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PubMed2005

Phyllosphere nitrogen relations: reciprocal transfer of nitrogen between epiphyllous liverworts and host plants in the understorey of a lowland tropical wet forest in Costa Rica.

Epiphyllous bryophytes on tropical rainforest plants acquire nutrients from throughfall and free-living N2-fixing organisms, but may also depend directly on host leaf leachates. By contrast, after drying events bryophytes lose significant quantities of nutrients through leaching that can be taken up by host leaves. To assess a potential nutritional interdependency, nitrogen fluxes between epiphyllous liverworts and their host leaves (Carludovica drudei, Costus laevis, Dieffenbachia concinna, Pentagonia wendlandii) were quantified by in situ15N-labelling techniques in a lowland rainforest, Piedras Blancas National Park, Costa Rica. Depending on host species, epiphyllous bryophytes met between 1 and 57% of their N demand from host leaf leachates. Externally supplied 15N was taken up both by epiphylls and host leaves, but N from epiphyll leachates accounted for < 2.5% of host leaf N after 14 d. Long-term observations (180 d) demonstrated the highly dynamic nature of phyllosphere N of the investigated tropical rainforest understorey and an intermittent sink capacity of epiphyllous bryophytes.

Costa Rica↗
PubMed1987

Microbially mediated leaching of low-sulfur coal in experimental coal columns.

The leaching of a low-sulfur bituminous coal was investigated with experimental coal columns subjected to simulated rainfall events. Leachates from the columns became dominated by iron-oxidizing bacteria as evidenced by specific enrichment cultures and measurements of CO(2) assimilation. Heterotrophic microorganisms were also present in the coal leachates, but their numbers and activity decreased with decreasing pH. This pattern could be reversed by increasing the pH of the coal with lime. Organosulfur-utilizing bacteria made up a substantial portion of the heterotrophic community. Measurements of microbial activity in coal cores indicated that although much of the microbial community remained associated with coal particles, the relative abundance of heterotrophs and autotrophs in leachate seemed to reflect that in coal cores. When bacterial growth was delayed by autoclaving coal samples, acid production and leaching of iron and sulfur were also delayed. Rapid leaching of materials from coal thus appears to be strongly dependent on the presence of the natural bacterial microflora.

Journal Article↗
PubMed2002

The bioreactor landfill: its status and future.

The bioreactor landfill provides control and process optimisation, primarily through the addition of leachate or other liquid amendments. Sufficient experience now exists to define recommended design and operating practices. However, technical challenges and research needs remain related to sustainability, liquid addition, leachate hydrodynamics, leachate quality, the addition of air, and cost analysis.

Bioreactors↗
PubMed2003

A framework to contain a spatially distributed model of the degradation of solid waste in landfills.

This paper describes the concept and development of a generic spatially distributed numerical model that can contain and link sub-models of landfill processes in order to simulate solid waste degradation and gas generation in landfills. The model has been designed to simulate anaerobic degradation of solid waste saturated in leachate, and to reflect the effect on degradation of the control of both the flow and chemistry of the leachate in the pore space of the solids. The model can accommodate different profiles of waste constituents and therefore has the potential to simulate the effects of pre-treatment techniques such as shredding and inoculation. Components of the model simulate the transport of leachate and gases, and the consolidation of the solid waste. The results of some prototype calculations are presented.

Environmental Pollutants↗
PubMed2004

Effect of sintering temperature on the properties and leaching of incinerator bottom ash.

The fine particle size fraction of municipal solid waste incinerator bottom ash is often problematic because reuse applications for this material are limited. In these experiments incinerator bottom ash with a particle size of less than 8 mm was processed using conventional ceramic production techniques involving wet milling, drying, compacting and sintering. The effect of sintering temperature on the sintered density, microstructure, acid neutralization capacity (ANC) and the release of metal ions as a function of leachate pH are reported. Sintering at 1080 degrees C produced samples with maximum density. This material contained diopside (CaMgSi2O6), clinoenstatite (Mg2Si2O6) and wollastonite (CaSiO3) as the major crystalline phases. The acid neutralization capacity of sintered samples is significantly lower than milled bottom ash, and further reduces as the sintering temperature increases. This is associated with reduced leaching of Ca from sintered ash samples under all leachate pH conditions. Heavy metals present in the incinerator bottom ash included Cr, Cu, Ni, Zn, Cd and Pb. Sintering under optimum conditions reduced the leachable fraction of these metals under aggressive acid conditions (leachate pH 3) by factors ranging from 90% for Ni to greater than 99% for Cr, Cd, Zn and Pb.

