material groups (greywacke, slate, andesite, tuff and granite) found in the study area. However when individual catchments were considered, the three methods provided consistent base cation weathering rates. This suggests that any of the methods could be employed for future catchment weathering studies. This paper also explores the implications of the weathering results when considering the possibility of the area becoming acidified due to increased loads of sulphur and nitrogen in the future.     

不同植被恢复模式下三峡库区万州段消落带土壤养分及其空间分布特征

消落带植被状况与水位消涨是影响土壤养分及其分布的重要因子。本文以三峡库区万州段消落带为研究地点,通过对人工和自然恢复样地沿海拔梯度对土壤进行取样和分析,揭示了不同恢复模式下消落带土壤养分及其空间分布特征。研究结果表明,植被恢复模式对土壤养分有显著影响,人工恢复样地消落带主要土壤养分含量总体高于自然恢复样地,显示人工恢复能有效促进土壤养分在植物群落中的积累;在库区反季节水位消涨的作用下,人工恢复地消落带土壤养分沿海拔梯度呈先增加后减少的空间分布格局,土壤养分含量在消落带中部(海拔165 m)达到最高值,而自然恢复地土壤有机质和全氮的空间分布则随海拔梯度增加而增加,以消落带上部(海拔175 m)的值最高。土壤养分的空间分布格局源自于不同海拔梯度的消落带受水位消涨扰动程度以及植被恢复状况的差异,植被恢复模式对土壤养分的空间分布仍有一定影响。今后应在消落带上部进一步引种适宜的乔灌木物种,不断提高消落带植被对土壤养分的固持能力。     

高光谱土壤多元信息提取模型综述

  目的  以长沙及周边区域水田土壤为研究对象,从特征空间和样本空间角度优化建模数据集,以提升基于土壤高光谱数据估测有机质含量模型的精度。  方法  利用马氏距离(MD)优化土壤光谱特征空间、最小生成树(MST)分割样本数据集优化建模样本空间,结合交叉验证岭回归(RidgeCV)和支持向量机回归(SVR)构建土壤高光谱有机质含量估测模型。  结果  在测试集上,光谱优化建模方法MD-RidgeCV和MD-SVR的模型决定系数(R²)分别为0.876、和0.84,样本优化建模方法MST-RidgeCV和MST-SVR 的R²指标分别为0.847和0.815,而两种优化方法相结合的MD-MST-RidgeCV和MST-MD-RidgeCV模型 R²指标均高达0.9;对比基于原始数据集和建模集优化KS和SPXY方法的土壤有机质含量估测模型,提出的方法在测试集上具有更佳的模型预测性能。  结论  利用马氏距离和最小生成树,从光谱特征空间和样本空间优化建模数据集,并结合回归算法RidgeCV和 SVR构建土壤有机质含量高光谱预测模型,能显著提高模型精度和稳定性。     

An Empirical Approach for Assessing the Relationship Between Nitrogen Deposition and Nitrate Leaching from Upland Catchments in the United Kingdom Using Runoff Chemistry

Samples were collected from 13 upland sites (main inflow and loch outflow) in the UK along an N deposition gradient of 12-50 kg ha^-1 yr^-1 to determine the relationship between N deposition and NO₃ ^- concentrations in surface waters. There was no direct correlation between NO₃ ^- leaching and soluble inorganic N deposition at these sites, but a significant relationship with NO₃ ^- was found using a deposition function incorporating dissolved organic carbon (DOC) flux from each catchment. A similar but less significant relationship was found between NO₃ ^- concentration and DOC:DON ratio in runoff water. Catchments showed evidence of N saturation, i.e., when mean NO₃ ^- concentration exceeded 5 µeq L^-1, when the mean DOC:DON ratio fell below an approximate value of 25. Five other large loch sites (LLS) with multiple subcatchments were used to test these relationships and for four of these mostly heathland sites the predicted NO₃ ^- concentrations closely matched measured values. At the fifth site, where most subcatchments were forested, the deposition function and DOC:DON ratios gave conflicting predictions and both methods generally underestimated measured NO₃ ^- concentrations. If the capacity of these catchments to retain deposited N is determined by C supply then many upland catchments in the UK may experience increasing NO₃ ^- concentrations in runoff in the future at current or increased levels of N deposition.     

黄河三角洲引黄灌区不同植被类型的蓄水保土功能研究

为探讨引黄灌区不同植被类型的防风固沙、蓄水保土及改良土壤效应,以黄河三角洲小开河引黄灌区沉沙池段内的杨树林、冬枣经济林、杨树+大豆农林间作和玉米农田作为研究对象,测定分析不同植被类型下的土壤水蚀量、风蚀量、土壤水文物理参数和土壤养分等指标。结果表明,(1)不同植被类型的土壤侵蚀深度和侵蚀模数均低于裸地。杨树+大豆农林间作抵抗风蚀能力最好,其次是杨树林;冬枣林和农林间作抵抗水蚀能力好于玉米地和杨树林。发生风蚀和水蚀的月份分别以3-4月和7-8月为主。(2)植被恢复措施明显改善土壤物理结构和蓄水性能,土壤表层的蓄水能力好于20-40cm土层。冬枣林蓄水能力较高,农林间作涵蓄有效水分较弱。土壤渗透性能表现为:玉米地杨树林冬枣林杨树+大豆间作。(3)植被恢复措施可显著提高土壤有机质及速效养分含量,土壤表层养分含量高于20-40cm土层。农林间作的土壤有机质和速效氮含量最高,其次为冬枣林和玉米地;冬枣林速效磷和速效钾含量最高,其次为玉米地和农林间作,杨树林在改善土壤养分效能方面较差。综合来看农林间作在引黄灌区沉沙池段具有较好的蓄水保土和改良土壤效应。