里氏木霉FS10-C对伴矿景天吸取修复镉污染土壤的强化作用

为提高伴矿景天对Cd污染土壤的修复效果,通过盆栽模拟试验,研究了木霉(Trichoderma)对伴矿景天生和Cd修复效率的影响.结果表明:Cd的加入抑制了伴矿景天的生长;伴矿景天在Cd含量为5 mg/kg模拟污染土壤中对Cd提取效率最高.在不同Cd污染水平下,里氏木霉(T.reesei)FS10-C使伴矿景天地上部干重比对照组增加了17.1％ ～42.5％,显著提高伴矿景天地上部对Cd的积累;在15 mg/kg Cd处理下,里氏木霉FS10-C处理组植物地上部Cd积累量高于对照组46.2％但对于土壤中NH4OAc提取态Cd含量影响不显著.说明里氏木霉FS10-C能提高伴矿景天对Cd的抗性,增加其生物量,从提高其修复效率.因此,里氏木霉FS10-C具有强化伴矿景天修复Cd污染土壤的应用潜力.     

柠檬酸活化协同伴矿景天-玉米套作对镉轻微污染土壤的修复效果

伴矿景天-玉米套作是一种原位、绿色、边生产、边修复Cd污染土壤的有效方式,土壤中添加柠檬酸可有效提高伴矿景天的修复效率。该研究通过田间微区试验,探究了柠檬酸不同添加方式协同伴矿景天-玉米套作模式对Cd轻微污染稻田土壤修复机理及修复效果。结果表明：1）同一种植模式,添加柠檬酸可提高土壤Cd有效性,显著提高伴矿景天的修复效率;5次添加柠檬酸,伴矿景天单作时修复效率提高了2.09%,套作时提高了10.54%。2）柠檬酸添加量相同时,套种与伴矿景天单种相比,修复效率提高了3.42%～4.27%,同时减少了玉米对土壤Cd的吸收。3）5次添加柠檬酸协同伴矿景天-玉米套作,伴矿景天Cd移除量可达18.59 mg/m2,该处理伴矿景天对轻微Cd污染土壤的修复效果最佳。因此,柠檬酸协同伴矿景天-玉米套作的联合修复模式可强化伴矿景天修复效率,可运用于Cd轻微污染稻田土壤的修复,并可实现边修复边生产。     

铜对伴矿景天生长及锌镉吸收性的影响

利用植物生长室水培试验和温室土培盆栽试验相结合,研究了Cu对Zn、Cd超积累植物伴矿景天生长及Zn、Cd吸收性的影响。水培试验结果显示,0.31～50μmol/L Cu处理14天对伴矿景天生长及对Zn、Cd吸收性没有显著影响;但100μmol/L Cu处理显著抑制植物生长,降低地上部Zn、Cd及根中Cd浓度,对根中Zn浓度变化没有显著影响。盆栽试验结果发现,在土壤Cu仅为3.61 mg/kg时伴矿景天生长不良,外加Cu显著促进其生长并随Cu浓度升高效应增加;但施用3 mmol/kgEDDS和再次外加250 mg/kg Cu处理使伴矿景天因体内Cu积累量过高而导致明显毒害,地上部Cu最高达1 068 mg/kg。可见低量Cu处理可促进伴矿景天生长,利于植物对土壤Zn、Cd的吸取修复,但土壤中Cu浓度过高将抑制Zn、Cd超积累植物的生长,降低其Zn、Cd吸收能力,在利用该Zn、Cd超积累植物修复高Cu的Zn和Cd污染土壤时应采取适当措施降低Cu毒害效应。     

Remediation of vanadium contaminated soil by nano-hydroxyapatite

Purpose

Vanadium (V) contamination in soil can cause diverse damage to soil ecosystem and has attracted research interests in exploring soil V stabilization methods, but only a few materials were proposed and studied. Here, a pot experiment was firstly conducted to estimate the efficiency of nano-hydroxyapatite (n-HAP) in stabilizing V in soil. To verify the impact of n-HAP on soil V bioavailability and phytotoxicity, cabbages (Brassica chinensis L.) were grown in V-spiked soils after n-HAP amendment.

