RESUMEN
Metal pollution e.g. copper, in water bodies occurs worldwide. Although copper is an essential trace metal, at certain levels it is still considered as pollutant. The aim of this study was to investigate the effect of exposure concentration on copper bioaccumulation in marbled crayfish (Procambarus sp.) by determining uptake and elimination kinetics. Crayfish were exposed to sub-lethal copper concentrations (average measured concentrations of 0.031 and 0.38 mg Cu L(-1)) for 14 d and transferred to copper-free water for another 14 d. At different time points during the uptake and elimination phases copper concentrations were measured in five organs (exoskeleton, gills, muscle, ovaries and hepatopancreas). At 0.031 mg Cu L(-1), copper levels in the crayfish organs were not significantly increased compared to the control animals, suggesting effective regulation. Exposure to 0.38 mg Cu L(-1) did lead to not significantly increased copper levels in muscles and ovaries, while the gills and exoskeleton, which are in direct contact with the water, showed significantly higher copper concentrations. In these four organs, copper showed fast uptake kinetics with equilibrium reached within 10 d of exposure. Copper accumulation was highest in the hepatopancreas; uptake in this storage organ steadily increased with time and did not reach equilibrium within the 14-d exposure period. Copper accumulation levels in the marbled crayfish found in this study were hepatopancreas>gills>exoskeleton>muscle.
Asunto(s)
Astacoidea/metabolismo , Cobre/metabolismo , Contaminantes Químicos del Agua/metabolismo , Animales , Femenino , Branquias/metabolismo , Hepatopáncreas/metabolismo , Cinética , Músculos/metabolismo , Ovario/metabolismoRESUMEN
Levels of toxic substances released into the environment are often highly variable and fluctuate over time. The present study deals with a simple type of time-variable exposure, diluted pulse. We determined toxicokinetic parameters of zinc in guppy fish (Poecilia reticulata) and evaluated the applicability of a toxicokinetics-based survival model developed earlier. In the toxicokinetics experiment, zinc was rapidly taken up and released again; the half-life in fish was only 1.5 d. In the toxicity experiments with diluted-pulse exposure, survival leveled off to a baseline level, which in accordance with the model is explained by the dilution of zinc. The model fitted reasonably well for the lower initial concentrations but tended to overestimate survival rates at the higher concentrations. Toxicokinetic parameters estimated from changes in survival were close to values estimated from measured zinc concentrations in water. Elimination rates during pulse exposure varied from 0.434 to 0.488 d(-1) and corresponded very well to the elimination rate during constant exposure (0.463 d(-1)). Ultimate LC50 values were estimated as 6.40 and 9.10 mg/L. These results suggest that toxicity experiments with a simple, time-varying exposure can be used as an alternative to conventional, constant-exposure experiments. Toxicokinetic parameters and toxicological endpoints can still be estimated in static bioassays with decreasing exposure if the concentration in the medium is measured. At the same time, diluted-pulse experiments may simulate exposure from discharges in the field better than constant-exposure experiments.
Asunto(s)
Exposición a Riesgos Ambientales , Poecilia , Contaminantes Químicos del Agua/toxicidad , Zinc/farmacocinética , Zinc/toxicidad , Animales , Agua Dulce , Semivida , Indonesia , Cinética , Modelos Biológicos , Factores de Tiempo , Contaminantes Químicos del Agua/farmacocinéticaRESUMEN
Elevated environmental concentrations of metals are usually associated with the impact of urbanization. The present study is focused on metal contamination in urban sediments. A field survey was carried out to determine the distribution of four metals, i.e., cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn), in the coastal urban area of Semarang, Central Java, Indonesia. Sediment samples were collected from 101 grids of 2x2 km. To map the spatial distribution of these metals, concentrations of each metal were plotted against the corresponding grid coordinate. Cd was below the detection limit (<0.03 microg/g) in all samples, whereas concentrations of Pb, Zn, and Cu fell into a wide range. Frequency distributions of Pb, Zn, and Cu concentrations indicated a similar pattern, in which the major proportion of the sites had a low metal concentration. Some sites, however, had extremely high metal concentrations, Zn up to 1257 microg/g, Pb up to 2666 microg/g, and Cu up to 448 microg/g. The data were used to define background concentrations for sediments in coastal zones of Indonesia ("reference values"). The proposed reference values are 25.6 microg/g, 132.2 microg/g, and 40.7 microg/g, respectively, for Pb, Zn, and Cu. The degree of metal contamination of each individual site was classified according to the calculated value of a combined pollution index, W. Four categories of the degree of metal contamination were proposed, i.e., unpolluted, slightly polluted, polluted, and heavily polluted. Based on this classification, from 101 sites investigated in the greater Semarang area, 51 are unpolluted, 36 slightly polluted, 9 polluted, and 5 heavily polluted.
Asunto(s)
Sedimentos Geológicos/química , Metales/análisis , Contaminantes Químicos del Agua/análisis , Cadmio/análisis , Cobre/análisis , Indonesia , Plomo/análisis , Zinc/análisisRESUMEN
The present study aims to answer the question whether the amount of metal in aquatic biota reflects the concentrations in the sediment and water, and whether the physico-chemical properties of the water and sediment have any influence on the suspected relationship. A study was made of 101 small streams in the city of Semarang, Central Java, Indonesia. Data on fish occurrence in 63 streams of the greater Semarang indicated that the guppies did not avoid the highly polluted sites. No significant difference in body weight between sites was found. Significant differences were found in metal body concentrations (Pb and Zn) between fish collected from sites with different degrees of pollution. A significant declining trend of Pb concentrations with increasing organism size was observed, whereas for two other metals, Zn and Cu, the concentrations did not depend on the body weight. Apparently, body concentrations of these two metals are regulated and maintained at a certain concentration. For the relationships between metal concentrations in water, sediment and fish, water and sediment parameters, and fish dry weight, the presence of significant multiple correlations and bivariate correlation (in 17 of 91 pairs of variables) indicated that, in general, abiotic parameters and body size had no influence on the metal flux from sediment to water, and into fish. Results of partial correlation analyses further suggested that metal concentrations in the sediments were the most important factor governing the metal body concentrations of fish. The present study indicates that the guppy Poecilia reticulata from urban streams is a potential bioindicator for urban metal pollution, especially with respect to their (1) spatial distribution over sites of all pollution regimes and (2) variation in metal accumulation levels reflecting the degree of pollution.