基于聚类分析的北京市空气质量时空分布研究

对北京市空气质量时空分布的研究已比较丰富,但仍缺少对北京市不同区域大气污染物变化相似性的研究.在分析北京市2018年空气污染物时空分布特征的基础上,得出污染物浓度在空间上呈现出北低南高的趋势,自然因素是造成该趋势的主要原因.分别从污染物浓度值和空气质量等级天数2个角度对北京市的大气监测站点进行聚类分析,根据2种聚类结果...     

山地土壤—植物系统中汞污染问题的初步调查

调查研究表明：在山地大气、水体质量较好的环境中,柑橘（含汞量）有超标问题,其土壤汞有超背景值现象;而蔬菜土壤则无此问题,其原因可能是由于多年生植物从大气和土壤中富积微量汞的时间较一年生植物长,以及土壤中砂粒结合汞粘粒结合汞具有更高的生物活性     

渡口地区大气监测的时空分布

一、引言为完成大气监测任务,人们希望通过短时间间隔乃至连续采样、获得好的时间分辨率;通过密集布点获得好的空间分辨率。但现有的人力、物力、财力不容许我们维持多点连续采样。于是研究大气监测的时空分布成为监测的首要任务。它应与研究样品采集,保存及分析方法一样,受到人们重视。从本质讲,监测数据的代表性,首先取决于样品的时空代表性。     

四川省环境中的汞

本文较系统地报道了四川省地面水环境（河，湖原水，过滤水，沉积物），土壤，大气降水及生物－鱼体中的含量及分布特点，得出四川省环境中的汞与国内外相比属于罗低水平，地面水环境中汞的含量及溶解态汞由川东南向川西北递减，土壤中汞的含量与土壤类型，成土母质，降水条件等相关，鱼类对河水中汞有较强的富集能力，大气降水是四川省环境中汞的来源之一。文章还研究了汞的水环境容量，指出汞是四川省水环境较为脆弱的重要因素之一     

水体汞光还原研究进展

汞的光还原是影响水生系统汞迁移转化的重要过程.光还原产生的溶解性气态汞会通过水气界面向大气挥发.该过程可以减轻水体汞负荷,降低汞被甲基化的风险,对全球汞循环具有重要意义.水生系统中汞的光还原过程十分复杂,影响因素较多,是汞环境地球化学行为研究的重点和热点.目前科学家在这方面已做了大量研究,但许多结论与建议还存在争议,对其还原机制也还不清楚.本文总结了近年来水体汞光还原过程的研究进展;分析了水生系统中影响汞光还原过程的主要因素;评述了水汞光还原研究存在的问题;提出了水体汞光还原的研究焦点与方向.     

乌鲁木齐河地区土埌中汞的含量水平

汞是人们重视的环境污染物。汞元素在各自的自然地理环境中,在三相间不断的循环转化,同时由于人类的工农业生产活动,有意无意地使汞进入环境,污染大气、水体及土壤。本文主要是探讨乌鲁木齐河地区(简称乌河地区)土壤中汞的含量水平,为此,研究了乌河地区土壤中汞的背景值,并在工业集中的乌鲁木齐市区采集表层土壤,研究乌市土壤中汞的污染程度,作为评价坏境质量提供依据。     

中美贸易模式变化对中国大气汞排放的影响

在全球贸易体系中,美国是中国大气汞排放的主要外部消费驱动力之一。现有研究多核算国际贸易驱动的大气汞排放,识别主要的贸易驱动关系,缺乏中美贸易模式变化对中国大气汞排放的影响分析。本文基于环境扩展型投入产出模型和结构分解分析方法,计算了1997—2017年中美贸易驱动的中国大气汞排放量,并深入分析了贸易相关的社会经济因素对中国大气汞排放变化的相对贡献。研究结果表明:1997—2007年,中美贸易驱动的中国大气汞排放从13.5 t增至32.8 t,2007年后开始回落,2017年回落至13.6 t。贸易规模扩大是推动大气汞排放增加的最主要因素(62.6 t),排放强度降低是大气汞排放减少的最大驱动因素(-67.0 t)。生产技术水平变化和贸易结构变化的贡献相对较小,近年来逐渐起到促进大气汞排放减少的作用,但其贡献不稳定。根据研究结果,提出了加快产业创新升级,优化、稳定贸易结构,提升产品竞争力等建议。     

