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51.
52.
本研究选取化学消毒的常用6种中和剂组氨酸、甘氨酸、抗坏血酸、吐温80、亚硫酸钠和硫代硫酸钠,采用动态浊度鲎试验定量检测样品中内毒素活性,研究中和剂在不同浓度范围内单独使用对内毒素活性检测的影响,旨在优选出适于鲎法检测细菌内毒素的中和剂种类,确定合适的浓度范围.结果表明在0~1.0%浓度范围内,除了甘氨酸和硫代硫酸钠之外,组氨酸、抗坏血酸、吐温80、亚硫酸钠(碱性和中性)均对鲎试验结果有不同程度的干扰,都不能在鲎试验之前作为化学消毒的中和剂.虽然0~1.0%浓度的甘氨酸对鲎试验结果基本无明显影响,但是甘氨酸和戊二醛的中和产物显黄色,所以不适于在光度法鲎试验中用作戊二醛的中和剂.0~1.0%浓度的硫代硫酸钠对鲎试验结果基本无明显干扰,但是当浓度升高至1.0%~5.0%时会对鲎试验结果有一定的抑制作用.与组氨酸、甘氨酸、抗坏血酸、吐温80和亚硫酸钠相比,硫代硫酸钠更适于在内毒素活性检测之前用作消毒剂的中和剂,但是浓度应控制在0.5%范围以内. 相似文献
53.
为探究饮用水厂滤池反冲洗水和排泥水的直接回用和处理后回用对水厂的影响及两类水处理过程中的差异,采用了污染负荷计算、实验室混凝小试和现场混凝-超滤中试装置对两类生产废水分别进行了研究。溶解性有机碳(dissolved organic carbon,DOC)、氨氮(NH4+-N)、Al3+和全氟类化合物(perfluorinated compounds,PFASs)的污染负荷计算结果表明生产废水直接回用会为水厂带来一定的额外负荷,其中排泥水和反冲洗水分别对PFASs和Al3+负荷贡献较大;通过对小试中浊度,UV254以及5种荧光组分去除效果的对比,反冲洗水的混凝效果稍好于排泥水,同时10 mg·L-1的聚合氯化铝为最佳混凝剂方案;在中试过程中,两类水中的浊度、有机物、Al3+和PFASs均可被有效去除,出水差异较小,但反冲洗水中的亲水性和小分子有机物使得其去除效果低于排泥水。总体来说,经过处理之后,两类生产废水均可回用,回用可有效减少废水排放量,提高水厂水资源... 相似文献
54.
McClenny WA Jacumin HH Oliver KD Daughtrey EH Whitaker DA 《Journal of environmental monitoring : JEM》2006,8(2):263-269
Analytical results obtained by thermal desorption GC/MS for 24 h diffusive sampling of 11 volatile organic compounds (VOCs) are compared with results of time-averaged active sampling at a known constant flow rate. Air samples were collected with co-located duplicate diffusive sampling tubes and one passivated canister. A total of eight multiple-component sampling events took place at fixed positions inside and outside three private homes. Subsequently, a known amount of sample air was transferred from the canister to an adsorbent tube for analysis by thermal desorption GC/MS. Results for the 11 most prevalent compounds--Freon 11, 1,3-butadiene, benzene, toluene, tetrachloroethene, ethylbenzene, m,p-xylene, o-xylene, 4-ethyltoluene, 1,3,5-trimethylbenzene, and p-dichlorobenzene--show that the ratio of average study values (diffusive sampling to active sampling) is 0.92 with 0.70 and 1.14 extreme ratios. Absolute percent difference for duplicate samples using diffusive sampling was <10% for the four most prevalent compounds. Agreement between the two sampling approaches indicates that the prediction of approximately constant diffusive sampling rates based on previous laboratory studies is valid under the field conditions. 相似文献
55.
