VA菌根对土壤酸度的耐性

The ammonification,nitrifcation and denitrification in maize rhizosphere of alluvial sols were compared with those in the bulk soil after exposure to different kinds of heavy metals.The addition of cadmium at low levels (2 mg kg^-1 and 5 mg kg^-1）could stimulate the ammonification and nitrification in the soils,while inhibition influences were found at high levels of Cd addition (10 mg kg^-1 and 20mg kg^-1），The relationship between microbial activity and cadmium concentration varied with the kind of microorganisms.The nitrifying bacteria were more sensitive to cadmium pollution than the ammonifying bacteria.When Cd( Ⅱ），Cu（Ⅱ）and Cr（Ⅵ）wer compared at the same addition concentration of 20 mg kg^-1 soil,Cd(Ⅱ） was the most effective inhibitor of ammonification and denitrification. among the three investigated heavy metals,and Cr（Ⅵ）had the most strong inhibitory influence on the nitrifying bacteria.The microbial activities in rhizosphere were higher than those in the bulk soil for most of the treatments.Cr(Ⅵ)proved to be the most effective in enhacing the microbial activities in rhizosphere,and this could be caused by the poitive reduction of Cr(Ⅵ）to Cr(Ⅲ）in rhizosphere,and the relatively sufficient existence of organic matter which intensified the adsorption of the metal,It seemed that the rhizosphere had some mitigation effect on heavy metal toxicity.     

Delayed immobilization of heavy metals in soils and sediments under reducing and anaerobic conditions; consequences for flooding and storage

Purpose  

The consequences of permanent inundation and storage of flood plain soils and aquatic sediments on metal mobility were studied. The main goal was to quantify kinetic mobilisation processes in order to pinpoint the conditions that pose emission risks to groundwater and surface waters.     

Phosphorus uptake and rhizosphere properties of intercropped and monocropped maize, faba bean, and white lupin in acidic soil

Little information is available on phosphorus (P) uptake and rhizosphere processes in maize (Zea mays L.), faba bean (Vicia faba L.), and white lupin (Lupinus albus L.) when intercropped or grown alone in acidic soil. We studied P uptake and soil pH, carboxylate concentration, and microbial community structure in the rhizosphere of maize, faba bean, and white lupin in an acidic soil with 0–250 mg P (kg⁻¹ soil) as KH₂PO₄ (KP) or FePO₄ (FeP) with species grown alone or intercropped. All plant species increased the pH compared to unplanted control, particularly faba bean. High KP supply (>100 mg P kg⁻¹) significantly increased carboxylate concentration in the rhizosphere of maize. The carboxylate composition of the rhizosphere soil of maize and white lupin was significantly affected by P form (KP or FeP), whereas, this was not the case for faba bean. In maize, the carboxylate composition of the rhizosphere soil differed significantly between intercropping and monocropping. Yield and P uptake were similar in monocropping and intercropping. Monocropped faba bean had a greater concentration of phospholipid fatty acids in the rhizosphere than that in intercropping. Intercropping changed the microbial community structure in faba bean but not in the other corps. The results show that P supply and P form, as well as intercropping can affect carboxylate concentration and microbial community composition in the rhizosphere, but that the effect is plant species-specific. In contrast to previous studies in alkaline soils, intercropping of maize with legumes did not result in increased maize growth suggesting that the legumes did not increase P availability to maize in this acidic soil.     

Concentration and deposition of trace metals in Ontario-1982

Results of trace metal concentrations in air and precipitation and the corresponding wet and dry deposition in Ontario in 1982 arc reported. In terms of the spatial patterns, in general, there was a decreasing gradient from south-to-north in both concentration and deposition. Patterns differed with each parameter although certain groups of metals (e.g., Fe and Al; Pb, Zn, and Mn) displayed similar patterns. In general, wet deposition was greater than dry deposition at all sites. Geographically, the variability in the wet to dry deposition ratio for coarse particles (MMD > 2.5 μm) was small. However, it increased from the south to the north for fine particles (MMD < 2.5 μm), being higher away from the source areas. Scavenging ratios (W) have been derived from the precipitation and air concentrations of trace metals. The scatter in W is quite large for all trace metals, up to 2 orders of magnitude. There was little seasonal variability in W for fine particles (Pb, Mn, Zn, and Cd). However, coarse particles (Fe, Al, and Cu) were more efficiently scavenged by snow than by rain.     

