Evaluation of four chemical extractants for metal determinations in wetland soils

Abstract

Wetland soils (hydric soils) are unique in their chemical characteristics compared to upland soils. It is known that they are capable of removing a variety of wastes from polluted water entering the wetland including metals and potentially toxic heavy metals. When these metals are determined in wetland soils, it is necessary to use the proper chemical extractant(s). Four commonly used chemical extractants (Mehlich 1, Mehlich 3, 0.1M HCl, and DTPA) for soil fertility evaluation were selected to measure metal concentrations of three different wetland soils/spoils. Soil samples were collected from the constructed wetland cells which were lined with Abernathy silt loam topsoil and two different mine spoil materials [collected from active coal strip‐mined sites in Alabama (pH 5.9) and Tennessee (pH 3.2)]. Mehlich 3 extracted the most zinc (Zn), iron (Fe), manganese (Mn), calcium (Ca), magnesium (Mg), potassium (K), sodiumm (Na), and aluminum (Al), while 0.1M HC1 extracted more cadmium (Cd), copper (Cu), and lead (Pb). Extractants followed the same trend in removing quantities of the metals from the three soil/spoil materials, with DTPA generally extracting the least amount of the metal (the trend was Mehlich 3 > 0.1N HCl > Mehlich 1 > DTPA). However, DTPA removed larger quantities of metals from Tennessee spoil compared to Alabama spoil and topsoil, suggesting the higher effectiveness of DTPA under acidic conditions. Metal concentrations in plant tissue did not show a definite trend in correlation with metals extracted by the four chemical extractants.     

Application of High Copper and Zinc Compost and Its Effects on Soil Properties and Growth of Barley

Abstract

A compost of high copper (Cu) and zinc (Zn) content was added to soil, and the growth of barley (Hordeum vulgare L.) was evaluated. Four treatments were established, based on the addition of increasing quantities of compost (0, 2, 5, and 10% w/w). Germination, plant growth, biomass production, and element [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), Cu, manganese (Mn), and Zn] contents of soil and barley were determined following a 16‐week growing period. Following harvesting of the barley, analysis of the different mixtures of soil and compost was performed. Micronutrient contents in soils as affected by compost additions were determined with diethylene–triamine–pentaacetic acid (DTPA) (Cu, Mn, Fe, and Zn) or ammonium acetate [Ca, Na, Mg, K, cation exchange capacity (CEC)] extractions, and soils levels were compared to plant uptake where appropriate. Increasing rates of compost had no affect on Ca, Mg, or K concentration in barley. Levels of Cu, Zn, Mn, and Na, however, increased with compost application. High correlations were found for DTPA‐extractable Cu and Zn with barley head and shoot content and for Mn‐DTPA and shoot Mn content. Ammonium acetate–extractable Na was highly correlated with Na content in the shoot. High levels of electrical conductivity (EC), Cu, Zn, and Na may limit utilization of the compost.     

不同高粱种质对污染土壤中重金属吸收的研究

利用重金属含量较高的污水污染土壤,以未污染土壤作对照,种植8个甜高粱品种、2个饲用高粱品种和1个粒用高粱品种,检测8种重金属在高粱植物体内不同器官的含量,以研究不同高粱种质对重金属的吸收特性。结果表明:甜高粱对汞(Hg)、镉(Cd)、锰(Mn)和锌(Zn)的吸收在两种土壤间差异显著,对钴(Co)、铬(Cr)、铅(Pb)和铜(Cu)的吸收差异不显著。Mn在甜高粱体内含量表现为未污染土壤高于污染土壤;而Zn含量在不同器官之间存在差异,未污染土壤叶中含量远高于穗,穗中含量远高于茎和根。不同重金属在甜高粱体内的储存部位不同,污染土壤上Hg、Cd、Co、Cr和Zn在根中积累量较高,Cu、Mn和Pb在穗中的积累量较高。甜高粱、饲用高粱和粒用高粱对重金属的吸收、运输及储存在品种之间差异较大,同一品种对不同重金属的吸收也存在差异。饲用高粱表现为叶部对Cr和Zn的储存量较高,而粒用高粱‘晋中0823’则显示了茎对多种重金属的储存能力。高粱根对土壤中重金属的富集系数较高,为0.02(Pb)~0.23(Cd),转移系数变幅为0.21(Co)~3.42(Pb)。对同一种重金属的吸收量品种间差异较大,甜高粱‘西蒙’根对Co、Cr、Cu、Mn、Pb和Zn具有高富集系数,粒用高粱‘晋中0823’茎对Hg、Cd、Mn、Pb和Zn富集系数较高。高粱对重金属的吸收能力与转移能力不同步,甜高粱‘绿能1号’具有对多种重金属的高转移能力,粒用高粱‘晋中0823’只对Zn有较高的转移能力。因此本文认为甜高粱对不同重金属的吸收和转移有选择性。对Zn吸收并转移到地上部后,首先储存在叶和穗中,当吸收量足够大时,茎和根也成为储存器官;对Mn的吸收与其他重金属的吸收存在竞争作用,Hg吸收后很少向地上部转移;而对Cu、Mn和Pb吸收后在穗部的储存量较大。饲用高粱与甜高粱相比对重金属的吸收未显示明显的不同,甜高粱‘西蒙’根对多种重金属具有强储存能力,而粒用高粱‘晋中0823’的茎秆显示了比甜高粱更强的储存能力,甜高粱‘绿能1号’对多种重金属的转移能力较强。所以,选择富集和转移能力均强的高粱品种能更有效地吸收土壤中的重金属,达到修复污染土壤的目的。     

