超积累植物东南景天根际土壤酶活性研究

通过野外调查和盆栽试验研究了超积累植物东南景天根际土壤酶活性变化及其与重金属有效态的关系。研究结果表明,在矿山土壤、重度污染土壤和轻度污染土壤上,种植超积累生态型东南景天后,根际土壤有效态Zn分别比非根际减少了14.3%,7.9%和47.4%,有效态Cd分别比非根际减少25.1%,21.9%和20%。在铅锌矿区,东南景天生长地段土壤蔗糖酶、酸性磷酸酶、脱氢酶活性高于其它植物生长地段。在矿山土壤和重度污染土壤中,超积累生态型东南景天根际土壤酶活性明显高于非根际土壤,同时也高于非超积累生态型根际土壤。Pb、Zn、Cd、Cu4种重金属对东南景天根际土壤脲酶、蔗糖酶、脱氢酶活性均有抑制作用,而Pb对磷酸酶有一定的刺激作用。东南景天根际土壤脱氢酶、酸性磷酸酶活性与重金属有效态含量呈极显著相关。     

施肥对I-107杨树人工林土壤根际效应的影响

 通过研究施用有机肥、化学肥料和生物菌肥对I-107杨树人工林根际和非根际土壤微生物数量和土壤酶活性的影响,分析土壤酶活性与土壤微生物数量的关系。研究结果表明:不同种类肥料使用后3个月,林地根际土壤和非根际土壤微生物总量均有显著增长,其中有机肥处理土壤微生物数量增长幅度最大,菌肥处理最小。施肥处理显著提高土壤脲酶、碱性磷酸酶、过氧化氢酶、过氧化物酶活性,但尿素和菌肥处理土壤多酚氧化酶活性降低。施用有机肥处理对土壤微生物和土壤酶根际效应值影响最明显,菌肥处理影响最小。尿素处理土壤pH值高于对照,有机肥和菌肥处理小于对照,但不同处理间土壤pH值的根际效应值差异性不明显。土壤微生物数量与土壤酶活性之间存在一定的相关性,其中:土壤脲酶活性与好气性纤维素分解菌之间、土壤碱性磷酸酶活性与氨化细菌、真菌、放线菌、亚硝酸细菌之间,土壤过氧化氢酶与好气性纤维素分解菌、真菌、放线菌之间相关性显著。     

Microbiological rates and enzyme activities as indicators of functionality in soils affected by the Aznalcóllar toxic spill

This study focused on the potential of using soil enzyme activities and general microbiological rates (respiration, N-mineralisation, nitrification) to evaluate the quality of soils affected by a pyrite mud spill which contained high concentrations of heavy metals. The quality of soils after restoration was estimated by comparing enzyme activities and general microbiological rates in three different types of experimental field plots: (i) non-polluted, (ii) polluted but restored, and (iii) polluted but un-restored soils. Non-polluted soils showed the highest levels of enzyme activity. Significant differences were detected for acid phosphatase, β-glucosidase and urease activities between all types of plots. However, arylsulfatase and alkaline phosphatase activities showed no significant differences between the restored plots and polluted but un-restored plots. Geometric mean statistics were used as an index of soil quality in terms of overall: (i) bioavailable heavy metal concentrations, (ii) assayed enzyme activities, and (iii) general microbiological rates, in order to compare plots differing in the degree of pyritic mud pollution. The results indicate that it is important to consider these three criteria in to estimate the soil quality of heavy-metal contaminated soils. Typically, enzyme activities were negatively correlated with bioavailable Cd, Cu and Zn concentrations, but positively with soil pH values. In contrast, pH values were negatively correlated with bioavailable concentrations of Cd, Cu and Zn. It is unclear if the generalised lower enzyme activities found in restored soils, compared to non-polluted soils, is promoted by pH or bioavailable heavy metals concentrations, or a combination of both.     

