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941.
942.
943.
进入生化池的沙粒受粒径影响,或沉积或悬浮在生化池,粒径≤73 μm的细微沙容易悬浮在污泥混合液中,导致活性污泥ρ(MLVSS)/ρ(MLSS)(生物有机质所占的比例)下降. 以粒径≤73 μm的沙粒为对象,研究生化池中不同粒径细微沙对活性污泥ρ(MLVSS)/ρ(MLSS)的影响,探讨细微沙的可悬浮性和悬浮态势,揭示细微沙对污泥活性的影响,以期为污水厂的运行管理提供理论基础. 通过显微观察发现,粒径>33 μm的细微沙不易被活性污泥卷捕,呈自由悬浮态势;粒径≤33 μm的细微沙容易被活性污泥絮体卷捕,呈卷捕附着态势. 细微沙粒径越小,悬浮比(悬浮在污泥混合液中的细微沙占生化池进水中细微沙总量的比例)越大,活性污泥ρ(MLVSS)/ρ(MLSS)越低,悬浮比与细微沙粒径呈显著线性相关(y=0.996-0.010x),活性污泥ρ(MLVSS)/ρ(MLSS)与悬浮比相关性显著〔y=2.84/(12.27x+3.06)〕. 研究显示,细微沙不影响污泥中微生物的活性,污水厂可结合活性污泥ρ(MLVSS)/ρ(MLSS)调控ρ(MLSS),保证ρ(MLVSS)的稳定,有利于实现污水处理系统的稳定运行. 相似文献
944.
以广州市楼顶降尘为研究对象,在分析其粒度分布和重金属总量的基础上,采用单一化学提取法(DWLP、TCLP)和多级化学提取法(SEP)研究了大气颗粒物中4种重金属元素的生物有效性。结果表明:样品中96%以上颗粒小于100μm,其中10μm和2.5μm以下颗粒分别占33%和11%。大气颗粒物中重金属含量很高,Cu、Pb、Zn和Cd的平均含量分别为362.43、1033.81、830.32和5.80mg/kg,是广东省环境土壤背景值的17~64倍。单一提取法中,TCLP的提取效率明显高于DWLP,表明pH值是影响大气颗粒物中重金属释放的主要因素。SEP法结果显示,Zn和Cd的生物可利用态比例远高于Cu和Pb。经DWLP和TCLP法提取后,颗粒物中重金属的总含量有不同程度的降低,生物可利用态所占比例明显增加。通过综合分析,发现SEP此其他两种方法更适用于评价大气颗粒物中重金属的生物有效性。 相似文献
945.
Radioactive particles present a novel exposure pathway for members of the public. For typical assessments of potential doses received by members of the public, habit surveys and environmental monitoring combine to allow the assessment to occur. In these circumstances it is believed that the probability of encounter/consumption is certain. The potential detriment is assessed through sampling the use of environmental monitoring data and dose coefficients such as that in ICRP 60 [ICRP, 1990. 1990 Recommendations of the international commission on radiological protection. Publication 60. Annals of the ICRP 21 (1-3)]. However, radioactive particles often represent a hazard that is difficult to quantify and where the probability of encounter is less than certain as are the potential effects on health. Normal assessment methodologies through sampling and analysis are not appropriate for assessing the impact of radioactive particles either prospectively or retrospectively. This paper details many of the issues that should be considered when undertaking an assessment of the risk to health posed by radioactive particles. 相似文献
946.
为对防砂过程中因地层物性影响而导致冲缝筛管出现结垢问题进行准确的过程分析,基于FLUENT平台利用现场数据建立流道中的化学反应和沉积结垢的数值模型,评估管道缝宽、环境压力、温度、离子浓度与流速对冲缝筛管结垢速率的影响规律。结果表明:筛管结垢速率与管内温度和离子浓度成正相关,与管内流体流速成负相关,但环境压力影响不大,同时结垢主要产生在冲缝台阶以及冲缝套与打孔基管的接触面上,对产液的过流面积存在较大影响;结合正交分析得到4个敏感因素的主次顺序为:管内温度、管内流速、反应物浓度、环境压力,并确定最小结垢的组合方案;通过DPM模型探究CaCO3颗粒的沉积规律,得到管内的沉积情况,并建立多因素垢层厚度的计算模型。在实际生产中为降低筛管结垢对油井产能的影响,可以通过降低管内的温度、离子浓度及适当地增大流速来抑制结垢过程的发生。 相似文献
947.