Ceramics↗
PubMed2001

In vitro cytotoxicity evaluation of plastic biomedical devices.

Cytotoxic potential of four plastic biomedical devices (intravenous transfusion sets, IV sets; dextrose normal saline bottles, DNS bottles; Ringer lactate bottles, RL bottles; and Ryle's tubes) including 17 different brands was evaluated by investigating growth inhibition, percent survival, mitotic index and colony-forming ability (cfa) in L929, an adherent type mouse fibroblast cell line. Experimental sets were exposed with leachates of biomedical products in serum-free minimum essential medium (MEM) for 1 h at 37 degrees C in a CO2 incubator. After 1 h, medium was replaced with serum rich MEM containing essential amino acids and reincubated up to 96 h. Cells in serum-free MEM only were processed under identical conditions and served as the control. The leachates from all types of biomedical devices evaluated exhibited reduction in the growth and survival of the cell line in the first 12 h postexposure followed by their gradual recovery up to 96 h. A significant reduction in cell growth was apparent in the six brands of IV sets from 24 h onwards up to 36 h (59% growth inhibition). Though the cfa was also reduced in all the brands tested, the magnitude of reduction was less compared to growth inhibition. The results indicate that leachates of IV sets were more toxic compared to other biomedical devices screened, and growth inhibition assay was found to be more sensitive and suitable for cytotoxicity evaluation of biomedical devices.

Animals↗
PubMed1978

Transport and transportation pathways of hazardous chemicals from solid waste disposal.

To evaluate the impact of hazardous chemicals in solid wastes on man and other organisms, it is necessary to have information about amounts of chemical present, extent of exposure, and chemical toxicity. This paper addresses the question of organism exposure by considering the major physical and biological transport pathways and the physicochemical and biochemical transformations that may occur in sediments, soils, and water. Disposal of solid wastes in both terrestrial and oceanic environments is considered. Atmospheric transport is considered for emissions from incineration of solid wastes and for wind resuspension of particulates from surface waste deposits. Solid wastes deposited in terrestrial environments are subject to leaching by surface and ground waters. Leachates may then be transported to other surface waters and drinking water aquifers through hydrologic transport. Leachates also interact with natural organic matter, clays, and microorganisms in soils and sediments. These interactions may render chemical constituents in leachates more or less mobile, possibly change chemical and physical forms, and alter their biological activity. Oceanic waste disposal practices result in migration through diffusion and ocean currents. Surface area-to-volume ratios play a major role in the initial distributions of chemicals in the aquatic environment. Sediments serve as major sources and sinks of chemical contaminants. Food chain transport in both aquatic and terrestrial environments results in the movement of hazardous chemicals from lower to higher positions in the food web. Bioconcentration is observed in both terrestrial and aquatic food chains with certain elements and synthetic organics. Bioconcentration factors tend to be higher for synthetic organics, and higher in aquatic than in terrestrial systems. Biodilution is not atypical in terrestrial environments. Synergistic and antagonistic actions are common occurrences among chemical contaminants and can be particularly important toxicity considerations in aquatic environments receiving runoff from several terrestrial sources.

Animals↗
PubMed2004

Effect of prairie grass on the dissipation, movement, and bioavailability of selected herbicides in prepared soil columns.

Phytoremediation of pesticide-contaminated sites using a prairie grass mixture (big bluestem, yellow indiangrass, and switch grass) has been suggested as a low-cost in situ remediation strategy. In this study, the proposed phytoremediation technique was applied to artificially prepared soil columns that were fortified with high concentrations of four herbicides (atrazine, alachlor, metolachlor, and pendimethalin). The fate and toxicity of the herbicides were compared with results from soil columns lacking vegetation. After either 150 or 240 d of phytoremediation, soils were watered with 7.5 cm of water, and leachate was collected. Columns were then divided into three sections (top, middle, bottom). For each section of the column, chemical analysis (ethyl acetate and water extractions), earthworm accumulation tests, and lettuce seedling growth tests were performed. The leachate was chemically analyzed and tested for chronic toxicity to algae. Atrazine and alachlor degraded rapidly in the column, and the total amount recoverable was less than 2% of applied. After 250 d, vegetation reduced the total recoverable amounts of metolachlor and pendimethalin by 78 and 39%, respectively. Metolachlor was the only compound found in leachate, and the amounts recovered were reduced 5- to 20-fold by vegetation. Vegetation decreased the bioavailability of pendimethalin as measured by 8-d, earthworm bioaccumulation factors (BAFs) and lettuce seedling growth assays. Decreases in mobility and bioavailability indicate that this technique may stabilize pesticide residues in addition to increasing dissipation rates.

Animals↗
PubMed2005

Effects of sulfachlorpyridazine in MS.3-arable land: a multispecies soil system for assessing the environmental fate and effects of veterinary medicines.

A multispecies soil system (MS.3) has been used to evaluate the ecological effects of veterinary pharmaceuticals in soil as a result of routine agricultural practices. Different experimental conditions were tested and the variation of the different parameters was evaluated for a final design. A protocol for the MS.3-arable land is presented here. Emergence of seedlings, plant elongation and biomass, earthworm mortality, and soil microbial enzymatic activities have been selected as toxicological endpoints for soil organisms. Toxicity tests were conducted with the leachate on aquatic organisms (in vitro fish cell lines, daphnids, and algae). The system was used for assessing the effects of the antimicrobial sulfachlorpyridazine that was tested in triplicate at concentrations of 0.01, 1, and 100 mg/kg. The chemical was mixed uniformly with a 20-cm depth soil column to resemble the distribution of manure within arable soil. Reversible and nonreversible effects on soil enzymatic activities were observed at 1 and 100 mg/kg, respectively. Earthworms were not affected. Significant reduction of plant elongation and biomass was observed at the highest concentration. Degradation and leaching contributed to the dissipation of sulfachlorpyridazine from the soil column. The undiluted leachate was highly toxic to Daphnia magna. The parent chemical was assumed responsible for the leachate toxicity although the role of mobile metabolites could not be excluded fully. No significant effects were observed for green algae Chlorella vulgaris and for the rainbow trout established cell lines RTG-2 (rainbow trout gonads) and RTL-WI (rainbow trout liver). The MS.3 system offers a cost-effective experimental approach to measure simultaneously fate and effects of chemicals on a realistic soil system under controlled laboratory conditions. The advantages of using MS.3-effect endpoints are discussed.

Agriculture↗
PubMed2002

Methods for toxicity assessment of contaminated soil by oral or dermal uptake in land snails: metal bioavailability and bioaccumulation.

Using two biological characteristics of the land snail (subspecies Helix aspersa aspersa and Helix aspersa maxima), i.e., soil eating and crawling on wet surfaces, methods were developed to assess the bioavailability of heavy metals (Cd, Cr, Pb, and Zn) from soil and aqueous leachates of soil. Measurement of heavy-metal concentrations in soil, leachates, and soft tissues of snails showed that contamination from ingested soil is the major route for metal uptake. Generally, the concentrations of metals were greater in the viscera than in the foot and rose with the proportion of spiked soil (Sl) in the diet. After ingestion of soil, bioaccumulation factors in the viscera were over two for Cd (3.5-27) and Zn (1.7-4.4) for both subspecies but were below one for Cr (0.04-0.6, except for H. aspersa maxima: 1.21) and Pb (0.02-0.23). Contamination by leachate Sl mainly caused accumulation of Cr in the tissues. Determining the metal burden per snail enables an estimation to be made of the risk of secondary poisoning encountered by predators. The present study provides data on the bioavailability of metals in soils and on the relationships between bioaccumulation and sublethal effects.

