To evaluate the effect of abiotic factors on larval and juvenile fish assemblage in shallow waters of middle reaches of Li River, Guilin, China. Samplings were taken monthly at 7 stations in the mainstream and 2 stations in 3 tributaries from May 2014 to April 2015. Synchronously, temperature, pH, turbidity, conductivity, dissolved oxygen rainfall and discharge were obtained. In all, 11.886 larval and juvenile fish from 18 species belonging to 8 families, 16 genera was captured. Principal Component Analysis (PCA) showed obvious significant difference between the environmental variables across sampling areas and months. The results of Canonical Correspondence Analysis (CCA) indicated that water temperature, turbidity, discharge and rainfall were dominant factors on larval and juvenile fish assemblage. 相似文献
A simulation-based interval quadratic waste load allocation (IQWLA) model was developed for supporting river water quality
management. A multi-segment simulation model was developed to generate water-quality transformation matrices and vectors under
steady-state river flow conditions. The established matrices and vectors were then used to establish the water-quality constraints
that were included in a water quality management model. Uncertainties associated with water quality parameters, cost functions,
and environmental guidelines were described as intervals. The cost functions of wastewater treatment units were expressed
in quadratic forms. A water-quality planning problem in the Changsha section of Xiangjiang River in China was used as a study
case to demonstrate applicability of the proposed method. The study results demonstrated that IQWLA model could effectively
communicate the interval-format uncertainties into optimization process, and generate inexact solutions that contain a spectrum
of potential wastewater treatment options. Decision alternatives can be generated by adjusting different combinations of the
decision variables within their solution intervals. The results are valuable for supporting local decision makers in generating
cost-effective water quality management strategies. 相似文献
This study evaluated the individual and interactive effect of phenol and thiocyanate (SCN−) on partial nitritation (PN) activity using batch test and response surface methodology. The IC50 of phenol and SCN− on PN sludge were 5.6 and 351 mg L−1, respectively. The PN sludge was insensitive to phenol and SCN− at levels lower than 1.77 and 43.3 mg L−1, respectively. A regression model equation was developed and validated to predict the relative specific respiration rate (RSRR) of PN sludge exposed to different phenol and SCN− concentrations. In the range of independent variables, the most severe inhibition was observed with a valley value (17%) for RSRR, when the phenol and SCN− concentrations were 4.08 and 198 mg L−1, respectively. An isobole plot was used to judge the combined toxicity of phenol and SCN−, and the joint inhibitory effect was variable depending on the composition and concentration of the toxic components. Furthermore, the toxic compounds showed independent effects, which is the most common type of combined toxicity.
Heavy metals and surfactants have a significant effect on the sorption of organic contaminants. In this study, batch equilibrium experiments were carried out to investigate the influence of Pb(NO(3))(2) on the sorption of p-nitrophenol (PNP) onto sediments in the presence of cationic surfactant cetylpyridinium chloride (CPC). Results indicated that in the complex system containing PNP, Pb(NO(3))(2) and CPC, the sorption of PNP decreased with increasing concentration of Pb(NO(3))(2) due primarily to competing for adsorption sites. Likewise, partitioning of PNP in adsorbed surfactant layers and micelles decreased with increasing level of Pb(NO(3))(2). Moreover, the influence of different metal ions (Pb(2+), Cd(2+), Zn(2+)) was examined and results indicated that the presence of heavy metals inhibited the sorption of PNP in the order: Pb(2+)>Cd(2+)>Zn(2+). The competitive effect of the heavy metals was in agreement with the hydration energy and hydrated radius. The results are believed to provide a useful insight into describing the transport and fate of PNP in natural environments. 相似文献
A study was conducted to determine the annual average radon concentrations in California residences, to determine the approximate fraction of the California population regularly exposed to radon concentrations of 4 pCi/l or greater, and to the extent possible, to identify regions of differing risk for high radon concentrations within the state. Annual average indoor radon concentrations were measured with passive (alpha track) samplers sent by mail and deployed by home occupants, who also completed questionnaires on building and occupant characteristics. For the 310 residences surveyed, concentrations ranged from 0.10 to 16 pCi/l, with a geometric mean of whole-house (bedroom and living room) average concentrations of 0.85 pCi/l and a geometric standard deviation of 1.91. A total of 88,000 California residences (0.8 percent) were estimated to have radon concentrations exceeding 4 pCi/l. When the state was divided into six zones based on geology, significant differences in geometric mean radon concentrations were found between several of the zones. Zones with high geometric means were the Sierra Nevada mountains, the valleys east of the Sierra Nevada, the central valley (especially the southern portion), and Ventura and Santa Barbara Counties. Zones with low geometric means included most coastal counties and the portion of the state from Los Angeles and San Bernardino Counties south. 相似文献