Coregionalization of trace metals in the soil in the Swiss Jura

The provenance of trace metals in soil, whether from the parent material or from pollution, is rarely known with certainty, and the metals' history must usually be pieced together from fragmentary statistical information. This is particularly true in the Swiss Jura where the concentrations of several heavy metals around La Chaux de Fonds exceed the statutory recommended thresholds for safety. The topsoil of the 14.5-km² region was sampled on a square grid at 250-m intervals with additional nesting with distances of 100 m, 40 m, 16 m and 6 m. The concentrations of seven potentially toxic metals, namely Cd, Co, Cr, Cu, Ni, Pb and Zn, were measured. Their coregionalization could be represented by a linear model consisting of a nugget component plus two spherical structures with ranges of 0.2 km and 1.3 km. The short-range component dominated the variograms of Cd, Cr, Cu and Pb; the long-range component dominated those of Co and Ni; the variogram of Zn combined the two in approximately equal proportions. The coregionalization matrices contain moderate correlation among the nugget and the short-range components, notably between Cu and Pb, between Cd and Zn, and between Cr, Ni and Zn. The strongest correlations are at the long range between Co, Cr and Ni, and to a somewhat smaller degree between Zn and Co. Analysis of variance showed Co and Ni to be related to geology, and to the Argovian formation in particular. The indicator variogram of this formation has also a short-range component. The analysis also showed Cr and Cu to be related to land use (in different ways). Copper and Pb are strongly correlated to one another and distinct from the five other metals. The long-range structure is almost certainly a geological effect, whereas the one of short range probably results from both the geology and human activities.     

Origin,retention and release of trace metals from sediments of the river seine

Metallic contents (Fe, Mn, Pb, Cu, Cd, Zn, Cr) of sediments were measured in 14 sites in the River Seine (France) along 110 km; in three sites surrounding the sewage treatment plant at Achères, vertical profiles were established from cores and dialysis cells, and interface exchanges have been studied. Metal contamination increases downstream, except for Pb for which contamination is higher immediately downstream of stormdrains (up to 130 mg kg^?1); that confirms its urban origin. Upstream of Achères, metallic contamination increases with depth while downstream, contribution to sediments of suspended matter from the treatment plant, loaded with organic matter, alters the behaviour of metals within the first ten centimeters. A strong link between particulate organic carbon (POC), polycyclic aromatic hydrocarbons (PAH), polychlorobiphenyls (PCB) and metal contents has been established. The organic matter brought down by the treatment plant effluents induces a specific diagenesis downstream leading to metal release in summer as attested by a 30% metal contents decrease in sediments. Calculation of molecular diffusion fluxes shows that in september, the release phenomenon is ending.     

Dissolved and particulate trace metals in a wetland of international importance: Lake Mikri Prespa,Greece

This paper reports the dissolved and particulate trace metal distributions in Lake Mikri Prespa, wetland of NW Greece. The concentrations of Cu, Pb, Zn, Cd, Al, Fe, Mn, Ni and Cr were determined in surface and hypolimnetic waters as well as in the inputs and the outflow. Trace metals were connected with two major populations of suspended particles, identified by using the recovery ratio for two different leaching reagents, namely 0.5 N HCl and 1:1 hot aqueous HNO₃. The first group is land derived entering the lake through runoff and plays a rather restricted role in its geochemistry. The second group which is more important includes authigenic carbonates, Fe and Mn hydroxides and oxides and organic rich particulates.     

