江西省旱地土壤有效硅含量的分布特征及其影响因素

了解江西旱地土壤有效硅含量分布规律及影响因素,可为今后江西省旱地土壤采取合理的硅肥施用措施提供理论依据。本研究采用柠檬酸浸提—硅钼蓝比色法测定了江西省旱地耕层185个土样的有效硅含量,结果表明:(1)江西旱地土壤有效硅含量范围在12.7～192.0 mg·kg~(-1),空间分布存在较大差异,整体表现为北高南低,西高东低,赣东北最低的分布特征。(2)赣东北、赣北、赣西土壤中有效硅含量随着土壤pH值升高而显著(P0.05)增加;赣南旱地土壤有效硅含量随碱解氮、有效磷的升高而显著(P0.05)降低。(3)江西省除赣东北土壤有效硅平均含量稻田高于旱地,其他4个区旱地土壤有效硅平均含量均高于稻田。且旱地土壤有效硅含量主要集中在25～115 mg·kg~(-1),而稻田土壤有效硅含量主要集中在25～70 mg·kg~(-1),旱地有效硅含量缺(25～70mg·kg~(-1))与极缺(25 mg·kg~(-1))的土壤占比分别比稻田低7.09%和6.03%。但江西省旱地土壤有效硅含量缺和极缺的也占57.3%,超过一半,急需通过合理施肥提高其含量,保证作物的产量和品质。     

典型岩溶流域不同土地利用类型土壤腐植酸与钙的关系

为了阐明岩溶地区不同土地利用类型中土壤腐植酸的分布特征及其与钙的关系,以滇东南典型岩溶流域普者黑流域为研究对象,分析流域内裸地、林地、旱地、水田和湿地5种土地利用类型中土壤表层(0～10 cm)、亚表层(10～20 cm)的水溶性有机质(WSOM)、胡敏酸(HA)、富里酸(FA)的分布情况,并进一步探究土壤中腐植酸的结构特征及其含量与钙的关系。结果表明:研究区5种土地利用类型土壤中WSOM、HA和FA含量的空间变幅均较大(P0.05),且表层亚表层(P0.05),腐植酸含量(WSOM、HA、FA三者含量之和)的大小依次为旱地(13 289.97 mg·kg~(-1))湿地(10 007.02 mg·kg~(-1))林地(9 136.76 mg·kg~(-1))水田(8 708.724 mg·kg~(-1))裸地(3 395.13 mg·kg~(-1));5种土地利用类型土壤PQ值(HA在腐植酸中的比例)以及HA/FA(可以在一定程度上反映土壤有机质的稳定性)的空间变幅较大且变化规律相似,大小排序均为水田湿地林地旱地裸地(P0.05);红外图谱分析表明5种土地利用类型土壤的腐植酸具有类似的结构组成和官能团信息,除含有一定量的芳香结构外,还含有大量的羟基、氨基、酚羟基、醇羟基以及脂肪链结构;冗余分析表明土壤全钙及各形态钙在很大程度上影响腐植酸的种类及含量。研究表明,普者黑岩溶流域内5种土地利用类型土壤腐植酸含量空间变幅较大,结构相似且特征明显,与土壤钙的关系密切,同时普者黑流域内5种土地利用类型土壤的腐殖化程度较高,腐植酸品质较好。     

桂东南地区兴业县富Se土壤地球化学特征及来源浅析

对广西兴业县1/5万土地质量地球化学评价表层土壤样的硒含量进行分析。结果表明,调查区土壤硒量变幅为0.08~12.59 mg·kg~(-1),平均含量为0.59 mg·kg~(-1),高于全国土壤平均硒含量,富硒土壤资源丰富。成土母质以泥盆系、石炭系和二叠系形成的土壤硒含量相对较高,土壤类型中砖红壤性红壤和石灰岩土硒含量相对较高,土地利用类型中园地、林地及草地等土壤硒含量相对较高,而农耕地中水田及旱地土壤硒含量则相对较低。土壤富硒主要来源于原富硒成土母质,其含量分布特征主要受自然地质背景的影响。     

