A Study of Airborne Selected Metals and Particle Size Distribution in Relation to Climatic Variables and their Source Identification

Ten selected metals (Na, K, Fe, Zn, Pb, Mn, Cr, Co, Ni & Cd) were estimated in total suspended particulate (TSP) samples collected on glass fibre filters in urban Islamabad, Pakistan, from October 2002 to May 2003, using a high volume sampling technique. The wet digestion method (HNO₃/HClO₄) was used for metal analysis by the flame atomic absorption spectrophotometry (FAAS) method. Maximum mean contribution was noted for Na (1.949 μg m^?3), followed by K (0.900 μg m^?3), Zn (0.603 μg m^?3), Fe (0.584 μg m^?3) and Pb (0.214 μg m^?3). The particle size determination on % volume basis for four fractions (PM_{< 2.5}, PM_2.5–10, PM_10–100& PM_{> 100}) was also carried out. PM_10–100 were found to be the most abundant in the local atmosphere followed by PM_2.5–10, while the respirable fraction (PM_{< 2.5}) and giant fraction (PM_{> 100}) showed comparable and lower levels. The trace metals were found to be mainly associated with PM_{< 2.5} and PM_2.5–10. The influence of climatic variables on toxic trace metals and particle size fractions was also investigated statistically and it was revealed that temperature has a significant correlation with fine particle fractions and airborne trace metal levels. The source identification was carried out by Principal Component Analysis and Cluster Analysis. Four metal sources were identified: industrial (32.6%), soil-derived dust (21.9%), traffic/road dust (19.8%), and metallurgical/garbage incineration (12.4%). The metal levels were also compared with those reported for other parts around the world.     

塔里木河流域水文过程的特点初探

根据1957-2003年塔里木河流域气温、源干流水文资料，对塔里木河流域基本水文过程，山区降水和温度变化、源流区来水情况以及干流区各段水资源消耗进行分析，试图对近50年来塔里木河流域水文过程的特点进行初步分析和讨论。结果显示：塔里木河流域特殊的自然条件造成流域径流的形成区与水资源开发利用区，水资源荒漠平原消耗区相分离，而由于全球气候的变化。山区温度升高和降水增加，源流区径流量大幅增加，其中对干流影响最大的阿克苏河近10年进入特丰来水时期；但是，塔里木河干流来水量并未增加反而呈现微递减的走势，随着干流上游段耗水量的不断增加，塔里木河中下游生态环境明显退化。     

基于LMDI模型的黄河中游城市群水土资源利用影响因素分析

[目的]水土资源是城市发展的重要生产要素,是探索黄河中游城市群水土资源利用过程中的关键因素,对科学促进黄河中游城市群经济快速发展具有重要意义。[方法]以黄河中游三大城市群为例,通过运用LMDI加法模型对2010—2019年黄河中游三大城市群分别构建影响水资源消耗量变化及城市建设用地数量变化的因素分解模型,计算并比较不同驱动因素的效应值。[结果](1)水资源利用效率提高和产业结构的优化能够抑制水资源消耗量的增加,而经济规模和人口规模扩大则促进其增加。(2)产业规模、经济规模及人口规模扩大对建设用地扩张存在推动作用,而城市建设用地消耗强度对建设用地扩张具有抑制作用。(3)对于水资源利用量变化,黄河中游不同城市之间产业结构优化水平存在较大差距;对于城市建设用地变化,三大城市群总效应值比较结果为关中平原城市群>中原城市群>晋中城市群。[结论]基于区域差异和时间差异角度探讨黄河中游城市群水土资源利用的影响因素,有助于丰富水土资源可持续利用的相关研究,为黄河中游城市群的可持续发展提供理论指导。     

