The role of radial oxygen loss and root anatomy on zinc uptake and tolerance in mangrove seedlings

Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the ‘tightest barrier’ in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings.     

Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L⁻¹) and a soil pot trail (control, 60 mg As kg⁻¹). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O₂ kg⁻¹ root d.w. d⁻¹), As uptake (e.g., 8.8-151 mg kg⁻¹ in shoots in 0.8 mg As L⁻¹ treatment), translocation factor (2.1-47% in 0.8 mg As L⁻¹) and tolerance (29-106% in 0.8 mg As L⁻¹). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity.     

Effects of As levels on radial oxygen loss and As speciation in rice

Greenhouse experiment was conducted to examine effects of arsenic (As) on iron plaque formation, radial oxygen loss, As accumulation, and speciation in rice. Three genotypes were grown in soil with three different concentrations of As. The stress of As caused a slight increase of iron plaque formation (P?>?0.05) and a decrease in the rates of radial oxygen loss (ROL; P?<?0.01). The results of As speciation showed that the percentages of DMA increased from 19–28 % to 53–58 %, while the percentages of inorganic As decreased from 53–58 % to 36–42 % with the increasing soil As concentrations, indicating a strong environmental influence on As species in rice grain. The present study showed that elevated soil As may induce As toxicity towards rice plants, leading to the decrease of ROL; environmental factors could influence As methylation or As species transportation. Our study provided useful information on As tolerance and accumulation in rice which may contribute to reducing the health risk posed by As contamination in rice.     

Effects of root anatomy and Fe plaque on arsenic uptake by rice seedlings grown in solution culture

Hydroponic experiments were carried out to investigate the effects of root anatomy, induced by aeration and stagnation, and Fe plaque on arsenic (III&V) uptake and translocation by rice plants. The results showed that As uptake in rice plants (Gui Chao-2) treated by aeration was decreased due to lower root specific surface area. Rice roots with larger specific surface area tended to form more Fe plaque, and Fe plaque affected As uptake kinetics by changing As influx curves from linear to hyperbolic for As(III) and from hyperbolic to S-curve for As(V). Fe plaque increased As(III&V) adsorption and minimized the effects of root anatomy characteristics on As uptake into roots and subsequently translocation to shoots. Fe plaque increased As(III) uptake rate at As(III) concentrations of 0.5∼8 mg L⁻¹, reduced As(V) uptake rate at low As(V) concentrations (<2 mg L⁻¹), but increased As uptake rate at high As(V) concentrations (>6 mg L⁻¹).     

The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings

A historically multi-metal contaminated soil was amended with biochars produced from different parts of rice plants (straw, husk and bran) to investigate how biochar can influence the mobility of Cd, Zn, Pb and As in rice seedlings (Oryza sativa L.). Rice shoot concentrations of Cd, Zn and Pb decreased by up to 98%, 83% and 72%, respectively, due to biochar amendment, though that of As increased by up to 327%. Biochar amendments significantly decreased pore water concentrations (C_pw) of Cd and Zn and increased that of As. For Pb it depended on the amendment. Porewater pH, dissolved organic carbon, dissolved phosphorus, silicon in pore water and iron plaque formation on root surfaces all increased significantly after the amendments. The proportions of Cd and Pb in iron plaque increased by factors 1.8-5.7 and 1.4-2.8, respectively; no increase was observed for As and Zn. Straw-char application significantly and noticeably decreased the plant transfer coefficients of Cd and Pb. This study, the first to investigate changes in metal mobility and iron plaque formation in rice plants due to amending a historically contaminated soil with biochar, indicates that biochar has a potential to decrease Cd, Zn and Pb accumulations in rice shoot but increase that of As. The main cause is likely biochar decreasing the C_pw of Cd and Zn, increasing the C_pw of As, and increasing the iron plaque blocking capacity for Cd and Pb.     

