紫色土施用磷酸盐肥料对玉米铜毒害的缓解

A pot experiment was conducted to evaluate the effects of phosphorus fertilizer in inhibiting the copper toxicity to maize(Zea mays L.) in neutral purple soil. Results indicated that the growth of the shoot and roots of maize plant was obviously reduced by copper and the height and biomass were significantly negatively correlated to the application levels of copper (r = -0.899^**~-0.994^**) at no P and low P (100 mg kg^-1). However, the maize biomass was relatively increased and the high Cu (100 and 200 mg kg^-1) induced toxicity of maize was greatly alleviated in all treatments with medium P (300 mg kg^-1 ) and high P (500 mg kg^-1). To maintain the normal growth of maize plant (≥3.68 g pot^-1), the critical application rates of phosphorus fertilizer should be 160, 210, 300 and 500 mg P kg^-1 at 10, 50, 100 and 200 mg Cu kg^-1 levels of the soil, respectively. The increases in polyphenol oxidase and catalase activities in maize leaf and dehydrogenase activity in roots by phosphorus fertilizer were in the order of medium P>high P>low P>no P. Activities of polyphenol oxidase and catalase were significantly positively correlated to the application levels of copper (r =0.892^**~0.924^**), whereas that of dehydrogenase was just reverse (r = -0.966^**) at no P. Medium and high P repressed the influence of copper on activities of three enzymes. Phosphorus fertilizer reduced the copper concentrations of maize roots and leaf and the change ranges of the P/Cu ratio of maize roots and the P/Cu, N/Cu and K/Cu ratios of maize leaf. The three ratios of maize leaf were 256^**71.5, 2643^**839 and 1133^**440 at normal growth of maize plant, respectively. Soil available Cu could be markedly cut down by application of phosphorus fertilizer, especiallly at high phosphorus level.     

湿地土壤质量退化的模糊综合评价

Due to frequent soil Cd contamination and wide use of butachlor in China,there is a need to assess their combined toxicity to soil microorganisms.The combined effects of cadmium (Cd,10 mg kg^-1 soil) and herbicide butachlor (10,50,and 100 mg kg^-1 soil) on enzyme activities and microbial community structure in a paddy soil were assessed using the traditional enzyme assays and random amplified polymorphic DNA (RAPD) analysis.The results showed that urease and phosphatase activities were significantly reduced by high butachlor concentration (100 mg kg^-1 soil).When the concentrations of Cd and butachlor added were at a ratio of 1:10,urease and phosphatase activities were significantly decreased whereas enzyme activities were greatly improved at the ratio of 1:5,which indicated that the combined effects of Cd and butachlor on soil urease and phosphatase activities depended largely on their addition concentration ratios.Random amplified polymorphic DNA (RAPD) analysis showed loss of original bands and appearance of new bands when compared with the control soil.Random amplified polymorphic DNA fingerprints suggested substantial differences between the control and treated soil samples,with apparent changes in the number and size of amplified DNA fragments.The addition of high concentration butachlor and the combined impacts of Cd and butachlor significantly affected the diversity of the microbial community.RAPD analysis in conjunction with other biomarkers such as soil enzyme parameters would prove a powerful ecotoxicological tool.Further investigations should be carried out to understand the clear link between RAPD patterns and enzyme activity.     

根区限制及氮营养对杂交小麦生长的影响

To study the physiological effects of small root zone, plants of a hybrid wheat variety (Triticum aestivum L. cv. Meiyou 4) were grown in small pots (1 litre) or large pots (8 litre) with low nitrogen (50 mg kg^-1 soil) and high nitrogen (200 mg kg^-1 soil). Restricting root zone decreased dry weight of plants at the stages of stem elongation and flowering, compared to those of control plants grown in the large pots (P<0.01). Spraying of 6-benzylaminopurine (50 μmol L^-1) increased dry weight of plants and chlorophyll concentration in leaves. Restriction of root zone decreased the concentrations of total nitrogen, chlorophyll and soluble protein in the flag leaf and accelerated senescence of the leaves. Supply of high nitrogen delayed senescence of the flag leaf. The results suggested that the shortage of nutrients, especially nitrogen deficiency, was the primary reason for the decreased growth of plant in the treatment of root zone restriction.     

