74 Using Multi-media Modeling to Investigate Conditions …
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but will dominate the cyanobacteria community with just small amounts available
[2]. Microcystis blooms are more toxic, longer in duration and are more extensive
than the earlier P-limited cyanobacteria communities experienced in the late 1960’s
and 1970’s. A better understanding of the environmental conditions leading to the
proliferation of these differing cyanobacteria communities may be gleaned through
using physics-based, mass-balanced models that simulate the transport of nutrients
through the land, air and water.
QUESTIONER: Clemens Mensink
QUESTION: To what extent do you think we understand the different processes? In
other words, where are the biggest knowledge gaps to be found?
ANSWER: The cycling of nutrients throughout the environment is complex and
extremely variable across time and space. Our understanding of these processes are
limited, and data are sparse. Particular knowledge gaps include the biogeochemical
cycling associated with nutrients (e.g., interactions involving microbes, organic N,
nitrous oxide, carbon), and limitations in measurements (e.g., flux, dry deposition)
and input data (e.g., soils, landcover, location/emissions of animal feeding operations).
QUESTIONER: Camilla Geels
QUESTION: You mention NH 3 is an imporant factor. It is well known that the
application of manure and the following NH 3 emissions to the atmosphere is very
dependent on the weather. To what degree do you include that in the atmospheric
model? And is the spatial resolution of the atmospheric model high enough to describe
the dry deposition of NH 3 ?
ANSWER: Temperature dependent processes, such as the increase in NH 3 volatilization as ambient temperature increases, is calculated for croplands (e.g., from applied
fertilizer) and other non-agriculture vegetation. Emissions from animal feeding operations are based on animal density data and are seasonally adjusted. While CMAQ
is run at a 12 km x 12 km resolution, relevant variables needed for calculating deposition and evasion are based on the varying landuse types within this grid structure
(sub-grid level). This resolution is appropriate for the long-term objective of this
study (national screening-level assessment of large waterbodies in the US to harmful
algal blooms), however, it is recognized that NH 3 deposits locally, and running the
model at a finer resolution would be valuable.
QUESTIONER: Paul Maker
QUESTION: What EPIC variables are being fed back into CMAQ as part of the
2-way coupling shown in one of your figures?
ANSWER: Fertilizer rates, depths and timing, and managed soil information are
passed from EPIC to CMAQ on a daily time step. CMAQ uses this information to
calculate the soil NH 4 pool, which in turn is used to calculate the NH 3 air-surface
flux.
Disclaimer The views expressed in this paper are those of the authors and do not necessarily reflect
the views and policies of U.S. Environmental Protection Agency.
473
but will dominate the cyanobacteria community with just small amounts available
[2]. Microcystis blooms are more toxic, longer in duration and are more extensive
than the earlier P-limited cyanobacteria communities experienced in the late 1960’s
and 1970’s. A better understanding of the environmental conditions leading to the
proliferation of these differing cyanobacteria communities may be gleaned through
using physics-based, mass-balanced models that simulate the transport of nutrients
through the land, air and water.
QUESTIONER: Clemens Mensink
QUESTION: To what extent do you think we understand the different processes? In
other words, where are the biggest knowledge gaps to be found?
ANSWER: The cycling of nutrients throughout the environment is complex and
extremely variable across time and space. Our understanding of these processes are
limited, and data are sparse. Particular knowledge gaps include the biogeochemical
cycling associated with nutrients (e.g., interactions involving microbes, organic N,
nitrous oxide, carbon), and limitations in measurements (e.g., flux, dry deposition)
and input data (e.g., soils, landcover, location/emissions of animal feeding operations).
QUESTIONER: Camilla Geels
QUESTION: You mention NH 3 is an imporant factor. It is well known that the
application of manure and the following NH 3 emissions to the atmosphere is very
dependent on the weather. To what degree do you include that in the atmospheric
model? And is the spatial resolution of the atmospheric model high enough to describe
the dry deposition of NH 3 ?
ANSWER: Temperature dependent processes, such as the increase in NH 3 volatilization as ambient temperature increases, is calculated for croplands (e.g., from applied
fertilizer) and other non-agriculture vegetation. Emissions from animal feeding operations are based on animal density data and are seasonally adjusted. While CMAQ
is run at a 12 km x 12 km resolution, relevant variables needed for calculating deposition and evasion are based on the varying landuse types within this grid structure
(sub-grid level). This resolution is appropriate for the long-term objective of this
study (national screening-level assessment of large waterbodies in the US to harmful
algal blooms), however, it is recognized that NH 3 deposits locally, and running the
model at a finer resolution would be valuable.
QUESTIONER: Paul Maker
QUESTION: What EPIC variables are being fed back into CMAQ as part of the
2-way coupling shown in one of your figures?
ANSWER: Fertilizer rates, depths and timing, and managed soil information are
passed from EPIC to CMAQ on a daily time step. CMAQ uses this information to
calculate the soil NH 4 pool, which in turn is used to calculate the NH 3 air-surface
flux.
Disclaimer The views expressed in this paper are those of the authors and do not necessarily reflect
the views and policies of U.S. Environmental Protection Agency.