Reactions of gases on calcareous stones under dry conditions in field and laboratory studies

Dry deposition of gases plays an important role for the deterioration of stone materials and a better understanding of the processes involved will improve our ability to maintain stone monuments and buildings. As a part of an EU-project an investigation with four calcareous stone types have been exposed outdoor at two test sites in Norway for two years. The exposure has been carried out in sheltered position and the amount of reaction products and the penetration depth of SO₂ into the stones was determined as soluble sulphate after half a year and after one and two years. Even if most of the sulphate was found in the upper 0.3 mm of the stone, there was an increase in the sulphate content in stone even down to the center of the stone sample. In laboratory tests with SO₂, NO₂ and changing relative humidity the synergistic effect of NO₂ and the importance of the relative humidity was investigated. The uptake rates were calculated from the laboratory studies by analyzing the gas concentrations before and after the exposure chamber. By calculating the deposition velocity from the field study by using the amount of sulphate found in the stones together with the average outdoor concentration of SO₂ at the test sites, the values were a magnitude higher than in the laboratory test, highest at the industrial paper mill sites with high concentrations both of SO₂ and some hypochlorite and lower in urban atmosphere with fairly low values of SO₂ and high values of NO₂.     

The calculation of transboundary and deposition fluxes of SO2 and sulfate by means of aircraft measurements

Aircraft measurements of the air pollutants SO₂ and sulfate (SO_x is defined as SO₂ plus sulfate), plus data on wind velocity, wind direction and depth of the planetary boundary layer, enable the calculation of transboundary mass fluxes of SO_x. When emission data are available, an emission-deposition balance of SO_x can be determined. The results of a measurement flight, carried out on 12 February, 1986, are presented. Two tracks were flown, along the eastern and along the western border of the Netherlands, respectively. The wind was easterly. The calculated deposition flux of SO_x is converted to an area-averaged dry deposition velocity (ν _d ). The result, ν _d = 1.2 × 10^?2 m s^?1, seems to be in good agreement with literature data.     

奶牛场恶臭污染物扩散规律研究

以山东省某县中等规模的3个奶牛养殖场为试验场地,以臭气浓度为监测指标,在下风向距恶臭排放源不同距离处设置采样点,对规模化奶牛养殖场恶臭污染物的下风向扩散规律及影响扩散规律的部分气象因素进行了研究,并通过数据回归得出了恶臭污染物水平扩散模型。结果表明,奶牛场恶臭污染物的排放浓度随距离的增加迅速减小,通过线性回归得出下风向同一高度处的臭气浓度与监测点距排放源的距离呈指数函数关系;对于气象条件,在27～37℃,风速小于5.4 m.s-1的范围内,风速、空气温度和空气相对湿度对恶臭污染物扩散规律的影响均显著,其中温度和风速对恶臭污染物扩散规律的影响较空气相对湿度大。     

恒温下相对湿度对果蔬热风干燥特性和品质的影响及调控

相对湿度作为干燥介质的重要参数，对干燥热质传质过程和干燥品质具有显著影响。但由于相对湿度对干燥过程的影响机理及优化调控机制尚不明确，导致相对湿度的调控方式多依靠经验，造成干燥效率低、品质差、能耗高等问题。对于传质过程，降低相对湿度能够增大对流传质系数，加快物料表面水分蒸发；而对于传热过程，升高相对湿度能够增大对流传热系数，加快物料升温速率。相对湿度较高时，物料升温速率快，内部水分迁移量增大，但表面水分蒸发量较小；而当相对湿度较低时，物料升温速率较慢，内部水分迁移量较小，但表面水分蒸发量较大。相对传热和传质过程的影响此消彼长，互相耦合。高相对湿度主要体现为对传热过程的影响，低相对湿度主要体现为对传质过程的影响。高相对湿度能够抑制物料表面的结壳，并能够提高复水性，降低收缩率。阶段降湿及多阶段降湿干燥方式下物料表面形成和保持了蜂窝状多孔结构，能够提高干燥效率和品质。基于监测物料温度的相对湿度调控方式被验证为较忧的相对湿度控制方式。阶段降湿干燥方式适用性的实质为：干燥过程中所体现出的对流传热热阻和内部导热热阻的相对大小，及对流传质阻力和内部传质阻力的相对大小，不同干燥条件和物料种类、厚度会影响以上传热传质阻力的大小，从而呈现出不同适应性的结果。当阶段降湿干燥过程中传热毕渥数>1且传热毕渥数>0.1时，说明阶段降湿干燥过程适用于此物料的干燥。该文综合论述了相对湿度对果蔬热风干燥过程中热质传递及干燥品质的影响，优化调控策略及适用性范围4个方面内容，明确了果蔬热风干燥过程中相对湿度的影响机理，为相对湿度的优化调控提供理论依据和技术支持。     

