Wood Leachate Research Articles

Antifungal activity of heat-treated wood extract against wood decay fungi

Using heat treatment for wood protection has been driven to maturity, but the role of heat-treated wood extracts in decay resistance has lacked attention. To assess the potential of heat-treated wood extract for wood preservation, the antifungal activity of the extract against wood decay fungi and the effects of the extract on fungal wood degrading enzyme activity and cell membrane integrity were tested. Small shavings generated during the processing of larch (Larix gmelinii (Rupr.) Kuzen) were heat-treated and extracted. The antifungal activity of extract against wood decay fungi and decay resistance of extract impregnated wood were tested to assess their potential. The effect of extracts on the enzyme activity of the white-rot fungus, Trametes versicolor (L.) Lloyd and the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. for wood degradation was assessed by detecting the activity of cellulose, hemicellulose, and ligninase of fungi incubated with extract. The effect of extracts on the integrity of cell membranes of fungi was assessed by staining with propidium iodide (PI) and the leakage detection of nucleic acid and protein in fungi after exposure to extract. The toxicity to freshwater luminescent bacteria (Vibrio qinghaiensis sp. -Q67) and mouse macrophages (RAW264.7) of the extract impregnated wood leachate was tested and compared with the leachate of the raw wood. The results denoted that the decay resistance of poplar (Populus tomentosa Carr.) wood could be improved by heat-treated larch wood extract, and the effect of the extract impregnated wood leachate on Q67 and RAW264.7 was the same as that of raw wood leachate. The extract inhibited ligninase activity (only for T. versicolor), cellulase activity, and respiratory metabolism of tested fungi, and impaired the membrane integrity. The study identified a potential wood preservative.

Defluoridation of water by the Homa* method, a co-precipitation technique using wood ash leachate and alum

High fluoride level in drinking water is an endemic public health concern in East Africa. Unlike in Kenya where it is absent, the Nalgonda technique, a defluoridation method that uses two chemicals, alum, and CaO, has seen mixed results in its application and adoption in Ethiopia and Tanzania. This has been due to the low capacity of communities to manage the process and the breakdown in the supply chain of chemicals used in the technique. In the present study, we attempted to bridge the gap in the chemical deficit by investigating the possible substitution of CaO with leachate from wood ash, a by-product of wood combustion commonly found in Kenya. The leachate was prepared from one part of wood ash mixed with two parts of distilled water and stirred for 24 hours followed by decantation. The new technique, the Homa method, using alum and wood ash leachate was then tested on H2O samples from three areas in Kenya with high F- concentrations ranging from 5.1 mg L-1, 9.1 mg L-1 to 91.0 mg L-1. The determination of F- concentration by SPADNS Spectrophotometry was applied throughout the experiment. Four levels of alum i.e. 1%, 2%, 3%, and 4% were dosed on five volumes of water i.e. 100, 200, 300, 400, and 500 ml raw water at 5.1 and 9.1 mg L-1 F-. For water samples at 91.0 mg L-1 F-, the same volumes were treated with 5 higher alum levels i.e. 5%, 6%, 7%, 8%, and 9%. The final pH was then adjusted to 7 with ash leachate for defluoridation. The set-up was a factorial design experiment where the final F- concentration was the dependent variable and the volume of raw water, the percentages, and volume of alum and wood ash leachate constituted the different factors. A fitted multivariate regression model of the general form; where Y = Residual fluoride, X = wood Leachate volume, W = alum Concentration, X*W = Interaction α, β, γ were regression coefficients, ε = error term, showed that only in the Baringo area did we have an interaction between wood ash leachate and alum concentration significant (p < 0.05). Defluoridation occurred (p < 0.05) at as low as 10% and as high as 99%, depending on the initial F- content. Total coliform decreased from 310, 290 and 270 count/l respectively to zero. Unfortunately, high chemical and TDS (from 558 mg L-1 to more than 9,000 mg L-1) enrichment were recorded in addition to the mixed data on turbidity. The overall results show that wood ash can substitute CaO in the Nalgonda process. Further investigation is however required to make it applicable for potable water production.

