Symbol Description of data Data type Unit Statistical distribution Mean Standard deviation SD Value References SD/mean % References S pond HN Area of fish ponds in Hanoi Certain km 2 Norm
Trang 1a Hanoi University of Science (HUS), Vietnam National University, No 19, Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam
b Institute of Chemistry, Vietnam Academy of Science and Technology (VAST), A18 – No 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam
c International Research Centre for River Basin Environment (ICRE), University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan
a r t i c l e i n f o
Article history:
Received 26 September 2013
Received in revised form 19 April 2014
Accepted 22 April 2014
Keywords:
Nutrient
Material flow analysis (MFA)
Monte Carlo simulation
Uncertainty
Reassessment procedure
a b s t r a c t
NitrogenflowsimpactedbyhumanactivitiesintheDay-NhueRiverBasininnorthernVietnamhave beenmodeledusingadaptedmaterialflowanalysis(MFA).Thisstudyintroducesamodifieduncertainty analysisprocedureanditsimportanceinMFA.WegeneratedaprobabilitydistributionusingaMonte Carlosimulation,calculatedthenitrogenbudgetforeachprocessandthenevaluatedtheplausibility underthreedifferentcriterionsets.Thethirdcriterion,withonestandarddeviationofthebudgetvalue
astheconfidenceintervaland68%astheconfidencelevel,couldbeappliedtoeffectivelyidentifyhidden uncertaintiesintheMFAsystem.Sensitivityanalysiswasconductedforrevisingparameters,followedby thereassessmentofthemodelstructurebyrevisingequationsorflowregime,ifnecessary.Thenumber
ofprocessesthatpassedtheplausibilitytestincreasedfromfivetonineafterreassessmentofmodel uncertaintywithagreatermodelquality.Theapplicationoftheuncertaintyanalysisapproachtothiscase studyrevealedthatthereassessmentofequationsintheaquacultureprocesslargelychangedtheresults fornitrogenflowstoenvironments.Thesignificantdifferenceswereidentifiedasincreasednitrogenload
totheatmosphereandtosoil/groundwater(17%and41%,respectively),anda58%decreaseinnitrogen loadtosurfacewater.Thus,modifieduncertaintyanalysiswasconsideredtobeanimportantscreening systemforensuringqualityofMFAmodeling
©2014ElsevierB.V.Allrightsreserved
1 Introduction
Huijbregts,1998;Radwanetal.,2004;Antikainen,2007).Eachof
∗ Corresponding author Tel.: +81 55 220 8593.
E-mail addresses: dothu nga2005@yahoo.com (N.T Do), ducta@ich.vast.ac.vn
(D.A Trinh), nishida@yamanashi.ac.jp (K Nishida).
(2012)addressedresourcemanagementandenvironmentalissues
etal.(2004)stressedtheimportanceofandneedforinvestigating
http://dx.doi.org/10.1016/j.resconrec.2014.04.006
0921-3449/© 2014 Elsevier B.V All rights reserved.
Trang 2Viet-nam(Do-Thuetal.,2011).Importanceofuncertaintyanalysisin
1992;Hekkertetal.,2000;LassenandHansen,2000).When
2 Methodology
beendoneintheDNRB(MOC,2009;MONRE,2006);thesewere
(BrunnerandRechberger,2004).Modelequationsconsistedofthe
Trang 3Table 1
List of parameters directly used in aquaculture process.
Symbol Description of data Data type Unit Statistical distribution Mean Standard deviation (SD)
Value References SD/mean (%) References
S pond HN Area of fish ponds in Hanoi Certain km 2 Normal 129.56 GSO (2008) 10 Authors’
assumptions
S pond HNa Area of fish ponds in Ha
Nam
assumptions
S pond ND Area of fish ponds in Nam
Dinh
assumptions
S pond NB Area of fish ponds in Ninh
Binh
assumptions
S pond HB Area of fish ponds in Hoa
Binh
assumptions
assumptions
assumptions
assumptions
assumptions
assumptions
aN man pond Nitrogen load in manure
supplied for fish pond per
time preparation
(2008)
966 b MARD (2008)
obser-vation and interview local farmers
observation and interview local farmers
(2000)
13 OSPAR (2000)
CN fish feed Nitrogen content in
commercial food for fish
(2000)
17 OSPAR (2000)
Fd pond Frequency of sludge
removals
obser-vation and interview local farmers
assumptions
rN SL fish Nitrogen accumulated in
fish pond sludge
(2000)
50 OSPAR (2000)
rN emis pond Percentage of nitrogen
release from aquaculture
system
(2007)
17 Schaffner
(2007)
(2000)
10 OSPAR (2000)
sludge removal
(2000)
5 OSPAR (2000)
a Minimum values of the uniform distribution.
b Maximum values of the uniform distribution.