The relationship of root porosity and radial oxygen loss on arsenic tolerance and uptake in rice grains and straw

The correlations among arsenic (As) accumulation in grains and straw, rates of radial oxygen loss (ROL), and porosity of roots using 25 rice cultivars were investigated based on two pot experiments: (1) soil with addition of 100 mg As kg^?1 for analysis of As in grains and straw, and (2) deoxygenated solution for analyzing rates of ROL and porosity of roots. The results showed that there were great differences in grain As (0.71–1.72 mg kg^?1) and straw As (15.6–31.7 mg kg^?1), rates of ROL (7.40–13.24 mmol O₂ kg^?1 root d.w. h^?1), and porosity (20.91–33.08%) among the cultivars. There were significant negative correlations between As in grains or straw and ROL and porosity, and significant positive correlations between rates of ROL and porosities, respectively. Rice cultivars with high porosities tended to possess higher rates of ROL, and had higher capacities for limiting the transfer of As to aboveground tissues.     

Lead accumulation and association with Fe on Typha latifolia root from an urban brownfield site

Synchrotron X-ray microfluorescence and X-ray absorption near-edge microstructure spectroscopy techniques were applied to Typha latifolia (cattail) root sections and rhizosphere soils collected from a brownfield site in New Jersey to investigate lead (Pb) accumulation in T. latifolia roots and the role of iron (Fe) plaque in controlling Pb uptake. We found that Pb and Fe spatial distribution patterns in the root tissues are similar with both metals present at high concentrations mainly in the epidermis and at low concentrations in the vascular tissue (xylem and phloem), and the major Pb and Fe species in T. latifolia root are Pb(II) and Fe(III) regardless of concentration levels. The sequestration of Pb by T. latifolia roots suggests a potential low-cost remediation method (phytostabilization) to manage Pb-contaminated sediments for brownfield remediation while performing wetland rehabilitation.     

Effects of perchlorate on growth of four wetland plants and its accumulation in plant tissues

Perchlorate contamination in water is of concern because of uncertainties about toxicity and health effects, impact on ecosystems, and possible indirect exposure pathways to humans. Therefore, it is very important to investigate the ecotoxicology of perchlorate and to screen plant species for phytoremediation. Effects of perchlorate (20, 200, and 500 mg/L) on the growth of four wetland plants (Eichhornia crassipes, Acorus calamus L., Thalia dealbata, and Canna indica) as well as its accumulation in different plant tissues were investigated through water culture experiments. Twenty milligrams per liter of perchlorate had no significant effects on height, root length, aboveground part weight, root weight, and oxidizing power of roots of four plants, except A. calamus, and increasing concentrations of perchlorate showed that out of the four wetland plants, only A. calamus had a significant (p?<?0.05) dose-dependent decrease in these parameters. When treated with 500 mg/L perchlorate, these parameters and chlorophyll content in the leaf of plants showed significant decline contrasted to control groups, except the root length of E. crassipes and C. indica. The order of inhibition rates of perchlorate on root length, aboveground part weight and root weight, and oxidizing power of roots was: A. calamus > C. indica > T. dealbata > E. crassipes and on chlorophyll content in the leaf it was: A. calamus > T. dealbata > C. indica > E. crassipes. The higher the concentration of perchlorate used, the higher the amount of perchlorate accumulation in plants. Perchlorate accumulation in aboveground tissues was much higher than that in underground tissues and leaf was the main tissue for perchlorate accumulation. The order of perchlorate accumulation content and the bioconcentration factor in leaf of four plants was: E. crassipes > C. indica > T. dealbata > A. calamus. Therefore, E. crassipes might be an ideal plant with high tolerance ability and accumulation ability for constructing wetland to remediate high levels of perchlorate polluted water.     

Remediation of acid mine drainage (AMD)-contaminated soil by Phragmites australis and rhizosphere bacteria

Experiments were conducted to assess the impact of citric acid (CA) and rhizosphere bacteria on metal uptake in Phragmites australis cultured in a spiked acid mine drainage (AMD) soil. Rhizosphere iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque on roots, which decreased the uptake of Fe and Mn. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque, raised the metal mobility in soil, and increased the accumulation of metals in all tissues of the reeds. The higher the CA dosage, the more metals accumulated into reeds. The total amount of metals in reeds increased from 7.8?±?0.5?×?10^?6 mol plant^?1 (Mn), 1.4?±?0.1?×?10^?3 mol plant^?1 (Fe), and 1.0?±?0.1?×?10^?4 mol plant^?1 (Al) in spiked soil without CA to 22.2?±?0.5?×?10^?6 mol plant^?1 (Mn), 3.5?±?0.06?×?10^?3 mol plant^?1 (Fe), and 5.0?±?0.2?×?10^?4 mol plant^?1 (Al) in soil added with 33.616 g C₆H₈O₇·H₂O for per kilogram soil. CA could be effective at enhancing the phytoremediation of metals from AMD-contaminated soil.     