Novel Biodegradable Poly (Lactic Acid)/Wood Leachate Composites: Investigation of Antibacterial, Mechanical, Morphological, and Thermal Properties.

This research aimed to investigate the effects of using wood leachate (WL) powder as a cost-effective filler added to novel poly (lactic acid) biocomposites and evaluate their mechanical, thermal, morphological, and antibacterial properties. Fourier transform infrared spectroscopy (FTIR), tensile test, Charpy impact test, Shore hardness, scanning electron microscope (SEM), differential scanning calorimetry (DSC), contact angle, and bacterial growth inhibition tests were employed to characterize the developed biocomposites. The SEM results indicated a proper filler dispersion in the polymer matrix. WL powder improved the hydrophobic nature in the adjusted sample’s contact angle experiment. Markedly, the results showed that the addition of WL filler improved the mechanical properties of the fabricated biocomposites. The thermal analysis determined the development in crystallization behavior and a decline in glass transition temperature (Tg) from 60.1 to 49.3 °C in 7% PLA-WL biocomposites. The PLA-WL biocomposites exhibited an antibacterial activity according to the inhibition zone for Escherichia coli bacteria. The developed novel PLA-WL composites can be effectively utilized in various value-added industrial applications as a sustainable and functional biopolymer material.

Influence of wood leachate industrial waste as a novel catalyst for the synthesis of UF resins and MDF bonded with them

MDF (Medium Density Fiberboard) production processes produce a large amount of wood leachate as a hazardous waste. Wood leachate is a lignin-based waste material from the MDF production industry. It constitutes a potential environmental problem if discarded by penetrating into groundwater aquifers. Currently, there is no viable way for industrial MDF leachate waste to be transformed into environmentally friendly high value materials. The aim of this work was to present for the first time a novel approach which was successfully developed for the recovery of wood leachate industrial waste as a catalyst for the synthesis of UF adhesives for MDF panels. The leachates were examined by FTIR, 13 C NMR, and DSC as well as by evaluating the properties of fiberboards bonded with liquid UF resins. In addition, the other aim of this work was to capture the free formaldehyde gas emitted by MDF panels. It was of interest determine whether an MDF bonded panel prepared with a UF resin catalyzed by the wood leachate would exhibit lower formaldehyde emissions and the lowest thickness swelling, while still presenting a relatively good performance. The direct reuse of the fiberboard industrial leachate in the experiments demonstrated that the preparation method of the UF bonded fiberboard was environmentally friendly and sustainable. Therefore, this work arrived at some interesting conclusions that may be used as a base for future work on the recycling and reuse of MDF waste.

Toxicity of wood leachate to algae Desmodesmus subspicatus and plant Lemna minor.

Wood is one of the extensively used goods on the earth due to its large accessibility and usage in a wide range of human life. When woods are exposed to aquatic media, leachates are generated which may affect the quality of water and damage aquatic life into which they are discharged. This research seeks to evaluate the toxicity of linden (Tilia cordata), larch (Larix decidua) from the Czech Republic, cedrela (Cedrela odorata) and emire (Terminalia ivorensis) from Ghana wood leachates to two aquatic organisms (Desmodesmus subspicatus and Lemna minor). In algal and duckweed toxicity tests, these plants were exposed to different concentrations of wood leachate with nutrient medium creating concentration rates, 20, 30, 45, 67, and 100% v/v. High concentration of phenols and heavy metals may have contributed to toxicity. It was observed that the various wood leachates were inhibitory to the growth rate of algae and duckweed with emire exhibiting the highest toxicity with IC50 of 30.04% and 28.58% and larch the lowest toxicity with IC50 of 51.18% and 49.57% in relation to growth rate and chlorophyll respectively, hence indicating confirmed and potential toxicity of the various wood leachates to the aquatic organisms.