谷壳生物炭与石灰石组配对土壤中Cd有效性的影响

通过水稻盆栽实验,研究了不同添加量的组配改良剂谷壳生物炭和石灰石(TS)对Cd污染土壤的修复效果及水稻对Cd吸收累积的影响。结果表明:(1)添加TS(2~4 g kg~(-1))能显著提高土壤pH值,与对照相比,Cd含量为0.5 mg kg~(-1)和5.0 mg kg~(-1)土壤pH值分别增加了0.69~1.38和0.70~1.12个单位;(2)TS能显著降低土壤中Cd的生物有效性,在Cd含量为0.5 mg kg~(-1)和5.0 mg kg~(-1)土壤中,添加量为2~4 g kg~(-1)时,能使Cd的Ca Cl2提取态含量分别降低13.3%~86.7%和12.2%~73.6%,使Cd的TCLP提取态含量分别降低52.9%~76.5%和37.1%~76.8%;(3)添加TS(2~4 g kg~(-1))能显著降低水稻根系、秸秆、糙米对Cd的吸收累积,在2种不同Cd含量的土壤中(0.5 mg kg~(-1)和5.0 mg kg~(-1)),使糙米Cd含量分别降低了40.8%~60.0%和49.9%~86.6%,糙米Cd含量低于国家食品卫生标准0.2 mg kg~(-1)的限制。     

闽西南崩岗土壤重金属含量、分布、来源及生态风险

选取福建省长汀县黄泥坑崩岗群内2处典型崩岗及附近一无崩岗山坡(对照区),采样并测定了63份0~20 cm土壤样品Cu、Zn、Ni、Pb、Cr、As、Cd含量,运用相关分析与主成分分析进行重金属来源辨识,并应用Hankanson潜在生态风险指数法,以福建省背景值和国家二级标准作为参比,对研究区重金属进行潜在生态风险评价。结果表明:研究区土壤重金属含量从高到低的顺序依次为Zn(105.56 mg·kg~(-1))Pb(67.21 mg·kg~(-1))As(61.47 mg·kg~(-1))Cu(22.33 mg·kg~(-1))Cr(17.12 mg·kg~(-1))Ni(5.24 mg·kg~(-1))Cd(0.80 mg·kg~(-1)),Pb、Cd含量表现为崩岗区对照区,Cu、Zn、Ni、Cr、As、Cd含量与之相反。1号崩岗Zn、Pb、As和Cd平均值分别是福建省背景值的1.12倍、2.82倍、8.68倍和13.33倍,2号崩岗这4种元素平均值分别是背景值的1.11倍、1.36倍、11.22倍和16.67倍,对照区该4种元素平均值分别是背景值的1.58倍、1.60倍、5.14倍和14.44倍;与国家土壤环境质量二级标准比较得出,崩岗区和对照区As平均值分别超标1.92倍和2.70倍,Cd平均值分别超标2.31倍和2.60倍。从集水坡面到沟道末端,崩岗区Pb、Zn、Cd含量呈增加趋势,Cu、Cr含量基本维持稳定,Ni含量有所降低;从坡面上部到下部,对照区Cu、Zn、Ni、Cr、Cd含量呈增加趋势,Pb含量略有降低;As含量在研究区的分布无明显变化。Cu、Ni、Cr主要来源为成土母质,Zn主要来源于禽畜养殖,Cd、As的主要来源包基岩风化稀土开采,Pb主要来源于基岩矿化、煤炭燃烧及汽车尾气排放等复合污染源。以福建省背景值为参比时,Cd潜在生态风险系数达到"极强风险",As为"较强风险",其余均为"轻微风险";以国家二级标准为参比时,Cd属"较强风险",其余均为"轻微风险"。潜在生态风险指数(Ri)表现为2号崩岗对照区1号崩岗。研究区Cd、As污染已较为严重,应采取相应的安全防范措施。     

西北半干旱地区玉米土壤养分丰缺指标研究

对会宁县全膜双垄沟播玉米2007~2010年开展的"3414"田间肥效试验结果进行统计分析,研究了土壤有效养分含量与玉米相对产量之间的相关性,初步建立半干旱地区全膜双垄沟播玉米的土壤养分丰缺指标。结果表明,会宁县土壤碱解氮含量分3个等级,分别为低(43mg·kg~(-1))、较低(43~73mg·kg~(-1))和中(73~125mg·kg~(-1));土壤有效磷含量分5个等级,分别为低(7mg·kg~(-1))、较低(7~15mg·kg~(-1))、中(15~28mg·kg~(-1))、较高(28~35mg·kg~(-1))和高(35mg·kg~(-1));土壤速效钾含量分4个等级,分别为较低(119~172mg·kg~(-1))、中(172~250mg·kg~(-1))、较高(250~283mg·kg~(-1))、高(283mg·kg~(-1))。利用肥料效应函数,结合目标产量计算出不同肥力水平区间的推荐施肥量,每公顷半干旱区全膜双垄沟播玉米随地力等级从低到高以施N 266.1~185.1kg、P_2O_5132.2~95.1kg、K_2O 70~47.7kg,氮:磷:钾=1:0.62~0.43:0.38~0.25为宜。     