径流季节变化对清水河河道生态环境需水量的影响

[目的] 估算清水河河道生态环境需水量,为保证清水河发挥其正常生态功能以及流域内水资源的合理配置提供依据。[方法] 通过对清水河流域用水情况实地调查,在分析整理多年水文统计资料的基础上,考虑生态用水安全,根据清水河径流随降水时间的季节性变化特点以及流域多年水文变化特征,在空间上选取清水河干流的不同断面计算河道生态环境需水量。针对需要满足河流不同生态功能要求,分别采用Tennant法、面积定额法,90%保证率最枯月水量法等方法计算河道基础生态需水量、蒸发需水量、输沙需水量以及水体自净需水量。[结果] 清水河河道生态环境需水量包括基础生态需水量、蒸发需水量、输沙需水量及水体自净需水量,年需水总量上游段为6.29×10⁶ m³,中游段为6.57×10⁷ m³,下游段为1.65×10⁸ m³。[结论] 清水河河道生态环境需水量与泥沙含量和水质有直接关系。泥沙含量高是清水河河道生态环境需水量高的最主要因素。     

2010年汾河流域土地退化经济损失评估

土地退化是汾河流域严重的生态环境问题,直接关系到全流域社会经济的可持续发展。以实地调查为基础,结合已有的文献资料和汾河流域环境特征,运用生态经济损益核算方法,分析了汾河流域土地退化状况和变化趋势,估算了2010年汾河流域土地退化的经济损失。结果表明:(1)2010年汾河流域土地退化的经济损失高达3.83×109元,其中水土流失的经济损失最大(占61.79%),为2.37×109元,沙漠化、盐渍化的经济损失分别为2.31×108和1.23×109元。(2)2010年汾河流域土地退化的经济损失约占全流域GDP的0.77%(上游占1.45%),上游地区是土地退化的重点治理区;占第一产业产值的14.58%,影响着流域可持续发展能力;土地退化的经济损失人均负荷值为290.08元/人,制约着流域人民的脱贫致富,因此,应加强对土地退化的治理。     

Experimental Warming Aggravates Degradation‐Induced Topsoil Drought in Alpine Meadows of the Qinghai–Tibetan Plateau

Climatic warming is presumed to cause topsoil drought by increasing evapotranspiration and water infiltration, and by progressively inducing land degradation in alpine meadows of the Qinghai–Tibetan Plateau. However, how soil moisture and temperature patterns of degraded alpine meadows respond to climate warming remains unclear. A 6‐year continuous warming experiment was carried out in both degraded and undegraded alpine meadows in the source region of the Yangtze River. The goal was to identify the effects of climatic warming and land degradation on soil moisture (θ ), soil surface temperature (T _sfc ), and soil temperature (T _s ). In the present study, land degradation significantly reduced θ by 4·5–6·1% at a depth of 0–100 cm (p  < 0·001) and increased the annual mean T _sfc by 0·8 °C. Warming with an infrared heater (radiation output of 150 W m⁻²) significantly increased the annual mean T _sfc by 2·5 °C (p  < 0·001) and significantly increased θ by 4·7% at a depth of 40–60 cm. Experimental warming in degraded land reversed the positive effects of the infrared heater and caused the yearly average θ to decrease significantly by 3·7–8·1% at a depth of 0–100 cm. Our research reveals that land degradation caused a significant water deficit near the soil surface. Experimental warming aggravated topsoil drought caused by land degradation, intensified the magnitude of degradation, and caused a positive feedback in the degraded alpine meadow ecosystem. Therefore, an immediate need exists to restore degraded alpine meadow grasslands in the Qinghai–Tibetan Plateau in anticipation of a warmer future. Copyright © 2017 John Wiley & Sons, Ltd.     

Influence of Saharan Dust Transport Events on PM2.5 Concentrations and Composition over Athens

