Influence of origin and properties of dissolved organic matter on the partition of polycyclic aromatic hydrocarbons (PAHs)

Abstract

We investigated dissolved organic matter (DOM) from soil, sewage sludges, water from waste disposal sites, and composts as sorbents and potential carriers for hydrophobic polycyclic aromatic hydrocarbons (PAHs) in soil. Partition coefficients (expressed log K-)for two 5-ring compounds were 4.8-4.9 for DOM from soil, 4.547 from composts, and 4.34.4 from sewage sludges. The DOM from compost and sewage sludge can influence the transport of non-ionic organic contaminants because of the large concentrations of dissolved organic carbon (DOC) released from these materials. Leachates from waste disposal sites did not sorb PAHs. The DOM from compost contained a large percentage of organic molecules >14 OOO Da (32-46%), whereas DOM from waste disposal leachates contained only 7-lo%, and so bound less PAHs. The percentage of total hydrophobic components, as characterized by XAD-8 chromatography, was 50 2 9% for most of the DOM solutions and did not express the differences in affinity of the organic sorbents to PAHs in the same way as the K D~ values. Isolated molecular-weight fractions of DOM from composts sorbed benzo(k)fluoranthene in each fraction. The log KDOC values were 4.14.3 for both fractions, <lo00 and 1000-14 OOO Da, and 4.8-5.0 for the fraction >14 000 Da.The interaction of PAHs with DOM < 1OOO Da cannot be explained by partitioning within intramolecular nonpolar environments of dissolved macromolecules; rather it seems to be due to the amphoteric properties of DOM. This type of interaction of PAHs with small DOM molecules might affect the mobility of hydrophobic organic chemicals in soils.

Pesticide desorption from soils facilitated by dissolved organic matter coming from composts: experimental data and modelling approach

“…However, these methods, as equilibrium dialysis, fluorescence quenching or solubility enhancement, work well for compounds with low water solubility allowing high extent of interactions with DOM in solution. Hence, some values of interaction constants between some chemicals and DOM from compost are available, all larger than 30,000 l kg -1 C (Raber and Kogel-Knabner 1997), contrasting with the values found in this work with more hydrophilic pesticides. The low values of constants estimated in this work are in correspondence with some published data showing that for low hydrophobic pesticides, sorption is mainly governed by soil organic matter as a solid phase.…”

New Insights into the Influence of Heavy Metals on Phenanthrene Sorption in Soils

“…It is proposed that OC in soils is envisaged as comprising rubbery (including flexible DOC and humic acids) and glassy (for example, humin) phases, both of which contain sorption domains according to a well accepted dual reactive domain model (1-3), among which DOC can bind phenanthrene through hydrophobic interactions and inhibit the accumulation of phenanthrene on solid surfaces (23)(24)(25)(26)(27). In fact, DOC is also a highly heterogeneous mixture of compounds varying in size, shape, composition, and physicochemical properties (14,21,24) although the exact structure of DOC still remains unclear. In the presence of metal cations, both aliphatic and aromatic moieties of DOC were significantly flocculated from the soil solution as evidenced by the changes in DOC contents and NMR spectra.…”

Influence of temperature and origin of dissolved organic matter on the partitioning behavior of polycyclic aromatic hydrocarbons

“…The presence of dissolved organic matter (DOM) in pore water of soils and sediments significantly affects the partitioning behavior of PAHs (Lüers and Ten Hulscher 1996, Raber andKögel-Knabner 1997, Krop et al 2001). This results in decreased bioavailability and bioconcentration of dissolved PAHs due to the presence of DOM in freshwater ecosystems (Akkanen and Kukkonen 2003), whereas enhanced bioconcentration has also been observed at low DOM concentrations (Haitzer et al 1998).…”