Ecotoxicological Effect of Aged Wood Leachates to Aquatic Organisms

Wood is an important natural resource used for various human activities. Toxicity of wood leachate in aquatic organisms has been previously established, but whether storage over time has an impact on the quality of leachate has not been assessed. Hence, this research seeks to assess the toxicity of aged wood leachate in aquatic organisms. Five fresh wood samples were randomly selected from the Oboyow forest reserve in the eastern region of Ghana: Mahogany (Khaya ivorensis), Cedrela (Cedrela odorata), Emire (Terminalia ivorensis), Wawa (Triplochiton scleroxylon), and Ceiba (Ceiba pendandra) to assess their toxicity to aquatic organisms. Algal (Desmodesmus subspicatus) duckweed (Lemna minor) and daphnia (Daphnia magna) were carried out using exposures to concentrations of 20%, 30%, 45%, 67%, and 100% v/v of wood leachate with control media, because they represented various concentration rate levels of wood leachate toxicity in the test organisms. The toxicity of the various wood leachates might be due to high levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC), i.e., metals and phenols. The % IC50 of the various wood leachate ranged from 21.51–66.77% with mahogany exhibiting the highest toxicity and wawa the lowest. It was also observed that toxicity of wood leachates decreased as the wood leachate aged. The % IC50 showed both confirmed and potential toxicity among the various wood leachates.

Assessing the effects of tropical wood leachate to Desmodesmus subspicatus, Lemna minor and Daphnia magna

Ghana has a long history as a major supplier of high-value hardwood timber and wood products to many countries. The research seeks to assess the effects of tropical wood leachates to aquatic organisms. Hence, five wood samples were selected; Mahogany (Khaya ivorensis), Cedrela (Cedrela odorata), Emire (Terminalia ivorensis), Wawa (Triplochiton scleroxylon) and Ceiba (Ceiba pendandra) from Oboyow forest reserve in Eastern Region- Ghana to assess their toxicity to aquatic organisms. Toxicity tests: Algal (Desmodesmus subspicatus) Duckweed (Lemna minor) and crustacean (Daphnia magna) were carried out using exposures to concentrations of 20, 30, 45, 67 and 100% v/v wood leachate in control media. The high levels of phenols measured in the various wood leachates was the main cause of toxicity. The percentage median Inhibition Concentration (%IC50) of the various wood leachate, ranged from 21.5 - 55.6% with mahogany exhibiting the highest toxicity and wawa the lowest. All the wood leachates were toxic to the aquatic organisms. The %IC50 showed both confirmed and potential toxicity among the various wood leachates and established that there was significant difference between various wood leachate toxicity.

Denitrifying Woodchip Bioreactor Leachate Tannic Acid and True Color: Lab and Field Studies

HighlightsOak leached more tannic acid, true color, and chemical oxygen demand (COD) than ash and mixed hardwood chips.The factors became similar (tannic acid, COD) or below stream levels (true color) after flushing.Eleven site-years of field bioreactor data showed decreasing tannic acid and true color over time.Post-startup tannic acid was lower in bioreactor outflow than in area streams.True color did not appear to be a reliable indicator of leachate tannic acid at low concentrations.Abstract. Woodchips have been a preferred denitrifying bioreactor medium to date, but concerns about potential harmful effects of tannins in the leachate have precluded the use of oak chips in many installations. A study was conducted to compare the suitability of oak (genus Quercus) woodchips as a denitrifying bioreactor medium relative to other types of woodchips, both in lab leachate tests and in the context of observed bioreactor leaching in the field. Assessment measures included the content of tannic acid and other compounds in the leachate, as well as leachate color, which can often be high during startup. An 84-day leaching test using rectangular bioreactor cells filled with either oak (Quercus rubra), ash (Fraxinus spp. L.), or a generic hardwood blend showed that oak initially leached higher concentrations of tannic acid, true color, and chemical oxygen demand (COD) than the other two media. The significant differences in leached concentrations among the three wood types were eliminated after a finite leaching period. Tannic acid and true color in 11 site-years of field bioreactor outflow data generally decreased over time, except following a dry period when one of the bioreactors received no drainage inflow for more than two months. The lab and field results indicated the capability of woodchip bioreactors to flush at least these two analytes to ambient stream levels. True color did not appear to be the best parameter for estimating the tannin content of woodchip leachate due to discrepancies at low concentrations. Mass normalized tannic acid leaching ranged from 0.03 to approximately 40 mg tannic acid g-1 woodchip across the lab and field assessments. Oak initially leached more tannic acid, color, and COD than the other wood types, but the eventual similarity among the wood types after flushing with a sufficient number of pore volumes meant that any potentially negative environmental impacts would likely be limited to the startup period or possibly after dry periods. Oak initially eluted higher mean total nitrogen (TN) concentrations than the other wood types, but the treatments were not significantly different by day 3, indicating that biological N removal was not significantly inhibited, even with high concentrations of tannic acid. Keywords: Chemical oxygen demand, Oak, Tannin, Water quality, Wood leachate.

