NOTE:
These narratives that provide a detailed description of the parameter,
the rationale for its inclusion, specific test methods, and other
information.
Initially, it
is suggested that only qualitative data be provided to customers
pertaining to trace elements/heavy metals. This approach has been
taken because providing an all?inclusive chemical analysis to customers
would be overkill in most situations, and impractical. It may also
feed the phobia surrounding the use of waste?derived products. Instead,
a quality assurance statement would be offered in its place. For
example, our product meets the Federal EPA's definition for an exceptional
quality product, or our product is approved for unlimited distribution
and therefore can be used on . . . . It would further be suggested
that data showing trace element content of the product be made available
upon request and presented in a usable form. A statement may even
be made, such as: our product contains trace elements at various
levels necessary for plant growth; quantitative data is available
upon request. This data may be necessary to assist specific end
users in adjusting their fertilization programs to avoid phytotoxicity.
Trace Elements/Heavy Metals: Heavy metals
are trace elements whose concentrations are regulated due to the
potential for toxicity to humans, animals, or plants. Regulations
governing the heavy metal content of composts derived from specific
feedstocks have been promulgated on both the state and federal
levels. Trace elements, referred to as heavy metals are arsenic,
cadmium, chromium, copper, lead, mercury, molybdenum, nickel,
selenium, and zinc. Many of these elements are actually needed
by plants for normal growth. Therefore, measuring the concentration
of these elements, as well as other plant nutrients, will provide
valuable management data relevant to the fertilizer requirements
of plants, and subsequent fertilizer application rates. Specified
heavy metals and trace elements are also known to cause phytotoxic
effects in plants, and specific plant species are more sensitive
than others. These elements are boron, manganese, molybdenum,
nickel, and selenium. Although none are typically found in compost
in detrimental quantities, some can accumulate in the root zone
over time. Therefore, to avoid the potential of plant damage,
these elements should be monitored and reduced when necessary.
The quantity of these elements is measured on a dry weight basis
and expressed as mg/kg or ppm. Data on heavy metals should be
available to customers upon request, and an understanding of the
potential health and environmental impacts of these elements,
as they relate to compost, is essential to address public concern.
