Sorption to Black Carbon of Organic Compounds with Varying Polarity and Planarity

Abstract

It is becoming increasingly clear that the products of incomplete combustion (soot and charcoal, collectively termed black carbon or BC) can be responsible for as much as 80 - 90% of the total sorption to sediments of aromatic, planar, and hydrophobic compounds such as polycyclic aromatic hydrocarbons or planar polychlorinated biphenyls. In the present study, it was investigated whether a nonpolar aliphatic compound (hexachloroethane) and three nonplanar bipolar compounds with different functional groups [free electron pairs but no aromatic ring (butylate) or free electron pairs and an aromatic ring (diuron, atrazine)] would also show strong and nonlinear sorption to a BC-enriched sediment. At a concentration of 1 ng/L, the extent of elevated BC sorption compared to total organic carbon (TOC) sorption increased in the order atrazine < hexachloroethane < butylate < diuron. Rationalization of the differences between the sorbates was attempted in terms of dispersive and steric effects. This study shows that the effects of strong BC sorption apply to a broader range of organic contaminants than previously thought, and the results will aid in a better understanding of BC sorption mechanisms and improved fate modeling of contaminants in the environment.

Influence of black carbon and chemical planarity on bioavailability of sediment‐associated contaminants

“…It was surprising to find a statistically significant difference in BAFs for the nonplanar HCBP, whereas BC addition showed no effect on C pw . Because of the capability of attaining a planar conformation, some nonplanar compounds such as diuron may strongly sorb to BC as well [12]. However, this could not explain the observed significant effect of BC on HCBP bioavailability.…”

“…In addition to BC characteristics, the planarity of a compound also impacts HOC bioavailability [11,12]. Addition of charcoal significantly reduced bioavailability of the planar compounds TCBP and BaP.…”

“…However, BC may strongly sorb some nonplanar compounds, for example, the pesticide diuron. The dipole interactions between diuron and BC may provide diuron a better ability to attain planar conformation, which enhanced its sorption to the BC [12]. Although several studies have been conducted on the bioavailable potential of HOCs in sediment amended with activated carbon [13][14][15], the influence of naturally originated BC in sediment on the bioavailability of HOCs with differing chemical properties to aquatic species has not been thoroughly studied.…”

Addition of contaminant bioavailability and species susceptibility to a sediment toxicity assessment: Application in an urban stream in China

“…These significant relationships indicated pyrethroids tended to bind to OC, and OC-normalization would reduce the concentration variation among different sediments, while BC was also involved in the sorption process. However, in addition to total OC content, the types of OC should also be taken into consideration for estimating bioavailability of contaminants (Cornelissen et al, 2005;Kukkonen et al, 2005). Fleming et al (1998) reported that different types of OC (peat or a-cellulose) significantly affected permethrin toxicity to Chironomus riparius at a constant OC content.…”

“…Similarly, other studies have shown OC-normalized concentrations may overestimate bioavailability of contaminants (Cornelissen et al, 2005;Reichenberg and Mayer, 2006). One of the reasons for this discrepancy is that contaminants have distinct sorption capacities to different types of OC, but the understanding of OC classification and the partitioning processes of contaminants within OC is still quite limited .…”