Effects of laboratory test conditions on the toxicity of silver to aquatic organisms

Abstract

The effects of various chemical manipulations of test water on acute toxicity of silver to fathead minnows (Pimephales promelas) were investigated. Increases in hardness and organic carbon substantially reduced toxicity. Toxicity was also inversely related to pH and alkalinity when these parameters were jointly changed by addition of strong acid or base. The addition of 2 meq/L sodium sulfate had no significant effects, but the addition of 0.2 meq/L sodium chloride increased toxicity, perhaps related to the formation of the dissolved AgCl0 complex. We also evaluated the effects of static versus flow‐through test conditions, feeding during exposure, and aging of test solutions before exposure on the acute toxicity of silver to fathead minnows and Daphnia magna. Static conditions and feeding reduced toxicity, likely as a result of accretion of organic carbon. Aging of test solutions had little effect. For both juvenile fathead minnows and D. magna, silver was much less toxic in water from the St. Louis River than in our normal laboratory water, presumably because of the much higher organic carbon content of the river water. This study identified some aspects of test conditions that are important in assessing the risk of silver to aquatic biota, but improved assessments will require information for more conditions, species, and endpoints. More importantly, if toxicity test results are to be extrapolated among waters with different chemistries, adequate characterization of the chemical speciation of silver and a better understanding of the mechanisms of silver toxicity and its relationship to silver speciation and other chemical factors are needed.

Toxicity of various silver nanoparticles compared to silver ions in Daphnia magna

“…The 48-hour EC50 for the silver ions (AgNO 3 ) was determined to be 0.0023 mg/L, which matched well with previous literature [32-34]. Although, lower EC50s (0.0003, 0.0007, 0.0009, 0.0011, and 0.0016) have been reported in some other studies using Daphnia [13,16,31,35-37].…”

Transformation of PVP coated silver nanoparticles in a simulated wastewater treatment process and the effect on microbial communities

“…Organic matter complexes Ag + [31,32], which has been linked to AgNP toxicity, whereas high salt concentrations cause NP aggregation which is known to decrease nanoparticle toxicity [33]. In addition, Ag + anion binding may produce very stable products such as AgCl (K sp, H2O, 25°C  = 1.77 x 10 -10 ) and Ag 2 S (K sp, H2O, 25°C  = 5.92 x 10 -51 ) which will also decrease Ag + bioavailability and hence toxicity.…”

A relationship between gill silver accumulation and acute silver toxicity in the freshwater rainbow trout: Support for the acute silver biotic ligand model

“…The 96-h LC50 value based on ionic silver, as calculated by MINEQLϩ [30] [11]) and Galvez and Wood (3 g/L, [9]). Static test conditions have been found to reduce acute silver toxicity [31]. Our study was performed under flow-through conditions while the studies of Bury et al [11] and Galvez and Wood [9] were static tests.…”