西安市汽车站地表灰尘中重金属的污染评价及其来源识别

[目的]研究西安市长途汽车站地表灰尘中重金属的主要成分、可能来源及其污染水平,为改善汽车站内及周边环境现状提供科学依据。[方法]利用X-Ray荧光光谱仪对西安市内20个具有代表性的汽车站地表灰尘中Cu,Mn,Ni,Pb,V和Zn的元素含量进行分析,采用地积累指数法及潜在生态风险指数法评价灰尘重金属的污染水平及环境风险,利用主成分分析。聚类分析等方法来研究城市汽车站地表灰尘中重金属的主要成分及其可能来源。[结果]Cu,Pb,Zn均在不同程度上超过陕西省土壤背景值,其含量的平均值分别为36.3,107.7,113.5mg/kg。地积累指数法评价表明,除Pb为中度污染以外,其余元素均为无污染;潜在生态风险指数法表明,西安汽车站地表灰尘中的重金属元素处于中等污染水平,具有中等潜在生态风险。[结论]Cu,Mn和Ni主要来自于自然源和交通源,Pb和Zn主要来自汽车尾气的排放及零部件的磨损,V则主要来自于自然源。     

叶面滞尘对火电厂周边绿化树种叶片反射光谱及光合作用的影响

以宁东能源化工基地典型火电厂周边5种常见绿化树种白蜡、臭椿、火炬树、山槐、榆树的叶片为对象，并在雨后第1天和第15天分别采用洗脱法分析其滞尘能力，地物光谱仪测定滞尘对叶面反射光谱的影响，Li-6400便携式光合仪测定滞尘对光合特征参数（净光合速率、气孔导度和蒸腾速率）的影响。结果表明，5种绿化树种的滞尘能力由大到小表现为:火炬树、臭椿、榆树、山槐、白蜡。光谱反射曲线总体特征是洁净叶片反射率大于滞尘叶片反射率，主要表现在740~1 300 nm波段，而在350~680、1 500~2 500 nm波段，则无一致性规律，存在波动。叶面滞尘量与叶片光谱反射率相关性研究表明对叶面滞尘敏感的波段主要集中在可见光波(700~750 nm)和近红外波段(1 390~1 500 nm)。滞尘不改变叶面特有的反射特征，但存在增强或削弱效果，且这种增强或者削弱效果存在种间差异。滞尘对叶片反射光谱曲线一阶导数的三边位置没有明显影响，说明三边位置对滞尘的干扰不敏感；三边幅值和三边面积对滞尘有明显的响应，5种绿化树种均表现为洁净叶片大于滞尘叶片。在相同的污染环境下，滞尘会对绿化树种的光合生理特征产生抑制作用，但并非滞尘量越大、光合特征损失率越大，而损失的幅度因植物种类的不同而异，存在种间差异。综合各树种受滞尘影响的光合特征参数变化，发现榆树和山槐对当地大气降尘污染的抗性较强。     

Separating emitted dust from the total suspension in airflow based on the characteristics of PM10 vertical concentration profiles on a Gobi surface in northwestern China

During aeolian processes, the two most critical factors related to dust emissions are soil particle and aggregate saltation, which greatly affect the vertical profiles of near-surface dust concentrations. In this study, we measured PM10 concentrations at four different heights (0.10, 0.50, 1.00 and 2.00 m) with and without continuous and simultaneous aeolian saltation processes on a Gobi surface in northwestern China from 31 March to 10 April, 2017. We found that the vertical concentration profiles of suspended PM10 matched the log-law model well when there was no aeolian saltation. For the erosion process with saltation, we divided the vertical concentration profiles of PM10 into the saltation-affected layer and the airflow-transport layer according to two different dust sources (i.e., locally emitted PM10 and upwind transported PM10). The transition height between the saltation-affected layer and the airflow-transport layer was not fixed and varied with saltation intensity. From this new perspective, we calculated the airflow-transport layer and the dust emission rate at different times during a wind erosion event occurred on 5 April 2017. We found that dust emissions during wind erosion are primarily controlled by saltation intensity, contributing little to PM10 concentrations above the ground surface compared to PM10 concentrations transported from upwind directions. As erosion progresses, the surface supply of erodible grains is the most crucial factor for saltation intensity. When there was a sufficient amount of erodible grains, there was a significant correlation among the friction velocity, saltation intensity and dust emission rate. However, when supply is limited by factors such as surface renewal or an increase in soil moisture, the friction velocity will not necessarily correlate with the other two factors. Therefore, for the Gobi surface, compared to limiting dust emissions from upwind directions, restricting the transport of suspended dust in its path is by far a more efficient and realistic option for small areas that are often exposed to dust storms. This study provides some theoretical basis for correctly estimating PM10 concentrations in the Gobi areas.     

蔺草固色用染土改性及粉尘污染控制研究

利用纳米TiO2、叶绿素添加剂、分散剂等有效成分对蔺草固色所用日本染土进行改性处理,在不影响原有固色工艺及固色效果前提下,可使改性后染土的实际用量在目前蔺草固色工艺的基础上降低70%左右,从而降低了固色成本。同时,通过控制染土的实际用量,使作业环境中粉尘浓度在现有基础上降低62%左右,粉尘中游离S iO2含量降低60%左右,从而使蔺草作业环境中的粉尘污染得到有效控制,工作环境得到改善。     

Soil pH changes induced by contamination by magnesium oxides dust

In this paper we evaluate the environmental impact of dust emission from a magnesite calcination factory during the last 40 years over an area of about 600 ha in northern Spain. Our study aimed to determine the contamination levels through the spatial modifications induced on the soil pH by deposition of the dust, mostly composed of magnesium oxides. A soil survey of the area has been conducted by collecting soil samples at three different depths (0–2, 2–32 and 32–52 cm) following a square grid pattern. Our survey has evidenced an important and general pH increase of the soils. Thus, from original values of around 7, pH reaches alkaline values of above 9·5. IDRISI GIS techniques have been used to analyse and represent the spatial distribution of the pH values. Variations in the expected concentric circular pattern of soil pH distribution appear to be related to climatic factors, such as precipitation, wind direction and intensity. Also topography affects pH distribution through its ‘screen’ effect. The contamination levels in the area have a strong environmental impact responsible for the abandonment of some agricultural lands. Copyright © 2000 John Wiley & Sons, Ltd.