Throughfall deposition of ammonium and sulphate during ammonia fumigation of a scots pine forest

The estimation of the dry deposition of sulphur dioxide to forests is confounded by the possibility of co-deposition of SO₂ with NH₃ on leaf surfaces. A sector of Scots pine forest was selectively fumigated with NH₃ to give average concentrations up to 15 ppbV (nL L^–1) above ambient, in order to test the hypothesis that increased air concentrations of NH₃ would enhance the dry deposition of SO₂, and the consequent amounts of SO₄ ^2– measured in throughfall below the forest canopy. Ammonia gas, generated by evaporation of concentrated aqueous solution, was released above the canopy in proportion to wind speed when the wind direction was between south and west. Concentrations of NH₃ at canopy height were measured using passive diffusion tubes; throughfall was preserved with thymol and measured weekly. Meteorological data and SO₂ concentrations were recorded continuously, to permit the estimation of dry deposition input. Deposition of NH₄ ⁺ in throughfall over 8 months was increased by up to 40 meq m^–2 relative to control sites upwind of the NH₃ release point, with largest values closest to the release point. Deposition of SO₄ ^2– in throughfall was also enhanced in the fumigated area, by up to 20 meq m^–2, even though average ambient SO₂ concentrations were 2.3 ppbV. The results are discussed in terms of the factors controlling SO₂ deposition on forest surfaces, the development of appropriate deposition models, and their relevance to using throughfall as an estimate of total S deposition.     

Dry Deposition of Atmospheric Sulphur and Nitrogen in Russia and the Former USSR

Generally, dry deposition processes are very important for atmospheric chemistry of pollutants providing up to 30–80 % of the removal for certain compounds from the atmosphere. The model for calculating of dry deposition fluxes for a large territory seems unsophisticated in spite of the dependence on surface characteristics, pollutant properties and atmospheric conditions. The approach of combining monthly average concentrations measured at the Integrated Background Monitoring Network (IBMoN) and EMEP stations and linear dry deposition velocity was used to calculate total sulphur and nitrogen fluxes for the whole of the former Soviet Union (FSU) taking into account large-scale geographical variability in climate and lands. Most values of all SO₂ and SO₄ ^2? concentrations were below 2.9 and 3.1 mgS/m³, and NO₂ concentration were 1.5 mgN/m³ over European part and 0.6 mgN/m³ in Western Siberia. The long-term trends of oxidised sulphur and nitrogen compounds in the atmosphere were examined for 1982–1998 in certain FSU regions. Annual dry deposition of sulphur was estimated as 3.64 Mt S (in sulphate form) and 2.76 Mt S (in SO₂ form) for the whole area of FSU. Annual removal of NO₂ by dry deposition was calculated at 1.27 Mt N. These values constituted between 44 and 50% of total oxidised sulphur and nitrogen deposition.     

Thermodynamic analysis of marble deterioration in the atmosphere

Using thermodynamic data, the effect of SO₂ and H⁺ on the deterioration of marble has been estimated. Theoretically, the partial pressure threshold of SO₂ required for the marble deterioration in the SO₂-marble system is in the order of 10^?54 atm. The pH of rainwater for the deterioration of marble in the H⁺-marble system was calculated at about 7.8 for the dissociation of reaction products. The thermodynamic calculations showed that SO₂-marble and H⁺-marble reactions are possible in the atmosphere, but that marble deteriorates faster by reacting with SO₂ than with H⁺. Marble can deteriorate under normal atmospheric conditions and by natural rain. Acid deposition enhances the degree of the marble deterioration in the atmosphere.     

Dependence of SO2 integrated exposure rates on SO2 concentration,wind velocity,temperature, and relative humidity

Integrated exposure rates for SO₂ of a standardized physico-chemical receptor and corresponding SO₂ concentrations and meteorological variables have been measured at various sites in the state of Northrhine Westphalia, Germany from 1982 to 1986. The dependence of exposure rates and deposition velocities of the receptor on SO₂ concentration and meteorological variables has been investigated within the framework of various regression models. A contribution of prime importance to exposure rates of the product of SO₂ concentrations and the square root of wind velocities averaged over exposure time has been established. The model explains 87% of variation. Deposition velocities for this receptor turn out to be of the order of 1 cm s ^?1. A corresponding regression model between deposition velocities and the square root of wind velocities unexpectedly explains only a minor amount of variation of this quantity.     

