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491.
珠江口和邻近海域沉积有机质的来源及其沉积通量的时空变化 总被引:4,自引:2,他引:2
分析了珠江口和邻近海域沉积有机质(OM)的总有机碳(TOC)、总氮(TN)及稳定碳同位素组成〔δ(13C)〕等地球化学参数,并对有机质的来源和沉积通量进行了研究. 结果表明,珠江口沉积有机质来自大陆(52%)和水生(48%)混合来源;而邻近海域沉积有机质主要为水生来源(93%). 珠江口陆源有机质含量〔w(T-OC)为5.4 mg/g〕远远高于邻近海域(0.49 mg/g),近年来珠江口TOC和陆源有机质(T-OC)的平均沉积通量分别为5.57和2.2~3.6 mg/(cm2·a),说明珠江河口接受了大量的陆源有机物的输入,这是由于自20世纪后期的几十年以来,华南地区经济快速增长造成大量土地开垦,以及工农业生产和生活污水的排放所致. 珠江口和邻近海域的水生有机质沉积通量在近年均呈增加趋势,在珠江口达到最大值3.6 mg/(cm2·a),说明大量的营养物质导致水体的富营养化,从而促使水域初级生产力的增长. 相似文献
492.
Adsorption of microcystins by carbon nanotubes 总被引:4,自引:0,他引:4
The production of cyanobacterial toxins microcystins (MCs) by cyanobacterial bloom which may promote the growth of tumor in human liver is a growing environmental problem worldwide. In this paper, the adsorption of MC-RR and LR, which were extracted from cyanobacterial cells in Dianchi Lake in China, by carbon nanotubes (CNTs), wood-based activated carbon (ACs) and clays were investigated. Compared with ACs and clay materials of sepiolite, kaolinite and talc tested, CNTs were found to have a strong ability in the adsorption of MCs. At the concentrations of 21.5 mg l(-1) MC-RR and 9.6 mg l(-1) MC-LR in 50 mmol phosphate buffer solution (pH 7.0), the adsorption amounts of MCs by CNTs with the range of outside diameter from 2 to 10nm were 14.8 and 5.9 mg g(-1), which were about four times higher than those by other adsorbents tested. It was shown that with the decrease of CNTs outside diameters from 60 to 2 nm, the adsorption amount of MCs was apparently increased, however the size of CNTs particles formed in solution declined. This result implies that the size of CNTs tube pore that is fit for the molecular dimension of MCs plays a dominant role. Furthermore the specific surface area of CNTs was also found to be a factor in the adsorption of MCs. The results suggested that the selection of suitable size of CNTs as a kind of adsorbent is very important in the efficient eliminating MCs from drinking water in future. 相似文献
493.
Fang Liu Chunyang Liao Jianjie Fu Jungang Lv Qinzhao Xue Guibin Jiang 《Environmental geochemistry and health》2014,36(1):65-77
The residue levels of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) and 16 selected organochlorine pesticides (OCPs) in rice and rice hull collected from a typical e-waste recycling area in southeast China were investigated from 2005 to 2007. PAHs and OCPs also were measured in ten mollusk species (soft tissues) collected in an adjacent bay in 2007. Individual PAHs were frequently found in the entire sample set (including the rice, hull, and mollusk samples) with a detection rate of 73 %. The total concentrations of 16 PAHs (ΣPAHs) and 16 OCPs (ΣOCPs) were in the range of 40.8–432 ng/g dry weight (mean: 171 ng/g) and 2.35–925 ng/g (122 ng/g), respectively, which were comparable or higher than those reported in some polluted areas. Statistical comparisons suggested that the concentrations of contaminants in hull gradually decreased from 2005 to 2007 and the residue levels were generally in the order of mollusk, hull, and rice, on a dry weight basis. Principal component analysis in combination with diagnostic ratios implied that combustion of coal, wood, and plastic wastes that are closely associated with crude e-waste recycling activities is the main source of PAHs. The finding of decreasing trend of concentrations of PAHs in this area is consistent with the efforts of local authorities to strengthen regulations on illegal e-waste recycling activities. Composition analysis suggested that there is a recent usage or discharge of hexachlorocyclohexane and dichlorodiphenyltrichloroethane into the tested area. The estimated daily intake (EDI) of ΣPAHs and ΣOCPs (calculated from mean concentrations) through rice and mollusk consumption was 0.411 and 0.921 μg/kg body weight (bw)/day, respectively. 相似文献
494.
