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Petroleum hydrocarbons (PHs) are the most widespread organic pollutants of roadside soils, the reclamation of which is costly due to large areas affected, and natural PHs biodegradation is the only way of mitigating negative ecological consequences. This study aimed to investigate the microbial response to PHs in roadside soils and to identify soil organic matter (SOM) and PHs involved in biodegradation processes. To address this aim, soil respiration is related to light (chain‐length ≤C14) medium (C15–C27), and heavy fractions (≥C28) of total PHs, and to SOM components: carbohydrates, proteins, lignin, aliphates, carbonyl/carboxyl, and char amounts of soils sampled at distances of up to 100 m from three roads in Kharkiv, Ukraine. A close relation between soil respiration and ratio of the light fraction to the sum of medium and heavy alkane fractions indicate the preferential mineralization of more biodegradable light PHs fractions. A positive relation between soil respiration and carbohydrate C, as well as negative correlation with aliphatic C, indicate preferred degradation of carbohydrates compared to more recalcitrant aliphates. Carbohydrate content increased and aliphatic C decreased with distance from the roads, and carbohydrates decreased with PHs concentration, indicating increased degradation of carbohydrates at high PHs concentrations (positive priming). It is concluded that microorganisms generate the energy required for PHs degradation by enhanced oxidation of native SOM where carbohydrates were of paramount importance.
Relict charcoal hearths (RCHs) are sites of former charcoal production that are an increasingly well documented anthropogenic feature in forests of the temperate climate zone. However, the type and extent of a possible legacy effect from RCHs on soil physical and chemical properties is still largely unknown. In the Litchfield Hills in west Connecticut, RCH sites are located mainly on slopes and therefore differ in their architecture from lowland sites found in Europe. One of the striking characteristics of a RCH site regardless of its architecture is the enrichment of the soil with charcoal in varying particle sizes. In this study, we use chemical digestion coupled with a PLSR-model to quantify organic carbon and pyrogenic carbon in RCH substrate by MIR-DRIFT measurements. Furthermore, we analyse the quality of carbon compounds by MIR-DRIFT measurements on multiple grain size fractions to assess the post-burn enrichment of soil organic matter. Preliminary results show a markedly increase in organic and pyrogenic carbon in RCH substrates in relation to the natural forest soil. Also, our first results suggest that the enrichment of organic carbon is favoured on RCHsites. However, the causality between the enrichment of soil organic matter and site features remains open. Experiments using chemical extraction techniques on our samples hint at an increase of labile organic compounds and/or microbial biomass. This legacy effect of RCHs is however evident and further studies need to focus on how to address them.
Kinetic Characteristics of Petrochemicals Transposition and Accumulation in Soils of Roadside Area
(2013)
Total petroleum hydrocarbon (TPH) deposition rates were determined along various roads using the natural snow cover as deposition trap. Daily deposition rates decreased with distance from the roads, which coincided with long-term TPH accumulation in roadside soils. Scanning electron microscopy (SEM-EDX) of the snow meltwater sediment revealed occurrence of carbon-rich plaques, which were identified as hydrocarbons using FTIR-microscopy. GC-MS revealed that the compounds extracted from the sediment consisted of an unresolved complex hydrocarbon mixture (UCM). Individual n-alkanes could not be resolved in the sediment extract, whereas TPHs extracted from soils contained a series of n-alkanes peaking at C25-C27. The proportion of UCM compounds from TPHs decreased with distance from road. We conclude that high-boiling hydrocarbons bind to coarse mineral dust and/or to splash water and vehicle spray, which preferentially deposit within a 10 m roadside strip.