Application of an in-situ soil sampler for assessing subsurface biogeochemical dynamics in a diesel-contaminated coastal site during soil flushing operations. (15th January 2018)

• Record Type: Journal Article
• Authors: Kwon, Man Jae; O'Loughlin, Edward J.; Ham, Baknoon; Hwang, Yunho; Shim, Moojoon; Lee, Soonjae
• Is Part Of: Journal of environmental management. Volume 206(2018)
• Page Start: 938
• Page End: 948
• Publication Date: 2018-01-15
• Subjects: In-situ sampler -- Diesel contamination -- Seawater intrusion -- Soil flushing -- Microbial community dynamics; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2017.11.053
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Subsurface biogeochemistry and contaminant dynamics during the remediation of diesel-contamination by in-situ soil flushing were investigated at a site located in a coastal region. An in-situ sampler containing diesel-contaminated soils separated into two size fractions (<0.063- and <2-mm) was utilized in two monitoring wells: DH1 (located close to the injection and extraction wells for in-situ soil flushing) and DH2 (located beyond sheet piles placed to block the transport of leaked diesel). Total petroleum hydrocarbon (TPH) concentrations and biogeochemical properties were monitored both in soil and groundwater for six months. A shift occurred in the groundwater type from Ca-HCO3 to Na-Cl due to seawater intrusion during intense pumping, while the concentrations of Ni, Cu, Co, V, Cr, and Se increased substantially following surfactant (TWEEN 80) injection. The in-situ sampler with fine particles was more sensitive to variations in conditions during the remedial soil flushing process. In both wells, soil TPH concentrations in the <0.063-mm fraction were much higher than those in the <2-mm fraction. Increases in soil TPH in DH1 were consistent with the expected outcomes following well pumping and surfactant injection used to enhance TPH extraction. However, the number of diesel-degrading microorganisms decreased after surfactant injection. 16S-rRNA gene-based analysis also showed that the community composition and diversity depended on both particle size and diesel contamination. The multidisciplinary approach to the contaminated site assessments showed that soil flushing with surfactant enhanced diesel extraction, but negatively impacted in-situ diesel biodegradation as well as groundwater quality. The results also suggest that the in-situ sampler can be an effective monitoring tool for subsurface biogeochemistry as well as contaminant dynamics. Graphical abstract: Image 1 Highlights: In-situ samplers well reflected biogeochemical dynamics during in-situ soil flushing. In-situ samplers with fine particles showed contaminant dynamics much sensitively. Soil particle sizes and TPH concentrations impact community diversity and composition. Soil-flushing negatively impacted diesel biodegradation as well as groundwater quality.