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PubMed2006

Cadmium leaching from micro-lysimeters planted with the hyperaccumulator Thlaspi caerulescens: experimental findings and modeling.

The use of heavy metal hyperaccumulating plants has the potential to become a promising new technique to remediate contaminated sites. We investigated the role of metal mobilization in the Cd hyperaccumulation of Thlaspi caerulescens (J. & C. Presl, 'Ganges'). In a micro-lysimeter experiment we investigated the dynamics of Cd concentration of leachate as well as Cd removal by plant uptake in four treatments: (i) Control (bare soil), (ii) T. caerulescens, (iii) nonhyperaccumulator Brassica juncea (L.) Czern. ('PI 426308'), and (iv) co-cropping of the hyperaccumulator and nonhyperaccumulator. The experimental findings were analyzed using one- and two-site rate-limited desorption models. Co-cropping of T. caerulescens and B. juncea did not enhance metal uptake by B. juncea. Although Cd uptake of T. caerulescens was 10 times higher than that of B. juncea, the Cd concentration of leachate of the T. caerulescens treatment did not decrease below that of the B. juncea treatment. The Cd depletion in leachate was well reproduced by the two-site rate-limited desorption model. The optimized desorption coefficient was three orders of magnitude higher in the rhizosphere than in the bulk soil. Our results indicate that T. caerulescens accelerates the resupply of Cd from soil pointing to an important role of kinetic desorption in the hyperaccumulation by T. caerulescens.

Cadmium↗
PubMed2006

Nitrogen- vs. phosphorus-based dairy manure applications to field crops: nitrate and phosphorus leaching and soil phosphorus accumulation.

Management of animal manures to provide nutrients for crop growth has generally been based on crop N needs. However, because manures have a lower N/P ratio than most harvested crops, N-based manure management often oversupplies the crop-soil system with P, which can be lost into the environment and contribute to eutrophication of water bodies. We examined the effects of N- vs. P-based manure applications on N and P uptake by alfalfa (Medicago sativa L.), corn (Zea mays L.) for silage, and orchardgrass (Dactylis glomerata L.), leaching below the root zone, and accumulation of P in soil. Treatments included N- and P-based manure rates, with no nutrient input controls and inorganically fertilized plots for comparison. Nitrate concentrations in leachate from inorganic fertilizer or manure treatments averaged 14 mg NO(3)-N L(-1), and did not differ by nutrient treatment. Average annual total P losses in leachate did not exceed 1 kg ha(-1). In the top 5 cm of soil in plots receiving the N-based manure treatment, soil test P increased by 47%, from 85 to 125 mg kg(-1). Nitrogen- and P-based manure applications did not differ in ability to supply nutrients for crop growth, or in losses of nitrate and total P in leachate. However, the N-based manure led to significantly greater accumulation of soil test P in the surface 5 cm of soil. Surface soil P accumulation has implications for increased risk of off-field P movement.

Animals↗
PubMedDate not supplied

Chemical and physical properties of dry flue gas desulfurization products.

Beneficial and environmentally safe recycling of flue gas desulfurization (FGD) products requires detailed knowledge of their chemical and physical properties. We analyzed 59 dry FGD samples collected from 13 locations representing four major FGD scrubbing technologies. The chemistry of all samples was dominated by Ca, S, Al, Fe, and Si and strong preferential partitioning into the acid insoluble residue (i.e., coal ash residue) was observed for Al, Ba, Be, Cr, Fe, Li, K, Pb, Si, and V. Sulfur, Ca, and Mg occurred primarily in water- or acid-soluble forms associated with the sorbents or scrubber reaction products. Deionized water leachates (American Society for Testing and Materials [ASTM] method) and dilute acetic acid leachates (toxicity characteristic leaching procedure [TCLP] method) had mean pH values of >11.2 and high mean concentrations of S primarily as SO(2-)4 and Ca. Concentrations of Ag, As, Ba, Cd, Cr, Hg, Pb, and Se (except for ASTM Se in two samples) were below drinking water standards in both ASTM and TCLP leachates. Total toxicity equivalents (TEQ) of dioxins, for two FGD products used for mine reclamation, were 0.48 and 0.53 ng kg(-1). This was similar to the background level of the mine spoil (0.57 ng kg(-1)). The FGD materials were mostly uniform in particle size. Specific surface area (m2 g(-1)) was related to particle size and varied from 1.3 for bed ash to 9.5 for spray dryer material. Many of the chemical and physical properties of these FGD samples were associated with the quality of the coal rather than the combustion and SO2 scrubbing processes used.

