Integrated phytomanagement of a carbon tetrachloride-contaminated site in Murdock, Nebraska (USA)

Abstract

The application of a large-scale ( ca . 59,000 m 2 ) integrated phytomanagement system at a carbon tetrachloride (CCl 4 )-impacted site at Murdock, Nebraska, USA, was assessed in terms of its effectiveness in mitigating site risk, and realizing wider social and environmental benefits. Volatile Organic Compound (VOCs) concentrations (including CCl 4 ) measured in surface water, groundwater, air and vegetation samples show that the Murdock system has achieved effective risk management over the 10+ year period since its implementation, with the phytomanagement component of the remediation system (consisting of a mixed stand of dominantly Niobe willow ( Salix x ‘Niobe’ ) and Eastern Cottonwood ( Populus deltoides )) removing 300g–600g of CCl 4 annually. Eastern Cottonwood played an increasing role in CCl 4 removal over time, from 55% of the total mass removal in 2008 to 69% in 2014. Using a site design focused on enhancement of the social and physical environment, in addition to risk mitigation, has enabled realization of a range of wider social and environmental benefits, which include carbon sequestration of ca. 77 tons CO 2 /ha/y, and educational and recreational benefits. The phytomanagement system applied at Murdock has incurred significant installation, and on-going monitoring and maintenance, effort and costs (exceeding $1.5 million) highlighting the importance of (a) sustained stakeholder engagement to ensure continued local community support, and (b) effective site design to realize as full a range of core (i.e. risk mitigation) and wider benefits as possible, to increase the overall value proposition of such schemes. • Large-scale phytomanagement was successfully applied at a CCl 4 -impacted site. • Effective risk management has been achieved over the 10+ years since implementation. • Ca. 300g–600g CCl 4 has been removed annually via plant uptake and translocation. • Effective design can realize significant socio-economic and environmental benefit.