Influence of environmental related concentrations of heavy metals on motility parameters and antioxidant responses in sturgeon sperm

The effects of heavy metals (Cd, Cr and Cd + Cr) on the motility parameters and oxidative stress of sterlet (Acipenser ruthenus) sperm were investigated in vitro. Sturgeon sperm were exposed for 2 h to heavy metals at environmental related concentrations (0.1 mg L^?1 Cr, 0.001 mg L^?1 Cd, 0.1 mg L^?1 Cr + 0.001 mg L^?1 Cd) and higher concentrations (5.0 mg L^?1 Cr, 0.05 mg L^?1 Cd, 5.0 mg L^?1 Cr + 0.05 mg L^?1 Cd). Results revealed that environmental concentrations of heavy metals had no significant influence on motility parameters and antioxidant responses indices in sturgeon sperm, except for LPO level and SOD activity. But higher concentrations of these metals induced oxidative tress in sturgeon sperm in vitro, associated with sperm motility parameters inhibition. Our results suggest that using of sperm in vitro assays may provide a novel and efficiently means for evaluating the effects of residual heavy metals in aquatic environment on sturgeon.     

Lead,zinc, cadmium hyperaccumulation and growth stimulation in Arabis paniculata Franch

Metal hyperaccumulation is of great interest in recent years because of its potential application for phytoremediation of heavy metal contaminated soils. In this study, a field survey and a hydroponic experiment were conducted to study the accumulation characteristics of lead (Pb), zinc (Zn) and cadmium (Cd) in Arabis paniculata Franch., which was found in Yunnan Province, China. The field survey showed that the wild population of A. paniculata was hyper-tolerant to extremely high concentrations of Pb, Zn and Cd, and could accumulate in shoots an average level of 2300 mg kg^?1 dry weight (DW) Pb, 20,800 mg kg^?1 Zn and 434 mg kg^?1 Cd, with their translocation factors (TFs) all above one. Under the hydroponic culture, stimulatory effects of Pb, Zn and Cd on shoot dry biomass were noted from 24 to 193 μM Pb, 9 to 178 μM Cd and all Zn supply levels in nutrient solution, while the effects were not obvious in the roots. Chlorophyll concentrations in Pb, Zn and Cd treatments showed an inverted U-shaped pattern, consistent with the change of plant biomass. Pb, Zn and Cd concentrations in the shoots and roots increased sharply with increasing Pb, Zn and Cd supply levels. They reached > 1000 mg kg^?1 Pb, 10,000 mg kg^?1 Zn and 100 mg kg^?1 Cd DW in the 24 μM Pb, 1223 μM Zn and 9 μM Cd treatment, respectively, in which the plants grew healthy and did not show any symptoms of phytotoxicity. The TFs of Zn were basically higher than one and the amount of Zn taken by shoots ranged from 78.7 to 90.4% of the total Zn. However, the TFs of Pb and Cd were well below one, and 55.0–67.5% of total Pb and 57.8–83.5% of total Cd was accumulated in the shoots. These results indicate that A. paniculata has a strong ability to tolerate and hyperaccumulate Pb, Zn and Cd. Meanwhile, suitable levels of Pb, Zn and Cd could stimulate the biomass production and chlorophyll concentrations of A. paniculata. Thus, it provides a new plant material for understanding the mechanisms of stimulatory effect and co-hyperaccumulation of multiple heavy metals.     

Changes in proline accumulation and antioxidative enzyme activities in Groenlandia densa under cadmium stress

In this study an experiment was carried out to study the process of stress adaptation in Groenlandia densa (opposite-leaved pondweed) grown under cadmium stress (0–20 mg L^?1 Cd). The results showed that Cd concentrations in plants increased with increasing Cd supply levels and reached a maximum of 0.43 mg kg^?1 DW at 0.5 mg L^?1 Cd concentrations. The level of photosynthetic pigments and soluble proteins decreased only upon exposure to high Cd concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Cd concentration. These results suggested an alleviation of stress that was presumably the result of by antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST) as well as ascorbate peroxidase (APX), which increased linearly with increasing Cd levels. Cellular antioxidants levels showed a decline suggesting a defensive mechanism to protect against oxidative stress caused by Cd. In addition, the proline content in G. densa increased with increasing cadmium levels. These findings suggest that G. densa is equipped with an efficient antioxidant mechanism against Cd-induced oxidative stress which protects the plant's photosynthetic machinery from damage.Our present work concluded that G. densa has a high level of Cd tolerance and accumulation. We also found that moderate Cd treatment (0.05–5 mg L^?1 Cd) alleviated oxidative stress in plants, while the addition of higher amounts of Cd (10–20 mg L^?1) could cause an increasing generation of ROS, which was effectively scavenged by the antioxidative system.     