Air Pollution↗
PubMed2003

The effect of drying and size reduction pretreatments on recovery of inorganic crop nutrients from inedible wheat residues.

Inorganic nutrients can be easily recovered from ALS crop residue solid wastes by aqueous leaching. However, oven drying and milling pretreatment of these residues has been frequently required to accommodate crop scientists and facility storage limitations. As part of a research study that will compare three different bioreactor technologies for processing these wastes, we realized that different drying and size-reduction pretreatments had been utilized for each technology. This paper compares the effects of residue pretreatment on recovery of nutrients by leaching. Pretreatments included three drying methods [fresh, oven-dried (70 degrees C overnight), and freeze-dried] and two size reduction methods [chopped (2 cm length) and milled (2 mm diameter)]. Determination of mass balances (dry weight and ash content of solids) before and after leaching indicated solubilization was least for fresh residues (23% dry weight loss and 50% for ash loss), and most for freeze-dried residues (41-47% dry weight loss and nearly 100% for ash loss). Mineral recovery of major elements (NO3, PO4, K, Ca, and Mg) in leachates was poorest for fresh residues. P and K recovery in leachates were best for oven-dried residues and Ca, Mg, and N recovery best for freeze-dried residues. The differences in recovery for N, P, and K in leachates were minimal between chopping and milling and slightly better for Ca and Mg from milled residues.

Biomass↗
PubMed1999

Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause?

In the southern Appalachian mountains a subcanopy species, Rhododendron maximum, inhibits the establishment and survival of canopy tree seedlings. One of the mechanisms by which seedlings could be inhibited is an allelopathic effect of decomposing litter or leachate from the canopy of R. maximum (R.m.) on seed germination, root elongation, or mycorrhizal colonization. The potential for allelopathy by R.m. was tested with two bioassay species (lettuce and cress), with seeds from four native tree species, and with three ectomycorrhizal fungi. Inhibitory influences of throughfall, fresh litter, and decomposed litter (organic layer) from forest with R.m. (+R.m. sites) were compared to similar extractions made from forest without R.m. (-R.m. sites). Throughfall and leachates of the organic layer from both +R.m. and -R.m. sites stimulated germination of the bioassay species above that of the distilled water control, to a similar extent. There was an inhibitory effect of leachates of litter from +R.m. sites on seed germination and root elongation rate of both bioassay species compared with that of litter from -R.m. sites. Native tree seed stratified in forest floor material from both forest types had a slightly higher seed germination rate compared with the control. A 2-yr study of seed germination and seedling mortality of two tree species, Quercus rubra and Prunus serotina, in field plots showed no significant influence of litter or organic layer from either forest type. Incorporating R.m. leaf material into the growth medium in vitro depressed growth of one ectomycorrhizal species but did not affect two other species. Leaf material from other deciduous tree species depressed ectomycorrhizal growth to a similar or greater extent as leaf material from R.m. In conclusion, R.m. litter can have an allelopathic effect on seed germination and root elongation of bioassay species as well as some ectomycorrhizal species. However, this allelopathic affect is not manifest in field sites and is not likely to be an important cause for the inhibition of seedling survival within thickets of R.m.

Journal Article↗
PubMed2001

Electrolytic removal of nitrate from crop residues.