Animals↗
PubMedDate not supplied

Sources of salinity near a coal mine spoil pile, north-central Colorado.

A small (1 km2) salt-affected stream drainage on the High Plains north of Denver, Colorado was sampled to determine the near-surface dispersion of soluble salts and metals from low-sulfur coal mining waste (spoil). Surface waters collected along the 0.8-km stream reach, and aqueous leachates of spoil and naturally saline local soil, were analyzed for chemical constituents and sulfur isotopes. In this semiarid setting with abundant carbonate-bearing surficial sediments, the limited, mildly acidic drainage from the spoil pile is quickly neutralized, restricting the mobility of many elements. However, some spoil-derived constituents were clearly traceable within the upper 0.4 km of the stream reach. Spoil leachates and surface water near the spoil pile have distinctive compositions of major anions and cations, and elevated levels of dissolved nitrate compared with downstream waters. Spoil-derived sulfate was traceable because it has generally positive values of delta34S that contrasted with generally negative values of delta34S in soil leachates and evaporite salts from the surrounding area. Spatial-chemical sampling of surface water showed an abrupt increase in dissolved U, Se, B, Li, and Mn in the lower 0.4 km of the stream reach where shallow ground water from surrounding irrigated fields contributed to surface flow. The downstream evolution of surface water chemistry and sulfur isotopic composition is consistent with mixing between spoil-affected upstream water and irrigation-return water. The methods described should be applicable at other sites in similar settings where the environmental effect of low-sulfur coal mining waste must be assessed and where access to samples of shallow ground water is limited.

Coal↗
PubMedDate not supplied

Coupled effects of treated effluent irrigation and wetting-drying cycles on transport of triazines through unsaturated soil columns.

The physical and chemical parameters controlling the movement of atrazine (6-chloro-N2-ethyl-N4-isopropyl-l,3,5-triazine-2,4-diamine; 98.8%) and prometryn [N,N'-bis(1-methylethyl)-6-(methylthio)-l,3,5triazine-2,4-diamine; 99.5%] were investigated in columns infiltrated with treated effluent under unsaturated transient conditions and subjected to drying events at 22 or 60 degrees C followed by rewetting. Three soils varying in soil pH and texture and three solutions were used. The infiltrating solutions consisted of either a CaCl2 matrix (CC), a swine waste-derived lagoon effluent (SW), or a simulated buffer solution (SB) representative of the element composition and pH of the SW but with no dissolved organic matter. Several parameters were monitored including leachate triazine concentrations, pH, dissolved organic carbon (DOC), inorganic carbon, and flow rates. Compared with CC, application of SW and SB increased column leachate pH, enhanced dissolution of organic carbon and particle dispersion, and decreased average flow rates, which allowed for increased desorption time. The coupled effect of these processes enhanced movement of triazines in some cases, with SW generally having the greatest effect. The individual effect of increased pH was more pronounced for prometryn (pKa=4.05) versus atrazine (pKa=1.66), and most dramatic for the soil with the lowest initial pH. High-temperature drying, which simulated intensive evaporation, further enhanced the dissolution of soil organic matter and the reduction in leachate flow rates with SW and SB applications; however, the net effect under the experimental conditions employed varied with soil type. Relative to low-temperature drying, high-temperature drying in the silty clay loam-packed columns reduced pesticide migration.

Atrazine↗
PubMedDate not supplied

Ryegrass cover crop effects on nitrate leaching in spring barley fertilized with 15NH415NO3.

