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排序方式: 共有3044条查询结果,搜索用时 265 毫秒
941.
942.
Yunjun Yao Yuhu Zhang Shaohua Zhao Xianglan Li Kun Jia 《Environmental monitoring and assessment》2015,187(6):382
We have evaluated the performance of three satellite-based latent heat flux (LE) algorithms over forest ecosystems using observed data from 40 flux towers distributed across the world on all continents. These are the revised remote sensing-based Penman-Monteith LE (RRS-PM) algorithm, the modified satellite-based Priestley-Taylor LE (MS-PT) algorithm, and the semi-empirical Penman LE (UMD-SEMI) algorithm. Sensitivity analysis illustrates that both energy and vegetation terms has the highest sensitivity compared with other input variables. The validation results show that three algorithms demonstrate substantial differences in algorithm performance for estimating daily LE variations among five forest ecosystem biomes. Based on the average Nash-Sutcliffe efficiency and root-mean-squared error (RMSE), the MS-PT algorithm has high performance over both deciduous broadleaf forest (DBF) (0.81, 25.4 W/m2) and mixed forest (MF) (0.62, 25.3 W/m2) sites, the RRS-PM algorithm has high performance over evergreen broadleaf forest (EBF) (0.4, 28.1 W/m2) sites, and the UMD-SEMI algorithm has high performance over both deciduous needleleaf forest (DNF) (0.78, 17.1 W/m2) and evergreen needleleaf forest (ENF) (0.51, 28.1 W/m2) sites. Perhaps the lower uncertainties in the required forcing data for the MS-PT algorithm, the complicated algorithm structure for the RRS-PM algorithm, and the calibrated coefficients of the UMD-SEMI algorithm based on ground-measured data may explain these differences. 相似文献
943.
本文通过梳理我国污染源监管的历史沿革和日益严峻的环境污染问题,理清我国现阶段在污染源整个生命周期的不同阶段由不同环境部门主导的污染源监管模式和在此模式下形成的数出多源的数据库基本情况。从时间、空间、参与者三个角度分析该模式的缺点,针对环境统计、排污申报、排污收费等多个污染源数据库进行分析比较,列表找出各自数据的特点。通过分析指出我国污染源管理存在的不足,主要体现在污染源信息管理碎片化、多元化,数据互通性差,难以实现交换和共享,导致环境部门数据可靠性不高,信息公开不全面,社会公信力缺失。究其根本原因是我国目前缺乏一整套统一的、紧密衔接的污染源协同监管模式以及顺畅的污染源全过程管理数据流程。文章从实行排污许可证一证式管理制度、污染源企业报告制度、信息公开制度、加强违法处罚力度和完善企业环境信用等方面提出政策建议。 相似文献
944.
Yongmei Ma Zhongmin Jia Siyue Li 《Environmental science and pollution research international》2017,24(25):20282-20290
Assessment of heavy metal (HM) pollution in soil is critical for human health, ecological remediation, and soil conservation. In this study, statistical analyses and geochemical approaches such as enrichment factor (EF), the index of geoaccumulation (Igeo), and potential ecological risk index (RI) were used for characterization and risk assessment of soil HMs through a high-spatial-resolution 385 samples from Tongnan District, an important agricultural practice area in Chongqing Municipality in Southwest China. Igeo and EF indicated that Hg and Cd could be considered as low and moderate polluted, respectively, and others HMs were not a major concern. Comprehensive ecological risk information further demonstrated that the HMs have caused a moderate risk. Principal component analysis (PCA) extracted two principal components (PCs) with eigenvalue >1 explaining about 66.1% of the total variance in the HM data sets, demonstrating major source of anthropogenic activity, phosphate fertilizers, vehicle, and pesticides. These multi-index methods have the capacity of HM assessment in soil, which are useful for soil conservation and ecological remediation. 相似文献
945.
The extensive reclamation of marshland into cropland has tremendously impacted the ecological environment of the Sanjiang Plain in northeast China. To understand the impacts of marshland reclamation and restoration on soil properties, we investigated the labile organic carbon fractions and the soil enzyme activities in an undisturbed marshland, a cultivated marshland and three marshlands that had been restored for 3, 6 and 12?years. Soil samples collected from the different management systems at a depth of 0-20?cm in July 2009 were analyzed for soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) and easily degradable organic carbon. In addition, the activities of the invertase, β-glucosidase, urease and acid phosphatase were determined. These enzymes are involved in C, N and P cycling, respectively. Long-term cultivation resulted in decreased SOC, DOC, MBC, microbial quotient and C (invertase, β-glucosidase) and N-transforming (urease) enzyme activities compared with undisturbed marshland. After marshland restoration, the MBC and DOC concentrations and the soil invertase, β-glucosidase and urease activities increased. Soil DOC and MBC concentrations are probably the main factors responsible for the different invertase, β-glucosidase and urease activities. In addition, marshland restoration caused a significant increase in the microbial quotient, which reflects enhanced efficiency of organic substrate use by microbial biomass. Our observations demonstrated that soil quality recovered following marshland restoration. DOC, MBC and invertase, β-glucosidase and urease activities were sensitive for discriminating soil ecosystems under the different types of land use. Thus, these parameters should be considered to be indicators for detecting changes in soil quality and environmental impacts in marshlands. 相似文献
946.