Response of native grasses and Cicer arietinum to soil polluted with mining wastes: Implications for the management of land adjacent to mine sites

Mine tailings are an environmental problem in Southern Spain because wind and water erosion of bare surfaces results in the dispersal of toxic metals over nearby urban or agricultural areas. Revegetation with tolerant native species may reduce this risk. We grew two grasses, Lygeum spartum and Piptatherum miliaceum, and the crop species Cicer arietinum (chickpea) under controlled conditions in pots containing a mine tailings mixed into non-polluted soil to give treatments of 0%, 25%, 50%, 75% and 100% mine tailings. We tested a neutral (pH 7.4) mine tailings which contained high concentrations of Cd, Cu, Pb and Zn. Water-extractable metal concentrations increased in proportion to the amount of tailings added. The biomass of the two grasses decreased in proportion to the rate of neutral mine-tailing addition, while the biomass of C. arietinum only decreased in relation to the control treatment. Neutron radiography revealed that root development of C. arietinum was perturbed in soil amended with the neutral tailings compared to those of the control treatment, despite a lack of toxicity symptoms in the shoots. In all treatments and for all metals, the plants accumulated higher concentrations in the roots than in shoots. The highest concentrations occurred in the roots of P. miliaceum (2500 mg kg^?1 Pb, 146 mg kg^?1 Cd, 185 mg kg^?1 Cu, 2700 mg kg^?1 Zn). C. arietinum seeds had normal concentrations of Zn (70–90 mg kg^?1) and Cu (6–9 mg kg^?1). However, the Cd concentration in this species was ～1 mg kg^?1 in the seeds and 14.5 mg kg^?1 in shoots. Consumption of these plant species by cattle and wild fauna may present a risk of toxic metals entering the food chain.     

Subcellular distribution and chemical forms of cadmium in Bechmeria nivea (L.) Gaud.

Bechmeria nivea (L.) Gaud. (Ramie) is a promising species for Cd phytoextraction with large biomass and fast growth rate. Nevertheless, little information is available on its tolerance mechanisms towards Cd. Determination of Cd distribution and chemical speciation in ramie is essential for understanding the mechanisms involved in Cd accumulation, transportation and detoxification. In the present study, ramie plants were grown in hydroponics with increasing Cd concentrations (0, 1, 3, 7 mg l^?1). The subcellular distribution and chemical forms of Cd in different tissues were determined after 20 days exposure to this metal. To assess the effect of Cd uptake on plant performance, nitrate reductase activity in leaves and root activity were analyzed during the entire experimental period. Increased Cd level in the medium caused a proportional increase in Cd uptake, and the highest Cd concentration occurred in roots, followed by stems and leaves. Subcellular fractionation of Cd-containing tissues indicated that about 48.2–61.9% of the element was localized in cell walls and 30.2–38.1% in soluble fraction, and the lowest in cellular organelles. Cd taken up by ramie rapidly equilibrated among different chemical forms. Results showed that the greatest amount of Cd was found in the extraction of 1 M NaCl and 2% HAC, and the least in residues in all test tissues. In roots, the subdominant amount of Cd was extracted by d-H₂O and 80% ethanol, followed by 0.6 M HCl. While in stems and leaves, the amount of 0.6 M HCl-extractable Cd was comparable with that extracted by 80% ethanol or d-H₂O. 1 mg l^?1 Cd stimulated nitrate reductase activity in leaves and root activity, while a concentration-dependent inhibitory effect was observed with increasing Cd concentration, particularly at 7 mg l^?1 Cd. It could be suggested that the protective mechanisms evolved by ramie play an important role in Cd detoxification at relatively low Cd concentrations (below 3 mg l^?1 Cd) but become restricted to maintain internal homeostasis with higher Cd stress.     

