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901.
902.
An evaluation of a river health using the index of biological integrity along with relations to chemical and habitat conditions 总被引:13,自引:0,他引:13
We evaluated the health condition of a temperate river during June-November 1999 through applications of the index of biological integrity (IBI) using fish assemblages and qualitative habitat evaluation index (QHEI) as well as chemical analyses. Overall IBI values ranged from 13 to 37 and averaged 23 (n = 25, standard error = 1.16), indicating a "poor" or "very poor" condition according to the criteria of modified Karr [Fisheries 6 (1981) 21]. The values of mean IBI declined at a rate of 0.22 km(-1) (R2 = 0.91, p < 0.05) along the longitudinal distance from the headwaters to the downstream sites. Reduced IBI values at downstream sites reflected low forest cover, high population density and high nutrient enrichments. Ecotoxicity tests using the river water also showed that toxic impacts were evident in the downriver sites. These factors resulted in decreases of riffle benthic species and insectivores and increases of tolerant species, anormalies and exotic species in the river. Spatial pattern in IBI agreed with QHEI values, which showed a linear relation (R2 = 0.998, p < 0.001) with species richness. Field measurements of conductivity and pH, an indicators for variation of conservative ions, showed that the river water was diluted by 40% fold by summer monsoon rain and surface run-off from the watershed, resulting in a physical and chemical instability during the monsoon. For these reasons, average IBI values during the monsoon and postmonsoon decreased >20% compared to the premonsoon, indicating that IBI values were also affected by flow regime. Based on the overall physico-chemical data and IBI values, the river health is rapidly degrading due to the combined effect of chemical contaminations and habitat modifications. 相似文献
903.
A practical application of Driscoll's equation for predicting the acid-neutralizing capacity (ANC) in acidic waters equilibria with the mineral phase gibbsite is reported in this paper. Theoretical predication values of ANC are compared with the experimental data obtained from different literatures. The effect of aluminum (Al) on the value of ANC is investigated. It indicates that Al plays an important role in regulating the buffering effects in acidic natural waters. Failure to consider Al in acidic waters may bias assessment results in certain situations so as to overestimate the ANC values in response to increase in atmospheric deposition. 相似文献
904.
This paper reports an investigation of the dynamics of aluminum (Al) speciation in the forest-well waters from study site 110 of the Rhode River watershed, a representative sub-unit of Chesapeake Bay. Seasonal changes of Al speciation are evaluated by a modified MINEQL computer model using chemical equilibrium calculation. It was found that Al-F and Al-Org complexes were the dominate forms, whereas toxic forms of Al3+ and Al-OH were not significant. This indicates that Al toxicity is not very serious in the Rhode River area due to the high concentrations of fluoride and organic materials, even though sometimes pH is very low (approximately 4). Increased H+ or some other associated factors may be responsible for the decline in fish and amphibian population on the watershed. 相似文献
905.
Xin Jin Wei Wang Shuai Wang Pengkang Jin Xiaochang C. Wang Wushou Zhang Weijun An Yong Wang 《环境科学学报(英文版)》2019,31(7):17-27
This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance(EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process. 相似文献
906.
Xiaopan Li Huizheng Che Hong Wang Xiangao Xi Quanliang Chen Ke Gui Hujia Zhao Linchang An Yu Zheng Tianze Sun Zhizhong Sheng Chao Liu Xiaoye Zhang 《环境科学学报(英文版)》2019,31(6):66-81
The cloud optical depth(COD) is one of the important parameters used to characterize atmospheric clouds. We analyzed the seasonal variations in the COD over East Asia in 2011 using cloud mode data from the AERONET(Aerosol Robotic Network) ground-based observational network. The applicability of the MODIS(Moderate Resolution Imaging Spectroradiometer) COD product was verified and compared with the AERONET cloud mode dataset. There was a good correlation between the AERONET and the MODIS. The spatial and temporal distribution and trends in the COD over China were then analyzed using MODIS satellite data from 2003 to 2016. The seasonal changes in the AERONET data and the time sequence variation of the satellite data suggest that the seasonal variations in the COD are significant. The result shows that the COD first decreases and then increases with the season in northern China, and reaches the maximum in summer and minimum in winter.However, the spatial distribution change is just the opposite in southern China. The spatial variation trend shows the COD in China decreases first with time and gradually increases after 2014. And the trend of COD in the western and central China is consistent with that in China. While the trend of COD shows a continuously increasing over time in northeast China and the Pearl River Delta. 相似文献
907.
An optimized nonlinear grey Bernoulli model was proposed by using a particle swarm optimization algorithm to solve the parameter optimization problem. In addition, each item in the first-order accumulated generating sequence was set in turn as an initial condition to determine which alternative would yield the highest forecasting accuracy. To test the forecasting performance, the optimized models with different initial conditions were then used to simulate dissolved oxygen concentrations in the Guanting reservoir inlet and outlet(China). The empirical results show that the optimized model can remarkably improve forecasting accuracy, and the particle swarm optimization technique is a good tool to solve parameter optimization problems. What's more, the optimized model with an initial condition that performs well in in-sample simulation may not do as well as in out-of-sample forecasting. 相似文献
908.
目前核电站普遍采用的水泥固化处理废液增容大,为了实现废物最小化,开展了微波桶内干燥处理模拟含硼废液可行性研究.采用微波炉对模拟含硼废液干燥特性探索性试验研究,结果表明:桶内干燥产物含水率受模拟含硼废物的厚度影响,桶内干燥工艺需要合理控制模拟含硼废物添加量.12升微波桶内干燥试验预试验结果表明:不锈钢桶壁和桶底干燥产物含水率偏高,建议添加相应的保温或辅助加热措施.综合考虑,合理控制微波干燥条件,模拟含硼废液干燥产物的含水率可降至10wt%(不合游离水)以下,减容系数可达到5.试验表明,微波桶内干燥处理放射性废液是可行的. 相似文献
909.
Xiaoqiang Gong Jinbiao Li Scott X. Chang Qian Wu Zhengfeng An Chengpeng Huang Xiangyang Sun Suyan Li Hui Wang 《Frontiers of Environmental Science & Engineering》2022,16(3):39
910.
分别采用现场铁路路基填料及掺量为0.3%的聚丙烯纤维改良填料构筑室内小型路基,通过对路基顶部施加不同的分级静载,对比研究两种不同填料对路基内应力分布规律和沉降变形特性的影响,进而判断纤维材料作为改良措施运用于路基沉降控制的可行性与有效性。试验结果表明:相对于现场填料路基,纤维改良措施加快了应力在路基中沿深度的扩散速度;应力加载至100 kPa时,两种填料路基的沉降变形规律相似,路基不同深度处的沉降随着基顶作用荷载的增加呈非线性增大;应力达到200 kPa时,纤维改良路基60 cm深度范围内的沉降曲线出现反转点,曲线形状近似拉长的s形;较于现场填料路基,纤维改良措施使基顶沉降分别减少了30.3%及35.4%;在高应力、大变形趋势条件下,纤维材料对路基沉降的控制效果会更好。 相似文献