Overview of Precious Metal Content Analysis Methods in Automotive Catalytic Converter

With the increasing awareness of environmental protection, people’s concern of pollution issues arising. Vehicles, as the most important means of transportation, its exhaust emission has received considerable attention. The catalytic converter is able to purify harmful substances in exhaust gas. The absolute content of precious metals in the catalytic converter dominates the exhaust gas purification effect. Accurate detection of precious metal content is of great significance for controlling the cost of catalysts, ensuring catalytic performance and recovering precious metals from spent catalysts. We herein summarized several instruments for precious metals content exploration, such as X-ray fluorescence spectrometer (XRF), atomic absorption spectrometer (AAS), inductively coupled plasma emission spectrometer (ICP) and spectrophotometer. In this thesis, the feasibility of using various devices for characterizing precious metal content in catalytic converters is analyzed and their strengths or weaknesses are elaborated.

Characteristics and Risk Assessment of Soil Heavy Metal Contents in Facility Agriculture of Guangxi

[Objectives]To study the characteristics of soil heavy metal contents in facility agriculture of Guangxi and analyze its risks.[Methods]The heavy metal content of 30 surface soil samples taken from facility agriculture in Guangxi was analyzed.The status of soil heavy metal pollution in facility agriculture of Guangxi was evaluated by the single factor index method,geo-accumulation index method and Hakanson potential ecological risk index method with reference to the soil background value in Guangxi.[Results]Compared with the soil background value in Guangxi,the over-limit rates of heavy metals cadmium,lead,arsenic,chromium,mercury,copper and zinc in soil samples were 56.67%,56.67%,16.67%,30.00%,50.00%,60.00%and 80.00%,respectively.Compared with the screening values of the Soil Environmental Quality-Risk Control Standard for Soil Contamination of Agricultural Land(for trial implementation)(GB15618-2018),the overlimit rates of the heavy metals cadmium,arsenic,copper and zinc in the surface soil of agricultural facilities in Guangxi were 56.67%,10.00%,16.67%and 23.33%,respectively.Except for the average content of soil cadmium exceeding the screening value,the evaluation content of the other six soil heavy metals did not exceed the screening value.According to the evaluation results of the single factor pollution index method,the surface soil arsenic and chromium of the agricultural facilities in Guangxi belonged to the clean level,lead,mercury,and copper belonged to mild pollution,and cadmium and zinc belonged to moderate pollution.According to the evaluation results of the geo-accumulation index,the lead,arsenic,chromium and mercury in the surface soil of the agricultural facilities in Guangxi belonged to the pollution-free level,while the cadmium,copper and zinc belonged to the mild-moderate pollution.According to the evaluation results of the potential ecological risk index method,the potential ecological risks of the heavy metals of lead,arsenic,chromium,copper and zinc in the soil of agricultural facilities in Guangxi belonged to low potential ecological risk level,and the potential ecological risks of cadmium and mercury belonged to moderate risk level.The potential ecological risk index(RI)of the seven heavy metals in the soil was 132.46,which belonged to moderate potential ecological risk.The largest contribution of soil heavy metals to the potential ecological risk index was cadmium and mercury.[Conclusions]Taking the soil of facility agriculture in Guangxi as the object,this paper studied the characteristics of heavy metal content in facility agricultural soil and its risk assessment,in order to provide a scientific basis for facility soil heavy metal risk prevention and control and provide safe technology for facility agriculture.

Heavy Metal Content in Chinese Vegetable Plantation Land Soils and Related Source Analysis