Optimization of Electrospray Ionization for Liquid Chromatography Time-of-Flight Mass Spectrometry Analysis of Preservatives in Wood Leachate Matrix

Triazoles and 3-iodo-2-propynyl butylcarbamate (IPBC) are commonly used wood preservatives active against a wide range of fungi and bacteria. As they are prone to leaching, their amounts need to be monitored by the industry to determine preservative loss from the products and for environmental impact assessment. Therefore, a liquid chromatography–electrospray–time-of-flight mass spectrometry (LC–ESI–TOFMS) method was developed and optimized for simultaneous quantification of triazoles and IPBC in aqueous wood extracts, specifically wood leachate. Analyte pre-concentration on a solid-phase extraction cartridge prior to the analysis yielded > 94% recoveries. ESI method parameters (e.g., solvent system, electrolyte type, electrolyte concentration, capillary and fragmentor voltages) were selected based on an initial screening followed by an in-depth optimization via design of experiments. The optimal conditions employed an acetonitrile-water solvent system with 1.7 mM ammonium acetate, capillary voltage of 4350 V, and fragmentor voltage of 115 V. The developed method was applied to industrial wood leachate samples and the matrix-affected limits of detection were found to be 1.2–1.5 µg L−1 with interlay repeatability being < 7%.

Ecophysiological Responses of a Willow Cultivar (Salix miyabeana ‘SX67’) Irrigated with Treated Wood Leachate

As wood preservatives leach from exposed treated wood, they contaminate soil and water, creating an environmental problem that needs to be addressed. Treating this contamination is particularly challenging since it includes mixed compounds, such as heavy metals and trace elements, as well as xenobiotic organic pollutants like polychlorinated dibenzo-dioxin/furan congeners (PCDD/Fs) that are very toxic and are under very strict discharge regulations. Cultivating fast-growing willow shrubs, either in soil or in treatment wetlands, offers a flexible and inexpensive treatment option. The main objective of this study was to evaluate the tolerance of a frequently used willow cultivar (Salix miyabeana ‘SX67’) to irrigation with leachate contaminated with pentachlorophenol (PCP) and chromated chromium arsenate (CCA), two important wood preservatives. We designed a mesocosms experiment with willow grown in three different substrates and irrigated over 12 weeks with three different leachate concentrations. Willow proved to be tolerant to irrigation with the raw leachate, with only leaf area decreasing with increasing leachate concentration. However, the type of growing substrate influenced willow ecophysiological responses and overall performance, and seemed to affect contaminant dynamics in the plant-soil system. All contaminants accumulated in willow roots, and Cu and PCDD/Fs were also translocated to aerial parts. Overall, this study suggests that Salix miyabeana ‘SX67’ could be a good candidate for treating water or soil contaminated with wood preservatives.