Soybean response to the application of several elements on a low‐manganese soil

Abstract

Certain soils in the Lower Atlantic Coastal Plain are Mn‐deficient and because of their inherent properties, deficiencies of other elements might be expected. The response of soybean [Glycine max (L.) Merr. cv. ‘Ransom'] to annual soil applications of B, Cu, Fe, Mo, S, and Zn with and without Mn was examined. The study was conducted on an Olustee‐Leefield sand (Ultic Haplaquod‐Arenic Plinthaquic Paleudult) in 1975, 1976, and 1977. Seed yields, and soil and plant tissue concentrations of certain of the applied elements were determined. Soil pH increased from 6.4 in 1975 to 7.0 in 1977 as a result of lime applications.

Of the seven elements studied, only Mn significantly increased soybean seed yield compared to the check. Leaf concentrations of the respective elements were higher where the element was added than they were in plants grown on the check plots. In 1977, after three years of elemental additions, plant concentrations of Mn, Cu, and Zn were higher, relative to checks, than in 1975. In 1977, with the higher soil pH levels, plants from check plots had lower concentrations of Mn, but unexpectedly equal levels of Cu and higher levels of Zn than in 1975. This unexplained increase in plant Zn was also found in Other experiments in the same field during the same time period. Double acid extracted more soil Mn, Cu, and Zn than did DTPA from similar treatments during all three years. The DTPA‐extractable soil Mn correlated much better with plant Mn than did double acid Mn values, especially over years where a change in soil pH occurred. Correlation coefficients comparing extractable soil versus plant values for Cu and Zn data combined over years were higher for double acid than DTPA, although coefficients for the Cu and Zn data were still generally much lower than for the Mn data.     

长期肥料试验对土壤和水稻微量元素及重金属含量的影响

长期肥料试验会影响土壤中微量元素和重金属状况以及作物对微量元素和重金属的吸收。本文研究了长期的不同施肥处理对土壤、糙米中微量元素Cu、Zn、Fe、Mn和重金属Pb、Cd含量的影响,结果表明:经17a连续施用猪粪及秸秆还田显著增加了土壤Cu、Zn和Cd全量,而土壤Fe、Mn和Pb全量在不同施肥处理间没有显著差异;施肥增加了土壤有效态Cu、Zn和Fe含量,其中施用猪粪及秸秆还田的3个处理显著增加了土壤有效态Cu、Zn和Cd含量,而土壤有效态Pb含量在不同施肥处理间没有显著差异。不同处理糙米Cu、Zn、Fe、Mn和Pb含量变化较小或没有显著性差异,而在3个施猪粪和秸秆还田处理中,糙米Cd含量均超过国家食品卫生标准(>0.2 mg kg-1)。水稻地上部吸收积累Cu、Zn、Fe、Mn、Pb和Cd总量与其地上部生物量呈正相关,土壤Cu、Zn、Cd有效态与全量含量呈极显著相关关系,而糙米中的镉含量与土壤镉含量有较好的相关关系。长期施用畜粪导致土壤Cd污染问题应引起高度重视。     

Residual heavy metal concentrations in sludge‐amended coastal plain soils ‐ I. Comparison of extractants

