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1.

Purpose  

Lead contamination is ubiquitous, and much attention has been paid due to its toxicity. The phyllomanganate birnessite is the most common Mn oxide in soils. The MnO6 octahedral layers may have significant Mn vacancies in the hexagonal birnessites. Among heavy metal ions, birnessites possess the greatest adsorption affinity and capacity for Pb2+. The aim of this study was to understand the relationship between vacant Mn octahedral sites and Pb2+ adsorption.  相似文献   

2.
Akram FATEMI 《土壤圈》2017,27(6):1105-1115
Knowledge on potassium ion(K~+) release from soils makes K fertilizer recommendation more efficient and profitable.Kinetics of K~+release under continuous fertilization of no fertilizer(CK), urea(N), triple superphosphate(P), and urea + triple superphosphate(NP) without K fertilizer was investigated in calcareous(chloritic and kaolinitic) soils on the Miandarband Plain in Kermanshah Province of Iran.The results showed that the kinetics of K~+release included an initial reaction and a slow reaction.The phosphateand NH_4~+-induced K~+release followed the same rate process during the rapid(2–192 h) and slow release periods(192–1 090 h).There were no significant differences in the cumulative K~+released from the chloritic and kaolinitic soils among all the treatments.The cumulative K~+released was positively correlated with P adsorption capacity for the chloritic(r = 0.461, P 0.05) and kaolinitic soils(r = 0.625, P 0.01), and negatively correlated with K fixation potential for the chloritic(r = 0.720, P 0.01) and kaolinitic soils(r =-0.513, P 0.01).There was a significant(P 0.001) interactive effect of K fixation potential × P adsorption capacity on the cumulative K~+released for both soil groups.The initial release rate(IRR) index(a·b, where a and b are the rate coefficients of the power function equation) for the chloritic soils was significantly(P 0.05) higher under applications of P and NP than N and CK.The IRR index values among different fertilization treatments were in the order of NP = P N = CK for the chloritic soils, and N =P NP CK for the kaolinitic soils.This study showed that K fixation potential and P adsorption capacities controlled K~+release from soils.This information will be helpful for precise fertilizer recommendations for the studied soils.  相似文献   

3.

Purpose

The study is aimed at the analysis of the spatial–structural organization of Pb(II) in Chernozem soils and the relationship between the metal ion and the soil components using X-ray absorption spectroscopy and chemical extractive fractionation.

Materials and methods

In a model experiment, soil samples were artificially contaminated with elevated rates of Pb(NO3)2 and PbO (2000 and 10,000 mg kg?1). The samples of mineral phases (bentonite, gibbsite, kaolinite, calcite, and hydromuscovite) were saturated with Pb2+ ions. The sequential fractionation of Pb in the soil was conducted by the Tessier method. X-ray absorption near-edge fine structure (XANES) spectra at the Pb LIII-edge (13.040 keV) were obtained on a Rigaku R-XAS Looper spectrometer. Extended X-ray absorption fine structure (EXAFS) LIII-edge Pb was measured at the Structural Materials Science beamline of the Kurchatov Center for Synchrotron Radiation.

Results and discussion

The results of successive extraction showed that Pb is associated with strongly bound organic substances, Fe and Mn (hydr)oxides, and carbonates. An increase in the portion of exchangeable fraction is observed under extreme loads. At the addition of Pb in the form of oxide and nitrate to the soil, the fractional compositions were similar, which indicates the good transformation of PbO in Chernozem. The features of XANES spectra indicate different orbital transitions in the electron shells of Pb2+ ions for monoxide (PbO) and soluble salt (Pb(NO3)2), which affect the ion properties and determine the individual structure of the coordination sphere. The analysis of XANES revealed that sorption of Pb in the soil samples and in the samples of mineral phases does not change its bond valence.

Conclusions

The increased degree of soil contamination with Pb is accompanied by decreasing the stable connection between metal and soil components. Lead ions in bentonite, kaolinite, hydromuscovite, gibbsite, and calcite are incorporated in the positions of the inner-sphere complex replacing some aluminum ions in the octahedral sites. This results in changes the Pb–O distances in Pb-bearing octahedrons. We may suggest that Pb2+ is also sorbed by dimer (Pb–Pb) silicate and/or aluminum groups. The structure of adsorbent surface plays the key role in the sorption of Pb2+ by mineral phases.
  相似文献   

4.