Materials and methods

Soils were sampled from a farmland in China, and the n-HAP was prepared in the laboratory. In each pot of soil spiked with 0, 75, 150, 300, and 600 mg/kg V, 2% n-HAP was amended for 30 days, while soils without n-HAP amendment were set as controls. The stabilization effect of n-HAP on V in soil was estimated by the water-extractable and bioavailable V concentrations in soils. Cabbages were grown in pots subsequently. The V(V/IV) concentrations in cabbage leaves and roots, the organic bound V concentrations in cabbage roots, and the chlorophyll concentrations in leaves were determined. Bioconcentration factor and translocation factor were calculated. The composition of organic bound V in leaf was characterized by fluorescence excitation–emission matrix.

Results and discussion

In soils spiked with 150 mg/kg V, n-HAP amendment yielded the highest stabilization rates of 51.0% and 42.4% for water-extractable and bioavailable V, respectively. In 75, 150, and 300 mg/kg V-spiked soil, the plant weight, plant height, and root length of cabbage after 60-day growing decreased 54.6%/89.6%, 30.9%/45.5%, and 41.5%/51.4% in groups with/without n-HAP, respectively. Cabbage leaf chlorophyll concentrations descend firstly then ascend with rising soil V concentration. Leaf V speciation analysis revealed that less leaf V was reduced to V(IV) in groups amended with n-HAP than groups without n-HAP amendment. In 150 and 300 mg/kg V-spiked soil, n-HAP effectively reduced the V content and the V bioconcentration factor of cabbage root. Tyrosine-like and humic acid-like analogues composed the principal part of V complex.

Conclusions

In general, n-HAP amendments are potential to decrease the mobility of V in soils, as well as inhibit the bioavailability and phytotoxicity of V to cabbage. In V-spiked soils, n-HAP amendment can alleviate the toxicity of V to the cabbage. Overall, 2% n-HAP is efficient for the amendment of slight V-polluted (150–300 mg/kg) soils to alleviate the soil V stress to cabbage.

     

Effects of multiple heavy metal contamination and repeated phytoextraction by Sedum plumbizincicola on soil microbial properties

The threat of heavy metal contamination to food and human health in south and east China has become a public concern as industrial development continues. The aims of this study were to investigate the influence of repeated phytoextraction over a two-year period by successive crops of the Zn and Cd hyperaccumulator Sedum plumbizincicola on multiple metal contaminated soils and to assess recovery of soil quality. Total and NH₄OAc-extractable Zn and Cd concentrations were significantly reduced in planted soils compared to unplanted soils. Microbial biomass C (C_mic), basal respiration and microbial quotient (qM) were significantly and positively correlated and soil metabolic quotient (qCO₂) was negatively correlated with heavy metal concentrations in unplanted soils (P < 0.05). However, C_mic, basal respiration and qM values increased significantly after phytoremediation by five crops over two years compared to unplanted soil. Urease, β-glucosidase, neutral phosphatase and arylsulfatase activities also increased significantly with decreasing heavy metal contents and hydrolase activity was enhanced in planted soil (P < 0.05) compared to the unplanted control. The data indicate the capacity of S. plumbizincicola to extract Zn and Cd from contaminated soil and also that phytoremediation had beneficial effects on soil microbial and hydrolase activities, with the metal phytoextraction procedure restoring soil quality.     

氯代有机化合物污染土壤的修复技术

大多数氯代有机化合物具有较高的沉积物－水分配系数，故在环境系统中其主要存在于土壤和沉积物中。因此土壤中氯代有机化合物的修复技术研究对于减少其在环境中的存量是十分重要的。氯代有机化合物污染土壤的修复技术主要可分为分离浓缩技术、转化分解技术和植物修复技术三大类。本文就各技术中的具体类型以及不同技术之间的结合作用作了系统概述。     

表面活性剂与EDTA对紫色土镉的化学行为影响

Elemental composition and geochemical characteristics of iron-manganese nodules from nine main soils in China were studied by chemical and multivariate statistical analyses to better understand the reactions and functions of ironmanganese nodules in soils and sediment. Compared to the corresponding soils, Mn, Ba, Cd, Co and Pb had strong accumulation, Ni had moderate accumulation, while Ca, Cu, Fe, Na, P, Sr and Zn accumulated to a minor degree in the iron-manganese nodules. In contrast, Si, Al, K, Mg and Ti were reduced in the iron-manganese nodules. The contents of Ba, Cd, Co, Cu, Ni, Pb and Zn were positively and significantly correlated with that of MnO2 in the iron-manganese nodules, while the contents of Cr, Cu, Ni, Pb and Zn were positively and significantly correlated with that of Fe2O3 in soils. Based on a principle component analysis, the elements of iron-manganese nodules were divided into four groups： 1） Mn, Ba, Cd, Co, Cu, Li, Ni, Pb and Zn that were associated with Mn oxides, 2） Fe, Cr and P that were associated with Fe oxides, 3） Si, K, and Mg that were included in the elemental composition of phyllosilicate, and 4） Ca, Na, Al and Ti that existed in todorokite, birnessite, lithiophorite and phyllosilicate. It was suggested that accumulation, mineralization and specific adsorption were involved in the formation processes of soil iron-manganese nodules.     

