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621.
Viney P. Aneja Candis S. Claiborn Zheng Li Anuradha Murthy 《Journal of the Air & Waste Management Association (1995)》2013,63(2):217-220
Abstract This paper presents a comparative study of the biodegradation of three aromatic volatile compounds in a compost-based biofilter: toluene, xylene, and 1,2,4-trimethyl-benzene, used in the course of this work for the first time in the field of biofiltration. Hence, three identical biofiltration units have been operated at the laboratory scale. During the experiments, nitrogen (as urea) was supplied at various concentrations to each reactor, via irrigated nutrient solutions. A comparative analysis of the results showed that the biodegradability scale followed the degree of substitution around the aromatic ring: toluene > xylene > trimethylbenzene, with 95, 80, and 70% maximum conversions, respectively. In addition, and despite the different removal levels achieved in the three biore-actors, it was established that from a reaction viewpoint, the degradation of the three compounds seemed to follow similar metabolic pathways involving methylcatechol isomers. Finally, by varying the nitrogen input concentrations in the three reactors, three degradation regimes have been highlighted: an N-limitation regime and an N-optimum regime, common to the three solvents, and an N-excess regime, favorable to the colonization of the filter beds by nitrifying species, which particularly affected the xylene and trimethylbenzene biodegradation. 相似文献
622.
Bin Xu Tingyao Gao Chenyan Hu Jiekuan Shi 《Journal of the Air & Waste Management Association (1995)》2013,63(6):714-718
Abstract This paper introduces a new allocation method on discharge loading of each function zone in a total emission control region. The wind frequency, the position of each district, and the pollutant’s influence area were taken into account in this new method. The concept of “average downwind distance” was brought forward in this paper. The method here is more reasonable than the original method of area distribution, which was proposed by the “A-value” method in regulation of total emissions in China, by means of the simulation of annual average concentration in the total emission control region. 相似文献
623.
This study projected responses of forest net primary productivity (NPP) to three climate change scenarios at a resolution
of 5 km × 5 km across the state of Louisiana, USA. In addition, we assessed uncertainties associated with the NPP projection
at the grid and state levels. Climate data of the scenarios were derived from Community Climate System Model outputs. Changes
in annual NPP between 2000 and 2050 were projected with the forest ecosystem model PnET-II. Results showed that forest productivity
would increase under climate change scenarios A1B and A2, but with scenario B1, it would peak during 2011–2020 and then decline.
The projected average NPP under B1 over the years from 2000 to 2050 was significantly different from those under A1B and A2.
Forest NPP appeared to be primarily a function of temperature, not precipitation. Uncertainties of the NPP projection were
due to large spatial resolution of the climate variables. Overall, this study suggested that in order to project effects of
climate change on forest ecosystem at regional level, modeling uncertainties could be reduced by increasing the spatial resolution
of the climate projections. 相似文献
624.
Based on the Environmental Kuznets Curve theory,the authors choose provincial panel data of China in 1990 2007 and adopt panel unit root and co-integration testing method to study whether there is Environmental Kuznets Curve for China’s carbon emissions.The research results show that:carbon emissions per capita of the eastern region and the central region of China fit into Environmental Kuznets Curve,but that of the western region does not.On this basis,the authors carry out scenario analysis on the occurrence time of the inflection point of carbon emissions per capita of different regions,and describe a specific time path. 相似文献
625.
Xu H Jiang Y Al-Rasheid KA Al-Farraj SA Song W 《Environmental science and pollution research international》2011,18(7):1213-1221
Introduction
Ciliated protozoa play important roles in aquatic ecosystems especially regarding their functions in micro-food web and have many advantages in environmental assessment compared with most other eukaryotic organisms. The aims of this study were focused on analyzing the application of an indicator based on taxonomic relatedness of ciliated protozoan assemblages for marine environmental assessment. 相似文献626.
Zhou ZF Zheng YM Shen JP Zhang LM He JZ 《Environmental science and pollution research international》2011,18(9):1644-1652
Purpose
Denitrification is an important biochemical process in global nitrogen cycle, with a potent greenhouse gas product N2O. Wastewater irrigation can result in the changes of soil properties and microbial communities of agricultural soils. The purpose of this study was to examine how the soil denitrification genes responded to different irrigation regimes. 相似文献627.