Cover crops are a management option to reduce NO3 leaching under cereal grain production. A 2-yr field lysimeter study was established in Uppsala, Sweden, to evaluate the effect of a perennial ryegrass (Lolium perenne L.) cover crop interseeded in barley (Hordeum vulgare L.) on NO3-N leaching and availability of N to the main crop. Barley and ryegrass or barley alone were seeded in mid-May 1992, in lysimeters (03-m diam. x 1.2-m depth) of an undisturbed, well-drained, sandy loam soil. Fertilizer N was applied at the same time as labeled l5NH415NO3 (10 atom % 15N) at a rate of 100 kg N ha(-1). In 1993, barley was reseeded in May in the lysimeters but with nonlabeled NH4NO3 and no cover crop (previous year's cover crop incorporated just prior to seeding). Barley yields and total and fertilizer N uptake in Year 1 (1992) were unaffected by cover crop. Total aboveground N uptake by the ryegrass was 28 kg ha(-1) at the time of incorporation the following spring. Recovery of fertilizer-derived N in May 1993 was about 100%; 53% in soil, 46% in barley, <2% in ryegrass, and negligible amounts in leachate. In May 1994, the corresponding figures were: 32% in soil, <3% in barley, and, again, negligible amounts in leachate. The cover crop reduced concentrations of NO3-N in the leachate considerably (<5 mg L(-1), compared with 10 to 18 mg L(-1) without cover crop) at most sampling times from November 1992 to April 1994, and reduced the total amount of NO3-N leached (22 compared with 8 kg ha(-1)).

Agriculture↗
PubMedDate not supplied

Fertilizer use efficiency and nitrate leaching in a tropical sandy soil.

Maize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996-1997, 1997-1998, and 1998-1999) in field lysimeters repacked with a coarse-grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr(-1) (1395 mm rainfall) in 1996-1997, 296 to 335 mm yr(-1) (840 mm rainfall) in 1997-1998, and 606 to 635 mm yr(-1) (1387 mm rainfall) in 1998-1999. Mineral N fertilizer, especially the high rate (120 kg N ha(-1)), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L(-1)) and NO3 losses (up to 56 kg N ha(-1) yr(-1)) in 1996-1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha(-1) yr(-1)), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha(-1)) plus 60 kg N ha(-1) fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses.

Environmental Monitoring↗
PubMed2005

Phosphorus leaching at cold temperatures as affected by wastewater application and soil phosphorus levels.

Land application of wastewater in the northern-tier United States during winter months has been suggested as a means to reduce cost of building storage lagoons. A study was initiated in 1996 to assess land application of potato-processing wastewater on a 120-ha field at Park Rapids, MN. One objective of this study was to evaluate the effects of soil P levels and temperature on P leaching in soil columns. In this paper, we report the P sorption, desorption, and leaching characteristics of a high-P (>200 mg kg(-1)) and a low-P (<25 mg kg(-1)) surface soil from the wastewater irrigation site. The leaching experiment was done with wastewater at 4 +/- 2 or 10 +/- 2 degrees C. The high-P soil resulted in an equilibrium P concentration of 8.0 mg L(-1) compared with 0.14 mg L(-1) for the low-P soil. When low-P wastewater was applied to the high-P soil, the soil acted as a P source, and the total phosphorus (TP) concentration in the leachate was 3.5 times higher than the input TP concentration (C0). When high-P wastewater was applied to the high-P soil, the soil acted as a P sink retarding the TP concentration in the leachate by 80%. Phosphorus desorption was higher at 10 degrees C compared with 4 degrees C. The results showed that depending on P levels of the soil and the wastewater, reduction or increase in leachate P will occur below the surface soil. However, further mobility of this P under field conditions will depend on the volume and rate of percolating water as well as the sorption-desorption characteristics of the subsoil.

Adsorption↗
PubMedDate not supplied

Degradation and mobility of linear alkylbenzene sulfonate and nonylphenol in sludge-amended soil.