Phosphorus Speciation and Nutrient Stoichiometry in the Soil-Plant System During Primary Ecological Restoration of Copper Mine Tailings

The effects of plant vegetation on phosphorus(P) speciation, pH, total carbon concentration, total nitrogen concentration, and alkaline phosphatase activities were investigated to explore the P uptake strategy of plants in low-P soil and to determine the nutrient stoichiometric ratio changes in the rhizosphere of plants(Imperata cylindrica, Miscanthus floridulus, Zoysia sinica, Artemisia lavandulaefolia, Indigofera pseudotinctoria, and Conyza canadensis) which had grown for approximately 15 years in copper mine tailings, East China. The results showed that the average pH values in the rhizosphere decreased by 0.06–1.37 compared with those in the non-rhizosphere. The alkaline phosphatase activities of the rhizosphere were significantly higher than those in the non-rhizosphere.The mean concentrations of aluminum(Al)-and iron(Fe)-bound P and Ca_2-P(CaHPO_4) in the rhizosphere of all plants were 5.4% to 87.7%, 49.2% to 214.2%, and 86.6% to 147.6% higher than those in the non-rhizosphere, respectively. Except for Ca_8-P(Ca_8H_2(PO_4)_6)and Ca_(10)-P(Ca_(10)(PO_4)_6(OH)_2) in the rhizosphere, all kinds of inorganic P forms were negatively correlated with pH. Significant correlation was also observed among the concentrations of dominant forms of inorganic P, C, and N and alkaline phosphatase activities in the rhizosphere. Among the studied species, I. pseudotinctoria showed the most significant effect on enhancing soil available P concentration. The stoichiometric ratios of C:P and N:P were apparently higher in the rhizosphere than the non-rhizosphere, whereas these ratios were far below the ratios commonly observed in Chinese soils. These results indicated that the plant growth effectively affected P fractions possibly by changing pH, C and N concentrations, and alkaline phosphatase activity, in the rhizosphere in copper mine tailings.     

Additive effects of copper and zinc on cadmium toxicity on phosphatase activities and ATP content of soil as estimated by the ecological dose (ED50)

The ecological dose (ED₅₀) of Cd on alkaline and acid phosphatase activity and the ATP content of three contrasting forest soils was measured with or without Cu and Zn to assess the additive toxic effects of these two metals. Soils polluted with Cu and/or Zn were treated with increasing Cd concentrations to give the following metal combinations: Cd, Cd+Cu, Cd+Zn and Cd+Cu+Zn. Alkaline and acid phosphatase activities and ATP content of the three soils were analysed 4 h, 7 and 28 days after the metal additions. The ED₅₀ values were obtained by interpolating the enzyme activities or ATP data with a kinetic model and the goodness of fit was satisfactory.Generally, the ED₅₀ values of both acid and alkaline phosphatase activities for Cd were lower (higher toxicity) with than without Cu and Zn and the effect of Cu and Zn was particularly adverse when these two metals were both added to soils. The alkaline phosphatase was more sensitive in the acid and neutral soil whereas the acid phosphatase was more sensitive in the alkaline soil. Both phosphatase activities and the ATP content were more sensitive in the sandy than in the finer textured soils. The ATP content was less sensitive to the additive effects. Increasing toxicity was observed during the incubation.Analysis of 1 M NH₄NO₃-extractable Cd, Cu and Zn revealed that Cd competed with Zn for the adsorption sites but not with Cu. However, the lower ED₅₀ values for Cd of the two phosphatase activities and of the ATP content in the presence of heavy metal combinations could be not explained by the heavy metal solubility data. It is concluded that the ED₅₀ may be a sensitive tool for assessing additve toxic effects to soil biochemical parameters.     

Differences between soil solutions obtained from rhizosphere and non-rhizosphere soils by water displacement and soil centrifugation

