Townsend Timothy G, Solo-Gabriele Helena, Tolaymat Thabet, Stook Kristin
Department of Environmental Engineering Sciences, University of Florida, P.O. Box 116450, Gainesville, FL 32611, USA.
Sci Total Environ. 2003 Jun 20;309(1-3):173-85. doi: 10.1016/S0048-9697(03)00047-0.
The production of landscape mulch is a major market for the recycling of yard trash and waste wood. When wood recovered from construction and demolition (C&D) debris is used as mulch, it sometimes contains chromated copper arsenate (CCA)-treated wood. The presence of CCA-treated wood may cause some potential environmental problems as a result of the chromium, copper, and arsenic present. Research was performed to examine the leachability of the three metals from a variety of processed wood mixtures in Florida. The mixtures tested included mixed wood from C&D debris recycling facilities and mulch purchased from retail outlets. The synthetic precipitation leaching procedure (SPLP) was performed to examine the leaching of chromium, copper and arsenic. Results were compared to Florida's groundwater cleanup target levels (GWCTLs). Eighteen of the 22 samples collected from C&D debris processing facilities leached arsenic at concentrations greater than Florida's GWCTL of 50 microg/l. The mean leachable arsenic concentration for the C&D debris samples was 153 microg/l with a maximum of 558 microg/l. One of the colored mulch samples purchased from a retail outlet leached arsenic above 50 microg/l, while purchased mulch samples derived from virgin materials did not leach detectable arsenic (<5 microg/l). A mass balance approach was used to compute the potential metal concentrations (mg/kg) that would result from CCA-treated wood being present in wood mulch. Less than 0.1% CCA-treated wood would cause a mulch to exceed Florida's residential clean soil guideline for arsenic (0.8 mg/kg).
景观覆盖物的生产是庭院垃圾和废木材回收利用的一个主要市场。当从建筑和拆除（C&D）废墟中回收的木材用作覆盖物时，有时会含有经铬酸铜砷酸盐（CCA）处理的木材。由于存在铬、铜和砷，经CCA处理的木材的存在可能会导致一些潜在的环境问题。开展了研究以检测佛罗里达州各种加工木材混合物中这三种金属的可浸出性。测试的混合物包括来自C&D废墟回收设施的混合木材以及从零售店购买的覆盖物。采用合成沉淀浸出程序（SPLP）来检测铬、铜和砷的浸出情况。将结果与佛罗里达州的地下水清理目标水平（GWCTLs）进行比较。从C&D废墟处理设施收集的22个样本中有18个浸出的砷浓度高于佛罗里达州50微克/升的GWCTL。C&D废墟样本的平均可浸出砷浓度为153微克/升，最高为558微克/升。从零售店购买的一个彩色覆盖物样本浸出的砷高于50微克/升，而从原始材料衍生而来的购买覆盖物样本未浸出可检测到的砷（<5微克/升）。采用质量平衡方法来计算木覆盖物中存在经CCA处理的木材时可能产生的金属浓度（毫克/千克）。经CCA处理的木材含量低于0.1%会导致覆盖物超过佛罗里达州住宅清洁土壤中砷的指导标准（0.8毫克/千克）。