Impact of drilling waste pollution on land cover in a high subarctic forest-tundra zone

Global climate changes can lead to the destruction of the permafrost zone and contribute to the active transfer of pollutants to natural waters. This can be especially pronounced in the areas of oil and gas production in the Arctic. This study aimed to define the landscape components (i.e., groundwater, soil water, soil, and indicator plant species) of chemical pollution with metals, oil hydrocarbons, and polycyclic aromatic hydrocarbons, from the discharge of drill cuttings. Studies at two sites in the forest-tundra zone of Western Siberia (Russia) were carried out within two years of pollution. Pollutant migration was found in peaty-gley heavy loamy soils and iron-illuvial clayey podburs, but lateral migration of different pollutants did not exceed 200 m. Additionally, radial migration was practically absent owing to the high buffering capacity of the soil organic horizon and the upward flow of matter in the seasonal melt layer. The main indicators of drilling waste pollution were high concentrations of Sr, Ba, petroleum hydrocarbons, and Cl^- ions. At the waste disposal sites, the concentration of Ba and Sr in the soil water were 1 150 and 1 410 μg L^-1, respectively; in groundwater, they reached 721 and 2 360 μg L^-1, respectively. In the soil, Ba and Sr accumulated in the peaty horizon (798 and 706 mg kg^-1, respectively). The concentration of Cl^- ions in the soil water at the site of waste discharge was 1 912 mg L^-1, and at a distance of 200 m, it decreased to 77.4 mg L^-1. The Cl^- concentration in the groundwater was lower, and at a distance of 200 m, it was 38.9 mg L^-1. The highest concentration of petroleum hydrocarbons in the surface layer was found in the peaty-gley soils (up to 2 400 mg kg^-1). In glandular-illuvial podburs, it was 420 mg kg^-1. In horizons BH and BC, it was close to the background values (27 and 33 mg kg^-1, respectively). Alkalinization of soils and water under the influence of drill cuttings led to the death of oligotrophic and acidophilic vegetation at a distance of up to 50 m, and to the restructuring of the species and spatial structure of plant communities up to 100 m.     

鸭跖草(Commelina communis L.): 发现于中国安徽省的铜的超积累植物

Commelina communis L. growing over some new copper mining wastelands at Bijiashan, Tongling City of Anhui Province, China, was found to be a copper hyperaccumulator. Its copper concentrations were 2707~6159 (4439±2434) mg kg^-1, 369~831 (731±142) mg kg^-1, and 429~587 (547±57) mg kg^-1, respectively, in the roots, stems, and leaves. The soils supporting the growth of the species had a copper concentration ranging from 4620 to 5020 mg kg^-1 and averaging 4835±262 mg kg^-1, suggesting that the species could not only grow on heavily copper-contaminated soils but also accumulate extraordinarily high concentration of copper. Thus, it shows great potential in the phytoremediation of copper-contaminated soils, the restoration of mined land, geochemical prospecting, and the study of environmental pollution changes.     

中国土壤微生物量的大小

The microbial biomass C, N and P of soils all over China were determined in this study to study their affecting factors. The results, about 100-417 mg C kg^-1 soil, 18-51 mg N kg^-1 soil and 4.4-27.3 mg P kg^-1 soil, showed the biomass C, N and P in linear relationship with the soil total organic C, toal N and soil organic P. The ratios of C: N and C:P, ranging from 5.6 to 9.6 and from 11.2 to 48.4 respectively, were affected by soil pH, texture, crop rotation, macroclimate, etc. The ratio of C:N in soil biomass increases gradually from the north to the south in China.     

