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91.
92.
芦溪流域非点源污染物流失的一般规律 总被引:13,自引:2,他引:13
以芦溪小流域为研究对象,监测在自然降雨条件下,不同土地利用类型小区、流域出口的污染物流失情况,研究一次降雨径流过程中非点源污染物流失的一般规律,以及不同前期降雨条件下的污染物流失特征.研究表明:随着前期降雨量的增大,SS的流失明显降低,当试验前5天总降雨量为15、115、161mm时,流域出口的SS流失浓度分别为265.6、145.8和124.2mg/L;流域出口的营养物质与COD受前期降雨条件的影响相对较小,波动幅度不大于±15%.小区试验的结果表明:污染物流失浓度的一般规律为:旱地>居民点>草地>林地>水田.植被覆盖可有效地减少泥沙流失,当植被盖度从50%上升到90%时,泥沙流失浓度可减少80%.土壤背景值是决定TN流失浓度的关键因子,旱地、草地、林地的TN流失浓度与土壤背景值的比值为2.75%、2.79%和2.42%.NO3--N与NH4+-N的流失浓度随植被盖度的增大而增大. 相似文献
93.
HUANG Hong LEE Shun-cheng CAO Jun-ji ZOU Chang-wei CHEN Xin-geng FAN Shao-jia 《环境科学学报(英文版)》2007,19(1):35-43
Quantitative information on mass concentrations and other characteristics, such as spatial distribution, seasonal variation, indoor/outdoor (I/O) ratio, correlations and sources, of indoor and outdoor PM2.5 and elemental components in Guangzhou City were provided. Mass concentration of PM2.5 and elemental components were determined by standard weight method and proton-induced X-ray emission (PIXE) method. 18 elements were detected, the results showed positive results. Average indoor and outdoor PM2.5 concentrations in nine sites were in the range of 67.7-74.5μg/m^3 for summer period, and 109.9-123.7 μg/m^3 for winter period, respectively. The sum of 18 elements average concentrations were 5362.6-5533.4 ng/m^3 for summer period, and 8416.8-8900.6 ng/m^3 for winter period, respectively. Average concentrations of PM2.5 and element components showed obvious spatial characteristic, that the concentrations in roadside area and in industrial plant area were higher than those in generic urban area. An obvious seasonal variation characteristic was found for PM2.5 and elemental components, that the concentrations in winter were higher than that in summer. The I/O ratio of PM2.5 and some elemental components presented larger than 1 sometimes. According to indoor/outdoor correlation of PM2.5 and element concentrations, it was found that there were often good relationships between indoor and outdoor concentrations. Enrichment factors were calculated to evaluate anthropogenic versus natural elements sources. 相似文献
94.
以安徽涡河流域为研究区域,通过采集涡河地表水、浅层地下水和中深层地下水样品,运用Gibbs图、离子比例和MixSIAR模型等方法对各类水体的水化学参数和氢氧同位素进行分析,揭示并量化了各类水体之间的转化关系.结果表明,研究区地表水和地下水主要呈现中性至弱碱性,地表水的水化学类型以Cl·SO4 ·HCO3 -Na和Cl·SO4 -Na型为主,浅层地下水以HCO3 -Ca·Mg和HCO3 -Mg·Na型为主,中深层地下水主要为Cl·HCO3 -Na型.各类水体的水化学特征受到岩石风化、蒸发浓缩及正向阳离子交换等多重因素共同影响.地表水和地下水的δ18O和δ2H分布特征表明大气降水是该区域水体的主要补给来源,且地下水δ18O和δ2H值与K+、Na+、Cl-、SO4 2-和NO 3-浓度存在显著相关性.根据MixSIAR模型分析结果,地表水接受大气降水和浅层地下水的贡献率分别为46.5 %和53.5 %;浅层地下水的补给来源分别为大气降水(57.4 %)和地表水(42.6 %);中深层地下水的补给主要来自上游地下水的侧向径流补给. 相似文献
95.
96.
More than 30 years after it was first proposed as a biodiversity conservation strategy, rewilding remains a controversial concept. There is currently little agreement about what the goals of rewilding are, and how these are best achieved, limiting the utility of rewilding in mainstream conservation. Achieving consensus about rewilding requires agreeing about what “wild” means, but many different definitions exist, reflecting the diversity of values in conservation. There are three key debates that must be addressed to find a consensual definition of “wild”: (1) to which extent can people and “wild” nature co-exist?; (2) how much space does “wild” nature need? and (3) what kinds of “wild” nature do we value? Depending on the kinds of “wild” nature rewilding aims to create, rewilding policy will be faced with managing different opportunities and risks for biodiversity and people.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01560-8. 相似文献
97.
Meiyun Lin Taikan Oki Magnus Bengtsson Shinjiro Kanae Tracey Holloway David G. Streets 《Atmospheric environment (Oxford, England : 1994)》2008,42(24):5956-5967
Region-to-grid source–receptor (S/R) relationships are established for sulfur and reactive nitrogen deposition in East Asia, using the Eulerian-type Community Multiscale Air Quality (CMAQ) model with emission and meteorology data for 2001. We proposed a source region attribution methodology by analyzing the non-linear responses of the CMAQ model to emission changes. Sensitivity simulations were conducted where emissions of SO2, NOx, and primary particles from a source region were reduced by 25%. The difference between the base and sensitivity simulations was multiplied by a factor of four, and then defined as the contribution from that source region. The transboundary influence exhibits strong seasonal variation and generally peaks during the dry seasons. Long-range transport from eastern China contributes a significant percentage (>20%) of anthropogenic reactive nitrogen as well as sulfur deposition in East Asia. At the same time, northwestern China receives approximately 35% of its sulfur load and 45% of its nitrogen load from foreign emissions. Sulfur emissions from Miyakejima and other volcanoes contribute approximately 50% of the sulfur load in Japan in 2001. Sulfur inflows from regions outside the study domain, which is attributed by using boundary conditions derived from the MOZART global atmospheric chemistry model, are pronounced (10–40%) over most parts of Asia. Compared with previous studies using simple Lagrangian models, our results indicate higher influence from long-range transport. The estimated S/R relationships are believed to be more realistic since they include global influence as well as internal interactions among different parts of China. 相似文献
98.
99.
Zhida Song L. Douglas. James 《Journal of the American Water Resources Association》1992,28(5):833-844
ABSTRACT: Improving the reliability of parametric hydrologic models (sometimes called cenceptual rainfall-runoff models) in the continuous simulation of runoff from ungaged catchments has been frustrated by difficulties in estimating model parameters from catchment characteristics. An underlying problem is that these models use parameters to represent catchments as a whole, whereas data on catchment characteristics are collected at multiple field locations and are difficult to transform into one measure of collective impact. Subdividing the catchment and calibrating a stochastic parametric model to estimate distributions for the parameters that covered the range of observed streamflow values was found to improve the simulations. This paper presents an optimization of the amount of subdivision to use in simulation with a version of the Stanford Watershed Model using available climatological data. The calibration process assumes that catchment heterogeneity introduces errors that can be reduced by calibrating parameters as spatial distributions rather than single values. Calibrations for three diverse small gaged catchments located in California and in Virginia found the optimal number of subdivisions to range from 4 to 25 and the optimal scale to range from 0.3 to 2.1 mi2. 相似文献
100.