Wood chip soil amendments in restored wetlands affect plant growth by reducing compaction and increasing dissolved phenolics

Adding chipped wood to soil ameliorates compaction, allowing faster plant growth that is critical to successful wetland restorations. Following the filling and planting of an erosion gully in Halstead Meadow, Sequoia National Park, the tallest leaf height and maximum clone width of transplanted Scirpus microcarpus seedlings were negatively correlated with soil compaction. Plant height decreased by 9.8 cm and width decreased by 11.9 cm per MPa of soil compaction (range of 0.74–4.50 MPa). We experimentally amended mineral soil in a test trench and found that every 0.10 cm3/cm3 addition of wood chips (range of 0.00–0.75 cm3/cm3) reduced compaction by 0.174 MPa. Had the Halstead Meadow gully fill contained an equivalent volume of wood chips to the reference area soil organic matter content (0.64 cm3/cm3), we predict compaction would have been reduced by 1.11 MPa, increasing individual transplant width spread by 36%, approximately doubling the vegetated area after two growing seasons. In a greenhouse phytometer experiment, conifer bark leachate (phenolics 211 mg/L) significantly reduced plant growth and, in the presence of added nutrients, increased the production of the enzyme polyphenol oxidase (PPO). However, phenolics concentration in bark‐free conifer wood leachate (12 mg/L), similar to field‐sampled concentrations, did not affect plant growth or PPO production. Pure conifer bark is not recommended as a soil amendment, but the addition of low‐bark‐content wood chips to gully fill may be a feasible and effective means of reducing soil compaction, accelerating plant establishment, and lowering wetland restoration project costs.

Soil-wood interactions: Influence of decaying coniferous and broadleaf logs on composition of soil fungal communities

Abstract Wood-inhabiting fungi may affect soil fungal communities directly underneath decaying wood via their exploratory hyphae. In addition, differences in wood leachates between decaying tree species may influence soil fungal communities. We determined the composition of fungi in 4-yr old decaying logs of Larix kaempferi and Quercus rubra as well as in soil directly underneath and next to logs. Fungal community composition in soil covered by logs was different from that in wood and uncovered soil and was clearly influenced by the tree species. Soil fungal species richness under logs was lower than in uncovered soil but higher than in decaying wood. The amount of exploratory hyphae of log-inhabiting fungi was only high close to decaying logs. In conclusion, there is a small but significant effect of decaying coniferous and broadleaf logs on soil fungal communities directly underneath logs, likely affected by differences in wood chemistry and fungal preference between tree species.

Novel biomaterials from citric acid fermentation as biosorbents for removal of metals from waste chromated copper arsenate wood leachates

The paper discusses the potential of different waste biomaterials for biosorption. Waste biomaterials after citric acid fermentation and chitosan extraction using Aspergillus niger were evaluated for biosorption of toxic metals (Cu, Cr and As) from leachates of chromated copper arsenate woods. The different waste BMs, such as fungal biomass (living and dead), alkali insoluble material and acid and alkali insoluble material were used in this study. The effect of different parameters, such as biosorbent concentration, metal concentration and contact time were investigated. The fitness of biosorption data for Freundlich and Langmuir adsorption models was investigated through batch adsorption technique. Among the adsorption isotherm tested, Langmuir isotherm gave the best fit with correlation coefficients (R2) value ranging from 0.89 to 0.97; 0.96–0.99 and 0.76–0.95 for As, Cr and Cu, respectively using solid state fermented biomass. Similarly, the significant removal of metals (>60% in leachate 2) from waste CCA wood leachate was achieved with the different BMs. Therefore, this study demonstrates the potential of CA fermentation derived waste BMs for biosorption of toxic metals from waste waters.

Occurrence and speciation of polymeric chromium(III), monomeric chromium(III) and chromium(VI) in environmental samples