酸性根际肥对石灰性土壤pH和铁有效性的影响研究

在无植物栽培的条件下通过肥料在土壤中的扩散试验研究酸性根际肥对石灰性土壤 pH值、有效铁含量的影响 ,利用盆栽试验验证对石灰性土壤上花生缺铁失绿黄化症的矫正效果。结果表明 ,酸性根际肥 (pH 1.0～ 2 .0 )中的酸在土壤中扩散的影响半径可达 6cm ,但对土壤pH降低作用最显著的是在距肥料 2cm内 ;在施肥 2 8d内 ,距肥料 2cm处 ,土壤 pH值降低了 0 .9个单位 ,土壤铁有效性 (DTPA浸提量 )增加了 5 .9mg kg ;施用酸性根际肥可使花生叶绿素SPAD值与叶片活性铁含量显著提高 ,克服了花生缺铁黄化症状 ,使施肥区 (肥料周围 2cm内 )土壤pH值显著降低 ,并显著提高了该区土壤铁的有效性和花生对土壤Fe的吸收量。     

Proton release by roots of Medicago murex and Medicago sativa growing in acidic conditions, and implications for rhizosphere pH changes and nodulation at low pH

Medicago murex nodulates faster and produces more nodules than Medicago sativa in acidic sandy soils. Experiments using a ‘root mat’ approach and videodensitometry examined pH changes in the rhizospheres of nitrate-fed plants of M. murex and M. sativa. Using the ‘root mat’ approach with soil disks of pH 4.49, M. sativa cv. Aquarius acidified its rhizosphere by approximately 0.2-0.4 pH-units within 4 d, while M. murex cv. Zodiac did not acidify its rhizosphere. Rates of H⁺ release were higher from M. sativa than from M. murex. Videodensitometry of roots embedded in agarose of pH 4.5 showed that the mature parts of the tap-root of both species exuded OH⁻ ions, but was approximately twofold more in M. murex than in M. sativa. Consequently, young parts of the M. sativa rhizosphere were less alkaline than that of M. murex. It is suggested that the difference in nodulation response between the two species at low pH may be related to the different patterns of rhizosphere acidification: the stronger rhizosphere acidification of M. sativa being less favourable for survival and growth of Sinorhizobium medicae. The higher rate of rhizosphere acidification by M. sativa roots may be related to its genetic characteristics including greater relative root growth rate and greater sensitivity to acidity in comparison to M. murex.     

Effects of flooding and redox conditions on solute diffusion in soil

Rates of solute diffusion fundamentally affect the properties of flooded soils, but the effects of flooding on solute diffusion have not previously been studied in detail. Four soils with widely differing chemical and physical properties were packed to a range of bulk densities, flooded for varying times, and the self‐diffusion of chloride through the soils measured. Diffusion impedance factors were derived from the results. In each soil the impedance factor decreased linearly with increase in bulk density, and between soils impedance factors increased with increasing clay content. The impedance factor decreased by up to 20% during the first 3–6 weeks following flooding, but with prolonged flooding it increased to at least its initial value. Concomitantly the cation exchange capacities of the soils increased by between 30 and 100%, there was reductive dissolution of soil iron, probably both structural iron in soil clays and iron oxyhydroxide coatings on clay surfaces, and subsequently there was re‐precipitation of ferrous iron, probably as mixed carbonates and hydroxides. The decreases in diffusion impedance factors were consistent with the increases in cation exchange capacity and changes in soil iron, and the subsequent increases were consistent with re‐crystallization of mixed ferrous–ferric compounds. We conclude that the effects of changes in redox on diffusion impedance will be important in some soils, although they are smaller than the effects of water content per se.     

Detection of aluminium tolerance plasmids and microbial diversity in the rhizosphere of plants grown in acidic volcanic soil

The rhizosphere is considered as a hot-spot for gene exchange among bacteria in terrestrial ecosystems. Chilean volcanic soils are characterized by low pH and high concentrations of aluminium (Al) in the soil solution, thus Al tolerance could be important for the survival of microorganisms in these soils; loss of genes encoding for Al tolerance may affect competitiveness particularly in the rhizosphere where competition is strong. The occurrence of Al-tolerance plasmids was investigated in the rhizospheres of pasture and crop plants growing in acidic volcanic soils from southern Chile. Al tolerance plasmids were captured by biparental mating. Two types of Al tolerance plasmids could be distinguished, based on their endonuclease restriction pattern. One plasmid of each group (denoted as pRPA21 and pOPA21) was selected for further studies. The plasmids showed a high stability in presence and absence of Al. Additionally, microbial community composition in the rhizosphere soils was assessed by denaturing gradient gel electrophoresis (DGGE). Sequencing of DGGE bands revealed among others, members of the bacterial phylum Gemmatimonadetes and archaeal phylum Crenarchaeota. The present study shows that the rhizosphere of pasture and crop plants growing in Chilean volcanic soil harbors genetic mobile elements which could play a role in the adaptation of bacterial populations to environmental stressors, such as Al-toxicity.     

