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PubMed1983

Physicochemical speciation of toxic fractions of wastewaters.

A physicochemical speciation scheme in tandem with bioassays identified the toxic fractions of the wastewater from a base metal refining and fertilizer complex. The toxic fractions were the leachates from suspended solids, purgeables, and bound metals of the dissolved fraction. Most of the metals were bound to macrosolutes of Mr greater than 30,000 and exchangeable by cation- and weak anion-exchange resins. In contrast, total chromium and surfactants were bound strongly to microsolutes of Mr less than 1500, removable only by strong anion-exchange resin.

Animals↗
PubMed2005

Rubber additives induce oxidative stress in rainbow trout.

Several studies have demonstrated the toxicity of rubber leachate, mainly from rubber tires, to aquatic organisms. In the present study rainbow trout (Oncorhynchus mykiss) were exposed to water provided to aquaria through a rubber hose. Increased hepatic ethoxyresorufin-O-deethylase (EROD) activity, and glutathione reductase (GR) activity were observed in the exposed fish. Two common rubber additives, 2-mercaptobenzothiazole (MBT) and diphenylamine (DPA) and structurally related compounds, were identified by chemical analyses of water samples as were hydroxylated polycyclic aromatic hydrocarbons. Metabolites of these compounds were also detected in the bile of exposed fish, as were some of the parent compounds. In a following experiment, we injected rainbow trout with DPA or MBT. Both compounds affected total glutathione (tGSH) concentration in liver and MBT caused an increase in hepatic GR and glutathione S-transferase (GST) activity as well. In DPA injected fish, hydroxylated DPA was the main metabolite in the bile. Our results indicate that rubber chemicals may leach into the water surroundings where they can be taken up and metabolised by fish. Some of these chemicals can lead to up-regulation of antioxidant defences as demonstrated with DPA and MBT injections.

Analysis of Variance↗
PubMed2004

Technical review of the Laboratory Biosphere closed ecological system facility.

Laboratory Biosphere is a 40 m3 closed life system that commenced operation in May 2002. Light is from 12,000 W of high pressure sodium lamps over planting beds with 5.37 m2 of soil. Water is 100% recycled by collecting condensate from the temperature and humidity control system and mixing with leachate collected from under the planting beds. Atmospheric leakage was estimated during the first closure experiment to be 0.5-1% per day in general plus about 1% for each usage of the airlock door. The first trial run of 94 days was with a soybean crop grown from seeds (May 17, 2002) to harvest (August 14, 2002) plus 5 days of post-harvest closure. The focus of this initial trial was system testing to confirm functionality and identify any necessary modifications or improvements. This paper describes the organizational and physical features of the Laboratory Biosphere.

Air Conditioning↗
PubMed2005

Protein interactions with subcutaneously implanted biosensors.

Biofouling of in vivo glucose sensors has been indicated as the primary reason for sensitivity losses observed during the first 24 h after implant [Wisniewski N, Moussy F, Reichert WM. Characterization of implantable biosensor membrane biofouling. Fresen J Anal Chem 2000; 366(6-7): 611-621]. Identification of the biomolecules that contribute to these sensitivity perturbations is the primary objective of the research presented. Active needle-type glucose sensors were implanted in Sprague-Dawley rats for 24h, and then a proteomics approach was used to identify the substances absorbed to the sensors. MALDI-TOF mass spectrometry was the primary tool utilized to identify the biomolecules in sensor leachate samples and species absorbed directly on sensor membranes excised from explanted in vivo sensors. Not surprisingly serum albumin was identified as the primary biomolecule present, however, predominantly as endogenous fragments of the protein. In addition, several other biomolecule fragments, mainly less than 15 kD, were identified. Based on these findings, it is concluded that fragments of larger biomolecules infiltrate the sensor membranes causing diminished glucose diffusivity, thus decreasing in vivo sensitivity.

Adsorption↗
PubMed2004

The interacting effects of temperature and plant community type on nutrient removal in wetland microcosms.

