Trace Element Content Of Soils Research Articles

Potential accumulation of toxic trace elements in soils during enhanced rock weathering

AbstractTerrestrial enhanced rock weathering (ERW) is a carbon dioxide removal technology that aims at accelerating one of the most powerful negative feedbacks on Earth's climate, the chemical weathering of silicates. To achieve this, ERW proposes to spread ground silicate rock on agricultural soils. According to many models, global application rates of 40 tonnes of ground basaltic rock per hectare and per year would be necessary to sequester a significant amount of CO2, representing up to 24% of the current net annual increase in atmospheric CO2. When assessing the viability of ERW as a global geo‐engineering strategy, a pivotal but overlooked question to address is whether ERW may lead to toxic trace element accumulation in soils at unauthorized and potentially harmful levels. This study evaluates the legal sustainability of ERW with regard to trace element contents in soils. We compare different trace element accumulation scenarios considering a range of rock sources, application rates and national regulatory limits. The results indicate that, at the suggested annual application rate of 40 tonnes per hectare, the first regulatory limits would be exceeded after 6 and 10 years for copper and nickel, respectively. This study argues in favour of close tailoring of ERW deployment to local conditions in order to tap into its climate mitigation potential while preserving long‐term soil uses.Highlights Terrestrial enhanced rock weathering (ERW) is a carbon sequestration technology that consists in applying rock powder to soils. This study evaluates whether rock powder application can lead to trace metals accumulation in soils beyond regulatory limits. ERW can lead to the overrun of some environmental regulatory limits within less than a decade. Specific site and rock selection will be necessary for this method to preserve long‐term soil uses.

Heavy metal contents, mobility and origin in agricultural topsoils of the Galápagos Islands

While the Galápagos Islands have been renowned for their unique flora and fauna since the time of Charles Darwin, the soils of the isolated island chain have been mostly overlooked and little information on their heavy metal contents is available. The aim of this study was therefore to examine the total heavy metal (Cd, Co, Cr, Cu, Ni, Pb, U, Zn) contents of soils from the agricultural areas on islands Isabela, Santa Cruz and San Cristóbal, and identify trends with duration of exposure to weathering processes. Additionally, the mobility of these elements was assessed using ammonium nitrate extraction. In general, levels of Cd, Co, Cr, Cu, Ni and Zn were high compared to other world locations, while Pb levels were low and U levels were similar. Ni, Co, Cr, and to a lesser extent Pb and U tended to accumulate with increasing weathering duration. Soil concentrations of Cd, Zn, Cu, and possibly Pb and U, may have been influenced by use of agrochemicals, particularly on Santa Cruz Island. Mobility of Cd displayed an increasing trend with soil age, while Ni mobility decreased. Many soils had total contents of Cd, Co, Cr, Cu, Ni and Zn above threshold values indicating possible ecological or health risks. Systematic examination of trace element contents in soils from pristine national park areas would further assist in the delineation of background levels and the development of soil quality standards to ensure crop quality, animal and human health on this unique island chain.

Variability in plant trace element uptake across different crops, soil contamination levels and soil properties in the Xinjiang Uygur Autonomous Region of northwest China

This study investigated contamination status of eight trace elements (As, Cd, Cr, Hg, Pb, Cu, Zn and Ni) in farmland soils and crops at 535 sites across the Xinjiang Uygur Autonomous Region, Northwest China. Land use types of the sampling sites included vegetable patch, grain field and orchard. Our experimental results indicated all farmland soils were considered as trace element contamination based on the Nemerow comprehensive pollution index (NCPI > 1). However, 91.97% of the crop samples were uncontaminated according to the Chinese Risk Control Standard. Soils from the vegetable patch showed higher pollution level comparison with that from grain field and orchard. Health risks for both non-carcinogenic and carcinogenic risks were calculated through crop ingestion exposure pathway. Grain samples showed highest health risks, followed by melon and fruit, and vegetables. The health risks of crops were mainly driven by Cr and Cd. Crop consumption may pose risks for children but not adults. The source of trace element contamination in the different farmland soils varied and may be attributed to the different agricultural activities. Plant type had a greater influence on the trace element accumulation in crops compared with soil trace element contents and physicochemical properties.