黑龙江省土壤硒分布及其影响因素研究

黑龙江省处于全国缺硒带的始端,为研究黑龙江省土壤全硒(Se)的含量、分布及其与土壤性质的关系,在全省采集400余个农业土壤0~20 cm耕层样品及主要类型土壤剖面样品(共21个剖面各发生层次土样71个),分析了土壤全硒含量、分布规律及其影响因素。结果表明,黑龙江省土壤全硒含量变幅为0.008~0.660 mg kg~(-1),平均值为0.147 mg kg~(-1),总体上处于缺硒及潜在缺硒土壤范畴,几乎不存在高硒土壤与硒毒土壤。不同类型土壤中以盐碱土含硒量最低(0.097 mg kg~(-1)),而泥炭土最高(0.273 mg kg~(-1));硒在土壤剖面中主要呈现表聚型分布,也有少数呈现双峰型和心土聚集型分布;不同区域以大兴安岭地区为最低(0.115 mg kg~(-1)),小兴安岭山地最高(0.198 mg kg~(-1));不同行政市以大兴安岭地区最低(0.115 mg kg~(-1)),黑河市为最高(0.228 mg kg~(-1))。回归分析表明:土壤全硒含量与土壤有机碳(SOC)、黏粒含量具有极显著正相关关系,与pH呈极显著负相关。研究区表土层土壤SOC、黏粒含量与pH是影响土壤硒含量的主要因素,此外土壤母质也是影响硒分布的重要因素;而土壤SOC含量对硒在土壤剖面中的分布与富集起到了至关重要的作用。     

莎草诱导土壤有机碳的激发效应

为了探索添加莎草后土壤有机碳的激发效应发生机制,采用室内控制试验,向培育土壤内添加莎草碎片、增施氮磷元素,测定土壤有机碳(SOC)含量、微生物量、土壤δ_(13)C值,计算土壤中"新碳"(源于莎草的)和"旧碳"(土壤原有的)的含量。结果表明,75 d后,对照组SOC降低了11 mg·kg~(-1),氮磷营养组SOC降低了10 mg·kg~(-1),莎草组SOC含量先升高而后下降(最终降低了44 mg·kg~(-1)),莎草+氮磷营养组SOC含量先升高而后下降(最终增加了75 mg·kg~(-1))。土壤δ_(13)C值的变化说明土壤添加莎草后,"旧碳"分解速率加快,诱导了激发效应的发生。添加莎草组中,77.8%的莎草被微生物呼吸作用消耗掉,22.2%转化成"新碳"固定到土壤中。除去激发效应消耗的土壤碳(144 mg·kg~(-1)),土壤总有机碳含量降低了30 mg·kg~(-1);莎草+氮磷处理中,64.0%的莎草被呼吸作用消耗掉,36.0%被固定于土壤中,除去激发效应消耗的94 mg·kg~(-1),总土壤有机碳增加了68 mg·kg~(-1)。莎草处理中,土壤激发效应损失的碳量占莎草分解碳量的37.0%,植物+氮磷处理仅占29.3%,土壤激发效应损失的"旧碳"量远低于莎草呼吸作用损失的碳量。本研究结果为进一步探究土壤添加莎草后激发效应机理提供了参考依据。     