Background

Evidence of trivalent manganese (Mn3+) in the aqueous phase of soils is unknown so far although this strong oxidant has large environmental implications.

Aims

We aimed to modify a spectrophotometric protocol (porphyrin method) and to discriminate between Mn2+ and Mn3+ in the aqueous phase of forest soils based on kinetic modeling.

Methods

We investigated manganese speciation in 12 forest floor solutions and 41 soil solutions from an acidic forest site by adjusting pH and correcting for absorbance.

Results

The solutions showed broad ranges in pH (3.4−6.3), dissolved organic carbon (DOC, 1.78−77.1 mg C L−1), and total Mn (MnT, 23.9−908 µg L−1). For acidic solutions, a pH-buffer was added to increase the pH of the solutions to 7.5−8.0, and background absorption was corrected for colored solutions, that is, solutions high in DOC. This was done to accelerate the reaction kinetics and avoid overestimation of MnT concentrations. After the pH and color adjustments, the comparison of MnT concentrations between the porphyrin method and optical emission spectrometry showed good agreement. Trivalent Mn, which is stabilized by organic ligands, constitutes significant proportions in both forest floor solutions (10−87%) and soil solutions (0.5−74%).

Conclusions

The dissolved Mn3+ is present in acidic forest soils. Thus, we revise the paradigm that this species is not stable and encourage to apply the revised method to other soils.  相似文献   

5.
Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate（FDA） hydrolysis were measured in two red soils spiked with Pb^2＋ ranging from 0 to 2 400 mg kg^-1 to relate the enzyme activity values to both plant growth and the levels of available and total Pb^2＋ concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month’s incubation and then after planting of celery（Apium graveolens L.） and Chinese cabbage（Brassica chinensis L.）. Enzyme activities in the red soil derived from arenaceous rock（RAR） were generally lower than those in the red soil developed on Quaternary red earths（REQ）. At high Pb^2＋ loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb^2＋ loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb^2＋ than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.  相似文献   

6.
The parameters of adsorption of Cu2+, Pb2+, and Zn2+ cations by soils and their particle-size fractions were studied. The adsorption of metals by soils and the strength of their fixation on the surface of soil particles under both mono- and polyelement contamination decreased with the decreasing proportion of fine fractions in the soil. The adsorption capacity of the Lower Don chernozems for Cu2+, Pb2+, and Zn2+ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem ∼ clay loamy southern chernozem > loamy southern chernozem > loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions (C max and k), the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu2+ ≥ Pb2+ > Zn2+. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem > loamy chernozem > loamy sandy chernozem. The analysis of the changes in the parameters of the Cu2+, Pb2+, and Zn2+ adsorption by soils and their particlesize fractions showed that the extensive adsorption characteristic, namely, the maximum adsorption (C max), was a less sensitive parameter characterizing the soil than the intensive characteristic of the process—the adsorption equilibrium constant (k).  相似文献   

7.

Purpose

TiO2 photocatalytic degradation of tetracycline (TC) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including cations, anions, organic acids, and surfactants.

Materials and methods

The solution of TC with TiO2 was irradiated by medium mercury lamp. The concentrations of TC and metal ions were analyzed by HPLC and AAS, respectively. The degradation efficiency of TC was calculated based on TC disappearance.

Results and discussion

Photocatalysis was very effective for TC removal. The degradation efficiency of TC was significantly enhanced in the presence of Cu2+/Pb2+, SO4 2?/Cl?, and humic acid (HA) in the examined range, but did no change with Ni2+, Cd2+, or Zn2+. In addition, the results also showed that solution Cu2+ and Pb2+ ions could be reduced during the process, while Ni2+, Cd2+, and Zn2+ were still kept in the solution. However, tannic acid (TA), gallic acid (GA), citric acid (CA), salicylic acid (SA), hydroxypropyl-β-cyclodextrin (HPCD), polyoxyethylene lauryl ether (Brij35), or polyoxyethylenesorbitan monooleate (Tween80) significantly decreased the degradation efficiency of TC.

Conclusions

The photocatalytic approach could be successfully applied to remove TC, and environmental factors significantly influenced its degradation efficiency. It would be useful to understand the environmental behaviors of TC and for the implementation of remediation strategies of TC.  相似文献   

8.