Assessment of Trace Element Contents in Soils and Water from Cerrado Wetlands, Triângulo Mineiro Region

ABSTRACT In the Brazilian Cerrado biome, there are wetlands locally known as “Veredas”, which are swampy plains between hills and rivers. Since the 1970’s, the Cerrado biome has been gradually converted to livestock, crop, or forestry production. Until now, very few studies were conducted to evaluate the baseline contents of trace elements in Cerrado wetland soils. Due to their position in the landscape (bottom lands), the wetlands are potentially susceptible to contamination by runoff and/or leaching from surrounding areas at [...]

Effect of zinc oxide nanoparticles on the trace element contents of soils

ABSTRACTIn the last few decades, metal oxide nanoparticles have shown impact in various areas, and such an impact causes an increased release in a different environment like soil, water, or air. A limited number of studies on soils showed that the biochemical parameters were affected by the metal oxide nanoparticles. However, the influence of metal oxide nanoparticles on soil elements has not been investigated. For this aim, zinc oxide nanoparticles were applied to two different soils; also, the effect of planting on soil elements was investigated via the cultivation of various plants roots (taproots, fibrous, bulb). Soils were treated with zinc oxide nanoparticles at 0, 1.0 and 20.0 mg during 4 weeks. Then, surface soil samples were collected and digested using an acid digestion procedure. Some biochemically important elements (Ca, Zn, Mg, Fe, Al, Cu, Co, Ni) were determined using a microwave plasma atomic emission spectrometer. The effect of time and dose-dependent zinc oxide nanoparticles on the element contents of different soils was investigated during planting, and the results were statistically evaluated.

Evaluation of the suitability of three Mediterranean shrub species for phytostabilization of pyritic mine soils

A greenhouse pot experiment was conducted to evaluate the potential use of Nerium oleander, Cistus albidus and Pistacia lentiscus for phytostabilization of acidic mine soils. The selected species were grown in mine tailing soil, unamended (TS) and amended with calcium carbonate and pig manure (ATS), and in a reference unpolluted substrate for control (CT); plant growth, root characterization, soil trace element contents, and their accumulation in plants were measured. Results indicated that seed emergence was independent of the substrate characteristics, but seedlings were seriously affected and died in TS, with survival of 5–40% in ATS. Only stem biomass of P. lentiscus and root volume of N. oleander were negatively affected when grown in TS, but without differences between ATS and CT. There were significant negative correlations between soil and plant trace element concentrations and plant biomass and root development, indicating the effect of trace elements on plant growth. The application of amendments reduced the soil exchangeable and extractable fraction concentrations of trace elements in ATS compared with TS, mainly for As, Cd and Pb. The tested species directly contributed to the immobilization of trace elements in the soil. As a general pattern, trace element concentrations in plants grown in the unamended tailing soil were similar to those reported for the amended soil, with levels below toxicity thresholds. Thus, these species fulfill the criteria to be used for phytostabilization purposes, aided by application of amendments to increase plant growth.

The geochemical signature of rare-metal pegmatites in the Central Africa Region: Soils, plants, water and stream sediments in the Gatumba tin–tantalum mining district, Rwanda

We studied trace elements in soils, plants, water and stream sediments in the Gisuma–Kibilira catchment of the Gatumba area of western Rwanda which has a long tradition of artisanal to small-scale tin–tantalum mining from rare-metal pegmatites. The geochemical fingerprint of soil, plant, water (springs and surface water in dry and rainy seasons) and stream sediment samples reveals elevated concentrations of Li, Rb, Cr, and Cs, but low As and U abundances at or below the global average. Trace element contents of soils and most plant materials are below internationally accepted guideline values. All water samples analyzed meet the World Health Organization (WHO) drinking water guidelines, and the stream sediments are below critical values of Dutch environmental standards. These data provide a baseline for environmental impact studies for rare-metal mining projects in the Central Africa Region.

