Long-term Continuous Measurements of SO2 Dry Deposition over the Speulder Forest

In 1990 a project to develop a dry deposition monitoring method of SO₂, NH₃ and NO₂ to Speulder forest in the Netherlands began. Detailed annual deposition fluxes for these gases were measured throughout November 1992 to December 1995. This paper describes the measurement set-up and the analysis of the deposition parameters for SO₂. The dry deposition velocity was usually smaller than the maximum V_d, showing a resistance to surface uptake, except for periods when the canopy is wet and surface resistance is negligible. Several methods were tested to estimate annual average fluxes from the gradient measurements. Annual fluxes were estimated by selecting the data for periods fulfilling gradient theory and extending the data by using an inferential method for the other periods. The surface resistance parametrisation used in the inferential method was tested using the selected data and was found to yield systematic larger fluxes of the order of 20%. Annual fluxes were 465 mol ha^-1 a^-1 in 1992/1993, 460 mol ha^-1 a^-1 in 1994 and 330 mol ha^-1 a^-1 in 1995. The uncertainty in the annual flux was estimated to be 25%. The annual average dry deposition velocity was 1.5 cm s^-1. No large differences were found in deposition parameters between each of the three years.     

Critical Loads of SO2 Dry Deposition and Their Exceedance in South China

The critical loads of SO₂ dry deposition in South China,which is transferred from critical level, as well the excess ofcritical loads are computed and mapped. The areas with thelowest critical load and the highest excess are, respectively,identified. The research is complementary to the previousresearches on critical loads for soils, and expected to beintegrated with them to make efficient sulfur emission abatement strategy.     

Fine Particle Dry Deposition onto a Cropland — a Trial to Estimate Deposition Velocity

The dry deposition velocity of fine particles is usually on the order of several tenths of cm s^?1, and accordingly, the concentration gradient of particles above the surface is very small. This makes the application of the gradient method to the determination of the particle deposition velocity very difficult. This study is a trial to find a way around this difficulty. The idea is to evaluate the thickness of the molecular diffusion layer, zb by simultaneously measuring the concentration gradient of gaseous species such as SO₂ ; zb is obtained by combining the turbulent and molecular transport equations for the gas. Then the particle deposition velocity is estimated on the basis of zb and the Brownian diffusion coefficient with an assumption that zb is equal to the thickness of the Brownian diffusion layer. By applying this method to the data collected in a field observation, the velocity of deposition onto a cropland was estimated for submicron particles.     

Simultaneous Determination of Gas and Particle Dry Deposition onto Conditioned Surrogate Surfaces

Aerodynamically designed surrogate surfaces were used to determine the relative importance of gaseous (SO₂, HNO₃, NH₃) and particulate species (SO₄ ^2?, NO₃ ^?, NH₄ ⁺, Ca²⁺) in the dry deposition flux. For 11 sampling periods, we measured the deposition fluxes, ambient gaseous concentrations, size distributions of atmospheric aerosols and some meteorological parameters in Uji. The dry deposition of the gas to a nearly perfect sink was calculated by subtracting the greased surface flux from the total deposition flux to both the greased and reagent impregnated (or water) surface. It was found that the gas phase deposition contributed significantly more (60–93%) than the particulate phase to overall deposition of sulfur and nitrogen compounds. The dry deposition velocities of the species were also calculated using the deposition fluxes and the measured ambient concentrations. Comparisons were made between the measured and modeled particulate deposition flux.     

黄土高原旱地果园土壤水分管理研究

在黄土高原中、南部的延安宝塔区和淳化县,测定了旱地果园土壤储水量,测定结果表明:在苹果生育期,以60%田间持水量作为水分亏缺的标准,不同月份土壤储水量变幅很大,均出现不同程度的亏缺,需要补水才能满足苹果的正常生长要求。进行苹果需水规律试验和品质测定表明,在该地区优质苹果生产需水量为600mm左右。通过有限灌水技术试验证实,穴灌的净增值率高达58.7%。     

