6项环境监测分析方法标准中钴、铬、钼、钛的不确定度分析及其在达标判定中的应用

研究依据测定不确定度的基本理论和ISO 21748：2017《采用重复性、再现性和正确度评估测量不确定度的导则》，提出了基于中国环境监测分析方法标准多家实验室验证中已获得的数据计算合成标准不确定度的方法，将方法标准中规定的重复性、再现性等指标与合成标准不确定度进行了衔接。分析了近年发布的6项水质监测分析方法标准中钴、铬、钼、钛等4种金属元素的相对合成标准不确定度，结果表明：被测量的浓度是影响方法标准测量不确定度的重要因素。对于火焰原子吸收分光光度法（FAAS）和石墨炉原子吸收分光光度法（GAAS），样品浓度为方法标准测定下限3倍左右时，测定结果的相对标准不确定度可保持在15%以下；对于电感耦合等离子体发射光谱法（ICP-AES），样品浓度为方法标准测定下限3~5倍时，测定结果的相对标准不确定度为12%~17%；对于电感耦合等离子体质谱法（ICP-MS），钛元素浓度为测定下限3倍左右时，相对标准不确定度在15%以下，而钴、铬、钼的浓度在测定下限40~100倍以上时，相对标准不确定度在15%以下。6项方法标准可分别用于《地表水环境质量标准》（GB 3838—2002）以及22项水污染物排放标准钴、铬、钼、钛的达标监测。     

氢化物发生原子荧光光度法测定水中锑的不确定度评定

介绍了原子荧光光度法测定水中锑的不确定度评定方法,分析和识别在测定过程中的不确定度来源,较为全面地评定了测量不确定度,最后计算出测定结果的合成标准不确定度和扩展不确定度.结果表明,标准溶液配制过程和标准曲线拟合引起的不确定度是原子荧光光度法测定水中锑含量不确定度的主要来源.     

固体吸附/热脱附-气相色谱法测定环境空气中苯系物的不确定度评定

建立固体吸附/热脱附-气相色谱法测定环境空气中苯系物的不确定度评定方法,分析测定过程中不确定度的来源,进行各不确定度分量的评估,并给出合成相对标准不确定度和扩展不确定度。     

火焰原子吸收法测定水样铅含量的不确定度评定

实验室认可和资质认定都要求检测实验室具备评定测量不确定度的能力,现依据JJF1059-1999《测量不确定度评定与表示》,对火焰原子吸收法测定水样中铅含量进行不确定度评估,分析测定过程中不确定度来源,量化不确定度分量,求出合成不确定度和扩展不确定度,给出测定结果的表示式。     

离子色谱法测定PM_(2.5)中硫酸根离子含量不确定度评议

准确测定大气颗粒物中水溶性组份对分析污染物来源及身体健康具有重要意义。本文采用离子色谱法测定PM2.5中硫酸根离子含量,并对测定的不确定度进行分析。分析过程不确定度来源是样品重复性测量引入不确定度,样品测量准确性引入不确定度和标准曲线的不确定度。应用不确定度评定理论,计算硫酸根离子的合成不确定度。结果表明,滤膜中硫酸根离子本底浓度高低与剪裁滤膜环节是不确定度的主要来源。为了提高分析的准确性,建议使用本底低的滤膜,并取整张滤膜进行分析。     

热分解法测定水质中总氮的不确定度分析

采用实验测定和误差分析的方法,对TOC分析仪测定水质中总氮含量的不确定度进行了分析,测量过程中不确定度的来源有样品重复性测量、标准曲线拟合、标准溶液配制、测量仪器本身等,量化估算了不确定度的各分量。结果表明,标准曲线拟合是影响水质中总氮测定不确定度的主要因素,其次为标准溶液配制所产生的不确定度,样品重复性测量和测量仪器本身所产生的不确定度也不容忽视。同时提出了在测定过程中减小不确定度的有效途径。     

离子色谱法测定水中氟离子含量的不确定度评定

文章对离子色谱法测定水中氟离子(F-)可能产生的不确定度来源进行全面分析,通过对氟离子测定结果的不确定度的量化评定,得出由线性最小二乘法拟合曲线所产生的不确定度对总不确定度贡献最大,占总不确定度的33.3%。     

石墨炉原子吸收光谱法测定全血中铅的不确定度评定

根据《测量不确定度评定与评定表示指南》(JJF 1059-1999)建立了石墨炉原子吸收光谱法测定全血中铅不确定度的数学模型,分析了测试过程中不确定度的来源,并对各不确定度分量进行量化。本次测量的合成相对不确定度值为0.047 3,其中最大的分量是样品消化前处理重复测定引入的,其不确定度分量值为0.04。本次全血中铅测定结果为(130.7±12.4)μg/L,k=2,即测定结果置信水平为95%。     

原子荧光光度法测定水中汞的不确定度分析

用原子荧光光度法对测定水中汞的不确定度进行分析,找出影响不确定的因素,对测量不确定度进行计算和评定,结果表明影响其测量不确定度主要因素是原子荧光光强度值带来的不确定度,其它因素是次要的.     

