Environmental resistance water concentration effects

Chlorinated pesticides differ substantially in their toxicity to aquatic plants. Endrin is among the most toxic, inhibiting growth and carbon uptake at concentrations as low as 0.1-1.0 [xg (Menzel etal., 1970). Equally low levels of dieldrin and aldrin may reduce growth, whereas DDT and DDE generally have little inhibitory effect below 1.0 /xg (Luard, 1973 Powers etal, 1975). Development of tolerance to DDT and its derivatives is frequent, and there are several species that are apparently unaffected by DDT levels > 1000 jug L (Luard, 1973). Chlordane generally elicits toxic responses at concentrations < 50 ju.g L and is therefore more toxic than either heptachlor or toxaphene. However, this order is subject to considerable variability, due to the development of resistance, effects of other species-related variables, and differences in environmental conditions. Lindane and its isomers are generally the least toxic of the pesticides and probably pose little threat to aquatic plants in natural waters the majority of species tolerate concentrations > 1000 /xg L (Luard, 1973). 

A very difficult process is the treatment of water contaminated with p-nitrophenols. The presence of the nitro group in their stmcture gives them a strong chemical stability and resistance to microbial degradation. Therefore, reducing the concentration of these compounds in wastewater by adsorption is an environmentally important task besides their detection. Activated carbons are effective adsorbents for... 

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