Atmospheric pollution in Venice,Italy, as indicated by isotopic analyses

Rainwater samples collected in Venice over a period of about 1 yr were studied along with stone samples collected from buildings and monuments. Isotopic measurements of O, S, and C were carried out on rainwater, rainwater dissolved sulfate, carbonate in stone, and sulfate present in altered limestone, with the purpose of proving that atmospheric pollution is mainly responsible for the deterioration of monuments and buildings. The results obtained lead to the conclusion that, in spite of the geographic position of the city, atmospheric sulfate in Venice is basically tied to the emission of anthropogenic SO₂ and that only minor contribution can be expected from seawater spray and aerosols. The measurements carried out on stone samples clearly indicate that stonework is damaged by the interaction between limestone and S-bearing atmospheric pollutants.     

SO2 Transformation in controlled atmosphere leading to the production of aerosol particles

The photochemical transformation of SO₂ and the generation of aerosol particles are investigated in a variety of atmospheres, with and without initial aerosols, in clean and polluted air, and with various pollutants. The pollutants in addition to the SO₂ include O₃, NO, NO₂ and water vapor in a variety of combinations. The most striking finding is, that only with the combination of SO₂, NO₂, and H₂O is the aerosol particle production large.     

自然状态下栓皮栎人工林空气负离子浓度与相对湿度的关系

空气负离子是衡量一个地区空气清洁度的重要指标,对人体的心理和生理机能具有重要的促进作用。随着森林生态旅游的兴起,空气负离子的发生过程及影响机制已成为生物气象、森林生态和森林康养等相关领域的研究热点。本研究以华北低丘山地栓皮栎人工林为试验对象,在2018年和2019年6−9月森林植被叶面积相对不变期间,定位观测获取人工林冠层空气负离子及微气象参数,采用Python软件筛选出光合有效辐射约为零,温度、风速及颗粒物浓度相对不变条件下的观测数据,分析空气湿度（RH）对空气负离子浓度（NAI）的影响特征,建立基于空气相对湿度的预测模型,并对模型进行检验。结果表明,在不同空气相对湿度范围内,空气负离子浓度随空气湿度的升高呈现三种变化趋势,在空气相对湿度35%～55%范围内,空气负离子浓度相对稳定,二者呈稳定常数关系;在相对湿度55%～75%范围内,空气负离子浓度迅速上升,二者呈线性递增关系;在相对湿度75%～95%范围内,空气负离子浓度适度下降,二者呈线性递减关系。在此基础上,构建了空气负离子浓度与空气相对湿度的分段拟合方程,3个湿度区间分别为NAI=729;NAI=9.396RH+198.994,决定系数（R2）为0.807（P＜0.01）;以及NAI=−4.849RH+1232.992,决定系数（R2）为0.642（P＜0.01）。各拟合函数的预测值与实测值均不存在显著差异,均方根误差（RMSE）分别为6.175、7.091、8.213,而RH在55%～75%和75%～95%范围内决定系数（R2）分别为0.806、0.836,模型的模拟精度高且均方根误差较小。说明构建的分段拟合函数能够准确反映空气相对湿度对空气负离子浓度的影响,可为进一步深入研究空气负离子对气候变化的响应机制提供基础依据。     

Influence of Air Pollution and Humidity on Limestone Materials Degradation in Historical Buildings Located in Cities Under Tropical Coastal Climates

Climatic changes and the increased air pollution intensify the atmospheric degradation of stone, affecting the aspect and integrity of valuable historical buildings constructed using limestone and located in tropical coastal sites. This paper analyzes limestone degradation process due to air pollution and humidity in tropical humid conditions in historical buildings located in the cities of Havana, Cuba and San Francisco de Campeche, Mexico. Havana shows higher pollution level than San Francisco de Campeche, which presents pollution levels as a consequence of a multipollutant situation along with the presence of airborne salinity. Temperature and humidity data were recorded from the walls of historical buildings in the city of Havana: the Minor Basilica and the convent of San Francisco. Changes in dry/wet cycles due to the absence of direct sun radiation as well as a high level of SO₂ allow the formation of a black crust (mainly composed of gypsum) in the lower part of the surface of the facade of the Basilica Minor in Havana; however, crusts formed in historical buildings located in San Francisco de Campeche City are mainly composed of calcium carbonate, indicating the importance of natural degradation mechanisms mainly due to dissolution in water. In the last case, the influence of water plays an important role in the development of biodegradation, which induces the formation of calcium oxalates. Caves and cracks were found in the walls of military buildings caused by water infiltration. The influence of air contamination, humidity, and construction materials determine the type of degradation that historical buildings undergo.     