直链烷基苯磺酸盐(LAS)在土壤-植物系统中的生态学行为研究

More and more linear alkylbenzene sulfonate (LAS) has contaminated the water and soil via pollution discharge, making it important to identify the ecological behavior and toxicity of LAS so as to carry out measures that will reduce its negative effects on the ecosystem. The ecological behavior of LAS, including degradation, migration, and plant uptake, in both soil-paddy rice and soil-soybean systems was studied. Reduction of LAS in pot and field plots followed the first order reaction kinetics with degradation half-lives of 35-50 days with LAS decreasing to very low concentrations after a season of crop growth. Strong migration ability for LAS was found and the breakthrough time in a 1.5 m soil monolith was significantly shortened to 23 days by preferential flow. Leachate volumes of soil-paddy and soil-soybean systems at preferential breakthrough were much different, while the leachate volumes at equilibrium governed by soil adsorption/desorption processes were very similar. Significant uptake of LAS in both paddy rice and soybeans was observed in pot and field experiments (P < 0.05). In aquatic culture, 20 ug mL^-1 and above of LAS significantly inhibited the growth of paddy seedlings (P < 0.05). The critical concentration for LAS in soil inhibiting the growth and yield of paddy was 160 ug g^-1; when higher, there was a strong negative influence, with decreases in height, spike length, and production; when lower than 80 ug g^-1, paddy growth was stimulated. There was little effect of LAS on soybeans.     

中国陕西省施有机肥黄土NH4+固定的热力学性质

Some thermodynamic properties of NH₄⁺ fixation by loess soil in plowing and clay layers are discussed. The results indicate that the four ion adsorption equations commonly used can describe the properties of NH₄⁺ fixation in these soils under constant temperature. Among the four adsorption equations, the single-surface Langmuir equation is the best. When the concentration of NH₄Cl solution is 10^-1 mol below, the Freundlich equation can be used. The changes of apparent standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) illustrate that NH₄⁺ fixation in soil is an endothermic adsorption and spontaneous reaction, and the process can be enhanced by a higher temperature and clay content in soil. The "proper value of NH₄⁺ fixation by soil (K₁ × q_m) increased with increasing clay content and temperature. The heat of NH₄⁺ fixation in soil (Q_m) confirms the conclusions made in this paper.     

碱茅根际土壤盐分动态变化研究

A glasshouse experiment using a rhizobox technique was conducted to examine salt dynamics in the rhizosphere of a salt-tolerant grass, Puccinellia ciliata Bor. ‘Irwin Hunter', grown in a loamy soil, and to study the effect of rainfall flush on salt accumulation in the rhizosphere. The rhizobox (10 × 5.5 × 50 cm) had a nylon mesh (1 μm) positioned vertically in the middle to create two compartments filled with soil amended with 1 g NaCl kg^-1. The plants were grown in one compartment only. Flushed treatments received 275 mL of deionized water two days before harvest. In the plant-growing compartment, soils were sectioned vertically at 5 cm intervals. Significant differences in soil electrical conductivity (EC) (P < 0.05) and pH (P < 0.05) were observed for depths, but not between flushed and non-flushed treatments. In the no-plant compartment (rhizosphere), soil cores were taken horizontally at depths of 5, 20 and 40 cm and sliced at 1, 2, 3, 4, 5, 7, 10, 15 and 20 mm away from the roots. Soil EC and Cl^- concentration at the 5 and 20 cm depths, and Na⁺ concentration at the 5 cm depth significantly decreased (P < 0.05) with the distance away from the root, but no significant differences were observed in soil pH and concentrations of the K⁺ and Ca²⁺. The flush treatment only had significant influence on soil EC, pH, and Cl^- concentration at the 20 cm depth. Thus, salt accumulation could occur in the rhizosphere of salt-tolerant species on saline soils, and the periodic low rainfall might not have a strong influence on salt distribution in the rhizosphere and/or root zone.     