Accumulation of zinc and cadmium and localization of zinc in Picris divaricata Vant.

Picris divaricata Vant., a plant species native to subtropical China, was recently identified as the first Cd/Zn hyperaccumulator from Asteraceae. P. divaricata was grown from wild collected seed for 4 months in a series of pH adjusted test soils with added Zn levels 0–7000 mg kg⁻¹ and Cd levels 0–150 mg kg⁻¹. Plants did not hyperaccumulate Zn (threshold >3000 μg g⁻¹) and weakly hyperaccumulated Cd with little or no dose–response.P. divaricata has multicellular simple trichomes concentrated on the leaf margins and midrib. X-ray analysis showed that Zn was concentrated in larger trichomes and epidermal cells adjacent to the trichome but virtually absent in other leaf tissues. Within the trichomes, Zn was localized in ovate spots around the tips of individual cells. These tips and other locations in the trichome cell contained black electron dense material when examined with transmission electron microscopy, some of which was identified as SiO₂. Silicon and Mn were concentrated in the same areas as Zn. Si has been previously associated with alleviating Zn, Mn and Cd toxicity. Our results support this observation and further investigation is warranted.Calcium and P were concentrated in the distal tips of trichomes, similar to patterns previously observed for calcicole plants grown in elevated Ca soils. Overall, nonsecretory trichomes from many plant families may have a common origin as tissues adapted to handle a variety of environmental metals.     

Continuous production of selenomethionine-enriched Chlorella sorokiniana biomass in a photobioreactor

This article describes the enrichment of the fresh-water green microalga Chlorella sorokiniana in selenomethionine (SeMet). The microalga was cultivated in a 2.2 L glass-vessel photobioreactor, in a culture medium supplemented with selenate (SeO₄^2?) concentrations ranging from 5 to 50 mg L^?1. Although selenate exposure lowered culture viability, C. sorokiniana grew well at all tested selenate concentrations, however cultures supplemented with 50 mg L^?1 selenate did not remain stable at steady state. A suitable selenate concentration in fresh culture medium for continuous operation was determined, which allowed stable long-term cultivation at steady state and maximal SeMet productivity. In order to do that, the effect of dilution rate on biomass productivity, viability and SeMet content of C. sorokiniana at several selenate concentrations were determined in the photobioreactor. A maximal SeMet productivity of 21 μg L^?1 day^?1 was obtained with 40 mg L^?1 selenate in the culture medium. Then a continuous cultivation process at several dilution rates was performed at 40 mg L^?1 selenate obtaining a maximum of 246 μg L^?1 day^?1 SeMet at a low dilution rate of 0.49 day^?1, calculated on total daily effluent volume. This paper describes for the first time an efficient long-term continuous cultivation of C. sorokiniana for the production of biomass enriched in the high value amino acid SeMet, at laboratory scale.     

Effects of nutrients on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

This research investigated the effects of various nutrients on arsenic (As) removal by arsenic hyperaccumulator Pteris vittata L. in a Hoagland nutrient solution (HNS). The treatments included different concentrations of Ca and K in 20% strength of HNS, different strengths of HNS (10, 20 and 30%), different strengths of HNS (10 and 20%) with and without CaCO₃, and different concentrations of Ca, K, NO₃, NH₄, and P in 20% strength of HNS. The plants were grown in nutrient solution containing 1 mg As L^?1 for 4 weeks except the Ca/K experiment where the plants were grown in nutrient solution containing 10 or 50 mg As L^?1 for 1 week. Adding up to 4 mM Ca or 3 mM K to 20% strength HNS significantly (P < 0.05) increased plant arsenic accumulation when the solution contained 10 mg As L^?1. Plant arsenic removal was reduced with increasing Ca and K concentrations at 50 mg As L^?1. Lower strength of HNS (10%) resulted in the greatest plant arsenic removal (79%) due to lower competition of P with As for plant uptake. Addition of CaCO₃ to 20% strength of HNS significantly increased arsenic removal by P. vittata. Among the nutrients tested, NO₃ and CaCO₃ were beneficial to plant arsenic removal while NH₄, P and Cl had adverse effects. This experiment demonstrated that it is possible to optimize plant arsenic removal by adjusting nutrients in the growth medium.     