Abstract

The purposes for this research were: to examine the long‐term residual effects of farmland applications of municipal sludges from four treatment technologies on the total and extractable Zn, Cu, Mn, Fe, Pb, Ni and Cd concentrations in Coastal Plain soils; to investigate the effects of sludge sources and rates on the effectiveness of soil extractants to remove the various metals; and to determine correlation coefficients for soil extractable versus plant accumulation in tobacco. The extractants evaluated were Mehlich 1 and 3, and DTPA‐pH 7.3. Composite Ap horizon soil samples and tobacco leaf samples were obtained in 1984 from research plots at two sites in Maryland that were established in 1972 and 1976, respectively, using sludge materials from three wastewater treatment facilities in the Washington, D.C. metropolitan region. Similar application rates were used at both sites.

A wide range in soil pH values was found among treatments at each site. Significant (p ≤ 0.05) increases were observed in total Zn, Cu, Fe, Pb, Ni, and Cd for all sludge sources with increased rates; however, values for total soil Mn exhibited high variability in all cases. The rankings among the extractants varied for some elements depending on the sludge sources. For Zn, the rankings were Mehlich 1 > Mechlich 3 > DTPA‐pH 7.3 across all sources and rates. For Cu, Mehlich 3 > Mehlich 1 > DTPA‐pH 7.3 was found for soils amended with Blue Plains digested (BPD) and Piscataway limeddigested (PLD) sludges but Mehlich 1 ≥ DTPA pH 7.3 > Mehlich 3 for Blue Plains limed compost (BPLC) and Annapolis Fe and heat treated (AFH) sludges. Concerning extractable Mn, Mehlich Mehlich 1 > Mechlich 3 > DTPH pH 7.3 was the order for BPLC and AFH sludges but Mehlich 3 > Mehlich 1 > DTPA‐pH 7.3 was observed for BPD and PLD sludges. The rankings among extractants for Fe (Mehlich 3 > Mehlich 1 > DTPA‐pH7.3), Ni (Mehlich 3 ≥ Mehlich 1 > DTPA‐pH 7.3), Pb (Mehlich 3 > DTPA‐pH 7.3 > Mehlich 1) and Cd (Mehlich 1 > Mehlich 3 > DPTA‐pH7.3) were somewhat similar across all sludge sources. Significant correlation coefficients were obtained for all three extractants for soil extractable vs. plant Zn, Cu, Ni, and Cd at both sites; however, Mehlich 3 was not significant for Mn. Also, neither of the extractants produced significant coefficients for Fe and Pb.     

Effect of elemental sulphur and sulphur containing waste in a calcareous soil in Turkey

The effect of elemental sulphur (S) and S containing waste applications on soil pH treated with 0–2,000 kg ha^‐l elemental S, and 0–100 tons ha‐¹ of waste was determined in the field and the pots. Sorghum (Sorghum bicolor L.) was grown in a Lithic Xerorthent soil which was taken from where the field experiment was conducted in pots receiving 5 kg soil. Plants were harvested 20 weeks after planting or 30 weeks after the applications for determination of dry matter yield and phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) uptake by shoots. EC, NaHCO₃‐extractable P, and DTPA‐extractable Fe, Zn, Mn, Cu also were measured in pot soil at the 5th, 10th, and 30th weeks. All treatments led to a decrease in soil pH though pH tended to increase again during course of time in both field and pot experiments. The both elemental S and waste applications in pot experiment caused an increase in dry matter yield and P, Fe, zinc (Zn), Mn and Cu uptake (mg pot^‐1) by shoots in sorghum plant. There was also an increase in EC of soil due to both applications of S. The concentration of available P extracted by NaHCO₃ in the pot soil, though not significantly different, was slightly higher compared with the control. Waste applications increased DTPA‐extractable Fe content of the soil, DTPA‐extractable Mn and DTPA‐extractable Cu. DTPA‐extractable Zn content, however, was reduced by the same applications.     