Background, aim and scope  

The combined pollution of bensulfuron-methyl (BSM) and heavy metal Pb has been a common problem in agro-ecological environment in southern China. As an important natural clay mineral, the kaolinite structure possesses great advantages in many processes due to its high chemical stability and low expansion coefficient. The adsorption of BSM on kaolinite was therefore investigated at varying Pb2+ concentrations (0, 100, 500 and 1,000 mg kg−1) and different pH levels (3, 4 and 5) using the batch equilibration experiment.  相似文献   

9.

Purpose  

Abiotic dechlorination of organochlorine pollutants seems to occur more efficiently in nature than previously thought. Ferrous (Fe2+) and sulfide (S2−) ions have been shown to be effective dechlorinating reagents. However, little is known about the interactions between Fe2+ and S2− during dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)-ethane (DDT) in soil, in spite of the fact that these ions co-exist in waterlogged soils.  相似文献   

10.
在实验室条件下,采用重金属Cd2+、As5+、Cu2+、Pb2+和Cr3+处理黄松稻田土壤、紫色稻田土壤和红壤稻田土,28d后分析重金属污染对水稻田土壤的硫酸盐还原菌(SRB)种群数量和硫酸盐还原活性(SRA)的影响。结果表明,在每千克干土中加入200mgPb2+时,对稻田土壤的SRB种群数量和SRA有促进作用;当加入的Cd2+、As5+、Cu2+、Pb2+和Cr3+每千克干土分别超过1.0、30、500、400和200mg时,对稻田土壤SRB种群数量和SRA有明显抑制作用。随着加入量的增加,重金属对水稻田土壤的SRB种群数量和SRA的抑制作用越来越强,水稻田土壤通过自身来恢复SRB种群数量和SRA所需的时间也越长。同一种重金属元素对不同土壤的SRB种群数量和SRA抑制的污染临界值也有差异。  相似文献   

11.
The authors reported that the relative bonding strength between ligand of soil colloid surface and cations could be obtained easily by the measurement of MCSA, and that the MCSA corresponded to the constant of Langmuir's adsorption isotherm equation.

The relative bonding strength of cations with respect to kaolinitic soil clay at pH 6 was, Cr3+>Fe3+, Al3+>Ga8+>Cu8+>Pb2+>Y3+, La3+>Mn2+>Ni2+, Co2+> Zn2+>Sr2+, Mg2+>NH4+, K+, and with respect to colloid with humus coating, Y3+, La3+>Pb2+>Cu2+, and the other orders were same.

The solubility of cations in soil colloid aqueous dispersion system was calculated from the values of MCSAs, and considered as follows, Y3+, La3+, Cu3+, Pb3+, Mn2+, Ni2+, CO2+: concentration in soil solution and soil geochemical mobility may be regulated by the specific adsorption reaction, Zn2+, Mg2+, Sr2+, K+, NH4+: concentration in soil solution and soil geochemical mobility may be regulated by the non-specific adsorption reaction, but at neutral to alkaline condition, Zn2+ and Mg2+ may specifically adsorb on soil, clays, Fe3+, Cr3+, Al3+, Ga3+: concentration in soil solution and soil geochemical mobility may be regulated by the solubility of their oxide hydrates.  相似文献   

12.

Purpose

Field survey and sampling of vegetable greenhouse soils were conducted in Shouguang, Shandong Province, and Ningbo, Zhejiang Province to study the acidification and salinization characteristics of soils with different initial soil pH values and greenhouse cultivation time.

Materials and methods

The pH, electrical conductivity (EC), and ion composition of 74 composite soil samples were analyzed to evaluate their relation to soil acidification and salinization.

Results and discussion

Compared with their corresponding open-field soils, acidification and salinization of the greenhouse soils occurred in both 0-20 cm and 20-40 cm soil layers for the Shouguang and Ningbo soils. The soil pH decreased gradually at different rates as greenhouse cultivation time increased in the two surveyed regions, but the opposite trend was observed for soil EC. For the Shouguang soils, while the percentages of K+ and NO3 ? increased dramatically and Ca2+ and HCO3 - decreased significantly after the soils were converted to greenhouse use, the correlation between soil pH and EC was significant, and the stepwise multiple regression analysis further showed that there was a significant correlation between pH and the percent of Ca2+ and HCO3 ?.

