Competitive interactions among H, CU, and Zn ion moderate aqueous uptake of Cu and Zn by an aquatic insect

Environmental Pollution
By: , and 

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Abstract

The absorption of aqueous copper (Cu) and zinc (Zn) by aquatic insects, a group widely used to assess water quality, is unresolved. This study examined interactions among Cu, Zn, and protons that potentially moderate Cu and Zn uptake by the acid-tolerant stonefly Zapada sp. Saturation uptake kinetics was imposed to identify competitive mechanisms. Decreasing pH reduced the maximum transport capacity, Jmax, in both metals, had little effect on the Cu dissociation constant, KD, and increased the Zn KD. Partial noncompetitive (Cu) and partial mixed competitive (Zn) inhibitor models most closely tracked the observed Cu and Zn influx across pH treatments. The estimated values for acid dissociation constants for the binary (proton-receptor) and ternary (proton-metal-receptor) complexes indicated the strong inhibitory effect of protons on Cu and Zn. In neutral pH water, Cu inhibited Zn uptake, but Zn had little effect on Cu uptake. The mechanism of Cu-Zn interaction was not identified. Results from separate Zn experiments suggested that the insect’s developmental stage may affect the apparent Jmax. The study underscores some of the challenges of modeling metal bioaccumulation and informs future research directions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Competitive interactions among H, CU, and Zn ion moderate aqueous uptake of Cu and Zn by an aquatic insect
Series title Environmental Pollution
DOI 10.1016/j.envpol.2019.113220
Volume 255
Issue Part 1
Year Published 2019
Language English
Publisher Elsevier
Contributing office(s) WMA - Earth System Processes Division
Description 113220