Strong Sorption of Native PAHs to Pyrogenic and Unburned Carbonaceous Geosorbents in Sediments

Abstract

It has recently been shown that the presence of carbonaceous geosorbents (CG, including black carbon (BC), unburned coal, and kerogen) can cause strong sorption of polycyclic aromatic hydrocarbons (PAHs) in sediments. We studied sorption of native PAHs in four Norwegian harbor sediments of which high fractions (21-56%) of the total organic carbon (TOC) consisted of CG carbon (CGC), as shown by organic petrography. PAH sorption coefficients were 1-2 orders of magnitude above predictions based on amorphous organic carbon partitioning alone. In recent studies, such strong sorption was attributed solely to BC sorption under the implicit assumption that sorption is linear for coal and kerogen. The most important result of the present study is that total sorption is better explained by considering all three nonlinearly sorbing CGC materials than by only considering BC. In addition, it was evaluated whether activated carbon (AC) amendments could be effective in reducing the freely dissolved pore-water concentrations (CW) and thus the environmental risks of the PAHs in such strongly sorbing sediments. The results indicated that an addition of 2 weight % AC reduced the Cw by factors of 21-153 for the four sediments (average values for all PAHs). Itwas shown that phenanthrene sorption to AC was, on average, reduced by a factor of 6 in sediment-AC mixtures compared to pure AC.

Partitioning and sources of PAHs in wastewater receiving streams of Tianjin, China

“…Also, most of logK oc,obs between sediment and PW in the three streams were also higher than the predicted partition coefficients. This could be explained by the strong and nonlinear sorption of PAHs by carbonaceous geosorbents including BC in the sediment (Mcgroddy and Farrington 1995;Bucheli and Gustafsson 2000;Lohmann et al 2005;Cornelissen et al 2005Cornelissen et al , 2006. In addition, the rather slow release of PAHs after an initial rapid release from sediments collected from Yongding New River, South Drainage Canal, and North Drainage Canal PAHs which we reported previously in the desorption experiment (Qi et al 2010b) also proved this strong sorption of PAHs by carbonaceous particles in the sediment.…”

Aging effects on sorption–desorption behaviors of PAHs in different natural organic matters

“…These phenomena may mainly due to the source and structural difference between DHS and humins. As usually classified, HA and FA are typed into amorphous humic substances which are loosely packed, while humins pose rigid geosorbent characteristics [15]. And this may reflect that the use of only macroscopic properties is unlikely to underlie the sorptive character of a geosorbent.…”

“…However, most attention focused on the sorption by DHS in single-step uptake experiments while little has been paid to the reversibility of sorption by including desorption steps. Consequently, the enhanced retention was usually neglected when processing binding data of HOC-DHS interactions according to the partitioning concept and application of this inaccurate view can greatly affect attempts to model the transport and fate of organic pollutants in natural systems [15]. Since little experiment has been conducted on the influence of aging on chemicals bound with DHS, it is necessary to provide an improved understanding of the relationship between chemical retardation in NOMs and aging time.…”

Occurrence, distribution, sources and toxic potential of polycyclic aromatic hydrocarbons (PAHs) in surface soils from the Kumasi Metropolis, Ghana

“…Many PAHs are mutagenic and some are carcinogenic and these raise concerns over their occurrence in the environment (Flowers et al, 2002;Thorsen et al, 2004;Cornelissen et al, 2006). Due to their high hydrophobic properties, PAHs can be sorbed on atmospheric particles and thus transported over a long distance, being a source of diffuse pollution (Wilcke, 2007;Ravindra et al, 2008).…”