The Controlled Ecological Life Support System (CELSS) resource recovery system, which is a waste-processing system,uses aerobic and anaerobic bioreactors to recover plants nutrients and secondary foods from the inedible biomass. Crop residues contain a significant amount of nitrate. There are actually two major problems concerning nitrate: 1) both CELSS biomass production and resource recovery consume large quantities of nitric acid, and 2) nitrate causes a variety of problems in both aerobic and anaerobic bioreactors. The nitrate anion causes several problems in the resource recovery system in such a way that removal prior to the process is highly desirable. The technique proposed to remove nitrate from potato inedible biomass leachate and to satisfy the nitric acid demand was a four-compartment electrolytic cell. In order to establish the electrolytic cell performance variables, experiments were carried out using potato crop residue aqueous leachate as the diluate solution. The variables studied were the potato biomass leachate composition and electrical properties, preparation of compartment solutions to be compatible with the electrolytic system, limiting current density, nutrients removal rates as a function of current density, fluid hydrodynamic conditions, applied voltage, and process operating time during batch recirculation operation. Results indicated that the limiting current density (maximum operating current density) was directly proportional to the solution electrical conductivity an a power function of the linear fluid velocity in the range between 0.083 and 0.403 m/s. During the electrolytic cell once-through operation, the nitrate, potassium, and other nutrient removal rates were proportional to the current density and were inversely proportional to fluid velocity. The removal of monovalent ions was found to be higher than divalent ones. Under batch recirculation operation at constant applied voltage of 4.5 and 8.5 V, it was found that the nutrient removal rates were independent of applied voltage, but were proportional to the ions concentration and operating time.

Anions↗
PubMed2001

Nitrogen leaching from soil treated with sludge.

The amount of sludge generated from urban centers is increasing more and more, so wastewater treatment plants are being constructed. Recycling of sludge by application to agricultural land can alleviate the disposal pressure, and, at the same time, utilize the plant nutrients in the waste. Organic nitrogen in sludge is mineralized to inorganic forms such as nitrate and ammonium that can be taken up by plants. The inorganic forms of nitrogen, especially nitrates, can easily be leached because of its negative charge. Not only do nitrates cause eutrophication, but, at high concentration in drinking water, can also cause chemical suffocation disease in babies. This work is meant to quantify nitrate and ammonium nitrogen leached from soil treated with sludge. In order to obtain information on the composition of leachate from sludge, Kandiustults and a lysimeter study were used. Municipal and industrial sludge were applied to completely random design plots at different rates: 125, 250 and 375 kg N/ha. Each control lysimeter was treated with chemical fertilizer (N-P2O5-K2O: 20-10-10) at the rate of 125 kg N/ha. After the Chinese kale (Brassica oleracea L.) was planted in each lysimeter, leachate was collected every week and analyzed for NO3- and NH4+. The experiment was conducted at Kasetsart University, Bangkhen Campus, Bangkok, Thailand. Average nitrogen leach in the form of NO3- was 25 times more concentrated than the NH4+. Nitrate concentrations in the leachate exceeded the drinking water standard. Nitrate and ammonium leaching were measured to be between 1.50-3.00% and 0.03-0.14% of the total treated nitrogen, respectively. Total nitrogen losses found in this study were 44.88%, 77.24% and 77.91% of the total nitrogen applied by chemical fertilizer, Huay Kwang sludge and Bangpa In sludge, respectively.

Agriculture↗
PubMed2001

[Preferential flow and its effect on solute migration in soil].

The characteristics of soil preferential flow and the preferential migrate in soil for non-absorptive bromide and nitrate ions were studied. With undisturbed and packed soil columns, the results showed that soil preferential flow was characterized with preferential breakthrough, non-symmetric breakthrough curve, lateral infiltration, tailing and so on. The preferential breakthrough for Br- was 24 hours after it was applied, and the leachate volume was only 0.04 times as-much as the pore volumes. The preferential flow for Br- accounted for 26% of total flux in the undisturbed soil columns. But the accumulative leachate mass for Br- resulted from the preferential flow were 86.7% of total accumulative leachate mass, showing that the soil preferential flow accounted for relative small ratio of the flux, but caused relative much more solute transference. NO3- was moved down rapidly by preferential flow at only one time as large as pore volumes, and got 11% of the applied amount, respectively. As a result of the preferential flow, the lateral infiltration flow enabled Br- and NO3- rapidly distribute and diffuse into the deeper soil.

