Cobalt:: freshwaters ecosystems
Key Concerns
Key Concerns
Key Concerns
Key concerns
The toxicity of cadmium to aquatic organisms is variable, and it depends on both the species and environmental factors such as water hardness, salinity, temperature, pH, organic matter content and the presence of other metal ions, especially calcium and zinc (WHO 1992). Toxicity to aquatic organisms generally increases with increasing temperature and decreasing salinity and hardness. Early life stages of organisms, especially embr yonic and larval stages, are more sensitive to the effects of cadmium than the adult stage.
Key concerns:
Boron toxicity in plants is most likely to occur following the continued use of boron-contaminated irrigation waters, however, direct exposure from airborne emissions may also produce localized toxic effects (Howe 1998). Symptoms of boron toxicity in plants include yellowing, spotting or drying of leaf tissues, especially on the tips and sides of older leaves (Gupta et al. 1985).
Key Concerns:
Concentrations of arsenic in soil reported to be toxic to plants span a broad range (WHO 2001), and toxicity is generally higher in sandy soils than clay soils (Sheppard 1992).
Additional Comments:
Key Concerns:
There is a paucity of data on the effects of antimony on species and their ecosystems.
Emissions of antimony, such as those from smelters, can remain in the atmosphere for more than one month and therefore be transported over long distances (ATSDR 1992; Steinnes 1997). Antimony in soil is likely to be in the form of antimony sulphide, which is slightly soluble, and therefore potentially bioavailable.
Key Concerns:
PAHs are acutely toxic to aquatic organisms due to the formation of toxic metabolites. The PAHs which are most toxic to algae are benz(a)anthracene and benzo(a)pyrene, with EC50 values ranging from 1 to 29 µg/l and 5 to 15 µg/l, respectively (WHO 1998). Corresponding EC50 values for 3 ring PAHs range from 240 to 940 µg/l. Naphthalene is less toxic than other PAHs, with EC50 values in algae ranging from 2800 to 34 000 µg/l.
Key Concerns:
Reduced growth of the aquatic angiosperm Spirodela oligorhiza was reported following exposure to 5 mg/l PCBs (Aroclor 1242) for 14 days (Mahanty 1975). Symptoms of toxicity included reduced frond size with a characteristic striped chlorosis.
Key Concerns:
Key Concerns:
Hydrogen fluoride (HF) is the most phytotoxic of all air pollutants. It accumulates in the margins and tips of leaves, and in sensitive taxa it causes:
