某矿区土壤重金属分布特征及来源解析

为探究赣南某矿区土壤重金属污染状况及来源,以该矿区内40个土壤样品为研究对象,分析了土壤中Cu、Pb、Zn、Cr、Ni、Cd、As和Hg等8种重金属元素的含量,并采用频率直方图、相关性分析、主成分分析等多种统计方法探究了土壤重金属含量的分布特征及来源。研究结果表明:(1)研究区8种重金属中有7种不同程度地超过了江西省土壤重金属元素背景值;(2)Pb、Zn、As和Hg的含量接近正态分布,而Cu、Cr、Ni和Cd的含量则呈现出右偏分布的趋势,这可能与研究区矿山开采活动及土地利用类型等因素有关;(3)矿区土壤重金属相关性分析表明,Cu、Cr、Ni的同源性较高,可能具有相同的污染源,而Pb、Zn、Cd等元素与Cu、Cr、Ni相比,其来源可能存在一定的差异;(4)主成分分析结果显示,矿区内土壤中8种重金属元素含量可以由2个主成分来解释,所代表的实际意义按贡献率排序分别是成土母质和人为采矿活动;(5)矿区内土壤重金属污染物主要为Pb、Zn、Cd,人为采矿活动是这三种重金属污染的主要来源。     

南宁市郊周边农田土壤-农作物系统重金属元素迁移特征及其影响因素

通过采集南宁市郊农田中玉米、蔬菜、水稻可食部分及其根系土150组,研究重金属元素在不同土壤-农作物系统中迁移特征及其影响因素,结果表明:根系土中Hg、Cd、Cr、Cu、Ni、Pb、Zn平均含量分别为0.116、0.202、56.76、22.12、14.49、25.18和56.28 mg·kg-1。农作物对应平均含量分别为0.001 1、0.037、0.054、1.153、0.205、0.011和9.37 mg·kg-1。根系土富集因子表明Cd受到不同程度人为活动影响,Cr和Ni主要受地质背景控制;不同作物系统元素富集因子表明Pb在土壤-农作物系统中迁移能力最低,Zn迁移能力最强。Cd、Cr、Cu、Ni、Pb和Zn在土壤-水稻系统重迁移能力显著高于蔬菜和玉米。根系土中pH、CaO、有机质、Fe2O3、K2O、MgO与重金生物富集系数呈显著性负相关,但在土壤-叶类蔬菜系统中根系土中K2O、MgO与Hg生物富集系数呈显著正相关。      

Environment impact of heavy metals on urban soil in the vicinity of industrial area of Baoji city,P.R. China

Heavy metals in soils are of great environmental concern, in order to evaluate heavy metal contents and their relationships in the surface soil of industrial area of Baoji city, and also to investigate their influence on the soils. Soil samples were collected from 50 sites, and the concentration of Pb, Zn, Cu, Cr, Ni heavy metals and the contents of characteristics in soil from industrial area of Baoji city were determined with X-ray fluorescence method. The concentrations of Pb, Zn, Cu, Cr and Ni in the investigated soils reached the amount of 2,682.00–76,979.42, 169.30–8,288.58, 62.24–242.36, 91.96–110.54 and 36.14–179.28 mg kg⁻¹, respectively. The major element Pb contents of the topsoils were determined. to highlight the influence of ‘anthropic’ features on the heavy metal concentrations and their distributions. To compare, all values of elements were much higher than those of unpolluted soils in the middle of Shaanxi province that average 16.0–26.5, 67.1–120.0, 17.8–57.0, 46.9–65.6 and 24.7–34.6 mg kg⁻¹ for Pb, Zn, Cu, Cr and Ni, respectively. An ensemble of basic and relativity analysis was performed to reduce the precipitate of Pb in soil was extremely high and greatly relativity with other elements. Meanwhile, Pb, Zn, Cu, Cr, Ni heavy metals were typical elements of anthropic activities sources, so it was easy to infer to the tracers of anthropic pollutions from the factorial analysis, which was coming from the storage battery manufactory pollutions. The pollutant distributions were constructed for the urban area which identified storage battery manufactory soot precipitate as the main source of diffuse pollution and also showed the contribution of the topsoils of industrial area of Baoji city as the source point of pollution. Consequently, the impact of heavy metals on soil was proposed and discussed. These results highlight the need for instituting a systematic and continuous monitoring of heavy metals and other forms of pollutants in Baoji city to ensure that pollution does not become a serious problem in the future.     

