For release: March 26, 2015
Minn. – The Minnesota Pollution Control Agency is releasing its proposal for
protecting wild rice from excess sulfate. Rather than relying on a single
sulfate level for all wild rice waters in the state, the agency proposes to
calculate a sulfate level for each wild rice water, based on location-specific
study of how sulfate affects wild rice, which began in 2012, finds:
the sediment in which wild rice is rooted, sulfate from the water above is
converted to sulfide by bacteria
levels of sulfide in the sediment create an environment that is less hospitable
to wild rice
factors change the rate at which sulfate is converted to sulfide. Most
significantly, higher levels of iron can lead to less sulfide, and higher
levels of organic carbon can lead to more sulfide.
To take these
variables into account, the MPCA developed an equation that can determine a
sulfate level that will protect wild rice for a specific water body. The agency
proposes collecting sediment samples in wild rice stands, measuring the iron
and organic carbon concentrations in the sediment, and then plugging the data
into the equation to calculate a protective sulfate concentration for that particular
wild rice water.
The MPCA will
be scheduling meetings with interested stakeholders to further describe and get
input on its proposal. The agency will continue to refine the proposal based on
feedback and any new data. At the same time, the MPCA will consider how the
study’s findings will inform regulatory decisions and develop the data
collection protocol needed to implement the proposal. The MPCA plans to go
through formal rulemaking to change the existing standard later this year. The
rulemaking will also include listing specific wild rice waters that are subject
to the standard.
The MPCA has
compiled a draft list of wild rice waters, along with a process to add waters
to the list over time. The list and process are available on the MPCA web site www.pca.state.mn.us/r6wxpf9. The MPCA also proposes that a sulfate
standard is not needed to protect commercial wild rice paddies.
About the study:
In 2012, the MPCA contracted with scientists at the University of Minnesota’s
Duluth and Twin Cities campuses to study the relationship between sulfate,
sulfide, and wild rice with field surveys and laboratory and outdoor container
experiments. The agency integrated and analyzed the data with input from the
study’s advisory committee, and developed a draft analysis that was subject to
scientific peer review in summer 2014. The analysis was then refined based on
the peer reviewers’ recommendations.
A report on the study’s findings is available on the MPCA
web site at www.pca.state.mn.us/r6wxpf9.
Pollution Control Agency is releasing its draft proposal for protecting wild
rice from excess sulfate. Rather than relying on a single sulfate level for all
wild rice waters in the state, the agency proposes to calculate a protective sulfate
level for each body of water, based on location-specific factors. An M-P-C-A study
found that the levels of iron and organic carbon in the sediment in which wild
rice is rooted affect conditions for wild rice growth. The agency has proposed
an equation that will take these factors into account when calculating protective
sulfate levels for wild rice waters around the state.
Find out more
about the M-P-C-A’s proposed approach on the agency web site at www.pca.state.mn.us/r6wxpf9.