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411.
膜污染是限制膜生物反应器(MBR)广泛应用的主要因素之一。针对MBR处理生活污水过程中存在的硝化效果不稳定与膜污染问题,提出了一种新型的MBR系统:通过吸附-预沉淀实现进水中碳氮的分离和单独处理,不仅提高了污染物去除效果,且能够有效控制膜污染。研究结果表明,吸附-预沉淀可以去除进水中约89.7%的有机物,系统出水COD、NH4+-N平均浓度为24 mg/L、0.78 mg/L,去除率分别为95.9%和98.1%。MBR中碳氮比的降低和硝化细菌比例的增加大大降低了MBR内MLSS、EPS和SMP含量,平均浓度分别为5 185 mg/L、41 mg/g MLSS和2.62 mg/g MLSS。在膜通量为4 L/(m2·h)条件下,TMP可稳定保持在20 kPa左右。通过吸附-预沉淀过程可有效控制MBR中的膜污染。  相似文献   
412.
Nitrogen fertilization (N) is commonly known as a main source of direct nitrous oxide (N2O) emission from agricultural soils. An area of 38 % of the total land surface of Poland was covered by agricultural soils in 2009. In this paper, we aimed at analyzing data regarding the land exploitation for 13 selected subareas of Poland between 1960 and 2009. Seven out of the 13 subareas studied are located in the West (area A), and six subareas are located in southeast of Poland (area B). The total area covered by large farms (>20 ha) differed largely, between area A (10.6 %) and area B (0.9 %) in 2009. Both areas varied in terms of the amount of fertilizers used annually, average crop yield and crop structure. Average direct emissions of N2O from agricultural soils were 1.66 ± 0.09 kg N2O–N ha?1 a?1 for area A, 1.39 ± 0.07 kg N2O–N ha?1 a?1 for area B and 1.46 ± 0.07 kg N2O–N ha?1 a?1 for the whole country between 1960 and 2009.  相似文献   
413.
Rice seeds (Tianyou, 3618) were used to examine the physiological and biochemical responses to phosphine exposure during germination. A control (0 mg m−3) and four concentrations of phosphine (1.4 mg m−3, 4.2 mg m−3, 7.0 mg m−3 and 13.9 mg m−3) were used to treat the rice seeds. Each treatment was applied for 90 min once per day for five days. The germination rate (GR); germination potential (GP); germination index (GI); antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and lipid peroxidation measured through via malondialdehyde (MDA) were determined as indicators of the physiological and biochemical responses of the rice seeds to phosphine exposure. These indicators were determined once per day for five days. The results indicated that the GR, GP and GI of the rice seeds markedly decreased after phosphine exposure. The changes in the activities of the antioxidant enzymes due to the phosphine exposure were also significant. The exposure lowered the CAT and SOD activities and increased POD activity in the treated rice seeds compared with controls. The MDA content exhibited a slow increase trend with the increase of phosphine concentration. These results suggest that phosphine has inhibitory effects on seed germination. In addition, phosphine exposure caused oxidative stress in the seeds. The antioxidant enzymes could play a pivotal role against oxidative injury. Overall, the effect of phosphine on rice seeds is different from what has been reported previously for insects and mammals.  相似文献   
414.
Textile dye effluents are typically characterized by strong color and recalcitrance, even at very low concentration. The process of enrichment of anionic azo dye on the surface of TiO2 fibers followed by photosensitization degradation under ambient air conditions was extensively investigated. Adsorption isotherms and zeta potentials were used to describe the “dye/TiO2 surface” interface, taking into account the effects of pH on the nature and population of the surface groups on the TiO2 fibers. The extent of the photocatalytic degradation of dye on TiO2 surface was determined by FTIR. N2 adsorption isotherms and optical spectra were employed to investigate the effect of photosensitization. The adsorption of dyes on the TiO2 surface occurs via electrostatic attraction through the formation of single- or multidentate-coordinated surface complexes. Almost complete photobleaching of the absorption band at 534 nm is achieved in ~4 h. Dye-sensitized TiO2 fiber could absorb part of the visible light spectrum (λ?<?600 nm). Interfacial electron transfer can potentially alter the degradation efficiency. The regenerated TiO2 fiber could be reused for subsequent decolorization without a decline in adsorption efficiency compared with freshly prepared TiO2 samples, which may be attributed to preservation of the hierarchical pore structure and restoration of the original surface properties. In summary, we propose an efficient “adsorption–photoregeneration–reuse” process applying TiO2 fibers for the degradation of dyes in water.  相似文献   
415.