不同覆盖方式对旱地果园水热特征的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同覆盖方式对旱地果园水热特征的影响 DOI: 10.5846/stxb201211051543 作者: 作者单位: 甘肃省农业科学院林果花卉研究所,甘肃省农业科学院林果花卉研究所,静宁县林业局,甘肃省农业科学院林果花卉研究所,甘肃省农业科学院林果花卉研究所,静宁县康源果农协会 作者简介: 通讯作者: 中图分类号: 基金项目: 现代农业产业技术体系建设专项资金资助项目（CARS-29-41）；农业部西北作物抗旱栽培与耕作重点开放实验室和甘肃省旱作区水资源高效利用重点实验室开放基金课题资助项目（HNSJJ-201103） The effects of different mulching way on soil water thermal characteristics in pear orchard in the arid area Author: Affiliation: Institute of Fruit and Floriculture of Gansu Academy of Agricultural Sciences,Institute of Fruit and Floriculture of Gansu Academy of Agricultural Sciences,Jingning county Fruit Industry Bureau,Institute of Fruit and Floriculture of Gansu Academy of Agricultural Sciences,Institute of Fruit and Floriculture of Gansu Academy of Agricultural Sciences,Jingning county KangYuan Growers Association Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用垄膜覆盖（T1）、覆草（T2）和免耕无覆盖（T3）等方法，测定分析陇东旱地果园水热状况，结果表明，0-60 cm土壤温度全年T1最高，萌芽开花期至果实膨大期T2温度最低，新梢停止生长期至落叶期T3温度最低。T1地表和20 cm土壤最高温度出现在6月上旬，40 cm和60 cm出现在8月上旬，表现为浅层（0-40 cm）最高温度出现提前，而T2和T3不同土层最高温度均在8月上旬。0-25 cm不同处理土壤温度表现为晴天最高，雨天最低。除7月至8月土壤温差以T1最大外，其余时期均以T3最大，全年T2温差最小。梨树生长前期（4-6月），T3土壤含水量最小，7月以后，T3最高。梨年生长周期中，T1土壤含水量变化最小，T3最大。不同土层T1土壤容重最小，孔隙度最大，T3土壤容重最大，孔隙度最小；0-120 cm土层T1和T3土壤容重均表现为先升后降，T2为先降后稳定变化的特点。不同处理土壤营养元素含量随时间变化而降低，T3降幅最大。地面覆盖减缓了土壤养分的流失，同时增加了土壤铁、锌、硼等元素含量。 Abstract:By adopting the ridge film mulching (T1),wheatgrass mulching (T2) and zero tillage without cover (T3) method. To determine and analyze the soil temperature and moisture in a year changes in dry land pear orchard in eastern Gansu. The results show that the soil temperature of T1 is highest in 0-60cm soil horizon in a year. During bud sprouting and flowering to the growth stage of the fruit, the soil temperature of T2 is lowest,and T3 is lowest which new shoots stop growing period to leaf fall period.T1 treatment which The highest temperature of the surface and 20cm soil appears in early June, but 40 cm and 60cm appeared in early August. It was concluded that the highest temperature of the shallow layer (0-40 cm) of T1 appears in advance, while the highest temperature of different soil layer of T2 and T3 are in early August. In 0-25cm soil horizon, different treatment soil temperature performance for sunny is highest, lowest rainy day. The soil temperature difference of T1 from July to August is maximum, and T3 is maximum in the remaining time. In a year, the soil temperature difference of T2 is minimum. At growth prophase (4-6 months)of pear tree, the soil moisture content of T3 is minimum. After the July, the soil moisture content of T3 is highest. Annual growth cycle of pear tree, the soil moisture content change of T1 is minimum, and T3 is maximum. The soil bulk density of T1 with different soil horizon is minimum and its soil porosity is maximum. T3 is contrary. In 0-120 cm soil horizon, the soil bulk density of T1 and T3 treatment are performing first rises then falls, but T2 treatment is the first drop then stable change. The soil nutrient element contents of different treatment with the time change is reduced, the range of T3 is biggest. Mulching slow down loss speed of the soil nutrients, and also increase the soil trace element contents of iron, zinc, boron, etc. 参考文献 相似文献 引证文献

Spatio-temporal variation of trace element contents in Rwanda necrosols

In this study, the spatio-temporal variation of selected trace elements in cemetery soils (necrosols) was investigated. Preliminary results revealed that onsite mean concentration for As, Ba, Cr, Cs, Ga, Ni, Rb, Sc, Th, V, Y, and Zr was generally higher than background offsite values. The trace metal contents of the cemetery soils also showed higher accumulation ratio for As, Cr, Ni, and Sc relative to world averages for soils (Clarke values). Similarly, it was observed that the cemetery soils showed significant enrichment with As and Cr in comparison with world averages for agricultural soils. The exchangeable sodium percentage showed that most of the onsite soil samples are sodic, which may have adverse effect on the growth and yield of crops grown in the study area. The study concludes that decomposition of human remains and grave contents play a significant role in elevating the total trace element contents in soils associated with cemeteries. For this reason, there is need for proactive measures to be taken with respect to the choice of raw materials used for the construction of coffins and funeral materials. There is need for local funeral industries particularly in developing countries and the government to begin to consider and adopt such green or environmental friendly burial options to prevent the potential environmental degradation of cemetery areas.