The evaluation of the contribution of natural sources to PM₁₀ and PM_2.5 concentrations is a priority especially for the countries of European south strongly influenced by Saharan dust transport events. Daily PM_2.5 concentrations and composition were monitored at an urban site at 14 m above ground level, at the National Technical University of Athens campus from February to December 2010. The typical dust constituents Si, Al, Fe, K, Ca, Mg, and Ti were determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF). Sulfur, a tracer of anthropogenic origin and major constituent of PM_2.5, was determined by both WDXRF and ionic chromatography. The contribution of dust and sulfates in PM_2.5 was calculated from the analytical determinations. An annual mean of 20 μg/m³ was calculated from the mean daily PM_2.5 concentrations data. Twenty-two per cent of daily concentrations of PM_2.5 reached or exceeded the EU annual target concentration of 25 μg/m³. The exceedances occurred during 13 short periods of 1–4 days. Back-trajectory analysis was performed for these periods in order to identify the air masses origin. From these periods, ten periods were associated to Saharan dust transport events. The most intense dust transport event occurred between February 17th and 20th and was responsible for the highest recorded PM_2.5 concentration of 100 μg/m³ where the dust contribution in PM_2.5 reached 96 %. The other dust transport events were less intense and corresponded to less pronounced enhancements of PM_2.5 concentrations, and their contribution ranged from 15 to 39 % in PM_2.5 concentrations. Air masses originated from northwest Africa while the influence of central Sahara was quite smaller.     

黑河中游不同生计方式农户的水足迹分析

水资源紧缺问题是21世纪人类面临的最严峻生态环境问题之一,当前急需探寻影响水资源利用的关键因素,建立低水消费模式。生计方式作为影响家庭水资源消费的关键要素已得到关注。本文基于农户调查数据,利用水足迹估算模型,核算黑河流域中游不同生计方式农户的水足迹,并采用最小二乘法分析了生计方式对水足迹的影响。结果表明:①黑河中游农户的人均水足迹为145.87 m3,随着非农化水平的提高,农户的人均水足迹下降,其中,纯农户、兼业户和非农户的人均水足迹分别为151.61 m3、148.08 m3和137.91 m3;②随着非农化水平的提高,黑河中游纯农户、兼业户、非农户的人均粮食消费占用水足迹比例依次降低,农户人均果蔬、清洁消费占用水足迹比例依次增高,兼业户的人均畜产品消费占用水足迹比例高于非农户和纯农户;③提高非农化水平和劳动力受教育水平可以减少水足迹,扩大家庭规模和农户人均纯收入会增加农户的水足迹,但水足迹的增加速度低于家庭规模和人均纯收入自身的增加速度。基于上述研究结果,提出了对黑河中游地区农村建立低水模式,提高水资源利用效率的对策建议。     

Spatio‐Temporal Patterns of Land Use/Cover Changes Over the Past 20 Years in the Middle Reaches of the Tarim River,Xinjiang, China

The interaction between land use/cover change and landscape pattern is pivotal in research concerning global environmental change. This study uses three different Landsat images of 1989, 1998 and 2009 to study the land use/cover and landscape pattern changes in the middle reaches of the Tarim River basin. envi ®, erdas ®, ArcGIS ® and fragstats ® software were used to analyse the land use/cover changes. The objectives of study were to map and study the changes in land use/cover and landscape pattern, and propose some possible factors in making the land use/cover changes from 1989 to 2009. Seven different types of land use/cover are analysed, and the results are listed in tables. From 1989 to 1998, the percentage of farmland, slight–moderate saline land, heavy saline land and water areas have increased; woodland, desert and the undeveloped land have decreased. From 1998 to 2009, farmland, heavy saline land and the undeveloped land have increased; the other types of land use/cover have decreased. The gravity centre of each land use/cover types has shifted. The farthest shifting of the gravity centre was heavy saline land, which occurred between 1989 and 1998. The transformation and changes of land use/covers and landscape occurred more frequently from 1989 to 2009. Other types of land use and land cover changes to saline land have increased, which implied that a serious salinization took place in the Tarim Basin. The results from this study would show the adverse environmental changes (e.g. salinization and desertification) and they can be used for future sustainable management of land resources. Copyright © 2013 John Wiley & Sons, Ltd.     

