Confirmation of elemental sulfur toxicity in the Microtox® assay during organic extracts assessment of freshwater sediments

Abstract

Abstract-Recent literature indicates that the elemental sulfur occurring in organic extracts of sediment samples can be toxic to the bacterium Vibrio fischeri, used in standard Microtox bioassays. This observation was tested by means of the solvent extraction of 14 freshwater sediment samples from rivers tributary to Lake Geneva (Switzerland-France), measuring both Microtox toxicity and the elemental sulfur concentration of the extracts. Aliquots of these sediment extracts were further treated to remove the sulfur by adding acid-activated copper to the crude extracts; for 18 h in one case, and for 116 h in an other. The results were a significant amount of the observed acute toxicity in the Microtox assay of 81% of sample extracts (n ϭ 42, crude and after cleanup) was due to elemental sulfur, and despite a median decrease of 99.1% of elemental sulfur in the extracts subject to a 116-h cleanup, sulfur toxicity was not completely excluded for 57% (8/14) of the samples. Clearly, the Microtox methodology needs to be amended to more accurately assess the potential impact of organic pollutants in sediments when solvent extracts are used. This will help to cut down on costly and unnecessary remedial actions.

A new procedure, based on combustion to sulphate and ion chromatography for the analysis of elemental sulphur in sediments

“…The yield from the combustion step, determined by use of a standard solution of S ~ in toluene, was 89 • 6% (n = 3). The precision was comparable with that of GC methods (reported RSD range from <7% [10 12] to 20% [8]). The recovery is lower than that obtained in the spectrophotometric method (100• recovery from sediments spiked with S ~ [2]); it is probably limited by the combustion yield.…”

“…It reacts with sulphides to form polysulphides, which might enhance the solubility of toxic heavy metals [6] and participate in the incorporation of sulphur into sedimentary organic matter [5,7]. S ~ is biologically active, and its presence should be included in bioassays intended to evaluate sediment toxicity [8].…”

Sediment Toxicity of Industrialized Coastal Areas of Korea Using Bioluminescent Marine Bacteria

“…The EC50 values of sediments in this study were comparable to or lower than those in the following regions: Lake Geneva, USA (0.008-3.42 mg/mL) (Pardos et al, 1999), Southern Puget Sound, USA (0.31-175.30 mg/mL) (Long et al, 2002), Waukegan Harbor, USA (0.42-14.50 mg/mL) (Kemble et al, 2000), Ebro River, Spain (0.04-12.96 mg/mL) (Ocampo-Duque et al, 2008), Po River, Italy (0.46-36.80 mg/mL) (Viganò et al, 2003), and Irish marine sediments (>1,000 mg/mL) (Macken et al, 2008). However, our values were much higher than those in Barcelona Harbor, Spain (0.0002-0.0044 mg/mL) (Martínez-Lladó et al, 2007), which is associated with intensive marine and industrial activities.…”

Bioluminescent bacteria: lux genes as environmental biosensors

“…In the last 18 years, the Microtox system has been used by several agencies to assess the impact of chemicals in the environment (8,9). This is a commercially available toxicity bioassay that uses the naturally bioluminescent bacteria, Photobacterium phosphoreum, and more recently, Vibrio fischeri (43). Light emission in P. phosphoreum depends on functional metabolism.…”