Phospholipid fatty acid composition of a 2,4,6-trinitrotolune contaminated soil and an uncontaminated soil as affected by a humification remediation process

Analysis of phospholipid fatty acids (PLFAs) was performed to investigate effects of 2,4,6-trinitrotoluene (TNT) contamination and soil remediation on microbial biomass and community structure. A TNT-contaminated and an uncontaminated soil from a former ammunition plant were analysed before and after a humification/remediation process. TNT contamination reduced microbial biomass but indicated only minor differences in PLFA composition between the contaminated and uncontaminated soils. The humification process increased microbial biomass and altered soil PLFA patterns to a larger degree than did TNT contamination.     

水分特征对伴矿景天生长和重金属吸收性的影响

利用盆栽试验研究了水分特征对伴矿景天生长和重金属吸收性的影响.结果表明:在70% 土壤最大田间持水量(70%WHC)处理下,伴矿景天生长最好,其地上部鲜重显著高于其他处理;70%WHC处理伴矿景天对重金属吸收能力最强,其茎中Zn的浓度显著高于其他处理,茎中Cd的浓度分别比35%WHC、100%WHC、淹水处理高27.1%、29.0%、63.1%;叶中的Zn浓度表现出与茎中相同趋势,叶中Cd的浓度与茎中不同,以100%WHC处理最高.70%WHC处理下,植物提取Zn、Cd的效率最高,其修复效率均显著高于其他处理.这些结果表明,土壤水分状况在土壤重金属污染伴矿景天植物吸取修复中起着重要作用.     

过碳酰胺对土壤中非离子表面活性剂的修复研究

过碳酰胺是一种新型精细化工品,也是一种新型N肥,其应用和开发在国外已得到广泛的研究,而在我国还刚刚起步.为考察过碳酰胺作为一种N肥去除土壤中有机污染物的作用和潜力,将修复与施肥结合,为过碳酰胺应用于环境污染修复提供新的理论依据,特进行了本研究.本文采用室内土培试验等手段,研究了1种酸性土壤中施入过碳酰胺后对2种非离子表面活性剂TritonX-100和Tween80的降解效果.试验结果表明:过碳酰胺对2种非离子表面活性剂都有明显的降解效果,降解速度均是在第2周时较快,此后.随着降解时间的延长,降解速率逐渐下降.8周后1000mg/kg Tween80的残留浓度仅有195.46mg/kg土,降解率高达80%以上.5 mmol/kg的过碳酰胺降解2周后已有明显降解效果,但继续增加过碳酰胺浓度.其降解效果并非相应增加.     

Kinetics of soil phosphate desorption as affected by citric acid

Citrate can accumulate in the rhizosphere of phosphate (P) deficient plants. Therefore, P desorption was investigated in relation to citrate concentrations applied in a single or sequential mode to a Luvisol and a Podzol. Cumulative P desorption increased up to 20 times that of the control, the absolute increase being higher in the Podzol. The rate of P release was closely related to the rate of Fe+Al release indicating that desorption originated mainly from Fe/Al associated P. The mode of citrate loading affected the P desorption in an ambiguous manner. P-diffusion coefficients were calculated from the desorption data. The coefficients strongly increased with citrate loading, the increase being more pronounced in the Podzol.     

Regulation of amino acid biodegradation in soil as affected by depth

Dissolved organic nitrogen (DON) and in particular free amino acids represent a key pool in the terrestrial soil C and N cycle. The factors controlling the rate of turnover of this pool in soil, however, remain poorly understood. We investigated the factors regulating the rate of amino acid turnover at different depths (up to 1.2 m) in five low-input, acid soil profiles. Within the root zone (0–60 cm), amino acids constituted 8% of the DON and represented only a small fraction of plant available N. In all the soil profiles, the rate of amino acid mineralisation decreased progressively with depth. The average half-life of the exogenously added amino acids in the soil was 5.8 h in topsoils (0–10 cm), falling to 20 h at a depth of 50 cm and to 33 h at 100 cm. Generally, the rate of amino acid mineralisation correlated positively with total soil C and N, soil microbial activity (basal soil respiration rate) and soil content. The relatively rapid rates of microbial amino acid assimilation in subsoils below the root zone (>60 cm) indicate that long-term transport of amino acids (e.g. from soil to freshwaters) will be low. Based upon the C-to-N ratio of the amino acid substrate and the microbial C assimilation efficiency, we estimate that approximately 40–60% of the amino acid-N will be excreted as . In conclusion, the rapid rate of free amino acid turnover and their low concentration in soil solution indicate that the formation of inorganic N ( and ) in soil is limited primarily by the rate of free amino acid appearance in soil and not by the rate of amino acid mineralisation.     