RELATIONSHIPS AMONG METALS IN THE SOLID PHASE OF SOILS AND IN WILD PLANTS

The relationships between plant and soil systems were investigated using multivariate statistical methods and relative ionic impulsions. Soil samples were taken from three locations and wild plant species consisted of:Poa, Pteridium aquilinum, Diplotaxis, Plantago lanceolata andTrifolium repens. The content of Mg, Ca, Na, K, Mn, Fe, Pb, Co, Ni, Cu, Zn and Cr in soils and plants was determined. A five-step chemical fractionation procedure (speciation) was applied to soil samples. Total metal contents were determined and amounts extracted with HCl, EDTA and DTPA were measured. Pb, Co, Ni, Cu, Fe, Zn, Cd and Cr in soils (considered as microconstituents for plants) show a greater number of statistically significant relationships with plant contents than those shown by macroconstituents (Mg, Ca, Na, K and Mn). On the other hand, only Zn and Pb extracted with EDTA and DTPA seem to be related to metal contents in wild plants. When using relative ionic impulsions, any soil fraction (obtained from the fractionation procedure, including the soluble fraction, which is the sum of all the fractions except the residual) is suitable for the study of soil-plant system, suggesting a global balance among all the fractions. Our results suggested an active assimilation for K and a passive uptake for Na, Ca and Mn. Furthermore, Fe seemed to favour the active assimilation of the other microelements.     

添加物对镉、锌、铅污染土壤上小白菜的生长和养分吸收的影响

A pot experiment was carried out to study the effects of two amendments, lime and calcium magnesium phosphate, on the growth and Cd,Pd,Zn,Cu,Mn,Fe,N,P and K uptake of pakchoi (Brassica chinensis) in a Cd,Pb and Zn polluted acid soil in the southern part of China. The growth of pakchoi was apparently improved by lime and calcium magnesium phosphate application, the uptake of Cd,Pb,Cu and Zn by pakchoi was significantly depressed and the symptom caused by heavy metals pollution was eliminated. Meanwhile, the absorption of N,K and Mn was also inhibited by these amendments. Soil pH was the main factor controlling the uptake of the heavy metals by pakchoi. This suggests that lime and calcium magnesium phosphate could be used as effective amendments for eliminating the toxicity of heavy metals to the vegetable and inhibiting their absorption by the crop.     

Comparison of MnSO4 and MnEDTA for soybeans grown on two soils in the greenhouse

Abstract

A greenhouse experiment was conducted to compare MnSO₄ and MnEDTA as Mn sources. Four soil‐applied rates of each source were applied to two Coastal Plain soils, a Leefield s (pH 6.3) and an Alapaha is (pH 7.0). Plants were grown for 40 days and dry tissue weights were recorded along with leaf contents of Mn, Zn, Fe and Cu. The same ions were extracted from the soil with DTPA. The chelate source caused no differences in either extractable soil Mn or plant Mn between soils or among rates even when added at its highest rate of 2 μgMn/g. The sulfate source increased extractable soil Mn and plant Mn over the various rates but more so for the Alapaha soil than for the Leefield. Plant weights were not different between sources except on the averages for the Leefield soil. However, for the Leefield soil and the sulfate source, plant weights were lower for the check than for intermediate Mn rates due to Mn deficiency and lower for the high Ma rate (50 μg/g) presumably due to toxicity. A correlation coefficient of 0.866** was obtained for soil‐extracted Mn versus plant Mn concentration indicating that the DTPA was a good extractant for these two soils. High correlations between plant and soil Mn versus plant and soil Zn, Fe, and Cu for the chelate source showed that the MnEDTA affected metal ion availabilities other than just Mn. It was concluded that the MnSO₄ was the better source at the rates used and that for these soils the best rate was S μgMn/g applied to the soil.     

