Surface water quality and its control in a river with intensive human impacts–a case study of the Xiangjiang River,China

Surface water quality and its natural and anthropogenic controls in the Xiangjiang River were investigated using multivariate statistical approaches and a comprehensive observation dataset collected from 2004 to 2008. Cluster analysis (CA) grouped the 15 different sampling stations into five clusters with similar hydrochemistry characteristics and pollution levels. Four principal components (PCs), nutrients, heavy metals, natural components, and organic components, were extracted from the entire dataset. Comparison of the different regional characteristics of these four PCs revealed a decreasing trend for heavy metals and an increasing trend for organic factor on an annual scale, and the seasonal trend was only observed for natural factor. We also conducted analysis of variance (ANOVA) in combination with principal component analysis (PCA) to quantify the relative contribution of spatial and temporal variations to each of the four PCs. The results revealed that 62% of the contributions from the spatial sites were responsible for variations in heavy metals, while 83% of the contributions from the sampling time were responsible for natural variations observed. However, no significant spatial or temporal contributions were found to be responsible for the nutrient and organic variations. Finally, some suggestions regarding water management were put forward based on the current status and future trends of surface water quality in the Xiangjiang River.     

Kinetic study and modeling on photocatalytic degradation of para-chlorobenzoate at different light intensities

In order to clarify the dependence of apparent adsorption constant Ks in the Langmuir-Hinshelwood (L-H) model on the incident light intensity, photocatalytic degradation kinetic characteristics were experimentally investigated at different light intensities using para-chlorobenzoate (4-CBA) as a model compound. In all cases 4-CBA initial degradation rates showed dependence on 4-CBA initial concentration, which can be described by the L-H model. However, the adsorption constant Ks and rate constant kr obviously varied with light intensity. To account for the experimental finding, slight modification of the classic kinetic model developed by Turchi and Ollis was tentatively proposed by assuming insufficiency of H2O/OH- available for photo-activated holes' scavenging. Such a kinetic model predicts that both k(r) and Ks(-1) are linearly proportional to the square root of the intensity in a rather large intensity range. The validity of the modified model was proved by fitting it to the experimental data.     

从一个污染海湾的海藻植物看其十年的变化:巴西桑托斯湾

巴西某地区的第一部综合性的海藻植物志于1957年由Joly出版,该植物志描述并解释了105个分类单位.20年后,liveira和Berchez重新调查了该地区,只发现了69个分类单位,褐藻数量显著减少.1991年在三个物种丰度最大的研究站进行的另一次调查中,发现有同样的减少趋势,而且没有发现褐藻的存在.生物多样性的这种减少归因于污染的增加.这里我们列举了1998～1999年进行的一次新的调查结果.这次调查显示20世纪50年代记录的某些物种得到了恢复,其中包括7种褐藻.物种数的这一增长被认为是当地政府作出的减少污染的努力以及一个海底污水终端建成的结果.     

静态混凝破乳吸附法处理乳化废液

乳化废液在静态混凝破乳分离装置中，加入混凝破乳剂ＰＡＣ２ｇ／Ｌ、助凝剂ＰＡＭ（８％）２ｍｌ／Ｌ、混凝６ｍｉｎ，静态分离１ｈ，出水清沏透明，油含量小于１０ｍｇ／Ｌ。再经煤渣灰吸附处理，出水油含量小于３ｍｇ／Ｌ，ＣＯＤｃｒ＜３００ｍｇ／Ｌ，ｐＨ：７～８。混凝絮渣经酸溶后，可回收９５％以上的油品，此方法已在实际中应用。     

Contribution of black carbon to nonlinearity of sorption and desorption of acetochlor on sediment

In order to investigate the contribution of various black carbon (BC) contents to nonlinearity of sorption and desorption isotherms for acetochlor on sediment, equilibrium sorption and desorption isotherms were determined to measure sorption and desorption of acetochlor in sediment amended with various amounts of BC. In this paper, two types of BC referred to as BC400 and BC500 were prepared at 400°C and 500°C, respectively. Higher preparation temperature facilitated the formation of micropores on BC to enhance its sorption capacity. Increase of the BC content obviously increased the sorption amount and reduced the desorption amount for acetochlor. When the BC500 contents in total organic carbon (TOC) increased from 0 to 60%, Freundlich sorption coefficient (K _f) increased from 4.07 to 35.74, and desorption hysteresis became gradually obvious.When the content of BC in TOC was lower than 23%, the sorption isotherm had a significant linear correlation (p = 50.05). In case of desorption, a significant nonlinear change could be observed when the content of BC was up to 13%. Increase of BC content in the sediment would result in shifting the sorption-desorption isotherms from linearity to nonlinearity, which indicated that contribution of BC to nonlinear adsorption fraction became gradually remarkable.     