漆酶不同施用方法对土壤DDT污染修复的研究

该文从投加量、分次投加和灭菌等方面,研究了漆酶不同施用方法对其修复土壤DDT污染效果的影响.研究结果表明,土壤中DDT各组分(P,P'-DDE除外)及DDT总量(DDTs)的降解率均随着漆酶投加量的增加而显著提高,在投加量为每克土加酶6U时DDTs的降解率达到50.63%:漆酶两次投加对土壤中DDT各组分及总量的降解率均显著高于一次投加,DDTs的降解率提高11.4%;漆酶处理对于非灭菌土壤和灭菌土壤中DDT总量的降解率几乎相当,但各组分则有显著差异,其中P,P'-DDE、O,P'-DDT和P,P'-DDD在非灭菌土壤中的降解率低于灭菌土壤,而P,P'-DDT则相反.     

Remediation of a soil contaminated with heavy metals by immobilizing compounds

The labile fraction of heavy metals (HM) in soils is the most important for toxicity for plants and microorganisms. Thus, it is crucial to reduce this fraction in contaminated soils to decrease the negative effect of HM. In a greenhouse experiment, the effects of several additives on the labile fractions of Zn, Cd, Cu, Ni, and Pb were investigated in a soil contaminated during long‐term sewage‐sludge application. The accumulation of HM was studied in the aboveground biomass of wheat (Triticum aestivum L.). The additives used were the clay minerals Na‐bentonite, Ca‐bentonite, and zeolite; the Fe oxides hematite and goethite; the phosphate fertilizers superphosphate and Novaphos. Wheat was planted three times during 5 months, allowed to grow for 7 w, and harvested. Dry matter and HM content of shoots were determined after each harvest. Soil samples were taken after the first and third harvest, and the NH₄NO₃‐extractable HM contents were determined. After the addition of 2% Na‐bentonite as well as 2% Ca‐bentonite, a strong reduction of the labile HM soil fraction and shoot HM concentration was observed. At the end of the experiment, the labile fraction was reduced due to the addition of Na‐bentonite and Ca‐bentonite by 24% and 31% for Zn, by 37% and 36% for Cd, by 41% and 43% for Cu, by 54% and 61% for Ni, and by 48% and 41% for Pb, respectively. Furthermore, the shoot HM concentrations with the exception of Zn were reduced below the phytotoxicity range. Accordingly, the shoot dry‐matter production was significantly increased. The addition of phosphate fertilizers (notably Novaphos) strongly reduced the bioavailability of Pb for wheat plants. By addition of 0.05% Novaphos, the labile fraction and the shoot concentration of Pb were lowered by 39% and 64%, respectively. However, the addition of Fe oxides and zeolite resulted only in a small reduction in HM bioavailability to wheat plants. Among the studied additives, Na‐bentonite and Ca‐bentonite have the most promising potential to reduce the bioavailability for the studied HM.     

Remediation of an electroplating contaminated soil by EDTA flushing: chromium release and soil dissolution

Purpose

Remediation of soils contaminated with Cr (as Cr(III) complexes/precipitates and/or Cr(VI) oxyanion) and cationic metals (Cu, Ni, Zn, and Pb) by ethylenediaminetetraacetate (EDTA) flushing has been challenging and rarely investigated. This study aimed to evaluate the efficiency of EDTA flushing for metal extraction of soil from an electroplating site, with a specific focus on chromium release and soil dissolution.

Materials and methods

Column flushing tests were performed on a sandy soil contaminated by electroplating activities in the field. Three EDTA concentrations (5, 10, and 20 mM) and flow interruptions were employed to investigate the operation of EDTA flushing.

