Investigation on soil contamination at recently inundated and non-inundated sites

摘要

Purpose This study was carried out to determine hazards of particle-bound contaminants in rivers to retention areas close to public well fields in the context of flood events. The focus was on the assessment of soil contamination at a planned retention area. Soil core samples were chemically and biologically analyzed. Samples were fractionated to identify and compare contaminant loads and biological effects of soil and flood suspended particulate matter (SPM). Material and methods Soil cores were sampled at inundated and non-inundated sites at a planned retention area. Soil was analyzed for hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs) as well as for polycyclic aromatic hydrocarbons (PAHs). The highest inducing soil sample was fractionated applying a recently developed automated fractionation method to receive further insight into contaminant loads in soil at inundated sites. Impacts on biological scale were assessed using in vitro biotests for xenometabolic activity (7-ethoxyresorufin-o-deethylase (EROD) assay) as well as for mutagenic activity (Ames fluctuation assay). EROD induction was calculated as biological equivalent concentration (bio-TEQ), and mutagenic potentials were given as no observed effect concentration (NOEC) and maximum induction factor (IF_(max)). Results and discussion Soil core samples of each site induced EROD activity. However, extracts of soil sampled at a ground swale was by far the highest inducing (topsoil bio-TEQ= 41,000 pg/g). Further, chemical analysis yielded relative increases in concentration in particular: HCB (0.05 mg/kg), PCBs (0.19 mg/kg), and EPA-PAHs (39 mg/kg). Extracts of soil samples caused no mutagenic effects. PAHs caused the bulk of EROD activity (bio-TEQ= 32,000 pg/g) with ground swale topsoil fractions. Further, fractions containing moderately polar and polar substances gave elevated effects (bio-TEQ=8,200 pg/g). Mutagenic potentials were shown with most fractions. However, highest induction was observed with fractions containing moderately polar to polar substances reflected by a NOEC >0.03 mg/ml and an IF_(max) <29. Conclusions Soil contamination at floodplains is heterogeneous but may reach elevated levels with soil swales giving highest chemical concentrations and biological effects with total sample extracts and fractions. The origin of floodplain soil contamination can be evaluated using lines of evidence which may result in identification of contaminant transport path from sediment, via flood SPM to soil. Taking hazard assessment of floodplain soil forward to risk evaluation may indicate a concern which highlights the need to further investigate on hazards caused by eroded sediment in flood events to avoid conflicts of interest when planning and operating retention basins.