Dry deposition to snow in an urban area

Ambient particle and gas concentrations, wet deposition and dry deposition were measured in Warren, MI between December 18, 1983 and April 6, 1984. Dry deposition was measured to various surfaces in a cutoff bucket, including a snow surface, a snow/water surface during melting and a deionized water surface. Dry deposition velocities were calculated for various species from the ratio of the dry flux to the ambient concentrations. The dry deposition velocities measured to a snow surface were 0.082 cm s^?1 SO₂ 2.0 for HNO₃, 0.083 for NH₄ ⁺, 2.0 for Ca⁺⁺ and 4.3 for Cl^?. The values were not significantly different for a snow/water surface during melting compared to a snow surface. However, higher values of 0.69 cm s^?1 for SO₂, 6.2 for HNO₃, 0.33 for NH₄ ⁺, and 4.2 for Ca⁺⁺ were found to a deionized water surface in the spring. These higher values could be due to the higher air temperature, the pH of the liquid or to increased atmospheric mixing during this period.     

The influence of basic aerosols on throughfall fluxes of sulfate,ammonium and nitrate in three oak stands along a distance gradient from a lime quarry

Three oak stands (Quercus petraea and Quercus robur) in the Weinviertel, Lower Austria, located along a distance gradient from a lime quarry, were studied to determine the effects of basic aerosols on the deposition of ammonium, nitrate and sulfate. Higher concentrations of limestone aerosols in the vicinity of the quarry are suggested by higher Ca²⁺ fluxes and pH in throughfall and precipitation. The ammonium/nitrate ratio in throughfall decreases with distance from the quarry, though monitoring of NH₃ and NO₂ concentrations in the air with passive samplers shows the opposite trend. These findings support the theory of discrimination against NH₃ in dry deposition due to the presence of Ca ²⁺ particles on leaf surfaces resulting from limestone aerosols. Higher sulfate deposition near the quarry is consistent with higher atmospheric SO₂ concentrations and co-deposition between calcium and sulfate.     

The Influence of Discharge,pH, Dissolved Organic Carbon,and Suspended Solids on the Variability of Concentration and Partitioning of Metals in a Rural Catchment

The study of atmospheric concentration levels at a local scale is one of the most important topics in environmental sciences. Multivariate analysis, fuzzy logic, and neural networks have been introduced in forecasting procedures in order to elaborate operational techniques for level characterization of specific atmospheric pollutants at different spatial and temporal scales. Particularly, approaches based on artificial neural networks (ANNs) have been proposed and successfully applied for forecasting concentration levels of PM₁₀, NO₂, SO₂, CO, and O₃. The present study explores the development and application of ANN models for forecasting, 24 h ahead, not only the daily concentration levels of PM₁₀ but also the number of hours exceeding the PM₁₀ concentration threshold during the day in five different regions within the greater Athens area (GAA). The ANN modeling was based on measurements and estimates of the mean daily PM₁₀ concentration, the maximum hourly NO₂ concentration, air temperature, relative humidity, wind speed, and the mode daily value of wind direction from five different monitoring stations for the period 2001–2005. The evaluation of the model performance showed the risk of daily PM₁₀ concentration levels exceeding certain thresholds as well as the duration of the exceedances can be successfully predicted. Despite the limitations of the model, the results indicate that ANNs, when adequately trained, have considerable potential to be used for 1 day ahead PM₁₀ concentration forecasting and the duration within the GAA.     

Wet and Dry Deposition of Sulphur at the Site Melpitz in East Germany. In memorium dedicated to Wolfgang Rolle

Sulphur concentrations in precipitation as sulphate and in air as sulphur dioxide were determined from October 1991 (May 1992), respectively, to December 1995. The total sulphur deposition was calculated from sum of the wet and dry deposition, using the concentration of sulphate and precipitation volume and the concentration and deposition velocity of sulphur dioxide, determined with the micrometeorological gradient method. The concentration of sulphur in precipitation decreased over the period by about 40% and in air about 70%. The wet deposition decreased over the period by about 30%. However there was no decrease in dry deposition despite the reduction in SO₂ concentrations because the deposition velocity varied from 0.16 cm s^-1 to 0.37 cm s^-1 during the period. Therefore no trend was observed in the total sulphur deposition.     

