such as "Introduction", "Conclusion"..etc
WI, JULY 14, 2008– Land application of biosolids (treated municipal
sewage sludge) is a common practice because biosolids are a rich source
of plant nutrients and organic matter. However, the presence of
detectable levels of dioxins in biosolids led to concerns that farmland
application may result in accumulation of dioxins in soil and their
subsequent translocation through the human food chain because several
congeners of dioxins have extremely high bioaccumulation potential. The
USEPA evaluated the risk of dioxins in land applied biosolids and
concluded that dioxins from this source do not pose a significant risk
to human health or the environment. However, there is very little
information available on the effect of long-term application of
biosolids on accumulation of dioxins in soil and uptake by plants.
at the Metropolitan Water Reclamation District of Greater Chicago
(District) investigated the effects of continuous and long-term
application of biosolids on the levels of dioxins in soil and corn
tissues collected from the District's long-term field plots that were
established in 1973. Specifically, they collected soil, corn grain, and
corn stover samples from the field plots consisting of a 0 (control),
504, and 2016 Mg ha-1 cumulative biosolids loading applied through
annual applications from 1973 to 2002 and measured 29 congeners of
dioxins, furans, and polychlorinated biphenyls (PCBs). Results from
this study were published in July-August 2008 issue of the Journal of Environmental Quality. This research was also presented at the Sustainable Land Application Conference held in January 2004 in Orlando, Fla.
study revealed that the levels of dioxins in soil from the control and
agronomic rate biosolids plots were not statistically different but the
soil levels of dioxins were much higher in the plots that have been
receiving four times higher rates of biosolids application. Dioxins
were not detected in the corn grains. Only trace levels were found in
the corn stover, and there was no statistical difference between the
control and the biosolids-amended plots. These observations suggest
that dioxins from land application of biosolids do not pose any risk to
human health or the environment, if biosolids are land applied
according to the USEPA regulations.
The District has
on-going research to investigate the trend of dioxins levels in
biosolids over time. The USEPA's 2001 Dioxins Update to the National
Sewage Sludge Survey indicated that dioxins levels in biosolids have
declined since the last USEPA survey in 1988. This downward trend is
expected to continue due to the regulatory controls on additional
sources of dioxins in the environment, particularly on some combustion
practices. These findings support the USEPA's decision not to regulate
dioxins in land applied biosolids.
American Society of Agronomy. Public release date: July 14, 2008.
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