江西省葛种植区中重金属镉调查及其富集特征

为探明葛种植区域土壤和植株中重金属镉含量,对江西省18个葛种植区进行野外调查和室内分析,揭示葛对镉的富集特征及转运规律,为研究葛安全质量控制技术提供理论依据。结果表明:调查区域土壤有效态镉和全镉含量分别为0.002～0.21 mg·kg~(-1)和0.05～0.25 mg·kg~(-1),葛根、葛头、主藤、侧枝和叶片中镉含量分别为0.002～0.28 mg·kg~(-1)、0.14～1.38 mg·kg~(-1)、0.07～1.83 mg·kg~(-1)、0.04～1.80 mg·kg~(-1)和0.05～1.91 mg·kg~(-1);葛根、葛头、主藤、侧枝和叶片/土壤富集系数分别为:0.97、5.30、5.84、4.14和2.05,葛头、主藤、侧枝和叶片/葛根转运系数分别为11.64、8.54、6.16和3.56;不同部位镉含量表现为主藤(0.71 mg·kg~(-1))葛头(0.58 mg·kg~(-1))侧枝(0.51 mg·kg~(-1))叶片(0.28 mg·kg~(-1))葛根(0.11 mg·kg~(-1)),且主藤镉含量显著高于叶片和葛根(P 0.05);相关分析表明,土壤有效态镉和全镉与主藤、侧枝和叶片呈显著正相关,葛根与葛头、主藤和侧枝呈显著正相关。参考土壤镉含量、葛中镉含量、转运系数和富集特征等,并结合聚类分析表明江西省不同葛种植区中镉含量以渝水、兴国、德兴等地区较高,而永丰、南城、鄱阳、上高等地区较低;葛对重金属镉具有较强富集作用,种植过程中要选择土壤环境质量高的区域,避免高风险地区种植。     

曲靖红壤烟区有效镁、速效钾交互作用对烤烟钾、镁、钙吸收及品质的影响

连续两年采用田间实地调查及室内化验分析的方法,分析了云南曲靖不同县(市)烟区土壤有效镁、速效钾含量状况及其交互作用对烤烟钾、钙、镁含量、化学成分和评吸指标的影响,结果表明:曲靖中海拔红壤烟区土壤有效镁平均含量314.10 mg·kg~(-1),变幅32.64~1 402.00 mg·kg~(-1),会泽烟区有效镁含量高达711.25mg·kg~(-1);速效钾平均含量197.95 mg·kg~(-1),变幅21.63~718.92 mg·kg~(-1),除陆良县外,其他各县(市)土壤速效钾含量均处于中等至高等含量范围。烤烟镁含量随土壤有效镁含量的升高而显著增加,烤烟钾含量随着土壤速效钾含量的升高先降低后显著增加,烤烟钙含量随两者变化不显著;交互作用对烤烟钾、镁、钙含量及K/(Mg+Ca)有显著影响。土壤有效镁、速效钾交互作用对烤烟品质影响较大,在土壤有效镁含量处于中、低水平(100 mg·kg~(-1)),土壤速效钾含量处于适宜及以上水平(150 mg·kg~(-1))时,烟叶品质表现最好。     

Selenium in Water,Sediment, Plants,Invertebrates, and Fish in the Blackfoot River Drainage

Nine stream sites in the Blackfoot River watershed in southeastern Idaho were sampled in September 2000 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish. Selenium was measured in these aquatic ecosystem components, and a hazard assessment was performed on the data. Water quality characteristics such as pH, hardness, and specific conductance were relatively uniform among the nine sites examined. Selenium was elevated in water, sediment, aquatic plants, aquatic invertebrates, and fish from several sites suggesting deposition in sediments and food web cycling through plants and invertebrates. Selenium was elevated to concentrations of concern in water at eight sites (>5 g/L), sediment at three sites (>2 g/g), aquatic plants at four sites (>4 g/g), aquatic invertebrates at five sites (>3 g/g), and fish at seven sites (>4 g/g in whole body). The hazard assessment of selenium in the aquatic environment suggested low hazard at Sheep Creek, moderate hazard at Trail Creek, upper Slug Creek, lower Slug Creek, and lower Blackfoot River, and high hazard at Angus Creek, upper East Mill Creek, lower East Mill Creek, and Dry Valley Creek. The results of this study are consistent with results of a previous investigation and indicate that selenium concentrations from the phosphate mining area of southeastern Idaho were sufficiently elevated in several ecosystem components to cause adverse effects to aquatic resources in the Blackfoot River watershed.     

Caimans,Capybaras, otters,manatees, and man in amazonia

Amazonia, the world's largest tropical rain forest, is often assumed to be a virtually untouched wilderness. The region is often referred to as a demographic void; there is on average only about one person per sq. km. Yet in response to international market forces, the hand of man has penetrated deep into the imposing forests. Since colonial times, wildlife, particularly along rivers, has been exploited on a large-scale basis for commercial purposes. This paper focuses on the effects of the trade on some aquatic animals.     