Conclusions

Soil acidification and salinization are common in greenhouse soils with different initial soil pH. Soil acidification in the Shouguang soils is a result of decrease in the percent of Ca2+, HCO3 ? due to over application of N and K fertilizers. Future research should be devoted to understanding the relevant mechanisms in greenhouse soils with lower initial soil pH values to assess if there are correlations between soil acidification and salinization under greenhouse cultivation.  相似文献   

13.
The equilibria as well as the rates of adsorption and desorption of the ions Pb2+, Cu2+, Cd2+, Zn2+, and Ca2+ by soil organic matter were determined in batch experiments as a function of the amount of metal ions added to an aqueous suspension of HCl-washed peat. Simultaneous determination of the metal ions and hydrogen ions in the solution by atomic absorption spectrophotometry and pH-measurements showed that the adsorption of one divalent metal ion by peat was coupled with the release of two hydrogen ions. Since this equivalent ion-exchange process causes a corresponding increase of the electric conductivity of the solution, the rates of the adsorption and desorption processes were determined by an immersed conductivity electrode. The distribution coefficients show that the selective order for the metal adsorption by peat is Pb2+ > Cu2+ > Cd2+≌ Zn2+ > Ca2+ in the pH range of 3·5 to 4·5. The slope of -2, as observed in a double logarithmic plot of the distribution coefficients versus the total solution concentration confirms the equivalence of the ion-exchange process of divalent metal ions for monovalent H3O+ -ions in peat. The absolute rates of adsorption, as well as the rates for the fractional attainment of the equilibrium, increase with increasing amounts of metal ions added. This behaviour is also observed for the subsequent desorption of the metal ions by H3O+-ions. At a given amount of metal ions added, the absolute rates of adsorption decrease in the order Pb2+ > Cu2+ > Cd2+ > Zn2+ > Ca2+, while the rates for the fractional attainment of the equilibrium decrease in the order Ca2+ > Zn2+≌ Cd2+ > Pb2+ > Cu2+. The half times for adsorption and desorption were in the range of 5 to 15 sec.  相似文献   

14.
The thermodynamic calculations were made for the contents of Pb and Cd compounds in soil solutions and water extracts of the meadow-steppe and meadow solonetzes (Rostov oblast) based on their prescribed analytic concentrations of 3 and 5 μg/l, respectively. The solonetzes studied are characterized by their high carbonate content and high alkalinity. The activity of Pb2+ and Cd2+ was shown to be many times lower than their total concentration in the solution due to the association of these metals with carbonate and other anions and the formation of hydroxocomplexes CdOH+ and PbOH+. This fact is one of the reasons for the low input of Pb2+ and Cd2+ to plants growing on calcareous soils.  相似文献   

15.
Batch experiments were conducted to study the effect of freeze-thaw frequency on the adsorption behavior of Pb2+ and Cd2+ and its related mechanisms. The results indicated that the adsorption capacities of Pb2+ and Cd2+ to the freeze-thaw treated soil were lower than those to the unfrozen soil, and with increasing freeze-thaw frequency, the adsorption capacities of them decreased. These were attributed to the fact that freeze-thaw cycles reduced pH value, CEC, organic matter content, and free iron oxide content of soil, and these soil properties presented negative correlations with freeze-thaw frequency. Freeze-thaw cycles reduced specific adsorption capacities of Pb2+ and Cd2+ and enhanced nonspecific adsorption ratios of Pb2+ and Cd2+ compared with the unfrozen soil. The higher freeze-thaw frequency, the higher nonspecific adsorption ratio was. However, the relationship between specific adsorption capacities of Pb2+ and Cd2+ and freeze-thaw frequency was opposite. Furthermore, the adsorption processes to the unfrozen and freeze-thaw treated soils were spontaneous, for Pb2+, its adsorption to soil was endothermal process, for Cd2+, on the contrary.  相似文献   

16.

Purpose

Understanding of the interactions between cations, mineral particles, and organic matter (OM) in soils is of paramount importance in plant nutrition and environmental science, and thus, these phenomena have been studied extensively. At present, an effective and simple tool to investigate these interactions does not exist. Based on previous studies of Wien effect in suspensions, the interactions of cations with soil mineral particles, complicated by the presence of organic matter, can be easily determined by means of Wien effect measurements, which was the objective of this study.

Materials and methods

A paddy soil originating from a yellow-brown soil, rich in organic matter, served as a test sample, from which the clay fraction of less than 2 μm in diameter was separated. Organic matter of aliquots of the clay fraction was removed by the oxidation with hot H2O2, and the natural and OM-free samples were saturated with various cations: Na+, K+, Ca2+, and Cd2+. The effects of OM present in the paddy soil on the interactions between the cations and the soil mineral particles were investigated by measuring the suspension Wien effect with a homemade apparatus, SHP-2.