红三叶草丛枝菌根对有机磷的吸收

The capacities of two arbuscular mycorrhizal (AM) fungi, Glomus mosseae and Glomus versderme, tomineralize added organic P were studied in a sterilized calcareous soil. Mycorrhizal (inoculated with either of the AM fungi) and non-mycorrhizal red clover (Trghlium pmtense L.) plants were grown for eight weeksin pots with upper root, central hyphal and lower soil compartments. The hyphal and soil compartmentsreceived either organic P (as Na-phytate) or inorganic P (as KH₂PO₄) at tbe rate of 50 mg P kg^-1. No P wasadded to the root compartments. Control pots received no added P. Yields were higher in mycorrhizal than innon-mycorrhizal clover. Mycorrhizal inoculation doubled shoot P concentration and more than doubled total P uptake of plaflts in P-amended soil, irrespective of the form of applied P. The mycorrhizal contributionto inorganic P uptake was 80% or 76% in plants inoculated with G. mosseae or G. verefforme, respectively. Corresponding values were 74% and 82% when Na-phytate was applied. In the root compartments of the mycorrhizal treatments, the proportion of root length infected, hyphal length density and phosphatase activity were all higher when organic P was applied than when inorganic P was added.     

Effects of DDT and its metabolites on soil algae and enzymatic activity

 The persistence of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its metabolites in soil, their toxicity to soil algae, and effects on microbial activities were studied in laboratory microcosms for 45 days. In non-sterile soils, removal of DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane] and DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] was less than 3%, while 4–8% of applied DDMU [1-chloro-2,2-bis(p-chlorophenyl)ethylene], DDA [2,2-bis(p-chlorophenyl)acetic acid] and DDT were lost. Added DDOH [2,2-bis(p-chlorophenyl)ethanol] was more labile, as 60% was degraded during the same period. Soil microalgae were not measurably affected by the compounds tested at 10–50 mg kg^–1, but at 100 mg kg^–1 soil, DDD, DBP (p,p′-dichlorobenzophenone) and DDA significantly reduced their growth. Phosphatase activity was not affected by DDT and its metabolites at the concentrations tested (≤50 mg kg^–1), but all compounds inhibited dehydrogenase activity at concentrations of 50 mg kg^–1 soil. The toxic effects of DDT and its metabolites were dose-related. Received: 9 January 1998     

<Emphasis Type="Italic">Trichoderma</Emphasis> inoculation and trash management effects on soil microbial biomass,soil respiration,nutrient uptake and yield of ratoon sugarcane under subtropical conditions

A field experiment was conducted during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow, India to study the effect of Trichoderma viride inoculation in ratoon sugarcane with three trash management practices, i.e. trash mulching, trash burning and trash removal. Trichoderma inoculation with trash mulch increased soil organic carbon and phosphorus (P) content by 5.08 Mg ha⁻¹ and 11.7 kg ha⁻¹ over their initial contents of 15.75 Mg ha⁻¹ and 12.5 kg ha⁻¹, respectively. Soil compaction evaluated as bulk density in 0- to 15-cm soil layer, increased from 1.48 Mg m⁻³ at ratoon initiation (in April) to 1.53 Mg m⁻³ at harvest (in December) due to trash burning and from 1.42 Mg m⁻³ at ratoon initiation (in April) to 1.48 Mg m⁻³ at harvest (in December) due to trash mulching. The soil basal respiration was the highest during tillering phase and then decreased gradually, thereafter with the advancement of crop growth. On an average, at all the stages of crop growth, Trichoderma inoculation increased the soil basal respiration over no inoculation. Soil microbial biomass increased in all plots except in the plots of trash burning/removal without Trichoderma inoculation. The maximum increase (40 mg C kg⁻¹ soil) in soil microbial biomass C, however, was observed in the plots of trash mulch with Trichoderma inoculation treatment which also recorded the highest uptake of nutrient and cane yield. On an average, Trichoderma inoculation with trash mulch increased N, P and K uptake by 15.9, 4.68 and 23.6 kg ha⁻¹, respectively, over uninoculated condition. The cane yield was increased by 12.8 Mg ha⁻¹ with trash mulch + Trichoderma over trash removal without Trichoderma. Upon degradation, trash mulch served as a source of energy for enhanced multiplication of soil bacteria and fungi and provided suitable niche for plant–microbe interaction.     