According to the previous literature published since 1989, statistical analysis for reported data on the heavy metals in Chinese vegetable plantation soils was carried out systematically in this article. The purpose of this investigation was to study the status of heavy metal content in vegetable land soils systematically through objective assessment to promote the development of vegetable production with high quality and efficiency. It is concluded that Zn, Cr, Cu had relatively high concentrations while the mean concentrations of toxic metals, As, Hg, Cd were 8.03, 0.12, 0.28 mg·kg^-1, respectively with comparatively low concentrations in Chinese vegetable land. Comparing to Clainese Soil Quality Criterion GB 15618- 1995 （6.5 〈 pH 〈 7.5）, about 24.1, 10.3, and 9.2% of the total samples was contaminated by Cd, Hg, and As, respectively, and the descending order of heavy metals was Cd 〉 Hg 〉 As 〉 Zn 〉 Cu 〉 Cr 〉 Pb. When compared among different regions, the more serious heavy metal contamination was found in the vegetable land of eastern China and the main contamination elements were Cd, Hg, and Zn. In the mid region, vegetable plantation land soil was mainly polluted by As and Cd, as well as by Hg, Zn, and Cu, to some extent. In the west region of China, Cd and As contamination was also observed to some degree, along with few soil samples exceeding the grade Ⅱ level of GB 15618-1995 （6.5 〈 pH 〈 7.5） for Cu, Cr, and Hg content. Compared to the five vegetable plantation land patterns, the highest concentration of As, Cd, Hg, and Zn occurred in the industrial/sewage irrigation vegetable land, especially for Hg with 2.36 mg·kg^-1 content averagely, which is 10.5-21.1 times higher than the other four types of vegetable lands. The highest concentration of Cn and Cr occurred in the greenhouse vegetable land soils, and urban vegetable land soil had the highest Pb content in comparison with the other types of vegetable plantation land patterns. By analyzing heavy metal content under different vegetable land patterns, it was found that soil in vegetable production base had relatively low heavy metal concentrations except for Pb with a slightly higher amount in the suburb area. The soil quality of common vegetable land was good with the lowest concentrations for most heavy metals. Under present utilization patterns of vegetable land, the soil quality in Chinese vegetable base land was good with comparatively low concentrations of heavy metals and mostly not exceeding the grade II level of Chinese Soil Quality Criterion GB 15618-1995 （6.5 〈 pH 〈 7.5）. However, comparatively serious contamination was found in industrial/sewage irrigation and suburb vegetable land soils.

Heavy metal content in scalp hair of the inhabitants near Dexing Copper Mine,Jiangxi Province,China

Levels of seven metals(Mn,Cu,Zn,Pb,Cr,Cd,and Se) in the scalp hair of Daicun and Xiangtian inhabitants were determined by ICP-MS/AFS.Daicun,as an experimental site,is near Dexing Copper Mine,Jiangxi Province,China,and exposed to mining pollution;Xiangtian,as a control site,is free from any mining and other industrial pollution.The heavy metal distribution in the scalp hair of the two diverse population segments exposed to different environments was discussed against the background of the heavy metal content of local plants,waters,and soils.The results show:1) Levels of Cu,Zn,Pb,Cr,and Cd in the scalp hair of Daicun inhabitants were higher compared with Xiangtian counterparts which showed higher comparative levels of Se and Mn.But there were no significant differences of the levels of Cu and Zn in the hair samples between the two villages.In the hair of the inhabitants in the two villages,the levels for Se,Zn,and Cu were lower,while the level for Mn was higher,than the corresponding levels from other regions of the world.Compared with the standard issued by the Trace Element Research Council of China for Chinese inhabitants there were serious Se,Zn,Cu and Cr-deficiency phenomena in the hair samples from Daicun and Xiangtian.2) Against the geological background of high levels of Zn,Cu,Se and Cr,there were deficiencies of Zn,Cu,Se and Cr in the hair samples of the Daicun population.This may have been caused by the distribution forms of the heavy metals in the soils,and antagonism among the elements.3) Principal Component Analysis(PCA) and Cluster Analysis(CA) indicated that the origins of the heavy metals in the hair samples from the two villages had some differences as well as some similarities,this should be contributed mainly to the influence of the mining activities.