Assessment of sampling and analytical uncertainty of trace element contents in arable field soils

Assessment of trace element contents in soils is required in Germany (and other countries) before sewage sludge application on arable soils. The reliability of measured element contents is affected by measurement uncertainty, which consists of components due to (1) sampling, (2) laboratory repeatability (intra-lab) and (3) reproducibility (between-lab). A complete characterization of average trace element contents in field soils should encompass the uncertainty of all these components. The objectives of this study were to elucidate the magnitude and relative proportions of uncertainty components for the metals As, B, Cd, Co, Cr, Mo, Ni, Pb, Tl and Zn in three arable fields of different field-scale heterogeneity, based on a collaborative trial (CT) (standardized procedure) and two sampling proficiency tests (PT) (individual sampling procedure). To obtain reference values and estimates of field-scale heterogeneity, a detailed reference sampling was conducted. Components of uncertainty (sampling person, sampling repetition, laboratory) were estimated by variance component analysis, whereas reproducibility uncertainty was estimated using results from numerous laboratory proficiency tests. Sampling uncertainty in general increased with field-scale heterogeneity; however, total uncertainty was mostly dominated by (total) laboratory uncertainty. Reproducibility analytical uncertainty was on average by a factor of about 3 higher than repeatability uncertainty. Therefore, analysis within one single laboratory and, for heterogeneous fields, a reduction of sampling uncertainty (for instance by larger numbers of sample increments and/or a denser coverage of the field area) would be most effective to reduce total uncertainty. On the other hand, when only intra-laboratory analytical uncertainty was considered, total sampling uncertainty on average prevailed over analytical uncertainty by a factor of 2. Both sampling and laboratory repeatability uncertainty were highly variable depending not only on the analyte but also on the field and the sampling trial. Comparison of PT with CT sampling suggests that standardization of sampling protocols reduces sampling uncertainty, especially for fields of low heterogeneity.

Trace element distribution and 235U/ 238U ratios in Euphrates waters and in soils and tree barks of Dhi Qar province (southern Iraq)

To assess the quality of the environment in southern Iraq after the Gulf War II, a geochemical survey was carried out. The survey provided data on the chemistry of Euphrates waters, as well as the trace element contents, U and Pb isotopic composition, and PAH levels in soil and tree bark samples. The trace element concentrations and the 235U/ 238U ratio values in the Euphrates waters were within the usual natural range, except for the high contents of Sr due to a widespread presence of gypsum in soils of this area. The trace element contents in soils agreed with the common geochemistry of soils from floodplain sediments. Some exceptions were the high contents of Co, Cr and Ni, which had a natural origin related to ophiolitic outcrops in the upper sector of the Euphrates basin. The high concentrations of S and Sr were linked to the abundance of gypsum in soils. A marked geochemical homogeneity of soil samples was suggested by the similar distribution pattern of rare earth elements, while the 235U/ 238U ratio was also fairly homogeneous and within the natural range. The chemistry of the tree bark samples closely reflected that of the soils, with some notable exceptions. Unlike the soils, some tree bark samples had anomalous values of the 235U/ 238U ratio due to mixing of depleted uranium (DU) with the natural uranium pool. Moreover, the distribution of some trace elements (such as REEs, Th and Zr) and the isotopic composition of Pb in barks clearly differed from those of the nearby soils. The overall results suggested that significant external inputs occurred implying that once formed the DU-enriched particles could travel over long distances. The polycyclic aromatic hydrocarbon concentrations in tree bark samples showed that phenanthrene, fluoranthene and pyrene were the most abundant components, indicating an important role of automotive traffic.