Extractability and plant uptake of heavy metals in alum shale soils

Abstract

Fifty soil samples (0–20 cm) with corresponding numbers of grain, potatoes, cabbage, and cauliflower crops were collected from soils developed on alum shale materials in Southeastern Norway to investigate the availability of [cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and manganese (Mn)] in the soil and the uptake of the metals by these crops. Both total (aqua regia soluble) and extractable [ammonium nitrate (NH₄NO₃) and DTPA] concentrations of metals in the soils were studied. The total concentration of all the heavy metals in the soils were higher compared to other soils found in this region. Forty‐four percent of the soil samples had higher Cd concentration than the limit for application of sewage sludge, whereas the corresponding values for Ni, Cu, and Zn were 60%, 38%, and 16%, respectively. About 70% the soil samples had a too high concentration of one or more of the heavy metals in relation to the limit for application of sewage sludge. Cadmium was the most soluble of the heavy metals, implying that it is more bioavailable than the other non‐essential metals, Pb and Ni. The total (aqua regia soluble) concentrations of Cd, Cu, Zn, and Ni and the concentrations of DTPA‐extractable Cd and Ni were significantly higher in the loam soils than in the sandy loam soils. The amount of NH₄NCyextractable metals did not differ between the texture classes. The concentrations of DTPA‐extractable metals were positively and significantly correlated with the total concentrations of the same metals. Ammonium nitrate‐extractable metals, on the other hand, were not related to their total concentrations, but they were negatively and significantly correlated to soil pH. The average concentration of Cd (0.1 mg kg^‐1 d.w.) in the plants was relatively high compared to the concentration previously found in plants grown on the other soils. The concentrations of the other heavy metals Cu, Zn, Mn, Ni, and Pb in the plants were considered to be within the normal range, except for some samples with relatively high concentrations of Ni and Mn (0–11.1 and 3.5 to 167 mg kg‘¹ d.w., respectively). The concentrations of Cd, Cu, Zn, Ni, and Mn in grain were positively correlated to the concentrations of these respective metals in the soil extracted by NH₄NO₃. The plant concentrations were negatively correlated to pH. The DTPA‐extractable levels were not correlated with plant concentration and hence DTPA would not be a good extractant for determining plant availability in these soils.     

Vermicomposts and/or Arbuscular Mycorrhizal Fungal Inoculation in Relation to Metal Availability and Biochemical Quality of a Soil Contaminated with Heavy Metals

A greenhouse pot experiment was conducted to investigate how the addition of two vermicomposts (commercial or produced from damaged greenhouse tomatoes) and/or inoculation with arbuscular mycorrhizal (AM) fungi affected availability and extractability of P, K and trace metals and biochemical quality of a soil contaminated with heavy metals. The pots were planted with Trifolium repens L., which was harvested 40?days after germination. Shoot and root dry matter of T. repens increased by the addition of both vermicomposts. P, K, Fe, Mn, Cu and Zn uptake by T. repens increased after vermicompost addition, whereas Ni, Pb and Cd concentrations were below the detection limit of the method used. After harvest, AB-DTPA-extractable Fe, Cu, Zn, Cd and Pb decreased in the organically amended soil, whereas AB-DTPA P, K and Mn increased. The addition of both vermicomposts, particularly which made from damaged tomatoes, boosted dehydrogenase, ??-glucosidase and urease activities in the postharvest soil, implying a higher microbial functional diversity and biochemical quality in this amended soil. Although phosphatase activities were greater in the postharvest soils with higher AB-DTPA-extractable metals, the other enzyme activities were negatively affected. The inoculation of the soils with AM fungi had weak effects on plant growth, as well as on the availability and extractability of metals and enzyme activities compared to non-inoculation.     

Metals in stocked Lake Trout (Salvelinus namaycush) in lakes near Sudbury,Canada

Muscle tissue from stocked lake trout (Salvelinus namaycush) from lakes near the smelters at Sudbury, Canada was analyzed for Al, Cu, Fe, Hg, Mn, Ni, and Zn. Metals in tissue were not abnormally high compared with fish from lakes farther away from the smelters. Tissue concentrations of Al, Fe, Mn, and Zn declined significantly after stocking. Because metal concentrations were lower in hatchery water than the study lakes, this decline in tissue metal suggests that diet plays a prominent role in the uptake of these metals in lake trout. Only Hg showed evidence of accumulation to levels that might be harmful for human consumption, and then only in a few older, larger trout. In contrast, tissue Mn and Zn were inversely correlated with trout weight. Fluctuations, independent of age, body weight or time of year, were observed in tissue concentrations of Al, Cu, and Zn. Annual cycles, independent of pH and alkalinity were observed in tissue concentrations of Fe, Hg, Mn, and Ni. Bioaccumulation of metal proved to be an unfounded concern for the rehabilitation of fish populations in lakes near Sudbury.     

