Transport and interaction of arsenic, chromium, and copper associated with CCA-treated wood in columns of sand and sand amended with peat
Introduction
Chromated-copper-arsenate (CCA)-treated wood was widely used for the construction of outdoor structures in the United States since 1970s. Since both arsenic (As) and chromium (Cr) have been classified as human carcinogens (IARC, 2007, PA, 2009), the potential risks of exposure to As and Cr from the sources associated with CCA-treated wood commanded intensive attention over the last decade (Saxe et al., 2007, Solo-Gabriele et al., 2008). Copper (Cu) has also raised concerns due to its potential adverse effects on aquatic organisms (Weis and Weis, 2006). Due to the pressure from increased public awareness and risk assessments conducted by various regulatory groups (U.S.CPSC, 2003, U.S.EPA, 2005), the wood treatment industry voluntarily withdrew the treated products for most residential settings effective from January 1, 2004. However, the utilization of new CCA-treated wood will continue for several uses, including industrial applications, structures in marine environments and load bearing components of structures in terrestrial environments. Even for the CCA-treated wood sold for residential and industrial uses prior to 2004, metal release will likely continue for at least several decades due to its long service life (Khan et al., 2006). Consequently, a better understanding of the fate, transport, and transformation of all three elements in soil substrate is needed for current uses, for disposal and for remediation of soil contaminated with CCA-treated wood.
In the leachate from CCA-treated wood, arsenate, As(V), is the predominate species and a small proportion of arsenite, As(III) can also be observed (Khan et al., 2006). Cr(III) is the main species in the leachate from treated wood (Song et al., 2006, Pan et al., 2009), despite Cr(VI) presents in the original treatment solution. Chromium in the treated wood mainly exists as Cr/As complex or as Cr(OH)3 (Nico et al., 2004). Once released to soil, the rate and the extent of adsorption of As, Cr and Cu on soil are determined by their species and by the soil physicochemical characteristics (Chirenje and Ma, 2006). Microbial redox transformations are important (if not the principal) drivers controlling environmental As and Cr speciation (Feng et al., 2005, Li et al., 2007). Soil physicochemical characteristics determine the bioavailability of these elements, which is a key factor for microorganism-facilitated transformation.
Considerable progress has been made in recent years in understanding As, Cr, and Cu leachability from soils affected by CCA-treated wood. However, information on the effect of soil characteristics and microorganism activity on leaching of all three elements and the potential interactions among these elements during the leaching in soil is scarce. Previous studies revealed that the amount of As, Cr, and Cu leached from CCA-treated wood was not proportional to their concentrations in the original formulation (Stefanovic and Cooper, 2006). Considering the distinct differences in physicochemical properties of these elements, it is expected that their leachability and the factors controlling their migration in soil could be different. Since these elements could exist in high concentrations in the leachate, competitive or enhanced adsorption of the cation or anion on soil in the multiple adsorbate system can become significant (Benjamin, 1983).
The objective of this work was to study the transport and transformation of As, Cr, and Cu in soils associated with CCA-treated wood with an emphasis on the potential interactions among the three elements and the key factors controlling the species transformation and transport in soil. Our previous studies on As leaching from soils indicated that the organic matter content and microorganism activity plays an important role on controlling the transport and transformation of As in soils (Feng et al., 2005, Chen et al., 2006, Chen et al., 2008). Therefore, these two factors were selected in this study and assessed on their roles in the transport and transformation of As, Cr, and Cu in soil. In order to more clearly elucidate what is happening in the column, simplified soil substrate, sand and sand amended with peat were employed. This study was accomplished through a laboratory scale soil column experiment.
