Wood Leachate Research Articles

Treatment of wood leachate with high polyphenols content by peat and carbon-containing fly ash filters

In the present study, two combinations of filter materials in filter/columns were examined for removal of total organic carbon (TOC) and polyphenols (PP) found in storm water runoff from wood storage areas in a wooden floor industry. One filter/column was packed with peat mixed with carbon-containing fly ash, while another filter/column contained only peat (without ash). The mixture of peat and ash has shown faster and higher removal capacity for TOC and faster removal with the same final removal capacity for PP (in grams of pollutant per kg of sorbent) at the saturation point. The superiority observed for the peat and ash filter is presumably due to the unique characteristics of peat and ash, which enhanced the treatment efficiency when used together in a mixture. Based on the observed results, filters formed by peat and carbon-containing ashes proved to be a potentially low-cost option for the treatment of storm water generated at storage areas of wood materials such as logs, sawdust and wood chips.

Influences of wood preservation, lumber size, and weather on field leaching of red pine lumber

Alkaline copper quaternary (ACQ) is a widely used wood preservative. This study evaluated leachate volume generation and contaminant leaching from ACQ-treated lumber during rainfall events in comparison to untreated lumber. The influences of wood preservation with ACQ, lumber size, and weather on leachate generation ratio and contaminant concentrations in wood leachate were investigated with four red pine lumber piles exposed to natural weather conditions. The average volumetric ratio of leachate to rainfall was significantly higher for the large-lumber piles (0.62) compared with the small-lumber piles (0.35). Less leachate was generated in the ACQ-treated lumber piles (0.42) than the untreated lumber piles (0.55). Leachate volume could be predicted with rainfall depth, air temperature, and wetted lumber surface area. Lumber size did not make a statistically significant difference in leachate quality except for zinc concentration. The average copper concentrations were 4034μg/L in the leachate from the ACQ-treated lumber piles and 87μg/L in the leachate from the untreated lumber piles. Moreover, ACQ treatment significantly increased leaching of arsenic and total dissolved solids. Copper concentration in leachate from ACQ-treated lumber can be predicted with rainfall intensity, the time interval between two consecutive leachate-generating events, rain copper concentration, and rain pH

Arsenic toxicity in the human nerve cell line SK-N-SH in the presence of chromium and copper

As, Cr, and Cu represent one potential combination of multiple metals/metalloids exposures since these three elements are simultaneously leached from chromated copper arsenate (CCA)-treated wood, a common product used for building construction, at levels that can be potentially harmful. This study investigated the neurotoxicity of As associated with CCA-treated wood when accompanied by Cr and Cu. The toxicity was evaluated on the basis of a cytotoxicity model using human neuroblastoma cell line SK-N-SH. The cells were cultured with CCA-treated wood leachates or with solutions containing arsenate [As(V)], divalent copper [Cu(II)], trivalent chromium [Cr(III)] alone or in different combinations of the three elements. The toxicity was evaluated using variations in cell replication compared to controls after 96h exposure. Among the three elements present in wood leachates, As played the primary role in the observed toxic effects, which were exerted through multiple pathways, including the generation of oxidative stress. DOM affected the absorption of metals/metalloids into the test cells, which however did not obviously appear to impact toxicity. As toxicity was enhanced by Cu(II) and inhibited by Cr(III) at concentrations below U.S. EPA’s allowable maximum contaminant levels in drinking waters. Thus assessing As toxicity in real environments is not sufficient if based solely on the result from As.

Wood Leachate Remains an Issue of the Forest Industry

Wood in outdoor applications is usually pressure treated with preservatives. Since the 1970s, the majority of the woods used in outdoor residential settings have been treated with chromate copper arsenate (CCA). The most common formulation of CCA (type C) contains 47.5% as CrO3, 18.5% as CuO, and 34% as As2 O5 . Effective 31 December 2003, no wood manufacturer may treat wood with CCA for residential uses in the U.S.

Investigation into Heterotrophic Activities and Algal Biomass in Surface Flow Stormwater Wetlands

Stormwater wetlands have been mainly designed in an empirical approach for water quality improvement, with little quantitative understanding of the internal microbia l processes. This study investigated into heterotrophic bacterial pro duction rate, heterotrophic bacterial mineralization percentage, and algal biomass in hypertrophic and eutrophic surface flow stormwat er wetlands. Compared to a nearby wood leachate treatment wetland, the stormwater wetlands had much higher chlorophyll-a concentrations. The eutrophic stormwater wetland had improved water quality, whereas the hypertrophic stormwater wetland had degraded water quality. Heterotrophic bacterial activities in wate r were limited in the stormwater wetlands due to competition of algal gro wth for nutrients. The relative contribution of biofilms to the overal l heterotrophic activities was higher in the stormwater wetlands th an that in the wood leachate treatment wetland. Keywords—chlorophyll-a, constructed wetland, heterotrophic production, mineralization, stormwater

