Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill wastewaters

A dark and complex metal polymeric organic mixture, named polymerin, was recovered from olive oil mill wastewaters (OMWW) and characterized by chemical analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and atomic absorption spectrometry (AAS). Polymerin proved to be composed of carbohydrates (52.40 mg 100(-1), w/w), melanin (26.14 mg 100(-1)), and proteins (10.40 mg 100(-1)), and the respective composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (11.06 mg 100(-1)), mainly K(+) and, to a lesser extent, Na(+), Ca(2+), Mg(2+), Zn(2+), Fe(3+), and Cu(2+), which were naturally bound and chelated through carboxylate anions and other characteristic nucleophilic functional groups naturally occurring in polymerin. The distribution of polymerin relative molecular size was assessed to be approximately between 500.0 and 2.0 kDa by calibrated molecular weight gel filtration chromatography, indicating also that a fraction consisted of protein, melanin, and polysaccharide, strongly aggregated to each other in a supramolecular status by a combination of covalent and hydrogen bonds and CH/Pi interactions, and another fraction of only free polysaccharide. Polymerin was transformed into a potassium salt deglycosylated derivative, named KSDpolymerin, which was also characterized by chemical analysis, DRIFTS, and AAS. KSDpolymerin consisted of carbohydrates (6.00 mg 100(-1)), melanin (52.49 mg 100(-1)), and proteins (35.40 mg 100(-1)), and the composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (6.11 mg 100(-1)), mainly K(+) and to a lesser extent Na(+), Ca(2+), Mg(2+), Zn(2+) and Fe(3+), bound as in polymerin. All the organic components were strongly linked in a supramolecular aggregate status and the relative average molecular size proved to be 6.3 kDa. Finally, we briefly discuss the possible use of such polymerins in agriculture as bioamendments and macro- and microelement biointegrators and as a biofilter for toxic metal removal, in light of their similarity with humic acids.     

Potential Use of Olive Mill Wastewater as Amendment: Crops Yield and Soil Properties Assessment

The traditional olive oil extraction process generates a large amount of liquid by-product that could be recycled as an organic fertilizer. The aim of this 3-year field experiment was to assess the effects of olive mill wastewater (OMWW) application on yields of ryegrass, proteic pea, and clover crops and on soil properties. The following treatments were compared: OMWW at 80 m³ ha^?1 (80_OMWW), OMWW at 120 m³ ha^?1 (120_OMWW), and an unfertilized control (Contr).

The yields of ryegrass increased 40% and 41.6% compared to Contr, for 80_OMWW and 120_OMWW, respectively, while a significant enhancement was found at the lowest level of OMWW in proteic pea (27.0% increase). Clover showed a species-specific sensitiveness, but the OMWW applications increased the protein content 26.3% and 28.7% for 80_OMWW and 120_OMWW, respectively, in comparison with Contr.

The OMWW rates also enhanced the total organic content in the soil compared to the unfertilized control. At the end of the 3-year experiment, total extracted carbon and humified organic carbon were greater than the initial ones. The values of available phosphorus (P) and potassium (K) determined at the end of experiment in Contr were almost the same as those recorded at the beginning of the research, confirming that the increases found in 80_OMWW and 120_OMWW plots were due to the OMWW applications.

The findings suggest that repeated applications of OMWW could both sustain fodder crop performance and support soil fertility, with the possibility to recycle the organic amendment and reduce the risks of soil degradation.     

Heavy‐metal toxicity in plants 1. A crisis in embryo

Abstract

Heavy metals are often added indiscriminantly to soils in pesticides, fertilizers, manures, sewage sludges, and mine wastes, causing an imbalance in nutrient elements in soils. Heavy‐metal toxicity causes plant stress in various degrees dependent on the tolerance of the plant to a specific heavy metal. The objectives of this study were (i) to show that plant species and soils respond differently to heavy metals and (ii) to show the necessity for proper quantity and balance of heavy metals in soils for plant growth.

Three Fe‐inefficient and three Fe‐efficient selections of soybean, corn, and tomato were grown on two alkaline soils with Cu and Zn ranging from 14 to 340 and Mn from 20 to 480 kg/ha. Heavy‐metal toxicity caused Fe deficiency to develop in these plants. The Fe‐inefficient T3238fer tomato and ys₁/ys₁ corn developed Fe deficiency on all treatments and both soils. T3238FER tomato (Fe‐efficient) did not develop heavy metal toxicity symptoms on any treatment or soil. The soybean varieties and WF9 corn were intermediate in their response.