为科学谋划赣州市“十四五”期间大气污染防治工作,重点对赣州市“十三五”期间整体空气质量变化情况,以及影响赣州市优良天数的两个重要参数——臭氧(O3)和细颗粒物(PM2.5)的污染规律进行了分析。结果表明,赣州市“十三五”期间空气质量改善明显,优良天数整体增加。O3浓度和O3超标天数占总污染天数的比例整体均呈现波动上升趋势,对空气质量综合指数的贡献率逐年增加;高浓度O3污染通常发生在干燥、高温条件下,高发期主要集中在4—5月和7—11月,空间分布呈西高东低的特点,与2018年大气污染源排放清单中挥发性有机物(VOCs)的排放量分布情况较为一致。PM2.5浓度呈逐年下降趋势,在2019年和2020年达到国家空气质量二级标准;PM2.5污染天数在2016年同比增加26 d,而后逐年减少,其中2020年较2015年减少了12 d;PM2.5浓度的季节变化特征整体呈现为冬季高、春秋次之、夏季低,空间分布特征与O3类似。建议赣州市在“十四五”期间以PM2.5和O3协同治理为主要思路,继续深入打好蓝天保卫战。 相似文献
948.
949.
Zhengzheng Zhang Hong Li Hongyan Liu Yingchen Bai Jinjuan Li Guorui Zhi Yanting Yu Wenjun Li Hao Zhang Fan Meng 《环境科学学报(英文版)》2021,33(4):363-372
The pollution characteristics of surfactant substances in fine particles (PM2.5) in spring were studied in the Beibu Gulf Region of China, 68 samples of PM2.5 were collected at Weizhou Island in Beihai City from March 12 to April 17, 2015. The Anionic Surfactant Substances (ASS) and Cationic Surfactant Substances (CSS) in the samples were analyzed using Byethyl Violet Spectrophotometry and Disulfide Blue Spectrophotometry, respectively. Combined with the data from backward trajectory simulation, the effects of air pollutants from remote transport on the pollution characteristics of surfactant substances in PM2.5 in the Beibu Gulf Region were analyzed and discussed. The results showed that the daily mean concentrations of ASS and CSS in spring in the Beibu Gulf Region were 165.20 pmol/m3 and 8.05pmol/m3, and the variation ranges were 23.21–452.55 pmol/m3 and 0.65–31.31 pmol/m3, accounting for 1.82‰ ± 1.65‰ and 0.12‰ ± 0.11‰ of the mass concentration of PM2.5, respectively. These concentrations were lower than those in comparable regions around the world. There was no clear correlation between the concentrations of ASS and CSS in PM2.5 and the mass concentrations of PM2.5. Tourism and air transport had a positive contribution on the concentrations of ASS. The concentration of surfactant substances in PM2.5 was significantly impacted by wind speed and wind direction. Atmospheric temperature, air pressure and precipitation had little effect on the concentrations of surfactant substances. Surfactant substances in PM2.5 significantly impacted visibility. Results also showed that the main sources of surfactant substances were from the southern China and Southeast Asia. 相似文献
950.
Size distribution and anthropogenic sources apportionment of airborne trace metals in Kanazawa, Japan 总被引:1,自引:0,他引:1
Aerosol samples were collected from Kanazawa, Japan to examine the size distribution of 12 elements and to identify the major sources of anthropogenic elements. Key emission sources were identified and, concentrations contributed from individual sources were estimated as well. Concentrations of elements V, Ca, Cd, Fe, Ba, Mg, Mn, Pb, Sr, Zn, Co and Cu in aerosols were determined with ICP-MS. The results showed that Ca, Mg, Sr, Mn, Co and Fe were mainly associated with coarse particles (>2.1 μm), primarily from natural sources. In contrast, the elements Zn, Ba, Cd, V, Pb and Cu dominated in fine aerosol particles (<2.1 μm), implying that the anthropogenic origin is the dominant source. Results of the factor analysis on elements with high EFCrust values (>10) showed that emissions from waste combustion in incinerators, oil combustion (involving waste oil burning and oil combustion in both incinerators and electricity generation plants), as well as coal combustion in electricity generation plants were major contributors of anthropogenic metals in the ambient atmosphere in Kanazawa. Quantitatively estimated sum of mean concentrations of anthropogenic elements from the key sources were in good agreement with the observed values. Results of this study elucidate the need for making pollution control strategy in this area. 相似文献