Soil solution was obtained from potted rhizosphere or non-rhizosphere soils by water displacement or soil centrifugation. The pH of the displaced solutions was lower than that of bulk soils when solutions were obtained from non-rhizosphere soil, although it increased as plants grew. This increase probably reflected true changes in rhizosphere pH, generated by the uptake by plants of N0₃-N. In contrast, the pH of soil centrifugates was usually close to that of the bulk soils, implying that buffering by colloids had occurred during sampling. Concentrations of elements in solutions from non-rhizosphere soil were similar for both methods when soils were incubated at ambient pCO₂. However, when non-rhizosphere soils were incubated at elevated pCO₂, displacement solutions had lower pH values, and much larger concentrations of elements, compared to soil centrifugates. Comparison of mass flow of elements versus actual plant uptake showed that Ca and Mg accumulated, while K, Zn and Cd were depleted from the rhizosphere. Displacement solutions showed this accumulation or depletion of the elements more clearly than soil centrifugates. These differences were attributed to the fact that, at constant soil moisture, the rhizosphere developed mainly in larger pores, which were sampled by displacement. With centrifugation, a mixture of pore sizes was sampled, so that rhizosphere solution was only obtained when all of the soil had become rhizosphere. Soil centrifugates obtained after 22 days of growth also contained higher concentrations of organic carbon than displacement solutions, indicating contamination due to the disruption of roots and/or micro-organisms. We conclude that water displacement is suitable for sampling solution from light to medium textured rhizosphere or non-rhizosphere soils and that soil centrifugation is only of limited suitability.     

镉胁迫系统中土壤氮循环微生物活性随大豆生育期变化的动态效应研究

The potential influences of cadmium （Cd） on the biochemical processes of the soil nitrogen （N） cycle, along with the dynamics of ammonification, nitrification, and denitrification processes in the rhizosphere and non-rhizosphere （bulk soil）, respectively, were investigated in a Cd-stressed system during an entire soybean growing season. In terms of Cd pollution at the seedling stage, the ammonifying bacteria proved to be the most sensitive microorganisms, whereas the effects of Cd on denitrification were not obvious. Following the growth of soybeans, the influences of Cd on ammonification in the bulk soil were： toxic impacts at the seedling stage, stimulatory effects during the early flowering stage, and adaptation to the pollutant during the podding and ripening stages. Although nitrification and den itrification in the bulk soil decreased throughout the entire growth cycle, positive adaptation to Cd stress was observed during the ripening stage. Moreover, during the ripening stage, denitrification in the bulk soil under high Cd treatment （20 mg kg^-1） was even higher than that in the control, indicating a probable change in the ecology of the denitrifying microbes in the Cd-stressed system. Changes in the activity of microbes in the rhizosphere following plant growth were similar to those in the non-rhizosphere in Cd treatments; however, the tendency of change in the rhizosphere seemed to be more moderate. This suggested that there was some mitigation of Cd stress in the rhizosphere.     

Tebuconazole application decreases soil microbial biomass and activity

A short-term mesocosm experiment was conducted to ascertain the impact of tebuconazole on soil microbial communities. Tebuconazole was applied to soil samples with no previous pesticide history at three rates: 5, 50 and 500 mg kg⁻¹ DW soil. Soil sampling was carried out after 0, 7, 30, 60 and 90 days of incubation to determine tebuconazole concentration and microbial properties with potential as bioindicators of soil health [i.e., basal respiration, substrate-induced respiration, microbial biomass C, enzyme activities (urease, arylsulfatase, β-glucosidase, alkaline phosphatase, dehydrogenase), nitrification rate, and functional community profiling]. Tebuconazole degradation was accurately described by a bi-exponential model (degradation half-lives varied from 9 to 263 days depending on the concentration tested). Basal respiration, substrate-induced respiration, microbial biomass C and enzyme activities were inhibited by tebuconazole. Nitrification rate was also inhibited but only during the first 30 days. Different functional community profiles were observed depending on the tebuconazole concentration used. It was concluded that tebuconazole application decreases soil microbial biomass and activity.     

Functional diversity as indicator of the recovery of soil health derived from Thlaspi caerulescens growth and metal phytoextraction

