Toxic Effects of Heavy Metals and Organic Polycyclic Aromatic Hydrocarbons in Sediment Porewater on the Amphipod Hyalella azteca and Zebrafish Brachydanio rerio Embryos from Different Rivers in Taiwan

The amphipod (Hyalella azteca) and zebrafish (Brachydanio rerio) embryos were used for toxicological sediment porewater testing. Porewaters from 35 sampling stations of eight streams in southern Taiwan were screened for toxic effects and their relationship with 6 metal and 16 polycyclic aromatic hydrocarbons (PAHs). Concentration analysis results showed that the following PAHs, naphththalene, benzo(b)fluoranthene, dibenz(a,h)anthracene, acenaphthalene, and the heavy metal cadmium were not detected in 35 sampling stations. The highest detection rate of 94.1% was caused by the PAHs fluoranthene and pyrene. The highest detection rate of the metal zinc was 88.6% of 35 analyzed samples. The majority of samples (88%) were classified as level tier 1 according to USEPA national sediment inventory. This indicates the probability of adverse effects on aquatic life or human health. The results of a zebrafish embryo test showed that heart rate and survival were significantly reduced with all porewater samples. Therefore, fish exposed to contaminated river conditions may be affected in their cardiovascular functions. Looking at correlations between toxic effects of metals and PAHs, we found that phenanthrene, anthracene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, and benzo(a)pyrene were low, while fluorene was highly correlated with toxic effects of metals.

The Acute Toxicity of Thulium to Hyalella Azteca and the Influence of Toxicity Modifying Factors.

The demand for rare earth elements (REEs) is growing and as a result, environmental exposure is a concern. The objective of this research was to evaluate the acute toxicity of Tm to Hyalella azteca and to understand the potential for toxicity modification by dissolved organic matter (DOM) and the cations Ca2+, Mg2+ and Na+. Standard methods were followed for 96 h static exposures in a medium with a hardness of 60 mg CaCO3/L, pH of 7.3 at 23°C. H azteca neonates (2-9 d of age) were used and in unmodified media the LC50 concentration was 3.4 µM (95% CI 2.9-3.9 µM; 573 µg/L (482-663)) based on measured dissolved concentrations at the end of the test. Tests done with different concentrations of Ca (0.25, 0.5 and 1.5 mM) did not show consistent trends and there was no clear evidence of a protective effect from Ca. Variations in Na (0.26, 0.5 and 1.6 mM) resulted in no significant changes in toxicity. Similarly, Mg (0.07, 0.14 and 0.4 mM) did not result in significant changes in LC50 values, except for a reduction in toxicity for measured total Tm at the lowest Mg concentration. Our results indicate that Tm toxicity is not influence by cationic competition (Ca, Na and Mg). Dissolved organic matter (sourced from Luther Marsh ON) offered significant protection against Tm toxicity. Additions over 3 mg DOC/L resulted in significantly increased LC50 values. This study contributes toward understanding the toxicity of Tm and the importance of considering dissolved organic matter in estimating the potential for environmental risk of REEs.

Environmental assessment of stormwater pond impacts on a Rouge River tributary

This study was conducted to evaluate impacts of stormwater ponds in the Municipality of the Town of Richmond Hill on select physical (temperature, dissolved oxygen, and pH) chemical (nutrients) and biological (macroinvertebrate community, macrophyte and experimental Hyalella azteca and Daphnia magna enclosures) aspects of a Rouge River tributary. Over a five-month period five sites along the tributary close to the outfall of the stormwater ponds were sampled to determine if there were any impacts, cumulatively (with increasing number of pond outfalls along the tributary) and locally (above and below an outfall). Physical and nutrient parameters showed no signifiant degradation in water quality, either cumulatively or locally. Macrophytic data showed some decrease in biomass at downstream sites, but no decrease in diversity or species richness. Survivorship in the enclosures containing Hyalella azteca and Daphnia magna showed no significant cumulative change. Analysis of the macroinvertebrate community showed no cumulative or local impact until the farthest downstream site.

Environmental assessment of stormwater pond impacts on a Rouge River tributary

This study was conducted to evaluate impacts of stormwater ponds in the Municipality of the Town of Richmond Hill on select physical (temperature, dissolved oxygen, and pH) chemical (nutrients) and biological (macroinvertebrate community, macrophyte and experimental Hyalella azteca and Daphnia magna enclosures) aspects of a Rouge River tributary. Over a five-month period five sites along the tributary close to the outfall of the stormwater ponds were sampled to determine if there were any impacts, cumulatively (with increasing number of pond outfalls along the tributary) and locally (above and below an outfall). Physical and nutrient parameters showed no signifiant degradation in water quality, either cumulatively or locally. Macrophytic data showed some decrease in biomass at downstream sites, but no decrease in diversity or species richness. Survivorship in the enclosures containing Hyalella azteca and Daphnia magna showed no significant cumulative change. Analysis of the macroinvertebrate community showed no cumulative or local impact until the farthest downstream site.