The unpredictable response of both the soil and the plant to heavy metals make general recommendations difficult. In order to maintain highly productive soils, we need to know what we are adding to soils and the consequences. Without some control, the continued addition of heavy metals to soils is a crisis in embryo.     

废水污泥生物炭对圣女果生长、产量及重金属累积效应的对比评估

To investigate the potential effects of wastewater sludge and sludge biochar on growth, yield and metal bioaccumulation of cherry tomato ({\it Lycopersicon esculentum} L.), a pot experiment was carried out under greenhouse environment with three different treatments, control soil (CP), soil with wastewater sludge (SS) and soil with sludge biochar (SB), to reveal the comparative effect between the amendments of wastewater sludge and sludge biochar.~The soil used for pot experiment was Chromosol.~Wastewater sludge and sludge biochar produced through pyrolysis process at 550 $^\circ$C were applied at 10 t ha$^{-1}$. No significant difference was found in growth and production of cherry tomatoes between wastewater sludge and sludge biochar applications to the soil. The accumulation rates of metals in the fruits were lower in the treatment with sludge biochar than in the treatment with wastewater sludge. The study highlights the benefits of risk mitigation from toxic metal accumulation in fruits using wastewater sludge and sludge biochar as soil conditioners.     

The Influence of Heavy Metals on Carbon Dioxide Evolution from a Typic Xerochrept Soil

In a laboratory study the effects on soil respiration of trace metals (Ni, Cd, Cu, Mn, Pb, Zn)added at loading rates ranging from 0 to 1000 µg g-1 were determined. Differences intoxicity with respect to the type of metal salt added were also evaluated. The inhibitory effect onsoil respiration differed considerably among the heavy metals and increased with the increasingloading rate. No linear relationships were found between the degree of inhibition and the levels oftotal and available metals. Toxicity evaluation at 20 and 50% inhibition of soil respiration showedCu as the most toxic and Mn as the most tolerable metal. A ‘metal equivalent’ was calculated asthe sum of the amounts of the available metals weighted to their relative toxicity with respect tothe least toxic one: Mn equivalent = Mn + 1.9Pb + 2.1Ni + 2.5Zn + 6.7Cd + 6.7Cu. The ionicpotential of the heavy metals was found to be positively related to the percent inhibition of soilrespiration. Chlorides and sulphates appeared to depress soil respiration more than nitrates, thelatter counter-balancing the toxic effect of the heavy metals.     

Role of Soil Properties in Phytoaccumulation of Uranium

A pot study was conducted to investigate the toxiceffects of certain heavy metals on the plant growth and grainyield of wheat (Triticum aestivum L.). The resultsrevealed that heavy metals brought about significant reductionsin both parameters, Cd being the most toxic metal followed by Cu,Ni, Zn, Pb and Cr. Moreover, the presence of Cd in the soilresulted in the maximum inhibition (84.9%) in the number of freeliving Azotobacter chroococcum cells over the control. Thephytotoxicity was apparently due to the susceptibility of thefree living Azotobacter chroococcum cells to the toxicdoses of heavy metals.Protein content decreased from 19.0–71.4% in metal exposedplants at metal concentrations equivalent to those found inpolluted soil. Metal uptake by grains was directly related tothe applied heavy metal with greater concentrations of metalsfound in cases where metals were added separately rather than incombinations. The toxic effects on the plant growth, nitrogencontent in plant parts, and protein content in grains, exerted bytwo metals in combination were not additive, but rather only assevere as for the most toxic metal alone.     

Antioxidant activity of oregano, parsley, and olive mill wastewaters in bulk oils and oil-in-water emulsions enriched in fish oil

The antioxidant activity of oregano, parsley, olive mill wastewaters (OMWW), Trolox, and ethylenediaminetetraacetic acid (EDTA) was evaluated in bulk oils and oil-in-water (o/w) emulsions enriched with 5% tuna oil by monitoring the formation of hydroperoxides, hexanal, and t-t-2,4-heptadienal in samples stored at 37 degrees C for 14 days. In bulk oil, the order of antioxidant activity was, in decreasing order (p < 0.05), OMWW > oregano > parsley > EDTA > Trolox. The antioxidant activity in o/w emulsion followed the same order except that EDTA was as efficient an antioxidant as OMWW. In addition, the total phenolic content, the radical scavenging properties, the reducing capacity, and the iron chelating activity of OMWW, parsley, and oregano extracts were determined by the Folin-Ciocalteau, oxygen radical absorbance capacity, ferric reducing antioxidant power, and iron(II) chelating activity assays, respectively. The antioxidant activity of OMWW, parsley, and oregano in food systems was related to their total phenolic content and radical scavenging capacity but not to their ability to chelate iron in vitro. OMWW was identified as a promising source of antioxidants to retard lipid oxidation in fish oil-enriched food products.     

