Helichrysum microphyllum subsp. tyrrhenicum, Its Root-Associated Microorganisms, and Wood Chips Represent an Integrated Green Technology for the Remediation of Petroleum Hydrocarbon-Contaminated Soils

Abstract

Phytoremediation and the use of suitable amendments are well-known technologies for the mitigation of petroleum hydrocarbon (PHC) contaminations in terrestrial ecosystems. Our study is aimed at combining these two approaches to maximize their favorable effects. To this purpose, Helichrysum microphyllum subsp. tyrrhenicum, a Mediterranean shrub growing on sandy and semiarid soils, was selected. The weathered PHC-polluted matrix (3.3 ± 0.8 g kg−1 dry weight) from a disused industrial site was employed as the cultivation substrate with (WCAM) or without (UNAM) the addition and mixing of wood chips. Under the greenhouse conditions, the species showed a survival rate higher than 90% in the UNAM while the amendment administration restored the totality of the plant survival. At the end of the greenhouse test (nine months), the treatment with the wood chips significantly increased the moisture, dehydrogenase activity and abundance of the microbial populations of the PHC degraders in the substrate. Cogently, the residual amount of PHCs was significantly lower in the UNAM (3–92% of the initial quantity) than in the WCAM (3–14% of the initial quantity). Moreover, the crown diameter was significantly higher in the WCAM plants. Overall, the results establish the combined technology as a novel approach for landscaping and the bioremediation of sites chronically injured by PHC-weathered contaminations.

Using Mediterranean Native Plants for the Phytoremediation of Mining Sites: An Overview of the Past and Present, and Perspectives for the Future

“…Furthermore, compost improves the texture of the substrate, water retention, and ventilation [17]. Other organic amendments can be promoted, like woodchips, biochar, winery waste, and mushroom residues, giving a second life to organic fractions of municipal solid waste and special waste [21][22][23][24][25].…”

“…Basic research towards the description and definition of further metallophytes has been more recently complemented by the individuation of technologies to assist and boost phytoremediation, such as the development of substrate amendments or modifiers. In particular, attention has been oriented to the use of innovative amendments, often deriving from the re-use of other waste materials (i.e., waste from agricultural production, wood chips, biochar, and mushroom residues) [20][21][22][23][24][25]. The combination of modifiers is another branch of study showing promising results [20,26,27].…”