Hg, Cu, Pb, Cd, and Zn Accumulation in Macrophytes Growing in Tropical Wetlands

The concentrations of Hg, Cu, Pb, Cd, and Zn accumulated by regional macrophytes were investigated in three tropical wetlands in Colombia. The studied wetlands presented different degrees of metal contamination. Cu and Zn presented the highest concentrations in sediment. Metal accumulation by plants differed among species, sites, and tissues. Metals accumulated in macrophytes were mostly accumulated in root tissues, suggesting an exclusion strategy for metal tolerance. An exception was Hg, which was accumulated mainly in leaves. The ranges of mean metal concentrations were 0.035?C0.953 mg g^?1 Hg, 6.5?C250.3 mg g^?1 Cu, 0.059?C0.245 mg g^?1 Pb, 0.004?C0.066 mg g^?1 Cd, and 31.8?363.1 mg g^?1 Zn in roots and 0.033?C0.888 mg g^?1 Hg, 2.2?C70.7 mg g^?1 Cu, 0.005?C0.086 mg g^?1 Pb, 0.001?C0.03 mg g^?1 Cd, and 12.6?C140.4 mg g^?1 Zn in leaves. The scarce correlations registered between metal concentration in sediment and plant tissues indicate that metal concentrations in plants depend on several factors rather than on sediment concentration only. However, when Cu and Zn sediment concentrations increased, these metal concentrations in tissues also increased in Eichhornia crassipes, Ludwigia helminthorriza, and Polygonum punctatum. These species could be proposed as Cu and Zn phytoremediators. Even though macrophytes are important metal accumulators in wetlands, sediment is the main metal compartment due to the fact that its total mass is greater than the corresponding plant biomass in a given area.     

Variation of N,P, K,Ca, Mg,Mn, Zn,and al in slash pine foliage

Abstract

The seasonal patterns of foliage nutrient concentrations and contents were monitored for two growing seasons in an 11‐year—old Pinus el1iottii stand. In the first growing season after needle initiation, N, P, K, Mg, and Zn concentrations decreased, but this was followed by an increase in the fall and winter months. Another drop in concentration of all elements, except P, occurred in the second growing season. Decreases in total contents indicated that this drop was a result of translocation to other tissues. In contrast to the mobile elements, the concentration and fascicle contents of Ca, Mn, and Al increased with aging of the needles.

Between‐tree variability was least for N, P, and Zn and the N, K, Mg, Mn, and Zn in the current foliage had consistently lower variation than that in the 1‐year‐old foliage. Between‐tree variation for K was lower in the winter than the spring.

For pine foliage, recommended sampling period for N, P, Mg, and Zn is mid to late summer and for the other elements it is late fall to late winter.

There are several sources of variation that influence the level of nutrients in tree foliage. The most important of these, apart from the tree nutrient status, are seasonal fluctuations, variation between trees, and age of needles . Smaller sources of variation are associated with position of the needles within the crown, diurnal changes, year to year variation, and analytical errors^1,2. These variables must be studied in order to develop suitable sampling techniques and in Pinus this has been undertaken for P. banksiana ¹, P. taeda ³, P. strobus ⁴, P. resinosa ⁴, P. sylvestris ⁵, and P. radiata ^6,7. However, foliage sampling has not been studied in detail for slash pine (Pinus elliottii Englem var. elliottii) and earlier studies with other pines have been largely confined to temperate or cool climates.

This study reports the variation in elemental concentrations with season, age of foliage, and between slash pine trees growing in a subtropical climate in Florida.     

Extractors for barium,cadmium, copper,nickel, and zinc in tropical soils

ABSTRACT

The accumulation of potentially toxic elements (PTEs) in the soil can pose risks to human health, and precise risk assessment dealing with the production and consumption of plants is required. The 0.43 M of nitric acid (HNO?) solution was suggested by the International Organization for Standardization for reactive fraction of PTEs in the soil. The efficiency of some extractors was evaluated in tropical soils. Contents of barium (Ba), cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) were extracted in accordance with the methods of Environmental Protection Agency (EPA) 3051A, Aqua Regia, Diethylenetriaminepentaacetic acid (DTPA), Mehlich-1, Mehlich-3, 0.43 M HNO? and 0.01 M of calcium chloride (CaCl?), and these contents correlated with the contents of PTEs in roots, shoots, and fruits of vegetables. Mehlich-3 had the highest correlation with Ni and Zn contents extracted by the plants. Contents extracted with 0.43 M HNO? had high correlation with the amounts extracted by DTPA and Mehlich-3, as well as with the amounts of PTEs accumulated by plants.     