固体聚合膜电解浓集法测量天然水中低含量氚的化学淬灭效应研究

固体聚合膜电解浓集法是浓缩氚含量较低(1 Bq/m~3)的天然水样的常用方法,但因水样自身含有杂质离子或电解装置聚合膜带入杂质进入浓集液,使浓集液偏酸性,在测量过程中易产生化学淬灭效应,导致氚的测量值偏低。本文研究了水样自身存在的杂质离子和聚合膜上残留的杂质离子、样品溶液的pH值及其电导率所产生的化学淬灭效应的影响,实验表明,为减少化学淬灭效应,提高测量低含量氚的准确性,需保证水样溶液呈中性,电导率≤1μS/cm,同时避免杂质沉积在聚合膜上。如果水样溶液的pH值偏酸性、电导率大于1μS/cm,可采用酸碱混合型离子交换树脂去除水样中自身的杂质;对于聚合膜引入的杂质,可在电解后的水样中加入微量氨水将其pH值调节至中性。     

福建铁观音茶园生态地球化学特征

东南沿海是铅等重金属的地球化学高背景区。该地区广泛分布酸性红壤,酸雨沉降、不适当施肥导致土壤酸化以及由此引发土壤重金属生态风险令人关注。以福建省铁观音主产区为研究区,采集了79个茶园的表层和亚表层土壤样、茶叶样品,测定了重金属元素以及土壤常量元素和理化指标。研究表明,福建铁观音茶园土壤中Hg、Pb、Se、Zn高含量主要由地质背景所引起,土壤常量组分、有机质、酸碱度等理化条件对土壤元素含量有一定的影响;铁观音茶树老叶中As、Cd、Cr、Hg、Se、Pb、F等非植物营养元素含量明显高于嫩叶,显示这些元素随植物生长逐渐累积的特征,而嫩叶中植物生长必需的营养元素Cu、(Ni)、Zn则高于老叶,反映出微量营养元素在茶叶生长部位相对富集的特征;多数情况下土壤与茶叶间元素含量相关性差,说明茶树对土壤元素的吸收累积受到多种复杂因素的影响。研究表明茶叶与土壤Pb、Cr具有显著正相关性,为建立铅污染土壤生态效应预测评价模型提供了基础依据。     

Effect of different industrial activities on heavy metal concentrations and chemical distribution in topsoil and road dust

The development of industrial activity in recent years has promoted the pollution in this environment causing health problems to workers and the neighbourhood nearby. In order to determine the influence of different industrial activities in metals concentration and behaviour in soil and road dust, samples from three different industrial areas (service industry; refinery, fertilizer and power industry; and tannery industry) and a natural area were collected. Physical–chemical properties, metal content (Pb, Zn, Cu, Cr, Co, Ni) and the chemical distribution of metals were carried out. Results show largest accumulation of metals in road dusts samples for all industrial areas, being Zn, Pb, Cr and Cu the metals with highest concentrations. Each industrial activity contributes differently to the concentration of metals in soil and dust, and the highest concentrations of Cr were found from tannery industries, while Pb and Zn showed the highest concentration from refinery and fertilizer industry. It has been showed that industrial activity has influence on the physicochemical properties of soil and road dust and on the bioavailability of all metals. Chemical partitioning indicates that Pb, Zn, Cu and Cr distribution in the different solid phases is affected by industrial activity, while Co and Ni distribution is not affected by the industrial activity.     

An assessment study of heavy metal distribution within soil in upper course of Zarqa River basin/Jordan

Levels of heavy metals are found in soils and waters of the major tributary valleys of the Jordan Valley. Heavy metal content in soils irrigated by treated waste water were measured for a 40 km reach of Zarqa River. Soil samples from eight different sites along the upper course of this river were analyzed to determine the concentration of selected heavy metals (CO, Cr, Cu, Pb, Ni, Zn). Silt forms the major component of the soils with an average of 54%. Clay fractions show an increase with depth from 17 to 41%. Trends in particle size distribution and metal contents were compared across sample sites. Samples contained moderate to considerable levels of Pb and Ni. Concentrations of Cu and Cr ranged between 33–59 and 65–90 ppm, respectively. These values represent a slight to moderate class of pollution. The concentration of Cr shows a decrease with depth and distance from the waste water plant. Cu, Zn, and Ni show increasing concentrations with depth but Pb and CO do not. The concentrations of the measured heavy metals increases near the waste water treatment plant but decreases with distance from the plant due to precipitation in the stream bed and dilution with stream water. This decline in metal content with distance from the treatment plant suggests that most metals reaching floodplain soils may derive from the same source. Although current metal concentrations are low to moderate, floodplain surface soils in this area should be regarded as a potential source for future heavy metal pollution downstream.     

