Impact of municipal compost on soil phosphorus availability and mineral phosphorus fractions in some calcareous soils

The phosphorus (P) resources worldwide are limited, and the prices of commercial P fertilizer continue to increase. Therefore, the use of P containing wastes is important for P recycling in agriculture. The P fractionation methods have been widely applied to characterize the effect of land use practice on soil P dynamics. Information about effect of organic manures on available P and inorganic P (P_i) fractions in calcareous soils of Chaharmahal va Bakhtiari province is limited. The objectives of this research were to study the effect of municipal compost (MC) on available P and P_i forms in five calcareous soils. Municipal compost was applied at the rates of 0, 0.5, 1.0, 1.5 and 2.0% (w/w). Samples were incubated at 25?±?1°C and 20% moisture content for 150?days. At the end of incubation, available P in MC-treated soils was extracted by Olsen, AB-DTPA and 0.01?M CaCl₂ methods. Also, phosphorus was fractionated chemically into labile P (LP), non-occluded P(NP), re-adsorbed P (RP), occluded P (OP), calcium phosphates (CaP) and residual P. The results showed that there was a linear increase in soil available P with MC application. There was a significant positive relationship between Olsen-P, AB-DTPA-P and 0.01?M CaCl₂-P, and MC additions with slopes ranged from 0.471 to 0.583, 0.032 to 0.106, and 0.033 to 0.081, respectively. The increase in soil test P (STP) from MC additions was not related to the initial STP of the soils. A sharp increase in LP, NP and CaP and decrease in residual P concentration occurred in all soils with MC application. It can be concluded that MC applied to calcareous soils may enhance P nutrition of plants. Furthermore, applied P partitioning into the relatively available forms means the potential erosion losses of P to streams and other bodies of water.     

Heavy metal contamination of soils and tea plants in the eastern Black Sea region,NE Turkey

The study area covers two geologically different regions which have intensively been carpeted by tea plants in the eastern Black Sea. The rocks exposed in the region contain considerable amount of trace metals due to Upper Cretaceous massive sulfide formations and tertiary epithermal mineralizations. Tea plants that grow in soils derived from such mineralized rocks contain different concentrations of Cu, Pb, Zn, Fe, Cd, P, Al, Na, K, and S. The content ratios of most of the analyzed elements except Al are higher in basaltic and sedimentary rocks. To describe the transfer of metals from soil to tea leaf, the Freundlich-type model (log c _plant = ac _soil + log b) is used. The metal concentrations in leaves of tea plant in the studied soils are ranked as Zn > Cu > Pb > Al > Cd > Fe. The capacity of the plant to affect the metal accumulation decreased as follows: Fe > Cd > Pb > Cu > Zn > Al. Negative correlations were found between pH and availability of Cu, Pb, Zn, Mn, and Al elements by the tea plant. Experimental applications indicated that tea plant leaves growing on soils with high metal contents show some signs of toxicity. In soils where, particularly, ammonium sulfate fertilizer is used, metal uptake by the tea plant was found to be significantly higher as a result of extremely acidic character of the soil.     

不同茶园茶叶氟含量及土壤氟的形态分布

通过对我国中西南产茶区12个茶园土壤样品和茶叶样品的采集,探讨了不同茶园茶叶氟含量和茶园土壤氟的形态分布规律。老叶和嫩叶氟含量分别为221～1 504 mg/kg和49.0～602 mg/kg,老叶氟含量是嫩叶的2.5～8.1倍。各形态氟含量随土壤层次加深没有统一变化规律,但各层土壤不同形态氟含量均为残渣态铁锰氧化物态＞有机结合态＞水溶态＞交换态。土壤pH值、有机质含量和阳离子交换量对茶园土壤氟的形态分布有不同程度的影响。老叶和嫩叶氟含量随水溶态氟含量的增加均呈显著增加趋势,但与其他形态氟含量没有显著的相关关系。     