Suitability of Immobilized Pseudomonas fluorescens SM1 Strain for Remediation of Phenols, Heavy Metals, and Pesticides from Water

Immobilized microbial cells for the biological treatment have the potential to degrade toxic chemicals faster than conventional wastewater treatment systems. In the present study, suitability of immobilized Pseudomonas fluorescens SM1 strain in calcium alginate beads for remediation of the major toxicants in Indian water bodies was tested by means of GC/HPLC and AAS techniques. Roughly 80% reduction in the concentration of phenols was observed by immobilized SM1 cells compared with 60% by the free cells. Also, in the case of the bioremediation of heavy metals, immobilized SM1 cells were found to be more efficient compared with the free cells. Suspension of P. fluorescens SM1 cells in the test model water for 24 h brought down the concentrations of Cu⁺⁺, Cd⁺⁺, Ni⁺⁺, and Pb⁺⁺ by more than 75% under free cell state and 7?C9% better efficiency under the immobilized conditions. However, Cr(VI) could show only 44% removal by the cell immobilized system, whereas a mere 35% reduction in the Cr(VI) levels was shown in the test model water by the free SM1 cells under the same conditions. Moreover, a model water containing 2,000 ppb of BHC, 1,248 ppb mancozeb, and 312 ppb 2,4-D passed through the cell immobilized column resulted in the decline in their concentrations up to 362 ppb, 750 ppb, and 126 ppb, respectively. Generally, AAS, HPLC, and GC analyses of treated test model waters with the free and immobilized SM1 cells exhibited high potential of immobilized SM1 in detoxification of test water. From the results, we conclude that immobilized cells of P. fluorescens SM1 strain were quite effective in bioremediation of major toxicants present in Indian water bodies, and we also recommend the use of immobilized bacterial cells rather than the free cells for the bioremediation/detoxification process.     

胶冻样芽孢杆菌与生物质炭复配及对番茄产量和品质的影响

以提高胶冻样芽孢杆菌在土壤中的存活率、减缓其衰亡速率,延长存活时间,提高其对土壤难溶性钾的解钾效率为目的,利用不同种类的秸秆生物质炭与胶冻样芽孢杆菌进行复配筛选。通过室内培养试验发现,中性小麦秸秆炭可作为胶冻样芽孢杆菌较理想的载体。当土壤培养35天后,土壤速效钾含量在施用炭基解钾菌肥条件下较空白提高了28.53%,较小麦秸秆炭和纯菌液处理分别提高了20.75%、13.41%。纯菌液处理土壤中胶冻样芽孢杆菌的菌落数从1.1×10~9个/g土降为9.0×10~5个/g土,而炭基解钾菌肥处理则为1.4×10~7个/g土。田间施用炭基解钾菌肥能够提高番茄植株和果实中的全钾含量;提高番茄产量和品质,显著提高番茄Vc含量,降低硝酸盐含量。因此,中性小麦秸秆炭与胶冻样芽孢杆菌的复配能够提高菌剂的存活率,有效促进土壤中矿物态钾的释放。     

Bioremediation of an Experimental Oil Spill in a Coastal Louisiana Salt Marsh

The massive oil release from the Deep Water Horizon disaster has reemphasized the need to remediate oil impacted marshes. Due to the physically fragile nature of salt water marshes, bioremediation is often proposed as an appropriate technology and nutrient amendment is often proposed as a means of accelerating biodegradation of crude oil. However, no information is currently available concerning the efficacy of in situ nutrient amendments in Gulf Coast salt marshes. An experimental crude oil spill (142 l over 100 m²) was conducted to evaluate the efficacy of nitrogen amendment to stimulate bioremediation in a Spartina alterniflora dominated Louisiana salt marsh. A randomized complete block design with replication (n = 10) was utilized to test the hypothesis that additions of fast-release ammonium nitrate (60 g N/m²) and slow-release urea (30 g N/m²) fertilizers could enhance biodegradation of selected crude oil components in the marsh. Crude oil degradation was monitored by analyzing sediment samples for branched and unbranched alkanes over the 180-day study period. The compound/hopane ratio was used to correct for nonbiological losses. No consistent statistically significant effect of fertilizer addition on degradation rates was observed, despite success in increasing the porewater ammonium and NaCl-extractable ammonium over the time frame of the trial. Intrinsic pseudo-first order degradation rates of alkanes in all plots were substantial (0.003–0.008 day⁻¹). Existing, background levels of N did not appear to limit biodegradation rates in Spartina-dominated salt marshes. These results suggest that nutrient amendments will not be successful in stimulation biodegradation of crude oil in these systems.     