Statistical models for the accumulation of PAH,chlorinated hydrocarbons and trace metals in epiphytic Hypnum cupressiforme

Concentrations of PAH (1.12-benzoperylene, 3.4-benzopyrene, fluoranthene), chlorinated hydrocarbons (α-BHC, lindane, PCB) and trace metals (Zn, Pb, Cu) in bulk precipitation, as well as PAH and trace metal concentrations in atmospheric dust samples from 14 sites in Bavaria, F.R.G. are presented for two vegetation periods (1979 and 1980). The same substances were also analyzed in epiphytic moss (Hypnum cupressiforme var. filiforme) sampled from tree trunks in October 1979 and 1980. Using mean immission values and the amount of precipitation as predictors and concentrations of pollutants in moss samples as criteria, a number of multiple regression models were computed in order to quantify the relationships between absolute air pollution data and accumulated trace substance values. Beta values of all variables help to determine whether bulk precipitation or atmospheric particulate matter has dominant influence on the uptake of trace substances by mosses. The study shows that epiphytic mosses can be used to monitor both heavy-metal, PAH and chlorinated hydrocarbons.     

Phytotoxicity and some interactions of the essential trace metals iron,manganese, molybdenum,zinc, copper,and boron

Abstract

The essential trace elements Fe, Mn, Zn, Cu, and B in high concentrations can produce phytotoxicities. Iron toxicity resulted from 5 × 10^‐4 M and 10^‐3 M FeSO₄, but not from equivalent amounts of FeEDDHA (ferric ethylenediamine di (o‐hydroxyphenylacetic acid) ). Leaf concentrations in bush beans of 465 μg Mn/g, 291 μg B/g, and 321 μg Zn/g all on the dry weight basis resulted in 27%, 45%, and 34% reduction in yields of leaves, respectively. Zinc was concentrated in roots while Mn and B concentrated in leaves. Solution concentrations of MnS0₄ of 10^‐3 and 10^‐2 M depressed leaf yields of bush beans by 63% and 83%, respectively, with 5140 and 10780 μg Mn/g dry weight of leaves. Copper concentrations were simultaneously increased and those of Ca were decreased. Bush bean plants grown in Yolo loam soil with 200 μg Cu/g soil had a depression in leaf yield of 26% (with 28. 8 μg Cu/g leaf); plants failed to grow with 500 μg Cu/g soil. A level of 10^‐3 M H₂MoO₄ was toxic to bush beans grown in solution culture. Leaves, stems, and roots, respectively, contained 710, and 1054, and 5920 μg Mo/g dry weight.     

Factors influencing atmospheric deposition,stream export,and landscape accumulation of trace metals in forested watersheds

Wet and dry deposition inputs and streamflow output of Cd, Mn, Pb, Zn, and Al were measured intermittently at four deciduous forested watersheds in the southeastern United States between 1976 and 1982. Atmospheric inputs to each site were similar, varying by factors of 1.1 to 2.2 for the different metals. Metal levels in precipitation indicate that these sites are representative of rural, continental areas. Metals in rain exhibit significant temporal and spatial trends, with concentrations generally higher during summer than winter at all sites and generally lowest at the more remote site. The concentrations of Cd and Pb in both wet and dry deposition decreased between the period 1976 to 1977 and 1981 to 1982. Ion ratios and enrichment factors suggest that Mn is largely soil derived in atmospheric samples while Cd, Pb, and Zn are enriched over typical soil levels. Factor analysis indicates that soil components influence both Al and Mn while fine aerosol components influence Cd in wet and dry deposition. Both components influence the behavior of Pb. Dry deposition dominated the input of Mn and Al to each site, while wet deposition was the major input process for the other metals (54 to 85% of total). On an annual basis, deposited Cd, Pb, and Zn are strongly retained in each watershed: 2% of the Pb, 8 to 29% of the Cd, and 8 to 34% of the Zn inputs were transported in stream flow. Deposited Mn and Al are retained to a lesser degree and show a net loss from two sites. Metal export is controlled by stream pH, organic carbon, bedrock geology, and hydrologic characteristics of each site.     

