Equilibrium-based sampler for determining Cu2+ concentrations in aquatic ecosystems.
The bioavailability of potentially toxic metals in aquatic systems is frequently related to the dissolved free metal ion (M2+) concentration. However, typical methods used to determine M2+ are labor intensive or require sophisticated equipment. We developed an inexpensive, in situ sampling device--the "gellyfish"--that simplifies Cu2+ determinations in seawater. The gellyfish is a thin disk of polyacrylamide gel embedded with iminodiacetate (Id) groups bound to immobile beads. The sampler operates on the principle that the immobilized Id groups equilibrate with the Cu2+ concentration of the surrounding solution. Cu is then back-extracted into a known volume of 10% HNO3 and measured by inductively coupled plasma mass spectrometry (ICP-MS). In laboratory tests, we varied Cu2+ concentrations between 10(-12) and 10(-8) M and salinity between 5 and 35 ppt. Id-bound Cu (CuId(measured)) did not respond to changes in total Cu. However, CuId(measured) does increase in a predictable manner with increasing Cu2+, and prototype gellyfish precision (average coefficient of variation = 10%) is sufficient to resolve small differences in Cu2+ (+/-30%). Modeled Cu uptake, based on thermodynamic equilibrium speciation of Id within gellyfish, is a good predictor of CuId(measured) (r2 = 0.96 and n = 45).
Senn
David B
DB
Exposure, Epidemiology, and Risk Program, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, Massachusetts 02115, USA.
Griscom
Sarah B
SB
Lewis
Christopher G
CG
Galvin
Jennifer P
JP
Chang
Martha W
MW
Shine
James P
JP
D000180:Acrylic Resins; D003300:Copper / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation*; D008962:Models, Theoretical; D012623:Seawater / Q000737:chemistry; D012995:Solubility; D013816:Thermodynamics; D014873:Water Pollutants / Q000032:analysis*
D000180:Acrylic Resins; D014873:Water Pollutants; C016680:polyacrylamide gels; D003300:Copper