Zhendong Yang Aihua Lv Yulun Nie Chun Hu 《Frontiers of Environmental Science & Engineering》2013,7(3):451-456
Fe3O4 was supported on mesoporous Al2O3 or SiO2 (50 wt.%) using an incipient wetness impregnation method, and Fe3O4/Al2O3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyacetic acid and para-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe3O4 on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO2, more Lewis acid sites existed on the surface of Al2O3, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe3O4/Al2O3 exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment. 相似文献
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497.
Gaozhong Pu Jingjing Tong Aimeng Su Xu M Jingjing Du Yanna Lv Xingjun Tian 《环境科学学报(英文版)》2014,26(5):1001-1013
To understand the further impacts of multiple stressors in freshwater, we investigated the effects of heavy metal(HM, Cu and Zn) and nutrient enrichments(nitrogen and phosphorus, NP) on microbial decomposition of Pterocarya stenoptera litter and the associated extracellular enzyme activities and microbial biomass with microcosms. Results showed that the decomposition rates were slower in the polluted stream waters than those in the unpolluted ones, which corresponded to lower microbial biomass and integrated enzyme activities of cellulose and β-glucosidase. The decomposition rates were accelerated at low HM level, which was associated with the stimulated enzyme activities of hydrolytic enzymes or was stimulated by both NP levels in polluted stream waters. In particular, the hydrolase enzyme activities of microbial communities in polluted stream waters were stimulated by low HM level, suggesting that low HM level-stimulated litter decomposition may be due to the increased enzymatic activities. When microbial communities were exposed to HM and NP simultaneously, the inhibitory effect(in unpolluted stream waters) or the stimulated effect(in polluted stream waters) of low HM concentration was enhanced and attenuated, respectively, which suggests that the NP antagonistic effect against HM toxicity on litter decomposition may contribute to the litterassociated extracellular enzyme activities. These results suggest that the co-occurrence of HM and NP may have antagonistic effects on stream ecosystem functioning. 相似文献
498.
The present study investigated the relationship between N-acyl-homoserine lactone(AHL)-based quorum sensing(QS) and the physico-chemical properties of aerobic granules.Stable mature granules were observed in SBR2 and SBR3 with average diameters of 0.96,and1.49 mm,respectively. The sludge densities of aerobic granules in SBR2 and SBR3 were1.0246,and 1.0201 g/mL,respectively,which were higher than that of flocculent sludge in SBR1(1.0065 g/mL). The results showed that the activity of AHL-based QS in SBR2 and SBR3 amounted to 2.4- and 2.1-fold induction,however,that in SBR1 with flocculent sludge was1.6-fold induction. In addition,the results also showed that the activity of AHL-based QS in the three reactors rose in the feast condition,and then dropped with the consumption of substrate. However,the activity of AHL-based QS in these three reactors recovered again in prolonged starvation. Furthermore,the results showed that the enhancement of AHL-based QS favored the extracellular polymeric substance production of microorganisms in activated sludge. Thus,it could be concluded that aerobic granules showed higher AHL-based QS than flocculent sludge,which resulted from the higher sludge density of aerobic granules than flocculent sludge. AHL-based QS was related to the metabolism energy in the feast condition; however,in prolonged starvation,microorganisms would emit more AHL-like molecules to protect themselves to resist starvation. Moreover,the enhancement of AHL-based QS favored the EPS component productivity of the microorganisms in activated sludge,which contributed to maintain the aerobic granular structure. 相似文献
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