Selective recovery of Cr and Cu in leachate from chromated copper arsenate treated wood using chelating and acidic ion exchange resins

The purpose of this study was to selectively remove chromium and copper from CCA-treated wood acid leachates (initial concentrations of 447–651 mg As l −1, 374–453 mg Cu l −1 and 335–622 mg Cr l −1) using ion exchange resins and precipitation techniques. Batch experiments revealed that the chelating resin Dowex M4195 had a high copper selectivity in the presence of chromium while the Amberlite IR120 resin had a high chromium sorption capacity. Combining M4195 and IR120 resins in four successive columns, made with Plexiglas tube, led to 96% copper extraction and 68% chromium extraction. NH 4OH (4 M) efficiently eluted copper from the chelating resin while H 2SO 4 (10% v/v) was used for IR120 resin elution. Copper and chromium recovery by elution reached 94% and 81%, respectively. Successive sorption and elution steps using M4195 and IR120 ion exchange resins presented similar metal removal capacities over the five cycles. No resin deterioration was observed but the results suggested arsenic bulk diffusion into the M4195 resin. Successive treatments of CCA-treated wood leachate with M4195 and IR120 allowed for copper and chromium removal while arsenic could be extracted by coagulation treatment with ferric chloride and precipitation with Ca(OH) 2 at pH 5.7. This final process led to 99.9% arsenic removal. The final effluent contained less than 1 mg l −1 of arsenic, chromium and copper.

Combined evaluation of durability and ecotoxicity: A case study on furfurylated wood

Modified wood is commercially available and merchandized as a new, environmentally friendly and durable wood species. However, there are no standards focusing on the evaluation of modified wood. Combining resistance against fungal decay and good ecotoxicological properties may be a start. In this study softwood and hardwood species were furfurylated using different treatment processes and treating solutions. The durability was determined by exposing the treated wood to a range of Basidiomycetes and the ecotoxicity was studied on two aquatic organisms. It was the purpose to come to a strategy and how to unite efficacy and ecotoxicity, since this is important in product development. The results show that the selection of fungus used for mass loss determination and the choice of ecotoxicity method is decisive, confirming that a combination of methods is valuable. A tiered approach to find the optimal treatment seems the best option. First, adequate protection against wood-rotting fungi should be attained, followed by ecotoxicity evaluation of the wood leachates. If necessary, the optimization process should be repeated until both durability and ecotoxicity are within satisfactory limits. This process could be extended with other evaluation criteria, e.g. dimensional stability of the modified wood or a risk analysis of its leachate.

Impact of Surface Water Conditions on Preservative Leaching and Aquatic Toxicity from Treated Wood Products

New alternative wood preservatives contain higher levels of copper (Cu) which can promote aquatic toxicity in natural water systems. Earlier work focused on evaluating toxicity using laboratory generated leaching solutions. In this study, the impact on preservative leaching and aquatic toxicity from treated wood products was evaluated using natural surface waters including waters from two rivers, three lakes, two wetlands, and one seawater, in addition to synthetic moderate hard water and deionized water. Blocks of wood treated with Cu based alternatives such as alkaline copper quaternary (ACQ) and copper boron azole (CBA), along with chromated copper arsenate (CCA)-treated wood, were leached under quiescent conditions, and total Cu, labile Cu, and heavy metal toxicity were measured. Results show that ACQ- and CBA-treated wood leach approximately 10 and 20 times more total Cu relative to CCA-treated wood and that the presence of organic and inorganic ligands in natural waters lowered the labile fraction of Cu relative to that from laboratory generated leaching solutions. Aquatic toxicity was found to correlate with the labile Cu fraction, and hence, the aquatic toxicity of the treated wood leachates was lower in natural waters in comparison to laboratory leaching solutions. The results of the present study suggest that studies designed to evaluate the impacts of treated wood should therefore consider the role of complexation in reducing the labile Cu fraction and its potential role in decreasing toxicity.