Advances in fungal-assisted phytoremediation of heavy metals: A review

Trace metals such as manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) are essential for many biological processes in plant life cycles. However, in excess, they can be toxic and disrupt plant growth processes, which is economically undesirable for crop production. For this reason, processes such as homeostasis and transport control of these trace metals are of constant interest to scientists studying heavily contaminated habitats. Phytoremediation is a promising cleanup technology for soils polluted with heavy metals. However, this technique has some disadvantages, such as the slow growth rate of metal-accumulating plant species, low bioavailability of heavy metals, and long duration of remediation. Microbial-assisted phytoremediation is a promising strategy for hyperaccumulating, detoxifying, or remediating soil contaminants. Arbuscular mycorrhizal fungi (AMF) are found in association with almost all plants, contributing to their healthy performance and providing resistance against environmental stresses. They colonize plant roots and extend their hyphae to the rhizosphere region, assisting in mineral nutrient uptake and regulation of heavy metal acquisition. Endophytic fungi exist in every healthy plant tissue and provide enormous services to their host plants, including growth enhancement by nutrient acquisition, detoxification of heavy metals, secondary metabolite regulation, and enhancement of abiotic/biotic stress tolerance. The aim of the present work is to review the recent literature regarding the role of AMF and endophytic fungi in plant heavy metal tolerance in terms of its regulation in highly contaminated conditions.     

包头市铜厂周边土壤中重金属垂直分布特征与形态分析

为了解包头市铜厂周边地区土壤剖面中重金属污染状况,采用火焰原子吸收分光光度法和Tessier连续提取法,对土壤中6种重金属（Cu,Zn,Mn,Ni,Pb和Cd）的垂直分布特征、形态及潜在生物可利用性进行了分析。结果表明:研究区土壤剖面各层土壤中6种重金属含量均超过内蒙古土壤背景值,Cu,Pb和Cd为主要污染物。随采样深度的增加,Cu,Zn,Pb和Mn的含量呈现下降趋势,且由相关性系数可知重金属Cu,Zn和Pb可能有相同人为或自然污染源;土壤剖面中6种重金属均主要以残渣态存在,含量均在50%以上,对生物危害较小;潜在生物可利用性分析结果为:Cu（32.61%） > Mn（31.85%） > Ni（24.90%） > Zn（16.60%） > Cd（15.23%） > Pb（14.87%）,Cu和Mn的潜在生物可利用性较大,其次为Ni,Zn,Cd和Pb潜在生物可利用性较小。     

Evaluation of soil extractants to estimate available micronutrients under wheat‐field conditions

Abstract

Three extracting reagents were evaluated by correlation analyses to provide the best index of Zn, Cu, Mn and Fe availability to wheat (Triticum aestivum L.) plants growing under open field conditions. Twenty one soils were selected to obtain the widest range in properties of soils of the land wheat cultivated. The magnitude of the extractive power varied in the following order: 6NHCl ? EDTA + NH₄OA_C, pH4.65 > DTPA‐TEA, pH 7.3. The mild extractants, EDTA and DTPA, gave the same order of removal of micronutrients being Zn < Cu < Fe < Mn. The acid extractant was on the contrast more effective on Cu and Fe with respect to Zn and Mn, respectively. Wheat concentrations of Zn, Mn and Fe were significantly correlated to soil micronutrients. Highly significant relationships were found for Zn extracted by DTPA solution (r = 0.737***) and for Mn and Fe extracted by EDTA solution (r = 0.710*** and r = 0.564**). Plant Zn and Mn were also well predicted by the acid extraction. The absence of correlation for plant Cu vs. soil Cu occurred probably because of wheat concentrations almost constant, ranging from 5.0 to 8.0 mg/kg.     

Metal Extractability in Binary and Multi-metals Spiked Calcareous Soils

In the present study, a laboratory experiment was designed to compare the 0.01 M calcium chloride (CaCl₂) and diethylenetriaminepentaacetic acid (DTPA) extraction methods for their ability to predict cadmium (Cd), copper (Cu), iron (Fe), Manganese (Mn), nickel (Ni), and zinc (Zn) availability and mobility in five calcareous soils. The soils were spiked with different amounts of metals (0, 50, 100, 200, and 400 mg kg^?1) both in binary (Cu and Zn; Ni and Cd; Fe and Mn) and in multi-systems (Cd, Cu, Fe, Mn, Ni, and Zn) and incubated for 1 months at field capacity. In metal-spiked soils, both extraction methods showed a linear relationship of extractable to total metals for all soils. The fraction of total metals extracted by DTPA was much higher than the fraction extracted by CaCl₂, which was attributed to the formation of soluble metal-complexes in the complexing extracts calculated by the Visual Minteq program. DTPA extraction method showed higher selectivity for Cu over other metals both in binary and in multi-systems. Different order of metals extractability was found in binary and multi-systems for both extraction methods. Solid/solution distribution coefficient (K_d) was calculated by the ratio of the solid phase to soil solution concentration of metals extracted by CaCl₂ or DTPA extraction methods. Both in binary and in multi-systems, the average K_d (l kg^?1) of metals by soils were in the order of Mn (5398) > Fe (4413) > Zn (3376) > Cu (2520) > Ni (969) > Cd (350) in the CaCl₂-extractable metals and Fe (35) ≥ Ni (34) > Zn (18) > Mn (11.2) > Cu (6.3) > Cd (4) in the DTPA-extractable metals. Results showed that among the six studied metals, Cd had the lowest K_d, implying a relative higher mobility in these calcareous soils. The Visual Minteq indicated that in the CaCl₂-extraction method and in both binary and multi-systems the dominant species for Cu, Mn, Ni, and Zn were Cu²⁺, Mn²⁺, Ni²⁺ and Zn²⁺, respectively, while for Cd and Fe, the dominant species were CdCl⁺ and Fe(OH)²⁺, respectively.     