A comparative analysis of element composition of roots and leaves of barley seedlings grown in the presence of toxic cadmium,molybdenum, nickel,and zinc concentrations 1

Barley seedlings were grown in hydroponic culture in the presence of toxic concentrations of cadmium (Cd), molybdenum (Mo), nickel (Ni), and zinc (Zn) and analyzed for element composition [boron (B), calcium (Ca), Cd, iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), and Zn]. In a first survey, heavy metal concentrations were selected which resulted in a similar inhibition of root growth. Toxic concentrations of Cd, Mo, Ni, and Zn revealed both similar and distinct effects on specific leaf and root element contents. Examples for such responses were decreasing contents in root Mn and Mg at elevated levels of all heavy metals, including Mo, in the medium. In contrast, changes in root contents of B were specific for the applied type of heavy metal stress. The heavy metal dependent changes in B, Ca, Mg, and Mn contents were studied in more detail. In some cases, severe heavy metal toxicity caused excessive accumulation or depletion of nutrient elements that may be deleterious to the plants in addition to other primary damages caused by the heavy metal ions.     

Toxicity and binding of copper,zinc, and cadmium by the blue-green alga,Chroococcus paris

The toxic effects and accumulation of the heavy metals, Cd, Cu, and Zn by the sheath forming blue-green alga Chroococcus paris were investigated. All three of the metals were bound rapidly. Approximately 90% of the total amount of the added metal was bound within 1 min. Further significant binding occurred at a slower rate. The maximum metal binding capacity, as determined by filtration studies, was determined to be 53, 120, and 65 mg g^?1 dry algal weight for Cd, Cu, and Zn, respectively. Binding curves for the metals followed the Langmuir adsorption isotherm model. The amount of metal bound increased with increasing pH. Metal binding increased significantly when pH was increased from 4 to 7. Nearly all of the metal was found to be rapidly EDTA extractable. Metals were found to be increasingly toxic to growing cultures in the order, Zn, Cd, and Cu. All of the metals studied exhibited toxic effects at concentrations greater than 1.0 mg L^?1. The lowest concentrations used which showed detectable toxicity were 0.1 mg L^?1 for Cu and >0.4 mg L^?1 for Cd and Zn.     

重金属复合处理对小麦锌铜镍镉积累和分布的影响

为增加粮食可食用部分有益元素的浓度,同时减少有毒重金属元素的含量,需要更好地了解元素在植株和籽粒内的运输和分布。在温室盆栽条件下,以春小麦为供试材料,设置对照（不添加重金属）和重金属复合处理（同时添加铜、锌、镍、镉,以不影响小麦生长为前提）,研究锌（Zn）、铜（Cu）、镍（Ni）、镉（Cd）在成熟植株和籽粒不同部位的分布特点。结果表明,重金属复合处理对小麦成熟期籽粒和秸秆产量、收获指数以及粒重均无显著影响,但使小麦各器官重金属浓度均显著增加,增幅因不同器官和不同元素而异,籽粒中Zn、Cu、Ni和Cd浓度分别增加1.8、0.5、48.1倍和45.3倍。重金属复合处理还显著改变了Zn和Ni在地上部各器官中的分配模式：对照小麦吸收的Zn更易向生殖器官中转运,处理植株则更多地滞留在营养器官中,而Ni呈相反的趋势。激光剥蚀电感耦合等离子体质谱仪（LA-ICP-MS）对籽粒糊粉层和胚乳的定量分析表明,重金属复合处理使糊粉层Zn和Cu浓度仅增加了78%和86%,而糊粉层Ni和Cd浓度分别增加了30倍和121倍。重金属复合处理使胚乳Zn和Cu浓度分别增加了49%和48%,使Ni和Cd浓度均超出小麦标准中Ni和Cd的最大允许浓度（对照籽粒胚乳中没有检验到Ni和Cd）。以上结果表明,在小麦生物强化实践中,在增加有益营养元素（如Cu和Zn）的同时亦存在有毒重金属（如Ni和Cd）超标的巨大风险。     