Bromine↗
PubMed2001

[Leaching and vertical transport of Zirconium-95 in soils].

The leaching and vertical transport of Zirconium-95 in three representational soils (paddy soil, red-yellow earth and sea mud) in Zhejiang province and the influence of salinity on the activities of Zirconium-95 in sea mud were studied with soil-pole installation. The results show that: 1. The content of Zirconium-95 in collected leachate was low after passing through soil column with 250 ml, 500 ml, 750 ml leaching amount. The amount of Zirconium-95 in collected leachate of paddy soil, sea mud and red-yellow earth was about 5.33%-7.68%, 0.77%-1.32% and almost 0 of labelled amount respectively. And with increasing the total amount of leaching water, the content of Zirconium-95 in collected leachate varied indistinctively, which indicated that once Zirconium-95 was absorbed by soils, it was very difficult to desorb. 2. In paddy soil, red-yellow earth and sea mud, 45.99%-50.02%, 96.02%-97.16% and 95.94%-98.01% radioactivity of Zirconium-95 was concentrated in the 0.4 cm upper layer soils respectively, which illustrated that most of Zirconium-95 remained in the surface soils. 3. With the increase of salinity in leaching water, the amount of Zirconium-95 in surface soils (0-0.2 cm) presented obviously increased, which demonstrated that increasing salinity could raise the adsorption rate of Zirconium-95 in soils.

Kinetics↗
PubMed2001

[Bioreactor-landfill site for leaching solution treatment].

The study utilizes the system combined bioreactor with landfill site to treat leachate. The results show that the system helped the degradation of the organic pollutants in the leachate to be divided into two-phases, the hydrolytic fermentation and acid-production phases mainly occurred in the landfill site, the acidification rate was 40%-50%, the methane-production chiefly occurred in the bioreactor(UASB). It treated the leachate significantly and benefits the collection and utilization of methane gas. Also, the system accelerates the process of degrading municipal solid waste and stabilizing landfill site.

Bioreactors↗
PubMedDate not supplied

Phosphorus leaching from biosolids-amended sandy soils.

Increasing emphasis on phosphorus (P)-based nutrient management underscores the need to understand P behavior in soils amended with biosolids and manures. Laboratory and greenhouse column studies characterized P forms and leachability of eight biosolids products, chicken manure (CM), and commercial fertilizer (triple superphosphate, TSP). Bahiagrass (Paspalum notatum Flugge) was grown for 4 mo on two acid, P-deficient Florida sands, representing both moderate (Candler series: hyperthermic, uncoated Typic Quartzipsamments) and very low (Immokalee series: sandy, siliceous, hyperthermic Arenic Alaquods) P-sorbing capacities. Amendments were applied at 56 and 224 kg P(T) ha(-1), simulating P-based and N-based nutrient loadings, respectively. Column leachate P was dominantly inorganic and lower for biosolids P sources than TSP. For Candler soil, only TSP at the high P rate exhibited P leaching statistically greater (alpha = 0.05) than control (soil-only) columns. For the high P rate and low P-sorbing Immokalee soil, TSP and CM leached 21 and 3.0% of applied P, respectively. Leachate P for six biosolids was <1.0% of applied P and not statistically different from controls. Largo biosolids, generated from a biological P removal process, exhibited significantly greater leachate P in both cake and pelletized forms (11 and 2.5% of applied P, respectively) than other biosolids. Biosolids P leaching was correlated to the phosphorus saturation index (PSI = [Pox]/[Al(ox) + Fe(ox)]) based on oxalate extraction of the pre-applied biosolids. For hiosolids with PSI < or = approximately 1.1, no appreciable leaching occurred. Only Largo cake (PSI = 1.4) and pellets (PSI = 1.3) exhibited P leaching losses statistically greater than controls. The biosolids PSI appears useful for identifying biosolids with potential to enrich drainage P when applied to low P-sorbing soils.