Content Analysis of Baicalin and Heavy Metals in Scutellaria baicalensis Georgi Cultivated in Jizhou District

This study aimed to explore an analysis method for baicalin in Scutellaria baicalensis Georgi and make a reference for the analysis of the medicinal value of S. baicalensis cultivated in Jizhou District. The content of baicalin in S. baicalensis cultivated in Jizhou District was determined using high-performance liquid chromatography( HPLC) to judge whether it met the requirements of Chinese Pharmacopoeia; and according to the requirements of the Chinese Pharmacopoeia of 2015 edition,the contents of heavy metals were determined by ICP-MS. The results showed that the contents of baicalin,Cr,Cu,As,Cd and Pb in S. baicalensis planted in Jizhou District were 14. 625 05%,11. 360,12. 830,0. 062 315,0. 025 715 and 0. 176 65 μg/g,respectively. The content of baicalin in S. baicalensis planted in Jizhou District was much higher than the standard( ≥ 9. 0%) of Chinese Pharmacopoeia of 2015 edition,and the contents of heavy metals were also below the limit( ≤20/1000 000) required by Chinese Pharmacopoeia of 2015 edition.

Fuzzy Prediction of Silicon Content for BF Hot Metal

Some key operation variables influencing hot metal silicon content were selected, and time lag of each of them was obtained. A standardized fuzzy system model was developed to approach the random nonlinear dynamic system of the change of silicon content, forecast the change of silicon content and calculate silicon content. The prediction of hot metal silicon content is very successful with the data collected online from BF No. 1 at Laiwu Iron and Steel Group Co.

Influence of sulfur addition/solids content ratio on removal of heavy metals from mine tailings by bioleaching

The effect of sulfur addition/solids content(SA/SC)ratio on heavy metals(e.g.copper,zinc and lead)obtained from mine tailings by indigenous sulfur-oxidizing bacteria was studied,and the changes in the chemical forms of heavy metals after bioleaching were explored.The results show that the solubilization of metals is significantly influenced by SA/SC ratio,and SA/SC ratio of 2.50 is found to be the best for bacterial activity and metal solubilization among six SA/SC ratios tested(such as 1.00,1.33,1.50,1.67,2.00 and 2.50)under the chosen experimental conditions.The pH decreases fast and the maximum solubilizations of copper and zinc are respectively 81.76% and 84.35% while that of lead only reaches 40.36%.After bioleaching,the chemical forms of heavy metals have changed.The metals remained in mine tailings are mainly found in residual fractions,which is harmless to the surrounding environment.

Chaotic Identification and Prediction of Silicon Content in Hot Metal

The time series data of silicon content in hot metal were identified to have the chaotic feature because of the positive maximum Lyapunov exponent, and then the time scales to predict future were estimated. Finally a chaotic local-region model was constructed to predict silicon content in hot metal with good performance due to high hitting rate.

Statistical characteristics of heavy metals content in groundwater and their interrelationships in a certain antimony mine area

In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in groundwater of metal mine. In this research, a certain antimony mine area is selected as a typical study area. Also, the study about statistical characteristics of heavy metals in groundwater has been carried out. Furthermore, the interrelationships have been preliminarily discussed through related analysis, such as relevant analysis, cluster analysis and principle component analysis. The results show that: the excessive elements in groundwater of study area are Sb, As, Pb, Se, and Ni. The average mass concentration of Sb, As, and Pb is higher than that of drinking water standards(GB5749-2006). The concentration of most heavy metals in dry season is lower than or equal to that in wet season for groundwater. Zn is the only metal in groundwater showing a different pattern, the concentration of which in dry season is higher than that in wet season. Under the impacts of stratum leaching and absorption effect, the concentration of heavy metals(except Pb and Ba) in groundwater are lower than or equal to that in surface water. As and Se, the two heavy metals have a significant positive correlation, which shows the two elements might have gone through similar environmental geochemical effect. Also, the connection among Zn, Hg, Pb, and Mn is not obvious; therefore, the sources of those elements are quite different. In addition, the elements of Se and As have obvious positive interrelationship with elements of CO_3^(2-) and F^-. Also, the Pb has significant positive correlation with PO_4^(3-), H_2SiO_3 and oxygen consumption. The results of cluster analysis show that 9 different heavy metals in the study area can be divided into 3 categories: Zn, Cd, Mn, Hg, Cu, and Cr belong to the first category, Se and As belong to the second one, and the last category is Pb. Also, the principle component analysis divides 6 heavy metals(Zn, As, Hg, Pb, Mn, and Se) into 4 different principle components, which can be utilized to assess heavy metals pollution situations in groundwater. The reliability of this method is higher than 91%. Moreover, the research provides theory basis and models for establishing evaluation index system and exploring the evaluation method of heavy mental pollution in groundwater.