Adsorption of Toxic Metals on Modified Polyacrylonitrile Nanofibres: A Review

Removal of toxic metals from aqueous solutions is of high priority in environmental chemistry. Most of the available techniques for this task are considered expensive; however, the adsorption process has been considered the easiest and the cheapest way of removing toxic metals from aqueous solution. The performance of adsorption setup largely depends on the characteristic of adsorbents. One of these characteristic is availability of large surface area. The more the available sites for chelation, the more the amount of metals removed. Therefore, the production of materials of nanoscale is expedient for adsorption purposes. Electrospinning process is one of the technologies that have been employed to produce polyacrylonitrile nanofibres (PAN-nfs). Moreover, PAN-nfs surfaces have also been chemically modified so as to introduce chelating groups such as amine, carboxyl, imines, etc. Here we review PAN-nfs as metal ion adsorbent. With characteristics such as high surface area as well as good mechanical strength, modified PAN-nfs are considered good adsorbents and have been used to remove toxic metals such as cadmium, lead, chromium, mercury, uranium, silver and copper in different ion states from their aqueous solutions. The ease of immobilization of metal-specific ligands on PAN-nfs has been of great interest in selective extraction of metal ions from their aqueous solutions. Also, toxic metals adsorbed on modified PAN-nfs can be recovered through desorption process using acids or bases of various concentrations.     

Effects of metals on the germination and growth of fungal isolates from New Caledonian ultramafic soils

Soils of New Caledonian mining areas have relatively high metal contents. Two ultramafic soils rich in extractable Mn, Fe, Ni and Co and two agricultural soils with much lower concentrations of metals were compared through different experiments. Microbial population numbers and their tolerance to Mn²⁺ and Ni²⁺ were estimated. The effect of five metals (Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺ and Mg²⁺) upon spore germination and mycelial growth was investigated for fungi isolated from the two types of soils. Nickel appeared to be the most toxic metal, but the other metals also had inhibitory effects at concentrations similar to those which occur in ultramafic soils. Spore germination was more sensitive to metals than mycelial growth. The toxic effects of the five metals were not cumulative when mixed together into the medium; antagonism between ions, partly neutralizing their effects may account for this. Fungal isolates from ultramafic soils appeared to be more tolerant to metals than those from agricultural soils. Some ultramafic soil isolates appeared to actually require the presence of metals, with their growth being stimulated by relatively high concentrations of these elements. Two fungal isolates of genera which are often common in agricultural soils (i.e. Curvularia and Fusarium), and which are not present in New Caledonian ultramafic soils were also tested. Curvularia was more sensitive to the five metals than all the other isolates and Fusarium was particularly inhibited by Ni²⁺. However, a proportion of the spores of each isolate was able to germinate and to grow moderately well in the presence of relatively high metal concentrations. Their absence from ultramafic soils is thought to result from their elimination by competitors that are more tolerant to metals.     

Metals in urban soils of Sevilla: seasonal changes and relations with other soil components and plant contents

Soils of the urban area of Sevilla have been scarcely studied, especially concerning their concentrations of potentially toxic metals. A previous paper has shown that moderate pollution exists in soils from some public green areas of the city, and a common pattern was found in the distribution of the concentrations of some particular metals. The present paper is aimed at (i) determining possible seasonal changes in the measured concentrations; (ii) checking possible effects of the observed pollution on plant metal contents, and (iii) finding possible relations between metals by statistical techniques. Samples of 35 soils from the urban area of Sevilla were studied. Comparison with previous data shows that samples from a depth of 0–20 cm are representative of the measured soil properties for the city. We show that in most cases differences in the EDTA‐ and aqua regia‐extractable metal contents between autumn 2000 and summer 2001 are not significant. Only Zn shows significant decreases (P < 0.05), probably because it is more mobile than the other metals studied. Electrical conductivity and pH also show significant changes related to leaching of soluble salts. We found a strong association between ‘urban’ metals (as defined in the literature) and organic matter, as shown by factor analysis, whereas ‘non‐urban’ metals could be related to clay and carbonate contents, perhaps coming from the soil parent materials. The behaviour of the urban metals means that organic matter contributes to their accumulation, either by retention of the incoming metals from the atmosphere, dust or various human activities, or from addition of organic amendments that might provide significant amounts of such metals. Although concentrations of Cu, Pb and Zn at several sites exceeded the limits established elsewhere as acceptable in residential areas, the values in the grass were less than those considered as normal in the literature. This implies that fairly large concentrations in the soil do not necessarily make metals more available.     