用ICS-90型离子色谱仪测定水中钙离子的不确定度分析

对离子色谱法测定水中钙离子的不确定度进行评定,并分析了其影响因素主要有来自重复测量引入的A类不确定度和来自工作曲线的不确定度以及来自标准溶液的不确定度。     

Iron-rich Oklahoma clays as a natural source of chromium in monitoring wells

Water samples, drawn from groundwater monitoring wells located southeast of Oklahoma City, OK, were found to contain elevated concentrations of total chromium with an apparent source localized to the area surrounding each well. Since these monitoring wells are located in areas with no historic chromium usage, industrial sources of chromium were ruled out. Water testing was performed on twelve monitoring wells in the area that historically had elevated total chromium concentrations ranging from 10-4900 micrograms per litre. Filtered water samples were found to be free of chromium contamination, indicating that the source of the chromium is the suspended solids. Analysis of these solids by acid digestion and a sequential extraction technique revealed that the chromium was primarily associated with iron-containing solids. X-ray diffraction identified goethite, an iron oxide hydroxide, as the dominant iron-containing phase in the suspended solids. The mineralogy in this region is dominated by interbedded red-bed sandstone and mudstone whose mineral content includes mixed-layer illite-smectite, hematite, goethite, gypsum and dolomite. Elemental analysis of soil samples collected as a function of depth in the locale of the monitoring wells indicated that the iron rich clays contain a natural source of chromium. The elevated levels of total chromium are most likely due to the dissolution of silica and alumina from the chromium containing iron clays in the basic well water, resulting in the release of fine suspended solids that naturally have high chromium concentrations. These results should be applicable to other areas containing iron-rich clays.     

皮革铬鞣废水回收利用中铬渣的铬量测定

本文研究了皮革铬鞣废水中铬的定性特征曲线。利用吸光度加合定律对大量实测数据进行统计处理。建立测定铬的实验室校准直线方程，相关系数γ＝０．９９６０．以此作为测定铬鞣废水及回收铬渣中铬量的实验室回归直线方程。并对本法的可靠性进行研究，结果令人满意。本法不仅大大简化了铬量测定的步骤．而且在提高分析效率的同时获得同等的检测结果。     

火焰原子吸收法测定总铬的最佳酸度条件选择

对火焰原子吸收法测定总铬的酸度介质条件进行了分析和论述。通过在不同的盐酸介质条件下对总铬的实际测定，选择出最适宜的盐酸介质条件，降低了测定空白值，使方法的测定灵敏度有了显著提高。     

无火焰原子吸收石墨炉法测定海水中的总铬

研究了使用无火焰原子吸收石墨炉法测定海水中总铬的分析方法。在氧化过程后采用络合 -萃取技术使共存元素与待测元素分离 ,既消除了基体干扰 ,又达到了富集作用 ,使测定结果准确可靠。方法的相对标准偏差 6.34 % ,回收率85.2 %。     

A Numerical Model for the Transport of Chromium and Fine Sediments

A mathematical model which represents the transport processes of heavy metals and fine sediments in a fluvial stream was developed. The model consists of a three-equation system: the first one for total chromium concentration in the water column, C _Tw, the second one for total suspended sediment concentration, S _w, and the third one for chromium concentration in bed sediments, r. The third equation represents the chromium exchange between the water column and bed sediments by two processes: diffusion of soluble chromium and erosion/deposition of chromium sorbed to sediments. The basic assumption of the model is the instantaneous equilibrium. The main parameters are the partition coefficients in the water column and bed sediments, the depth of the active bed sediment layer, and the mass transfer coefficient between the water column and sediment pore water. The numerical model approximates the equations of advection–dispersion for chromium in water and suspended sediments by using a Eulerian third-order scheme. Numerical vs. analytical solutions were considered satisfactory for different initial, boundary, and sedimentological conditions. In order to estimate the impact of a chromium side discharge, the model was implemented for the Salado River in a reach of 65.6-km long (Santa Fe, Argentina). The results showed the effect of chromium discharge on almost the whole reach, then the vulnerability of the water quality in the Salado River when the flow was low was evidenced. When comparing the computed and measured results, the former showed a reasonable representation of the presence of chromium in water and bed sediments.     