Atmospheric Emission Inventory for Natural and Anthropogenic Sources and Spatial Emission Mapping for the Greater Athens Area

A spatially, temporally and chemically resolved emission inventory for particulate matter and gaseous species from anthropogenic and natural sources was created for the Greater Athens Area (GAA; base year, 2007). Anthropogenic sources considered in this study include combustion (industrial, non-industrial, commercial and residential), industrial production, transportation, agriculture, waste treatment and solvent use. The annual gaseous pollutants (????x, SOx, non-methane volatile organic compounds (NMVOCs), CO and ????₃) and particulate matter (PM_2.5 and PM_2.5?C10) emissions were derived from the UNECE/EMEP database for most source sectors (SNAP 1?C9; 50?×?50 km²) and their spatial resolution was increased using surrogate spatial datasets (land cover, population density, location and emissions of large point sources, emission weighting factors for the GAA; 1?×?1 km²). The emissions were then temporally disaggregated in order to provide hourly emissions for atmospheric pollution modelling using monthly, daily and hourly disintegration coefficients, and additionally the chemical speciation of size-segregated particles and NMVOCs emissions was performed. Emissions from agriculture (SNAP 10) and natural emissions of particulate matter from the soil (by wind erosion) and the sea surface and of biogenic gaseous pollutants from vegetation were also estimated. During 2007 the anthropogenic emissions of CO, SOx, NOx, NMVOCs, NH₃, PM_2.5 and PM_2.5?C10 from the GAA were 151,150, 57,086, 68,008, 38,270, 2,219, 9,026 and 3,896 Mg, respectively. It was found that road transport was the major source for CO (73.3%), NMVOCs (31.6%) and NOx (35.3%) emissions in the area. Another important source for NOx emissions was other mobile sources and machinery (23.1%). Combustion for energy production and transformation industries was the major source for SOx (38.5%), industrial combustion for anthropogenic PM_2.5?C10 emissions (59.5%), whereas non-industrial combustion was the major source of PM_2.5 emissions (49.6%). Agriculture was the primary NH₃ source in the area (72.1%). Natural vegetation was found to be an important source of VOCs in the area which accounted for approximately the 5% of total VOCs emitted from GAA on a typical winter day. The contribution of sea-salt particles to the emissions of PM_2.5 was rather small, whereas the emissions of resuspended dust particles exceeded by far the emissions of PM_2.5 and PM_2.5?C10 from all anthropogenic sources.     

塔里木河中游径流变化分析

在多年水文数据的基础上,分析了塔里木河中游1957~2002年间径流年际变化及1992~2002年径流月际变化的特点、趋势及其原因和影响。得出1957~2002年间塔里木河中游径流不稳定、不平衡,并且径流呈逐渐减小的趋势,其主要原因是源流区和上游区大量引水所致;塔里木河径流月际变化呈明显的西北型河流的特点,在7~9月为洪水期,水量可占全年水量的79.31%,4~6月份由于农业用水,导致径流量下降。塔里木河径流的这些特点给水资源管理加大了难度。     

基于RUSLE模型的湟水流域土壤侵蚀时空变化

研究黄河上游土壤侵蚀的时空变化对于维持黄河上游生态系统服务功能、保护黄河上游水塔具有重要意义。以黄河上游典型区域湟水流域为研究区,采用RUSLE模型定量评估了该流域2000—2015年土壤侵蚀的时空变化特征,并分析了有无梯田措施下土壤侵蚀的空间变化,从而量化了梯田建设对防治坡面土壤侵蚀的影响。结果表明:2000—2015年,湟水流域的土壤侵蚀强度整体呈现减小趋势,侵蚀模数由1 183 t/(km~2·a)降低至940 t/(km~2·a),减少幅度为20.54%。不同土地利用类型以及不同坡度下的土壤侵蚀强度均有所降低,其中耕地上的减幅最大为20.58%。15°～20°坡度区间的侵蚀模数减幅最显著,为23.11%。通过有无梯田措施情景模拟发现,湟水流域2015年土壤侵蚀模数由940 t/(km~2·a)降低至有梯田的837 t/(km~2·a),减少11.00%。研究结果可为流域的水土流失防治和生态环境保护提供科学依据。     