Response of Holm oak (Quercus ilex subsp. ballota) and mastic shrub (Pistacia lentiscus L.) seedlings to high concentrations of Cd and Tl in the rhizosphere

The impairment of root growth and photosynthetical functioning are the main impacts of trace elements on woody plant seedlings. In this work, we assessed the response of Holm oak (Quercusilex subsp. ballota) and mastic shrub (Pistacia lentiscus) seedlings to high concentrations of Cd and Tl in the rhizosphere. These are non-essential trace elements, with a potential high mobility in the soil-plant system. Seedlings of these species are frequently used in the afforestation of degraded soils in mining areas. Plants were exposed to different levels of Cd (20, 80 and 200 mg L⁻¹) and Tl (2, 10 and 20 mg L⁻¹) in a sand culture. Biomass allocation, growth rates, chlorophyll fluorescence and gas exchange were studied. Both metals affected root biomass. Cadmium produced an increase in the root mass ratio and a decrease in the specific leaf area of the plants in oak seedlings, while Tl did not provoke such response. Mastic plants were more sensitive to Tl and Cd than oak plants. Between elements, Tl provoked more severe toxic effects in the plants, affecting the antennae complexes and reaction centers of the photosystem II. Both elements decreased net assimilation rates (down to a 20% of the control plants) and stomatal conductance (5-10% of the values for the control plants). Cadmium was highly retained in the roots of both species, while Tl was highly translocated into the leaves. In general, Holm oak showed a higher tolerance for Cd than for Tl, and a higher resistance to both metals than mastic shrub, due to a high capacity for Cd retention at the root level. However, such accumulation in roots may induce water stress in the seedling exposed to Cd.     

Evaluation of olive oil mill wastewater toxicity on spinach

Background, aim, and scope

Olive oil mill wastewater (OMW), a by-product of the olive oil extraction process, is annually produced in huge amounts in olive-growing areas and represents a significant environmental problem in Mediterranean areas. We studied the impact of OMW dilutions (1:20 and 1:10) on spinach plants in order to evaluate OMW dilutions as a low-cost alternative method for the disposal of this waste.

Materials and methods

The effects of OMW dilutions were evaluated on seed germination, shoot and root elongation, biomass production, nutrient uptake and translocation, ascorbic acid content, polyphenols, photosynthetic pigments, and photosynthetic performance of spinach.

Results

Plant biomass was more affected than plant height and total chlorophyll; carotenoid and ascorbic acid content progressively decreased with decreasing OMW dilution. Exposure to both OMW dilutions resulted in overaccumulation of total polyphenols, which were negatively correlated to plant biomass and nutrients. Nutrient (Fe, Ca, and Mg) content was insufficient leading to reduced growth. Water use efficiency decreased mainly due to decreased CO₂ assimilation rate rather than to a decline of transpiration rate. Disturbances in photosystem II (PSII) photochemical efficiency could be better envisaged by the ratio between variable fluorescence and initial fluorescence (Fv/Fo), which showed much greater amplitude than the maximal photochemical efficiency of PSII photochemistry (Fv/Fm).

Conclusions

From the data obtained, it is suggested that 1:20 OMW dilutions are still phytotoxic and that higher OMW dilutions should be used in order to use this waste for the irrigation of spinach plants.     

