Polybrominated diphenyl ethers (PBDEs) have been used extensively over the past two decades as flame retardants in most types of polymers. Many measurements of PBDEs in various environmental matrices from Sweden, Holland, Japan, and elsewhere have been reported, but few measurements are available for North America. PBDEs in 21 coho and chinook salmon taken from Lake Michigan tributaries in 1996 were measured for this study. The salmon samples were extracted and initially analyzed for polychlorinated biphenyl (PCB) congeners. It was demonstrated for these samples that the same extract fraction contains PBDEs. Six PBDE congeners were observed in all 21 samples, and the rank order of concentration of these congeners was similar to that in commercial mixtures of PBDEs. The average concentration across all samples of the sum of PBDE congeners was 80.1 ng/g of wet weight or 2,440 ng/g of lipid. This is much less than the average sum PCB concentration (1,450 ng/g of wet weight; 43,100 ng/g of lipid). However, the average concentration of the most abundant PBDE congener (IUPAC BDE-49: 52.1 ng/g wet, 1,590 ng/g of lipid) was about one-third of the average concentration of the most abundant PCB congener (IUPAC CB-153: 149 ng/g wet, 4,550 ng/g of lipid). On the basis of an extensive literature survey, the concentrations of PBDEs reported here are among the highest in the world for salmon in open waters. The concentrations of PBDEs and PCBs are both correlated with fish length and mass, but not with lipid content. The concentrations of PBDEs and PCBs are highly correlated in individual fish, implying that PBDEs are as prevalent as PCBs in Lake Michigan.

The limit of detection and limit of quantification are current critical issues in environmental testing. In most laboratories, limits are currently calculated on the basis of the standard deviation of replicate analyses at a single concentration. However, since the standard deviation depends on concentration, these single-concentration techniques result in limits that are directly dependent on spiking concentration. A more rigorous approach uses a weighted least-squares regression analysis of replicates spiked at a series of concentrations [Formula: see text] a calibration design. In this work, the use of weighted tolerance intervals is introduced for estimating detection and quantification limits. In addition, models for estimating the weights used in calculating weighted prediction intervals and weighted tolerance intervals are presented. Using this method, detection and quantification limits were calculated for gas chromatographic analyses of 16 polychlorinated biphenyls. Results show that the approach developed provides improved estimates of analytical limits and that the single-concentration approaches currently in wide use are seriously flawed. Future work should reduce the data needed for the calibration design approach so that more rigorous detection and quantification limits can be routinely applied.

Interpretation of the potential bioavailability of phosphorus forms and fractions indicates some of the P entering lakes may have a limited effect on lake productivity. Some P sources, such as land runoff, are often high in particulate P, significant portions of which cannot be utilized in the growth of algae and higher plants. Based on existing information (mostly from Great Lakes studies), potentially bioavailable P in tributaries generally does not exceed 60% of the total P and is often considerably less. Potentially bioavailable P is shown to correspond to the dissolved reactive P (DRP) plus the fraction of particulate inorganic P obtained by extraction with 0.1N NaOH. Whether potentially bioavailable particulate P actually becomes available in a receiving water depends on factors such as the receiving‐water DRP concentration and the position (location) of the particle in the water. A mathematical model, combining two classical modeling approaches, is used to illustrate the importance of positional limitation. Consideration of bioavailability in eutrophication‐control strategies should lead to more cost‐effective management.