Responses of non-protein thiols to Cd exposure in Cd hyperaccumulator Arabis paniculata Franch

We investigated the responses of phytochelatins (PCs), glutathione (GSH) and other non-protein thiols in Cd hyperaccumulator Arabis paniculata after Cd exposure. Applying γ-glutamylcysteine synthetase (γ-ECS) inhibitor, l-buthionine-sulfoximine (BSO), the roles of PCs in Cd tolerance and Cd accumulation in A. paniculata were evaluated. Plants were exposed to four Cd concentrations (0, 50, 100 and 250 μM) for different times (2w or 3w) with and without BSO. Overall, Cd exposure had little impact on plant biomass after 2w or 3w of growth except at the highest Cd level. A. paniculata tolerated ≤100 μM Cd with up to 1127 mg kg^?1 Cd in the shoots and 5624 mg kg^?1 Cd in the roots after 3w of Cd exposure. Cd exposure induced formation of PCs and three unknown thiols in the roots, but none were detected in the shoots. BSO had no significant effect on Cd sensitivity in plants though it reduced Cd accumulation in the roots. In addition, the molar ratio of PCs:Cd, which ranged from 0.7 to 1.3 after exposing to 50–100 μM Cd without BSO in the roots, was close to the value expected for PC-mediated Cd sequestration in plants. Those data indicate that GSH and PCs did not contribute to Cd tolerance in the shoots and Cd transport from the root to shoot in A. paniculata, but they may play an important role in Cd accumulation and Cd complexation in the roots of A. paniculata.     

Potential of Typha angustifolia for phytoremediation of heavy metals from aqueous solution of phenol and melanoidin

Typha angustifolia was evaluated for various heavy metals (Cu, Pb, Ni, Fe, Mn, and Zn) bioremediation potential from aqueous solution containing variable concentrations of phenol (100–800 mg l^?1) and melanoidin (2500–8500 Co–Pt) at 20, 40, and 60 days. The concentration of phenol (200–400 mg l^?1) along with melanoidin 2500 Co–Pt showed optimum for phytoremediation of tested heavy metals, while, higher concentrations of melanoidin (5600–8500 Co–Pt) showed toxic effect on T. angustifolia along with phenol. Phenol and melanoidin showed adverse effect on T. angustifolia of up to 20 days incubation, but this leads to induction of peroxidase and ascorbic acid activity to cope with adverse conditions. Subsequently, as pollutants were decreased along with plant growth, peroxidase and ascorbic acid also declined. However, with reduction of peroxidase, catalase level was increased. The Cu, Zn, and Ni were accumulated at maximum in all tested conditions. The TEM observations of T. angustifolia showed clotted deposition of metals and shrinkage of cell in root, breakdown of spongy and palisade parenchyma of leaves at higher concentration of phenol (100 mg l^?1) and melanoidin (5500 Co–Pt). Thus, this study concluded that T. angustifolia could be a potential phytoremediator for heavy metals from metal, melanoidin, and phenol containing industrial wastewater at optimized condition.     

