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排序方式: 共有417条查询结果,搜索用时 15 毫秒
111.
通过气-液两相普通流化床和内循环式生物反应器(DTBR)的对比研究,发现DTBR具有更好的氧传质能力和氧转移效率。本试验条件下,当表面气速为0.29cm/s时,DTBR的(KLα)20和E4值分别为普通流化床反应器的1.2倍和1.3倍。通过研究影响DTBR混合特性的主要因素,发现表面气速的影响最大,表面液速的影响最小。其它条件相同,表面气速分别为0.29和0.074cm/s时,DTBR的循环时间分别为12s和16s,混合时间分别为76.2s和91.8s。 相似文献
112.
Minru Liu Yunkai Tan Kejing Fang Changya Chen Zhihua Tang Xiaoming Liu Zhen Yu 《环境科学学报(英文版)》2021,33(1):80-89
Dissolved organic matter (DOM) derived from various composts can promote significant changes of soil properties. However, little is known about the DOM compositions and their similarities and differences at the molecular level. In this study, the molecular compositions of DOM derived from kitchen waste compost (KWC), green waste compost (GWC), manure waste compost (MWC), and sewage sludge compost (SSC) were characterized by electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The molecular formulas were classified into four subcategories: CHO, CHON, CHOS, and CHONS. The KWC, MWC, and SSC DOM represented the highest fraction (35.8%-47.4%) of CHON subcategory, while the GWC DOM represented the highest fraction (68.4%) of CHO subcategory. The GWC DOM was recognized as the nitrogen- and sulfur-deficient compounds that were less saturated, more aromatic, and more oxidized compared with other samples. Further analysis of the oxygen, nitrogen-containing (N-containing), and sulfur-containing (S-containing) functional groups in the four subcategories revealed higher organic molecular complexity. Comparison of the similarities and differences of the four samples revealed 22.8% ubiquitous formulas and 17.4%, 11.1%, 10.7%, and 6.3% unique formulas of GWC, KWC, SSC, and MWC DOM, respectively, suggesting a large proportion of ubiquitous DOM as well as unique, source-specific molecular signatures. The findings presented herein provide new insight into the molecular characterization of DOM derived from various composts and demonstrated the potential role of these different compounds for agricultural utilization. 相似文献
113.
Remediation of metal polluted mine soil with compost: co-composting versus incorporation 总被引:10,自引:0,他引:10
Tandy S Healey JR Nason MA Williamson JC Jones DL 《Environmental pollution (Barking, Essex : 1987)》2009,157(2):690-697
Trace element contamination of post-industrial sites represents a major environmental problem and sustainable management options for remediating them are required. This study compared two strategies for immobilizing trace elements (Cu, Pb, Zn, and As) in mine spoil: (1) co-composting contaminated soil with organic wastes and (2) conventional incorporation of mature compost into contaminated soil. Sequential chemical extraction of the soil was performed to determine temporal changes in trace element fractionation and bioavailability during composting and plant growth. We show that mine spoil can be co-composted successfully and this action causes significant shifts in metal availability. However, co-composting did not lead to significant differences in metal partitioning in soil or in plant metal uptake compared with simply mixing mine spoil with mature compost. Both treatments promoted plant growth and reduced metal accumulation in plants. We conclude that co-composting provides little additional benefit for remediating trace-element-polluted soil compared with incorporation of compost. 相似文献
114.
This paper presents industrial experience of process identification, monitoring, and control in a full-scale wastewater treatment plant. The objectives of this study were (1) to apply and compare different process-identification methods of proportional-integral-derivative (PID) autotuning for stable dissolved oxygen (DO) control, (2) to implement a process monitoring method that estimates the respiration rate simultaneously during the process-identification step, and (3) to propose a simple set-point decision algorithm for determining the appropriate set point of the DO controller for optimal operation of the aeration basin. The proposed method was evaluated in the industrial wastewater treatment facility of an iron- and steel-making plant. Among the process-identification methods, the control signal of the controller's set-point change was best for identifying low-frequency information and enhancing the robustness to low-frequency disturbances. Combined automatic control and set-point decision method reduced the total electricity consumption by 5% and the electricity cost by 15% compared to the fixed gain PID controller, when considering only the surface aerators. Moreover, as a result of improved control performance, the fluctuation of effluent quality decreased and overall effluent water quality was better. 相似文献
115.
Parashar C Verma N Dixit S Shrivastava R 《Environmental monitoring and assessment》2008,140(1-3):119-122
Pollution of water bodies is one of the areas of major concern to environmentalists. Water quality is an index of health and
well being of a society. Industrialization, urbanization and modern agriculture practices have direct impact on the water
resources. These factors influence the water resources quantitatively and qualitatively. The study area selected were the
Upper lake and Kolar reservoir of Bhopal, the state capital of Madhya Pradesh, India. The Upper lake and Kolar reservoir both
are the important sources of potable water supply for the Bhopal city. The physico–chemical parameters like temperature, pH,
turbidity, total hardness, alkalinity, BOD, COD, Chloride, nitrate and phosphate were studied to ascertain the drinking water
quality. 相似文献
116.