Distribution of Zinc,Manganese, Copper,Cobalt, and Nickel in Andosols Profiles

The distribution of zinc, manganese, copper, cobalt, and nickel in Andosols was investigated. Sixty nine soil samples were collected from different horizons of an Andosols profile in Miyakonojo Basin in south Kyushu, Japan, The total contents of heavy metals were determined by digestion and four extraction solutions, 1 M NH₄Ac (ammonium acetate) pH 4.5, 0.1 M HCl, 0.01 M EDTA (ethylenediaminetetraacetic acid) pH 6.5, and 0.005 M DTPA (diethylenetri-aminepentaacetic acid) pH 7.3 were used to determine the contents of available Zn, Mn, Cu, Co, and Ni in Andosols in relation to the organic carbon content. The results of the extraction analysis showed that by the use of 0.1 M H Cl high value of extracted heavy metals in the upper layers of the humus horizons were obtained while EDTA extraction yielded a large amount of the above mentioned metals in the high humus horizons. The extractable heavy metals contents were high and these metals closely related to the organic carbon content mostly in the humus horizons in the profile. Where, biocycling process may play an important role in the concentration of heavy metals. Based on the study, it was found that the total content of Zn increased towards the C horizons or pumice layers in the soil profile. Such a trend was also found in the case of the Mn content. While the Cu content in the humus horizons was much higher in the upper part of each humus horizon. According to this study the distribution of heavy metals, Cu (organic matter complexes) in the Andosols profile was more stable than that of Zn (organic matter complexes) in soils. It was shown that Zn in the surface humus horizon was enriched but that some amount was leached under buried conditions. The same phenomenon was also observed in the distribution of Mn in the profile. The movement of Co and Ni in the soil profile was limited, as evidenced by the sharp reduction in the concentrations of these two metals in buried soils.

Hence, it is concluded that the distribution of Zn, Mn, Cu, Co, and Ni was considerably higher in the humus horizons of the Andosols profiles.     

Arsenic Concentrations in Water,Soil, Milk and Forage in Comarca Lagunera,Mexico

Arsenic levels were determined in seventy three samples of well water, and in fifty samples of soil, forage and cow's milk collected at the most important dairy farms of the Comarca Lagunera located in Coahuila and Durango, Mexico, region naturally rich in As. The total inorganic arsenic concentration in well water ranged from 7 to 740 μg L-1 and about ninety percent of the total arsenic was found as As(V). The agricultural soil texture of the sampled area was sandy clay loam type with total arsenic levels up to 30 μg g-1, however, the extractable arsenic was not higher than 12% of the total and it was higher in the 0–30 cm depth horizon. In alfalfa, the most important crop, the total aresenic ranged from 0.24 to 3.16 μg g-1, with 40% of it accumulated at the root level. Significant correlations (p=0.05) were obtained between arsenic (III), (V) and total inorganic arsenic in groundwater with arsenic in soil (0–30 cm depth), and with arsenic in alfalfa (leaves and roots). It was also found a good correlation between extractable arsenic in soil with As concentrations in alfalfa (roots). Arsenic concentrations found in milk ranged from <0.9 to 27.4 ng g-1. The cow's milk biotransfer factor for arsenic was up to 6 × 10-4, applying a pharmacokinetic approach. It was associated with the exposure not only to food but also to water arsenic.     

Estimation of Reference Values for Cadmium,Cobalt, Chromium,Copper, Nickel,Lead, and Zinc in Brazilian Soils

Abstract

The objectives of this study were 1) to recommend reference values (RVs) and tolerance limits (TLs) for representative Brazilian soils and 2) to propose a model to calculate natural contents of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in a soil from the silt, clay, manganese (Mn), iron (Fe), and cation exchange capacity (CEC) values. A set of 256 soil samples was classified by similarity in seven groups, and the concentrations corresponding to the upper quarter of data collected were then calculated. These concentrations are proposed as RVs for Brazilian soils. Additionally, TLs were obtained for each group from the antilog expression (m+2s), where m=mean value and s=standard deviation of data transformed in log₁₀. The classification functions of discriminant analysis proved to be suitable to allocate new samples in the established groups. Thus, it is possible to evaluate soils under anthropic activity and, by comparison with reference values, to be aware of pollution risks in a given area.