Amending highly weathered soils with finely ground basalt rock

Surface (0–10 cm) samples of 7 soils from tropical coastal Queensland were incubated at room temperature and at field capacity with finely ground (<150 μ) basalt rock for 3 months. The amendment was applied at 0, 1, 5, 25 and 50 t/ha to cover situations of moderate application rates to that where the amendment might be banded to produce high local concentrations. Having an abrasion pH of about 9, the amendment was able to reduce both active acidity (as estimated by an increase in soil pH) and reserve acidity (reduction in % Al saturation of the CEC). Increases in soil pH resulted in increased CEC, depending on the variable charge nature of each soil, accompanied by increases in exchangeable Ca, Mg, and K supplied by the basalt. The amounts of basic cations converted to exchangeable form constituted only a fraction of the amounts applied. Thus the cations held in reserve ensure that the effect of cation enrichment will be prolonged. In some soils phosphate sorption was significantly reduced by crushed basalt application. Furthermore, ‘available’ P as measured by extraction with 0.005 M H₂SO₄ was increased. These effects appear to be due to the release of silicate from the basalt as well as modest amounts of phosphate in the rock. Three extractants commonly used for estimating Si availability in sugarcane production indicated that all 7 soils contained sub-optimal levels of the element. Application of crushed basalt rock increased extractable Si levels above what is considered sufficient for this crop. The incubated soils were placed in columns and leached with the equivalent of 2750-mm (average wet season) rainfall. Re-analysis showed that the favourable chemical soil properties imparted by the amendment were retained. These results add further support to the contention that the effects of amelioration will continue for some time.     

Using soil survey data for series-level environmental phosphorus risk assessment

Choosing soil series scale for assessing phosphorus (P) retention and release characteristics may help relate routinely collected series-specific soil survey data with P retention and aid in designing series-specific P management strategies. Phosphorus retention and release characteristics of pedons collected from two benchmark upland soil series (Berks and Monongahela) and two floodplain (Huntington and Lindside) soil series of West Virginia (USA) were assessed by evaluating P sorption capacity (PSC, Langmuir method) and its major determinants, and effect of different levels of degree of P saturation (DPS) and soil test P (STP, Mehlich-1 P) on the desorbable P (0.01 M CaCl₂-extractable) concentrations. The PSC of the two floodplain soils, Huntington and Lindside, was similar but lower than PSC of upland Berks and Monongahela soils. However, thicker A horizons of Huntington and Lindside soils may compensate for their lower PSC. The B horizons exhibited higher PSC than A horizons. However, slow permeability and thinness of such horizons may discount the higher PSC effect. Relationship of PSC with ammonium oxalate extractable Al (AOX-Al) and Fe (AOX-Fe), dithionite–citrate–bicarbonate extractable Al (DCB-Al) and Fe (DCB-Fe), total C, clay content, and pH [soil:water ratio 1:1 (pH-water) and soil:0.01 M CaCl₂ solution ratio 1:2 (pH-CaCl₂)] showed that in general all except Fe and total C influenced PSC significantly. Aluminum associated with crystalline clay minerals particularly affected PSC, especially of upland soils. Most of the soils did not release considerable P even beyond the conventional critical limit of 25 % DPS for well-drained soils. DPS-desorbable P relationships, though, reflected poor reliability of DPS as an environmental index. At a given DPS and STP, surface horizons released more P than their subsurface counterparts and thus reflected the net sink character of subsurface horizons. Most of the soils did not show considerable release of P even beyond agronomically high STP levels (>23 mg kg^?1). The study provides an economical alternative to time and money-intensive lysimetric studies for assessing subsurface P loss. It reveals the workability of integrating environmental P studies with soil survey data and superiority of integrated assessment of environmental indices of P over the use of any single index.     

Comparison of extractability of Cd, Cu, Pb and Zn with sequential extraction in contaminated and non-contaminated soils

Various extraction procedures were employed for measuring extractable concentrations of potential toxic elements in soil. The extractability of Cd, Cu, Pb and Zn in four contaminated and four non-contaminated soils of Japan, was compared by single extraction (CaCl₂, DTPA, NH₄Cl, 0.1 M HCl and 1 M HCl ) and sequential extraction procedures [(six operationally defined chemical phases, viz. water soluble (Fl), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6) fractions)]. Extractability of metals from soils samples varied depending on metals and/or extradants used. Among the extradants, 1 M HCl extracted the largest proportion of Cd (79 to 96% of total), Cu (61 to 83%), Pb (51 to 99%) and Zn (23 to 52%) from soils followed by 0.1 M HCl, NH₄Cl, DTPA and CaCl₂. In all the extradants, the proportion of extractability of metals was higher in the contaminated soils than the non-contaminated soils. Regardless of soils and extradants, relative extractability was higher for Cd as compared to other three metals. The use of 1 M HCl may be recommended for first-level screening of soil contamination with heavy metals. The other four weak extradants are believed to provide a better assessment of bioavailable/mobile metals content in soils than 1 M HCl extradant. However, 0.1 M HCl mobilized all four metals irrespective of soil types, therefore, might be the best choice if only one extradant is to be used. The sequential extraction procedures showed 22 to 64% of total Cd was in the mobile fraction (sum of Fl to F3), while the corresponding values for Cu, Pb and Zn in this fractions were 2 to 23% suggesting higher mobility of Cd than other three metals. The single extraction procedures are simple and easy to perform and obtained results are comparable with sequential extraction procedure.     