Size and resin fractionations of dissolved organic matter and trihalomethane precursors from four typical source waters in China 总被引:3,自引:0,他引:3
Wei Q Wang D Wei Q Qiao C Shi B Tang H 《Environmental monitoring and assessment》2008,141(1-3):347-357
Dissolved organic matter (DOM) and its potential to form disinfection by-products (DBPs) during drinking water treatment raise
challenges to water quality control. Understanding both chemical and physical characteristics of DOM in source waters is key
to better water treatment. In this study, the DOM from four typical source waters in China was fractionated by XAD resin adsorption
(RA) and ultrafiltration (UF) techniques. The trihalomethane formation potential (THMFP) of all fractions in the DOM were
investigated to reveal the major THM precursors. The fraction distributions of DOM could be related to their geographical
origins in a certain extent. The dominant chemical fraction as THM precursors in the DOM from south waters (East-Lake reservoir
in Shenzhen and Peal rivers in Guangzhou) was hydrophobic acid (HoA). The size fraction with molecular weight (MW) <1 kDa
in both south waters had the highest THMFP. The results of cluster analysis showed that the parameters of fractions including
DOC percentage (DOC%), UV254%, SUVA254 (specific UV254 absorbance) and THMFP were better for representing the differences of DOM from the studied waters than specific THMFP (STHMFP).
The weak correlation between SUVA254 and STHMFP for either size or XAD fractions suggests that whether SUVA254 can be used as an indicator for the reactivity of THM formation is highly dependent on the nature of organic matter. 相似文献
117.
地表水中溶解氧监测及变化规律 总被引:7,自引:0,他引:7
采用碘-淀粉光度法对连云港大浦河水域中溶解氧进行测定,并对其日变化、季节变化和垂直分布及变化规律进行了分析。 相似文献
118.
J. Bai K. R. Li D. Y. Liu J. Zhang H. F. Zhang G. S. Liu J. L. Li Z. Y. Li D. M. Gao 《Water, Air, & Soil Pollution: Focus》2007,7(6):673-681
The distribution patterns and factors affecting uptake rates and turnover times of dissolved inorganic nutrients by heterotrophic
bacterioplankton (HB) in Jiaozhou Bay were studied based on in situ surveys and laboratory culturing. The uptake rates of
dissolved inorganic phosphorus (DIP) and dissolved inorganic nitrogen (DIN) by HB are limited by the temperature of the water
and the concentration of dissolved organic carbon. The turnover times of DIP and DIN by HB are regulated by the concentrations
of the nutrients and the numbers of HB, which show significant spatiotemporal variability in Jiaozhou Bay. HB may aggravate
the P-limitation of phytoplankton by competing for phosphorus in summer in Jiaozhou Bay. HB play an important role in the
biogeochemical cycling of nutrients and may increase the N:P ratio and the accumulation of DIN, thereby accelerating the imbalance
of the N:P ratio in Jiaozhou Bay. 相似文献
119.
Mobilization of heavy metals from contaminated paddy soil by EDDS,EDTA, and elemental sulfur 总被引:1,自引:0,他引:1
Wang G Koopmans GF Song J Temminghoff EJ Luo Y Zhao Q Japenga J 《Environmental geochemistry and health》2007,29(3):221-235
For enhanced phytoextraction, mobilization of heavy metals (HMs) from the soil solid phase to soil pore water is an important
process. A pot incubation experiment mimicking field conditions was conducted to investigate the performance of three soil
additives in mobilizing HMs from contaminated paddy soil (Gleyi-Stagnic Anthrosol): the [S, S]-isomer of ethylenediamine disuccinate
(EDDS) with application rates of 2.3, 4.3, and 11.8 mmol kg−1 of soil, ethylenediamine tetraacetate (EDTA; 1.4, 3.8, and 7.5 mmol kg−1), and elemental sulfur (100, 200, and 400 mmol kg−1). Temporal changes in soil pore water HM and dissolved organic carbon concentrations and pH were monitored for a period of
119 days. EDDS was the most effective additive in mobilizing soil Cu. However, EDDS was only effective during the first 24
to 52 days, and was readily biodegraded with a half-life of 4.1 to 8.7 days. The effectiveness of EDDS decreased at the highest
application rate, most probably as a result of depletion of the readily desorbable Cu pool in soil. EDTA increased the concentrations
of Cu, Pb, Zn, and Cd in the soil pore water, and remained effective during the whole incubation period due to its persistence.
The highest rate of sulfur application led to a decrease in pH to around 4. This increased the pore water HM concentrations,
especially those of Zn and Cd. Concentrations of HMs in the soil pore water can be regulated to a large extent by choosing
the proper application rate of EDDS, EDTA, or sulfur. Hence, a preliminary work such as our pot experiment in combination
with further plant experiments (not included in this study) will provide a good tool to evaluate the applicability of different
soil additives for enhanced phytoextraction of a specific soil. 相似文献
120.
Photochemical reactions can alter the transformation of sedimentary organic matter into dissolved organic matter (DOM) and affect its ultimate fate in water ecosystems. In the present study, the photorelease of DOM and Fe from resuspended lake sediments was investigated under different O2 and NO3? concentration conditions to study the mechanisms of DOM and Fe photorelease. The amount of photoreleased Fe, which ranged from 0.22 to 0.70 μmol/L, was significantly linearly correlated with the amount of photoreleased DOM. O2 and NO3? could promote the photochemical release of DOM and Fe, especially during the initial 4 h irradiation. In general, the order of the photorelease rates of DOM and Fe under different conditions was as follows: NO3?/aerobic > aerobic ≈ NO3?/anaerobic > anaerobic. The photorelease rates of DOM and Fe were higher for the initial 4 hr irradiation than these for the subsequent 8 hr irradiation. The photorelease of DOM and Fe is thought to proceed via direct photodissolution and indirect processes. The relative contributions of indirect processes (>60%) was much greater than that of direct photodissolution (<40%). The photoproduced H2O2 under aerobic and anaerobic conditions indicated that hydroxyl radicals (?OH) are involved in the photorelease of DOM. Using ?OH scavengers, it was found that 38.7%, 53.7%, and 77.6% of photoreleased DOM was attributed to ?OH under anaerobic, aerobic, and NO3?/aerobic conditions, respectively. Our findings provide insights for understanding the mechanisms and the important role of ?OH in the DOM and Fe photorelease from resuspended sediments. 相似文献