Comparative quantification of oxygen release by wetland plants: electrode technique and oxygen consumption model

Understanding oxygen release by plants is important to the design of constructed wetlands for wastewater treatment. Lab-scale systems planted with Phragmites australis were studied to evaluate the amount of oxygen release by plants using electrode techniques and oxygen consumption model. Oxygen release rate (0.14 g O₂/m²/day) measured using electrode techniques was much lower than that (3.94–25.20 gO₂/m²/day) calculated using the oxygen consumption model. The results revealed that oxygen release by plants was significantly influenced by the oxygen demand for the degradation of pollutants, and the oxygen release rate increased with the rising of the concentration of degradable materials in the solution. The summary of the methods in qualifying oxygen release by wetland plants demonstrated that variations existed among different measuring methods and even in the same measuring approach. The results would be helpful for understanding the contribution of plants in constructed wetlands toward actual wastewater treatment.     

光催化氧化-Fenton组合方法降解高浓度正丙醇废水

研究了1%和10%2种浓度正丙醇废水在光催化氧化-Fenton组合工艺条件下的降解情况,分别考察了H2O2加药方式及剂量、Fe2+浓度、TiO2浓度,以及废水的初始浓度对反应的影响,得到了优化工艺参数。结果显示,在23 W的低压汞灯照射下,当Fe2+离子浓度为0.44 g/L,TiO2为0.4 g/L,H2O2分6次等幅递增投加,增幅为均值的10%,投加总量至28.6 g/L时,反应6 h后,组合工艺可将1%浓度正丙醇废水的COD从17 200 mg/L降低至2 000 mg/L。H2O2总用量为136.5 g/L,其他条件及加药方式不变条件下,废水浓度提高至10%,紫外光能量利用率明显提高,反应15 h后,可将COD从172 000 mg/L降至1 000 mg/L以下,降解速率随浓度降低而下降。     

Root responses to soil Ni heterogeneity in a hyperaccumulator and a non-accumulator species

We compared root responses of the Ni-hyperaccumulator plant Berkheya coddii Rossler with the non-accumulator plant Cicer arietinum L. to Ni heterogeneity in soil. We grew plants in growth containers filled with control soil, homogeneously spiked, and heterogeneously spiked soil with Ni concentrations of 62 and 125 mg kg^?1. Neutron radiography (NR) was used to observe the root distribution and the obtained images were analysed to reveal the root volumes in the spiked and unspiked segments of the growth container. There was no significant difference in root distribution pattern of B. coddii among different concentrations of Ni. Unlike B. coddii, the roots of C. arietinum initially grew into the spiked segments. However, the later developing roots did not penetrate the spiked segment suggesting an avoidance strategy. Our results indicate that, B. coddii does not forage towards the Ni-rich patches, although presence of Ni in soil changes its root morphology.     

Characterization of heavy metal-resistant endophytic bacteria from rape (Brassica napus) roots and their potential in promoting the growth and lead accumulation of rape

Two lead (Pb)-resistant endophytic bacteria were isolated from rape roots grown in heavy metal-contaminated soils and characterized. A pot experiment was conducted for investigating the capability of the two isolates to promote the growth and Pb uptake of rape from Pb-amended soil. The two isolates were identified as Pseudomonas fluorescens G10 and Microbacterium sp. G16 based on the 16S rDNA gene sequence analysis. Strains G10 and G16 exhibited different multiple heavy metal and antibiotic resistance characteristics and increased water-soluble Pb in solution and in Pb-added soil. Root elongation assays demonstrated increases in root elongation of inoculated rape seedlings compared to the control plants. Strain G16 produced indole acetic acid, siderophores and 1-aminocyclopropane-1-carboxylate deaminase. Increases in biomass production and total Pb uptake in the bacteria-inoculated plants were obtained compared to the control. The two strains could colonize the root interior and rhizosphere soil of rape after root inoculation.     

强化内电解预处理制药废水

为进一步提高铁炭内电解法处理制药废水的处理效率,采用添加不同强化剂的方法考察分析强化因子的影响效果.在C加入量10g/L,铁屑30g/L,反应时间150 min,pH值7.5的条件下,以不同的盐、金属铜、双氧水作强化剂分别加入反应体系中,检测COD去除效果.实验结果表明:当每升废水中分别加入氯化铜、硫酸锰、硝酸镍、金属...     

