Effect of chelating agents on phytotoxicity of lead and lead transport

Abstract

The major purpose of these experiments was to determine if Pb uptake by plants was significantly increased by chelating agents used in plant nutrition. The interaction of Pb with some other elements in barley plants (Hordeum vulgare L. C.V. Atlas 57) and bush bean (Phaseolus vulgaris L. C.V. Improved Tendergreen) was studied in a glasshouse with different rates of Pb in solution culture and in amended (control, S, CaCO₃, MgCO₃) Yolo loam soil with and without the chelating agent DTPA (diethylene triamine pentaacetic acid). In a solution culture experiment, 10^‐3 M Pb significantly decreased bush bean yields in both control and DTPA treatments. The CaCO₃ added to nutrient solution decreased the concentration of Pb in leaves, stems, and roots and prevented the toxicity of 10^‐3 M Pb⁺⁺. At high Pb levels, interactions between Pb and Mn and Pb and Fe were observed, except with CaCO₃. In the soil experiment, the yields of barley and bush bean were influenced only slightly by Pb. The Pb concentration in barley shoots and bush bean leaves and stems was increased considerably in the presence of DTPA, however. In the absence of DTPA, the effect of added Pb was very small in the control and S amended soil treatments and almost negligible in the CaCO₃ and MgCO₃ amended soil treatments. Application of DTPA facilitated the translocation of Pb, Fe, Mn, Cu, and Zn to shoots. The effect was dependent upon soil pH. Particularly, the Fe was increased by DTPA at low pH while the effect was negligible at high pH. This was opposite the effect on Pb. The DTPA resulted in considerable Pb transport to leaves and stems at high soil pH. The uptake pattern of Zn and Cu was similar to that of Pb. It can be expected that chelating agents can increase the migration of Pb to plants andincrease its uptake by plants, and hence, entry into food chains.     

Lithium toxicity in plants

Abstract

The toxicity of Li to three plant species was studied to determine if there were interactions with other elements and to determine if a chelating agent modified Li toxicity. Bush beans (Phaseolus vulgarls L. C.V. Improved Tendergreen), grown in solution culture, were sensitive to 0.5 X10^‐3Li which resulted in 10 μg/g in leaves, 48 in stems, and 24 in roots. Higher concentrations of Li produced marked reductions in plant yield accompanied by increased Li concentrations in leaf, stem, and root tissues. For most treatments, root concentrations of Li were lower than those in shoots, but those in stems were higher than those in leaves. Higher levels of Li decreased Zn in leaves, increased Ca in stems, and generally increased Fe and Mn in all plant tissues. Ethylenediamine tetraacetic acid (EDTA) resulted in slightly increased Ii levels in leaves, stems, and roots. Bush bean plants were injured slightly with 25 μg Li/g of Yolo loam soil applied as LiCl; 50 μg Li/g soil caused more severe injury. Leaf concentrations of about 200 μg Li/g resulted in significant yield reduction and around 600 μg//g of leaves resulted in severe toxicity. There were some interactions of Li with other elements which resulted in an increase of them in both leaf and stem tissues. Barley plants (Hordeum vulgare L. C.V. Atlas 57) were severely stunted when grown with 500 and 1000 μg Li/g soil as Li oxalate. Increasing the soil pH even further with lime and decreasing it with S had no influence on the toxicity. Shoot concentrations of Li ranged from 800 to over 2000 in the various treatments resulting in severe disruption of the Ca and K balance. Leaf concentrations of Li were higher than those for stems in cotton (Gossypium hirsutum L. C.V. Acala 442). Cotton was tolerant of a leaf concentration of 587 μg Li/g. High levels of Li increased concentrations of several elements in cotton leaves and in stems. Cotton leaves accumulated more Li than did bush beans.     

Impacts of Calcium Silicate Slag on the Availability of Silicon and Trace Contaminants in Rice (Oryza Sativa L.)

Calcium silicate slag from the phosphorus fertilizer industry has the potential to be used as a liming agent or for silicon (Si) fertilization in rice production, but it contains trace elements that may contaminate rice grain and straw. A greenhouse study was performed to evaluate the bioavailability of Si and trace elements from slag (0, 1000, 2000, and 4000 mg kg^?1) surface-applied or incorporated to a mineral soil and an organic soil. Slag application increased Si availability and rice grain yield relative to the control. Trace element and radioactivity in soil and rice grain were not significantly affected by slag supplementation. The applied slag showed minimal influence on plant available cadmium (Cd), chromium (Cr), or lead (Pb); however, copper (Cu) and zinc (Zn) in the organic soil increased, whereas Ni in the mineral soil decreased. Results indicate that the evaluated slag may be used as a Si fertilizer or liming amendment for rice with minimal environmental risks.     

