Influence of a wastewater treatment plant on mercury contamination and sediment characteristics in Vidy Bay (Lake Geneva, Switzerland)

Abstract

Previous direct observations of the sediment surface in Vidy Bay, Lake Geneva (Switzerland), revealed a range of sediment characteristics in terms of colour, texture and morphology. Dives with the MIR submersibles during the éLEMO project permitted the exploration of a large portion of Vidy Bay. It is the most contaminated part of Lake Geneva, due to inputs of treated and untreated waters from a large wastewater treatment plant (WWTP). To evaluate the influence of WWTP effluent on mercury contamination and sediment characteristics, 14 sediment cores were retrieved in the vicinity of the wastewater treatment plant effluent. Total mercury concentrations in sediments ranged between 0.32 and 10.1 mg/kg. Inorganic mercury and monomethylmercury concentrations in overlying and pore waters were also measured. The total partition coefficients of mercury (logK d ) ranged from 3.6 to 5.8. The monomethylmercury concentration in pore waters of surface sediments was a large proportion of the total mercury concentration (44 ± 25 %). A Spearman test showed a negative correlation between the distance to the wastewater treatment plant outlet and the concentrations of total mercury in sediments and pore waters. Visual observations from the submersible allowed recognizing six different types of sediment. The areal distribution of these different sediment types clearly showed the influence of the wastewater treatment plant outlet on the sediment surface patterns. However, no relationship with mercury concentrations could be established.

Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by waste water releases

“…The proportion of MMHg to Hg tot was the highest at 1–2 cm (0.9–1.1 %) and decreased with depth to values between 0.28 % and 0.38 %. These Hg tot values and MMHg percentages are in line with analyses performed previously, but fall within the lower range of Hg concentrations reported for Vidy Bay [ 49 , 50 ]. Pearson's correlation analysis revealed that MMHg concentrations were positively correlated to C org , S tot , Fe II and Hg tot (Figure S3 ).…”

Diversity, Functions and Antibiotic Resistance of Sediment Microbial Communities From Lake Geneva Are Driven by the Spatial Distribution of Anthropogenic Contamination

“…The magnitude of these effects depends on the types and the concentrations of contaminants in the sediments. All contaminant concentrations measured in the present study are in agreement with previous findings ( Haller et al, 2011 ; Gascon Diez et al, 2014 ; Masson and Tercier-Waeber, 2014 ; Gascón Díez et al, 2017 ; Loizeau et al, 2017 ). In addition, our results also revealed high concentrations of PAH (>13.5 μg kg –1 dw) in sediments collected at site 36.…”

“…Sediments in the Vidy Bay near the city of Lausanne were the most contaminated by metals, organic pollutants and organic matter ( Loizeau et al, 2017 ). The high contamination of sediments in this area has been documented for decades ( Grandjean et al, 1990 ; Poté et al, 2008 ; Loizeau et al, 2013 ; Gascon Diez et al, 2014 ; Masson and Tercier-Waeber, 2014 ). This is mainly due to historic inputs from urban sewage effluents ( Gascón Díez et al, 2017 ), which is also reflected by the prevalence of fecal-indicator bacteria ( Poté et al, 2008 ) and antibiotic-resistance genes ( Czekalski et al, 2014 ).…”

Role of Settling Particles on Mercury Methylation in the Oxic Water Column of Freshwater Systems

“…This site has been previously described by Graham, and detailed maps are presented in the Supporting Information (Figure S1). Briefly, NG2 is located at 138 m depth and 1100 m from an outlet pipe discharging in Vidy Bay both treated and untreated sewage water of a wastewater treatment plant (WWTP) located near the city of Lausanne. ,− …”