Laboratory experiments suggest that polymeric Cr(III) could exist in aqueous solution for a relative long period of time. However, the occurrence of polymeric Cr(III) has not been reported in environmental media due partially to the lack of method for speciating polymeric Cr. We observed an unknown Cr species during the course of study on speciation of Cr in the leachates of chromated-copper-arsenate (CCA)-treated wood. Efforts were made to identify structure of the unknown Cr species. Considering the forms of Cr existed in the CCA-treated woods, we mainly focused our efforts to determine if the unknown species were polymeric Cr(III), complex of Cr/As or complex of Cr with dissolved organic matter (DOM). In order to evaluate whether polymeric Cr(III) largely exist in wood leachates, high performance liquid chromatography coupled with inductively coupled mass spectrometry (HPLC-ICPMS was used) for simultaneous speciation of monomeric Cr(III), polymeric Cr(III), and Cr(VI). In addition to wood leachates where polymeric Cr (III) ranged from 39.1 to 67.4%, occurrence of the unknown Cr species in other environmental matrices, including surface waters, tap and waste waters, was also investigated. It was found that polymeric Cr(III) could exist in environmental samples containing μg/L level of Cr, at a level up to 60% of total Cr, suggesting that polymeric Cr(III) could significantly exist in natural environments. Failure in quantifying polymeric Cr(III) would lead to the underestimation of total Cr and bias in Cr speciation. The environmental implication of the presence of polymeric Cr(III) species in the environment deserves further study.

Studies on Hydroxyl Radical Formation and Correlated Photoflocculation Process Using Degraded Wood Leachate as a CDOM Source

The iron-poor leachate from decaying wood can be an important source of colored dissolved organic matter (CDOM) in natural waters. In this study, we examined hydroxyl radical (•OH) formation with respect to photoreactivity of wood leachate DOM, the Fenton reaction, and photoflocculation. The relationship of •OH photoproduction rate and leachate optical properties (UV-visible absorption and fluorescence excitation-emission matrices (EEMS) coupled with PARAFAC analysis) were studied during irradiation in a UV solar simulator. The results showed that the •OH photochemical formation rate is strongly related to humic-like fluorescence as characterized by EEMS-PARAFAC analyses, and these fluorescence components are more photolabile than most of the other CDOM components. Fourier transform infrared spectroscopy (FT-IR) indicates the photodegradation of lignin-related structures. To examine the role of iron, Fe speciation (particulate Fe, organically-complexed Fe(II), organically-complexed Fe(III), free Fe(II), and free Fe(III)) were measured in the leachate samples amended with Fe. The addition of Fe accelerated •OH production substantially, and Fe was rapidly photochemically cycled between Fe(II) and Fe(III). The photodegradation of iron complexing ligands appears to play an important role in DOM photoflocculation.

Removal of organic pollutants from oak leachate in pilot scale wetland systems: How efficient are aeration and vegetation treatments?

This study investigated the effects of aeration and/or vegetation in experimental constructed wetlands (CWs) as mesocosms on the removal of pollutants in oak wood leachate. Twelve outdoor wetland mesocosms, with randomized replicated treatment combinations of vegetation (Phragmites australis) and aeration was monitored during the second and third year after construction. The investigation included control tanks with no aeration and no vegetation. The parameters monitored were polyphenols (PPs), chemical oxygen demand (COD) and water colour. The reduction of COD after 28 days was approx. 50% and more than 50% of PPs, whereas only 40% of the water colour was removed. Aeration increased the effect of both COD and PP removal. The vegetation treatment had a small but significant effect on removal of COD. The vegetation + aeration treatment, as well as aeration alone, increased the removal efficiency of COD from 9.5 g m−3 d−1 in the control to 11 g m−3 d−1. The results suggest that CWs can be used to treat stormwater contaminated by oak wood leachate. Further, it is suggested that the main processes for removal of pollutants in the leachate occur in the open-water habitat and that the hydraulic retention time is more important for removal than aeration and vegetation related processes.

Combined Ozone and Biological Treatment of Oak Wood Leachate

In the present study, we investigated the possibility of treating oak wood leachate with a combined ozone and biological treatment. Wood leachate is characterized by high amounts of organic carbon and is reported as being toxic to aquatic organisms. Ozone was used as a pre‐treatment before using aerobic degradation. The biological treatment was applied for seven days and evaluated using head‐space respirometry. Target pollutant in this investigation was polyphenols in combination with more general parameters, such as chemical oxygen demand (COD), total organic carbon (TOC) and colour. A custom made bubble column reactor was used, 1.5 L of wood leachate was exposed to 0–4 g/L of ozone, corresponding to a specific ozone dose between 0.7–7 g/L O3/g of initial COD. Oak wood leachate was found to be easily degraded by ozone, with &gt;90% of polyphenols degraded. COD was degraded by 73%, TOC by 61% and colour by 97% by ozone. Furthermore, a positive correlation between biodegradation and ozone pre‐treatment was found.