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。     

Release kinetics and distribution of boron in different fractions in some calcareous soils

The aim of this study was to evaluate the release kinetics, speciation, and fractionation of boron (B) in some calcareous soils of western Iran. Ten surface soil samples were incubated with 100 mg B kg^?1 for a week at field capacity moisture. After air drying of samples, the trend of B release was experimented using sequential extraction with 10 mM CaCl₂. B speciation in soil solution was calculated for the first and the last steps of extraction by the visual MINTEQ program. The distribution of B among five fractions including exchangeable (F1), specially adsorbed (F2), bound by Fe–Mn oxides (F3), organically bound (F4) and residual (F5), was determined in control and spiked soils. The results indicated that the release rates were initially rapid followed by a slower reaction and the main proportion of the added B was extracted by CaCl₂. The release kinetics of B was described well with Elovich, parabolic diffusion, power function, and first-order equations. The speciation results revealed that the uncharged boric acid (H₃BO ₃ ⁰ ) was the dominant species in soil solutions. In control soils, B concentration in different fractions decreased in the following order: F5 > F1 > F2 > F3 > F4. In spiked soils, however, the largest and the smallest fractions were exchangeable and residual, respectively. This implies that B transformation from soluble to less mobile and non-labile forms is not a rapid process and requires more than a week. The significant relationship observed between kinetic parameters of power and parabolic equations and organically bound B fraction and OM content indicated that organic matter played an important role in B adsorption and release in calcareous soils.     

Formation of Zn-rich phyllosilicate, Zn-layered double hydroxide and hydrozincite in contaminated calcareous soils

Recent studies demonstrated that Zn-phyllosilicate- and Zn-layered double hydroxide-type (Zn-LDH) precipitates may form in contaminated soils. However, the influence of soil properties and Zn content on the quantity and type of precipitate forming has not been studied in detail so far. In this work, we determined the speciation of Zn in six carbonate-rich surface soils (pH 6.2-7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322-30,090 mg/kg Zn). Based on 12 bulk and 23 micro-focused extended X-ray absorption fine structure (EXAFS) spectra, the number, type and proportion of Zn species were derived using principal component analysis, target testing, and linear combination fitting. Nearly pure Zn-rich phyllosilicate and Zn-LDH were identified at different locations within a single soil horizon, suggesting that the local availabilities of Al and Si controlled the type of precipitate forming. Hydrozincite was identified on the surfaces of limestone particles that were not in direct contact with the soil clay matrix. With increasing Zn loading of the soils, the percentage of precipitated Zn increased from ∼20% to ∼80%, while the precipitate type shifted from Zn-phyllosilicate and/or Zn-LDH at the lowest studied soil Zn contents over predominantly Zn-LDH at intermediate loadings to hydrozincite in extremely contaminated soils. These trends were in agreement with the solubility of Zn in equilibrium with these phases. Sequential extractions showed that large fractions of soil Zn (∼30-80%) as well as of synthetic Zn-kerolite, Zn-LDH, and hydrozincite spiked into uncontaminated soil were readily extracted by 1 M NH₄NO₃ followed by 1 M NH₄-acetate at pH 6.0. Even though the formation of Zn-precipitates allows for the retention of Zn in excess to the adsorption capacity of calcareous soils, the long-term immobilization potential of these precipitates is limited.     

Effect of sheep manure and EDTA on the leaching of potassium from heavy metals contaminated calcareous soils

In this study, we examined the movement of potassium (K) in columns of contaminated calcareous soils by sheep manure and ethylene diamine tetraacetic acid (EDTA). Glass tubes, 4.9 cm in diameter and 40 cm in length, were packed with contaminated soils. The resulting 20-cm long column of soil had a bulk density of 1.3–1.4 g cm⁻³. Columns were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl₂, and sheep manure extract solutions. The amounts of K leached varied considerably between different soils (sandy loam and loamy sand) and leaching solutions. The amount leached with EDTA solution, varied from 7.2 to 66.7% of the extractable K when 20 pore volumes had passed through the column. The breakthrough curves of K in the EDTA and CaCl₂ were approximately similar, indicating they have similar ability to displace K from these contaminated calcareous soils. Thus, among leaching solutions application of EDTA and CaCl₂ on contaminated soils might enhance the mobility of K and large amounts of K will be leached.     