Treatment wetlands can remove nutrients from inflow sources through biogeochemical processes. Plant composition and temperature play important roles in the nutrient removal efficiency of these wetlands, but the interactions between these variables are not well understood. We investigated the seasonal efficiency of wetland macrophytes to reduce soil leachate concentrations of total nitrogen and total phosphorus in experimental microcosms. Each microcosm contained one of six vegetation treatments: unplanted, planted with one of four species (Carex lacustris, Scirpus validus, Phalaris arundinacea and Typha latifolid) in monoculture or planted with an equal abundance of all four species. Microcosms were also subjected to two temperature treatments: insulated microcosms and microcosms exposed to environmental conditions. A constant nutrient solution containing 56 mg/l N and 31 mg/l P was added to all microcosms three times a week. Water samples were analyzed monthly for total dissolved nitrogen and total dissolved phosphorous. Microcosms exhibited a typical pattern of seasonal nutrient removal with higher removal rates in the growing season and lower rates in the winter months. In general, planted microcosms outperformed unplanted microcosms. Among the plant treatments, Carex lacustris was the least efficient. The four remaining plant treatments removed an equivalent amount of nutrients. Insulated microcosms were more efficient in the winter and early spring months. Although a seasonal pattern of nutrient removal was observed, this variation can be minimized through planting and insulation of wetlands.

Ecosystem↗
PubMed2005

Amount of leachant and water absorption levels of wood treated with borates and water repellents.

Wood protection efficacy of borates against biological agents, flame retardancy, and suitability to the environment is well known. Since borates can be applied to timber as water based solutions, they are preferred economically as well. Even though they are highly mobile in wood, boron compounds are widely used in timber preservation. Borates migrate in liquid and increase the hygroscopicity of wood in damp conditions. This study deals with the physical restriction of water access in wood by impregnating water repellent agents into wood to limit amount of leachant and water absorption levels of wood after boron treatment. Borates were incorporated with polyethylene glycol-400 (PEG-400) their bulking effect in wood was considered. Results indicated that the amount of leachates from wood treated with borates in PEG-400 was remarkably higher compared to those of wood treated with the aqueous solutions of borates. Water absorption (WA) levels of wood treated with aqueous solutions of borates were higher than those of their treated samples with the solutions in PEG-400. Secondary treatments of wood with the water repellent (WR) chemicals following borate impregnation reduced the leaching of chemicals from wood in water and also WA of the specimens were less than those of the wood treated with only borates from aqueous and PEG solutions. Styrene (St) was the most effective monomer among the other agents used in terms of immobility effect on borates and WA.

Borates↗
PubMed2006

BOD5 and COD removal and sludge production in SBR working with or without anoxic phase.

The aim of this study was to estimate the BOD(5) and COD removal efficiency and biomass yield coefficient in sequencing batch reactors (SBR) treating landfill leachate. Experiments were carried out in four SBRs at HRT of 12, 6, 3 and 2d. Two series were performed. In series 1, the reactors were operated in a 24h cycle mode (anoxic 3h, aeration 18 h, settling 2.75 h, and discharge 0.25 h). In series 2, however, the anoxic phase was eliminated. In both series the BOD(5) removal efficiency was almost identical--over 98%. On shortening HRT from 12 to 2d, COD removal efficiency decreased from 83.1% to 76.7% (series 1). In series 2, efficiency ranged from 79.6% to 75.7%. In the reactors working with the anoxic phase the observed biomass yield coefficient (Y(obs)) was nearly constant (0.55-0.6 mg VSS/mg COD). Upon elimination of the anoxic phase, the Y(obs) was observed to decrease from 0.32 mg VSS/mg COD (HRT 2d) to 0.04 mg VSS/mg COD (HRT 12d).

Animals↗
PubMed2006

Long term fate of slurry derived nitrogen in soil: a case study with a macro-lysimeter experiment having received high loads of pig slurry (Solepur).

In intensive livestock production areas, land application remains the traditional management of manure and slurries for nutrient recycling. For sustainable agriculture there is fear, however, that this practice may have detrimental effects, particularly on the depletion of Soil Organic Matter associated with pig slurry applications. We investigated the long-term fate of nitrogen in a reconstituted soil having received high doses of pig slurry during 5 years (1991-1995). After 5 years of intensive application rates (nearly 1000 m(3)yr(-1)), the N and C content of the soil profile (0-20 cm) had increased by about 60% and 50%, respectively. These results confirm previous findings although it seems that the particularly high rates of application may explain, in part, the relatively important N incorporation in soil. Pig slurry applications ceased in 1995 and nitrogen content in soil and drainage water have been monitored. Apparent mineralization rates were calculated from the decrease in N content of the soil. This analysis indicated that more than 50% of the added N stored in the soil at the end of the applications would eventually be mineralized, leaving nearly 50% of the stored N to be immobilized in the soil. These results are the first published of their kinds, as most reports never examine the fate of applied pig slurry N after halting applications. In addition the few reports on long-term experiments suggest that Soil Organic Matter following pig slurry applications may be unstable. Our analysis tends to show the contrary. However, this conclusion must be tempered because data on nitrate leachate patterns suggest that soil management such as ploughing and sowing may actually trigger mineralization that could eventually deplete nitrogen stored following applications.