Toxicity of untreated wood leachates towards two saltwater organisms ( Crassostrea gigas and Artemia franciscana)

Wood is widely used in the development of freshwater, estuarine and marine coastlines. Timbers last according to their content of naturally occurring preservatives (mostly phenols and aldehydes), produced to prevent decay from biotic agents. When untreated woods are exposed to aquatic media, leachates are generated with likely toxic effects on the target environment. The potential impact on saltwaters of leachates from some untreated timbers of both native and tropical species has been assessed. The leaching procedure was set up considering British Standard test methods for paints and OECD guidelines for wood preservatives emission scenarios. Toxicity was monitored via the acute toxicity test with the brine shrimp Artemia franciscana and the sub-chronic embryotoxicity test with the oyster Crassostrea gigas. Brine shrimps evidenced no toxic effects while oysters discriminated well among leachates: the tropical wood species showed similar or relatively lower toxic effects than the native ones according to both leaching cycles (24 and 72 h). The ecotoxicological data have been integrated with some physical and chemical parameters.

Effects of Smoke and Fire-related Cues on Penstemon barbatus Seeds

Previous research has found that exposure to fire-related cues enhances germination of some plant species, and such species may exist in frequent-fire southwestern United States Pinus ponderosa forests. I performed four greenhouse experiments with Penstemon barbatus, a perennial forb common in P. ponderosa forests, testing seed responses to liquid and air smoke, charred P. ponderosa wood and leachate, heat and emergence substrates. Liquid smoke increased P. barbatus emergence to as high as 63%, 44% greater than controls, and enhanced emergence in all 4 experiments. Air smoke produced by burning P. ponderosa litter for 15 min appeared to increase emergence similar to liquid smoke. In contrast, P. ponderosa charred wood and charred wood leachate did not improve emergence, and sometimes inhibited positive effects of smoke. Heating samples at 100 C for 30 min did not affect emergence. Substrate and liquid smoke interacted in one experiment, with smoke increasing emergence more sharply on basalt and potting soil than on limestone soil. These greenhouse findings have practical implications for germinating P. barbatus, but need testing under field conditions to evaluate their importance in this species' population biology after fire in P. ponderosa forests.

Metal Transport and Bioavailability in Soil Contaminated with CCA-Treated Wood Leachates

A laboratory study was conducted to investigate metal transport and accumulation within soils contaminated with As, Cr, and Cu from CCA-treated wood leachates. New blocks of CCA-treated wood were leached using synthetic rainwater. Soil columns were constructed and filled with three different soils, including a sandy soil, an organic soil and a clay soil. The leachate was applied intermittently until 80 pore volumes were eluted through each column. Metal concentrations (Cu, Cr, and As) were measured in the leachate before passage through the columns as well as in each elutriate fraction collected. Chemical analysis was complemented with toxicity testing using Ceriodaphnia dubia, Selenastrum capricornutum, and MetPLATE™. Following application of 80 pore volumes of leachate, the columns were dissected and the profile of the metal concentrations within each column was determined. A comparison of the arsenic, chromium and copper leaching patterns found arsenic to be the most mobile, with copper the most retained in the soil columns (As < Cr < Cu). Transport patterns of As differed in the three soil types, with observed mobility highest in the sandy soil and lowest in the clay soil. The three metals accumulated in the top layer of soil. Arsenic posed the greatest risk when soil concentrations were compared to risk-based target levels. Although metals were detected in soil elutriates, no toxicity was detected in any of the soil column elutriates using any of the three toxicity assays.

Arsenic speciation of solvent-extracted leachate from new and weathered CCA-treated wood.

For the past 60 yr, chromate-copper-arsenate (CCA) has been used to pressure-treat millions of cubic meters of wood in the United States for the construction of many outdoor structures. Leaching of arsenic from these structures is a possible health concern as there exists the potential for soil and groundwater contamination. While previous studies have focused on total arsenic concentrations leaching from CCA-treated wood, information pertaining to the speciation of arsenic leached is limited. Since arsenic toxicity is dependent upon speciation, the objective of this study was to identify and quantify arsenic species leaching from new and weathered CCA-treated wood and CCA-treated wood ash. Solvent-extraction experiments were carried out by subjecting the treated wood and the ash to solvents of varying pH values, solvents defined in the EPA's Synthetic Precipitation Leaching Procedure (SPLP) and Toxicity Characteristic Leaching Procedure (TCLP), rainwater, deionized water, and seawater. The generated leachates were analyzed for inorganic As(III) and As(V) and the organoarsenic species, monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA), using high-performance liquid chromatography followed by hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS). Only the inorganic species were detected in any of the wood leachates; no organoarsenic species were found. Inorganic As(V) was the major detectable species leaching from both new and weathered wood. The weathered wood leached relatively more overall arsenic and was attributed to increased inorganic As(III) leaching. The greater presence of As(III) in the weathered wood samples as compared to the new wood samples may be due to natural chemical and biological transformations during the weathering process. CCA-treated wood ash leached more arsenic than unburned wood using the SPLP and TCLP, and ash samples leached more inorganic As(III) than the unburned counterparts. Increased leaching was due to higher concentrations of arsenic within the ash and to the conversion of some As(V) to As(III) during combustion.

