Yield and grain quality of spring wheat (Triticum aestivum L., cv. Drabant) exposed to different concentrations of ozone in open-top chambers

Spring wheat (Triticum aestivum L., cv. Drabant) was exposed to different concentrations of ozone in open-top chambers for two growing seasons, 1987 and 1988, at a site located in south-west Sweden. The chambers were placed in a field of commercially grown spring wheat. The treatments were charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus extra ozone (NF(+)). In 1988, one additional ozone concentration (NF(++)) was used. Grain yield was affected by the ozone concentration of the air. Air filtration resulted in an increase in grain yield of about 7% in both years, compared to NF. The addition of ozone (NF(+), NF(++)) reduced grain yield and increased the content of crude protein of the grain in both years. Filtration of the air had no significant effect on the content of crude protein, compared to NF. The results showed a strong positive chamber effect on grain yield in the cold and wet summer of 1987. In 1988, there was no net chamber effect on grain yield. The relative differences between the CF, NF and NF(+) treatments with respect to grain yield were of the same magnitude in the two years, despite the very different weather conditions.     

EDTA and HEDTA effects on Cd, Cr, and Ni uptake by Helianthus annuus

Phytoremediation has shown great potential as an alternative treatment for the remediation of heavy-metal-contaminated soils and groundwater. However, the lack of a clear understanding pertaining to metal uptake/translocation mechanisms, enhancement amendments, and external effects on phytoremediation has hindered its full-scale application. The objective of this research was to investigate the ability of synthetic chelators for enhancing the phytoremediation of cadmium-, chromium- and nickel-contaminated soil. Ethylenediaminetriacetic acid (EDTA) and N-(2-hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) were applied to the soil at various dosages to elevate metal mobility. Uptake into and translocation within Helianthus annuus was determined. It was found that EDTA at a rate of 0.5 g/kg significantly increased the shoot concentrations of Cd and Ni from 34 and 15 to 115 and 117 mg/kg, respectively. The total removal efficiency for EDTA was 59 microg/plant. HEDTA at the same application rate resulted in a total metal uptake of 42 microg/plant. These research demonstrated that chelator enhancement is plant- and metal-specific and is subjective to inhibition when multiple heavy metals are present. Results also showed that chelator toxicity reduced the plant's biomass, thereby decreasing the amount of metal accumulation.     

Application of a constructed wetland for industrial wastewater treatment: a pilot-scale study

The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Four parallel pilot-scale modified free water surface (FWS) constructed wetland systems [dimension for each system: 4-m (L)x1-m (W)x1-m (D)] were installed inside an industrial park for conducting the proposed treatability study. The averaged influent contains approximately 170 mg l(-1) chemical oxygen demand (COD), 80 mg l(-1) biochemical oxygen demand (BOD), 90 mg l(-1) suspend solid (SS), and 32 mg l(-1) NH(3)-N. In the plant-selection study, four different wetland plant species including floating plants [Pistia stratiotes L. (P. stratiotes) and Ipomoea aquatica (I. aquatica)] and emergent plants [Phragmites communis L. (P. communis) and Typha orientalis Presl. (T. orientalis)] were evaluated. Results show that only the emergent plant (P. communis) could survive and reproduce with a continuous feed of 0.4m(3)d(-1) of the raw wastewater. Thus, P. communis was used in the subsequent treatment study. Two different control parameters including hydraulic retention time (HRT) (3, 5, and 7d) and media [vesicles ceramic bioballs and small gravels, 1cm in diameter] were examined in the treatment study. Results indicate that the system with a 5-d HRT (feed rate of 0.4m(3)d(-1)) and vesicles ceramic bioballs as the media had the acceptable and optimal pollutant removal efficiency. If operated under conditions of the above parameters, the pilot-plant wetland system can achieve removal of 61% COD, 89% BOD, 81% SS, 35% TP, and 56% NH(3)-N. The treated wastewater meets the current industrial wastewater discharge standards in Taiwan.     

Heavy metal distribution in sediments and ecological risk assessment: The role of diagenetic processes in reducing metal toxicity in bottom sediments

This paper describes the heavy metal distributions in river and lagoonal sediments of Jacarepaguá Basin, Rio de Janeiro, Brazil. The occurrence of metal phase translocation from the reducible to the oxidizable was observed for Fe, Mn and Ni, from the fluvial environment to the lagoonal. Cu was mainly associated with the oxidizable phase while Zn and Pb were mainly associated with the reducible phase in both environments. It has been demonstrated that metal sulfide formation and complexation by organic complexes are very important aspects in terms of toxicity reduction. By means of a risk assessment methodology, based on available sediment data, it was demonstrated that the lagoonal system is exposed to a low potential ecological risk and that Zn was the metal of greater concern with respect to the system pollution.     

Effect of surfactants at low concentrations on the sorption of atrazine by natural sediment.