Continuous phytoextraction has lately drawn a lot of attention due to its potential for the remediation of metal polluted soils. Although when assessing the success of a phytoextraction process, up till now, emphasis has mostly been placed on metal removal, it is important to highlight that the ultimate objective of a phytoextraction process must be to restore soil health. Consequently, a short-term microcosm study was carried out to evaluate the capacity of an actively growing ecotype of the Zn and Cd hyperaccumulator Thlaspi caerulescens (Lanestosa ecotype) to phytoextract metals from soil and, above all, to assess the potential of soil functional diversity (through the determination of soil enzyme activities and community level physiological profiles) to both determine the toxic effect of metals on soil condition and to monitor the efficiency of a metal phytoextraction process. T. caerulescens plants grown in metal polluted soils showed a shoot metal concentration of 337 mg of Cd, 5670 mg of Zn and 76.6 mg of Pb per kg of dry weight tissue. Apart from confirming its great potential for Zn and Cd phytoextraction, the presence of T. caerulescens, as compared to the metal phytoextraction itself, had the major effect on soil biological parameters. Actually, in metal polluted soils, the presence of T. caerulescens led to a 154, 115, 140, 37 and 164% increase in the activity of β-glucosidase, arylsulphatase, acid phosphatase, alkaline phosphatase and urease, respectively. Metal pollution did not cause a clear inhibition of soil enzyme activities. Contrasting results were obtained with EcoPlates™ versus soil enzyme activities. Actually, the presence of metals led to significantly lower values of Shannon's index calculated from enzyme activities and non-significant higher values of this same index when calculated from EcoPlates™ data. It was concluded that biological indicators of soil health are valid tools to evaluate the success of a metal phytoextraction process.     

Changes of microbial properties in (near-) rhizosphere soils after phytoextraction by Sedum alfredii H: A rhizobox approach with an artificial Cd-contaminated soil

The ultimate goal of soil remediation is to restore soil health. Soil microbial parameters are considered to be effective indicators of soil health. The aim of this study was to determine the effects of phytoextraction on microbial properties through the measurement of soil microbial biomass carbon, soil basal respiration and enzyme activities. For this purpose, a pre-stratified rhizobox experiment was conducted with the Cd hyperaccumulator Sedum alfredii H. for phytoextraction Cd from an artificial contaminated soil (15.81 mg kg⁻¹) under greenhouse conditions. The plant and soil samples were collected after growing the plant for three and six months with three replications. The results indicated that the ecotype of S. alfredii H. originating from an ancient silver mining site was a Cd-hyperaccumulator as it showed high tolerance to Cd stress, the shoot Cd concentration were as high as 922.6 mg kg⁻¹ and 581.9 mg kg⁻¹ at the two samplings, and it also showed high BF (58.4 and 36.8 after 3 and 6 months growth), and TF (5.8 and 5.1 after 3 and 6 months growth). The amounts of Cd accumulated in the shoots of S. alfredii reached to an average of 1206 μg plant⁻¹ after 6 months growth. Basal respiration, invertase and acid phosphatase activities of the rhizosphere soil separated by the shaking method were significantly higher (P < 0.01) than that of the near-rhizosphere soil and the unplanted soil after 3 months growth, so were microbial biomass carbon, urease, invertase and acid phosphatase activities of the rhizosphere soil after 6 months growth. Acid phosphatase activity of the 0–2 mm sub-layer rhizosphere soil collected by the pre-stratified method after 3 months growth was significantly higher (P < 0.05) than that of other sub-layer rhizosphere soils and bulk soil, and so were microbial biomass carbon, basal respiration, urease, invertase and acid phosphatase activities of the 0–2 mm sub-layer rhizosphere soil after 6 months growth. It was concluded that phytoextraction by S. alfredii could improve soil microbial properties, especially in rhizosphere, and this plant poses a great potential for the remediation of Cd contaminated soil.     

The adverse effects of soil salinization on the growth of Trifolium alexandrinum L. and associated microbial and biochemical properties in a soil from Iran

The aim of this study was to determine the effects of increasing concentrations of salt solutions (including 0.12, 2, 6, and 10 dS m⁻¹) on the growth of berseem clover (Trifolium alexandrinum L.) and related soil microbial activity, biomass and enzyme activities. Results showed that the dry weights of root and shoot decreased with an increase in the concentrations of salt solutions. Soil salinization depressed the microbiological activities including soil respiration and enzyme activities. Substrate-induced respiration was consistently lower in salinized soils, whereas microbial biomass C did not vary among salinity levels. Higher metabolic quotients (qCO₂) and unaffected microbial biomass C at high EC values may indicate that salinity is a stressful factor, inducing either a shift in the microbial community with less catabolic activity or reduced efficiency of substrate utilization. Acid phosphatase and alkaline phosphatase activities decreased with increasing soil salinity. We found significant, positive correlations between the activities of phosphatase enzymes and plant's root mass, suggesting that any decrease in the activities of the two enzymes could be attributed to the reduced root biomass under saline conditions.     