Comparison of Copper,Manganese, and Zinc Extraction with Mehlich 1, Mehlich 3, and DTPA Solutions for Soils of the Brazilian Coastal Tablelands

Deficiency of micronutrients is increasing in crop plants in recent years in Oxisols and Ultisols in the tropics. The predominant soils in the coastal tablelands of Brazil are Ultisols and Oxisols, with low cation exchange capacity and kaolinitic clay mineralogy. Soil copper (Cu), manganese (Mn), and zinc (Zn) extracted by the Mehlich 1 solution, currently used in the regional soil-testing laboratories, were compared with those extracted by the Mehlich 3 and diethylenetriaminepentaacetic acid (DTPA) solutions in a greenhouse experiment with 10 soil samples (0–20 cm deep) collected from representative Ultisols and Oxisols from various locations in the region. Corn was grown as a test crop, and its dry matter and micronutrient uptake was measured at 30 days of growth. Soil Cu, Mn, and Zn extracted with the three solutions were significantly correlated (0.65–0.95 range for r values), with the Mehlich 3 solution extracting greater quantities than the Mehlich 1 and DTPA solutions. Zinc and Cu taken up by corn plants were significantly related to their soil-extractable levels measured at harvest with all three of the solutions, except for Zn DTPA. However, similar relations between plant uptake and soil extractable Mn were poor, except for DTPA extracting solution.     

Phytoremediation Potential of Vetiver Grass (<Emphasis Type="Italic">Vetiveria zizanioides</Emphasis>) for Treatment of Metal-Contaminated Water

Phytoremediation using vetiver grass (Vetiveria zizanioides) has been regarded as an effective technique for removing contaminants in polluted water. This study was conducted to assess the removal efficiency of heavy metals (Cu, Fe, Mn, Pb, Zn) using vetiver grass (VG) at different root lengths and densities and to determine metals uptake rate by plant parts (root and shoot) between treatments (low and high concentration). Removal efficiency for heavy metals in water by VG is ranked in the order of Fe>Pb>Cu>Mn>Zn. Results showed that VG was effective in removing all the heavy metals, but removals greatly depend on root length, plant density and metal concentration. Longer root length and higher density showed greater removals of heavy metals due to increased surface area for metal absorption by plant roots. Results also demonstrated significant difference of heavy metals uptake in plant parts at different concentrations indicating that root has high tolerance towards elevated concentration of heavy metals. However, the effects were less significant in plant shoot suggesting that metals uptake were generally higher in root than in shoot. The findings have shown potential of VG in phytoremediation for heavy metals removal in water thus providing significant implication for treatment of metal-contaminated water.     

Micronutrient Levels in Sugar Beet in Soils of Greece

A survey was conducted in order to estimate micronutrient levels in plants and soils of 215 farms in Greece cultivated with sugar beet. Soils were analyzed for particle-size distribution, pH, organic carbon (C), CaCO₃, and DTPA-extractable copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn). Sugar beet leaves were analyzed for the same metals. Also, aboveground biomass (top), root, and raw sugar yields were recorded. DTPA-extractable Fe and Mn were above critical levels in all cases, whereas Cu and Zn were above critical levels in 49% and 24% of the soil samples, respectively. Concentrations of the four metals in plant tissue were similar or higher than the sufficiency range. Concentrations of DTPA-extractable Fe and Mn, and plant Zn and Mn, were significantly and negatively correlated with soil pH. Soil pH and DTPA-extractable Fe seemed to have a significant positive impact on root, top, and raw sugar yields. However, in all cases, less than 14% of the variance of the sugar beet parameters was explained by soil characteristics.