Combined Effects of Compost and Medicago Sativa in Recovery a PCB Contaminated Soil

Martina Di Lenola,Paola Grenni,Valeria Ancona,Anna Barra Caracciolo,Giuseppe Mascolo,Vito Armando Laudicina,Gian Luigi Garbini

doi:10.3390/w12030860

Abstract

The effectiveness of adding compost and the plant Medicago sativa in improving the quality of a soil historically contaminated by polychlorinated biphenyls (PCBs) was tested in greenhouse microcosms. Plant pots, containing soil samples from an area contaminated by PCBs, were treated with the compost and the plant, separately or together. Moreover, un-treated and un-planted microcosms were used as controls. At fixed times (1, 133 and 224 days), PCBs were analysed and the structure (cell abundance, phylogenetic characterization) and functioning (cell viability, dehydrogenase activity) of the natural microbial community were also measured. The results showed the effectiveness of the compost and plant in increasing the microbial activity, cell viability, and bacteria/fungi ratio, and in decreasing the amount of higher-chlorinated PCBs. Moreover, a higher number of α-Proteobacteria, one of the main bacterial groups involved in the degradation of PCBs, was found in the compost and plant co-presence.

Highlights

Soil microorganisms provide regulating ecosystem services, playing a central role in ensuring the quality of ecosystems
Soil was gathered from a polychlorinated biphenyls (PCBs) contaminated site, located in Apulia Region (Southern Italy), overlooking the Little Sea of Taranto, where a phytoremediation strategy, applying the Monviso poplar clone (Populus generosa x Populus nigra) as the main detoxifying plant, has been in progress for more than 4 years (Figure 1)
The samples consisted of equal proportions of surface soil (0–20 cm) collected in three points in which PCB contamination was above the legislative limit of 60 ng g−1

Summary

Introduction

Soil microorganisms provide regulating ecosystem services, playing a central role in ensuring the quality of ecosystems. The presence of a rich and diverse microbial community makes it possible to recover soil from contamination [1,2]. Soil remediation is possible if the detrimental effects of chemicals do not kill or inhibit microbial populations [3]. Particular concern arises from polychlorinated biphenyls (PCBs) which are persistent organic pollutants (POPs), as classified in the Stockholm Convention in 2001, and exclusively generated from anthropogenic sources. They have been prohibited since the 1970s, these POPs have been causing continuous exposition of water, air, sediments, soil and living organisms [4]. The most common PCB remediation strategies implemented today are “dig and dump” and “dig and incinerate” [5], but there is a need to apply effective green remediation strategies in line with environmental sustainability guidelines [6]

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Discussion

Conclusion