宁沪高速公路句容段两侧土壤磁化率异常与重金属元素的关系研究

高速公路两侧土壤的磁化率从路中央向两侧具有逐渐降低的特征,相对应的样品中的重金属Cu、Pb、Zn、N i、Cr、Fe等元素的含量也具有从路中心向两侧逐渐降低的现象。相关分析表明,土壤磁化率与土壤中的Cu、Pb、Zn、N i、Cr、Fe的相关性显著,因而可以利用磁化率异常来指示高速公路两侧土壤的重金属污染状况。元素的赋存形态分析表明铁锰氧化物态与残渣态是Cu、Pb、Zn、N i、Cr、Fe的主要赋存形式;各元素的形态分析结果与土壤磁化率的相关统计分析表明,高速公路两侧土壤的磁化率与可交换态中的Cu、Pb、Zn、铁锰氧化物态中的Fe、Pb、Zn、有机还原态中的Cu、Cr、Fe、Zn和残渣态中的Cu、Pb、Zn、Cr、Co、N i具有明显的相关性。     

Temporal variability of selected heavy metals in automobile soils

Studies on seasonal changes of heavy metal concentration in soils provide vital information for best management options at all times. The study investigated temporal variation in concentration of heavy metals in three towns having automobile service centres in Imo State. The study site is characterized by two major seasons in a year. Heavy metals were found in both arable and automobile soils, but more concentrations were recorded on the latter. Mean values of Cd, Cr, Ni, Hg and Pb were 6.2 mg/kg, 4.7 mg/kg 6.5 mg/kg, 0.02 mg/kg and 71.9 mg/kg respectively in the dry season while 2.9 mg/kg Cd, 2.2 mg/kg Cr, 1.9 mg/kg Ni, 0.01 mg/kg Hg and 51.9 mg/kg Pb were recorded during the rainy season of the experimental period. Higher values of heavy metal concentration were found in automobile soils as follows: 18.1 mg/kg Cd, 12.0mg/kgCr, 16.3 mg/kg Ni, 4.8 mg/kg Hg and312.8 mg/kg Pb in rainy season, and 15.1 mg/kg Cd, 8.1 mg/kg Cr, 11.9 mg/kg Ni 2.7 mg/kg Hg and 267.9 mg/kg Pb. However, Cd showed highest variability in arable soils during the dry season (CV=79%) while Hg varied widely in automobile soils in the rainy season (CV=54%).     

Distribution of heavy metals in Gaborone urban soils (Botswana) and its relationship to soil pollution and bedrock composition

The capital city of Botswana, Gaborone, has seen unprecedented population, economic, and industrial growth in recent years. In order to assess how this rapid urbanisation process impacts the environment, 106 silt and clay (particle size <0.053 mm) samples, separated from Gaborone surface soil samples representing urban, agricultural and rural sites, were investigated. The concentrations of nine heavy metals (Sc, Cr, Co, Ni, Cu, Zn, Nb, Cd, and Pb) were measured using ICP–MS and GFAAS, and the resulting patterns were correlated to the bedrock composition and anthropogenic activities. As expected, we found that samples from soils on top of dolerites show higher levels of Cr, Ni, and Cu than those on top of granites and rhyolites. However, our studies also show that Gaborone city centre soils are moderately polluted by Pb (up to 222 mg/kg, i.e. 5.7-fold the concentration in comparable rural soils), as a result of heavy traffic. Furthermore, Cr and Ni pollution originating from agrochemicals were shown to be accumulating in Gaborone crop soils. Our studies also showed moderate levels of Zn pollution and low level, dot-shaped pollution of Cr, Co, Ni, Cu detected in Gaborone residential and industrial soils that are correlated to waste disposal. Interestingly, the highest levels of Sc, Cr, Co, Ni and Zn pollution are found near two abandoned sewage works. The results of sequential extraction indicate that the polluting Co and Ni exist in all speciations; the polluting Cu mainly exists in the residue of the sequential extraction, whereas the polluting Pb is mostly bound to organic matters and Fe- and Mn-oxides. These results highlight the need for instituting a systematic and continuous monitoring of heavy metals and other forms of pollutants in Gaborone to ensure that pollution does not become a serious problem in the future.     