Zn和ABT对玉米根系生长及根际磷酸酶活性和pH的影响

在石灰性土壤上,以田间根袋栽培方法,研究了Zn和生根粉4号(ABT)对玉米在5个生育期中根系生长和根际微生态环境的影响。结果表明,玉米根系生长随生育期呈"S"型分布,根长和根体积在生育后期呈下降趋势。Zn和ABT的应用促进了根系的生长,扩大了根系和土壤接触面积,减缓了后期根系衰老速度,并改善了根际微生态环境。玉米根际土壤pH低于非根际;根际土壤磷酸酶活性显著高于非根际。抽雄期,Zn、ABT和Zn+ABT处理土壤碱性磷酸酶活性较高。Zn和ABT的应用改善了玉米根际微生态环境,为有效利用土壤和肥料磷打下基础。     

Grasses, litter, and their interaction affect microbial biomass and soil enzyme activity

Plant effects on ecosystem processes are mediated through plant-microbial interactions belowground and soil enzyme assays are commonly used to directly relate microbial activity to ecosystem processes. Live plants influence microbial biomass and activity via differences in rhizosphere processes and detrital inputs. I utilized six grass species of varying litter chemistry in a factorial greenhouse experiment to evaluate the relative effect of live plants and detrital inputs on substrate-induced respiration (SIR, a measure of active microbial biomass), basal respiration, dissolved organic carbon (DOC), and the activities of β-glucosidase, β-glucosaminidase, and acid phosphatase. To minimize confounding variables, I used organic-free potting media, held soil moisture constant, and fertilized weekly. SIR and enzyme activities were 2-15 times greater in litter-addition than plant-addition treatments. Combining live plants with litter did not stimulate microbial biomass or activity above that in litter-only treatments, and β-glucosidase activity was significantly lower. Species-specific differences in litter N (%) and plant biomass were related to differences in β-glucosaminidase and acid phosphatase activity, respectively, but had no apparent effect on β-glucosidase, SIR, or basal respiration. DOC was negatively related to litter C:N, and positively related to plant biomass. Species identity and living plants were not as important as litter additions in stimulating microbial activity, suggesting that plant effects on soil enzymatic activity were driven primarily by detrital inputs, although the strength of litter effects may be moderated by the effect of growing plants.     

The combined effects of earthworms and arbuscular mycorrhizal fungi on microbial biomass and enzyme activities in a calcareous soil spiked with cadmium

Earthworms and arbuscular mycorrhizal fungi (AMF) are known to independently affect soil microbial and biochemical properties, in particular soil microbial biomass (SMB) and enzymes. However, less information is available about their interactive effects, particularly in soils contaminated with heavy metals such as cadmium (Cd). The amount of soil microbial biomass C (MBC), the rate of soil respiration (SRR) and the activities of urease and alkaline phosphatase (ALP) were measured in a calcareous soil artificially spiked with Cd (10 and 20 mg Cd kg⁻¹), inoculated with earthworm (Lumbricus rubellus L.), and AMF (Glomus intraradices and Glomus mosseae species) under maize (Zea mays L.) crop for 60 days. Results showed that the quantity of MBC, SRR and enzyme activities decreased with increasing Cd levels as a result of the elevated exchangeable Cd concentration. Earthworm addition increased soil exchangeable Cd levels, while AMF and their interaction with earthworms had no influence on this fraction of Cd. Earthworm activity resulted in no change in soil MBC, while inoculation with both AMF species significantly enhanced soil MBC contents. However, the presence of earthworms lowered soil MBC when inoculated with G. mosseae fungi, showing an interaction between the two organisms. Soil enzyme activities and SRR values tended to increase considerably with the inoculation of both earthworms and AMF. Nevertheless, earthworm activity did not affect ALP activity when inoculated with G. mosseae fungi, while the presence of earthworm enhanced urease activity only with G. intraradices species. The increases in enzyme activities and SRR were better ascribed to changes in soil organic carbon (OC), MBC and dissolved organic carbon (DOC) contents. In summary, results demonstrated that the influence of earthworms alone on Cd availability is more important than that of AMF in Cd-polluted soils; and that the interaction effects between these organisms on soil microorganism are much more important than on Cd availability. Thus, the presence of both earthworms and AMF could alleviate Cd effects on soil microbial life.     