土-气界面汞交换特征研究进展

本文综述了20多年来汞在土壤-大气界面间交换的研究现状,包括汞在大气和土壤中的存在形态、大气汞的干湿沉降、土壤汞释放及影响因素的研究,分析其存在的问题,并提出了未来的研究重点。     

绵阳市大气降水pH值时空分布及酸雨成因研究

通过对绵阳市9个测点1998－1999年大气降水监测数据的统计分析，并结合历史数据，对大气降水pH值的时空分布及酸雨成因进行了研究。结果表明：绵阳市大气降水酸化严重，除主要受本地区大气污染影响外，还受大气中、长距离输送的影响。     

大连市大气中气态总汞的时间分布特征研究

为研究大连市大气中气态总汞的时间分布特征,采用Lumex RA-915AM型测汞仪对大连市气态总汞进行了长达一年(2015年)的连续监测。结果表明:2015年大连市气态总汞年平均值为3.72 ng/m3;季节浓度高低顺序为春季夏季冬季秋季;月均值最大值出现在夏季,日均值最大值出现在春季;春季气态总汞浓度白天明显高于夜间,而夏季则白天明显低于夜间,秋季、冬季白天与夜间气态总汞浓度没有明显差别。     

The Water‐Year Water Balance of the Colorado River Basin

Model‐estimated monthly water balance components (i.e., potential evapotranspiration, actual evapotranspiration, and runoff (R)) for 146 United States (U.S.) Geological Survey 8‐digit hydrologic units located in the Colorado River Basin (CRB) are used to examine the temporal and spatial variability of the CRB water balance for water years 1901 through 2014 (a water year is the period from October 1 of one year through September 30 of the following year). Results indicate that the CRB can be divided into six subregions with similar temporal variability in monthly R. The water balance analyses indicated that approximately 75% of total water‐year R is generated by just one CRB subregion and that most of the R in the basin is derived from surplus (S) water generated during the months of October through April. Furthermore, the analyses show that temporal variability in S is largely controlled by the occurrence of negative atmospheric pressure anomalies over the northwestern conterminous U.S. (CONUS) and positive atmospheric pressure anomalies over the southeastern CONUS. This combination of atmospheric pressure anomalies results in an anomalous flow of moist air from the North Pacific Ocean into the CRB, particularly the Upper CRB. Additionally, the occurrence of extreme dry and wet periods in the CRB appears to be related to variability of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation.     

Development and application of a laboratory flux measurement system (LFMS) for the investigation of the kinetics of mercury emissions from soils

Recent measurements at different locations suggest that the emission of mercury from soils may play a more pronounced role in the global mercury cycle as suggested by global emission inventories and global mercury cycling models. For up scaling and modelling of mercury emissions from soils a comprehensive assessment of the processes controlling the emission of mercury from soils is imperative. We have developed a laboratory flux measurement system (LFMS) to study the effect of major environmental variables on the emission of mercury under controlled conditions. We have investigated the effects of turbulent mixing, soil temperature and solar radiation on the emission of mercury from soils. The emission of mercury from soils is constant over time under constant experimental conditions. The response of the mercury emission flux to variations of the atmospheric transfer parameters such as turbulence requires a rapid adjustment of the equilibrium that controls the Hg(o) concentration in the soil air. It has been shown that the light-induced flux is independent of the soil temperature and shows a strong spectral response to UV-B.     