基于SWAT和PLUS模型的窟野河流域径流对土地利用变化的响应及预测

[目的]为揭示窟野河流域径流对土地利用变化的响应,并预测未来径流变化。[方法]以窟野河流域为研究区,基于SWAT和PLUS模型,通过2000年、2005年、2010年、2015年、2020年和预测得到的自然发展情景下2025年、2030年7期土地利用数据,定量分析径流在不同土地利用情景下的变化。[结果](1)SWAT模型率定期和验证期的R²和NS均>0.7;PLUS模型总体精度为0.877 4,Kappa系数为0.802 1,2个模型在窟野河流域适用性较好;(2)2000—2020年,窟野河流域林地、建设用地面积分别增加102.92,600.90 km²,耕地、草地、水域和未利用地分别减少277.15,366.25,40.44,19.98 km²;(3)窟野河流域年平均径流深整体呈现“上游低,下游高,西部低,东部高”的空间分布格局;(4)在保证其他输入数据不变的情况下,改变土地利用数据,情景分析结果表明,林地、草地面积减少会促进径流,建设用地面积增加同样会促进径流;(5)自然发展情景下,2025年和2030年窟野河...     

PM10 and PM2.5 Levels in the Eastern Mediterranean (Akrotiri Research Station, Crete, Greece)

Particulate matter measurements (PM₁₀, PM_2.5) using a beta radiation attenuation monitor were performed at the Akrotiri research station (May 2003–March 2006) on the island of Crete (Greece). The mean PM₁₀ concentration during the measuring period (05/02/03–03/09/04) was equal to 35.0?±?17.7 μg/m³ whereas the mean PM_2.5 concentration (03/10/04–04/02/06) was equal to 25.4?±?16.5 μg/m³. The aerosol concentration at the Akrotiri station shows a large variability during the year. Mean concentrations of particulate matter undergo a seasonal change characterised by higher concentrations during summer [PM₁₀, 38.7?±?10.8 μg/m³ (2003); PM_2.5, 27.9?±?8.7 μg/m³ (2004) and 27.8?±?9.7 μg/m³ (2005)] and lower concentrations during winter [PM₁₀, 28.7?±?22.5 μg/m³ (2003/2004); PM_2.5, 21.0?±?13.0 μg/m³ (2004/2005) and 21.4?±?21.9 μg/m³ (2005/2006)]. Comparative measurements of the PM₁₀ concentration between the beta radiation attenuation monitor, a standardized low volume gravimetric reference sampler and a low volume sequential particulate sampler showed that PM₁₀ concentrations measured by the beta radiation attenuation monitor were higher than values given by the gravimetric samplers (mean ratio 1.17?±?0.11 and 1.21?±?0.08, respectively). Statistical and back trajectory analysis showed that elevated PM concentrations (PM₁₀, 93.8?±?49.1 μg/m³; PM_2.5: 102.9?±?59.9 μg/m³) are associated to desert dust events. In addition regional transport contributes significantly to the aerosol concentration levels whereas low aerosol concentrations were observed during storm episodes.     

Effects of land management on CO2 flux and soil C stock in two Tanzanian croplands with contrasting soil texture

Evaluation of carbon dynamics is of great concern worldwide in terms of climate change and soil fertility. However, the annual CO₂ flux and the effect of land management on the carbon budget are poorly understood in Sub-Saharan Africa, owing to the relative dearth of data for in situ CO₂ fluxes. Here, we evaluated seasonal variations in CO₂ efflux rate with hourly climate data in two dry tropical croplands in Tanzania at two sites with contrasting soil textures, viz. clayey or sandy, over four consecutive crop-cultivation periods of 40 months. We then: (1) estimated the annual CO₂ flux, and (2) evaluated the effect of land management (control plot, plant residue treatment plot, fertilizer treatment plot, and plant residue and fertilizer treatment plot) on the CO₂ flux and soil carbon stock at both sites. Estimated annual CO₂ fluxes were 1.0–2.2 and 0.9–1.9 Mg C ha^?1 yr^?1 for the clayey and sandy sites, respectively. At the end of the experiment, crop cultivation had decreased the surface soil carbon stocks by 2.4 and 3.0 Mg C ha^?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively. On the other hand, plant residue application (7.5 Mg C ha^?1 yr^?1) significantly increased the surface soil carbon stocks, i.e., 3.5–3.8 and 1.7–2.1 Mg C ha^?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively, while it also increased the annual CO₂ fluxes substantially, i.e., 2.5–4.0 and 2.4–3.4 Mg C ha^?1 yr^?1 for the clayey and sandy soils, respectively. Our results indicate that these dry tropical croplands at least may act as a carbon sink, though the efficiency of carbon accumulation was substantially lower in sandy soil (6.8–8.4%) compared to clayey soil (14.0–15.2%), possibly owing to higher carbon loss by leaching and macro-faunal activity.     