Toxicity and chemistry of aspen wood leachate to aquatic life: field study.

A dark, toxic leachate has been observed around woodpiles of trembling aspen (Populus tremuloides Michx.) cut in winter for pulp or structural lumber. We measured production of leachate from 18 m3 of harvestable aspen logs stacked in an open field near Dawson Creek, British Columbia, Canada. The logpile began producing leachate during the first winter thaw and continued to do so for the duration of the two-year study (mean, 250 L/collection). Aspen leachate was characterized by dark color, acidic pH (5.0-6.5), elevated conductivity (200-500 microS/cm), high to very high biochemical oxygen demand (500-5,000 mg/L) and total organic carbon concentrations (500-2,000 mg/L), variable levels of phenolic compounds (2-27 mg/L), and low dissolved oxygen tensions (<2 mg/L). In tests with rainbow trout (Oncorhynchus mykiss), Daphnia magna, and luminescent bacteria, the leachate varied from weakly toxic (median lethal concentration, >10%) to very toxic (median lethal concentration, <1%). The volume of leachate generated by the logpile was correlated with total precipitation (rain or snow) since the last collection. Loads of chemical constituents or toxicity (lethal concentration x volume) in the leachate did not decline over the duration of the study. Less than 10% of the total mass of leachable material in the aspen logs was removed during two years of exposure.

Assessment of relative environmental risk from logyard run-off in British Columbia

Run-off is generated at logyards at sawmills and dryland sorts when mobile water interacts with woody debris. Logyard run-off can contain a range of constituents with the potential to have an adverse impact on the receiving environment. Many geoclimatic, operational and physical factors contribute to the volume and characteristics of run-off, and a management tool to predict relative environmental risk from different sites would be of value. In this study, we attempted to develop such a tool. A survey was devised and distributed to logyard operators in British Columbia. The survey provided information on site characteristics, volumes and types of wood processed, operational practices, the incidence of run-off, run-off treatment practices, as well as the ultimate receiving environment. Qualitative and quantitative data from the survey were subjected to statistical analyses to: (1) determine the factors that contributed to risk; (2) assign relative risk ratings to each site; and (3) rank facilities according to their potential to impact the receiving environment. Multidiscriminant analysis was used to determine which factors were correlated to environmental risk posed by run-off. Eighty-nine percent (64/72) of the facilities had visible run-off. Sixty-six percent (42/64) of the facilities fell into the high risk category with the remaining 34% (22/64) being low risk. In order of importance, volume of wood stored onsite (largest contribution), frequency of run-off events and colour intensity of run-off (smallest contribution) were factors that significantly contributed to risk and were correlated positively. The methods employed in this study could be applied as management tools to identify sites for further assessment and evaluate the need for remediation. Key words: wood leachate, run-off, logyard, dryland sort, environmental impact, toxic, remediation

Biodegradation and detoxification of wood leachate from pentachlorophenol‐treated poles

AbstractThe pentachlorophenol (PCP) in leachate, generated from size‐reduced PCP‐treated poles, was degraded using a mixed culture containing Arthrobacter sp. in cyclic batch bioreactors in non‐sterile conditions. Complete degradation of PCP was achieved for a five‐month period for a concentration of 50 mg PCP/L and 12 h cycle time. The adsorbable organic halogen (AOX) concentration of the reactor effluent was reduced by two orders of magnitude compared to the feed, and the chemical oxygen demand (COD) was reduced by 50%. The increase in chloride ion concentration also suggests that PCP was mineralized to end products. In tests to increase the process throughput, complete degradation of PCP was also achieved in the cases for 120 mg PCP/L and a 12 h cycle time or 50 mg PCP/L and a 6 h cycle time. Daphnia magna toxicity tests showed that the presence of PCP in leachate caused toxicity, and the biodegradation of PCP resulted in significantly reducing the effluent toxicity to a value similar to that of PCP‐free nutrient solution.