Degradation and mobility of the surfactants linear alkylbenzene sulfonate (LAS) and nonylphenol (NP) were investigated in a lysimeter study using a sandy loam soil and 45-cm soil columns. Anaerobically digested sewage sludge was incorporated in the top-15-cm soil layer to an initial content of 38 mg LAS and 0.56 mg NP kg(-1) dry wt., respectively. Spring barley (Hordeum vulgare L.) was sown onto the columns. The lysimeters were placed outdoors and therefore received natural precipitation, but were also irrigated to a total amount of water equivalent to 700 mm of precipitation. Leachate and soil samples from three soil layers were collected continuously during a growth period of 110 d. Leachate samples and soil extracts were concentrated by solid-phase extraction (SPE) and analyzed using high performance liquid chromatography (HPLC) with fluorescence detection. The concentrations in the top-15-cm soil layer declined to 25 and 45% of the initial contents for LAS and NP, respectively, within the first 10 d of the study. At the end of the study, less than 1% LAS was left, while the NP content was below the detection limit. Assuming first-order degradation kinetics, half-lives of 20 and 37 d were estimated for LAS and NP, respectively. The surfactants were not measured in leachate samples in concentrations above the analytical detection limits of 4.0 and 0.5 microg L(-1) for LAS and NP, respectively. In addition, neither LAS nor NP were measured in concentrations above the detection limits of 150 and 50 microg kg(-1) dry wt., respectively, in soil layers below the 15 cm of sludge incorporation, indicating negligible downward transport of the surfactants in the lysimeters.

Alkanesulfonates↗
PubMed2006

An axenic plant culture system for optimal growth in long-term studies.

The symbiotic co-evolution of plants and microbes leads to difficulties in understanding which of the two components is responsible for a given environmental response. Plant-microbe studies greatly benefit from the ability to grow plants in axenic (sterile) culture. Several studies have used axenic plant culture systems, but experimental procedures are often poorly documented, the plant growth environment is not optimal, and axenic conditions are not rigorously verified. We developed a unique axenic system using inert components that promotes plant health and can be kept sterile for at least 70 d. Crested wheatgrass (Agropyron cristatum cv. CDII) plants were grown in sand within flow-through glass columns that were positively pressured with filtered air. Plant health was optimized by regulating temperature, light level, CO2 concentration, humidity, and nutrients. The design incorporates several novel aspects, such as pretreatment of the sand with Fe, graduated sand layers to optimize the air-water balance of the root zone, and modification of a laminar flow hood to serve as a plant growth chamber. Adaptations of several sterile techniques were necessary for maintenance of axenic conditions. Axenic conditions were verified by plating and staining leachates as well as a rhizoplane stain. This system was designed to study nutrient and water stress effects on root exudates, but is useful for assessing a broad range of plant-microbe-environment interactions. Based on total organic C analysis, 74% of exudates was recovered in the leachate, 6% was recovered in the bulk sand, and 17% was recovered in the rhizosphere sand. Carbon in the leachate after 70 d reached 255 microg d(-1). Fumaric, malic, malonic, oxalic, and succinic acids were measured as components of the root exudates.

Agropyron↗
PubMed2006

Leaching of N-nitrosodimethylamine (NDMA) in turfgrass soils during wastewater irrigation.

N-nitrosodimethylamine (NDMA) is a carcinogenic by-product of chlorination that is frequently found in municipal wastewater effluent. NDMA is miscible in water and negligibly adsorbed to soil, and therefore may pose a threat to ground water when treated wastewater is used for landscape irrigation. A field study was performed in the summer months under arid Southern California weather conditions to evaluate the leaching potential of NDMA in turfgrass soils during wastewater irrigation. Wastewater was used to irrigate multiple turfgrass plots at 110 to 160% evapotranspiration rate for about 4 mo, and leachate was continuously collected and analyzed for NDMA. The treated wastewater contained relatively high levels of NDMA (114-1820 ng L(-1); mean 930 ng L(-1)). NDMA was detected infrequently in the leachate regardless of the soil type or irrigation schedule. At a method detection limit of 2 ng L(-1), NDMA was only detected in 9 out of 400 leachate samples and when it was detected, the NDMA concentration was less than 5 ng L(-1). NDMA was relatively persistent in the turfgrass soils during laboratory incubation, indicating that mechanisms other than biotransformation, likely volatilization and/or plant uptake, contributed to the rapid dissipation. Under conditions typical of turfgrass irrigation with wastewater effluent it is unlikely that NDMA will contaminate ground water.

Biodegradation, Environmental↗