当前位置： SCI文献检索 > ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY期刊下所有文献 > Uptake and elimination of ionizable organic chemicals at fish gills: II. Observed and predicted effects of ph, alkalinity, and chemical properties.

Uptake and elimination of ionizable organic chemicals at fish gills: II. Observed and predicted effects of ph, alkalinity, and chemical properties.

Abstract：

:Effects of exposure-water pH on chemical uptake at rainbow trout (Oncorhynchus mykiss) gills were investigated for nine weakly acidic, chlorinated phenols with different ionization constants and hydrophobicities and for a moderately hydrophobic, nonionizable reference chemical (1,2,4-trichlorobenzene). Uptake rates for all chemicals varied little from pH 6.3 to 8.4, despite ionization of the chlorinated phenols ranging from less than 1 to greater than 99.9% among these pH values and chemicals. At pH 9.2, uptake rates were reduced substantially for the chlorinated phenols but not for the reference chemical. These results indicate greater bioavailability of neutral chemical forms but also considerable bioavailability of ionized forms that varies with pH. Three mechanisms were evaluated regarding such ionized chemical bioavailability. First, reduced pH at the gill surface causes net conversion of ionized molecules to more readily absorbed neutral molecules. This mechanism was tested by increasing exposure-water alkalinity, which increased gill surface pH and reduced uptake of the chlorinated phenols but not of the reference chemical. Magnitudes of these effects were close to predictions from a mathematical model for chemical exchange at fish gills that incorporated this mechanism. Second, ionized molecules contribute to uptake by maintaining high gradients of neutral molecules across epithelial membrane barriers, even if the barriers are impermeable to these ions. This mechanism was demonstrated to explain the similarity of uptake among pH values and chemicals at pH less than 8.4 and the degree to which uptake declined at pH 9.2. Third, membrane barriers can have some permeability to the ionized forms, but this was not important for the chemicals and conditions of the present study. Increased exposure-water pH also was demonstrated to increase elimination rates of these chemicals, which also was in accord with model expectations.

journal_name

Environ Toxicol Chem

journal_title

Environmental toxicology and chemistry

authors

Erickson RJ,McKim JM,Lien GJ,Hoffman AD,Batterman SL

doi

10.1897/05-359r.1

subject

Has Abstract

pub_date

2006-06-01 00:00:00

pages

1522-32

issue

eissn

0730-7268

issn

1552-8618

journal_volume

pub_type

杂志文章

在线工具

Uptake and elimination of ionizable organic chemicals at fish gills: II. Observed and predicted effects of ph, alkalinity, and chemical properties.