Effects of compost type and storage conditions on climbing bean on Technosols of Tantalum mining sites in Western Rwanda

Little is known about the effects of compost application to reclaim artisanal mining sites for agriculture in Central Africa. A field experiment was therefore conducted to examine the effects of locally available organic household waste composted under traditional (pit under leaf shade) versus improved management (pit under double plastic sheeting) and mixed with either Tithonia diversifolia biomass or Minjingu Phosphate Rock (13–15% P) on climbing bean sown on degraded Technosols (former Tantalum mining sites) and un‐mined control soils (Cambisols). Both soil types were derived from pegmatite. After 6 months of composting, nutrient concentrations in traditional compost were 0.27–0.32% N, 0.06–0.08% P, and 0.20–0.22% K. Comparative values in amended compost were 1.02–1.65% N, 0.10–0.31% P, and 0.41–1.13% K. In farmyard+solid waste, composted under traditional system, dry matter was 65.4%, pH 6.7, and C : N ratio 13.0, as opposed to 81.5% DM, a pH of 8.6, and a C : N ratio of 8.6 in farmyard+solid waste+Minjingu phosphate under improved compost, and 68.3% dry matter, a pH of 8.4, and a C : N ratio of 7.4 for Tithonia +farmyard+solid waste under improved conditions. Compared to bean (Phaseolus vulgaris L.) grain yields of 0.28 (mined soil) and 0.11 (unmined soil) without amendments, the application (on a dry matter basis) of 5 t compost ha⁻¹ led to yields of 3.54 t DM ha⁻¹ for improved compost Tithonia +farmyard+solid waste on mined soil versus 2.26 t DM ha⁻¹ (P < 5%) for the same treatment at the un‐mined sites. The yield obtained for farmyard+solid waste+Minjingu phosphate composted under improved conditions averaged 3.06 t DM ha⁻¹ at mined sites compared with 2.85 t DM ha⁻¹ at un‐mined sites (P > 5%). All amendments were more effective in enhancing bean yields on Technosols with significant positive effects with improved compost than on Cambisols.     

Sorption of trace metals by suction cups of aluminium oxide,ceramic and plastics

The sorption properties of ceramic, aluminium oxide and plastic suction cups in respect to trace metals (Be, Cd, Co, Cu, Mn, Ni, Pb, Zn) were compared in laboratory and field experiments. The sorption effect is determined by the level of the cation exchange capacity of the cup material, the pH-value of the soil solution, the content of dissolved organic carbon, the sampling rate and the sampled volume. Sorption was generally negligible only in case of cobalt, manganese and nickel. At low pH-values no retention of trace metals occurred with the exception of lead in the aluminium oxide and the ceramic cups. At pH-values of about 8 cadmium and zinc were strongly sorbed only by aluminium oxide and ceramic cups whereas beryllium, copper and lead were markedly sorbed at this pH-range by all cup types. These results are only valid for the boundary conditions used. Whenever a suction cup's suitability is in doubt it should be tested after a conditioning procedure using realistic boundary conditions.     

Concentration and partitioning of particulate trace metals in the Changjiang (Yangtze River)

Suspended sediments from the lower Changjiang (Yangtze River) were sampled to determine concentrations of Cu, Cd, Pb, Ni, and Cr. The particulate trace element values in the Changjiang are higher than in the Huanghe (Yellow River), but lower than in the other large Chinese rivers (e.g. Pearl River) and polluted rivers. A general pattern of high element levels in the clay minerals and low element concentrations in coarse sediment fractions are observed in the Changjiang. Sequential extraction shows the predominance of metals in the residual fraction relative to labile fractions in the Changjiang, emphasizing the importance of natural weathering and erosion in the drainage basin on the transport of particulate metals. Elevated Enrichment Factors (EF: the ratio of element concentration in microsurface to that in subsurface layer minus 1.0) suggest a potential influence of atmospheric input on the concentrations of particulate metals in the river.     