Contents of Trace Metal Elements in Cow Milk Impacted by Different Feedstuffs

Feedstuff intake plays key role in impacting the yield and quality of milk. In this study, we discussed the contents of trace metal elements in cow milk impacted by different feedstuffs. We detected the contents of Pb, Cd, As, Cu, Mg, Ca, Fe and Zn in different feedstuffs and milk by atomic absorption spectrophotometry. The determinations of Pb, Cd and As contents were by graphite furnace A_AS and Cu, Mg, Ca, Fe and Zn was by flame atomic absorption spectrometry. The results showed that Pb, Cd, As and Cu presented in feedstuffs, but Pb, Cd and As were lowly detected in milk samples, and Cu was not detected in milk samples. The content of Mg in concentrates was lower than that in forages. However, the content of Mg in milk from concentrate feed was higher than that in forage feed. This suggested that the utilization of Mg in concentrate feed was higher than that in forage feed. The contents of Ca and Zn were opposite to Mg, and the utilization of Ca and Zn in forage feed was higher than that in concentrate feed. There was no obviously change law of Fe in different feedstuffs and milk samples. The relationship between the contents of trace metal elements in milk to feedstuffs would provide a theoretical basis for dairy farming. It would be useful for improving the milk yield and milk quality of dairy production.

Investigation on Steelmaking with Hot Metal Containing Low Silicon Content in Large Converter

There are some problems in steelmaking with hot metal containing low silicon content such as difficulty in slag formation, less slag for dephosphorization and slag adhesion on oxygen lance and hood. To overcome these problems, experiments wcrc conducted and some improvements were obtained, such as adding appropriate flux, increasing the lance position slightly during steelmaking and using effective multi-outlet nozzle. Moreover, to keep normal heating rate, the ore and scrap charge should be reduced due to less chemical heat input in steelmaking.

硒对云南白灵芝生长、品质及DNA甲基化特征的影响

采用田间覆土栽培试验,设置6个Se浓度(0、50、100、200、300、400μg/g)处理,分别记为CK、Se50、Se100、Se200、Se300、Se400,研究外源硒对云南白灵芝生长发育、重金属积累、生物活性成分含量及其DNA甲基化特征的影响。结果表明,与CK相比,外源Se对子实体柄长和菌盖大小(横径、纵径)无显著影响,但能显著降低菌盖厚度;随着Se施用水平提高,菌丝生长速率和子实体硒含量均呈先增后降的趋势,生物量呈先降后增再降的趋势。子实体重金属含量(As、Cd、Pb、Hg)随Se浓度增加呈持续降低趋势,线性分析也表明,重金属含量与Se施用浓度均呈显著负相关。施Se增加了子实体多糖、粗蛋白、黄酮及总氨基酸含量,其中,多糖、黄酮含量在Se400处理下最高,总氨基酸、粗蛋白含量分别在Se200、Se300处理下最高。HPLC测定分析表明,与CK相比,Se300提高了灵芝酸A、灵芝酸DM、灵芝酸F及灵芝酮三醇为主的三萜酸组分,其总三萜酸含量较其他处理提高2.93%~25.54%。敏感扩增多态性分析(MSAP)结果显示,Se300较CK、Se400相比具有较高的未甲基化位点比例和较低的甲基化位点比例。综上,施用外源硒可促进早期菌丝生长,提高子实体生物量累积,改善子实体重金属安全性能和生物活性成分品质,改变DNA甲基化比例,且以300μg/g施用浓度的整体效果最佳,其子实体产量较对照显著提高11.36%。