Greenhouse Gas Emissions following Conversion of a Reclaimed Minesoil to Bioenergy Crop Production

This study provides a comparative assessment of greenhouse gas (GHG) emissions when converting a reclaimed minesoil that was previously under meadow to miscanthus (Miscanthus  × giganteus ) and maize (Zea mays L.) land uses in Ohio, USA. Additionally, effluent from an anaerobic digester at rates of 0, 75, 150, and 225 kg N ha⁻¹ rates was also assessed for C and nutrient fertilization. Results from the study show that land use conversion to maize had the highest net release of GHG equivalent of 6·6 Mg CO_2equ ha⁻¹ y⁻¹, on average, across effluent application rates. Under miscanthus land use with no and high effluent application rates, net GHG equivalent on average was 4·3 Mg CO_2equ ha⁻¹ y⁻¹, which was larger when compared with that under the meadow land use (1·6 Mg CO_2equ ha⁻¹ y⁻¹). Miscanthus land use under medium rates of effluent application had similar net GHG equivalent (7·1 Mg CO_2equ ha⁻¹ y⁻¹) to the maize land use. The application of effluent did increase CO₂–C and N₂O–N emissions; but increases in above‐ground–below‐ground biomass production (1·6 Mg C ha⁻¹) in the meadow land use and C input from effluent retained in the soil in the miscanthus and maize land uses offset most of the effluent‐induced GHG equivalent emissions. Contribution of cumulative N₂O–N to GHG equivalent emissions in general was 11% when no effluent was applied and 22% when effluent was applied across land uses. Findings from this study show that land use changes from antecedent meadow to maize and miscanthus during the first year of establishment would result in net increase of GHG emissions. Published 2017. This article is a U.S. Government work and is in the public domain in the USA     

Influence of the 23 October 2002 Dust Storm on the Air Quality of Four Australian Cities

Widespread drought and record maximum temperatures in eastern Australia produced a large dust storm on 23 October, 2002 which traversed a large proportion of eastern Australia and engulfed communities along a 2000 km stretch of coastline from south of Sydney (NSW) to north of Mackay (Queensland). This event provided an opportunity for a study of the impacts of rural dust upon the air quality of four Australian cities. A simple model is used to predict dust concentrations, dust deposition rates and particle size characteristics of the airborne dust in the cities. The total dust load of the plume was 3.35 to 4.85 million tones, and assuming a (conservative) plume height of 1500 m, 62–90% of this dust load was deposited in-transit to the coast. It is conservatively estimated that 3.5, 12.0, 2.1 and 1.7 kilotonnes of dust were deposited during the event in Sydney, Brisbane, Gladstone and Mackay, respectively. In the South East Queensland region, this deposition is equivalent to 40% of the total annual TSP emissions for the region. The event increased TSP, PM₁₀ and PM_2.5 concentrations and reduced the visibility beyond the health and amenity guidelines in the four cities. For example, the 24-h average PM₁₀ concentrations in Brisbane and Mackay, were 161 and 475 μg m^?3 respectively, compared with the Australian national ambient air quality standard of 50 μg m^?3. The 24-h average PM_2.5 concentration in Brisbane was 42 μg m^?3, compared with the national advisory standard of 25 μg m^?3. These rural dusts significantly increased PM₁₀/TSP ratios and decreased PM_2.5/PM₁₀ ratios, indicating that most of the particles were between PM_2.5 and PM₁₀.     

