Mutual relations between PAHs derived from atmospheric deposition, enzymatic activity, and humic substances in soils of differently urbanized areas

Elżbieta J. Bielińska,Barbara Futa,Lilla Mielnik,Szymon Chmielewski,Agnieszka Mocek-Płóciniak,Sylwia Wesołowska,Aleksandra Ukalska-Jaruga,Krzysztof Patkowski,Jerzy Weber

doi:10.1007/s11368-018-1937-z

Abstract

PurposeThe aim of this study was to determine the mutual relations between polycyclic aromatic hydrocarbons (PAHs) originated from atmospheric emissions and enzymatic activity and humic substances in soils at differently urbanized area, on an example of the Lublin city, east Poland.Materials and methodsThe chosen areas represented three differently urbanized environments: old tenement houses and modern residential blocks, mixture of different building and rural landscape, and typical rural environment with smallholding farms, respectively. On each of the urban, suburban, and rural areas, one representative plot was chosen on fallow lands classified as luvisol derived from loess. The soil samples were collected from the top 25 cm layer. The following properties were determined: pH, organic carbon, total nitrogen, humic and fulvic acids, PAHs content (14 PAHs from US EPA list), and the activities of the following enzymes: dehydrogenases, acid phosphatase, alkane phosphatase, protease, and urease.Results and discussionHigher contents of organic C and total N were found in the rural soil samples. The share of humic acid was similar in all soils investigated, ranging from 19.38 to 25.27%, while fulvic acid values differ significantly between urban and rural areas. The urban soils indicated much lower share of fulvic acids (9.78–10.99%) than those of rural (29.02–29.32%). Consequently, the values of the CHA:CFA ratio of the urban soil were approximately two times higher than those of the rural soil. The results showed that both the rate of humification and the activity of dehydrogenases, acid phosphatase, alkaline phosphatase, and proteases in the soils increased in the following sequence: urban < suburban < rural.ConclusionsThe results showed that an increase of PAHs in the urbanized areas affect other soil properties. The phenanthrene/anthracene and fluoranthene/pyrene ratios pointed to coal combustion as the principal source of PAHs in the investigated soils. The PAH content in the urbanized area inhibit humification processes in the soil and the activity of dehydrogenases, acid phosphatase, alkaline phosphatase, and proteases.

Highlights

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants
Results obtained in the vicinity of Czechowice-Dziedzice refinery in Poland, where the total polycyclic aromatic hydrocarbons (PAHs) content was over 25,000 μg kg−1, showed a very low dehydrogenase activity, at the range of 0.32–0.46 mg TPF kg−1 day−1 (MałachowskaJutsz and Miksch 2000)
Anthropogenic factor in the urbanized areas contributes to an increase of polycyclic aromatic hydrocarbons (PAHs) and affect other soil properties

Summary

Introduction

PAHs are organic environmental contaminants formed during incomplete combustion of fossil fuels such as coal, oil, and natural gas (Galarneau 2008; Ravindra et al 2008; Mostert et al 2010). They represent a large group of organic compounds with two or more fused aromatic (benzene) rings. Atmospheric PAHs are continuously deposited to the soil by dry or wet deposition processes. PAHs can be added to soils with materials containing these compounds (composts, biochar, spills from agricultural machinery) (Galarneau 2008; Mostert et al 2010)

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