Impact of Different Types of Activated Carbon on the Bioaccessibility of 14C-phenanthrene in Sterile and Non-Sterile Soils

Abstract

In this study, the impact of three different types of activated carbon (AC) on the bioaccessibility of 14 C-phenanthrene in non-sterile and sterile soils was investigated. A single dose (1%) of each of the different AC (CB4, CP1 and AQ5000) was blended with soil spiked with 50 mg•kg −1 of 12 C/ 14 C-phenanthrene. The mineralisation of the 14 C-phenanthrene was monitored over a 14 day incubation period by indigenous soil microflora and an enriched inoculum of Pseudomonas sp., while uptake in earthworms, Eisenia fetida, was measured after incubation for 10 days at 1, 25, 50 and 100 d. Bioaccessibility was assessed using hydroxypropyl-β-cyclodextrin (HPCD) solution. Results showed that the presence of AC had a significant effect upon the extents of mineralisation, earthworm uptake and HPCD extraction, when compared to the control. Aquasorb CB4 was the least effective amongst the different AC used. The characteristics of the different AC used was also seen to have a major influence on how each AC would have an effect on its use in soil remediation in reducing bioaccessibility, mobility and risk.

Impact of activated carbon on the catabolism of 14C-phenanthrene in soil

“…Analysis of the data suggested that there was a relation between the AC type, and its impact on 14 C-phenanthrene mineralisation in soil. 12,23,26 This indicates that the characteristic of coconut shell based carbon, which has a predominance of pores in the micropore-mesopore range, accounts for 95% of the available internal surface area. Values are mean AE standard error (n ¼ 3) CP1-amended soils, respectively.…”

“…2-4; Tables 2-4). 12 An increase in soil-phenanthrene contact time led to a reduction in the rates and extents of 14 C-phenanthrene mineralisation, although it was not signicant in the lower concentrations of AC-amended soils. A comparison CB4, AQ5000 and CP1-amended soils showed that CB4-amended soils generally had the highest extents of 14 Cphenanthrene mineralisation; this was found to be statistically signicant (P < 0.001), when compared to AQ5000-and CP1amended soils (Fig.…”

“…Although the mechanism of sorption was not investigated, the decline in 14 C-phenanthrene mineralisation may be attributed to sorption of AC to phenanthrene, as shown in previous studies. 12,32 The reduction in overall extent of 14 C-phenanthrene, observed with CP1, AQ5000 and CB4, may be attributable to differences in particle sizes instead of pore size. This indicated that the adsorption capacity of CB4 towards 14 C-phenanthrene was lower than that of AQ5000 and CP1, as observed from the values of the SSA for each AC.…”

“…6,7 AC is a manufactured type of BC, produced from coal peat or coconut shells, by incomplete combustion followed by either thermal, chemical or steam activation. 11,12 Oyelami et al 12 reported that the addition of 1% AC to soil reduced uptake of 14 C-phenanthrene in E. fetida over 100 days. 10 The strong interaction between hydrophobic organic contaminants (HOCs) and AC can greatly reduce the mobility, bioaccessibility and environmental risk of HOCs in soils and sediments, thus lowering the actual risk to terrestrial and marine organisms.…”

Optimisation of XAD extraction methodology for the assessment of biodegradation potential of 14C-phenanthrene in soil

“…This measurement can be valuable in predicting biodegradation endpoints in the assessment of contaminated land (Rhodes et al, 2012;Sanchez et al, 2013;Ortega-Calvo et al, 2015;Ogbonnaya et al, 2016). However, prediction of bioaccessibility has been less successful in larger soil organisms, such as earthworms, high molecular weight (HMW) PAHs contaminated soils and soils with relatively high amounts of black carbon (Hickman and Reid, 2005;Barther and Pelletier, 2007;Papadopoulos et al, 2007;Rhodes et al, 2012;Cui et al, 2013;Oyelami et al, 2014). Thus, identifying a supporting technique that can overcome these barriers with similar efficiency would be valuable for the assessment of contaminated land.…”