Suitability of Urban Wastes for Crop Production in Zaria,Northern Nigeria: Bioavailability,Phytotoxicity, and Fractions of Micronutrients

The suitability of two composted solid urban wastes for crop production was evaluated in a pot experiment with sorghum (Sorghum bicolor) that focused on the geochemical fractions, bioavailability, and phytotoxicity of copper (Cu), manganese (Mn), and zinc (Zn). Total concentrations of Cu, Mn, and Zn in soil increased with increasing waste application, ranging from 1.6 to 48.2 mg kg^?1 for Cu, 84 to 474 mg kg^?1 for Mn, and 13.8 to 597 mg kg^?1 for Zn. Waste application significantly increased pH and electrical conductivity (EC) of the soil. Copper, Mn, and Zn in the waste-amended soil were speciated into mobile (F1), easily mobilizable (F2), occluded in Mn oxides (F3), organically bound (F4), occluded in amorphous Fe oxides (F5), occluded in crystalline Fe oxides (F6), and residual (F7) fractions to assess the lability of the metals. On the average, the F4 was the most dominant Cu and Zn fraction, accounting for between 37 and 60% of total Cu and from 14 to 40% of total Zn concentrations, whereas F3 was the dominant Mn fraction closely followed by F4. The concentrations of Cu, Mn, and Zn in sorghum dry matter (DM) decreased with increasing waste application, probably induced by osmotic stress and ionic toxicity. Tissue Zn (Y-Zn) and Mn (Y-Mn) correlated significantly with the F1 and F2 fractions, but pH was an overriding factor in predicting Cu and Zn bioconcentration. Used as soil amendments, the application rate for these Zaria urban wastes should be limited to ≤10% (w/w basis), as Zn in the sorghum tissue reached the toxic limit just from one application of the waste to soil.     

施用污泥后石灰性土壤中铜、锌、镉的植物有效性

The toxicity of trace elements (TEs), such as copper (Cu), zinc (Zn), and cadmium (Cd), often restrict land application of sewage sludge (SS) and there was little information about soil-plant transfer of TEs in SS from field experiments in China. In this study pot and field experiments were carried out for 2 years to investigate the phytoavailability of TEs in calcareous soils amended with SS. The results of the pot experiment showed that the phytoavailability of Zn and Cu in the SS was equal to 53.4%-80.9% and 54.8%-91.1% of corresponding water-soluble metal salts, respectively. The results from the field experiment showed that the contents of total Zn, Cu, and Cd in the soils increased linearly with SS application rates. With increasing SS application rates, the contents of Zn and Cu in the wheat grains initially increased and then reached a plateau, while there was no significant change of Cd content in the maize grains. The bioconcentration factors of the metals in the grains of wheat and maize were found to be in the order of Zn > Cu > Cd, but for the straw the order was Cd > Cu > Zn. It was also found that wheat grains could accumulate more metals compared with maize grains. The results will be helpful in developing the critical loads of sewage sludge applied to calcareous soils.     

Evaluation of immobilizing agents as soil quality conditioners in addition to their metal(loid) immobilizing effect

In trace metal (TM)-contaminated agricultural soils, management of TM availability is important for safe crop production. In addition, maintenance or improvement of soil quality is vital for sustainable crop cultivation. Decreased TM phytoavailability and increased soil quality can be achieved by the application of various immobilizing agents to soil, which can supply both macronutrients and organic matter. This study investigated the long-term influences of four common immobilizing agents on so...     

Extractability of major and trace elements from agricultural soils using chemical extraction methods: Application for phytoavailability assessment