A series of experiments were carried out to determine the effect of surfactants at low concentrations on the sorption of atrazine by natural sediments. With surfactant concentrations ranging from 0 to 20 mg/ L, anionic and cationic surfactants appreciably reduce the adsorption of atrazine, while nonionic surfactant decreases the adsorption of atrazine at concentrations equal to or less than 1 mg/L and increases adsorption at higher concentrations. Desorption of atrazine in the presence of different sodium dodecylbenzene sulfonate (SDBS) concentrations shows that a portion of the bound pesticide resists desorption in the SDBS free system. However, the addition of SDBS accelerates the desorption of atrazine. Furthermore, the nature of sediment and the contacting sequence of SDBS, at 10 mg/L, with the sediment, also influence the adsorption of atrazine. The conclusions in this study could be explained partially by the effect of the type and concentration of surfactants and the characteristics of sediments.     

Effects of solution conditions on the precipitation of phosphate for recovery. A thermodynamic evaluation

To understand the effects of solution conditions on the precipitation of calcium phosphates from wastewater for recovery, a computer programme PHREEQC was employed to calculate the speciation and saturation-index (SI) with respect to hydroxyapatite of a chemically defined precipitation system, which contains phosphate of 1–200 mg P/l, with Ca/P molar ratios of one to 10 times of the stoichiometric calcium to phosphorus molar ratio of hydroxyapatite, at a pH range of 7.0–11.0. The results show that the SI is respectively the logarithmic function of the phosphate concentration and the calcium concentration, increasing with the increase of either of them; the SI is a polynomial function of the solution pH value and increases with its increase, and the effect of solution pH value is due to its influence on base uptake of the precipitation reaction and the speciation of phosphate and calcium ions; the SI is also a logarithmic function of the solution ionic strength but decreases with its increase; at the temperature range of 5–30 °C the SI increases linearly with solution temperature and the effect of temperature is also due to its influence on the speciation of phosphate and calcium ions.     

Sorption and mobility of metronidazole, olaquindox, oxytetracycline and tylosin in soil

Laboratory studies were conducted to characterise four different antibiotic compounds with regard to sorption and mobility in various soil types. Distribution coefficients (Kd values) determined by a batch equilibrium method varied between 0.5 and 0.7 for metronidazole, 0.7 and 1.7 for olaquindox and 8 and 128 for tylosin. Tylosin sorption seems to correlate positively with the soil clay content. No other significant interactions between soil characteristics and sorption were observed. Oxytetracycline was particularly strongly sorbed in all soils investigated, with Kd values between 417 in sand soil and 1026 in sandy loam, and no significant desorption was observed. Soil column leaching experiments indicated large differences in the mobility of the four antibiotic substances, corresponding to their respective sorption capabilities. For the weakly adsorbed substances metronidazole and olaquindox the total amounts added were recovered in the leachate of both sandy loam and sand soils. For the strongly adsorbed oxytetracyline and tylosin nothing was detected in the leachate of any of the soil types, indicating a much lower mobility. Results from defractionation and extraction of the columns (30 cm length) showed that 60-80% of the tylosin added had been leached to a depth of 5 cm in the sandy loam soil and 25 cm in the sand soil.     

Biodegradation of phthalate esters by two bacteria strains

In this study two aerobic phthalic acid ester (PAE) degrading bacteria strains, DK4 and O18, were isolated from river sediment and petrochemical sludge, respectively. The two strains were found to rapidly degrade PAE with shorter alkyl-chains such diethyl phthalate (DEP), dipropyl phthalate (DPrP), di-n-butyl phthalate (DBP), benzylbutyl phthalate (BBP) and diphenyl phthalate (DPP) are very easily biodegraded, while PAE with longer alkyl-chains such as dicyclohexyl phthalate (DCP) and dihexyl phthalate (DHP) and di-(2-ethylhexyl) phthalate (DEHP) are poorly degraded. The degradation rates of the eight PAEs were higher for strain DK4 than for strain O18. In the simultaneous presence of strains DK4 and O18, the degradation rates of the eight PAEs examined were enhanced. When the eight PAEs were present simultaneously, degradation rates were also enhanced. We also found that PAE degradation was delayed by the addition of nonylphenol or selected polycyclic aromatic hydrocarbons (PAHs) at a concentration of 1 microg/g in the sediment. The bacteria strains isolated, DK4 and O18, were identified as Sphigomonas sp. and Corynebacterium sp., respectively.     

Accumulation of lead, zinc, copper and cadmium by 12 wetland plant species thriving in metal-contaminated sites in China

The concentrations of lead, zinc, copper and cadmium accumulated by 12 emergent-rooted wetland plant species including different populations of Leersia hexandra, Juncus effusus and Equisetum ramosisti were investigated in field conditions of China. The results showed that metal accumulation by wetland plants differed among species, populations and tissues. Populations grown in substrata with elevated metals contained significantly higher metals in plants. Metals accumulated by wetland plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. That some species/populations could accumulate relatively high metal concentrations (far above the toxic concentration to plants) in their shoots indicates that internal detoxification metal tolerance mechanism(s) are also included. The factors affecting metal accumulation by wetland plants include metal concentrations, pH, and nutrient status in substrata. Mostly concentrations of Pb and Cu in both aboveground and underground tissues of the plants were significantly positively related to their total and/or DTPA-extractable fractions in substrata while negatively to soil N and P, respectively. The potential use of these wetland plants in phytoremediation is also discussed.