以某化肥企业退役场地为例,基于GIS和EVS方法,开展场地的氨氮和挥发性有机污染物污染状况调查与特征分析。结果显示,场地主要超标特征污染物是氨氮和1,2-二氯乙烷;土壤中氨氮超标点位浓度最大值为2808 mg·kg-1,包气带最下段土层中基本已无氨氮污染,而潜水含水层土层中氨氮污染却又加重,说明地下水中氨氮污染可能存在污染物传输的优先通道;土壤中1,2-二氯乙烷未超标,地下水中1,2-二氯乙烷超标点位浓度最大值为1188.52μg·L-1,说明土壤中污染物未超出筛选值无法作为地下水中污染物未超标准限值的表征条件,土壤和地下水样品的采集检测均有必要;PID快速检测结果与厂区的污染源分布情况相符,对于初步筛选采集具有代表性的土壤样品具有较强的辅助作用。 相似文献
56.
57.
River channel migration and cutoff events within large river riparian corridors create heterogeneous and biologically diverse
landscapes. However, channel stabilization (riprap and levees) impede the formation and maintenance of riparian areas. These
impacts can be mitigated by setting channel constraints away from the channel. Using a meander migration model to measure
land affected, we examined the relationship between setback distance and riparian and off-channel aquatic habitat formation
on a 28-km reach of the Sacramento River, California, USA. We simulated 100 years of channel migration and cutoff events
using 11 setback scenarios: 1 with existing riprap and 10 assuming setback constraints from about 0.5 to 4 bankfull channel
widths (bankfull width: 235 m) from the channel. The percentage of land reworked by the river in 100 years relative to current
(riprap) conditions ranged from 172% for the 100-m constraint setback scenario to 790% for the 800-m scenario. Three basic
patterns occur as the setback distance increases due to different migration and cutoff dynamics: complete restriction of cutoffs,
partial restriction of cutoffs, and no restriction of cutoffs. Complete cutoff restriction occurred at distances less than
about one bankfull channel width (235 m), and no cutoff restriction occurred at distances greater than about three bankfull
widths (∼700 m). Managing for point bars alone allows the setbacks to be narrower than managing for cutoffs and aquatic habitat.
Results suggest that site-specific “restriction of cutoff” thresholds can be identified to optimize habitat benefits versus
cost of acquired land along rivers affected by migration processes. 相似文献
58.
A selective separation and quantitative determination procedure for 210Pb and 210Po in various environmental matrices from different sources such as IAEA-326 soil, phosphate rocks (PR), and phosphogypsum (PG) was developed. The tested samples were digested sequentially using concentrated mineral acids (HF, HNO3) by a programmable high-pressure microwave digestion system. The sample solution was loaded onto a preconditioned ion exchange column (Sr-resin) for chromatographic separation. Polonium-210 was eluted by 6 M HNO3 then spontaneously deposited onto polished silver discs to be measured using low-background alpha spectrometry. Lead-210 was sequentially eluted using 6 M HCl solution, precipitated as lead oxalate, dissolved in HNO3 solution, and mixed with scintillation cocktail to be measured by liquid scintillation counting (LSC). Performance of the developed procedure was tested using a reference soil (IAEA-326), with recommended isotope values, that was used as a quality control to assess separation and quantification efficiency (recovery %). The minimum detectable activities of 210Pb and 210Po were found to be 24 and 0.28 Bq kg(-1) for the measurements using LSC and alpha spectrometry, respectively. The recoveries (%) of 210Pb and 210Po were found to be 80 and 60%, respectively. To test the validity of the proposed LSC method, a comparative study was performed by measuring 210Pb activity concentration in test samples by nondestructive gamma-ray spectrometry. 相似文献
59.
人类历史的进化规律表明,生产力的发展是社会进步的最终决定力量.只有坚持以经济建设为中心,不断解放和革新生产力,才能为人的全面发展提供坚实的物质基础.在特定的物质基础上,必然紧密地联系着政治文明和精神文明的形态和内容. 相似文献
60.