Accumulations of major and trace elements in particle size fractions of soils on eight different parent materials

The major (ME) and trace element (TE) contents of virgin soils are very important in areas with chances to be contaminated from anthropogenic activities. We determined the ME and TE composition of 21 soils developed on dacite, lamproite, andesite, basalt, diabase, mica schist, quartzite and colluvial deposits to elucidate elemental transfer from PGM to soils. We also studied the enrichment of ME and TE in various particle size fractions. In general, the highest content of Si was observed in sand fraction regardless of PGM and is attributed to the dominance of quartz (SiO 2) in this size fraction. Results showed that Pb, Cd, Cu and Zn are associated with Al- and/or Fe-containing minerals such as micas, pyroxenes, and amphiboles and exhibit preferential partitioning into fine particle size fractions in the soils studied. Cobalt, Ni, and Cr are associated with Mg-bearing minerals such as smectites and Ti is related to Na-bearing mineral such as plagioclases (e.g. albite and andesine). Significant correlations between elemental contents in soils and PGM confirm that rock types significantly control ME and TE contents in soils, although some variations are expected due to factors such as resistance of rock to weathering, formation of secondary Fe oxides, elemental fixation and other pedogenic processes. Our data can be used to as benchmark or background information for ME and TE contents to assess any elemental enrichment from anthropogenic activities.

Total elemental composition analysis of soil samples using the PIXE technique

The determination of major and trace element contents in soils was developed by acid digestion method combined with particle-induced X-ray emission spectrometry (PIXE). The digestion of soils was achieved by using nitric acid (HNO3), hydrochloric acid HCl and hydrogen peroxide (H2O2) with repeated additions. A 20μL aliquot from the digested samples was evaporated on the Nuclepore Track-Etch Membrane and irradiated by the 2.5MeV proton beam from the single-end type Van de Graaff accelerator. The accuracy of this methodology was estimated based on series of measurements done for a reference material of soil CRM 023-050. The proposed experimental procedure was shown to have good reproducibility of the experimental results. The corresponding limits of detection (LODs) for Na, Mg, Al, P, S, Cl, K, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Mo and Cd were estimated. Other soil characteristics such as total carbon (TC) and nitrogen (TN) content, pH and electrical conductivity (EC) were also measured.

The Characteristics and Fertility Status of Tin Mine Spoils of the Jos Plateau, Nigeria

A laboratory study was carried out to determine some physico-chemical properties of five categories of tin mine spoil soils of the Jos Plateau. These categories include reclaimed cropped spoil (RCS), reclaimed uncropped spoil (RUS), mining (intermound) depressions (MD), spoil mounds (SM) and surrounding flat land (SFL). Unmined Ropp soil (URS) was included as control. RCS had significantly (P -1 ) and organic carbon (13.7 g kg -1 ) while URS, which had the lowest organic carbon content (3.4 g kg -1 ), although not significantly (P > 0.05) different from SM and MD, had a significantly higher available phosphorus content (18.44 g kg -1 ). RUS had a significantly higher amount of silt (307 g kg-1) followed by RCS (268 g kg -1 ). The large silt content of RUS and RCS is a reflection of the aeolian origin of the parent material of the soil used in the reclamation of the mine spoils. Copper was present in varying quantities in all categories of the mine spoils with the least contents in the reclaimed cropped and reclaimed uncropped soils. This was attributed to the presence of metal ore bodies in the rocks below the soil profile of mine spoils that could have contributed to the trace element contents of soils in its immediate vicinity. Generally, the differences observed in the magnitude of soil physical and chemical properties were as a result of management practices rather than the inherent soil type characteristics. Key words: Jos Plateau, mine spoils, tin, reclamation, soil characteristics, Nigeria Nigerian Journal of Soil Research Vol.5 2004: 44-52

Determination of trace elements in soil and plants in the Orontes basin of Syria by using instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) have been used for the determination of some major, minor and trace elements (As, Cr, Co, Ni, Zn, Sb, Sc, Ce, Ti, Fe, Mn and V) in various plant leaves together with their soil. The accuracy of the measurements have been evaluated by analyzing a number of plant and soil reference materials, precision have been estimated by triplicate analysis of the sample as well as that of the reference material. The obtained accurate and reliable data of some trace elements on microgram level for plants and soil will serve as baseline values and will be helpful to monitor the changes in the trace element content of soil and plant leaves.