Abstract

To assess soil-to-plant transfer of various elements more precisely, the concentrations of the elements extracted from soil samples using eight chemical solutions were compared with the results of a pot cultivation experiment of komatsuna (Brassica rapa L. var. perviridis) or buckwheat (Fagopyrum esculentum M.) using the soils. From agricultural fields in Aomori, Japan, 16 soil samples were collected. Elements in the samples were extracted using acids (1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃, 0.01 mol L^?1 HNO₃), chelating agents (0.05 mol L^?1 EDTA), neutral salt solutions (1 mol L^?1 NH₄OAc, 1 mol L^?1 NH₄NO₃, 0.01 mol L^?1 CaCl₂) and pure water. The 28 elements in the extracted solutions and plant samples were determined. The extractability of many metals was higher in 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ and the 0.05 mol L^?1 EDTA solutions than in the other extractants. Higher extractability using the NH₄OAc solution than the NH₄NO₃ solution was observed for some elements, in particular U. Extractability by pure water was not always lowest among these methods, probably because of dispersion of colloidal substances in the extracted solution. The pot cultivation experiment showed that the concentrations in soil and in the extracted fraction using 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ or the EDTA solution did not correlate with the concentration in plant samples for most elements. Plant uptake of Zn, Y and La by komatsuna correlated well with their concentrations in extracts with neutral salt solutions or 0.01 mol L^?1 HNO₃. Concentrations of Al, Cu and Cd in buckwheat were also correlated with the concentrations in the extracts.     

改良剂施用对重金属污染土壤溶液化学性质及豇豆生理特性的影响研究

本文研究了在不同生长时期凹凸棒土、硅藻土、泥炭、腐植酸对土壤重金属的钝化及豇豆生理特性的影响。结果表明:由于土壤的缓冲性,4种改良剂对土壤溶液pH影响较小;泥炭、腐植酸对Zn、Cu的钝化效果比凹凸棒土、硅藻土好,但4种改良剂对土壤溶液Pb和Cd浓度影响不明显;腐植酸、凹凸棒土均在不同程度上提高了豇豆叶片超氧化物歧化酶、过氧化物酶的活性,其中腐植酸的作用最为明显。除泥炭外,3种改良剂均使豇豆叶片的丙二醛、脯氨酸含量降低。受叶片衰老的影响,成熟期各改良剂对豇豆生理特性的作用不如苗期明显;冗余分析表明:4种改良剂对重金属的钝化效果依次为腐植酸、泥炭、凹凸棒土、硅藻土。本次试验结果说明有机物料腐植酸、泥炭可作为缓解豇豆重金属Zn、Cu胁迫的改良剂。     

不同前处理方法对秸秆金属元素原子吸收光谱分析结果的影响

秸秆中金属元素是关系农作物秸秆科学利用的重要组成部分,目前还没有统一的秸秆中金属元素原子吸收光谱(atomic absorption spectroscopy,AAS)测定方法标准,该研究采用原子吸收光谱测定黄芪(GBW10028)标准物质、玉米秸秆、小麦秸秆和棉花秸秆中金属元素含量,比较了不同前处理方法对样品中K、Cu、Fe、Zn和Mg分析结果的影响。结果表明:微波消解、干法灰化和湿法消解测定黄芪(GBW10028)标准物质中金属元素含量差异性显著(P<0.05),微波消解比干法灰化、湿法消解准确度高。微波消解对玉米秸秆、小麦秸秆和棉花秸秆中各金属元素的影响与黄芪(GBW10028)标准物质趋于一致。微波HNO3与微波HNO3-H2O2测定结果差异性不显著(P>0.05),微波HNO3比微波HNO3-H2O2和微波HNO3-H2SO4测定结果稳定。微波HNO3是进行秸秆样品金属元素含量测定时较准确简便的前处理方法。     

Selective utilization of copper and zinc in three species of Vaccinium (Ericaceae)

The concentrations of the trace elements copper and zinc were determined in field‐collected samples of three ericaceous dwarf shrubs of the genus Vaccinium. The average elemental concentrations were rather regular in the three species. The actual minor element levels of the individual samples showed, however, highly significant interspecific differences in the elemental compositions.

The calculation of the discriminant factor values (i.e. the comparative element ratios for the plant samples and for their substrata) resulted in clear species‐specific patterns in the element utilization. Thus, obvious selectivity was recognized in the uptake of copper and zinc by the three Vaccinium species. Of the species studied, V. myrtillus appeared to be an accumulator of copper in relation to zinc, whereas V. uliginosum showed the most efficient uptake of Zn in relation to Cu, and V. vitis‐idaea showed an intermediate pattern in the minor element utilization.     