Enhanced nitrification in integrated floating fixed-film activated sludge (IFFAS) system using novel clinoptilolite composite carrier

Novel carriers with favorable electrophilicity and hydrophilicity were prepared. Novel carriers had the capability of nitrification-enhancing. NH₄⁺-N removal efficiency of IFFAS process rose up to 20% with novel carriers. Nitrosomonadales and Nitrospirales were identified as the functional nitrifiers. The population of Nitrospirales increased by 4.51%. The integrated floating fixed-film activated sludge (IFFAS) process is an ideal preference for nitrification attributing to the longer sludge age for nitrifiers. However, as the core of this process, conventional carriers made of polymer materials usually exhibit negative charge and hydrophobicity on the surface, which is unbeneficial to nitrifying biofilm formation. In this study, novel clinoptilolite composite carriers with favorable hydrophilicity, positive charge and nitrification-enhancing capability were made and implemented in IFFAS system. In comparison with conventional carriers, the novel clinoptilolite composite carriers displayed positive charges on the surface (11.7±1.1 mV, pH 7.0) with increased hydrophilicity (surface contact angle dropped to 76.7°). The novel-carriers-based reactors achieved significantly better NH₄⁺-N removal efficiency at different influent concentrations, dissolved oxygen (DO) levels and shock loads (NH₄⁺-N removal efficiency rose up to 20% comparing with the control reactors filled with polyethylene (PE) carriers or activated sludge). High-throughput sequencing (HTS) results indicated the novel clinoptilolite composite carriers provided favorable niche for more types of bacteria, especially for Nitrosomonadales and Nitrospirales (the functional nitrifiers in the system). The population of Nitrospirales increased by 4.51% by using novel clinoptilolite composite carriers comparing with using PE carriers, which ensured enhanced nitrification process. This study was expected to provide a practical option for enhancing wastewater nitrification performance with the novel clinoptilolite composite carrier.     

Contribution of black carbon to nonlinearity of sorption and desorption of acetochlor on sediment

In order to investigate the contribution of various black carbon (BC) contents to nonlinearity of sorption and desorption isotherms for acetochlor on sediment, equilibrium sorption and desorption isotherms were determined to measure sorption and desorption of acetochlor in sediment amended with various amounts of BC. In this paper, two types of BC referred to as BC400 and BC500 were prepared at 400°C and 500°C, respectively. Higher preparation temperature facilitated the formation of micropores on BC to enhance its sorption capacity. Increase of the BC content obviously increased the sorption amount and reduced the desorption amount for acetochlor. When the BC500 contents in total organic carbon (TOC) increased from 0 to 60%, Freundlich sorption coefficient (K _f) increased from 4.07 to 35.74, and desorption hysteresis became gradually obvious.When the content of BC in TOC was lower than 23%, the sorption isotherm had a significant linear correlation (p = 50.05). In case of desorption, a significant nonlinear change could be observed when the content of BC was up to 13%. Increase of BC content in the sediment would result in shifting the sorption-desorption isotherms from linearity to nonlinearity, which indicated that contribution of BC to nonlinear adsorption fraction became gradually remarkable.     

膜生物反应器处理丙烯腈废水试验

采用平板式聚乙烯中空纤维膜生物反应器处理丙烯腈废水,进水ＣＯＤ值４００～７５０ｍ ｇ·Ｌ^1-,反应器的有效体积３０Ｌ,停留时间５０ｈ,经过膜生物反应器处理后ＣＯＤ的出水平均值为１８９ｍ ｇ·Ｌ^1-． 同时对膜生物反应器进、出水进行ＧＣ／ＭＳ分析,试验结果表明：２,６ 双（二甲基,乙基）－４－酚、十五醇、十六烯、苯二甲酸、硝基苯二甲酸为生物难降解的有机物．     

不同光强下光催化降解对氯苯甲酸钠动力学

以对氯苯甲酸钠为模型污染物,研究了不同光强条件下的光催化降解动力学.结果表明对氯苯甲酸钠的光催化降解动力学可以用Langmuir-Hinshelwood模式来描述,但其中的动力学参数与光强有关.速率常数k_r随入射光强的升高而增加,而表观吸附常数K_s却随入射光强的升高而降低.k_r和K_s^-1近似与光强呈幂函数的关系.说明提高光强虽然可以增加光催化降解速率但会降低其能量利用效率,如何使用低光强照射可能是提高光催化氧化反应器能量利用效率的重要因素之一.     

Does technology advancement reduce aggregate carbon dioxide emissions? Evidence from 66 countries with panel threshold regression model

Environmental Science and Pollution Research - The influence of technology advancement on carbon dioxide (CO2) emissions is complex and controversial, yet existing literature ignores the level of...