Chromium redox speciation in natural waters

Dissolved hexavalent chromium concentrations were determined in river, estuarine and coastal waters of the Humber catchment in north-east England. Samples were collected, filtered, extracted on site and after storage for up to eight days. Hexavalent chromium concentrations did not change by more than 0.05 microg l(-1) (not significant, p = 0.05) over this period. Total chromium concentrations in the catchment were less than 1.0 microg l(-1). This is low in relation to the proposed Environmental Quality Standard. Hexavalent chromium accounted for between 27% and 100% of the total dissolved concentration, with an average of approximately 50%. The proportion of Cr(III) and Cr(VI) in the rivers and estuary were of the same range as previously measured in 1993. The addition of Cr(III) and Cr(VI) to fresh and saline water samples illustrates the complexity of the factors controlling chromium speciation in natural waters. The presence of oxidisable organic matter and the stabilising role of complexing organic ligands are proposed as the main controlling influences of redox speciation in filtered samples.     

恒电流库仑滴定法测定铬渣中的铬（Ⅵ）

铬渣样品以（１＋１０）磷酸溶液加热消解１．５ｈ,可得到完全澄清的消解液。采用恒电流库仓滴定法测定消解液中的Ｃｒ（Ⅵ）,测得值（１．６４％）与标样参考值（１．７％）接近,准确度高,相对标准偏差为０．９８％。适于铬渣中Ｃｒ（Ⅵ）的日常监测。     

Sampling and analysis considerations for the determination of hexavalent chromium in workplace air

Airborne hexavalent chromium (Cr[VI]) is a known human respiratory carcinogen and allergen. Workers in a variety of industries may be exposed to airborne hexavalent chromium, with exposures frequently occurring via inhalation and/or dermal contact. Analytical methods for the measurement of Cr(VI) compounds in workplace samples, rather than for the determination of total elemental chromium in workplace air, are often desired because exposure limit values for Cr(VI) compounds are much lower than for total Cr. For years, sampling and analytical test methods for airborne Cr(VI) have been investigated so as to provide means for occupational exposure assessment to this highly toxic species. Inter-conversion of trivalent chromium (Cr[III]) and Cr(VI) can sometimes occur during sampling and sample preparation, and efforts to minimize unwanted redox reactions involving these chromium valences have been sought. Because of differences in toxicity, there is also interest in the ability to differentiate between water-soluble and insoluble forms of Cr(VI), and procedures that provide solubility information concerning Cr(VI) compounds have been developed. This paper reviews the state of the art concerning the measurement of airborne Cr(VI) compounds in workplace aerosols and related samples.     

Evaluation of Early Life Stage Fall Chinook Salmon Exposed to Hexavalent Chromium from a Contaminated Groundwater Source

We conducted a laboratory evaluation to assess the risk to early life stage (i.e., eyed egg to swim up) fall Chinook salmon (Oncorhynchus tshawytscha) for exposure to hexavalent chromium from a contaminated groundwater source. Local populations of fall Chinook salmon were exposed to Hanford Site source groundwater that was diluted with Columbia River water. Specific endpoints included survival, development rate, and growth. Tissue burdens of fish were also measured to estimate uptake and elimination rates of chromium. Survival, development, and growth of early life stage fall Chinook salmon were not adversely affected by extended exposures (i.e., 98 day) to hexavalent chromium ranging from 0.79 to 260 μg/l. Survival for all treatment levels and controls exceeded 98% at termination of the test. In addition, there were no differences among the mean lengths and weights of fish among all treatment groups. Whole-body concentrations of chromium in early life stage fall Chinook salmon had a typical dose-response pattern; i.e., those subjected to highest exposure concentrations and longest exposure intervals had higher tissue concentrations. Given the spatial extent of chromium concentrations at the Hanford Site, and the dynamics of the groundwater–river water interface, the current cleanup criterion of 10 μg/l chromium appear adequate to protect early life stage fall Chinook salmon. These findings, together with previous research indicate low risk to these populations.     

Determination of total chromium by flame atomic absorption spectrometry after coprecipitation by cerium (IV) hydroxide

A method for the preconcentration of the total chromium based on coprecipitation with cerium (IV) hydroxide is proposed for determination of chromium by flame atomic absorption spectrometry. Different factors including carrier element amount, pH, sample volume and matrix ion effects for the precipitation were examined. The detection limit of the total chromium (k = 3, N = 15) was 0.18 μg l⁻¹. The presented method was applied for the determination of chromium in the wastewater samples from Kayseri and Nigde Organized Industrial Region-Turkey and in drinking water from our laboratory, Kayseri with satisfactory results (relative standard deviations below 8%, recoveries 95%). The analytical results obtained by the proposed method for certified copper sample was in good agreement with the certified value.