Toxicity of Aspen Wood Leachate to Aquatic Life: Laboratory Studies

Abstract

Abstract-Trembling 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 (Ͼ2,600 mg/L), and high conductivity (1140 S/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 (5ЊC). 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.

Wastewater Treatment and Reclamation: A Review of Pulp and Paper Industry Practices and Opportunities

“…However, if such materials were to be discharged into rivers, lakes, and estuaries at excessive levels, the resulting biological metabolism would sometimes be sufficient to consume all or most of the available dissolved oxygen, leading to the death of fish and other aquatic life (Taylor et al 1996;Chhonkar et al 2000). Such impacts are often quantified by measuring the BOD.…”

In-woods chipping: Possible evidence for allelochemical interaction of leachate generated from trembling aspen (Populus tremuloides Michx.) bark and wood waste

“…This waste has the potential of creating large amounts of leachate containing solubilized compounds from decaying aspen bark, wood and leaves. Leachate generated from decked aspen logs and waste bark and wood is toxic to aquatic organisms (Goudey and Taylor 1992, Taylor 1994, Taylor et al 1996; aqueous extracts of P. tremuloides leaves decreased the growth of several grass species (Younger et al 1980); tissue culture extracts of P. tremuloides demonstrated antimicrobial activity (Mathes 1963) while leaf extracts of a closely related species, P. tremula, showed anti-fungal properties (Olsen et al 1971). …”

Effects from log-yard stormwater runoff on the microalgae Scenedesmus subspicatus

“…Those authors observed that higher toxic effects on the early stages of the runoff were gradually reduced, and that 90% of toxic effects were associated with the first 20% of the total runoff volume. Even though the toxic effects posed by wood-related compounds have been demonstrated [9,10,11,6,4], little is know concerning the intra-storm magnitude, variability and possible existence of toxic first flushes from stormwater runoff generated in log-yards. The aim of this paper was to evaluate the magnitude and the intra-storm variability of the toxic effects posed by stormwater runoff originated from a log-yard during single storm events.…”