Copper and zinc in Elodea canadensis from rivers with various pollution levels

The anthropogenic impact of xenobiotics contributes to environmental risk for the aquatic environment and thus, must be controlled. Elodea canadensis, a cosmopolitan aquatic macrophyte with an important role in the ecology of many littoral zones, may provide an integrated record of pollution. Therefore, it was interesting to investigate the accumulation of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in this species and in water and bottom sediments collected from rivers with various levels of contamination. Of these rivers one control and one polluted was selected for the collection of E. canadensis for an experiment to compare the ability of this species to accumulate Cu and Zn. These elements were supplemented at concentrations (mg L⁻¹) of 0.01, 0.02, 0.03, 0.05, 0.08 and 0.14 as CuSO₄·5H₂O, and 0.4, 0.6, 0.9, 1.4, 2.03 and 3.04 as ZnSO₄·7H₂O and in a mixture containing (mg L⁻¹) 0.01Cu + 0.4Zn, 0.02Cu + 0.6Zn, 0.03Cu + 0.9Zn, 0.05Cu + 1.4Zn, 0.08Cu + 2.03Zn and 0.14Cu + 3.04Zn. After the experiment, E. canadensis from the polluted river contained significantly higher Cu and Zn concentrations when applied separately and also significantly higher Cu and Zn concentrations when applied as a mixture compared to the control river. These higher concentrations in E. canadensis from the polluted river were found in all combinations in the experiment. Thus, E. canadensis habituated in polluted sites to the exposure, and long-term influence of elevated metal levels appeared to be better adapted, and it also exhibited a higher increase in biomass than plants from the control river in all the experimental Cu and Zn solutions. Younger leaves of E. canadensis were more resistant to the effects of Cu and Zn than older leaves. Both Cu and Zn negatively affected the cell structure of older leaves, although the influence of Cu on plasma membrane integrity and chloroplast distribution was stronger than that of Zn. The influence of the Cu + Zn mixture on E. canadensis resulted in less pronounced cell disintegration than the influence of Cu added separately.The explanation of differences in the E. canadensis biomass increase and metal concentrations under the binary Cu and Zn impact needs further examination.     

Co-planting can phytoextract similar amounts of cadmium and zinc to mono-cropping from contaminated soils

Co-planting crops normally decreases the main crop yield due to the reduced soil surface area occupied by the main crop. However, in our previous experiments, co-planting Sedum alfredii, a shade-requiring, Cd and Zn-hyperaccumulating plant, with corn increased the biomass and metal phytoextraction of S. alfredii. This experiment was conducted to verify if co-planting another hyperaccumulator, Thlaspi caerulescens, with ryegrass (Lolium perenne) in a pot-trial could obtain a similar result. The soil was separated by two permeable nets with a 2 mm interface soil layer to obtain a shared rhizosphere zone. Soluble metal concentrations in the soil in different rooting zones were measured using 0.01 mol L^?1 CaCl₂ extraction. The results showed that the growth of T. caerulescens was significantly promoted by co-planting, with a growth increase of about 2-fold compared with monoculture growth. The total uptake of Cd and Zn by T. caerulescens was not decreased by co-planting, and resulted in similar phytoextraction rates for Cd (about 26.6% of the soil total Cd) and Zn (about 2.4% of the soil total Zn) when compared with monoculture, though the T. caerulescens population was decreased by 50% because of co-planting. Analysis of soil samples showed that T. caerulescens substantially reduced the concentrations of 0.01 mol L^?1 CaCl₂ extractable Cd and Zn throughout the soil, even in the interface area and the ryegrass rooting area. The ryegrass roots did not mobilize more metals for the co-planted T. caerulescens. Based on these results, existing grass on contaminated land could be partly left while planting metal hyperaccumulators for phytoremediation in order to reduce runoff from the contaminated soil. However a field scale trial would be required for these results to be verified.     

Physiological mechanism of hypertolerance of cadmium in Kentucky bluegrass and tall fescue: Chemical forms and tissue distribution

Kentucky bluegrass (Poa pratensis) and tall fescue (Festuca arundinacea) are hypertolerant grasses to soil cadmium contamination. Little information is available on their tolerance mechanism. A sand culture and a hydroponic culture experiment were designed to investigate the Cd chemical form changes and its translocation in different tissues. The results showed that Kentucky bluegrass and tall fescue can tolerate 50–200 mg kg⁻¹ of soil Cd stresses and accumulate as high as 4275 and 2559 mg Cd kg⁻¹ DW, respectively, in their shoots without the loss of shoot biomass. Their Cd hypertolerance was correlated with an increase of the undissolved Cd phosphates in the leaves in both grass species, as determined by sequential solvent extraction procedures. The superior Cd tolerance of tall fescue to Kentucky bluegrass was associated with less Cd translocation into the stele of roots and less Cd transported to leaves. The pectate- and protein-integrated Cd forms may be involved in the symplastic translocation of Cd from cortex into stele, and this may lead the higher Cd concentrations in the stele of roots and then above ground leaves via long-distance transport in Kentucky bluegrass.     