Results and discussion

The weak electrical field electrical conductivities (EC0) of suspensions of the natural soils saturated with various cations were higher than those of the OM-free soils. The rate of increase in electrical conductivity of suspensions of the OM-free soil, except that of suspensions saturated with Na+, at electrical field strengths >50～100 kV?cm?1 was higher than those of the natural soil suspensions. The presence of OM increased the mean free binding energies of cations other than Na+. The increasing binding energies for K+ and Ca2+ were 0.56 and 0.57 kJ?mol?1, respectively, which were significantly larger than the increase for Cd2+ as only 0.03 kJ?mol?1. The binding energies of various cations on both natural and OM-free soils were all in the order: Na+?<?K+?<?Ca2+≈Cd2+. As opposed to its effect on the binding energies, the presence of OM reduced the mean free adsorption energies of the cations. Except for Na+, the adsorption energies of K+, Ca2+, and Cd2+ at field strengths >50 kV?cm?1 were lower in the natural soil as compared with the OM-free soil, and the differences between the adsorption energies became larger with increasing field strengths. The presence of OM made the zeta potential of the soil particles saturated with Na+ and K+ positive, and the particles saturated with Ca2+ and Cd2+ negative.

Conclusions

Organic matter affected the interactions of cations with soil mineral particles significantly. Binding and adsorption energies, which were quantitative measures of the interactions between cations and soil particles, could be determined by Wien effect measurements in suspensions. The binding energies on natural soils were larger than those on the corresponding OM-free soils, and the adsorption energies on the natural soils were lower than those on OM-free soils.  相似文献   

17.
Abstract

Nonexchangeable potassium (K) release kinetics of six major benchmark soil series of India as affected by mineralogy of clay and silt fractions, soil depth and extraction media was investigated. The cumulative release of nonexchangeable K was greater in smectitic soils (353 mg K kg?1 at 0‐ to 15‐cm depth and 296 mg K kg?1 at 15‐ to 30‐cm depth, averaged for 2 soils and 3 extractants) than in illitic (151 mg K kg?1 at 0‐ to 15‐cm depth and 112 mg K kg?1 at 15‐ to 30‐cm depth) and kaolinitic (194 mg K kg?1 at 0‐ to 15‐cm depth and 167 mg K kg?1 at 15‐ to 30‐cm depth) soils. Surface soils exhibited larger cumulative K release in smectitic and illitic soils, whereas subsurface soils had larger K release in kaolinitic soils. Among the extractants, 0.01 M citric acid extracted a larger amount of nonexchangeable K followed by 0.01 M CaCl2 and 0.01 M HCl. The efficiency of citric acid extractant was greater in illitic soils than in smectitic and kaolinitic soils. Release kinetics of nonexchangeable K conformed fairly well to parabolic and first‐order kinetic models. The curve pattern of parabolic diffusion model suggested diffusion controlled kinetics in all the soils, with a characteristic initial fast rate up to 7 h followed by a slower rate. Greater nonexchangeable K release rates in smectitic soils, calculated from the first‐order equation (b=91.13×10?4 h?1), suggested that the layer edge and wedge zones and swelling nature of clay facilitated the easier exchange. In contrast to smectitic soils, higher release rate constants obtained from parabolic diffusion equation (b=39.23×10?3 h?1) in illitic soils revealed that the low amount of exchangeable K on clay surface and larger amount of interlayer K allowed greater diffusion gradients, thus justifying the better fit of first‐order kinetic equation in smectitic soils and parabolic diffusion equation in illitic soils.  相似文献   

18.
The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu2+ and Pb2+) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb2+ than for Cu2+ (e.g. at pH = 5 HA gave 0·188 mmol Cu2+ g?1 and 0·564 mmol Pb2+ g?1: peat gave 0·111 mmol Cu2+ g?1 and 0·391 mmol Pb2+ g?1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K1) for Cu2+ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K1= 2·63, and peat gave log K1= 4·47 for Cu2+). The values for Pb2+ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K1= 3·03 and peat gave log K1= 3·00 for Pb2+). In the peat, Cu2+ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb2+ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.  相似文献   

