Trace elements often enter waterbodies with discharges from sewage treatment plants, industrial plants, and other sources. Some trace elements are toxic in high concentrations, though toxicity is often dependent on the ambient pH or the presence of other elements. Arsenic, Lead and Mercury are all examples of elements that can be toxic in tiny amounts and are commonly present in pesticides, insecticides and landfill leachates.
:
;Salinity
;TDS
;Aquatic Life
;Water Quality
Trace Elements:
Chemical elements appearing in minute quantities in natural systems or media; may occasionally be concentrated by specific organisms. Nutrients such as Phosphorus or Nitrogen, though in minute quantities, are not usually called trace elements (ref).
This site (link opens in a new window) has links to the biological effects of every element. First, select the element you are interested in, than choose "Biology" from the left-hand menu.