Relations between Environmental Black Carbon Sorption and Geochemical Sorbent Characteristics

Abstract

Pyrogenic carbon particles in sediments (soot and charcoal, collectively termed "black carbon" or BC) appear to be efficient sorbents of many hydrophobic organic compounds, so they may play an important role in the fate and toxicity of these substances. To properly model toxicant sorption behavior, it is important to (i) quantify the magnitude of the role of BC in sorption and (ii) elucidate which geochemical BC characteristics determine the strength of environmental BC sorption. Sorption isotherms of d10-phenanthrene (d10-PHE) were determined over a wide concentration range (0.0003-20 microg/L), for five sediments with widely varying characteristics. From the sorption isotherms, we determined Freundlich coefficients of environmental BC sorption, K(F,BCenv. These varied from 10(4.7) to 10(5.5). From the data, it could be deduced that BC was responsible for 49-85% of the total d10-PHE sorption at a concentration of 1 ng/L. At higher concentrations, the importance of BC for the sorption process diminished to <20% at 1 microg/L and 0-1% at 1 mg/L. There were no significant relationships between BC sorption strength and the tested geochemical BC characteristics [the fraction of small (<38 microm) BC particles, the BC resistance to high-temperature oxidation, the fraction of biomass-derived BC, the native polycyclic aromatic hydrocarbon and total organic carbon contents]. Because of the limited variation in BC sorption strength with widely varying BC characteristics, the presented BC sorption coefficients may putatively be used as generic starting points for environmental modeling purposes.

Impact of Biochar on Organic Contaminants in Soil: A Tool for Mitigating Risk?

“…Sorption is referred to as absorption when it penetrates the three-dimensional structure of the matrix, and adsorption when attached to the two-dimensional surface [30]. Linear absorption (partitioning) of HOCs into natural organic matter underestimates the total extent of sorption, but with the addition of non-linear adsorption of HOCs into black carbon nanopore sites, total sorption of HOCs can be deduced [31][32][33]. These studies [31][32][33] utilised the non-linear Freundlich model to best illustrate this phenomena, where the interaction between HOCs and black carbon materials depends on dispersive interactions and separation distance [11].…”

“…Linear absorption (partitioning) of HOCs into natural organic matter underestimates the total extent of sorption, but with the addition of non-linear adsorption of HOCs into black carbon nanopore sites, total sorption of HOCs can be deduced [31][32][33]. These studies [31][32][33] utilised the non-linear Freundlich model to best illustrate this phenomena, where the interaction between HOCs and black carbon materials depends on dispersive interactions and separation distance [11]. The sorption of HOCs within the soil matrix is thought to be by partitioning or entrapment within the internal matrix of the SOM [34][35][36].…”

Polyethylene passive samplers to determine sediment–pore water distribution coefficients of persistent organic pollutants in five heavily contaminated dredged sediments

“…Indeed, sorption to BC, such as diesel soot, coal soot, wood charcoal, or char-like carbonaceous particles, renders obsolete the traditional equilibrium partitioning theory (EPT) model assuming linear partitioning to amorphous organic matter (Bucheli and Gustafsson, 2000;Huang et al, 2003;Cornelissen et al, 2004;Cornelissen et al, 2005). Furthermore, a very high sorption capacity, similar or even higher than that of BC, has been previously reported for weathered mineral oil residues for polycyclic aromatic hydrocarbons (PAHs) (Jonker et al, 2003;Brändli et al, 2008) and polychlorinated biphenyls (PCBs) (Cornelissen et al, 2005;McNamara et al, 2005;Jonker and Barendregt, 2006).…”

Extraction of sediment‐associated polycyclic aromatic hydrocarbons with granular activated carbon

“…Consequently, the majority of AC amendment studies use powdered AC (PAC) or fine granular AC (GAC) having particle diameters within the range of 75 to 300 mm. Small particles have cumulatively large external surface area and, therefore, large accessible numbers of sorption sites per unit of weight [9]. Recently, risk reduction of sediment-bound HOCs in pilot field studies has been accomplished through addition of AC to the sediment biologically active layer (upper 30 cm) using commercial mixing units, by capping with a thin layer of AC or by mixing AC in a layer of clay [3,4,10,11].…”