Effects of heavy metals released from sediment accelerated by artificial sweeteners and humic acid on a green algae Scenedesmus obliquus

Abstract

Artificial sweeteners (ASs) are emerging polar organic contaminants, which can chelate with heavy metals in the environment. Recently, the ASs have been widely detected in the aquatic environment. However, little is known about the influence of ASs on the mobility and toxicity of heavy metals associated in sediment. In the present study, the release of heavy metals from a lake sediment and the toxicity to a green algae Scenedesmus obliquus were examined in the presence of two most frequently detected ASs, acesulfame and sucralose, and humic acid (HA), respectively. The existence of 1.00–100 mg/L of acesulfame, sucralose, and HA enhanced the release rates (Rrelease) of Cd, Cu, and Pb from the virgin lake sediment significantly by up to 46.7%, 86.0%, and 79.9%, respectively. Further, the results from microcosm experiments revealed that the existence of 1.00–10.0 mg/L of acesulfame, sucralose, and HA in the water phase prompted the release and toxicity of heavy metals associated with Cd- and Cu-spiked sediment, and the promotion capacity followed the order of HA > acesulfame > sucralose. The inhibitions on cell-specific growth rate (μ) of the algae were found increasing significantly with the elevated levels of acesulfame and HA (p < 0.05). Additionally, photosynthesis of the algae was affected by the co-existence of ASs or HA and heavy metals released from sediments, as indicated by the changes in fluorescence parameters. The present study provides valuable insight into the likelihood of the combined effect of ASs and heavy metals on aquatic organisms.