19.
Abstract

To investigate the activity of free cadmium (Cd2+), copper (Cu2+), lead (Pb2+), and zinc (Zn2+) ions and analyze their dependence on pH and other soil properties, ten contaminated soils were sampled and analyzed for total contents of Cd, Cu, Pb, and Zn (CdT, CuT, PbT, and ZnT, respectively), 0.43 MHNO3‐extractable Cd, Cu, Pb, and Zn (CdN, CuN, PbN, and ZnN, respectively), pH, dissolved organic matter (DOC), cation exchange capacity (CEC), ammonium oxalate extractable aluminum (Al) and iron (Fe), and dissolved calcium [Ca2+]. The activity of free Pb2+, Cd2+, Cu2+, and Zn2+ ions in soil solutions was determined using Donnan equilibrium/graphite furnace atomic absorption (DE/GFAA). The solubility of Cd in soils varied from 0.16 to 0.94 μg L‐1, Cu from 3.43 to 7.42 μg L‐1, Pb from 1.23 to 5.8 μg L‐1, and Zn from 24.5 to 34.3 μg L‐. In saturation soil extracts, the activity of free Cd2+ ions constituted 42 to 82% of the dissolved fraction, for Cu2+the range was 0.1 to 7.8%, for Pb2+ 0.1 to 5.1% and for Zn2+2 to 72%. The principal species of Cd, Cu, Pb, and Zn in the soil solution is free metal ions and hydrolyzed ions. Soil pH displayed a pronounced effect on the activity of free Cd2+, Cu2t, Pb2+, and Zn2+ ions.  相似文献   

20.
随着经济和社会的发展,土壤重金属污染对粮食安全及人类的身体健康构成了巨大的威胁,而目前对于土壤重金属污染的治理主要以植物修复为主。为了寻找适宜修复Cu、Pb复合污染土壤的牧草,采用盆栽试验法,将试验的植物设置9组处理:1组对照组(CK),不添加任何重金属盐;4组单一污染,即单一Cu低(Cu1,200 mg×kg-1)、高浓度(Cu2 400 mg×kg-1),单一Pb低(Pb1 300 mg×kg-1)、高浓度(Pb2 800 mg×kg-1);4组Cu、Pb复合污染(Cu1Pb1、Cu1Pb2、Cu2Pb1、Cu_2Pb_2)。通过比较紫花苜蓿(Medicago sativa)、黑麦草(Lolium perenne)、狼尾草(Pennisetum alopecuroides)的适应能力和富集特征,研究了这3种常见牧草植物对受Cu、Pb复合污染土壤的修复效果。结果表明:1)紫花苜蓿地上部和根部生物量均在Pb1处理组时最大,显著高于其他处理组;黑麦草地上部生物量在Cu1Pb1处理组最大,根部生物量在Pb1处理组最大;狼尾草地上部生物量在Cu_2Pb_2处理组最大,根部生物量在Cu2处理组最大。2)Cu单一污染下,狼尾草抗性系数最大;Pb单一污染下,紫花苜蓿抗性系数最大;Cu-Pb复合污染下,狼尾草的抗性系数较大。高浓度Cu处理组3种牧草植物的地上部生物量、根部生物量和抗性系数均呈现:狼尾草黑麦草紫花苜蓿,且狼尾草显著大于黑麦草和紫花苜蓿。3)种植3种牧草植物后,土壤重金属Cu、Pb含量均有所降低。在一定浓度下,土壤Cu-Pb重金属间会相互促进对方在牧草植物中的吸收。4)3种牧草中紫花苜蓿地上部对Cu的富集系数在Cu_2Pb_2处理组最大,达1.61;黑麦草根部对Cu的富集系数在Cu_2Pb_2处理组最大,达3.80;3种牧草地上部和根部对Pb的富集系数只在黑麦草根部的Cu1Pb1处理组时大于1,达1.46。5)黑麦草对Pb的吸收能力较强,且主要积累在根系;紫花苜蓿对Cu-Pb复合污染综合修复效果最好。紫花苜蓿和黑麦草分别在Cu-Pb复合污染和Pb单一污染土壤中对Pb的转运系数大于1,分别为2.72和2.06,反映其对土壤中的Pb具有富集潜力。综合表明,黑麦草对重金属Pb具有较强的耐性,在Pb单一污染土壤的植物修复及尾矿废弃地的植被重建中,可优先作为选择的材料;紫花苜蓿对重金属Cu、Pb均具有较强的耐性,在重金属Cu单一或Cu-Pb复合污染土壤的植物修复及尾矿废弃地的植被重建中,可优先作为选择的材料。  相似文献   

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