Growth of Tropical Legume Cover Crops as Influenced by Nitrogen Fertilization and Rhizobia

Tropical legume cover crops are important components in cropping systems because of their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were (i) 0 mg N kg^?1 (control or N₀), (ii) 0 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₁), (iii) 100 mg N kg^?1 + inoculation with Bradyrhizobial strains (N₂), and (iv) 200 mg N kg^?1 of soil (N₃). The N?×?cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length, and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and, overall, maximal shoot dry weight was produced at 100 mg N kg^?1 + inoculation treatment. Based on shoot dry-weight efficiency index, cover crops were classified as efficient, moderately efficient, and inefficient in N-use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean, and black velvet bean and inefficient cover crops were pueraria, calopo, crotalaria, smooth crotalaria, and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.     

Ecological pre-release risk assessment of two genetically engineered, bioluminescent Rhizobium meliloti strains in soil column model systems

In order to identify potential ecological risks associated with the environmental release of two Rhizobium meliloti strains, genetically engineered with the firefly-derived luciferase gene (luc), a pre-release greenhouse investigation was conducted. The upper 4 cm of soil columns (30 cm diameter; 65 cm depth), which were filled according to the horizons of an agricultural field (loamy sand), were inoculated with seeds of Medicago sativa (alfalfa) and R. meliloti cells at approximately 5×10⁶ cells·g^–1 soil. Four treatments were tested: inoculation with a non-engineered wild type strain (2011), strain L33 (luc ⁺), strain L1(luc ⁺, recA^–) and non-inoculated controls. The fate of the engineered strains was followed by two methods: (1) selective cultivation and subsequent detection of bioluminescent colonies and (2) PCR detection of the luc gene in DNA, directly extracted from soil. Strain R. meliloti L33 declined to 9.0×10⁴ cfu·g^–1 soil within 24 weeks and to 2.8×10³ cfu·g^–1 soil within 85 weeks in the upper 25 cm of the soil columns. Decline rates for R. meliloti L1 were not significantly different. Vertical distribution analysis of the recombinant cells after 37 weeks revealed that in three of four columns tested, the majority of cells (>98%) remained above 10 cm soil depth and no recombinant cells occurred below 20 cm depth. However, in one column all horizons below 20 cm were colonized with 2.2×10⁴ to 6.8×10⁴ cfu g^–1 soil. Ecological monitoring parameters included organic substance, total nitrogen, ammonium and nitrate, microbial biomass, culturable bacteria on four different growth media and the immediate utilization of 95 carbon sources (BiologGN) by soil-extracted microbial consortia. None of the parameters was specifically affected by the genetically engineered cells. Received: 6 December 1996     

Bioremediation of Co-contamination of Crude Oil and Heavy Metals in Soil by Phytoremediation Using Chromolaena odorata (L) King & H.E. Robinson

The capability of Chromolaena odorata (L) to grow in the presence of different concentrations of three heavy metals in crude oil-contaminated soil and its capability to remediate the contaminated soil was investigated using pot experiments. C. odorata plants were transplanted into contaminated soil containing 50,000 mg kg^?1 crude oil and between 100 and 2,000 mg kg^?1 of cadmium, nickel, and zinc and watered weekly with water containing 5% NPK fertilizer for 180 days. C. odorata did not show any growth inhibition in 50,000 mg kg^?1 crude oil. Plants in experiments containing 2,000 mg kg^?1 Cd showed little adverse effect compared to those in Zn-treated soil. Plants in 1,000 and 2,000 mg kg^?1 Ni experiments showed more adverse effects. After 180 days, reduction in heavy metals were: 100 mg kg^?1 experiments, Zn (35%), Cd (33%), and Ni (23%); 500 mg kg^?1, Zn (37%), Cd (41%), and Ni (25%); 1,000 mg kg^?1, Zn (65%), Cd (55%), and Ni (44%); and 2,000 mg kg^?1, Zn (63%), Cd (62%), and Ni (47%). The results showed that the plants accumulated more of the Zn than Cd and Ni. Accumulation of Zn and Cd was highest in the 2,000 mg kg^?1 experiments and Ni in the 500 mg kg^?1 experiments. Crude oil was reduced by 82% in the experiments that did not contain heavy metals and by up to 80% in the heavy metal-treated soil. The control experiments showed a reduction of up to 47% in crude oil concentration, which was attributed to microbial action and natural attenuation. These results show that C. odorata (L) has the capability of thriving and phytoaccumulating heavy metals in contaminated soils while facilitating the removal of the contaminant crude oil. It also shows that the plant??s capability to mediate the removal of crude oil in contaminated soil is not significantly affected by the concentrations of metals in the soil.     