黄土丘陵沟壑区典型林地土壤微生物、酶活性和养分特征

通过对陕西吴起县黄土沟壑区退耕还林地不同林分(沙棘、刺槐、油松、小叶杨)根际与非根际土壤养分、酶活性和微生物特征进行研究,比较4种典型林分及退耕草地“根际效应”及根际对养分的截留效应,评价根际效应对土壤特性产生不同改良效果,为黄土沟壑区退耕地人工林科学选择造林树种提供理论支持。研究表明:1根际与非根际土壤中有机质含量、有效磷含量、碱解氮含量和速效钾含量表现出显著差异,有机质、有效磷、速效钾含量均呈现明显的根际聚集现象。2根际土壤微生物数量和土壤酶活性总体高于非根际,仅油松样地中过氧化氢酶活性和小叶杨样地中脲酶活性根际低于非根际。3根际土壤中脲酶活性与细菌和真菌数量相关性达到显著水平,过氧化氢酶活性与真菌相关性达到显著水平;有机质含量与细菌、放线菌数量和脲酶活性相关性达到显著水平;碱解氮、有效磷含量均与细菌、真菌数量和脲酶活性相关性达到显著水平。在非根际土壤中,土壤养分含量与土壤微生物、土壤酶活性的相关性明显降低。4从土壤肥力综合水平看,根际土壤肥力水平综合得分总体上大于非根际土壤,其中根际土壤中沙棘小叶杨油松刺槐草地。沙棘能大幅度提高土壤肥力,具有较好的土壤改良效果。     

Influence of soil factors on the soil enzyme inhibition by Cd

A comparative study was conducted on the toxicity of Cd to alkaline phosphatase activity (ALP) and dehydrogenase activity (DHA) in 18 top soils with contrasting soil properties representative of 14 major soil types in China. Soil pH and carbonate content, soil organic matter, and cation exchange capacity (CEC) largely affected the Cd toxicity on two enzyme activities; with the soil pH having only minor effect on the median ecological dose values based on total Cd concentrations (ED_{50 T}). The values of ED_{50 T}/ED_{50 W} (based on water-soluble Cd content) of alkaline phosphatase and dehydrogenase were strongly influenced by pH and CEC contents, which explained up to 71% of the variation for alkaline phosphatase, 82% of the variation for dehydrogenase, and also were significantly correlated with the parameter K_F derived from Freundlich adsorption isotherms. This study suggests that the values of ED_{50 T}/ED_{50 W} could be useful to evaluate the buffer capacity of soils which protects soil enzymes from harmful effects of heavy metal.     

Spatial distribution of phosphatase activity associated with ectomycorrhizal plants is related to soil type

Several ectomycorrhizal fungi, including Hebeloma cylindrosporum, actively release large quantities of phosphatase enzymes into their growth medium. We fractionated the phosphatase activity of the ectomycorrhizal association between H. cylindrosporum and its host plant, Pinus pinaster, with the aim to quantify its spatial and temporal variation in response to contrasting soil phosphorus conditions. Seedlings were grown in mini-rhizoboxes and the phosphomonoesterase activity of rhizosphere soil, released by roots, surface-bound to roots or mycelium was determined spectrophotometrically with the p-nitrophenyl phosphate method or microscopically with the ELF-method as a function of culture time. We showed that acid phosphatase activity of the soil and the root increased with mycorrhizal association. We also observed that the phosphatase activity associated with ectomycorrhizal plants was related to soil type. All phosphatase fractions decreased over culture time, except the proportion of hyphae exhibiting phosphatase activity in the extramatrical mycelium, which increased over time. The specific fractions of phosphatase activity associated with the mycorrhizal plants were clearly related to the soil phosphorus type and content. Soils showed an increase in acid phosphomonoesterase activity with mycorrhizal association, supporting a role for this enzyme in the degradation of soil bound phosphorus. The gradually increasing proportion of hyphae in the extramatrical mycelium exhibiting alkaline phosphatase activity, particularly under low phosphorus conditions, indicates an induction of alkaline phosphatase activity by phosphorus limitation.     