黄淮冬麦区气象因子与小麦晚霜冻害关系研究——以商丘市为例

基于1956-2015年商丘市气象数据和霜冻害资料,研究黄淮冬麦区商丘市气象因子与霜冻害的关系,以及气温、地温、相对湿度、风速与草面温度的偏相关和多元线性回归关系。结果表明:随着全球气温变暖,商丘市冬春季积温以4.35℃·d·a~(-1)的速率逐年增加;晚霜冻害除受冷空气活动影响外,与前期积温和降水量密切相关,冬春季积温偏高或降水量偏少的情况下易发生晚霜冻害;随着小麦幼穗的发育,其对低温的敏感度增加,且可引起霜冻害的最低温度有逐渐升高的趋势;气温、地表温度、平均相对湿度、平均风速与草面温度呈极显著相关(P0.01),偏相关系数的大小表现为地表温度气温平均相对湿度平均风速,可见,除气温、地表温度外,平均相对湿度、平均风速也对霜冻害的发生及轻重程度起关键作用;各因子与草面温度可用模型表述为Y=0.558ST+0.482AT+0.087RH+1.304WS-12.704,经检验,线性回归方程成立,可通过该模型对草面温度进行监测,并为未安装草面温度传感器的地区提供可靠的冻害评估结果。     

Air Pollutant Transport Analysis Based on Hourly Winds in the City of La Plata and Surroundings, Argentina

The city of La Plata and its surroundings are a very populated area, which has an important Industrial Pole and intense traffic activity but environmental studies have been rare so far. This article presents and discusses the importance of wind frequencies and velocities for the transport of air pollutants. The study emphasizes the importance of knowing wind patterns on an hourly basis that can be helpful for designing a monitoring network as well as for preventing exposure to pollutants. Correlation between monthly SO₂ concentrations and wind frequencies and velocities are discussed for a particular set of directions NNW–NE that carry pollutants from industrial sources toward populated areas. As a result, averaged wind frequencies have been found to be very important for determining patterns influencing pollutants transport; the influence of averaged velocities has shown low variability (hourly and monthly). Hierarchical cluster analysis applied to wind roses provided a useful approach for analyzing and describing the general daily occurrence of winds.     

An Exploratory Study of Particulate PAHs in Low-Polluted Urban and Rural Areas of Southwest Spain: Concentrations, Source Assignment, Seasonal Variation and Correlations with Other Air Pollutants

A set of 72?PM₁₀ samples from low-polluted urban and rural locations belonging to the regional air monitoring network of Extremadura (Spain) were collected in a 1?year sampling period. Sample pre-treatment and analytical determination by gas chromatography?Cion trap mass spectrometry were optimised and validated for the analysis of the priority 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs). The influence of meteorological conditions (temperature, relative humidity and solar radiation) and other atmospheric pollutants (O₃, NO₂, SO₂, PM₁₀) has been covered in detail and Pearson correlation test were used for this purpose. Spatial distribution of particulate PAHs was evaluated and the comparison with other European sites was also established. Possible emission sources were identified and assigned by using molecular diagnostic criteria.     

大型光伏电站对共和盆地荒漠区微气候的影响

[目的]揭示光伏电站内外局地小气候的差异,评估大型光伏电站的布设对共和盆地荒漠区小气候的影响。[方法]利用自动气象站的观测数据,通过对比对照点和光伏电站内观测点观测得到的基本气象要素(气温、相对湿度、风速和风向、辐射)和土壤温湿度评估大型光伏电站的布设对共和盆地荒漠区小气候的影响。[结果]光伏电站的布设使得共和盆地荒漠区相对湿度增加3.93%,这种影响在较干日和夜间表现的更明显。在布设光伏电站后风向由原来的东北风转为以东风为主,光伏电站的布设使得局地风向更加单一。对于风速而言,在布设光伏电站后大风速出现的比例显著降低。大型光伏电站使得共和盆地荒漠区风速减小了53.92%。大型光伏电站使得共和盆地荒漠区10,20,40cm平均土壤温度分别降低17.20%,16.75%和16.09%,对浅层的影响大于深层。光伏电站对共和盆地荒漠区10cm土壤湿度的影响较其他要素更显著,大型光伏电站使得共和盆地荒漠区10cm平均土壤湿度增加了71.61%。[结论]大型光伏电站使得共和盆地荒漠区的湿度增加;风向变得单一,风速减小;土壤温度降低和土壤湿度增加。