270Trace Elements with Toxicity
Chromium as hexavalent Cr(VI)
Nickel – nickel salts are carcinogenic
Copper – copper toxicity
Zinc - zinc toxicity
Iron – iron poisoning
Fluorine-fluoride poisoning
Nonmetals
Some heavy nonmetals may be erroneously called "metals", because they have some
metallic properties.
Selenium – a nonmetal; essential element
Tellurium
Atomic Spectrometry
Atomic spectrometry converts each metal in the water sample to a particulate emission
that can then be weighed. Extrapolations are made to determine each metal concentration
in each water sample taken. The complicated analysis requires preserving the sample
with acid, heating the sample to convert to a particulate emission and then identifying each
metal and its weight.
A simple analogy is to capture the steam from a pot of water, separate every atom in the
steam, identify each atom, weigh each atom and then apply these numbers back to the
original volume of water contained in the pot. The result is an accurate picture of what is
in the water.
Heavy Metals in Water
High heavy metals concentrations can be naturally occurring. Every geologic formation
contains a certain amount of heavy metal. Mine operations extract and process these
metals in areas with the highest concentrations. Water in these areas may have high metal
concentrations due to the combination of naturally occurring deposits and mine waste.
Water samples are usually taken randomly within a contaminated area and offsite to
identify the source of contamination and the pathway it travels, into the drinkable
groundwater system or away from potable water sources. Accurate determination of heavy
metal contamination is important to identify cumulative risks to people drinking water
derived from these areas.
Treating Heavy Metal Contamination in Water
Heavy metal water contamination is a difficult expensive problem to address. Most
cleanup activities use a pump and treat system where contaminated groundwater is
pumped out of the ground, treated with activated carbon to remove contaminants and then
replaced into the groundwater system. Because large volumes of water must be pumped
and treated over long time periods, associated operation and maintenance systems are
very expensive. There are some new technologies being developed that actually treat the
water in the ground which operate more efficiently and quickly, decreasing costs.
If groundwater is contaminated with heavy metals, an alternative source of drinking water
must be used to prevent harmful health effects, until the water is treated to meet standards
protective of human health and the environment