Amendment Type and Dose Effects onto Coexisting Copper,Lead, and Nickel Ions Distribution in Soil

The use of soil additives for toxic metals chemical stabilization aims to decrease in situ the pollutants’ mobility and availability. In this study, the effectiveness of rinsed red mud (RBRM) and annealed animal bones (B400) was compared in terms of Cu, Pb and Ni stabilization in two contaminated soils with contrasting properties Dystric Cambisol (CM dy) and Rendzic Leptosol (LP rz). The mobility of metals in unamended soil samples (control) and samples amended with 1% and 5% of selected additives were compared using sequential extraction protocol. The relative content of metals in readily and potentially available fractions was higher in CM dy (62% Pb, 13% Cu, and 31% Ni in exchangeable fraction) than in LP rz (<?5% of Pb, Cu, Ni in exchangeable fraction). In CM dy, both additives have caused a decrease in metal mobility with an increase of their doses. The effect of 5% sorbent addition was most pronounced related to Pb immobilization, provoking decrease of exchangeable Pb content to <?10%. Furthermore, B400 addition has redistributed investigated metals from the exchangeable to the residual phase more effectively than RBRM, and its effect on metal mobility decreased in the order Pb?>?Cu?>?Ni. Amending of LP rz soil had limited effects with no apparent decrease in exchangeable metal content. The effects of soil type variation, the type of additive and the additive dose onto metal mobility were compared according to ANOVA results. The content of readily and potentially available forms of metals was found to be (i) significantly correlated with all investigated variables for Pb, (ii) significantly correlated with soil type for Cu, and (iii) not in significant correlation with selected variables for Ni. Complex impacts of soil properties and treatment conditions on the mobility of co-contaminants emphasize the need for an individual approach to each case of contamination.     

Microbial Communities in Long-Term Heavy Metal Contaminated Ombrotrophic Peats

High concentrations of heavy metals are known to be toxic to many soil organisms. The effects of long-term exposure to lower levels of metals on the soil microbial community are, however, less well understood. The southern Pennines of the U.K. are characterised by expanses of ombrotrophic peat soils that have experienced deposition of high levels of heavy metals since the mid to late 1800s. Concentrations of metals in the peat remain high but the effect of the contamination on the in-situ microbial communities is unknown. Geochemical and molecular polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing techniques were used to derive new information on the metal chemistry and microbial populations in peat soils from six locations in the southern Pennines. All sites were highly acidic (pH 3.00–3.14) with high concentrations of potentially toxic heavy metals, particularly porewater Zn and particulate-associated Pb. The results also reveal a split in site characteristics between the most polluted sites with the highest levels of bioavailable metals (Bleaklow, FeatherBed Moss and White Hill) and those with much lower bioavailable metals (Cowms Moor, Holme Moss and Round Hill). There was no difference in the number of dominant bacterial species between the sites but there were significant differences in the species composition. At the three sites with the highest levels of bioavailable metals, bacterial species with a high similarity to acidophilic sulphur- and iron-oxidizing bacteria and those from high metal environments were detected. The transformations carried out by these metal mobilising and acid producing bacteria may make heavy metals more bioavailable and therefore more toxic to higher organisms. Bacteria with similarity to those typically found in forest and grassland soils were documented at the three sites with the lowest levels of bioavailable metals. The data highlight the need for further studies to elucidate the species diversity and functionality of bacteria in heavy metal contaminated peats in order to assess implications for moorland restoration.     

Emerging resistant microbiota from an acidic soil exposed to toxicity of Cr, Cd and Pb is mainly influenced by the bioavailability of these metals

Purpose

The effect of pollutants in soil microorganisms is an important issue in order to understand their toxic effects in the environment, as well as for developing adequate bioremediation strategies. In this sense, the main objective of this study was to assess the involvement of the indigenous microbiota of an acidic forest Mediterranean soil by artificial pollution with heavy metals, and to detect and isolate resistant microorganisms that could be useful for bioremediation.

