Differentiating current and past PCB and PCDD/F sources: The role of a large contaminated soil site in an industrialized city area

Abstract

Cities and contaminated areas can be primary or secondary sources of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and other chemicals, into air and soil and can influence the regional level of some of these pollutants. In a contaminated site, the evaluation of such emissions can be crucial in the choice of the remediation technology to be adopted. In the city of Brescia (Northern Italy), more than 100 ha of agricultural areas were contaminated with PCBs, PCDD/Fs and heavy metals, originating from the activities of a former PCB factory. In order to evaluate the current emissions of PCBs and PCDD/Fs from the contaminated site, in a location where other current sources are present, we compared measured and predicted air concentrations, resulting from chemical volatilization from soils as well as fingerprints of Brescia soils and of soils contaminated by specific sources. The results confirm that the contaminated area is still a current and important secondary source of PCBs to the air, and to a lesser extent of PCDFs (especially the more volatile), but not for PCDDs. PCBs in soils have fingerprints similar to highly chlorinated mixtures, indicating contamination by these mixtures and/or a long weathering process. PCB 209 is also present at important levels. PCDD fingerprints in soil cannot be related to current emission sources, while PCDFs are compatible to industrial and municipal waste incineration, although weathering and/or natural attenuation may have played a role in modifying such soil fingerprints. Finally, we combined chemical and microbiological analyses to provide an integrated approach to evaluate soil fingerprints and their variation in a wider perspective, which accounts for the mutual effects between contamination and soil microbiota, a pivotal hint for addressing in situ bioremediation activities.

Bacteria Associated to Plants Naturally Selected in a Historical PCB Polluted Soil Show Potential to Sustain Natural Attenuation

“…In a previous work (Di Guardo et al, 2017) we suggested that soil pollutant profiles of different former agricultural fields in the SIN Caffaro acted as drivers of the bacterial community composition. Here we demonstrated that in one of the previously analyzed fields, the rhizosphere effect of spontaneous plants adapted to the occurring soil contamination significantly influenced bacterial assemblages in the root-associated soil fraction, R and S. We speculate that in the rhizosphere an enhanced pollutant degradation, according to the higher abundance of taxa previously associated to PCB metabolism, contributed to shape bacterial diversity (Leewis et al, 2016a; Ridl et al, 2016).…”

“…Moreover, a significant fraction of isolates tolerated moderate saline, osmotic and temperature stresses. These phenotypes are not directly related to PGP or biodegradation activity, but could confer to the strains a higher fitness in soils with complex and uneven pollutant fingerprints and subjected to seasonal changes (Di Guardo et al, 2017). …”

“…Non-vegetated and root-associated soil fractions were collected in the SIN Caffaro, a site located in Northern Italy (Brescia municipality), within the sampling area A, a former agricultural grassland field that was previously chemically characterized and contained PCBs and other chlorinated pollutants in concentrations often exceeding the safety limits (Di Guardo et al, 2017). The root system of three spontaneous plant species was collected from triplicate specimens for each plant species.…”

“…This is a large area polluted by the activity of the former Caffaro chemical factory and includes more than 100 ha of former agricultural areas (Di Guardo et al, 2017). It presents a mixed and uneven contamination of chlorinated persistent organic pollutants, mainly PCBs, heavy metals and metalloids and several other contaminants including dioxins, furans, tetra-chloromethane (Turrio-Baldassarri et al, 2007; Di Guardo et al, 2017). PCBs were produced by Caffaro for 46 years and banned in Italy in 1984.…”

Present and future of aquatic sciences: The perspective of AIOL scientific community for a priority roadmap over the next five years

“…Finally, intensive agriculture is responsible for the degradation of the quality of surfaceand groundwater, including contamination from pesticides and nitrates (Di Guardo and Finizio, 2016;Di Guardo et al, 2017).…”