Results and discussion

Results demonstrated that Cr, Cu, and Ni were continuously released along with dissolution of Fe, Al, Mg, and Mn throughout the entire flushing process (up to 600 pore volumes), whereas Zn and Pb removal primarily occurred in the first 50–200 pore volumes. By comparing the Cr and Fe release patterns, the observed Cr release by EDTA flushing possibly resulted from a combination of dissolution of Fe oxides, dissolution of metal–chromate precipitates, and ligand competition for the surface sites (substitution reaction). The latter two mechanisms appeared to be more influential at the early stage. It was also revealed that soil dissolution was predominant, and metal extraction became inefficient at the later stage of flushing, especially with the concentrated EDTA solution. On the other hand, when the flushing process was temporarily paused (i.e., flow interruptions), Cr, Cu, Ni, and Zn concentrations elevated, whereas Pb levels in the effluent decreased, indicating the significance of rate-limited metal exchange of newly formed metal–EDTA complexes.

Conclusions

In consideration of EDTA utilization efficiency and potential ecological risks, diluted EDTA solution is recommended for field applications.     

腐殖酸对磷在石灰性土壤中迁移的影响

When humic acid (HA) and phosphorus (P) fertilizer are simultaneously applied to soil, HA may affect the movement of P. A laboratory incubation experiment was conducted to quantify the effects of a commercial HA product co-applied with monocalcium phosphate (MCP) on the distance of P movement and the concentration of P in various forms at different distances from the P fertilizer application site in a calcareous soil from northern China. Fertilizer MCP (at a rate equivalent to 26.6 kg P ha-1 ) was applied alone or in combination with HA (at 254.8 kg HA ha-1 ) to the surface of soil packed in cylinders (150 mm high and 50 mm internal diameter), and then incubated at 320 g kg-1 moisture content for 7 and 28 d periods. Extraction and analysis of each 2 mm soil layer in columns showed that the addition of HA to MCP increased the distance of P movement and the concentrations of water-extractable P, acid-extractable P and Olsen P in soil. The addition of HA to MCP could enhance P availability by increasing the distance of P movement and the concentration of extractable P in soil surrounding the P fertilizer.     

Variations of soil phosphorus accumulation in Nanjing,China as affected by urban development

Human activities can affect the biogeochemical cycling of phosphorus substantially. However, the relationship between P accumulation and urban development process is largely unknown. This study investigated the influence of urban development on the P accumulation in urban and suburban soils, using Nanjing (China) as a case. Based on its urban development history, Nanjing was divided into suburban and urban area, and the urban area was subdivided into urban north and urban south. Soil total P (TP) and available P (AP) of 578 samples from 68 pedons at different locations were measured. Thickness‐weighted mean P content of each pedon (P_w), P content of the surface soil layer (P_s), the highest P content of each pedon (P_h), and the lowest P content (P_l) of each pedon were selected as statistical indices. Compared with the background value, urban and suburban soils were enriched in P. The highest TP content was up to 11.14 g P kg^–1, and the highest AP content was up to 360 mg P kg^–1. However, analysis of variance (ANOVA) and multiple comparisons of P_w, P_s, P_h, P_l showed that urban south with longest residential history had the highest TP_w, TP_s TP_h, and AP_w, AP_l contents, and urbanizing suburban had the lowest TP_w and AP_w, AP_l contents. For both APs and AP_h, there was no significant difference between suburban and urban area. However, significant differences between urban south and urban north were observed. The results demonstrated that urban development process, including population quantity and level of urban infrastructure, could influence soil P accumulation and distribution in urban environment. A more detailed assessment is required to avoid the potential secondary eutrophication caused by excess P release from those anthropogenic high‐P soils.     