Animals↗
PubMed2006

Microbially-influenced degradation of solidified/stabilized metal waste.

In the present study, a refined microbially-influenced degradation method was used to evaluate the stability of a solidified synthetic waste containing chromium salt, cement and fly ash in two different proportions. The experimental samples showed evidence of microbial growth by leaching of sulfate. Chromium leached by Thiobacillus thiooxidans from the experimental samples 'C1' (10.26% CrCl3 .6H2O; 89.74% cement) and 'FC1' (10.26% CrCl3 .6H2O; 10% fly ash; 79.74% cement), after 30 days of exposure was 14.53 mg/g and 9.53 mg/g, respectively. The corresponding concentration of chromium in the leachate was 0.189 mg/l and 0.124 mg/l, respectively, which was lower than the toxicity characteristic leaching procedure (TCLP), regulatory limit (5 mg/l). Replacement of cement by 10% fly ash in FC1 restricted the leaching of chromium more effectively. Model equations based on two shrinking core models namely, acid dissolution and bulk diffusion model, were used to analyze the kinetics of microbial degradation. Of the two approaches, the bulk diffusion model fit the data better than the acid dissolution model as indicated by the correlation coefficients of >0.97.

Acidithiobacillus thiooxidans↗
PubMed2004

Development of urease and glutamic dehydrogenase amperometric assay for heavy metals screening in polluted samples.

An amperometric assay based on urease inactivation has been developed for the screening of heavy metals in environmental samples. The enzyme urease catalyses the hydrolysis of urea and the formation of NH(4)(+) is determined using a NADH-glutamate dehydrogenase coupled reaction system. NADH consumption is monitored amperometrically using screen-printed three electrode configuration and its oxidation current is then correlated to urease activity. The presence of heavy metals in the samples inhibits the urease activity, resulting in a lower NH(4)(+) production and therefore a decrease in NADH oxidation. The use of metallised carbon electrodes gave a decrease in NADH oxidation potential from +300 mV versus Ag/AgCl compared with > +600 mV for bare carbon electrodes, and thus minimised interferences from oxidizable species present in the samples. Electrodes fouling and possible contamination after reuse and cleaning was also eliminated by using screen-printed disposable electrodes. The linear range obtained for Hg(II) and Cu(II) was 10-100 microgl(-1) with a detection limit of 7.2 microgl(-1) and 8.5 microgl(-1), respectively. Cd(II) and Zn(II) produced enzyme inhibition in the range 1-30 mgl(-1), with limits of detection of 0.3 mgl(-1) for Cd(II) and 0.2 mgl(-1) for Zn(II). Pb(II) did not inactivate the urease enzyme significantly at the studied range (up to 50 mgl(-1)). Coefficients of variation (CV) values were 6-9% in all cases. Application of the assay system to leachate samples gave reliable and accurate toxicity assessments when compared to atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-MS) analysis. This approach provides to be a simple and rapid (15 min, including enzyme inhibition time) method for metal ions detection.

Biosensing Techniques↗
PubMed2006

Evaluation of essential and toxic metals by ultrasound-assisted acid leaching from scalp hair samples of children with macular degeneration patients.

BACKGROUND: The causes of night blindness in children are multifactorial and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence hair composition. METHOD: An ultrasonic-assisted acid leaching procedure was developed as a sample pretreatment for the determination of Zn, Cu, Cd, As and Pb in human scalp hair samples of night blindness male children with age between 5 to 15 y and compared with the children without vision anomalies that lived in the same localities. The effects of different factors on acid leaching of metals, such as preintensification time (without ultrasonic stirring) after treatment of acid mixture, exposure time to ultrasound and temperature of the ultrasonic bath have been investigated. The proposed method was validated by certified reference samples of scalp hair CRM 397. The wet acid digestion method was used to obtain the total metal concentration in both scalp hair and CRM samples. Cu and Zn in leachates and digests were measured by flame atomic absorption spectrometry (FAAS) using a conventional air/acetylene flame, while Cd and Pb were determined by electrothermal atomic absorption spectrometry (ETAAS) under optimized conditions. RESULTS: It was observed that at optimal conditions, the recovery for Zn, Cd, Pb, As and Cu were 98%, 98.5%, 96%, 97.2% and 94% respectively. The mean values of Zn and Cu in scalp hair samples of children having night blindness were significantly lower as compared to normal healthy children (p for Zn<0.001 and Cu<0.003), while the level of toxic metals As, Cd and Pb were significantly higher in children having ocular problems as related to normal children (p As<0.0074, Cd<0.001 and lead<0.004). CONCLUSION: These data present guidance to clinicians and other professional investigating deficiency of essential trace metals and excessive level of toxic metals in biological samples.

