水质中砷测定的影响因素探析

目前常采用二乙氨基二硫代甲酸银光度法测定水中砷。在实际操作中由于诸多因素的影响常会出现空白值高、精密度和准确度差等问题。今将积累的一些经验和处理方法,小结成文以供参考。（１）试制的质量是影响空白值的主要因素。二乙氨基二硫代甲酸银对潮湿和光敏感。试剂变...     

氢化物发生——原子荧光法测定水样中的砷

利用氢化物原子荧光光度法测定水样中的砷与传统的二乙氨基二硫代甲酸银光度法进行了比较，分析结果表明，2种方法测得的结果无明显差异。用氢化物原子荧光法测定砷的精密度和准确度可以满足地表水、地下水监测的要求。     

硫酸对测定水中砷的影响

硫酸与金属锌作用产生新生态氢 ,新生态氢将砷还原成气态砷化氢 ,砷化氢被二乙氨基二硫代甲酸银 -三乙醇氨的氯仿溶液吸收生成红色胶体银进行比色。可见 ,硫酸在整个过程中起着重要的作用 ,经过不断摸索和反复实验 ,发现控制硫酸的浓度能够有效控制氧化还原反应的速度和吸收的     

硫酸用量对测定砷的影响

二乙氨基二硫代甲酸银光度法是测砷的经典方法，该法是加入浓硫酸4mL。通过试验发现，将加入浓硫酸量减少一半，可提高测定的灵敏度。     

不同粒径锌粒对AgDDC光度法测砷的影响

不同粒径锌粒对ＡｇＤＤＣ光度法测砷的影响马瑛（石河子市环境监测站）二乙氨基二硫代甲酸银（简称ＡｇＤＤＣ）光度法是测砷的常用方法。普遍认为此法除了与溶液酸度、环境温度、吸收液往高低等因素有关外。锌粒规格的影响也同样不可忽视。因此在各种环境监测分析中，严...     

流动注射二乙氨基二硫代甲酸钠光度法测定废水中铜

采用流动注射二乙氨基二硫代甲酸钠分光光度法测定废水中的铜，优化了试验条件，讨论了干扰离子的影响。方法在0mg／L-10.0mg／L范围内线性良好，检出限为0.07mg／L，水样测定的RSD≤0.8％，加标回收率为98.5％-101％，标准样品的测定结果符合要求。     

连续分光光度法测定环境样品中砷（Ⅲ）、砷（Ⅴ）

使用硼氢化钾做还原剂、砷（Ⅲ）在ＰＨ６时还原为砷化氢，维续酸化样品至ＰＨ≤１时，砷（Ⅴ）再被还原为砷化氢。两种砷经与二乙氨基二硫代甲酸银反应生成带色络合物，实现了连续分光光度测定。两种形态砷的检测限为０．０１μｇＡｓ，对砷标准参考物质的测定合格，回收率为９７．０—１０１．６％。     

二乙氨基二硫化甲酸钠萃取光度法测铜时缓冲溶液pH值的探讨

二乙氨基二硫代甲酸钠萃取光度法测铜，所用氯化铵－氢氧化铵缓冲溶液ＰＨ在８．０－９．０之间，测定结果较好。     

二乙氨基二硫代甲酸钠萃取光度法测铜时缓冲溶液pH值的探讨

二乙氨基二硫代甲酸钠萃取光度法测铜，所用氯化铵－氢氧化铵缓冲溶液ｐＨ在８０～９０之间，测定结果较好。     

应用5B-3型COD测定仪测定水中砷

测砷的经典方法一般是二乙氨基二硫代甲酸银分光光度法,检测限为０００７ｍｇ／Ｌ。今可用５Ｂ－３型ＣＯＤ测定仪来进行测定,检测限为０００１ｍｇ／Ｌ,仪器本身还自带曲线,直接打印测量结果。现用本仪器法和ＤＤＣ－Ａｇ校准曲线法对总站砷标样和水样进行分析比...     

Hydride generation coupled to microfunnel-assisted headspace liquid-phase microextraction for the determination of arsenic with UV–Vis spectrophotometry

In this research, a microfunnel-assisted headspace liquid-phase microextraction technique has been used in combination with hydride generation to determine arsenic (As) by UV–Vis spectrophotometry. The method is based on the reduction of As to arsine (AsH₃) in acidic media by sodium tetrahydroborate (NaBH₄) followed by its subsequent reaction with silver diethyldithiocarbamate (AgDDC) to give an absorbing complex at 510 nm. The complexing reagent (AgDDC) has been dissolved in a 1:1 (by the volume ratio) mixture of chloroform/chlorobenzene microdroplet and exposed to the generated gaseous arsine via a reversed microfunnel in the headspace of the sample solution. Several operating parameters affecting the performance of the method have been examined and optimized. Acetonitrile solvent has been added to the working samples as a sensitivity enhancement agent. Under the optimized operating conditions, the detection limit has been measured to be 0.2 ng mL^?1 (based on 3s_b/m criterion, n _b?=?8), and the calibration curve was linear in the range of 0.5–12 ng mL^?1. The relative standard deviation for eight replicate measurements was 1.9 %. Also, the effects of several potential interferences have been studied. The accuracy of the method was validated through the analysis of JR-1 geological standard reference material. The method has been successfully applied for the determination of arsenic in raw and spiked soft drink and water samples with the recoveries that ranged from 91 to 106 %.     