将粉煤灰(fly ash,FA)微波辐照制得微波改性粉煤灰(MFA),选择用H2SO4、NaOH和Ca(OH)2对MFA进行化学改性制得微波化学改性粉煤灰(MMFA),结果表明,用2 mol/L NaOH并按与MFA的质量体积比为1∶4制得的MMFA对Cr6+的吸附去除效果最好,与原灰相比,去除率显著增强。研究了NaOH改性MMFA对废水中Cr6+的吸附性能。动力学研究结果表明,MMFA对Cr6+的吸附动力学符合二级吸附动力学速率方程,吸附受颗粒内扩散过程控制。热力学研究结果表明,在25、35和45℃下MMFA对Cr6+的等温吸附行为均可用Langmuir方程、Freundlich方程和线性方程描述,所得热力学参数吸附自由能(ΔG)、吸附焓(ΔH)和吸附熵(ΔS)均为负值,说明MMFA对Cr6+的吸附过程为自发进行的放热吸附过程。 相似文献
947.
亚甲基蓝在污泥活性炭上的吸附 总被引:5,自引:2,他引:3
以剩余污泥为原料,氯化锌为活化剂制备污泥活性炭。研究了初始pH值、吸附温度及离子强度对污泥活性炭吸附亚甲基蓝效果的影响。采用高分辨电子扫描电镜(SEM)和氮吸脱附曲线对污泥活性炭进行了表征。结果表明,随着pH值的升高,吸附量增大,碱性条件下最好。在15~55℃的范围内,亚甲基蓝的吸附量先增加后降低,温度为35℃时吸附量达到最大值。加入氯化钠后的污泥活性炭的吸附能力变弱,但随着离子强度的增大,变弱的强度减少。污泥活性炭以中孔为主和污泥活性炭具有不规则结构,预示着污泥活性炭较高的吸附能力。污泥活性炭对亚甲基蓝的吸附符合Lang-muir等温吸附方程。污泥壳活性炭对亚甲基蓝的吸附符合二级反应动力学方程反应特征。 相似文献
948.
基于地学信息图谱的合肥市城市扩展时空特征及驱动力分析 总被引:4,自引:0,他引:4
利用多时相遥感影像,借助ArcGIS平台,采用空间形态分析、等扇分析、等距分析及分形分析等方法,以城市扩展强度、紧凑度、分形维数、重心坐标、扩展弹性系数等为指标,基于地学信息图谱分析了1987~2011年合肥市城市扩展时空特征及其驱动力。结果表明:合肥市在经历了轴向放射状扩展、双核组团扩展及轴间填充后,城市形态由不规则团块状向星楔形、连体双星形转变;24 a间,城市用地面积增长了22415 km2,城市规模扩大了455倍;2000年以前基本保持中、低速扩展,进入21世纪后,开始高速扩展;城市空间主要沿交通线向西南、东南、东、东北等方向非均衡延展,城市扩展最强烈的区域约在距城区中心8 km处,城市重心不断向南偏西方向转移;扩展过程中,城市紧凑度呈“W”型波动,分形维数呈“M”型波动,扩展弹性系数呈“∧”型波动,城市形态最终向着稳定、合理化方向发展;自然环境、经济发展、人口增长、交通建设、政府行为等是合肥市城市扩展的主要驱动力量 相似文献
949.
淄博市重点工业行业VOCs排放特征 总被引:10,自引:9,他引:1
为研究淄博市重点工业行业的VOCs排放特征,筛选出9个重点行业,选择各行业代表性企业进行实地调研和采样,分析了不同行业的VOCs排放特征,通过实测法计算了各企业的VOCs排放量,并在此基础上得到本地化排放因子.结果表明,不同行业的VOCs排放特征存在一定差异,多数行业以烷烃、卤代烃为主;乙烷、乙炔、氯乙烷类(包括1,1-二氯乙烷、 1,1,1-三氯乙烷)以及氟利昂类(氟利昂12或氟利昂114)为大多数行业均含有的主要特征物种;分环节排放量计算结果显示,设备动静密封点泄漏、有机液体装卸挥发损失、有机液体储存与调和挥发损失以及工艺有组织排放为不同类型石化行业的VOCs主要排放环节,排放量占比均达到40%以上;合成橡胶与炼钢行业的VOCs本地化排放因子与已有规范中的推荐值相近,其余行业则存在较大差距. 相似文献
950.