Section snippets
Chemicals and materials
Individual As(III) and As(V) stock solutions (1000 mg L−1) were prepared by dissolving appropriate amounts of sodium metaarsenite (98%, Aldrich) and sodium hydrogen arsenate heptahydrate (98%, Aldrich) in water. ICP-MS grade standards for Cr(III) (10 000 mg L−1 in 5% HNO3), Cu(II) and Cr(VI) (1000 mg L−1 in 5% HNO3) were purchased from Ricca Chemicals Company. An ICP-MS grade standard solution used for total As analyses (1000 mg L−1 in 5% HNO3) was purchased from GSF Chemicals, Inc. Water used in the
Results
Elevated As concentrations in the leachate (Fig. 1, As) were observed on the 3rd day from the columns with peat (SP and SPF), and the leaching of As reached steady state within 13 d. Slower increases in As concentrations were observed from columns without peat (S and SF) with measureable increases in As appearing in the effluent by the 8th day. The time to reach steady state was different for S and SF columns. Arsenic in the effluent solution from S column reached steady state on day 13th,
Transport and transformation of As
Adding peat to sand significantly increased As mobility (Fig. 2). Generally, the mobility of As in the natural aquatic environment is controlled by adsorption/desorption on the soil. The adsorption/desorption of As on hydrous metal oxides, such as Fe2O3, Al2O3 or MnO2, has been considered as one of the main mechanisms controlling As mobility (Kumpiene et al., 2009). The presence of dissolved organic matter (DOM) can alter the As adsorption by forming As–DOM complexes (Wang and Mulligan, 2009).
Conclusions
Arsenic, copper and chromium, simultaneously leached at high concentration levels associated with CCA-treated wood, have the distinct leaching behavior and may behave differently in soil substrates compared with the situation of a single element because of the possible interactions between these elements. Therefore, prediction of the fate of As, Cr, and Cu associated with CCA-treated wood in the environment and the health effect on human should take into account all these three elements
Acknowledgments
This study was partially supported by NIEHS ARCH (S11 ES11181) and NIH-MBRS (3 S06 GM008205-20S1) programs. We thank Professors G. Snyder and J. Cisar for providing the soil samples. This is contribution # 456 of Southeast Environmental Research Center at FIU.
References (43)
- et al.
X-ray absorption spectroscopic study of the sorption of Cr(III) at the oxide–water interfaces, II. Adsorption, coprecipitation, and surface precipitation on hydrous ferric oxide
J. Colloid Interf. Sci.
(1992) - et al.
Role of soil-derived dissolved substances in arsenic transport and transformation in laboratory experiments
Sci. Total Environ.
(2008) Surface reaction of chromium in soils and waters
Geoderma
(1995)- et al.
Role of surface precipitation in copper sorption by the hydrous oxides of iron and aluminum
J. Colloid Interf. Sci.
(1999) - et al.
Stabilization of As, Cr, Cu, Pb and Zn in soil using amendments – a review
Waste Manage.
(2008) - et al.
Impact of water saturation level on arsenic and metal mobility in the Fe-amended soil
Chemosphere
(2009) - et al.
The role of humic substances in chromium sorption onto natural organic matter (peat)
Chemosphere
(2006) - et al.
Microbial reduction of hexavalent chromium by landfill leachate
J. Hazard. Mater.
(2007) - et al.
Competitive effect of iron(III) on metal complexation by humic substances: characterisation of ageing processes
Chemosphere
(2007) - et al.
Fractionation of heavy metals in liquefied chromated copper arsenate (CCA)-treated wood sludge using a modified BCR-sequential extraction procedure
Chemosphere
(2009)
Evaluating landfill disposal of chromated copper arsenate (CCA) treated wood and potential effects on groundwater: evidence from Florida
Chemosphere
Sorption of copper, zinc and lead on soil mineral phases
Chemosphere
Comment on “Evaluating landfill disposal of chromated copper arsenate (CCA) treated wood, potential effects on groundwater: Evidence from Florida” by Jennifer K. Saxe, Eric J. Wannamaker, Scott W. Conklin, Todd F. Shupe, Barbara D. Beck [Chemosphere 66 (3) 496–504]
Chemosphere
Implication of chromium speciation on disposal of discarded CCA-treated wood
J. Hazard. Mater.
Al(III) and Fe(III) binding by humic substances in freshwaters, and implications for trace metal speciation
Geochim. Cosmochim. Ac.