Treatment performance and copper removal mechanisms of a vegetated submerged bed receiving leachate from ACQ-treated lumber

Alkaline copper quaternary (ACQ), a wood preservative, consists of copper oxide and quaternary ammonium compounds. Its primary biocide, Cu, can be leached out by rainfall in outdoor storage piles of ACQ-treated lumber and disposal sites of decommissioned ACQ-treated wood. A vegetated submerged bed with a surface area of 0.19m2 was batch-operated to treat wood leachate generated in leaching piles during rainfall events over three growing seasons. The wetland was packed with pebbles and rubber mulch and planted with Phragmites australis. The wetland removed 93% of Cu on average after four initial cycles of batch operation, with effluent concentrations at 38–67μg/L on an annual basis. Removal efficiency was 7–80% for chemical oxygen demand, with effluent concentrations meeting the New York State benchmark monitoring cutoff for stormwater discharges associated with timber products sector in 24 out of 27 cycles. Leachate pH was increased to constantly meet the benchmark monitoring cutoff. Sorption to biofilms attached to wetland packing materials contributed 50% of total Cu removal. Pea pebbles had higher specific biofilm mass and subsequently accumulated more Cu than rubber mulch. Adsorption of Cu to pea pebbles accounted for 1.4% of Cu removal. Cu was accumulated to 27.3–31.1mg/kg in above-ground plant biomass and 39.0mg/kg in below-ground biomass, although plant uptake only contributed 4.4% of Cu removal. Cu contents in the growing and dead biomass were similar.

Particle size characterization of oak wood leachate: chemical oxygen demand and toxicity distribution within different fractions.

Oak wood leachate obtained from two storage facilities (storage pound and ditch) in a wood-based industry, and leachate generated by a laboratory leaching test, were characterized in seven categories regarding particle size distribution (PSD) (raw leachate, ≤ 20 μm, ≤ 10 μm, ≤ 1.2 μm, ≤ 13 nm, ≤ 5 nm and ≤ 2 nm). The PSD followed a normal distribution model with a correlation coefficient (r) varying from 82 to 88. Each fraction was analysed regarding chemical oxygen demand, polyphenols and acute toxicity in toxicity assays with Artemia salina, Vibrio fischeri and Lactuca sativa. Fractions with particles >1.2 μm were more toxic to A. salina and V. fisheri than fractions with particles ≤ 1.2 μm. No toxic effect was observed for L. sativa. The results suggest that polyphenols are the main toxic compounds in oak wood leachate. A conspicuous difference was found between field and laboratory samples.

Assessment of children's exposure to arsenic from CCA-wood staircases at apartment complexes in Florida

Arsenic exposure from wood treated with chromated copper arsenate (CCA) remains a concern due to its presence around homes. This study evaluated children's exposure to As from CCA-treated staircases through determination of bioaccessible soil As and measurements of dislodgeable As on hand railings, steps and surfaces of household objects impacted by CCA–wood leachate. Total As concentrations in 84 soil samples from 4 apartment complexes were elevated at 1.2–66.6mg/kg with bioaccessible As at 17–84%. Deterministic risk equations were used to estimate daily doses of As in children with estimates ranging from 0.41–54.9μg/day from ingestion of dislodgeable As. Lifetime average daily doses from ingestion of dislodgeable As and soil ranged from 8.1×10−6 to 3.0×10−5mg/kg/day, with estimated cancer risks being 1.2–4.5×10−5. Collectively, these results highlight potential health risks in children who have near-daily exposure to As from CCA-wood and are consistent with estimates generated by USEPA's SHEDS-Wood probabilistic exposure model.