Soil Extraction of Readily Soluble Heavy Metals and As with 1 M NH4NO3-Solution - Evaluation of DIN 19730 (6 pp)

Background, Aims and Scope   The German DIN 19730 (1997) describes a method for the extraction of readily available trace elements from soil by shaking the soil with 1 M NH4NO3-solution. Based on this method trigger and action values for the transfer of heavy metals and arsenic from soils to plants have been published in the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV 1999). The chemical mechanisms involved in this soil extraction procedure were evaluated in some detail to create requirements to improve environmental risk assessment for soil contaminations.Methods   The chemical mechanisms involved when soil is extracted with 1 M NH4NO3-solution were evaluated. This was followed by a laboratory experiment to quantify the formation of soluble metal ammine complexes during the extraction. Cd, Zn, Ni, Cu, Co and Hg were extracted from 16 soils by 1 M NH4NO3, 1 M KNO3 and water. pH was adjusted in 5 steps between 5.0 to 7.5. The potassium cation (K+) and the ammonium cation (NH4+) behave similarly when cations from soil surfaces are desorbed, because they have almost identical ion radii (e.g. 0.133 and 0.143 nm). K+ does not form ammine complexes with other ions, whereas, due to the increasing formation of NH3 from NH4 by dissociation with rising pH, metal ammine complex formation is an important process in soil extraction when using ammonium salt solutions. A difference in the extraction efficiency of 1 M NH4NO3- and 1 M KNO3-solution for a given soil can therefore be attributed to the formation of soluble metal ammine complexes. Conclusion   Our experiments resulted in considerably higher extraction rates of Cu, Cd and Hg by 1 M NH4NO3-solution as compared to 1 M KNO3-solution. This effect, caused by the formation of soluble metal ammine complexes, was only evident in soils with higher readily soluble heavy metal contents and a soil pH above 6 – 6.5 for Cu and 7 – 7.5 for Cd. Further chemical mechanisms involved when soils are extracted with 1 M NH4NO3 are a moderate decrease in pH and an increase in ionic strength. Most of the colloids and parts of soluble metal-organic complexes are precipitated due to the high ionic strength. High ionic strength also decreases the activity of metal-OH+ species and the electrostatic potential of the particle surfaces, which in turn, increases the desorption of heavy metal cations from negatively charged soil surfaces. In contrast, the adsorption of anions like arsenate is favoured by the decreasing electrostatic potential. The prediction of heavy metal uptake by plants from the results of the 1 M NH4NO3-solution extraction fits well for elements, which are mainly bound by low strength electrostatic forces to the soils. Such conditions are found in acidic soils for Cd and Tl, which have a low tendency for hydrolysis compared to other heavy metals. The correlation between 1 M NH4NO3 soil extraction and plant uptake is less significant for Ni and Zn. Only low positive correlation coefficients have been found for Pb, As, Hg and for the Cu-uptake by wheat. Imprecise prediction of plant uptake of heavy metals by the extraction with 1 M NH4NO3-solution is mainly caused by conditions leading to an overestimation of plant availability such as elements are strongly bound to soils, or low soluble trace element contents in soils. Neutral to alkaline soil pH can also lead to imprecise prediction due to increasing formation of soluble metal-organic (Cu, Pb, Hg) and metal ammine (Hg, Cu, Cd) complexes and less importantly due to the formation of colloids. Therefore, at low 1 M NH4NO3-extractable soil contents usually no high plant contents are to be expected. Recommendation and Outlook   Extraction of soil with 1 M NH4NO3-solution is a suitable method for the determination of readily soluble and plant available trace element contents. The chemical soil extraction process may cause misleading predictions of the transfer of trace elements to plants for some soil properties. This knowledge should be used to improve risk assessment of soil contaminations. It has to be considered, that the processes involved in plant uptake of trace elements are too complex to expect that just one soil extraction method can always guarantee a correct prognosis of toxicological significant element contents in plants. Soil analyses may be used for the preliminary examination of suspicious areas and the demarcation of contaminated areas. The results of soil analyses should be checked additionally by plant analyses especially under conditions with a high probability for misleading results by the 1 M NH4NO3-extraction. Alternatively, extraction with 1 M KNO3-solution can be performed to exclude the effect of metal ammine complex formation.     

北京市边缘区土壤重金属污染的初步研究

基础资料为采集于北京城市边缘区的29个土壤剖面表层和底层58个样品6种重金属全量分析数据,以本区重金属自然土壤元素背景值作为评价标准,计算出各样点剖面表层和底层土壤单因子污染指数。应用对应因子分析手段, 初步揭示了北京市边缘区土壤重金属污染的空间分异特征。结果表明,北京市边缘区土壤重金属总体污染状况不明显,只有Hg元素属于轻微污染范围。不同样点间重金属污染水平比较显示,Hg污染水平差异明显,Pb、Cd、As、Zn、Cu污染差异不大。     