复合污染土壤中水稻根际元素特性及效应研究

【目的】以广东大宝山重金属复合污染农田为生长介质,通过研究水稻不同部位生长量、 金属含量、 对金属的富集系数,及其与根际、 非根际土金属含量、 形态变化的相关关系,探讨根际效应可能对水稻体内金属积累转运以及生物量的影响。【方法】选取了广东大宝山稻田重金属复合污染(As、 Pb、 Fe、 Cu、 Zn)土壤及当地常见的20个水稻品种进行根际袋试验,即将根际袋内的土视为根际土,根际袋外的土视为非根际土,将供试水稻品种种植于根际袋土壤中60天后收获,测定水稻各部位的生长量、 不同金属的含量,根际土和非根际土中各金属有效态的含量。【结果】Fe、 Cu、 Pb、 Zn、 As在根部的富集系数均大于其在茎叶的富集系数,各金属在茎叶和根部的富集能力排序分别为Zn Cu As ≈ Pb ≈ Fe和Fe Zn As Cu Pb。根际土和非根际土中各种金属有效态含量均为Fe Cu Pb Zn As。研究还发现,有效态Fe、 Cu和Zn浓度对整株干重的影响显著,作用强弱顺序为Cu Zn Fe,对水稻生长影响作用显著的三种有效态金属Fe、 Cu和Zn均为植物生长所必需的元素。供试土壤中有效态Cu浓度对水稻的生长所起的作用最强。根际土有效态Fe浓度对根系Fe的积累作用效果显著,有效态As浓度显著抑制了根系Fe的积累,且有效态As浓度的作用强于有效态Fe。【结论】根际土中有效态Fe对株高、 根干重、 茎叶干重和整株干重均起着抑制作用,有效态Cu对水稻生长起到了促进作用。根际土有效态As和非根际土有效态Zn对根部Fe的积累起到了抑制作用,根际土有效态Fe和非根际土有效态Cu则起到了促进作用。非根际土有效态Fe和有效态Zn对水稻根长的增加均起到了促进作用。     

Microsensor analysis of oxygen and pH in the rice rhizosphere under field and laboratory conditions

 O₂ and pH microsensors were used to analyse the microdistribution of O₂ and pH inside and outside roots of lowland rice (Oryza sativa L.). The roots of 3-week-old transplants had O₂ concentrations of about 20% air saturation at the surface, but due to a high rate of O₂ consumption in the rhizosphere, the oxic region only extended about 0.4 mm into the surrounding soil. Also the fine lateral roots created an oxic zone extending about 0.15 mm into the soil. The O₂ concentration within the roots approached air saturation close to the base, but only about 40–60% of air saturation in a region about 8 cm below the base where lateral rootlets were present. A shift from air to N₂ around the leaves led to a drop of 50% in the O₂ concentration after 12 min at a distance of 8.5 cm from the base. Flowering plants did not export O₂ to the soil from the majority of their roots, but high microbial activity was present in a very thin biofilm covering the root surface. A brown colour around the thin lateral roots indicated some O₂ export from these also during flowering. No oxidized zone was present around the roots at later stages of crop growth. The roots caused only minor minima in pH (<0.2 pH units) in the rhizosphere as compared to the bulk soil. Illumination of the plants had no effect on rhizosphere pH. Received: 28 April 1998     

Distribution of exudates of lupin roots in the rhizosphere under phosphorus deficient conditions

Abstract

The distribution of secretory acid phosphatase and organic acids enhanced by phosphorus deficiency in lupin rhizosphere was investigated using a rhizobox system which separated the rhizosphere soil into 0.5 mm fractions. In the soil fraction closest to the root surface, the lupin exudates displayed an acid phosphatase activity of 0.73 u g^?1 dry soil and citrate concentration of 85.2 μmol g^?1 dry soil, respectively. The increase of the acid phosphatase activity-induced an appreciable depletion of organic P in the rhizosphere, indicating that lupin efficiently utilized the organic P from soil through the enzyme activitye The sterile treatments demonstrated that the acid phosphatase in the rhizosphere was mainly derived from lupin root secretions. The secretory organic acids enhanced considerably the solubility of the inorganic P in three types of soil and a sludge. However, the secretory acid phosphatase and organic acids from lupin roots were only detected in a considerable amount in 0-2.5 mm soil fractions from root surface.