Tolerance of hairy roots of carrots to U chronic exposure in a standardized in vitro device

In soil, high variability of U bioavailability results in large range of apparent U toxic levels for plants. U toxicity on hairy roots of carrot was studied in nutrient gel with a standardized in vitro device. After exposure to 2.5 and 20 mg U L^?1 for 34 days, U concentration ranged between 4 and 563 mg U kg^?1 fresh weight which was in good accordance with U accumulation by roots of plant from contaminated soils. Threshold of U toxicity for root length decreased with time and a transient hormesis occurred for exposure to 2.5 and 5 mg U L^?1. After 34 days and with root length as endpoint, significant toxicity appeared at a gel contamination level above 7.5 mg U L^?1 corresponding to a maximum U concentration in the liquid phase of 0.8 mg L^?1. The calculated EC50 for root length as a function of gel contamination was 9.4 mg U L^?1. Lower threshold and EC50 were observed for biomass as endpoint (resp. 5 and 7.3 mg U L^?1). The low values observed in this study could result from high sensitivity of carrot to U, high bioavailability of U in gel or absence of interferences with microorganisms. This in vitro device appeared adapted to study toxicity of U to plant roots in optimal conditions of both exposure and observations and is recommended to examine further physiological processes and the influence of microorganism interactions.     

Purification and characterization of a new laccase from Shiraia sp.SUPER-H168

A new laccase from Shiraia sp.SUPER-H168 was purified by ion exchange column chromatography and gel permeation chromatography and the apparent molecular mass of this enzyme was 70.78 kDa, as determined by MALDI/TOF-MS. The optimum pH value of the purified laccase was 4, 6, 5.5 and 3 with 2,6-dimethoxyphenol (DMP), syringaldazine, guaiacol and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) as substrates, respectively. The optimum temperature of the purified laccase was 50 °C using DMP, syringaldazine and guaiacol as substrates, but 60 °C for ABTS. Inhibitors and metal ions of SDS, NaN₃, Ag⁺ and Fe³⁺ showed inhibition on enzyme activity of 10.22%, 7.86%, 8.13% and 67.50%, respectively. Fe²⁺ completely inhibited the purified laccase. The K_cat/K_m values of the purified laccase toward DMP, ABTS guaiacol and syringaldazine were 3.99 × 10⁶, 3.74 × 10⁷, 8.01 × 10⁴ and 2.35 × 10⁷ mol^?1 L S^?1, respectively. The N-terminal amino acid sequence of the purified laccase showed 36.4% similarity to Pleurotus ostrestus. Approximately 66% of the Acid Blue 129 (100 mg L^?1) was decolorized by 2.5 U of the purified laccase after a 120 min incubation at 50 °C. Acid Red 1 (20 mg L^?1) and Reactive Black 5 (50 mg L^?1) were decolorized by the purified laccase after the addition of Acid Blue 129 (100 mg L^?1).     

Recycling of agro-industrial sludge through vermitechnology

This work illustrates the feasibility of vermitechnology to stabilize sludge from an agro-industry. To achieve the goal, industrial sludge (IS) was mixed with three different bulky agents, i.e. cow dung (CD), biogas plant slurry (BGS) and wheat straw (WS), in different ratios to produce nine different feed mixtures for earthworm Eisenia fetida. Vermicomposting bedding material was analyzed for its different physic-chemical parameters after 15 weeks of experimentations. In all waste mixtures, a decrease in pH, organic C and C:N ratio, but increase in total N, available P, exchangeable K, exchangeable Ca and trace elements (Mg, Fe and Zn) was recorded. IS (40%) + CD (60%) and IS (40%) + BGS (60%) vermibeds showed the highest mineralization rate and earthworm growth patterns during vermicomposting process. Vermicompost contains (dry weight basis) a considerable range of plant available forms of P (17.5–28.9 g kg^?1), K (13.8–21.4 g kg^?1), Ca (41.1–63.4 g kg^?1), Mg (262.4–348.3 mg kg^?1), Fe (559.8–513.0 mg kg^?1) and Zn (363.1–253.6 mg kg^?1). Earthworm growth parameters, i.e. biomass gain, total cocoon production, individual growth rate (mg wt. worm^?1 day^?1), natality rate, total fecundity were optimum in bedding containing 20–40% industrial sludge. C:N ratio of worm-processed material was within the agronomic acceptable or favorable limit (<15–20). The results clearly suggested that vermitechnology can be a potential technology to convert industrial sludges into vermifertilizer for sustainable land restoration practices.     