Fe and Al oxides distribution in some ultisols and inceptisols of southeastern Nigeria in relation to soil total phosphorus

Ten highly weathered soils in southeastern Nigeria were sampled from their typical A and B horizons for analyses. The objectives were to determine the different forms of Fe and Al oxides in the soils and relating their occurrence to phosphate availability and retention in the soils. The soils are deep and often physically degraded but are well drained and coarse in the particle size distribution. They are mostly dominated by kaolinite in their mineralogy with very high values of SiO₂. The soils are acidic with low soil organic carbon (SOC) contents. The elements in the exchange complex are also low thus reflecting in the low CEC of the soil. Available phosphorus (P) in the soils are generally low while total P ranged from 157 to 982 mg kg⁻¹ with an overall average of 422 mg kg⁻¹. Total Fe in the soil is highest and their order represented as follows: Fe_t > Fe_d > Fe_ox ≥ Fe_p. The pyrophosphate extractable Fe was always higher in the top soil than in the subsoil and was attributed to the fact that these forms of Fe are associated with organic matter which is more abundant in topsoil than in subsoil. Like in Fe forms, the order of Al occurrence could generally be presented as; Al_t > Al_d > Al_ox > Al_p. More Fe and Al oxides in the soils are strongly crystalline while a small quantity is poorly crystalline Fe forms. The amorphous forms of both Fe and Al are very low in the soils when compared with the crystalline forms. The oxides that show very strong affinity to total P are Fe_d–Fe_ox, Fe_d, Al_d, Fe_t, Fe_ox and Al_ox/Al_d. To overcome this problem of P retention in the soil, we recommend constant liming of these soils to neutralize them, application of organic matter and of high dosage of phosphate fertilizer to the soils.     

Evaluation of phosphorus leaching from contaminated calcareous soils due to the application of sheep manure and ethylenediamine tetraacetic acid

Organic amendment application to heavy metal contaminated soils may contribute to leaching of phosphorus (P). The objectives of this study were to determine the influence of sheep manure and ethylenediamine tetraacetic acid (EDTA) on the P leaching from a wide range of calcareous contaminated soils. Glass tubes, 4.9 cm diameter, and 40 cm long, were packed with contaminated soil. The resulting 20 cm long column of soils had bulk density of 1.3–1.4 g cm⁻³. The columns were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl₂ or sheep manure extract (SME) solutions. The breakthrough curves for P were different and the amounts of P leached varied considerably between different soils and leaching solutions. The amounts leached with SME were less than the amount added through the SME, indicating that some P was retained by the soil, mainly due to preliminary sorption of organic ligands on to the soil with the creation of new sorbing surfaces. The amount leached with EDTA solution varied from 9.9 to 46.3% of the extractable P when 15 pore volumes had passed through the column. Low amounts of P were leached by 0.01 M CaCl₂, which is likely to be due to the high concentration of soluble Ca used in the solution. Thus, among leaching solutions the application of EDTA and SME on contaminated calcareous soils might enhance the mobility of P and large amounts of P will be leached, leading to contamination of ground and surface waters.     

Assessment of isotopically exchangeable Al in soil materials using Al tracer

The solubility of aluminium (Al) in many acidic soils is controlled by complexation reactions with soil organic matter. In such soils, Al solubility is theoretically a function of the pool size of “active” Al, i.e., the total amount of Al that equilibrates with the soil solution within a defined period of time. To date, no reliable measurements of “active” Al in soil materials exist. In this study, we determined the isotopically exchangeable pool of Al (E_Al) as an operationally defined assessment of “active” Al in acidic mineral soils. The suitability of CuCl₂ and pyrophosphate (Na₄P₂O₇) as extractants for “active” Al was also evaluated. Eleven samples, mostly from spodic B horizons, were spiked with carrier-free ²⁶Al and equilibrated for different time periods (1-756 h). The size of the Al pool with which the ²⁶Al tracer exchanged increased with time during the whole experimental period. Thus, contact time between solid and solution phases needs to be defined when assessing the “active” Al pool. Values of E_Al obtained after 1 to 5 d of equilibration were equal to the amount of CuCl₂ extractable Al, but considerably smaller than the Na₄P₂O₇-extractable pool. Equilibration times greater than 5 d resulted in CuCl₂ extractable Al concentrations that under-estimated the “active” Al pool. Three of the investigated samples were rich in imogolite-type materials (ITM). In these samples, 30-50 % of the added ²⁶Al rapidly became associated with soil constituents in forms that could not be extracted by Na₄P₂O₇, indicating that a part of ITM may be in a dynamic state.     