冶炼烟气中砷的监测方法改进

金属冶炼烟气中的砷大都以颗粒物的形式存在,对环境造成污染.2010年,国家颁布了《铜、镍、钴工业污染物排放标准》( GB 25467-2010),对于废气中砷的监测,该标准中规定使用《空气和废气砷的测定 二乙基二硫代氨基甲酸银分光光度法(暂行)》( HJ 540-2009).然而该方法中对于烟气中砷的监测方法存在一定问题,高氯酸在高温消解过程中易爆炸,比较危险,另外采用在锥形瓶内加热至产生白烟的排酸方式不能有效地排净硝酸,会导致反应无法进行.为此,就该方法中有组织排放废气中砷的前处理部分提出了改进意见.     

Consumption of heavy metal contaminated foods and associated risks in Bangladesh

This study investigated the magnitude of heavy metal contamination and determined the carcinogenic as well as non-carcinogenic risks associated with selected food consumption in Bangladesh. Commonly consumed varieties of rice, vegetables, and fish samples were analyzed to measure the concentrations of heavy metals such as cadmium, chromium, lead, arsenic, manganese, nickel, and zinc. These staple food items showed the greatest probabilities of heavy metal contamination in different phases of their production and marketing. Wide variations of metal concentrations were observed. Specifically, estimated daily intakes of arsenic and cadmium exceeded allowable daily intakes in all three food items. Toxicity scores of the metals were evaluated, and a comprehensive risk assessment was conducted to quantify the risks associated with the daily food consumption. Except for cadmium and lead in vegetables, all the contaminants present in each food item posed significant levels of carcinogenic risks up to 2.99?×?10^?3 compared to the EPA recommended carcinogenic risk level of 1.0?×?10^?6. Cadmium and arsenic intake due to rice consumption also posed unsafe levels of non-carcinogenic risks of 4.587 and 6.648, respectively, compared to the EPA recommended non-carcinogenic risk level of 1.0. Finally, a revised set of permissible limits was proposed for the heavy metals detected in the food items. Those permissible limits would ensure the risks associated with food consumption below the allowable carcinogenic and non-carcinogenic risk levels. Thus, this comprehensive approach would provide guidelines to formulate adequate control measures and regulatory limits of toxic metals in foods produced and marketed in Bangladesh.     

原子荧光法测定废水中砷的不确定度评定

以原子荧光法测定油田废水中砷含量为实例,建立数学模型,分析和识别在分析过程中的不确定度来源,对测量中不确定度的各个分量进行了分步计算及合成,计算出测定结果的扩展不确定度0.74μg/L。通过计算和分析,结果表明,标准工作曲线拟合和方法回收率是原子荧光法测定油田废水中砷含量的不确定度的主要因素。     

Phosphine sampling and analysis using silver nitrate impregnated filters

In the field of industrial hygiene, besides the necessity of monitoring phosphine with direct reading apparatus to prevent accidents, there is a need for a method of sampling and analysing phosphine to control workers' exposure. The use of filters impregnated with silver nitrate to collect arsine, phosphine and stibine in workplace air has been described in the literature. Having previously chosen this type of filter to collect arsine, we studied its characteristics for phosphine capture. A filter impregnated with sodium carbonate was used both as a prefilter to collect the particles and to trap arsenic trioxide. After dissolving the silver compounds in nitric acid, ICP emission spectrometry was used to carry out the analysis. This article describes the comparative sampling we performed in a microelectronic laboratory and in a fumigation chamber (130 samples) to determine the concentration of AgNO3 impregnation solution to be used, the detection limit of the method and the retention capacity of the impregnated filters. Interference with other gases reacting with silver nitrate was studied and the storage time for sampled filters and analysis solutions was checked. The detection limit of the adopted method is better than 1 microg per filter, and the retention capacity exceeds 300 microg per filter. The problem of how to sample phosphine when H2S, NH3, or HCl is present has been solved, but the problem of sampling phosphine in atmospheres where acetylene evolves remains. Sampled filters and filter solutions are stable for more than three months at ambient temperature.     

Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California

As a result of extensive gold and silver mining in the Mojave Desert, southern California, mine wastes and tailings containing highly elevated arsenic (As) concentrations remain exposed at a number of former mining sites. Decades of weathering and erosion have contributed to the mobilization of As-enriched tailings, which now contaminate surrounding communities. Fluvial transport plays an intermittent yet important and relatively undocumented role in the migration and dispersal of As-contaminated mine wastes in semi-arid climates. Assessing the contribution of fluvial systems to tailings mobilization is critical in order to assess the distribution and long-term exposure potential of tailings in a mining-impacted environment. Extensive sampling, chemical analysis, and geospatial mapping of dry streambed (wash) sediments, tailings piles, alluvial fans, and rainwater runoff at multiple mine sites have aided the development of a conceptual model to explain the fluvial migration of mine wastes in semi-arid climates. Intense and episodic precipitation events mobilize mine wastes downstream and downslope as a series of discrete pulses, causing dispersion both down and lateral to washes with exponential decay behavior as distance from the source increases. Accordingly a quantitative model of arsenic concentrations in wash sediments, represented as a series of overlapping exponential power-law decay curves, results in the acceptable reproducibility of observed arsenic concentration patterns. Such a model can be transferable to other abandoned mine lands as a predictive tool for monitoring the fate and transport of arsenic and related contaminants in similar settings. Effective remediation of contaminated mine wastes in a semi-arid environment requires addressing concurrent changes in the amounts of potential tailings released through fluvial processes and the transport capacity of a wash.     

城市交通干道绿地砷污染评价

为了研究城市砷污染的现状及不同区域砷污染的空间差异性,以吉林市表层土壤为研究对象,在交通干道的绿化带和磨盘山保护区采集35个土壤样本,进行pH、有机质及砷含量的测定。采用单项污染指数、污染累计指数法等对土壤砷污染进行评价,并运用方差分析的方法对不同区域的砷污染进行了差异比较。研究表明:吉林市街道砷含量为26.43 mg/kg,为磨盘山自然土壤砷含量的4.08倍,为吉林市砷土壤背景值7.26倍;吉林市砷总体超标率12.9%。江北工业区、吉林大街和解放大路的单项污染指数分别为1.34、0.95、0.87,整体达到轻微污染水平。江北工业区和吉林大街、解放大路的变异系数相差不大,依次为0.13、0.11、0.17。土壤砷的污染累积指数为3.21,且由北向南递减,因此,砷污染主要来自于江北工业区的工业"三废"污染。     

Turbidimetric determination of chloride in different types of water using a single sequential injection analysis system

A sequential injection analysis system for the turbidimetric determination of chloride in different types of water is proposed. The determination is based on the reaction of chloride with silver ions and the subsequent measurement of the turbidity caused by silver chloride precipitation. In this method, the use of toxic reagents, such as mercury thiocyanate, commonly employed in most spectrophotometric techniques for chloride determination, is avoided. The main feature of the developed system is the use of a single configuration to carry out the determination over a wide concentration range (2-400 mg L(-1)) by changing only the aspirated sample volume. This characteristic allows the determination of chloride in ground, surface and wastewaters using the same manifold. In addition, a considerable saving of precipitating reagent is achieved due to non-continuous consumption. The results obtained with the developed system were statistically indistinguishable from those of the potentiometric titration reference method. Relative standard deviations for ten consecutive injections were lower than 3.7%, with a sampling frequency of between 55 and 57 determinations per hour.     

Desorption of arsenic from drinking water distribution system solids

Previous work has shown that arsenic can accumulate in drinking water distribution system (DWDS) solids (Lytle et~al., 2004) when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary objective of this work was to examine the impact of pH and orthophosphate on the chemical release (i.e. desorption) of arsenic from nine DWDS solids collected from utilities located in the Midwest. Arsenic release comparisons were based on the examination of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168~hours. Results showed that arsenic was released from solids and suggested that arsenic release was a result of desorption rather than dissolution. Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in the test range of 7 to 9). Finally, orthophosphate (3 and 5 mg PO₄/L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting in elevated levels at the consumer's tap.     

Uptake of arsenic by alkaline soils near alkaline coal fly ash disposal facilities

The attenuation of arsenic in groundwater near alkaline coal fly ash disposal facilities was evaluated by determining the uptake of arsenic from ash leachates by surrounding alkaline soils. Ten different alkaline soils near a retired coal fly ash impoundment were used in this study with pH ranging from 7.6 to 9.0, while representative coal fly ash samples from two different locations in the coal fly ash impoundment were used to produce two alkaline ash leachates with pH 7.4 and 8.2. The arsenic found in the ash leachates was present as arsenate [As(V)]. Adsorption isotherm experiments were carried out to determine the adsorption parameters required for predicting the uptake of arsenic from the ash leachates. For all soils and leachates, the adsorption of arsenic followed the Langmuir and Freundlich equations, indicative of the favorable adsorption of arsenic from leachates onto all soils. The uptake of arsenic was evaluated as a function of ash leachate characteristics and the soil components. The uptake of arsenic from alkaline ash leachates, which occurred mainly as calcium hydrogen arsenate, increased with increasing clay fraction of soil and with increasing soil organic matter of the alkaline soils. Appreciable uptake of arsenic from alkaline ash leachates with different pH and arsenic concentration was observed for the alkaline soils, thus attenuating the contamination of groundwater downstream of the retired coal fly ash impoundment.