Emission Control of SO2 by Dry Coal-Cleaning and Bio-Briquette Technology

In China, the large amount of sulfur dioxide and dust discharged from the combustion of low-grade raw coal causes severe air pollution and acid rain. Therefore, the need to control the emission of such pollutants is urgent. It is well known that wet coal-cleaning technology is used to prepare clean coal from low-grade raw coal containing large amounts of sulfur and ash. However, this technology is not used in areas where water is scarce or severely polluted, because of the high cost of treating the wastewater. In an attempt to overcome this limitation, we studied an integrated technology, which combines dry coal-cleaning and bio-briquetting technologies, to prepare clean coal from low-grade raw coal. In the dry coal-cleaning method, refined coal was separated from ash and other minerals containing inorganic sulfur as pyrite by means of the differences in their electrostatic character. Most of the sulfur left in the refined coal was organic sulfur. The residual ash was fixed in combustion ashes of bio-briquettes made from coal, biomass, and slaked lime (Ca/S mole ratio =2) under pressure. By combining these two technologies, we were able to decrease the emission of sulfur dioxide and ash by 70≈90% compared to the combustion of raw coal.     

基于黄土沉积速率的土壤侵蚀危险度评价

土壤侵蚀危险度是评估和预测侵蚀作用破坏土地资源和生态环境危险性的重要指标,也是科学防治水土流失的基础。利用14 C测年技术对陕北黄土高原黄土沉积速率进行研究,并通过计算土壤侵蚀模数与黄土沉积速率的比值,对该研究区的土壤侵蚀危险度进行评价。结果表明:洛川县、延长县和横山县采样点的黄土沉积速率分别为0.017 9cm/a,0.015 3cm/a和0.021 3cm/a,土壤侵蚀危险度分别为14.1,43.3和24.8,均远远大于临界危险度值1,因此该地区为水土流失重点防治区域。通过该项研究可以为水土保持治理及规划提供科学参考,并为环境治理决策部门提供理论依据。     

A Case Study on Estimation of Dry Deposition of Sulfur and Nitrogen Compounds by Inferential Method

In order to estimate dry deposition, deposition velocity calculation and concentration measurement were carried out in Niigata, Japan. Deposition velocities of SO₂ and HNO₃ for some surfaces such as coniferous forest, deciduous forest, agricultural land, and water were calculated taking into account diurnal variations of meteorological elements using routine meteorological data. Deposition velocities of fine and coarse aerosols were also estimated respectively. Concentrations of SO₂, HNO₃, sulfate and nitrate in fine and coarse aerosols respectively were measured from July to December in 1998 using filter pack and denuder methods. The results indicate that HNO₃ dry deposition for the high aerodynamic roughness surfaces such as forests is quite large. It is suggested that sulfate and nitrate aerosols depositions as well as the gases depositions should be taken into account to estimate dry deposition of sulfur and nitrogen compounds. It is also indicated that dry depositions of sulfur and nitrogen compounds are unable to ignore compared with their wet depositions.     

Characterizing Dry Deposition of Mercury in Urban Runoff

Stormwater runoff from urban surfaces often contains elevated levels of toxic metals. When discharged directly into water bodies, these pollutants degrade water quality and impact aquatic life and human health. In this study, the composition of impervious surface runoff and associated rainfall was investigated for several storm events at an urban site in Orlando, Florida. Total mercury in runoff consisted of 58% particulate and 42% filtered forms. Concentration comparisons at the start and end of runoff events indicate that about 85% of particulate total mercury and 93% of particulate methylmercury were removed from the surface before runoff ended. Filtered mercury concentrations showed less than 50% reduction of both total and methylmercury from first flush to final flush. Direct comparison between rainfall and runoff at this urban site indicates dry deposition accounted for 22% of total inorganic mercury in runoff.     

黄土旱塬不同氮肥用量下冬小麦干物质累积和氮素吸收利用过程研究

利用旱作长期定位施肥试验研究了不同氮肥用量对冬小麦干物质累积和氮素吸收利用的影响,结果显示,不同处理下干物质累积变化趋势都呈"S"型曲线,且冬小麦各生育期干物质量,随氮肥用量的增加而增大,说明氮肥对促进冬小麦干物质累积作用显著。干物质累积速率均呈现明显的单峰曲线,拔节-灌浆阶段累积速率最大,是干物质累积的重要时期。小麦植株含氮量和氮素累积量都随氮肥用量增加而升高,在冬前-拔节期和开花-灌浆期两个阶段,冬小麦植株氮素累积量较大,累积速率快,是氮素吸收利用的两个关键阶段。     