Adsorption↗
PubMed2004

Microbial recovery of copper from printed circuit boards of waste computer by Acidithiobacillus ferrooxidans.

The bioleaching of copper contained in the printed circuit boards (PCB) of waste computers by A. ferrooxidans was studied. The Fe oxidation rates by A. ferrooxidans in the 9K medium supplemented with the leachate of PCB (0.15-0.13 g L(-1) d(-1)) were similar to that in the 9K medium without the leachate (0.15 g L(-1) d(-1)). This finding suggests that the leachate of PCB did not seriously affect the bioleaching process by this bacterium. The amount of copper leached from PCB shreds increased with the addition of ferrous ion and reached up to 5190 mg L(-1) when the initial concentration of Fe2+ ion was 7 g L(-1). As the microbial leaching progressed, pale brown precipitate was observed to form in the solution. Based on the total amount of copper, both in solution and precipitate, the optimal addition of ferrous ion for the leaching of copper was around 7 g L(-1). When citric acid was not added, only about 37 wt% of the total leached copper remained dissolved; however, the amount of dissolved copper increased to greater than 80 wt% in the presence of citric acid. This fact indicates that the addition of a complexing agent (citric acid) to the bioleaching solution can raise the solubility of the leached metal ions.

Acidithiobacillus↗
PubMed2005

Assessment of nitrogen excess in an agricultural area using a nitrogen balance approach.

A pilot study has been initiated to develop an approach for quantification of nitrogen excesses from agricultural activities that involve greenhouse farming in Kumluca Plain, Turkey. Detailed calculations utilizing the nitrogen balance method (NBM) were carried out at nine different locations within the plain over a time period of one year. The major contributing factors and governing operative mechanisms taken into consideration were nitrogen application rates both as organic and chemical fertilizers, irrigation water application practices, and nitrogen uptake by plants. The adopted approach yielded valuable information such as plant nitrogen uptake efficiencies, excess nitrogen, leaching rates and leachate nitrogen concentrations. Further, a site specific multiple linear regression model has been developed to estimate the ratio (N(leachate)/N(groundwater)) as a function of independent variables: farming age, excess nitrogen application and SEEPAGE Index Number. The negative sign of the model parameters implies that the ratio (N(leachate)/N(groundwater)) decreases as values of the independent variables increase. The adopted approach and the obtained results can beneficially be applied to similar sites to establish basic parameters of irrigation and fertilizer application operations.

Conservation of Natural Resources↗
PubMed2005

Leaching of metals on stabilization of metal sludge using cement based materials.

Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371.5 mg/L, 1.95 mg/L and 1.99 mg/L respectively. Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.

Aluminum Silicates↗
PubMed2005

Treatment of high strength wastewater with vertical flow constructed wetland filters.

The aim of the present study was to evaluate the behaviour of vertical flow constructed wetlands to treat high strength wastewater. Influents were obtained mixing tap water with different percentages of MSW landfill leachate (5%, 10% and 20%). Phragmites australis seedlings were used as macrophytes. The reeds were nurtured during three spring months, before the start of the experimental period. Three and four days of detention time were adopted. Influent concentrations of 510-2,050 mg L(-1), 180-740 mg L(-1) and 65-260 mg L(-1) were obtained for COD, N-NH4(+) and N-NO3(-), respectively. The environmental temperature averaged around 31.0 +/- 1.4 degrees C. During the experimental period, all parameters showed an increasing removal efficiency trend. Best results in terms of COD removal were obtained for mixtures at lowest rate of landfill leachate; while, denitrification process showed an opposite behaviour; finally, the removal of ammonia nitrogen appeared to be independent upon influent concentrations. Analysis carried out on the reed tissues showed a theoretic maximum storage of TKN in the leaves of about 55 mg/g dry weight. A leachate percentage of about 35% was derived to be able to fully inhibit the growth of macrophytes.

Biodegradation, Environmental↗
PubMed2006

Evaluation of water binding, seed coat permeability and germination characteristics of wheat seeds equilibrated at different relative humidities.

