Dry deposition monitoring methods in Alberta

2006·4.1 MB·English

by  WBK & Associates Inc

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Dry Deposition
Monitoring
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Alberta
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Digitized by the Internet Archive
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https://archive.org/details/drydepositionmonOOwbka
Dry Deposition l\/lonitoring l\/lethods in
Alberta
Prepared
for:
Alberta Environment
Edmonton, Alberta
Final Report
By:
WBK & Associates Inc.
St Albert, Alberta
March 2006
ISBN: 978-0-7785-7583-2 (Printed)
ISBN: 978-0-7785-7584-9 (On-line)
Web Site: http://www.gov.ab.ca/env/
Any comments, questions, or suggestions regarding the content ofthis document may
be directed to:
Air Policy Branch
Alberta Environment
11th Floor, Baker Centre
10025-106 Street
Edmonton, AB
T5J 1G4
Fax: [phone]
Additional copies of this document may be obtained by contacting:
Information Centre
Alberta Environment
Main Floor, Oxbridge Place
9820- 106th Street
Edmonton, Alberta T5K 2J6
Phone: [phone]
Fax: [phone]
Email: env.infocent(a)qov.ab.ca
FOREWORD
Acid deposition occurs when acidifying pollutants emitted from anthropogenic and other
processes undergo chemical reactions in the atmosphere and fall to the earth as wet
deposition (rain, snow, cloud, fog) ordry deposition (dry particles, gas). Acidic
pollutants can be transported long distances in the atmosphere from their sources and
eventually be deposited in ecosystems overbroad regional scales and in locations far
from the emission sources.
Dry deposition is generally more a local problem than wet deposition. Direct
measurement ofdry deposition rates is difficult. Dry deposition depends on many
factors, including: meteorological conditions, characteristics ofthe pollutants being
deposited (e.g. different gaseous chemical andparticle size), andcharacteristics ofthe
surface on which deposition occurs.
The most accepted and common method forestimating dry deposition is the so-called
"inference method." The inferential method is acombination ofmeasurement and
modeling that involves indirect estimation ofdry deposition rates on the basis of
routinely measured airconcentrations and meteorological parameters. The method is
based on an assumed steady-state relationshipF = Vd C, where the dry deposition flux or
rate (F) is aproduct ofthe dry deposition velocity (Vd) and the concentration (C) ofan
airborne pollutant.
A series ofstudies have been initiatedby AENV to evaluate the inference method and
search forthe most suitable and simple model for deposition rate estimations in Alberta.
This report documents the second study in the series. Titles forthe reports ofthe other
studies are: ''Review andAssessmentofMethodsforMonitoring andEstimating Dry-
Deposition inAlberta", and "RefinementStudy ofDryDeposition InferenceMethod
UsedinAlberta It is anticipatedthat once all necessary information is gathered, an
Albertaprotocol fordry deposition measurement will be prepared.
Lawrence Cheng, Ph. D.
AirPolicy,
Climate Change, Air and LandPolicy Branch
Dry Deposition Monitoring Method inAlberta
SUMMARY
Currently there is no standard method for field measurement and estimation ofdry
deposition ofacidifying pollutants in Alberta. AlbertaEnvironment is pursuing
development ofan inexpensive standard method. This may involve acombination of
continuous, intermittent, and/orpassive field measurements ofacidifyingpollutants and
using inference methods forestimating sulphur and nitrogen species dry deposition. An
overall objective ofthis study was to continueevaluating inferential methods for
estimating dry deposition rates.
Dry Deposition Methods Evaluation
Three different inference methods used in Canada were evaluated forestimating sulphur
and nitrogen species dry deposition. These methods were developedby Alberta
Environment (AENV), Environment Canada (ENVC), andthe WoodBuffalo
Environmental Association (WBEA). A specific objective was to use theseinference
methods to compare contributions ofgaseous SO2, NO2, HNO3, HNO2, andparticulate
forms ofsulphur (S04^') and nitrogen (NO3' andNH/) in total sulphur andnitrogen
deposition andtheirpotential relationships among each method. Another specific
objective was to identify andrecommend apreferredmethod (ormethods) thatcouldbe
routinely used forestimating sulphurandnitrogen species dry deposition rates. The
following findings are noted:
1. Complete sulphur and nitrogen gaseous andparticulate species and
meteorological datafor a one-yearperiod (2003) from theWoodBuffalo
Environmental Association FortMcKay airmonitoring station wereevaluated
using the three methods. All three methods showed a similarabilityto represent
variation in dry deposition rates forindividual species from month to month.
WBEA
2. The method yieldedhighermonthly deposition rates formost species
modeled (S04^", NO2, HNO3, HNO2, andNH4^) comparedto theAENV and
ENVC methods. Monthly potential acid input (PAI) associated with dry species
WBEA
foreach method is shown in Figure ES-1. The method also yielded
higherPAI associated with dry species compared to the AENV andENVC
methods during winter and spring. The WBEA method gave similarPAI values
associated with dry species during summerandfall. A simplercomputational
approach for aerodynamic and surface resistance terms in the WBEAmethod may