Acetylcholinesterase, an old biomarker with a new future? Field trials in association with two urban rivers and a paper mill in Newfoundland

Biological markers are sensitive, cost effective tools for identifying risks of environmental contamination. The cytochrome P450-linked mixed-function oxygenase (MFO) system has been extensively validated in the environment, not only in association with point sources of pollution, but also in association with contamination over broad geographical areas. However, there is a recognized need for the establishment of biomarkers for assessing a variety of toxicological endpoints. With respect to neuromuscular functions, a recent study in the North Sea has indicated that the ‘old’ biomarker, acetylcholinesterase (ACHE), which is sensitive to selected organophosphate and carbamate pesticides, may be responding to low levels of contaminants in the environment, putatively by compounds other than, or in addition to, pesticides. We now provide evidence for such a possibility. A distinct depression of ACHE was found in muscle tissues of trout ( Salmo trutta) taken from two urban rivers in St. John's (Virginia River and Rennie's Mill River), in comparison with a nearby reference river (South Brook). Most striking was the fact that depression was observed in the 50% range. A similar high level of enzyme depression was observed in muscle tissues of flounder ( Pleuronectes americanus) taken in the area of a pulp and paper mill (Birchy Bay in the Bay of Islands), in comparison with a nearby reference site. Depression of ACHE was associated with induction of MFO enzyme activity (ethoxyresorufin-O-deethylase) in liver tissues of both trout and flounder. We provide evidence and discussion that contaminants other than pesticides, including compounds in complex mixtures of combustion hydrocarbons and natural wood leachate, could be responsible for the depressed ACHE levels observed in our studies (as well as those in the North Sea) and suggest that this old biomarker may have a new future in biological monitoring and assessment programmes.

Toxicity of aspen wood leachate to aquatic life: Laboratory studies

AbstractTrembling aspen (Populus tremuloides Michx.), a common hardwood tree throughout Canada, is being harvested at increasing rates for use in paper and building materials. Piles of aspen logs have been observed to produce a dark, watery, acutely toxic leachate. A laboratory study was undertaken to elucidate the nature, strength, and persistence of aspen leachate toxicity and the chemical composition of the leachate. Leaching from aspen chips in the laboratory was rapid, with 1% mass loss in the first 24 h. Another 2 weeks of immersion was necessary to remove all remaining leachable material (3% total). Fresh aspen leachate derived from a 1:9 wood‐water mixture (35 d immersion) was characterized by amber color, low pH (4.0), extremely high BOD (&gt;2,600 mg/L), and high conductivity (1140 μS/cm). The leachate was rich in phenols (30 mg/L), organic carbon (2,480 mg/L), and organic nitrogen (13 mg/L). Median acutely toxic concentrations of leachate were consistently 1 to 2% of full strength for trout and Daphnia. Inhibition of bacterial metabolism began at concentrations below 0.3%. Leachate was less toxic to plant life but inhibited algal growth at concentrations of 12 to 16%. Toxicity of aspen leachate persisted at the same level as in fresh leachate for more than 2 months unless artificial aeration was provided. Persistence was even greater at low temperature (5°C). Aged leachate underwent a transition marked by a rise in pH and dissolved oxygen concentration, a small decline in conductivity, and a color change, from amber to black. Toxicity declined abruptly when the supply of labile toxicants was exhausted, but it sometimes increased again from the products of microbial metabolism. Oxygen depletion, low pH, and phenolic compounds contribute to the toxicity of aspen leachate, but much of the toxic effect must be attributed to other, unidentified constituents.

Effects of river red gum, Eucalyptus camaldulensis, litter on golden perch, Macquaria ambigua

Aquaria with added river red gum, Eucalyptus camaldulensis, litter became hypoxic, with decreased pH and contained up to 30 mg 1−1 tannin and lignin. Survival of golden perch, Macquaria ambigua, larvae in aquaria treated with a simulated annual litter density of 450 g m−2 for 72 h was 14·9% for 15‐day‐old larvae and 0% for 8‐day‐old larvae. A litter density of 1223 g m−2 resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m−2 litter treatments compared to 89·8% in aerated controls and 86·8% in non‐aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight‐day‐old larvae exposed to bark and wood leachates (0·001–10 g 1−1) exhibited an initial period of hyperactivity, followed by a concentration‐dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four‐month‐old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1−1 for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose‐dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats unsuitable as nursery areas for native fish.

Clinotactic responses of Larval Silver Perch (Bidyanus bidyanus) and Golden Perch (Macquaria ambigua) to simulated environmental gradients

Larval silver perch (Bidyanus bidyanus) and golden perch (Macquaria ambigua) were subjected to gradients of light, depth, flow and wood leachate from river red gum (Eucalyptus camaldulensis) as well as a control treatment with no gradient. Both species were strongly attracted to light, while golden perch larvae were also attracted to river red gum and were carried downstream by water flow. Neither species displayed any response to depth. Gradient responses of silver perch were significantly more variable (P &lt; 0.05) than those of golden perch, which may result in silver perch larvae being more widely distributed in floodplain habitats. Golden perch larvae may be more closely associated with inundated river red gum than silver perch larvae.