陕北黄土丘陵沟壑区坡面侵蚀—沉积过程试验研究

[目的]分析各影响因素作用下黄土坡面的侵蚀—沉积过程,为陕北黄土丘陵沟壑区水土保持措施的合理布设以及水土流失防治规划提供科学依据。[方法]采用室内人工模拟降雨试验方法对不同坡度、坡长和60 mm/h降雨强度条件下的黄土坡面侵蚀—沉积过程特征开展研究。[结果](1)净侵蚀过程主要发生时间为在达到侵蚀速率峰值前后,在降雨开始35 min左右内,侵蚀速率在整个降雨过程出现正负值交替变化,侵蚀过程与沉积过程并存。(2)坡度为5°,10°,15°时,单位面积侵蚀量随坡长的增加而减少,5—10 m坡段中存在明显的沉积过程和临界侵蚀坡长。试验条件下黄土坡面发生沉积的临界坡长在4—5 m以及5—10 m范围内。(3)在5°,15°坡度下,整个降雨过程中0—5 m坡段的累计单位面积侵蚀量均大于0—10 m坡段坡面,侵蚀过程中一直伴有沉积现象;10°坡面分别在降雨后15 min左右开始伴有沉积现象出现。[结论]坡度和坡长是影响黄土坡面侵蚀—沉积过程的重要因素,坡面径流含沙量和单位面积侵蚀量可以作为表征黄土坡面侵蚀—沉积特征的重要因子。在治理坡面水土流失时应采用拦截中上坡位径流的水土保持措施。     

黄土高原干旱阳坡微地形土壤水分特征研究

黄土高原地区坡面内地表的起伏形成微地形,利用其土壤含水量的差异来提高植被成活率已经成为黄土高原生态恢复建设的重要方向.采用探针式TDR对陕西省吴起县合家沟流域内的微地形及其相应原状坡的土壤含水量进行测定.结果表明,微地形对土壤含水量有显著影响,阳坡各微地形土壤水分顺序为:塌陷>切沟底>缓台>浅沟底>原状坡>陡坎.0-20cm土层土壤水分变异系数最大的是切沟底为405,最小的是缓台仅0.226,阴坡原状坡各层的变异系数均小于阳坡的微地形.最后指出黄土高原地区植被恢复建设时,在按传统立地类型划分原则所确定的植被恢复单元内,还应该按照微地形的水分特征有区别地配置植被类型.     

黄土丘陵区旱年造林技术试验

黄土丘陵区干早年份较常见,春旱尤为严重。在这一地区造林的成效,首先取决于水分条件。在干早年份造林,采取以下技术措施:水平阶和大型鱼鳞坑整地、中耕除草、利用就地坑穴蓄水和浇少量水,地膜覆盖等,可以提高造林的成活率,有利树木的生长。     

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.     

Deposition Patterns of SO4 2−, NO3 − and H+ in the Brazilian Territory

SO₄ ^2?, NO₃ ^? and H⁺ depositions are estimated in the Brazilian territory based on the existing rainfall chemical data and on annual rainfall distribution over the whole territory. Local and regional depositions are estimated. Rainfall chemical data over the Braziliian territory shows that the average pH values are usually low (between 4.0 and 5.5). These values are observed in the tropical Amazon forest as well as in urban areas. However, the rainwater acidity in the tropical forests are due to organic acids naturally produced by the vegetation while in urban areas the acidity is mainly due to acidic anion deposition (NO₃ ^? and SO₄ ^2?). In some Amazonian areas, the average input values through rainfall for NO₃ ^? is about 0.06 keq.ha.yr^?1 and for SO₄ ^2? is between 0.23 and 0.54 keq.ha^?1.yr^?1. On the other hand, in some urban centers, such as São Paulo, values of .072 keq.ha^?1.yr^?1 for NO₃ ^? and 1.16 keq.ha^?1.yr^?1 of SO₄ ^2? are found and in sites where sulfate sources (coal mining) are present, as for the area of Florianópolis, values as high as 5.59 keq.ha^?1.yr^?1 for SO₄ ^2? are found.     