Geochemistry and partitioning of trace metals in acid sulphate soils in Sweden and Finland before and after sulphide oxidation

Acid sulphate soils (ASS) are formed on sulphidic sediments along the Baltic coasts of Sweden and Finland. The sulphides in the fine-grained sediments were once formed in an anoxic environment some centimetres below an oxic sediment–water interface. In earlier investigations, high concentrations of many trace elements have been observed in streams draining such areas. We compared the trace element contents in soils formed in sulphidic and non-sulphidic clays. The results show that the total contents of Cd, Ni, Mn, Co and Cu in the sulphidic sediments are not higher than in non-sulphidic clays from adjacent areas. However, the mobilisation of Cd and Ni is higher from acid sulphate soils than from soils formed on sulphide-free clays. To understand the processes causing the mobilisation, we studied the partitioning of trace metals before and after oxidation of sulphidic sediments. Cadmium, Ni, Mn, Co, Zn, and to some extent Cu, were found to be mobilised from acid sulphate soils due to increased weathering caused by the low pH in these soils. Iron and Cr are only mobilised to a limited extent. Copper, Mo and Fe mobilised from weathering are precipitated in oxides that form in the oxidised Bg-horizons. Nickel, Co, Mn, Mo and Cu were shown to be partly bound in pyrite and are mobilised from acid sulphate soils during the pyrite oxidation. However, mobilisation of trace elements from pyrite was not found to be an important quantitative contributor to trace element leaching. Any elements that are mobilised are likely to be transported down through the characteristic cracks, which occur frequently in the oxidised horizons. Evidence of this was found at the groundwater table, where the most easily extractable fraction of mobilisable elements occurred at higher concentrations.

Trace Element Concentrations of Three Soils in Central Appalachia

Trace Element Concentrations of Three Soils in Central Appalachia

Characterization of trace element distributions in soils

A method was developed for the analysis of the trace element content of soils using X-ray fluorescence spectrometry (XRFS). The method was successfully applied to the determination of the distributions of Cr, Ni, Zn, Rb, Sr, Y, Zr, Pb, Ba, and Mn in several types of soils. Soils were fractionated into eight particle size fractions using sieves with meshes between 5 μm and 800 μm. We found that the studied elements were mostly concentrated in the smallest size fraction. Mineralogical phase analysis was carried out using X-ray powder diffraction (XRD), and the elemental compositions of solid soil samples were analyzed using XRFS method. Despite their variability, grain size distributions of different soils share some general features. Commonly the grains in the <5 and 20–45-μm fractions were most abundant. The trace elements occur in three types of associations: (a) adsorbed onto mineral surfaces; (b) in crystallographic positions within minerals (e.g. Ti in rutile, Zr in zircon); and (c) bound to clay minerals. Our results show that the grain size distribution of a given mineral is related to its origin and can be used as a source of information when soil-forming processes are studied.

Factor Score Mapping of Soil Trace Element Contents for the Shenzhen Area

The abundances of copper, lead, zinc, nickel, chromium, cobalt, mercury, vanadium, and manganese in eighty three surface soil samples collected from Shenzhen area were determined. The correlation among element contents and the factors affecting the contents were studied using principle component analysis. The factor scores of the first two components were analyzed as regionalized variables using variogram analysis and Kriging. The interpolated factor scores were then mapped to show the common features in spatial distribution of a set of elements with similar geochemical behavior. It was demonstrated that the spatial distribution patterns of parent material in the area are the primary factor governing the spatial variation of the elements.

Baseline concentration levels of trace elements as a function of clay and organic carbon contents in soils in Flanders (Belgium)

Baseline concentration levels of trace elements in the soils of Flanders (Belgium) were assessed as a function of clay and organic carbon contents. Outliers in the data were identified and rejected according to statistical criteria. Median trace element concentrations in mg/kg dry wt. were As 7, Cd 0.18, Co 0.05, Cr 24.6, Cu 9.6, Hg 0.17, Ni 3.5, Pb 21.5, Zn 34.5. Clay and organic carbon contents were found to be significant in predicting soil trace element contents in unpolluted soils. The coefficients of determination ranged from 0.07 (Hg) to 0.69 (Ni). Based on confidence intervals of the observations, trace element concentrations that have a known probability of being exceeded can be assessed as a function of clay and organic carbon content and used as soil quality reference values.