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Abstract

A study was conducted to determine the location and distribution of PAH and PAH-degrading bacteria in different aggregate size fractions of an industrially polluted soil. The estimation of PAH-degrading bacteria using an MPN microplate technique indicated that these bacteria are most numerous in the aggregate size fractions corresponding to fine silt (2-20 microm) and clay (<2 microm) compared to larger fractions or unfractionated soil. PAH concentrations were also highest in the aggregate size fraction corresponding to fine silt. Similar results were found in a spiked soil (incubated for 6 months) with similar carbonated minerals. Transmission electron microscopy observations showed that the autochtonous PAH-degrading bacteria were embedded in the aggregates where PAHs were abundant. In spite of this extensive co-localisation PAH degradation was limited during 6 months incubation. This indicates that factors other than spatial distribution and PAH degrading ability control degradation rates. The fine silt fraction of the industrial soil had an elevated C/N ratio (35) compared to the clay fraction (C/N: 16). Thus the fraction which assumably had the highest specific surface area contained less PAH but similar numbers of PAH-degraders. N thus seem to play an important role in the long term, but as PAH degradation was low in fine size fractions, other sources/factors were probably limiting (easily degradable C, P org, O2 etc.). Based on these findings, soil particle organization and structure of soil aggregates appear to be important for the characterization of a polluted soil (localization and sequestration). Manipulations that modify aggregation in polluted soils could thus potentially influence the accessibility and biodegradability of PAHs.

Adsorption of phenolic compounds on low-cost adsorbents: A review

“…Recent literature on the methods of removal of phenol and their compounds from wastewater focuses on adsorption and microbial biodegradation process [61][62][63][64]. Certain species like Pseudomonas sp.…”

Soil Mineral Composition Matters: Response of Microbial Communities to Phenanthrene and Plant Litter Addition in Long-Term Matured Artificial Soils

“…Furthermore, Vogel et al [25] reported previously that QM and QMC soils incubated over a long-term period contained more aggregates than soils with illite. It is known that the biodegradation of PAHs is restricted in aggregates [2], [47], [48], [49]. Montmorillonite is an expandable clay mineral with a high specific surface area which makes possible that phenanthrene was separated from bacterial cells by surface sorption or entrapment in small pores [10], [50].…”

“…Different parameters can severely affect the efficiency of the methods, as for instance the exposure time of the contaminant in soil [1], soil structure [2], pH [3], temperature [3], sorptive interfaces [4], and the organic carbon content [5]. In addition, the accessibility to oxygen may be of importance, since the fastest and most often used microbial pathway of PAH degradation involves the oxidation of the ring-structure via dioxygenases [6].…”

“…[2], [5], [9], [10], [11], we lack a comprehensive understanding of these abiotic soil interaction processes. On the other hand, there is restricted knowledge of the interaction of pollutants with native soil microbial communities within the natural soil system.…”

Biodegradation of pyrene in sand, silt and clay fractions of sediment

“…Recognizing sediment as an assembly of different sizes of particles, a handful of researchers investigated the availability of PAHs also at the particle size scale. For instance, in suspensions, bacteria density was found to be lower on sand particles than on silt or clay particles, leading to a lower biodegradation rate of PAHs on sand (Amellal et al 2001; Xia and Wang 2008). Talley et al (2002), by separating a dredged sediment into coal-derived fraction and clay/silt fraction, showed that desorption and bioavailability of PAHs were more related to properties such as BC content of specific size fractions, rather than the size scale itself.…”