Introduction
The goal of the present study was to investigate the effects of Cu contamination on the above-mentioned biochemical and physiological parameters in order to explore possible prevention strategies against heavy metal stress.Materials and methods
Effects of copper (Cu) on the roots of Sagittaria sagittifolia L. were studied after 10 days of treatment at five concentration levels. The accumulation of Cu, the generation rate of O2 ·?C, the contents of thiobarbituric acid reactive substances (TBARS) and polyamines, as well as the activities of arginine decarboxylase (ADC) and polyamine oxidase (PAO) in the roots were measured and analyzed.Results and discussion
It was observed that endogenous Cu content increased in roots of S. sagittifolia L. in a concentration-dependent manner, along with an increased production of O2 ·?C. TBARS content increased progressively up to 5 ??mol l?1 Cu. A constant increase in ADC activity was also observed. The results indicated that lower Cu concentrations (2.5 and 5 ??mol l?1, respectively) had greater enhancing effect on the contents of free Put and perchloric acid-soluble conjugated (PS-conjugated) putrescine (Put), while Cu treatments at different concentration levels had similar enhancing effect on the content of perchloric acid-insoluble bound Put. In total, Put content in each Cu-treated group was higher than that in the control group. PAO activity was inhibited up to 10 ??mol l?1 Cu but enhanced at higher Cu concentrations (20 and 40 ??mol l?1). This explained the initial rise and subsequent decline of the contents of all forms of spermine (Spm), free and PS-conjugated spermidine (Spd). However, with the increase of Cu concentration, total Spm content increased gradually while total Spd content decreased. Our results suggest that Cu is phytotoxic to the roots of S. sagittifolia L. at high concentrations, and that the increased Spm level is not sufficient to resist Cu-induced oxidative damages. 相似文献628.
XM Zheng HL Liu W Shi S Wei JP Giesy HX Yu 《Environmental science and pollution research international》2011,19(7):2498-2505
Perfluorinated compounds (PFCs) have been widely used in industrial and consumer products and frequently detected in many environmental media. Potential reproductive effects of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) have been reported in mice, rats and water birds. PFOS and PFOA were also confirmed developing toxicants towards zebrafish embryos; however, the reported effect concentrations were contradictory. Polyfluorinated alkylated phosphate ester surfactants (including FC807) are precursor of PFOS and PFOA; however, there is no published information about the effects of FC807 and PFNA on zebrafish embryos. Therefore, this study was conducted to determine the effects of these four PFCs on zebrafish embryos. Normal fertilized zebrafish embryos were selected to be exposed to several concentrations of PFOA, PFNA, PFOS or FC807 in 24-well cell culture plates. A digital camera was used to image morphological anomalies of embryos with a stereomicroscope. Embryos were observed through matching up to 96-h post-fertilization (hpf) and rates of survival and abnormalities recorded. PFCs caused lethality in a concentration-dependent manner with potential toxicity in the order of PFOS > FC807 > PFNA > PFOA based on 72-h LC(50). Forty-eight-hour post-fertilization pericardial edema and 72- or 96-hpf spine crooked malformation were all observed. PFOA, PFNA, PFOS and FC807 all caused structural abnormalities using early stages of development of zebrafish. The PFCs all retarded the development of zebrafish embryos. The toxicity of the PFCs was related to the length of the PFC chain and functional groups. 相似文献
629.
630.
Ferric and manganese binary oxide (FMBO) has been successfully used to remediate arsenic-polluted river, but there still lacks sufficient data to evaluate its effects on environments. The release behaviors of iron (Fe), manganese (Mn), and arsenic (As) in different Eh ranges were investigated for As-bearing FMBO sediment after remediating As-polluted DaSha River by FMBO. Under high Eh range (+550 to +400 mV), slight dissolution of Fe and Mn, which corresponded to 12.2% and 25.6%, and less than 5% of As release were observed in 336 h. Under lower Eh range (+50 to −100 mV), elevated extent of the dissolution of Mn and Fe were observed, which corresponded to as high as 61.3% and 70.1%. Under such conditions, the dissolution rate of Mn was higher than that of Fe. Furthermore, from the established relationship of As release and the dissolution of Fe and Mn, the release of As seemed dominated by the dissolution of Fe. X-ray photoelectron spectroscopy (XPS) analysis demonstrated the release of Fe, Mn, As(III), and As(V) after sodium ascorbate-treatment, and the re-adsorption of As(V), as indicated from the increased binding energy of As 3d from 44.78 to 45.83 eV. Surface element composition analysis indicated significant decrease of Mn from 3.22% to 0.54%, slight increase of Fe from 12.45% to 13.67%, and elevated ratio of As from 0.11% to 0.32% accordingly. The main reactions of Fe and Mn dissolution and the pathways of As release under different Eh ranges were also proposed. 相似文献