Materials and methods

Samples from a previously unpolluted acidic forest soil were amended with Cr(VI), Cd(II) or Pb(II) at total amounts ranging from 0.1 to 5,000 mg?kg^?1. These soil microcosms were incubated under controlled laboratory conditions for 28 days. Soluble fractions of metals were determined from aqueous extracts. Both activity and composition of the microbial community were assessed, respectively, by respirometric assays and molecular analysis (polymerase chain reaction denaturing gradient gel electrophoresis). The isolation of metal-resistant microorganisms was attempted by culture plating from microcosms incubated with high concentrations of metals. Isolated strains were tested in cultures with minimal medium to check for their metal resistance and their capacity to reduce the presence of toxic Cr(VI).

Results and discussion

A decrease in the soil respirometric activity and changes in the microbial community composition were detected from 10/100 mg?kg^?1 Cr and 1,000 mg?kg^?1 Cd and Pb. Presumably resistant bacterial and fungal populations developed in most of these polluted microcosms; however, the microbiota was severely impaired at the highest additions of Cr. Even though Cr was the most damaging metal in soil microcosms, if the soluble fractions of metals are considered instead of their total added amounts, the comparison among their toxic effects suggests a similar potential toxicity of Cr and Pb. Isolated multiresistant microorganisms were related mainly to Actinobacteria, Firmicutes and Ascomycota. Some of them showed the capacity to reduce Cr(VI) concentrations between 54 % and 70 % of the initial value. These strains were affiliated to several species of Streptomyces and Bacillus.

Conclusions

The combination of respirometric assays with molecular methods has been useful to assess the effect of metals on the soil microbial community, which can greatly be explained by their differential bioavailability. Cultivation-dependent and -independent approaches have proved the presence and development of multiresistant microorganisms in a previously unpolluted soil. Due to their properties, some of the isolated strains are potentially useful for soil bioremediation.     

小麦根际Cr(Ⅵ)的还原

Reduction of Cr(Ⅵ) to Cr(Ⅲ) was studied in a fresh wheat rhizosphere soil (kuroboku, high humic Andosol) pretreated with a basal fertilizer consisting of (NH₄)₂SO₄, P₂O₅ and KH₂PO₄ and with K₂Cr₂O₇ by using a rhizobox system. The rhizosphere exerted a positive effect on Cr(Ⅵ) reduction. Part of the reason was the decrease of pH in the rhizosphere due to application of (NH₄)₂SO₄, implying that application of physiologically acid fertilizers would reduce Cr(Ⅵ) toxicity to plants.     

Bioaccumulation and Distribution of Lead,Zinc, and Cadmium in Crops of Solanaceae Family

Comparative research has been carried out to determine the quantities and accumulation of lead (Pb), zinc (Zn), and cadmium (Cd) in the vegetative and reproductive organs of crops of the Solanaceae family (tomato, pepper, and aubergine) as well as to identify the possibilities of growing them on soils contaminated by heavy metals. The analyses were carried out by inductively coupled plasma–atomic emission spectrometry after dry ashing. Heavy metals have an impact on the development and productivity of the crops of the Solanaceae family. The high anthropogenic contamination impedes the normal development and fruit‐bearing ability of the pepper and aubergine plants, and in the case of tomatoes, it led to an increased assimilation of heavy metals without reducing the yield and the quality of the production of tomatoes. Crops from the Solanaceae family, tomato, pepper, and aubergine plants, could be cultivated on soils having low and medium levels of contamination of heavy metals, because they do not show a tendency to accumulating Pb, Zn, and Cd in their fruits, which could still be used for consumption.     

施肥方式对滴灌加工番茄干物质积累、养分吸收和产量的影响

通过加工番茄大田试验,研究了不同施肥方式下,膜下滴灌加工番茄的干物质积累与养分吸收规律及产量构成。结果表明,在滴灌追施100%氮肥和初果期之后滴灌追施70%钾肥的基础上,基施65%磷肥和初果期之前滴灌追施35%磷肥(优化处理)比100%磷肥基施的加工番茄干物质增加11.51%,产量提高3.59%,氮、磷、钾肥的利用率分别增加了6.06、4.15和5.26个百分点。氮肥和磷肥在初果期之前滴灌追施,氮肥和钾肥在初果期之后滴灌追施的滴灌配方肥处理的产量显著低于优化处理,且优化处理的肥料效益也好于滴灌配方肥处理。加工番茄在初果期之前滴灌追施氮与磷,在初果期之后滴灌追施氮与钾可以提高加工番茄产量,增加肥料利用效率。     

云南滇池沉积物中重金属的形态分布特征

Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.