Dry deposition velocity estimates of SO2 from models and measurements over a deciduous forest in winter

Measurements were made of concentrations and vertical flux densities (using the eddy correlation technique) for SO₂ over a deciduous forest during March and April 1990. These were compared with estimates of dry deposition velocities, obtained from resistance analogue models that employ measured meteorological data as input. The models include: (1) the dry deposition module that forms part of a larger Eulerian air quality model, known as ADOM (Acid Deposition and Oxidant Model), (2) a modified version of ADOM and (3) a new parameterization for R _c . The observations yielded V _d values of about 0.5 cm s^?1 for the daytime and 0.1 cm s^?1 at night. ADOM's estimates were much larger, averaging about 3.0 cm s^?1 during the daytime and about 2.0 cm s^?1 at night. When the ADOM canopy resistance was increased by modifying its formulation, the modified dry deposition estimates were slightly larger during the day than at night, averaging about 0.5 cm s^?1. The new parameterization for R _c yielded smaller V _d estimates with no diurnal variation. An attempt is made to relate the observed diurnal cycle of the dry deposition velocity to meteorological parameters.     

陇东黄土高原塬区冬小麦干物质增长规律分析

用Logistic生长曲线对陇东黄土高原塬区冬小麦干物质积累进行不同气候年型的模拟分析表明：干物质积累在拔节后到乳熟期呈直线递增趋势。增长速率最快时期在抽穗前后．呈单峰型曲线。在不同的气候年型下干物质累积量与降水量、日照时数、≥0℃积温的关系均达极显著水平，而干物质生长率仅在少雨年与气象要素呈显著关系，其它两种气候年型下相关不显著。     

黄土旱塬农田全程全覆盖的“土壤水库”作用

晋南黄土旱塬虽土层深厚 ,蓄水、保水性能良好 ,但传统农业的农田“土壤水库”作用有限 ,在年降水量较小且分布不均匀 ,而蒸发量较大的情况下 ,天然降水利用率很低 ,作物产量极不稳定。为寻求解决这一问题的有效途径 ,于 1991～ 1996年进行了 6年的探索 ,研究出在旱地农田实行全程全覆盖的保水措施 ,采用不同覆盖材料 ,配合垄作方式 ,既能较大程度地吸纳天然降水 ,又可做到全程全封闭地抑制土壤水分蒸发 ,形成良好的“土壤水库”,使不均衡的天然降水变为较均匀的供水 ,在整个覆盖周期内其土壤贮水量始终高于半覆盖和不覆盖处理 ,有效地缓解了作物旱情 ,提高了天然降水的利用效率。     

黄土落水洞初步研究

黄土落水洞,是低凹地带湿陷性黄土长期遭受机械潜蚀和溶蚀作用的结果,它可分为黄土碟、黄土陷穴和黄土井三类。落水洞广泛分布于黄土高原,年降水量在450mm左右的湿陷性黄土地区陷穴、黄土井十分发育;黄土塬边及高阶地前缘陷穴、黄土井发育程度较好,粱区落水洞沿冲沟或小支沟呈串珠状分布;黄土丘陵地区峁坟上落水洞以陷穴为主,黄土碟次之,峁间宽缓的掌形地冲沟两侧及沟头陷穴和黄土井较为发育。黄土落水洞在滑坡、泥石流发育过程中起着重要作用,它是黄土高原地区地下水补给的重要通道。     

Statistical Modeling of Phosphorus Dry Deposition Rates Measured in South Florida

Dry deposition may be a substantial source ofphosphorus (P) to the Florida Everglades. Drydeposition has been measured on a weekly basis in theregion since 1987, but a significant amount of thisdata is missing (about 34%) due to instrumentalfailures and sample contamination. This study developsa statistical model of the P dry depositiontime-series to estimate missing data. The model isbased on a multivariate stochastic time-series theory.Model parameters are calibrated using theexpectation-maximization algorithm which is efficientfor data sets with many gaps. The pooled mean andstandard deviation of the data before estimating themissing values was 88.4±85.7 μg P m^-2d^-1 and after estimating the missing values was87.8±82.4 μg P m^-2 d^-1. Modelverification demonstrates that the calibrated modelsprovide unbiased data estimates while preserving thestatistics of the raw data. For each sampling site themean and standard deviation before and after werequite similar. No trend with time was detected. The Pdeposition fluctuates seasonally (highest in Octoberand lowest in June), but this fluctuation does notfollow the seasonal pattern of Florida's rainfall. Random noise in the data, however, is significant andcauses long-term fluctuations of the data. The datawith gaps filled in are useful for computing theweekly P load distribution.