Acids↗
PubMed2004

Mobilization of arsenic from subsurface sediments by effect of bicarbonate ions in groundwater.

Arsenic leaching by bicarbonate ions has been investigated in this study. Subsurface sediment samples from Bangladesh were treated with different carbonate and bicarbonate ions and the results demonstrate that the arsenic leaching efficiency of the carbonate solutions decreased in the order of Na2CO3>NaHCO3>BaCO3>MnCO3. Sodium carbonate and bicarbonate ions extracted arsenic most efficiently; Na2CO3 leached maximum 118.12 microg/l of arsenic, and NaHCO3, 94.56 microg/l of arsenic from the Ganges delta sediments after six days of incubation. The arsenic concentrations extracted in the batch experiments correlated very well with the bicarbonate concentrations. The kinetics study of arsenic release indicates that arsenic-leaching rate increased with reaction time in bicarbonate solutions. Bicarbonate ions can extract arsenic from sediment samples in both oxic and anoxic conditions. A linear relationship found between arsenic contents in core samples and those in leachates suggests that dissolved arsenic concentration in groundwater is related to the amount of arsenic in aquifer sediments. In batch experiment, bicarbonate solutions effectively extracted arsenic from arsenic adsorbed iron oxyhydroxide, reflecting that bicarbonate solutions may mobilize arsenic from iron and manganese oxyhydroxide in sediments that are ubiquitous in subsurface core samples. Carbonate ion may form complexes on the surface sites of iron hydroxide and substitute arsenic from the surface of minerals and sediments resulting in release of arsenic to groundwater. Like in the batch experiment, arsenic and bicarbonate concentrations in groundwater of Bangladesh correlated very well. Therefore, bicarbonate leaching is presumed to be one important mechanism to mobilize arsenic in bicarbonate dominated reducing aquifer of Bangladesh and other parts of the world as well.

Arsenic↗
PubMed2004

Laboratory leaching studies of oryzalin and diuron through three undisturbed vineyard soil columns.

The leaching of diuron and oryzalin through undisturbed soil columns was studied in the laboratory using three vineyard soils from Vosne-Romanée (Burgundy): a rendosol, a calcosol and a vegetated calcosol. After 845 mm of simulated rainfall in 15 days, soil leachates contained higher amounts of diuron (3.2%, 11.8% and 18.8% of applied diuron, respectively) than oryzalin (0.2%, 4.9%, 3.7%, respectively). A greater proportion of soil extractable residues was obtained for diuron (42.5%, 26.8% and 32.2%, respectively) than for oryzalin (14.7%, 12% and 15.5%, respectively). The greater mobility of diuron might be related to its higher water solubility (36.4 mgl(-1) compared with 2.6 mgl(-1) for oryzalin) and smaller adsorption coefficient (400 lkg(-1), compared with 700-1100 lkg(-1) for oryzalin). The mobility of the two herbicides was greater in the two calcosols than in the rendosol, not only due to different organic carbon contents but also different soil textures and structures.

Adsorption↗
PubMed2004

Low-grade MgO used to stabilize heavy metals in highly contaminated soils.

Low-grade MgO may be an economically feasible alternative in the stabilization of heavy metals from heavily contaminated soils. The use of MgO is described acting as a buffering agent within the pH 9-11 range, minimizing heavy metals solubility and avoiding the redissolution that occurs when lime is used. The effectiveness of LG-MgO has been studied as stabilizer agent of heavily polluted soils mainly contaminated by the flue-dust of the pyrite roasting. The use of LG-MgO as a reactive medium ensures that significant rates of metal fixation, greater than 80%, are achieved. The heavy metals leachate from the stabilized soil samples show a concentration lower than the limit set to classify the waste as non-special residue. Regardless of the quantity of stabilizer employed (greater than 10%), LG-MgO provides an alkali reservoir that allows guaranteeing long-term stabilization without varying the pH conditions.

Environmental Pollution↗
PubMed2004

Adsorption-desorption, persistence and leaching behavior of thifluzamide in alluvial soil.