上海市奉贤区农田土壤-农产品中的重金属含量特征和污染评价

为分析奉贤区农田土壤和农产品的重金属污染状况,采集粮田、菜田和果园3种作物的农田土壤及其对应农产品,分别测定土壤8种重金属元素(Hg、As、Cd、Cr、Pb、Cu、Zn和Ni)和农产品5种重金属元素(Pb、Cd、Cr、As和Hg)的含量特征,采用单项污染指数法、综合污染指数法、积累指数法和富集因子等方法对土壤-农产品中重金属元素进行污染风险评价,并将地统计学与因子分析相结合分析农田土壤重金属的空间分布特征。结果表明:与上海市土壤背景值相比,奉贤区农田土壤Hg、Cd、Cr、Zn和Ni的平均含量较高,分别是背景值的1.40、1.36、1.06、1.15倍和1.44倍。单项及综合污染指数值显示土壤重金属处于无污染水平;但Cd、Ni、Hg元素的积累指数值显示无-中度污染水平,其中有4.92%农田土壤处于Hg元素的中度污染。在空间分布上,Hg呈连片分布;As、Cd整体含量低,南北区域分布;Cr、Zn呈条带状分布,自南往北递增状态;Pb呈散点状分布;Cu元素整体含量高,呈东西梯度分布;Ni元素呈岛状分布。因子分析中,因子1包括Cu和Zn,因子2是Pb,因子3包括Cd、Cr,因子4是Ni,因子5是As和因子6是Hg。奉贤地区土壤重金属含量主要受到工业源、农业源、交通源和自然源影响较大,应加强污染源控制,降低风险水平。农产品样中的5种重金属均未超出标准限量值,单项及综合污染指数值显示农产品重金属属于清洁水平。经土样和农产品样中的重金属含量相关性分析,两者无相关,农产品对土壤重金属的富集因子较小。不同土地利用方式对土壤和农产品中重金属含量影响较大,菜地土壤和农产品对Cd较为敏感,吸收能力较强,而果园土壤和农产品对各重金属吸收总体较弱。在农业生产中可以根据作物吸收重金属特性来调整种植结构,以减轻重金属污染。综合来看,奉贤区土壤-农产品系统中重金属累积程度低,但局部农田土壤中重金属含量存在轻微污染,需引起重视。

干旱区绿洲农田土壤重金属含量高光谱反演

对新疆渭库绿洲土壤样本的As、Hg、Pb、Cr、Zn和Cu共6种重金属含量与高光谱关系进行分析,基于逐步回归方法筛选出特征波段,采用地理加权回归(GWR)和普通最小二乘法回归(OLS)构建土壤重金属的高光谱反演模型.结果显示:1)研究区的6种重金属元素含量存在一定的差异,土壤中的平均重金属含量依次为Zn>Pb>Cr>Cu>As>Hg,均未超过国家土壤背景值.研究区的Pb平均含量高于当地(新疆)土壤背景值,即研究区表土层中的Pb元素明显富集;2)不同的光谱变换使土壤重金属的光谱特征均得到了增强,但强度有所差异,经过二阶微分变换(SD)和一阶立方根微分变换(CRFD)的土壤光谱相对于原始光谱增强最显著;3)从模型验证来看,在反演6个土壤重金属元素含量时,GWR的R^(2)高于OLS,其中Zn的R^(2)接近0.8,Cu的R^(2)接近0.6,表明模型有一定预测能力,而As、Hg、Pb和Cr的R^(2)均依然低于0.5,模型预测能力并不理想;4)两种模型预测的6种土壤重金属含量的空间分布表现出一定的空间差异性.其中,As元素空间分布差异在这两种预测模型中最大,而其余5种重金属元素Hg、Pb、Cr、Zn和Cu的分布则较为均匀.通过高光谱反射率估算土壤重金属元素含量,实现了干旱区绿洲农田土壤重金属元素含量的高效快速反演,为干旱区绿洲农田土壤重金属元素含量动态监测提供了可靠的技术支撑.