One question in the use of plants as biomonitors for atmospheric mercury (Hg) is to confirm the linear relationships of Hg concentrations between air and leaves. To explore the origin of Hg in the vegetable and grass leaves, open top chambers (OTCs) experiment was conducted to study the relationships of Hg concentrations between air and leaves of lettuce (Lactuca sativa L.), radish (Raphanus sativus L.), alfalfa (Medicago sativa L.) and ryegrass (Lolium perenne L.). The influence of Hg in soil on Hg accumulation in leaves was studied simultaneously by soil Hg-enriched experiment. Hg concentrations in grass and vegetable leaves and roots were measured in both experiments. Results from OTCs experiment showed that Hg concentrations in leaves of the four species were significantly positively correlated with those in air during the growth time (p?<?0.05), while results from soil Hg-enriched experiment indicated that soil-borne Hg had significant influence on Hg accumulation in the roots of each plant (p?<?0.05), and some influence on vegetable leaves (p?<?0.05), but no significant influence on Hg accumulation in grass leaves (p?>?0.05). Thus, Hg in grass leaves is mainly originated from the atmosphere, and grass leaves are more suitable as potential biomonitors for atmospheric Hg pollution. The effect detection limits (EDLs) for the leaves of alfalfa and ryegrass were 15.1 and 22.2 ng g–1, respectively, and the biological detection limit (BDL) for alfalfa and ryegrass was 3.4 ng m–3.  相似文献   
416.
● BACs were used in electrode material for both fixed and flowing electrodes. ● ASAR of FCDI and MCDI was improved by 134% and 17%, respectively. ● ENRS of FCDI and MCDI was improved by 21% and 53%. ● The mechanism of improving desalination performance was analyzed in detail. Capacitive deionization (CDI) is a novel electrochemical water-treatment technology. The electrode material is an important factor in determining the ion separation efficiency. Activated carbon (AC) is extensively used as an electrode material; however, there are still many deficiencies in commercial AC. We adopted a simple processing method, ball milling, to produce ball milled AC (BAC) to improve the physical and electrochemical properties of the original AC and desalination efficiency. The BAC was characterized in detail and used for membrane capacitive deionization (MCDI) and flow-electrode capacitive deionization (FCDI) electrode materials. After ball milling, the BAC obtained excellent pore structures and favorable surfaces for ion adsorption, which reduced electron transfer resistance and ion migration resistance in the electrodes. The optimal ball-milling time was 10 h. However, the improved effects of BAC as fixed electrodes and flow electrodes are different and the related mechanisms are discussed in detail. The average salt adsorption rates (ASAR) of FCDI and MCDI were improved by 134% and 17%, respectively, and the energy-normalized removal salt (ENRS) were enhanced by 21% and 53%, respectively. We believe that simple, low-cost, and environmentally friendly BAC has great potential for practical engineering applications of FCDI and MCDI.  相似文献   
417.
Gu  Zhaolin  Han  Jie  Zhang  Liyuan  Wang  Hongliang  Luo  Xilian  Meng  Xiangzhao  Zhang  Yue  Niu  Xinyi  Lan  Yang  Wu  Shaowei  Cao  Junji  Lichtfouse  Eric 《Environmental Chemistry Letters》2023,21(2):725-739
Environmental Chemistry Letters - Policies and measures to control pandemics are often failing. While biological factors controlling transmission are usually well explored, little is known about...  相似文献   
418.
再生气氛对CuO/AC脱硫活性的影响   总被引:10,自引:0,他引:10  
本文考察了不同气氛再生后CuO/AC脱硫剂的二次脱硫活性,并藉借助XRD和XPS表征技术以及对再生后脱硫剂残硫的分析,探讨了脱硫剂以不同还原剂在不同温度下再生后二次脱硫活性差异的内在原因,结果表明:脱硫剂经H2再生后二次脱硫活性与初活性相比出现大幅度下降,H2气氛中添加H2O可提高其二次脱硫活性;经NH3在300℃再生后二次脱硫活性与初活性相当,两次再生后仍未观察到活性的明显下降,NH3再生时脱硫  相似文献   
419.
The purpose of this study was to determine and evaluate the spatial changes in soil salinity by using geostatistical methods. The study focused on the suburb area of Beijing, where urban development led to water shortage and accelerated wastewater reuse to farm irrigation for more than 30 years. The data were then processed by GIS using three different interpolation techniques of ordinary kriging (OK), disjunctive kriging (DK), and universal kriging (UK). The normality test and overall trend analysis were applied for each interpolation technique to select the best fitted model for soil parameters. Results showed that OK was suitable for soil sodium adsorption ratio (SAR) and Na+ interpolation; UK was suitable for soil Cl? and pH; DK was suitable for soil Ca2+. The nugget-to-sill ratio was applied to evaluate the effects of structural and stochastic factors. The maps showed that the areas of non-saline soil and slight salinity soil accounted for 6.39 and 93.61 %, respectively. The spatial distribution and accumulation of soil salt were significantly affected by the irrigation probabilities and drainage situation under long-term wastewater irrigation.  相似文献   
420.
牛军 《环境与发展》2020,(2):115-116
本文主要针对雾霾天气背景下大气环境监测质量的提升路径展开深入研究,先阐述了大气环境监测质量的提升重要性,比如有利于提高环境污染的防治水平、有利于不断提高城市环境规划水平等,然后重点提出了几点可行的提升路径,主要包括制定大气环境监测质量保障体系、加强环境质量监测网络建设、加强大气环境监测采样管理、加强3S技术的应用、加强监测监察联动协调机制、扩大大气环境质量评价范围等,确保监测数据与完整性和准确性相符,确保大气环境监测质量的稳步提升,以创建节能减排、生态环保的节约型社会。  相似文献   
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