ABSTRACT
Six wood decks of Southern Yellow Pine were constructed in Coral Gables, Florida (a suburb of Miami) to expose 2100 cm2 of the wood surface to rainfall for 1 year, during which weekly rain runoff samples were collected from a leachate collection tank. The six experimental decks included two that were made of new untreated boards and new Alkaline Copper Quat (ACQ) boards. The remaining 4 decks were all made of weathered CCA-treated wood and consisted of low concentration boards in replicates (LCCAa and LCCAb), Medium Concentration Boards (MCCA), and a High Concentration Marine Piling (HCCA) that weathered above
1 INTRODUCTION
Release of Arsenic (As) from CCA-treated wood is one of the major anthropogenic sources of As contamination in the US. The wood treatment industry voluntarily withdrew the treated products for most residential settings effective from January 1, 2004, resulting in a substitution with copper-only wood preservatives, in particular Alkaline Copper Quat (ACQ). However, the problem will exist for a long time for its continuous utilization in several areas, such as industrial applications, structures in marine environments and load bearing components of structures in terrestrial environments, and its long service life even for the wood sold for residential and industrial uses prior to 2004 (Hason et al. 2012). In addition to As, Chromium (Cr) and copper (Cu) are also simultaneously leached from CCA-treated wood at levels potentially harmful to aquatic organisms (Weise & Weise 2006). Therefore, exposure associated with CCA-treated wood should in reality be a co-exposure of As, Cr, and Cu as opposed to As alone model. Our understanding of the toxicity of these elements in natural leachate associated with CCA-treated wood is limited. The
Organic Carbon (DOC) in the wood leachates ranged from 11.3 to 58.8 mg/L, with an average of 28.8 mg/L. Cells did not survive in wood leachates directly because of the lack of nutrients and appropriate pH values. Therefore, culture media were prepared by first concentrating the wood leachates and then diluting with complete medium prior to applying leachates to the cells. For evaluation of Dissolved Organic Matter (DOM) effects, two different sources (untreated wood extract and humic acid) of DOM containing solution were used.