Operation of an Anammox SBR in the presence of two broad-spectrum antibiotics

The feasibility of the anaerobic ammonium oxidation (Anammox) process to treat wastewaters containing antibiotics was studied in this work. Concentrations ranging from 100 to 1000 mg L^?1 for tetracycline hydrochloride and from 250 to 1000 mg L^?1 for chloramphenicol were tested in batch assays. A strong inhibitory effect was observed for both antibiotics.A concentration of 20 mg L^?1 of chloramphenicol was continuously added to an Anammox Sequential Batch Reactor (SBR) system, causing a decrease of the nitrogen removal efficiency of 25%. The Specific Anammox Activity (SAA) of the biomass also decreased from 0.25 to 0.05 g N (g VSS d)^?1. Similar effects were observed when 50 mg L^?1 of tetracycline hydrochloride were continuously fed. Both antibiotics did not cause any changes in the physical properties of the biomass. A previous degradation step could be necessary in order to treat wastewaters containing inhibitory concentrations of antibiotics by the Anammox process.     

CBOD5 treatment using the marshland upwelling system

Five-day carbonaceous biochemical oxygen demand (CBOD₅) removal efficiency was evaluated for the marshland upwelling system (MUS) under both intermediate and saltwater conditions. The MUS treated decentralized wastewater from two private camps and a public restroom in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi, and one private camp in the Barataria Terrebonne National Estuary, along Bayou Segnette, Louisiana. Raw wastewater was injected into the surrounding subsurface at a depth of 3.8 or 4.3 m. Various injection flow rates and frequencies were tested in addition to a synthetic wastewater trial. All trials followed a first-order background corrected removal equation, resulting in removal constants ranging from 0.49 to 3.32 m^?1 and predicted surface concentrations from 5.7 to 33.0 mg L^?1. CBOD₅ (unfiltered) influent concentrations of 282 ± 173 mg L^?1 were reduced to an overall effluent mean of 13 ± 13 mg L^?1 by a vector distance of 7 m at Moss Point and from 365 ± 151 mg L^?1 to 3.6 ± 7.6 mg L^?1 by a vector distance of 6 m for Bayou Segnette. Of seven trials, only one failed to achieve effluent CBOD₅ levels below a National Pollutant Discharge Elimination System (NPDES) standard level of 25 mg L^?1.     

Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60 Mg ha⁻¹ of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe–Mn oxides fractions) decreased with the addition of 60 Mg ha⁻¹ of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35 mg kg⁻¹ of Cu, from 211 to 98 mg kg⁻¹ of Zn and from 1.4 to 0.6 mg kg⁻¹ of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138 mg pot⁻¹ of Cu, from 299 to 445 mg pot⁻¹ of Zn and from 1.8 to 3.7 mg pot⁻¹ of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130 mg kg⁻¹, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.     

Physiological responses of Phragmites australis to wastewater with different chemical oxygen demands

Constructed wetlands have been widely used to treat various wastewaters with large differences in their concentration of pollutants. The capability of wetland plants to resist these wastewaters is crucial for a wetland's healthy development. Phragmites australis has been shown to have the capability to grow in simulated wastewater containing a wide concentration of pollutants. In this study, the physiological responses of P. australis to simulated wastewaters with high chemical oxygen demands (CODs) were investigated in a bucket experiment. P. australis was incubated in buckets for 30 days at five treatments of 0, 100, 200, 400, and 800 mg L^?1 COD simulated wastewater. The net photosynthesis rate of the plants declined markedly with increasing COD levels. Proline and malondialdehyde (MDA) contents also increased dramatically. The plants further showed a unimodal pattern of superoxide dismutase (SOD) and peroxidase (POD) distribution along external COD values on the whole, indicating that high COD values (≥200 mg L^?1) can disrupt the normal metabolism of the plant. High COD levels (COD ≥ 400 mg L^?1) caused evident physiological changes in P. australis.