土壤酶活性评价镉锌铅复合污染的可行性研究

模拟试验研究表明在Cd、Zn、Pb复合污染处理土壤中,过氧化氢酶、脲酶活性与碱性磷酸酶或转化酶活性可构成综合评价体系,反映土壤Cd、Zn、Pb污染含量以及土壤Cd-Zn、Zn-Pb复合污染效应,用其评价土壤Cd、Zn、Pb复合污染具有一定可行性。     

油葵和苦荬菜根际土壤中镉和锌的活化机制及修复潜力比较

  目的  研究油葵和苦荬菜根际土壤固、液相对镉（Cd）和锌（Zn）的活化机制,比较两种植物在轻、中度复合污染农田的修复潜力。  方法  通过大田试验种油葵和苦荬菜,测定成熟期土壤的pH值、有机酸、重金属总量及其生物有效性;测定土壤溶液中的溶解性有机质（DOM）、主要离子、水溶态重金属及其形态分布;测定植物各部位中重金属的浓度及形态,通过计算重金属在植物中的富集系数（BCF）和转运系数（TF）,比较两种植物对土壤重金属污染的修复潜力。  结果  油葵和苦荬菜根系分泌的低分子有机酸均使根际土壤pH值下降明显,显著低于非根际土壤（P < 0.05）;苦荬菜根际土中低分子有机酸及DOM的浓度显著高于油葵根际土（P < 0.05）。两种植物根际土壤溶液中的Cd以离子态和DOM结合态为主,Zn以离子态为主;两种植物根际土壤中有效态的Cd差异不显著,油葵根际有效态Zn显著高于苦荬菜;两种植物根际土壤的Zn和Cd有效态与土壤溶液中Cd-DOM和Zn-DOM呈显著相关。苦荬菜根对重金属的富集能力较强,但油葵地上部分能吸收转运更多的Cd和Zn,并在叶中以毒性较低的不溶性磷酸盐结合态和草酸结合态富集。  结论  两种植物根际分泌的有机酸可以增加根际土壤中的Cd-DOM和Zn-DOM的浓度,提高土壤中的Cd和Zn的有效性,苦荬菜根际对重金属有较强的活化能力,但油葵地上部分对Cd和Zn的吸收转运能力更强。两种植物都具有较强的土壤重金属修复潜力,但从经济角度出发,油葵更适合现阶段我国农田重金属污染的修复。     

Soil amendment with seed meals: Short term effects on soil respiration and biochemical properties

In the last decades, worldwide biofuel production increased up to 105 billion liters in 2010; in this year, the world's first biodiesel producer was the European Union. Biodiesel is produced from a variety of oils, mainly soybean, Brassicaceae and sunflower. One of the most important biodiesel production byproducts are seed meals. The most common use of seed meals is for animal nutrition, but another potential use is agricultural soil organic amendments. Soil biological and biochemical properties have been widely used as soil quality indicators, due to their quick response to changes in soil management. Although there are many studies on the effects of regular amendments on respiration and enzymatic activities of the soil, very few papers refer to the effect of seed meals. Therefore, the aim of this study was to investigate the short-term effect of seed meal amendment on soil respiration and enzymatic activities (alkaline phosphatase, dehydrogenase, fluorescein diacetate hydrolase, arylsulphatase and β-glucosidase). The two seed meals used were obtained from Brassica carinata (A.) Braun (Ethiopian mustard) and sunflower (Helianthus annuus L.). The study was carried out, from June 2007 to October 2007, at an experimental farm of CRA-ORT, Battipaglia, in the Sele River (Plain Salerno, Campania Region, Italy). The results of this study support an alternative use of seed meals as organic amendments. Generally, a significant positive response of enzymatic activities, evaluated in this study, to the addition of seed meals, indicates a beneficial effect on soil quality as regards microbial activity.