PCB removal, soil enzyme activities, and microbial community structures during the phytoremediation by alfalfa in field soils

Abstract

Purpose An in situ phytoremediation trial was developed in order to investigate the function of alfalfa during a 2-year bioremediation of an agricultural soil contaminated with polychlorinated biphenyls (PCBs). The study was conducted with the aim to better understand the application potential of PCB phytoremediation at field scale. Materials and methods Two treatments were set up in this field study: (1) soil without planting as a control (CK), and (2) soil planted with alfalfa (P). Kinetics of soil PCB removal during the bioremediation treatment was determined using gas chromatography. Soil enzyme activities including dehydrogenase and fluorescein diacetate (FDA) esterase were detected by spectrophotometry. In addition, soil microbial community structures were investigated by using denaturing gradient gel electrophoresis (DGGE). Results and discussion After the first and second years of remediation, planting alfalfa significantly decreased the initial soil PCB concentrations by 31.4% and 78.4%, respectively. Moreover, the presence of alfalfa significantly increased soil dehydrogenase and FDA esterase activities during the remediation. Changes in soil bacterial community structure and diversity were observed by PCR-DGGE fingerprinting. Planting alfalfa significantly increased soil bacterial diversity. Some well-known PCB-degrading bacteria such as Chloroflexi sp. may have contributed to the rhizoremediation of PCBs.Conclusions Results of this field study suggest that alfalfa is a promising candidate for phytoremediation of PCBcontaminated agricultural soil.

Sludge Biochar Amendment and Alfalfa Revegetation Improve Soil Physicochemical Properties and Increase Diversity of Soil Microbes in Soils from a Rare Earth Element Mining Wasteland

“…Our results suggested that alfalfa revegetation could enhance soil microbial community diversity and richness of IAC mining wastelands, which are similar to the results of Chen [ 92 ]. Alfalfa revegetation significantly improved soil physicochemical properties, including enhancement of soil porosity, water-holding capacity and content of organic matter and nutrients (e.g., N, P, and K), decrease of soil bulk density, and amelioration of soil structure, all of which were helpful to the proliferation of soil microorganisms (bacteria and fungi).…”

Bacterial Communities in Riparian Sediments: A Large-Scale Longitudinal Distribution Pattern and Response to Dam Construction

“…Microbial respiration rate was evaluated by the CO 2 released per unit of time from microorganisms following the methods previously described ( Hu et al, 2012 ). Dehydrogenase activity was determined by reduction of 2,3,5-triphenyl tetrazolium chloride to 1,3,5-triphenyl formazan (TPF) according to Tu et al (2011) .…”

Remediation of Polychlorinated Biphenyls (PCBs) in Contaminated Soils and Sediment: State of Knowledge and Perspectives

“…Plant species used for PCB phytoremediation including Medicago sativa (alfalfa), Lespedeza cuneate (Chinese bushclover), Lathyrus sylvestris (everlasting pea), Phalaris arundinacea (reed canary grass), Cucurbitaceae (cucurbits), Sparganium (bur-reed), Salix alaxensis (Alaska willow), and Picea glauca (white spruce) as well as 27 different weeds (Chekol et al, 2004;Ficko et al, 2010;Slater et al, 2011). Tu et al (2011) showed a decrease in PCB soil concentrations by 31.4 and 78.4% after the first and second years of field scale phytoremediation by M. sativa via situ phytoremediation. Sparganium has been shown to promote the oxidation of the low-chlorinated PCBs via rhizodegradation, while panicum virgatum (switchgrass) and other popularly used plants have shown degradation of a high and low congener mix (Meggo et al, 2013).…”