电动土工塑料排水板修复重金属污染高岭土试验研究

针对重金属锌和镉污染的低渗透性高岭土,采用电动土工塑料排水板(EKG)作为电极材料,通过自制模型试验装置研究了电动修复中电势梯度、通电时间、含水率对重金属去除率的影响,确定电动修复的最优试验条件。在最优试验条件下,开展了电极材料、电势梯度对不同种类重金属去除效果影响的试验研究。结果表明:随着修复时间的增长,阳极处重金属污染物逐渐减少,阴极处重金属污染物富集逐渐增加;试验条件相同情况下,重金属污染物Cd的除去率明显高于Zn;电势梯度越大,重金属Zn离子的去除率越高;电动土工塑料排水板作为电极的电动修复重金属污染土的效果要优于石墨电极。研究有助于揭示电动修复重金属污染土的效果和机理,为电动生态环境修复技术的应用提供技术支持。

猪场沼液还田对土壤和植物重金属含量的影响

还田消纳是猪场沼液资源化利用的主要方式。由于沼液中含有多种金属元素,过量浇灌会引发土壤重金属污染。目前,关于猪场沼液对耕地土壤和植物重金属污染特征的影响及其影响因子的研究还不够深入。在广西生猪养殖区,选取了4种不同耕地利用类型(叶菜类、果树类、饲草类、药草类)和14个样地,就不同沼液浇灌强度对土壤与植物重金属的影响规律及其影响因子进行研究。结果表明:在14个样地0~40 cm表层土壤中,重金属Cu、Zn、Cd的输入强度最大,且其含量和土壤pH变化和与沼液浇灌总量呈显著(p<0.05)正相关;在4种耕地类型中,杂交象草和空心菜的可食用部分Cu、Zn、Cd、Pb、Cr含量与沼液浇灌总量呈显著正相关;在沼液还田中,由于Cu、Zn的输入强度大,而植物对其的富集系数又较低,因此土壤中Cu、Zn积累较快;浇灌沼液对叶菜类和果树类的主要污染风险是Pb和Cd,而对杂交象草的污染风险较小。

飞灰粒径对金属波导内飞灰含碳量测量影响

微波衰减法是近年来在线测量粉煤灰含碳量的常见方法之一。然而,由于飞灰的取样位置及取样装置的差异,飞灰的粒径大小存在较大的不确定性,从而造成飞灰含碳量测量的误差较大。现有的含碳量拟合模型均以飞灰对特征频率信号的衰减与飞灰含碳量的关系为基础,存在着误差大、适应性差等问题。为了解决含碳量拟合模型误差大和适应性差等问题,提出使用信号的时域主峰衰减来代替信号在特征频率处的衰减作为飞灰含碳量在线拟合的优化方法。为了修正飞灰粒径不确定性引起的误差,在研究灰位和含碳量测量的基础上,比较了不同粒径范围的飞灰对灰位和飞灰含碳量测量的影响。结果表明:采用信号的时域峰值衰减来计算含碳量,其结果与实际值吻合良好;对于波导中相同质量的灰样,飞灰的粒径大小对灰位的测量精度没有显著的影响;当使用微波法测量波导内飞灰含碳量时,对于相同质量的灰样,随着飞灰粒径的减小,波导内飞灰对微波信号的衰减逐渐减小,从而使含碳量的测量值随着飞灰粒径的减小而增加。

成都市某社区不同类别人群头发中重金属的含量特征

采用ICP-MS测定成都市某社区33位居民头发中Cr、Mn、Co、Ni、Cu、As、Mo、Cd、Sb、Tl、Pb共11种重金属的含量,分析其分布特征及主要影响因素。与相关文献推荐的正常范围值相比,研究区居民未受Tl污染。头发中Cu、As、Sb及Pb有超标现象,超标率分别为15.2%、3.0%、6.1%及15.2%。其中1位居民的发As含量(2.35μg/g)是推荐正常值范围限值的2.8倍,与其在工厂中的职业暴露有关;其次是接触电子产品较多的6号居民(0.52μg/g)与16号居民(0.5μg/g)发As含量明显高于其他居民。仅有1位食堂职工的发Cu含量超过推荐范围,主要与其职业/生活习惯有关。统计检验表明,只有Mo含量与性别相关(P<0.05)。Mn、Co、As、Tl含量在各年龄组间差异极显著(P<0.01)。抽烟人群头发中重金属含量与不抽烟人群无显著差别。相关性分析发现多种重金属间存在正相关关系。Co的单项累积污染指数在男女性中均为最高。男性的综合累积污染指数(3.12)低于女性(5.30)。