Impact of nano- and micro-particulate black carbon on organic contaminant bioaccessibility in soil

• Main Author: Oyelami, Ayodeji Oluwaseun
• Published: Lancaster University 2013
• Subjects: 631.4
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663215

This thesis investigated the impacts of different forms of black carbon (BC) on the bioavailability and bioaccessibility of phenanthrene in soil for remediation. BC is a general term used to describe various forms of natural and engineered carbonaceous geosorbents, such as activated carbon (AC), biochar and soot. Carbon nanomaterials (CNMs) are generally agreed to be engineered structures with at least one dimension of less than 100 nanometres in length. CNMs are of interest because of their specific physicochemical properties that can be attributed to their small size, chemical composition, surface structure, solubility, shape and aggregation. CNMs could be released into water and soil not only by inadvertent discharge, but also because NPs have applications for groundwater purification and pollutant remediation. Unfortunately, very little is known about the transport of these materials in soil or the resulting ecotoxicity, and only a small number of studies have been carried out in this area. Phenanthrene, a ubiquitous, persistent and hydrophobic contaminant found in all ecosystems worldwide, was used as the target contaminant for the studies carried out in this thesis. Powdered activated carbons (PACs) with different pore volumes and particle size distributions were amended to soil, and used to assess bioaccessibility of phenanthrene to soil. Biochar from the same feedstock was also used, but prepared under different conditions. At low concentrations (0.01 %), the addition of AC to soil did not affect microbial activity, measured by the rates of respiration and overall extents of mineralisation of 14C-phenanthrene. However, the presence of AC at 0.1 and 1 %, respectively, resulted in significant reductions (P < 0.05) in the bioavailability and bioaccessibility of 14C_ phenanthrene. For CNM-amended soils, the addition of>0.01% (w/w) significantly reduced the development of phenanthrene catabolism; the only exception to this was C60, which did not show any significant difference from the control, at all concentrations. Results from this thesis suggest that soils amended with AC provide a potential strategy for in situ environmental remediation, and appropriate selection of adsorbents is a key to realising this remediation potential. The different kinds of BC described in this thesis provide a wide choice; therefore it is reasonable to regard them as a promising amendment technology.