The relative binding of seed water and seed coat membrane stability were measured in two contrasting wheat (Triticum aestivum L) varieties, HDR 77 (drought-tolerant) and HD 2009 (susceptible) using seed water sorption isotherms, electrical conductivity (EC) of leachates and desorption-absorption isotherms. Analysis of sorption isotherm at 25 degrees C showed that the seeds of HDR 77 had significantly higher number of strong binding sites, with correspondingly greater amount of seed water as strongly bound water, as compared to HD 2009. Total number of binding sites was also higher in HDR 77 than HD 2009, which explained the better desiccation tolerance and higher capacity to bind water in seeds of HDR 77. EC of seed leachate in both varieties did not change with respect to change in equilibrium relative humidity (RII), indicating the general seed coat membrane stability of wheat seeds. However, absolute conductivity values were higher for HD 2009. showing its relatively porous seed coat membrane. Significantly lower area enclosed by the desorption-absorption isotherm loop in HDR 77, as compared to HD 2009 also indicated the greater membrane integrity of HDR 77. Germination and seedling vigour of HD 2009 were reduced when equilibrated over very low and very high RH. In contrast, germination and vigour in HDR 77 were maintained high, except at very high RH, indicating again its desiccation tolerance. Thus, the study demonstrated the relative drought tolerance of HDR 77, on the basis of seed water-binding characteristics and seed membrane stability. Seed membrane stability as measured by seed leachate conductivity or as area under dehydration-rehydration loop may be used as a preliminary screening test for drought tolerance in wheat.

Absorption↗
PubMed1999

Experimental designs and response surface modeling applied for the optimization of metal-cyanide complexes analysis by capillary electrophoresis.

The development of capillary zone electrophoresis (CZE) methods for the determination of metal cyanide complexes in real samples showed some problems, such as the low detection signal of Au (CN)2- and the low resolution between Ni(II) and Fe(II) cyanides in gold processing solutions, and the lack of separation of Pt(CN)4(2-) and Pd(CN)4(2-) in the leachates from automobile catalytic converters. To optimize some analytical parameters, the present study thus focused on the application of experimental designs and multiregression models. The following factors were examined by a two-level factorial design: applied voltage, injection time, detection wavelength, buffer ion, ionic strength and buffer modifiers. For optimization of the CZE method, subsequent response-surface experiments with the important factors were made with the two kinds of leaching solutions. Optimal analytical conditions were obtained in each case, giving good detection signals and resolution for the components of the studied leachates.

Cyanides↗
PubMed2000

Abundance of polymers degrading microorganisms in a sea-based solid waste disposal site.

In order to assess the degradability of plastics in solid waste disposal landfill sites, microbial populations capable of degrading five kinds of plastic-constituting polymers, poly epsilon-caprolactone (PCL), polylactic acid (PLA), polyethylene glycol (PEG), poly-beta-hydroxybutyrate (PHB) and cellulose acetate (CA), in a sea-based solid waste disposal site were investigated. Enumeration of aerobic and anaerobic polymers-degrading microorganisms (PDMs) was performed against to total 8 leachate samples, which were seasonally collected from the facultative pretreatment pond and the aerated lagoon. Both aerobic and anaerobic PDMs for natural polymers, PHB and CA, were found in all of the samples, while those for chemically-synthesized polymers, PCL, PLA and PEG, could not be always detected. In most cases, the ratios of the PHB- and CA-degraders to the heterotrophic bacterial population were more than 0.1%. On the other hand, the ratios of PCL-, PLA- and PEG-degraders were often much lower. These data indicate that the plastics degradation potential is commonly present in the studied disposal site, and that the degradation potential for plastics composed of chemically-synthesized polymers is inferior to that of natural polymers. Population sizes of the PDMs correlated to those of heterotrophic bacteria, and the counts of aerobic heterotrophic bacteria and PDMs in the aerated lagoon tended to be higher than those of anaerobic ones, indicating that the aeration of the leachate resulted in the activation of growth of whole aerobic microbial community including the PDMs.

Bacteria↗