A Study of PM2.5 and PM2.5-Associated Polycyclic Aromatic Hydrocarbons at an Urban Site in the Po Valley (Bologna, Italy)

PM_2.5 and PAHs bound to PM_2.5 were investigated in downtown Bologna, from January to June 2003, in order to determine the burden of the fine fraction in the aerosol of a typical urban environment of the Po Valley, a critical area in Northern Italy in terms of atmospheric pollution. The sampling campaign was divided into three parts: a winter sub-campaign, an intermediate campaign where PM_2.5 and PM₁₀ were simultaneously sampled and which identified PM_2.5 as the major component of PM₁₀, and a summer sub-campaign. Critical concentrations of both PM_2.5 and PAHs were observed in winter time; for example, in January 2003 the mean value for the 24-h average PM_2.5 concentration was 58 μg/m³, much higher than the annual arithmetic mean of 15 μg/m³ established by the US ambient air quality standard (NAAQS). Correspondingly, the mean value for benzo[a]pyrene (BAP) in PM_2.5 was 1.79 ng/m³, again higher than the annual mean of 1 ng/m³, required by European regulations for BAP in PM₁₀. In summer time the BAP concentration considerably decreases to 0.10 ng/m³ as the likely effect of photolysis and dilution on a higher boundary layer; PM_2.5 decreases too, but the mean concentration (22 μg/m³) is still higher than the NAAQS value. Further analysis included TEM microscopy of collected particles and correlations between PM_2.5, PAHs and gases (benzene, O₃, CO, NO₂, SO₂). All these observations identified on-road mobile sources as the main source of emissions and, in general, of the poor air quality level in the city of Bologna.     

Salinity and sodicity affect soil respiration and dissolved organic matter dynamics differentially in soils varying in texture

The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3–4 times with solutions containing different concentrations of NaCl and CaCl₂ to reach almost identical electrical conductivity (EC_1:5) in both soils (EC_1:5 0.5, 1.3, 2.5 and 4.0 dS m^?1 in the sand and EC_1:5 0.7, 1.4, 2.5 and 4.0 dS m^?1 in the sandy clay loam) combined with two sodium absorption ratios: SAR < 3 and 20. Finely ground wheat straw residue was added (20 g kg^?1) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: ?2.92 MPa in sand (at EC 1.3) and ?2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8–9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR < 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation.     

Boundary conditions of morphodynamic processes in the Mura River in Slovenia

Many alpine gravel-bed rivers have been altered in the past due to human interventions. A typical transboundary alpine river in Central Europe flowing over Austria, Slovenia, Croatia and Hungary is the Mura River (length: 465 km, catchment area: 14,304 km²). The main problem of the river before leaving Austria is bed degradation (average 0.5 m from 1970 to 2000) as a combined consequence of river regulation works and the reduced sediment supply from the upstream reaches due to the construction of hydro power plants. River restoration measures for the river reach on the border between Austria and Slovenia (SLO–A Mura reach) were proposed in 2000 to support both ecological and flood protection purposes that apply the concept “of self-restoration”. In order to apply similar process-oriented restoration strategies in the Mura River downstream in Slovenia, we consider the potentials for self-forming river processes. We have analysed the sediment granulometry and morphology of the Mura River in Slovenia, and discussed morphodynamic processes to detect potential for the Mura River recovery into a more diverse morphological structure. The cross section area increased by 8% between 1979 and 2005 on average, mainly due to riverbed degradation. On average, the thalweg of the Mura riverbed in Slovenia had degraded by 0.28 m in the 1979–2007 period, with the highest degradation of 2.28 m in one cross section and some cross sections being stable. The high river degradation trend from the SLO–A Mura reach is slowly shifting to the downstream direction into the Mura River in Slovenia. Nevertheless, the clear downstream coarsening of river sediments turns into the normal trend of sediment fining in the Mura River reach in Slovenia. The “self-restoration” potential in the Mura River reach in Slovenia is larger than on the SLO–A Mura reach due to still active morphological fluvial processes. These processes can be enhanced by the inflow of fresh coarse sediments from the SLO–A Mura reach, where active measures for re-establishing sediment transport are under way. In the long term, this will not work as proposed, if no sediment inflow is re-established from the Mura headwaters in Austria.