典型铜镍矿区周围环境介质中重金属及其化学形态分布特征

重金属污染是金属矿山开采和冶炼所引起的主要环境问题。对甘肃省典型矿业城市金昌市周围农田土壤、废渣堆表面风化物及降尘、尾矿坝尾矿砂和尾矿坝旁排污沟沉积物中Cr、Cu、Ni、Pb、Zn含量及其化学形态进行分析。结果表明:不同区域环境中重金属呈现不同程度累积,其中以Cu、Ni最为显著,含量由高到低依次为尾矿坝排污沟>尾矿坝>废渣堆>农田土壤;尾矿砂和沉积物中重金属分布以Ni含量显著高于Cu含量为特征;而农田土壤和风化物及降尘中重金属分布以Cu含量高于Ni含量为特征,前者Cu、Ni主要来源于尾矿,后者与冶炼烟尘排放有很大关系;样品中除Cr、Zn以残渣态为主外,Cu、Ni、Pb化学形态分布有较大差异,Cu以可氧化态和残渣态为主,Ni以可还原态为主,其次为弱酸提取态,Pb以可还原态为主,其次为残渣态。土壤理化性质是影响重金属化学形态分布的重要因素。     

海水入侵水质变化模拟实验研究

通过模拟海水入侵地下水过程的实验,研究了青岛地区海水对不同土壤浸泡上清液中各种元素的变化,得出了海水入侵过程中常规离子如Cl-、HCO3-、P和Ca2 的变化规律。与此同时,海水含有一定量重金属。在与不同土壤浸泡过程中,实验中分析了Ni、Cd、Cr、Pb、Cu、Mn和Zn共7种元素。上清液中Ni、Cd和Zn浓度增加,Pb、Cu和Cr的浓度略有降低或基本不发生变化。用饮用水和蒸馏水分别与不同土壤浸泡作参比实验,上清液中各种元素基本不发生变化。浸出液中基本上不含重金属。另外,应用海水、饮用水和蒸馏水与不同土壤浸泡时,所有上清液中均未检测出Mn元素。因此,海水入侵过程中,地下水不仅变咸,也使地下水重金属增加。     

Sorption and distribution of adsorbed metals in three soils of India

The mobility and bioavailability of heavy metals depends on the metal retention capacity of soil and also on the geochemical phases with which metals are associated. Laboratory batch experiments were carried out to study the sorption and distribution of Cd, Ni and Pb in 3 soils differing in their physicochemical properties from India: Oxyaquic Haplustalf (SL1), Typic Haplustalf (SL2) and Typic Haplustert (SL3). The heavy metal adsorption was studied by isotherms and the distribution coefficient (K_D) for each metal was obtained from the linear regressions of the concentration of metal remaining in equilibrium solution and the amount adsorbed. In general, the sorption capacity for all the metals decreased in the order: SL3>SL2>SL1. Among metals, the sorption capacity in all the soils decreased in the order: Pb>>Ni>Cd. Distribution of sorbed metals at various equilibrating concentrations was studied by sequential extraction. Results showed significant differences in the distribution of metals in these soils. At higher additions (such as 200 μM l⁻¹) most of the metals were extracted in their more mobile fractions, exchangeable and/or inorganic in contrast to their original partitioning in soils, where they were preferentially associated with the less mobile residual fraction. Largest percentages of metals extracted in the exchangeable fraction corresponded to those soil–metal systems with smaller K_D values, e.g. Cd, Ni and Pb in SL1 and Cd and Ni in SL2. In neutral and alkaline soils (SL2, pH=7.1, and SL3, pH=8.6) Pb was predominantly extracted from the inorganic fractions and this corresponded to higher K_D values for Pb in these soils. The predominance of metals associated with the exchangeable fraction together with low K_D values indicates higher mobility of metals retained in the acidic soil (SL1, pH=5.2) compared with the others.     