Mutagenicity and genotoxicity assessment of industrial wastewaters

The genotoxicity of industrial wastewaters from Jajmau (Kanpur), was carried out by Ames Salmonella/microsome test, DNA repair-defective mutants, and Allium cepa anaphase–telophase test. Test samples showed maximum response with TA98 strain with and without metabolic activation. Amberlite resins concentrated wastewater samples were found to be more mutagenic as compared to those of liquid–liquid extracts (hexane and dichloromethane extracts). The damage in the DNA repair defective mutants in the presence of Amberlite resins concentrated water samples were found to be higher to that of liquid–liquid-extracted water samples at the dose level of 20 μl/ml culture. Among all the mutants, polA exhibited maximum decline with test samples. Mitotic index (MI) of root tip meristematic cells of A. cepa treated with 5, 10, 25, 50, and 100 % (v/v) wastewaters were significantly lower than the control. Complementary to the lower levels of MI, the wastewaters showed higher chromosomal aberration levels in all cases investigated.     

Effect of octylphenol on physiologic features during growth in Arabidopsis thaliana

Alkylphenol ethoxylates are widely used as detergents, emulsifiers, solubilizers, wetting agents and dispersants. Octylphenol (OP) ethoxylates, one of alkylphenol ethoxylates, represent 15–20% of the market, and their metabolic residues may be discharged to surface waters, sediments and soils as a persistent and ubiquitous pollutant. We tested the response of Arabidopsis thaliana to different concentrations of OP. OP affected the germination percentage and mean germination period. 10 d treatment with OP, especially high concentration (10 and 50 mg L⁻¹), decreased shoot and root biomass and root length of 30 d-old A. thaliana. Content of chlorophyll was decreased but that of proline was increased in leaves with OP treatment. OP caused oxidative stress in leaves; malondialdehyde content was increased, and the activities of ascorbate peroxidase, catalase and superoxide dismutase were induced. OP affects the physiologic and morphologic features of A. thaliana during growth. Because plants might be exposed to OP for a long time in the surroundings, more attention needs to be paid to the effect of OP on plants.     

The composition and relationships between trace element levels in inhalable atmospheric particles (PM10) and in leaves of Nerium oleander L. and Lantana camara L

In order to evaluate the composition of inhalable atmospheric particles and to study the relationship between trace element levels in PM10 and in leaves of two plant species, the amount of Ba, Cu, Fe, Mn, Pb, Ti and V were analysed in PM10 and in Nerium oleander L. and Lantana camara L. leaves from two sites in the city of Seville and one remote control site. In PM10, the Cu and Fe content was significantly lower (p<0.05) in the control site than in the other sites. No correlations between leaf content and air content were found for the elements in L. camara. On the contrary, positive and significant correlations (p<0.05) were found between leaf content of N. oleander and PM10 content for Cu and Fe. The data suggest that N. oleander can be used in atmospheric biomonitoring studies, because it is especially useful for Cu and Fe, N. oleander being a better indicator than L. camara.     

Occurrence and abundance of tetracycline,sulfonamide resistance genes,and class 1 integron in five wastewater treatment plants

To understand the transport and fate of antibiotic resistance genes in wastewater treatment plants, 12 resistance genes (ten tetracycline resistance genes, two sulfonamides genes) and class 1 integron gene (intI1) were studied in five wastewater treatment plants with different treatment processes and different sewage sources. Among these resistance genes, sulfonamides genes (sul1 and sul2) were of the most prevalent genes with detection frequency of 100 %. The effluent water contained fewer types of resistance genes than the influent in most selected plants. The abundance of five quantified resistance genes (tetG, tetW, tetX, sul1, and intI1) decreased in effluent of plants treating domestic or industrial wastewater with anaerobic/aerobic or membrane bioreactor (MBR) technologies, but tetG, tetX, sul1, and intI1 increased along the treatment units of plants treating vitamin C production wastewater by anaerobic/aerobic technology. In plant treating cephalosporins production wastewater by UASB/aerobic process, the quantities of tetG, tetX, and sul1 first decreased in anaerobic effluent water but then increased in aerobic effluent water.