Hydroclimatology of the Mississippi River Basin

Model estimated monthly water balance (WB) components (i.e., potential evapotranspiration, actual evapotranspiration, and runoff [R]) for 848 United States (U.S.) Geological Survey 8‐digit hydrologic units located in the Mississippi River Basin (MRB) are used to examine the temporal and spatial variability of the MRB WB for water years 1901 through 2014. Results indicate the MRB can be divided into nine subregions with similar temporal variability in R. The WB analyses indicated ~79% of total water‐year MRB runoff is generated by four of the nine subregions and most of the R in the basin is derived from surplus (S) water during the months of December through May. Furthermore, the analyses showed temporal variability in S is largely controlled by the occurrence of negative atmospheric pressure anomalies over the western U.S. and positive atmospheric pressure anomalies over the eastern U.S. coast. This combination of atmospheric pressure anomalies results in an anomalous flow of moist air from the Gulf of Mexico into the MRB. In the context of paleo‐climate reconstructions of the Palmer Drought Severity Index, since about 1900 the MRB has experienced wetter conditions than were experienced during the previous 500 years.     

城市景观格局与大气颗粒物污染的关系研究

随着城市化和工业化发展,大气颗粒物对城市空气环境造成了严重污染,选取西安市作为研究区,分析不同时间和空间尺度下城市景观格局与大气颗粒物污染的关系。通过GIS软件、Fragstats4.2软件和SPSS软件对西安市2014年土地利用数据和2014年整年的大气颗粒物监测数据进行分析,结果显示,西安市土地利用类型分布较为集中;西安市大气颗粒物浓度的空间分布特征为浓度从市中心至城郊呈梯度递减趋势,在整体上呈现西北高于东南的倾向,大气颗粒物污染物浓度峰值基本都集中出现在建设用地范围内(PM10:102.7μg/m^3;PM2.5:99.7μg/m^3);相关性结果证实了城市景观格局与大气颗粒物浓度的空间分布特征。研究结果为中国西部内陆城市大气颗粒物污染控制、土地利用规划以及生态建设提供参考。     

济南市大气污染时空特征研究

为不断改善济南市大气环境质量,在广泛收集与整理相关资料和数据基础上,基于综合污染指数评价法及Arc-GIS平台空间插值法研究并表征了济南市“十一五”期间大气主要污染物的时、空变化特征及发展趋势;研究结果表明：济南市“十一五”期间大气环境质量变化较大,2007～2009年污染较为严重,之后有所改善;大气污染物浓度呈明显的季节变化特征,冬季污染最严重,夏季空气质量最好;首要污染物为PM10;污染较严重区域集中在济南市东北部地区;其变化原因受地理气候条件、产业结构和能源结构影响较大.该研究方法及结论对其他大中城市大气环境质量时空变化研究具有一定借鉴价值.     

Determination of Frequency for Remeasuring Ground and Vegetation Cover Factor Needed for Soil Erosion Modeling

Determining a remeasurement frequency of variables over time is required in monitoring environmental systems. This article demonstrates methods based on regression modeling and spatio-temporal variability to determine the time interval to remeasure the ground and vegetation cover factor on permanent plots for monitoring a soil erosion system. The spatio-temporal variability methods include use of historical data to predict semivariograms, modeling average temporal variability, and temporal interpolation by two-step kriging. The results show that for the cover factor, the relative errors of the prediction increase with an increased length of time interval between remeasurements when using the regression and semivariogram models. Given precision or accuracy requirements, appropriate time intervals can be determined. However, the remeasurement frequency also varies depending on the prediction interval time. As an alternative method, the range parameter of a semivariogram model can be used to quantify average temporal variability that approximates the maximum time interval between remeasurements. This method is simpler than regression and semivariogram modeling, but it requires a long-term dataset based on permanent plots. In addition, the temporal interpolation by two-step kriging is also used to determine the time interval. This method is applicable when remeasurements in time are not sufficient. If spatial and temporal remeasurements are sufficient, it can be expanded and applied to design spatial and temporal sampling simultaneously.     

Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach

The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research, an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further, remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization and its impact on groundwater system.