赣南茶区生态地球化学环境

初步评价了赣南地区茶树生长的总体生态环境景观条件,着重进行了13个典型茶园的岩-土-茶地球化学调查,研究了茶园基岩、土壤元素地球化学特征,根据土壤有机质、营养元素全量和有效量评价了茶园的营养状况,为茶园生产管理、施肥提供了科学依据。通过与龙井茶元素含量的对比,评价了本区茶叶质量,探讨了茶叶内在品质与地质、地球化学背景的关系。     

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.     

Stability of aggregates of some weathered soils in south-eastern Nigeria in relation to their geochemical properties

The stability of some highly weathered soils of the tropics is controlled by their organo-mineral substances. Highly weathered soils from 10 different locations were sampled from their A and B horizons to determine their aggregate stability. The objective of the study was to determine the aggregate stability of the soils and their relationships with geochemical constituents. The major geochemical elements of the soils are quartz and kaolinite, SiO₂, Al₂O₃ and Fe₂O₃, while the dithionite extractable Fe and Al was greater than their corresponding oxalate and pyrophosphate forms. The mean-weight diameter from dried aggregates (MWD_d) and their corresponding wet mean-weight diameter (MWD_w) were related significantly (r = 0.64*). The dithionite extracted Al and Fe or the crystalline forms of these elements were outstanding in the stability of the aggregates. However, this did not diminish the influence of SOC reduced to third order level in the stability of the soils. The influence of SOC in these soils, however, indirectly manifested on the role of Fe_p and Al_p in the aggregation of these soils. The crystalline Fe and Al sesquioxides were very prominent in the aggregation and stability of these soils.     

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.     

Available contents of potentially toxic elements in soils from the Eastern Amazon

Background Values of potentially toxic elements (PTEs) in soils are typically obtained from total or pseudo-total contents, but not represent the fraction of these elements available for plant uptake due to the predominance of the stable forms. Available contents to plants, in turn, tend to be positively correlated with the potential risk of contamination of PTEs. In this study, we determined the available contents, extracted with Mehlich-III solution, of Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in Oxisols and Ultisols in the state of Pará, Eastern Amazon, Brazil. Available contents ranged from low to very low when compared to soils from other Brazilian regions and from other countries. Contents of PTE were higher in Oxisols than in Ultisols, except for Cu and Ni. In the Oxisols, PTEs were positively correlated with clay content. However, PTEs were not correlated with soil pH, organic matter and cation exchange capacity. In the Ultisols, Ba, Cu, Pb, and Mn contents were significantly correlated with pH, while Ni contents were correlated with the contents of silt.     

茶园土壤不同形态镍的含量及其影响因素

通过自然茶园土壤采样和室内实验分析,探讨浙江、江苏和安徽13个茶园土壤镍的污染状况、形态分布规律以及不同形态镍的含量与土壤镍总量和土壤理化性质的关系。结果表明：部分茶园土壤受到不同程度的镍污染;茶园土壤镍的形态分布有一定差异,按镍的含量多少排序,一般为残渣态＞交换态＞铁锰氧化物结合态＞有机结合态＞碳酸盐结合态;除了交换态以外的所有其他形态的镍含量均随土壤镍含量的增加而显著增加;碳酸盐结合态、铁锰氧化物结合态和残渣态镍含量随土壤pH的升高呈显著增加趋势,而交换态镍则呈减少趋势,但不显著;随土壤有机质含量的增加,铁锰氧化物结合态镍显著减少,而其他形态增加或减少的趋势均不显著;碳酸盐结合态、有机结合态和残渣态的镍含量均随阳离子交换量的增加显著增加;随粘粒含量的增加所有形态中的镍呈增加趋势,但除了残渣态外增加趋势均不显著。