Characterization of soil profiles in a landscape affected by long-term tillage

Soil movement by tillage redistributes soil within the profile and throughout the landscape, resulting in soil removal from convex slope positions and soil accumulation in concave slope positions. Previous investigations of the spatial variability in surface soil properties and crop yield in a glacial till landscape in west central Minnesota indicated that wheat (Triticum aestivum) yields were decreased in upper hillslope positions affected by high soil erosion loss. In the present study, soil cores were collected and characterized to indicate the effects of long-term intensive tillage on soil properties as a function of depth and tillage erosion. This study provides quantitative measures of the chemical and physical properties of soil profiles in a landscape subject to prolonged tillage erosion, and compares the properties of soil profiles in areas of differing rates of tillage erosion and an uncultivated hillslope. These comparisons emphasize the influence of soil translocation within the landscape by tillage on soil profile characteristics. Soil profiles in areas subject to soil loss by tillage erosion >20 Mg ha⁻¹ year⁻¹ were characterized by truncated profiles, a shallow depth to the C horizon (mean upper boundary 75 cm from the soil surface), a calcic subsoil and a tilled layer containing 19 g kg⁻¹ of inorganic carbon. In contrast, profiles in areas of soil accumulation by tillage >10 Mg ha⁻¹ year⁻¹ exhibited thick sola with low inorganic carbon content (mean 3 g kg⁻¹) and a large depth to the C horizon (usually >1.5 m below the soil surface). When compared to areas of soil accumulation, organic carbon, total nitrogen and Olsen-extractable phosphorus contents measured lower, whereas inorganic carbon content, pH and soil strength measured higher throughout the profile in eroded landscape positions because of the reduced soil organic matter content and the influence of calcic subsoil material. The mean surface soil organic carbon and total nitrogen contents in cultivated areas (regardless of erosion status) were less than half that measured in an uncultivated area, indicating that intensive tillage and cropping has significantly depleted the surface soil organic matter in this landscape. Prolonged intensive tillage and cropping at this site has effectively removed at least 20 cm of soil from the upper hillslope positions.     

Effect of soil application of cadmium contaminated lime on soil cadmium distribution and cadmium concentration in strawberry leaves and fruit

Heavy metal environmental pollution which occurs as a result of lime contaminated with cadmium (Cd) poses a potential health hazard. This investigation was undertaken to study uptake of Cd by strawberry plants grown in soil amended with three different sources and two different rates of industry waste lime containing 3.4, 14.3, and 60.0 mg Cd/kg, respectively. The effects of Cd applied to the soil were investigated, including its distribution in the soil and effect on Cd concentration in strawberry cv. Senga Sengana (Fragaria anassa) leaves and fruit in response to soil organic matter content and lime rates. Cadmium accumulated mainly in the plough layer, increasing from 0.170 mg Cd/kg (background level) to a maximum of 1.2 mg Cd/kg. Fruit had very high, hazardous Cd concentrations regardless of its content in the soil. This indicates that Cd was easily taken up by strawberry plants and accumulated in upper plant parts, including the fruit. Soil Cd content had no effect on concentration of this element in strawberry fruit. However, plant Cd uptake and fruit concentration was increased in acid soils even when soil Cd concentration was low.     

Metal removal from and microbial property improvement of a multiple heavy metals contaminated soil by phytoextraction with a cadmium hyperaccumulator Sedum alfredii H.

Purpose

Effects of phytoextraction by Sedum alfredii H., a native cadmium hyperaccumulator, on metal removal from and microbial property improvement of a multiple heavy metals contaminated soil were studied under greenhouse conditions.

Materials and methods

A rhizobox experiment with an ancient silver-mining ecotype of S. alfredii natively growing in Zhejiang Province, China, was conducted for remediation of a multiple heavy metals contaminated soil. The rhizobox was designed combining the root-shaking method for the separation of rhizospheric vs near-rhizospheric soils and prestratifying method for separation of sublayers rhizospheric soils (0–10 mm from the root) and bulk soil (>10 mm from the root). Soil and plant samplings were carried out after 3 and 6 months of plant growth.

Results and discussion

Cadmium (Cd), zinc (Zn), and lead (Pb) concentrations in shoots were 440.6, 11,893, and 91.2 mg kg^?1 after 6 months growth, and Cd, Zn, and Pb removed in the shoots were 0.862, 25.20, and 0.117 mg/plant. Microbial biomass C, basal respiration, urease, acid phosphatase, and invertase activities of the rhizospheric soils were significantly higher than that of unplanted soils after 6 months growth. Microbial biomass carbon (MBC) of 0–2 mm and basal respiration (BR) rate of 0–8 mm sublayer rhizospheric soils were significantly higher than that of bulk soil after 6 months growth. So were the three enzyme activities of 0–4 mm sublayer rhizospheric soils. BR rate and urease were significantly negatively correlated with soluble Cd, so were MBC, acid phosphatase, and intervase activities with soluble Zn, MBC, BR rate, and three enzyme activities with soluble Pb.

Conclusions

Harvesting shoots of S. alfredii could remove remarkable amounts of Cd, Zn, Pb, and lower water-soluble Cd, Zn, and Pb concentrations in the rhizospheric soils. MBC, BR rate, and enzyme activities of the metal polluted soil, especially the rhizospheric soils increased with phytoextraction process, which is attributed to the stimulation of soil microbes by planting as well as the decrease in soil-soluble metal concentration.