Bioconcentration of Several Series of Cationic Surfactants in Rainbow Trout

Abstract

Cationic surfactants have a strong affinity to sorb to phospholipid membranes and thus possess an inherent potential to bioaccumulate, but there are few measurements of bioconcentration in fish. We measured the bioconcentration of 10 alkylamines plus two quaternary ammonium compounds in juvenile rainbow trout at pH 7.6, and repeated the measurements at pH 6.2 for 6 of these surfactants. The BCF of the amines with chain lengths ≤ C₁₄ was positively correlated with chain length, increasing ∼0.5 log units per carbon. Their BCF was also pH dependent and approximately proportional to the neutral fraction of the amine in the water. The BCFs of the quaternary ammonium compounds showed no pH dependence and were >2 orders of magnitude less than for amines of the same chain length at pH 7.6. This indicates that systemic uptake of permanently charged cationic surfactants is limited. The behavior of the quaternary ammonium compounds and the two C₁₆ amines studied was consistent with previous observations that these surfactants accumulate primarily to the gills and external surfaces of the fish. At pH 7.6 the BCF exceeded 2000 L kg^-1 for 4 amines with chains ≥ C₁₃, showing that bioconcentration can be considerable for some longer chained cationic surfactants.

Keywords: BCF; alkylamines; fish; kinetic model; pH dependence; quaternary ammonium.

Figure 1

Bioconcentration parameters of all test chemicals at pH 7.6: BCF (upper panel, L kg^–1); k_U (middle panel, L kg^–1 h^–1); k_T (lower panel, h^–1).

Figure 2

Comparison of bioconcentration parameters at pH 6.2 and at pH 7.6: BCF (upper panel); k_U (middle panel); and k_T (lower panel). The BCF for P9 at pH 6.2 is an upper estimate based on concentrations in fish that were below the LOQ.

Figure 3

Comparison of the measured overall resistance for uptake of alkylamines with modeled water perfusion and blood perfusion resistances (T# are tertiary amines with # representing alkyl chain length, S# are secondary amines, and P# are primary amines; L indicates lower pH result).