Investigations were undertaken to study the adsorption-desorption, persistence and leaching of thifluzamide (2',6'-dibromo-2-methyl-4'-trifluoromethoxy-4-trifluoro methyl-1,3-thiazole-5-carboxanilide) in an alluvial soil under laboratory conditions. The adsorption-desorption studies were carried out using batch equilibration technique. The results revealed high but weak adsorption of thifluzamide in alluvial soil with K(F) value of 9.62 and 'n' value of 0.63. About 47-62% of the adsorbed amount got desorbed in four desorption cycles, which further substantiate the hypothesis of weak binding. The hysteresis coefficient varied from 0.19 to 0.40. Persistence studies carried out at three concentration levels (0.1, 1.0 and 10.0 microgg(-1)) and under three moisture conditions (air-dry, field capacity moisture and submerged) revealed that thifluzamide is a persistent chemical and only 19.5-54.0% dissipation was recorded on 90th day. However, it appears that aerobic microbes are more efficient in degrading thifluzamide than anaerobic microbes. The preliminary leaching studies carried out in the laboratory revealed that thifluzamide was moderately mobile in alluvial soil. Only small amounts (<1%) were recovered from leachate fractions whereas major portion remained in 0-15 cm soil depth.

Adsorption↗
PubMed2004

Leaching of lead metallurgical slag in citric solutions--implications for disposal and weathering in soil environments.

Metallurgical slags from primary lead smelting were submitted to a 30-day batch leaching procedure in 20 and 8 mM citric solutions in order to determine the kinetics of release of Pb, Cu, Zn and As. The experiment was coupled with the PHREEQC-2 speciation-solubility modelling and mineralogical study of newly formed products (SEM/EDS, XRD, TEM/EDS and Raman spectrometry). A strong scavenging of metals and metalloids from the 8 mM citric leachate was observed due to the formation of newly formed products. The secondary precipitate consisted of well-developed calcite (CaCO3) crystals and amorphous organo-mineral matrix composed of hydrous ferric oxides and amorphous SiO2. Metals (Pb, Zn, Cu) and arsenic released into the solution were subsequently bound onto the newly formed product (adsorption on oxides) or trapped within the calcite structure (Zn, Mn). Similar scavenging mechanism can be taken into account in real soil systems with lower concentration of citric acid. Then, the covering of slag dumps with a thick soil layer and subsequent re-vegetation might be a possible scenario for slag management on some metallurgical sites.

Citric Acid↗
PubMed2005

Iron and organo-bentonite for the reduction and sorption of trichloroethylene.

Hybrid barriers using dechlorination and immobilization were studied to remove trichloroethylene (TCE) in this study. Hybrid barriers of iron filings and organo (hexadecyltrimethylammonium, HDTMA)-bentonite were simulated in columns to assess the performance of the hybrid barriers. TCE reduction rate for the mixture of zero valent iron (ZVI) and HDTMA-bentonite was approximately seven times higher than that for ZVI, suggesting the reduction of TCE was accelerated when HDTMA-bentonite was mixed with ZVI. For the column of two separate layers of iron and HDTMA-bentonite, TCE reduction rate was nearly similar to that for ZVI alone, but the partition coefficient (Kd) was 4.5 times higher than that for ZVI only. TCE was immobilized in the first layer with HDTMA-bentonite due to sorption, and then dechlorinated in the second layer with iron filings due to reduction. The HDTMA-bentonite and minimally-desorbed HDTMA from the organo-bentonite are believed to contribute the increase in TCE concentration on iron surface so that more TCE could be available for reduction. Therefore, the incorporation of HDTMA-bentonite into ZVI not only can effectively retard the transport of chlorinated organic contaminants from landfill leachate or oil shock in subsurface environment, also can expedite the reduction rate of TCE.

Adsorption↗
PubMed2005

Assessment of the mechanical stability and chemical leachability of immobilized electroplating waste.

The effectiveness of cement based treatment technology, in immobilizing chromium laden electroplating sludge was assessed by conducting toxicity characteristic leaching procedure (TCLP). The mechanical stability of the blocks was tested by measuring the compressive strength. Other leaching tests such as NEN 7341 test, ANS 16.1 and multiple TCLP (MTCLP) test conducted on select solidified blocks showed that chromium was immobilized by the binder studied. A linear relationship was obtained between the cumulative fraction of chromium leached (CFL) and square root of time in the solidified samples proving that diffusion is the controlling mechanism for leaching of chromium. The leachability indices (LI) obtained for the solidified materials using cement and cement-fly ash system (EPC6, EPFC6A and EPFC6B) satisfy the guidance value as per US NRC, which clearly indicates that chromium is well retained within the solid matrix. Chromium concentrations in the TCLP leachates of the above mix ratios were well within the regulatory level of United States Environmental Protection Agency (USEPA). Molecular characterization of the solidified material was carried out using Fourier transformation infra red (FTIR) technique.

Chromium↗