青岛城区土壤重金属环境地球化学研究

为研究青岛城区土壤的环境地球化学特征,对青岛市南区、市北区、四方区、李沧区、崂山区5区进行了广泛的土壤地质调查。在每1km2一个样品的取样密度下取得表层土样(0～10cm深度)319个,经前期处理后,利用多种仪器如X射线荧光光谱(XRF)、等离子体发射光谱(ICP-OES)和等离子体质谱(ICP-MS)等分析测得所有样品的72种元素的含量,本文探讨了重金属元素Cd、Cr、Cu、Ni、Pb和Zn及类金属元素As的含量分布。结果表明,人类活动导致表层土壤中元素Cd、Cu、Pb和Zn含量的增加,而元素As、Cr和Ni主要是地质起源,但也会受到人类活动的影响。其中Zn的含量值变化较大,Zn元素含量值增高的地区是工业、交通密集处等人类活动频繁的地区。     

包头市典型工业区表层土壤中重金属污染状况及其潜在生态风险研究

为了解包头市典型工业企业对其所在地土壤中重金属含量的影响及污染现状,利用相关性系数对其表层土壤中7种重金属(Cu、Zn、Pb、Cr、Cd、Mn、Ni)来源进行研究,并采用内梅罗综合污染指数法和潜在生态危害指数对其污染状况进行评价。结果表明,7种重金属含量平均值均高于内蒙古土壤背景值,其中Cd、Mn、Ni超标率已达100%,而Cu、Pb、Zn的超标率分别为97%、93%和93%,只有Cr超标率较低(53%),污染程度依次为CdPbCuNiZnMnCr,其中Pb和Cd为重度污染,Cu、Zn、Ni为中度污染,Cr、Mn为轻度污染;Cu、Zn、Cr、Mn、Ni可能同时来自工业生产和交通运输两个源,而Pb和Cd除上述来源外,燃煤烟气的排放有较大贡献。潜在生态危害依次为CdPbCuNiCrZnMn,其中Cd的潜在生态风险最大,应予以高度重视,其他金属的风险均为轻微。     

Relationships between heavy metals and iron oxides,fulvic acids,particle size fractions in urban roadside soils

Urban roadside soils are the “recipients” of large amounts of heavy metals from a variety of sources including vehicle emissions, coal burning waste and other activities. The behavior of heavy metals in urban roadside soils depends on the occurrence as well as the total amount. Accordingly, knowledge of the interactions between heavy metals and other constituents in the soil is required to judge their environmental impact. In this study, correlations of heavy metal concentrations (Pb, Zn, Cu, Ag, Se, Ni, Cr and Ba) to iron extracted using dithionite–citrate–bicarbonate (DCB) buffer (Fe_DCB), fulvic acids and particle size fractions were examined from the Xuzhou urban roadside soils. Heavy metals except for Cr and fulvic acids had a positive significant correlation with Fe_DCB, indicating these metals and fulvic acids are principally associated with the surfaces of iron oxides of the soils. Significant positive correlations were also found between the contents of fulvic acids and heavy metals, showing these heavy metals (especially for Cu, Ni and Cr) form stable complexes with fulvic acids. Such finding is of importance with regard to the increased mobilization of heavy metals, e.g., into freshwater ecosystems. Ag, Se and Cr are independent of particle size fractions because of their low concentrations of Ag and Se in the studied soils. Pb, Zn, Cu, Ba and Ag are mainly enriched in the finer soil particles (especially <16 μm).     

三峡库区澎溪河消落带土壤中重金属形态分布与迁移特征研究

消落带是水域与陆地的过渡地带,对水环境有着至关重要的影响。本文以三峡库区消落带面积最大的澎溪河流域作为研究区域,采集消落带土壤及其沿岸土壤样品,分析重金属形态分布特征,并使用地质累积指数法和风险评价准则(RAC)对重金属污染程度及生态风险进行评价。研究表明,消落带土壤中Pb、Cu、Cr、Cd、Zn和Ni平均含量分别为68.70、36.96、55.10、0.68、108.26、31.68 mg/kg,污染程度依次为CdPbZnCuNiCr,以Cd和Pb污染较为突出,普遍高于长江干流土壤,远高于重庆地区土壤。Cd的RAC值为20.62%,呈中等环境风险;其形态稳定性最差,以可还原态和酸提取态为主。Pb、Cu、Cr、Zn、Ni的RAC值为5.45%~10.0%,环境风险较低;且均以残渣态为主,占总量的54.69%~83.05%。以消落带沿岸土壤为对照,消落带形成后土壤中各重金属总量均有不同程度升高,且不同重金属在其增量部分的形态存在差异,Cr和Ni的增量部分以残渣态为主,Cd、Pb、Zn的增量以非残渣态为主。研究发现,由于受到水域与陆地污染源的双重影响,澎溪河流域重金属具有由沿岸向消落带沉积富集的趋势。     