Nickel Biosorption by Free and Immobilized Cells of Pseudomonas fluorescens 4F39: A Comparative Study

The biosorption of nickel ions on Pseudomonasfluorescens 4F39 free cells or immobilized cells in beads of agar (biobeads)has been studied in batch experiments to determine the effect ofcell immobilization on the metal accumulation properties of bothsystems. Bacterial cells were immobilized in agar beads followingthe interphase technique. When free cells were used, the sorptionequilibrium was reached in 5 min but with biobeads it took 24 hr as a consequence of metal diffusion. The pH of the Ni²⁺solution was found to be critical for Ni²⁺ accumulation,the optimum being 8, although the magnitude of this effect waslower in immobilized cells. The equilibrium data have been analysed using the Langmuir adsorption model. The q _max of free cells, immobilized cells and biobeads was 145, 37 and7.6 mg Ni²⁺/g dry sorbent, respectively. The removal capacity of free cells and immobilized cells increased when the cell concentration decreased. The maximum removal efficiency ofbiobeads was obtained when the cell concentration was 1.43 mg drycells/mL Ni²⁺ solution. The agar concentration in biobeads affected the Ni²⁺ accumulation, the optimum being 2%. Desorption of Ni²⁺ with 0.5 mM dipicolinic acid was efficient. Cycles of accumulation/desorption resulted in a lossof non immobilized cells. An increase of the removal efficiencyfrom the first cycle of accumulation/desorption was observed with biobeads.     

Effects of glucose and rhizodeposits (with or without cysteine-S) on immobilized-35S, microbial biomass-35S and arylsulphatase activity in a calcareous and an acid brown soil

Our aim was to study the effects of C (as glucose and artificial rhizodeposits) on S immobilization, in relation to microbial biomass‐S and soil arylsulphatase (ARS) activity, in contrasting soils (a calcareous and an acid brown soil). The glucose‐C and artificial rhizodeposit‐C with or without cysteine were added at six rates (0, 100, 200, 400, 600 and 800 mg kg^?1 soil) to the two soils and then incubated with Na₂³⁵SO₄ for 1 week prior to analysis. The percentages of ³⁵S immobilized increased when C as glucose and rhizodeposit (without cysteine) were added to both soils. With cysteine‐containing rhizodeposit, the percentages of ³⁵S immobilized remained relatively stable (23.5% to 29.9%) in the calcareous soil, but decreased in the acid brown soil (52.7% to 31.5%). For both soils, cysteine‐containing rhizodeposit additions showed no significant correlation between immobilized‐³⁵S and microbial biomass‐³⁵S, suggesting that microorganisms immobilized cysteine‐S preferentially instead of ³⁵S from the tracer (Na₂³⁵SO₄). In the calcareous soil, a positive and significant correlation was found between ARS activity and microbial biomass‐³⁵S (r = 0.85, P < 0.05) when glucose was added. We also saw this correlation in the acid brown soil when rhizodeposit‐C without cysteine was added (r = 0.90, P < 0.05). Accordingly, the results showed the presence of extracellular arylsulphatase activity of 48.7 mg p‐nitrophenol kg^?1 soil hour^?1 in the calcareous soil and of 27.0 mg p‐nitrophenol kg^?1 soil hour^?1 in the acid brown soil.