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环境污染对环境产生的负价值与环境保护对环境产生的正价值相互作用、相互抵消的运动过程,体现了环境整体价值在人类经济社会活动影响下的具体演化模式。文章探讨了环境价值的循环途径、环境资源价值的模型,并对模型进行了具体分析,以期帮助人们提高对环境价值的认识。 相似文献
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Artificial neural network modeling of dissolved oxygen in the Heihe River, Northwestern China 总被引:2,自引:0,他引:2
Xiaohu Wen Jing Fang Meina Diao Chuanqi Zhang 《Environmental monitoring and assessment》2013,185(5):4361-4371
Identification and quantification of dissolved oxygen (DO) profiles of river is one of the primary concerns for water resources managers. In this research, an artificial neural network (ANN) was developed to simulate the DO concentrations in the Heihe River, Northwestern China. A three-layer back-propagation ANN was used with the Bayesian regularization training algorithm. The input variables of the neural network were pH, electrical conductivity, chloride (Cl?), calcium (Ca2+), total alkalinity, total hardness, nitrate nitrogen (NO3-N), and ammonical nitrogen (NH4-N). The ANN structure with 14 hidden neurons obtained the best selection. By making comparison between the results of the ANN model and the measured data on the basis of correlation coefficient (r) and root mean square error (RMSE), a good model-fitting DO values indicated the effectiveness of neural network model. It is found that the coefficient of correlation (r) values for the training, validation, and test sets were 0.9654, 0.9841, and 0.9680, respectively, and the respective values of RMSE for the training, validation, and test sets were 0.4272, 0.3667, and 0.4570, respectively. Sensitivity analysis was used to determine the influence of input variables on the dependent variable. The most effective inputs were determined as pH, NO3-N, NH4-N, and Ca2+. Cl? was found to be least effective variables on the proposed model. The identified ANN model can be used to simulate the water quality parameters. 相似文献
145.
This article establishes a set of indicators and standards for landscape ecological sensitivity analysis of site resources by using the theories and approaches of landscape ecology.It uses landscape diversity index(H),evenness(E),natural degree(N),contrast degree(C) to study spatial structure and landscape heterogeneity of site resources and thus provides a qualitative-quantitative evaluation method for land planning and management of small ,medium scale areas.The analysis of Yantian District,Shenzhen of China showed that Wutong Mountain belonged to high lanscape ecological sensitivity area,Sanzhoutian Reservoir and Shangping Reservoir were medium landscape sensitivity area and high ecological sensitivity area;Dameisha and Xiaomeisha belonged to medium sensitivity area caused by the decline of natural ecological areas.Shatoujiao,Yantian Pier belonged to low sensitivity area but urban landscape ecological development had reshaped and influenced their landscape ecological roles in a great extent.Suggestions on planning,protection goals an development intensity of each site or district were raised. 相似文献
146.
A new approach applying fuzzy mathematic theorems, including the Primary Matrix Element Theorem and the Fisher Classification Method, was established to solve the optimization problem of atmospheric environmental sampling sites. According to its basis, an application in the optimization of sampling sites in the atmospheric environmental monitoring was discussed. The method was proven to be suitable and effective. The results were admitted and applied by the Environmental Protection Bureau (EPB) of many cities of China. A set of computer software of this approach was also comuletelv comniled and used. 相似文献
147.
探讨了连江地热水利用排放对水体、土壤农作物、鱼类的影响,为今后保护环境和合理开发利用地热水提供科学依据。 相似文献
148.
Fang Li Jing Jin Dongqin Tan Longxing Wang Ningbo Geng Rong Cao Yuan Gao Jiping Chen 《环境科学学报(英文版)》2016,28(10):209-217
Hexabromocyclododecane(HBCD) and tetrabromobisphenol A(TBBPA) are two kinds of brominated flame retardants and widely present in the environment and biota. The levels,spatial distributions and mass inventories of HBCD and TBBPA were investigated in sediments and paddy soils from the Liaohe River Basin in northeast China. The concentrations of ΣHBCD and TBBPA were in the range of not detected(nd) to 4.02 ng/g dry weight(dw) and 0.03 to 4.06 ng/g dw, respectively. γ-HBCD was dominated in sediments,while the abundance of α-HBCD was relatively high in paddy soils. The spatial distributions of HBCD and TBBPA in surface sediments and paddy soils indicated that the local point-input was their major source. The significant correlation between total organic carbon(TOC) contents and the HBCD levels suggested that TOC content also exerted an influence on the distribution of HBCD in sediments. Meanwhile, it was found that the irrigation with river water was not the major transportation pathway of HBCD and TBBPA in paddy soils. Based on the study, it was estimated that there were about 1.67 tons HBCD and 2.20 tons TBBPA deposited into sediments of the Liaohe River system every year. The total mass inventories of HBCD and TBBPA in sediments were far higher than that in paddy soils. 相似文献
149.
中国主要河口海湾富营养化特征及差异分析 总被引:6,自引:0,他引:6
针对我国65个沿海河口海湾,基于自然地理数据及2007~2012年水质监测数据,采用箱须图法、聚类分析、相关性分析和主成分分析等方法,探讨河口海湾间富营养化特征、差异性及主要原因.结果表明,大型河口海湾的富营养化状态指标值相对较高,但河口海湾间富营养化响应指标值存在一定差异.DIN、PO43--P和COD是河口海湾富营养化特征的第1主成分,DO和Chl-a是第2主成分,盐度、水深、潮差和面积等是第3主成分,河口海湾水体Chl-a浓度与TN入海量(P<0.01)、DIN(P<0.01)、PO43--P(P<0.05)、流量(P<0.01)、温度(P<0.05)呈显著性正相关,同时与潮差(P<0.05)和盐度(P<0.01)和DO(P<0.01)呈显著性负相关.表明营养盐入海量增多是引起河口海湾一系列富营养化症状的主要因素,但河口海湾自然属性会调节其富营养化状态,造成系统间响应特征的差异.潮差小于2.5m的河口海湾,其营养盐转化效率明显高于潮差大于2.5m的河口海湾.说明河口海湾潮差可通过改变水体滞留时间、垂直混合和光照条件等,调节浮游植物生物量对营养盐的敏感性.此外,与外海的水体交换,海洋生物的捕食,及其他形态营养盐的供给等作用,也会影响河口海湾水体Chl-a的水平.人类活动带来的营养盐输入,以及河口海湾特有的自然属性,共同决定了其富营养化特征的差异和程度. 相似文献
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