Natural attenuation process for remediation of arsenic contaminated soils and groundwater
J. Hazard. Mater.
Enhanced mobilization of arsenic and heavy metals from mine tailings by humic acid
Chemosphere
Adsorption of arsenic onto hydrous ferric oxide: Effects of adsorbate/adsorbent ratios and co-occurring solutes
Colloids Surf. A
Critical evaluation and selection of standard state thermodynamic properties for chromium metal and its aqueous ions, hydrolysis species, oxides, and hydroxides
J. Chem. Eng. Data
Adsorption and surface precipitation of metals on amorphous iron oxyhydroxide
Environ. Sci. Technol.
Effects of strong binding adsorbates on adsorption of trace metals on amorphous iron oxyhydroxide
Cited by (14)
Effect of peat and thiol-modified peat application on mercury (im)mobilization in mercury-polluted paddy soil
2023, Ecotoxicology and Environmental SafetyEffect of soil pH on the transport, fractionation, and oxidation of chromium(III)
2020, Ecotoxicology and Environmental SafetyCitation Excerpt :The vertical distribution of Cr(III) in soils can be strongly localized by transport limitations, and laboratory column experiments of Cr-containing liquid flowing through soil media are commonly designed to simulate Cr transport and retention (Banks et al., 2006; Zhang et al., 2018b). Scholars have extensively investigated factors influencing Cr transport and retention particularly for cases involving soil structure, soil minerals, organic matter, microbial exopolymeric substances, and flow rate (Akhtar et al., 2011; Hu et al., 2010; Jardine et al., 1999; Kantar et al., 2011). However, information about the effect of soil pH on the behavior of Cr(III) transport is lacking.
Enhanced immobilization of arsenic and cadmium in a paddy soil by combined applications of woody peat and Fe(NO<inf>3</inf>)<inf>3</inf>: Possible mechanisms and environmental implications
2019, Science of the Total EnvironmentCitation Excerpt :It can also enhance soil microbial activity and the availability of soil nutrients and thus promote plant growth (Ma et al., 2017). Previous studies (Hu et al., 2010; Lee et al., 2013) indicated that peat can effectively immobilize heavy metal(loid)s and that different mechanisms are involved in the sorption of metals by peat; these mechanisms depend on the type of peat, its preparation and the type of metals and their concentration (Stanislawska-Glubiak et al., 2015). Furthermore, the immobilization of heavy metal(loid)s by peat is affected by the presence of metal oxides and/or hydroxides (de Oliveira et al., 2015).
Occurrence and speciation of polymeric chromium(III), monomeric chromium(III) and chromium(VI) in environmental samples
2016, ChemosphereCitation Excerpt :However, health problems associated with exposure to the metals from CCA-treated wood are still a topic of interest worldwide. This is because the utilization of CCA-treated wood in various fields, including industrial applications, structures in marine environments, and load bearing components of structures in terrestrial environments continues (Hu et al., 2010) and metal release will likely continue for at least several decades due to its long service life for the CCA-treated wood sold for residential and industrial uses prior to 2004 (Khan et al., 2006). In our study on speciation of Cr in the leachates from CCA-treated wood using high performance liquid chromatography-induced coupled plasma mass spectrometry (HPLC-ICPMS), an unknown Cr species counting for a large portion of total Cr (∼39–67%) was observed and found to be neither monomeric Cr(III) nor Cr(VI).
The kinetic stability of colloid-associated plutonium: Settling characteristics and species transformation
2012, ChemosphereCitation Excerpt :The colloid-facilitated transport of Pu has been found to present in groundwater at nuclear sites such as Nevada (Honeyman, 1999; Kersting et al., 1999), and Mayak (Novikov et al., 2006). The enhanced transport of colloidal heavy metals (Citeau et al., 2003; Hu et al., 2008, 2010) and organic pollutants (Means and Wijayaratne, 1982) through the immobile media have been also observed under saturated flow conditions. Pu bound to colloids in the vadose zone, where natural colloids are generated in large concentrations, as a result of frequently infiltration events, possibly transport over significant distances to groundwater.