Identifying the Sources and Contamination Status of Potentially Toxic Trace Elements in Agricultural Soils

Elevated concentrations of potentially toxic trace elements in agricultural soils contribute to soil pollution affecting food quality and safety. We assessed pollution levels in agricultural systems, lowland rice (LL) and highland cash crops (HL), by comparing with non-agricultural soils (NA). Correlation analysis and principal component analysis (PCA) were performed, and geo-accumulation index (I_geo) and pollution loading index (PLI) were calculated. Zinc in LL, and Cd in LL and HL, were significantly higher than in NA. The I_geo values of cooper (Cu), lead (Pb), nickel (Ni), zinc (Zn), and cadmium (Cd) ranged from uncontaminated to moderately contaminated (Class 0 to 2) for LL, HL, and NA. Overall, trace element levels were categorized as unpolluted based on PLI. Soil properties significantly correlated with Cu, Pb, Ni, and Zn concentrations but not with Cd. Based on PCA, sources of origin for Cu, Pb, Ni, and Zn were lithogenic, while the sources for Cd was anthropogenic in the studied agricultural soils.     

昆山市农业土壤基本性质与重金属含量及二者的关系

研究了昆山市农业土壤基本性质和土壤中的重金属含量,并对二者的相关关系进行了分析。结果表明:昆山市农业土壤基本全为壤土,土壤pH值平均为6.50,土壤有机质平均含量为30.53g/kg,土壤CEC平均值为17.51cmol/kg,且各区之间变幅不大;昆山市主要污染重金属Cd、Pb和Hg全量大小排序基本为黄泥土>青泥土>青紫土>乌栅土;土壤重金属含量和土壤理化性质间的关系复杂,如全量As与pH值、有机质含量和全N含量呈极显著负相关,而全量Hg与土壤中有机质含量、全N含量、碱解N含量、CEC呈极显著正相关。     

Discrimination between Japanese and Chinese Products using trace elements concentration of kernel in pickled Japanese apricot

pp. 875–880

The trace-element composition of kernel in pickled Japanese apricot (Prunus mume Sieb. et Zucc.) was determined using an inductively coupled plasma optical emission spectrometer in order to distinguish between Japanese products and Chinese products.

Strontium and barium concentrations in the kernels of Chinese products were 10 or more times those of the Japanese ones. When based on 8.0 mg kg^?1 of strontium concentration in kernel, 93.2% of sample was distinguished as Japanese products or Chinese ones.

Applying principal component analysis using 9 elements (Mn, Zn, Fe, Ni, Ba, Sr, Cu, Co, Cr), the pickled Japanese apricots tend to separate into two countries. Linear discriminant analysis (LDA) using 9 elements allowed a reasonable classification of pickled Japanese apricots according to the country of production.

The result of the analysis of K-nearest neighbors (KNN) was better than that of LDA.     

影响城市土壤重金属污染因子的关联度分析

城市土壤深受人为活动的影响 ,具有明显的重金属人为富积的特点 ,认识这些土壤重金属丰度、形态与土壤理化性质及周围环境因子的关系 ,有助于更好地保护和修复城市土壤生态系统。本文对南京城市土壤中Pb、Zn、Cu、Cd四种重金属元素的含量和形态特征进行了研究 ,并用灰色系统理论方法对南京城市土壤重金属污染的影响因子进行了灰色关联度分析 ,认为最主要影响因子是距工业区远近 ,其次是土壤粘粒含量、pH值 ,而交通车流量、生产生活废弃物在土壤中堆埋的比例和土壤有机质对城市土壤重金属污染的影响相对较小     

Colza (Brassica napus, v. Jaguar) Responses to Low Level of Metal Inputs Through Sewage Sludge Application: Induction of phytochelatin synthesis (10 pp)