Characteristics of distribution and chemical speciation of heavy metals in environmental mediums around Jinchang mining city,Northwest China

Heavy metal contamination was the main environmental problem around the Jinchang Ni–Cu mine area of Gansu, Northwest China. The concentration of heavy metals (Cr, Cu, Ni, Pb, and Zn) in various environmental mediums around the Jinchang Ni–Cu mine area were analyzed using atomic absorption spectrometry (AAS). The different chemical speciation of heavy metals was extracted using BCR (European Community Bureau of Reference) sequential extraction procedure, and the concentration of chemical speciation of each heavy metal was measured by inductively coupled plasma-atomic emission spectrometry. The results showed that Cu and Ni were the most important heavy metal pollutants in various mediums including cultivated soils, dust on slagheap surfaces, tailings, and sediments in waste water drains. In the tailings and sediments, the concentrations of Ni were obviously higher than those of Cu, whereas, in the soil and dust, the concentrations of Cu were higher than those of Ni. Analysis of chemical speciation indicated that Cr and Zn were mainly in residual fraction; Cu was mainly in oxidizable fraction; Ni was mainly in reducible fraction and acid soluble fraction; and Pb was mainly in reducible fraction and residual fraction. The extent of contamination of various environmental mediums was different because the heavy metals were derived from different sources. Furthermore, the mobility of various heavy metals was different because of the different distribution of chemical speciation.     

Metal contamination of soils at Scott Base,Antarctica

Soil samples taken from excavated pits on traverses across New Zealand’s Scott Base, Antarctica, were leached with water and 0.01 M HNO₃ and the leachates analysed for Ag, Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The soils had high conductivity and pH values generally increasing with depth and in the range 8.3–10.1. The water leachate generally contained most of the extractable metals except Mn and Cd, and As. Linear relationships were observed between some metals leached into alkaline solution and the Fe in those solutions. The ratios to Fe were comparable to those of the host basanite, and this observation is interpreted as showing that these metals are incorporated in fine mineral particulates derived directly from the rock mass. Outliers in leachable metal concentrations in the soils indicated appreciable contamination of the soil from anthropogenic sources with Ag, Cd, Cu, Pb and Zn as well as As. In some locations high concentrations of Ag and Cd correspond to specific sources and drainage channels. High concentrations of Pb were widely spread and in the top soil layers whereas the elevated concentrations of Zn were distributed throughout the soil profiles indicating atmospheric sources and different mobilities within the soils. Transport within the soils is evident for some metals, as is lateral movement over and through the soils.     

Background levels and baseline values of available heavy metals in Mediterranean greenhouse soils (Spain)

This study determines extractable levels of Cd, Cu, Pb, Zn, Ni and Co in western Almería (Spain) greenhouse surface soil horizons using EDTA solution, which is identified as the fraction available for organisms and plants. It also establishes background levels, geochemical baseline concentration and reference values (RV), and investigates the possible relationships between soil properties and elemental concentrations. The results show that the soil concentration of these extractable heavy metals was high as those reported by other authors for Spanish agricultural soils. The available RV concentrations obtained (mg kg⁻¹) were: Cd 0.17, Cu 1.6, Pb 13.8, Zn 5.0 Ni 1.7 and Co 2.9. Using the upper baseline criterion, 95% of greenhouse soils present a relatively higher content of extractable heavy metals given their Cd and Cu concentration. Significant correlations between total and EDTA-extractable metal levels were found for Zn, Pb, Cu, Cd and Ni. Soil properties also related to heavy metals content, suggesting that Cd, Cu, Pb and Zn are of similar origin and relate to anthropic activities, and implies the same interactions and/or relationships among these metals.