Abstract
Increased production of carbon nanotubes (CNTs) and their widespread application in industrial and consumer products have led to a rise in the release of CNTs into the aquatic environment. CNTs have a very strong adsorption affinity for various environmental contaminants; therefore, they may also influence the toxic effects of other pollutants, such as toxic metals. In this study, the effect of two different functionalized carbon nanotubes, carboxylate and polyethyleneimine modified multi-walled carbon nanotubes (C-MWCNTs and N-MWCNT, respectively) on lead toxicity and bioaccumulation was investigated with a freshwater zooplankton Daphnia magna. The acute toxicity results indicate that the different surface properties of the two types of MWCNTs have different effects on lead toxicity to D. magna. The negatively charged C-MWCNT showed a notable decrease in lead toxicity (LC50 value increased from 0.15 mg L-1 to 1.08 mg L-1 in the presence of 10 mg L-1 C-MWCNT), whereas the positively charged N-MWCNT had only a slight effect on lead toxicity (LC50 value increased from 0.15 mg L-1 to 0.16 mg L-1 in the presence of 10 mg L-1 N-MWCNT). The decrease of lead toxicity was related with the reduced bioavailability of free metal form (Pb2+) caused by greater adsorption of lead onto the MWCNTs. The present study suggests that there is a need to consider carefully the complex interaction of CNTs with toxic metals in future ecotoxicological studies.
Highlights
Increased production and wider application of carbon nanotubes (CNTs) have led inevitably to their entry into the aquatic environment, and this release is likely to bring about unexpected hazards in various organisms [1, 2]
The effects of two different functionalized carbon nanotubes on lead toxicity and bioaccumulation were investigated with a freshwater zooplankton, Daphnia magna
The acute toxicity results indicate that different surface properties of MWCNTs perform differently in affecting
Summary
Increased production and wider application of carbon nanotubes (CNTs) have led inevitably to their entry into the aquatic environment, and this release is likely to bring about unexpected hazards in various organisms [1, 2]. Toxic mechanisms of CNTs toward a variety of organism species have been studied in many in vivo and in vitro tests [3,4,5]. The number of studies investigating the toxic effects of CNTs alone could give invaluable information, in the real environment CNTs coexist with other toxic compounds. CNTs exhibit a very strong adsorption affinity for various environmental contaminants [6,7,8]; they may influence the fate of other aquatic pollutants that surround them, such as toxic metals. Interactions of CNTs with other toxic compounds may influence the transport of toxic.
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