Background, Aim and Scope   Most studies of sewage sludge disposal effects on plants have focused on high metal loadings. Less attention has been paid to plant responses to trace metal loadings below the recommended limit values. Materials and Methods: Here, a lysimetric experiment was conducted to assess the uptake, distribution and binding of trace metals by metal-induced, sulfhydryl-rich peptides (phytochelatins) in colza (Brassica napus, v. Jaguar) grown on a clayey, silty soil amended with a sewage sludge compost containing trace metal contents far below the recommended limit values established by French legislation. Chemical fractionation of unamended and sludge-amended soils was performed using a sequential extraction technique. Results: Copper concentrations in plant tissues were not affected by compost disposal. Its application at a single rate equivalent to 30 t/ha stimulated the growth of plants. Lead was not detectable in the plant material (< 1 mg g-1 dry wt.). Plants grown on the amended soil accumulated significantly more zinc than control plants. These phytochelatin complexes detected in leaves had a lower molecular weight than those extracted from roots. Those extracted from roots were composed of one type of phytochelatins (PCs) such as in leaves or a mixture of glutathione, PC2 and PC4. In comparison with control plants, sewage sludge compost application caused the synthesis of longer chain PCs in roots and in leaves. Furthermore, in comparison with control roots, glutathione and phytochelatin mixtures of higher molecular weight were detected in roots produced on the amended soil, whereas no significant increase in \total\ Cu and Zn content was observed in these organs after sludge application. Discussion: Compost application induces a significant increase in the proportion of the most labile forms of zinc and especially its pH 4.7 acid-soluble forms and, as a consequence, a higher accumulation of zinc in plants. Effects of copper are limited due to its strong affinity for humic substances and lead does not seem to be transported in any organ of plants. The presence of phytochelatins, even in plants grown on the unamended soil, proved the ability of colza to synthesize them in the presence of zinc and copper. Conclusions: These primary results seem to prove, on one hand, ability of colza (Brassica napus, v. Jaguar) to synthesize phytochelatins as well as in roots, in leaves and, on the other hand, the sensitivity of the PC induction as suggested by their identification in plants grown on the control soil. Synthesis of longer chain PCs in roots and in leaves, and formation of glutathione and phytochelatin mixtures in roots, are plant responses to sewage sludge compost application. Recommendations and Perspectives: Phytochelatin analysis is thus supposedly able to be one of the bioindicators that may be used as an ecotoxicological risk assessment of wastes. Due to its ability to synthesize phytochelatins, colza could be chosen as a plant test. Phytochelatin analysis could also be limited to roots (more sensitive than leaves). However, further experiments are needed. Quantitative analysis of phytochelatins had not been carried out due to insufficient amounts of pure phytochelatin standards, that had allow us to better study relationships between trace metal amounts to vegetal response.     

不同土壤因子对中药牛蒡子品质的影响

牛蒡子为菊科2年生草本植物牛蒡(Arctium lappa L.)的成熟果实。牛蒡的生长情况与环境之间有密切的联系,其品质是由多种因子决定的,主要包括气候因子、地形因子、土壤因子等。本文采用双变量相关和偏相关分析相结合,因子分析和逐步回归法相结合的方法,对牛蒡子品质与土壤因子之间的关系进行了充分研究,结果表明:牛蒡子的品质受气候因子与土壤因子(特别是一些微量元素)影响,选取气候因子中的年均温作为控制变量,对牛蒡子品质指标与土壤因子进行偏相关分析,得到气候因子影响土壤因子与牛蒡子品质指标的相关性程度;进行因子分析之后,可以发现土壤因子对牛蒡子的品质指标有显著的影响,且各个土壤因子影响不同,其中发现牛蒡子的生长虽然受到N、P、K等主要生长元素的影响,但微量元素如As、Hg、Ca、Zn、Pb等对牛蒡子的生长影响也较大。因此在引种栽培过程中,注意根据实际情况增减微量元素。     

露天煤矿周边不同深度土壤重金属空间变异及分布特征

以准东露天煤矿周边为研究对象,对矿区周围52个土壤样点分别采取0~10、10~20和20~30 cm不同深度的土壤样品,在室内测定了Zn、Cr、Hg和As 4种重金属含量。采用地统计学方法,定量分析了不同深度土壤重金属元素的空间变异性,并通过普通克里金插值深入分析了其水平和垂直方向的空间分布规律。研究表明:土壤重金属元素含量大小顺序为CrZnAsHg,其中Cr、Hg和As的均值分别超过了新疆背景值的0.6倍、2.1倍和1.8倍,超标率均在60%以上,存在较严重的污染。从空间变异性来看,半方差函数符合高斯、指数和球状模型,其块金值均为正值,说明易受正基底效应的影响,而表层和深层土壤重金属元素的块金系数均在25%~75%,呈现中等空间相关性,受随机因素和结构性因素共同作用的影响。重金属元素在水平空间分布具有一定的规律性,其高值密集在矿区周边及工业园附近,而低值出现在研究区南部和古尔班通古特沙漠边缘,总体呈现南北方向递增趋势;而垂直分布上,Zn和Hg元素随深度的增加其含量递减,而As元素在表层和其他两层的空间分布上存在较大的差异。