partially explain differences observed during winterand spring. Furthertesting
wouldbe requiredto betterunderstand whetherthis is thecase.
3. Annual total PAI associated with dry species for2003 was 0.14 kg H^/ha/yr
(AENV method), 0.15 kg H^/ha/yr (ENVC method), and 0.20kg H"'/ha/yr
(WBEA method). The higher annual rate observed fortheWBEA method
relative to othermethods is consistentwith higher monthly deposition rates for
individual species. While the AENV andENVC methods yieldedcomparable
monthlyPAI values associated with dry species, it is observed thatENVC input
Dry Deposition IVIonitoring Method in Alberta ii
parameters have more boundary conditions (i.e. cut-offpoints and lower/upper
limits) associated with their use compared to AENV input parameters.
0.04
FigureES-1. Monthlypotential acid input (PAI) values associated with dry species
forthe periodJanuary to December2003 at WBEA Fort McKay air
monitoring stationAMS #1 (expressed in unitsofkg H+/ha/month).
(ENVC=EnvironmentCanadamethod;AENV=AlbertaEnvironmentmethod;
WBEA=WoodBuffaloEnvironmentalAssociationmethod)
4. TheENVC method is more complicated given that ithas the greatest numberof
inputparameterrequirements. A numberofadditional assumptions for some of
the inputparameters are also requiredbefore modelingcan be performed. The
AENVmethodprovided comparativeresults to the ENVC method. The AENV
method is less complicatedcomparedto the ENVC method, and it requires less
WBEA
inputdataandcomputing time. The method is simple and straight-
forwardto use. However, this method yieldedhighermonthly deposition rates for
most species modeled compared to the othermethods using the 2003 dataset.
5. The dataset usedto evaluate the methods was short-one year- and month to
month variation orlack ofvariation in species deposition rates observed using
each method does not necessarily provide an indication ofwhat may happen in
otheryears. Although only aone-yeardataset was available forevaluation.
Dry Deposition Monitoring Method in Alberta ill
results support that the AENV method offers apractical choice forroutine
computation ofsulphur and nitrogen species dry deposition in Alberta. Further
testing using different datasets elsewhere in Alberta is recommendedto support
this. Ifthe ENVC method can be shown to provide comparable results to the
AENV method using different datasets, it would offer alogical choice for
periodic use as acheck on the AENV method.
6. Evaluation ofcontributions ofSO2 and NO2 deposition in total sulphurand
nitrogen species deposition atthe FortMcKay site indicated that about 82% is in
the form ofgaseous SO2 with the remainder as particulate 804"" (18%). These
results are comparable to annual deposition loadings ofsulphur species during
1998 to 2002 at the formerAlbertaEnvironment Beaverlodge acid deposition
monitoring site (80% in the form ofgaseous SO2 and 20% as particulate S04^').
Estimates ofannual nitrogen species deposition at the FortMcKay site indicated
that -51% was from NO2 with the remainder as HNO3 and HNO2 (35%) and
particulate NH4^ and NO3' (<14%). Estimates ofannual nitrogen species
deposition at the Beaverlodge site during 1998 to 2002 showedthat about 35 to
50% was from NO andNO2 with theremainder as HNO3 and HNO2 (40 to 60%)
andparticulate NH4^ and NO3" (<10%).
7. Future workevaluating these inference methods shouldconsiderthe influence of
assigning additional boundaryconditions to AENV model inputparameters on
variability associated with model outputs. Specifically, assigningboundary
conditions to AENV inputparameters consistent with defaultENVC model
assumptions shouldbe investigated tobetterunderstand whetherthese changes
have the ability to improve AENV model performance relative to theENVC
model.
Dry Deposition Monitoring Method inAlberta iv
TABLE OF CONTENTS
FOREWORD
i
SUMMARY
li
LIST OF TABLES vi
LIST OF FIGURES vii
1.0 INTRODUCTION 1
1.1 Objectives ofStudy 1
2.0 DRY DEPOSITION METHODS EVALUATION 3
2.1 Background on Inference Method 3
2.2 Methods Description 6
2.2.1 Alberta EnvironmentMethod 6
2.2.2 Environment CanadaMethod 6
2.2.3 WoodBuffalo EnvironmentalAssociation Method 7
2.3 Methods Assumptions 8
2.4 Results andDiscussion 13
2.4.1 ModelResults ]3
2.4.2 Comparison ofInferenceMethods 22
2.4.3 Relationships ofDryDepositionforSulphurandNitrogen
Species24
2.4.3.1 Ratio 24
2.4.3.2 Ratio 25
2.4.3.3 Ratio 26
2.4.3.4 Ratio 26
3.0 FINDINGS AND RECOMMENDATIONS 27
4.0 REFERENCES 29
Appendix 33
I
Appendix 40
II
Appendix 58
III
Dry Deposition Monitoring Method inAiberta v
LIST OF TABLES
Table 1. Species commonly measuredfordrydeposition usingthe inference
method 5
Table 2. Dry deposition model parameters forWoodBuffalo Environmental
Association Fort McKay airmonitoring station-AMS #1 -forthe
period 1 January 2003 to 31 December 2003 8
Table 3. Relative comparison ofselective features ofthree inference
methods forestimating dry deposition 23
Table 4 Ratio ofannual SO2 deposition to total sulphur species deposition
atWBEAFort McKay airmonitoring station during 2003 24
Table 5 Ratio ofannual NO2 deposition to total nitrogen species deposition
atWBEAFort McKay airmonitoring station during 2003 25
Table 6. Ratio ofannual SO2 deposition to total sulphur species deposition
atBeaverlodge, Alberta (afterWBK, 2008) 26
Table 7. Ratio ofannual NOx deposition to total nitrogen species deposition
atBeaverlodge, Alberta (afterWBK, 2008) 26
Dry Deposition Monitoring Method inAlberta vi