Dietary cadmium and benzo(a)pyrene increased intestinal metallothionein expression in the fish Fundulus heteroclitus

Fish were individually fed food pellets containing cadmium, benzo(a)pyrene, or a combination of the two, then analyzed for metallothionein mRNA expression in the intestine, liver, and gill using real-time RT-qPCR. An initial experiment using only cadmium showed that ingestion of pellets varied in individual fish, and estimates of cadmium dose from the numbers of ingested pellets indicated considerable individual variability in cadmium dose. Induction of intestinal metallothionein mRNA was apparent, however, and a linear dose–response relationship was observed for metallothionein expression and cadmium dose in the intestine, but not the other organs, which showed no induction. In a second experiment, the entire daily cadmium dose was provided in a single contaminated pellet that was consumed by all treated fish, effectively eliminating the effect of variable ingestion rates on dose, and the interaction between cadmium and benzo(a)pyrene was also investigated. The intestine was again the primary organ for metallothionein induction by cadmium. When benzo(a)pyrene was administered together with cadmium, induction of metallothionein was potentiated by the presence of benzo(a)pyrene, with the main effect seen in the intestine, where already high levels of induction by cadmium alone increased by 1.74-fold when benzo(a)pyrene was present.     

Influence of HCl/HF treatment on organic matter in aquifer sediments: A Rock-Eval pyrolysis study

Rock–Eval pyrolysis is increasingly used for the routine characterization of natural organic matter in soils and sediments. In this work the bulk composition of sedimentary organic matter (SOM) in sandy aquifer sediments is studied, as well as purified samples (isolation of SOM) by HCl/HF treatment. This treatment is necessary to avoid detection limit problems for samples with low SOM contents, but the results presented here indicate that this treatment influences the organic geochemistry of the aquifer sediment samples. The FID and CO₂/CO pyrograms show a shift of 10–40 °C of the major peak to a lower temperature. Organic matter alteration or removal of components containing O-bearing groups may explain this. It is also suggested that destruction of the mineral matrix may lead to the reduced retention of the material. For the change of the CO₂/CO pyrograms of the RC fraction only organic matter alteration seems to be likely. Concentrated organic matter samples may also accelerate the release of exothermic energy and influence the pyrograms. Results indicate that the organic matter concentration in the sample influences the measured total organic matter (TOM) content and the T_max of the FID pyrogram, while the sample loading (absolute organic matter amount) up to 80 mg in the Rock–Eval apparatus does not. The FID pyrograms can be deconvoluted into four subpeaks, which allows comparison of samples at various depths. Rock–Eval pyrolysis may only be routinely applied to characterize SOM in aquifer sediments when such systematic and analytical phenomena are taken into account.