Montangero and Belevi (2008) primarily proposed
Trang 4Fig 1.Material flow analysis (MFA) system for the Day–Nhue River basin Dashed lines represent new nitrogen flows added after field observations Note: livestock process (12) contains pig process (12a), poultry process (12b) and cattle process (12c) processes; field crop process (14) contains paddy (14a) and vegetable–fruit (14b).
Montangeroetal.(2007)assumedthatapopulation’sstandard
(2011)showedthatthebudgetvalueofthehouseholdprocess
Checking impact of parameters
No equation reassessment is possibl e
No pa rameter reasses sment is possibl e
No flow reassessment is possible
Input data
Fail Pass
Running Monte Carlo simulatio n
MFA results Running Monte Carlo simulatio n
Trang 5Table 2
List of detailed balance equations and model equations for aquaculture process before and after model revision.
Nitrogen flow Equation (Unit: tN/year)
dMN(13)/dt =AN2–13 + AN3–13 + AN6–13 + AN12–13 + AN15–13 + AN17–13 − AN13–6 − AN13–14 − AN13–15 − AN13–16 − AN13–17
Input
AN2–13 See Onsite sanitation (2)
AN6–13 =Y fish × rFC × CN fish feed × 10 −2
AN12a–13 =aN man pond × S pond × Fd pond × 10−3
AN15–13 =S pond × D pond × (1 + ET/P) × CN river
AN17–13 =S pond × P × CN rain × 10 −3
Output
AN13–14 =(AN2–13 + AN6–13 + AN12–13 – AN13–6) × rN SL fish × Fd pond
AN13–15 =(AN6–13 − AN13–6) × (1 − e)
AN13–15 a =(AN2–13 + AN6–13 + AN12–13 − AN13–6) × (1 – rN SL fish × Fd pond – rN leach paddy – rN emis pond)
AN13–16 a =(AN2–13 + AN6–13 + AN12–13–AN13–6) × rN leach paddy
AN13–17 a =(AN2–13 + AN6–13 + AN12–13 – AN13–6) × rN emis pond
S pond =S pond HN + S pond HNa + S pond ND + S pond NB + S pond HB
Y fish =Y fi HN + Y fi HNa + Y fi ND + Y fi NB + Y fi HB
a Equation after reassessment.
newlyproposedandcomparedwiththepreviouslyproposed
one
InMFA,outputwastraditionallyestimatedonthebasisof
input,asshowninTable2(AN13–16andAN13–17),butoutput
inDo-Thuetal.(2011).Therefore,itwasnecessarytoassessthe
et al.(2007),correspondedtoonestandarddeviationofthe
Belevi,2008).Herein,thesensitivity analysiswasappliedto
3 Results
Table3showspassratesforallprocessesbeforeandafter
naturally
Trang 6Table 3
Results of the plausibility test for all processes: percentages of the estimated budget within confidence intervals (pass rate) before (a) and after (b) reassessment.
Notes: Criteria 1, 2 and 3 represent three different criterion sets, where confidence intervals were ± 15% of total input, ± 15% of averaged input and output and ± one standard deviation of the budget, respectively The confidence level was 68% in all cases Pass rates of processes greater than 68% are indicated in bold.
Fig.3andTable3showprobabilitydistributionsofthe
AscanbeseeninTable3,thepigprocesshadtobereassessed
Fig 3.Results of the plausibility test for drainage process and solid waste collection process after all model revisions The values between broken lines represent confidence
Trang 7AN13–16andAN13–17wouldberevisedasdescribedinTable2
test
Fig 4. Nitrogen load to the environment (t/year) in four model versions White,
gray and black bars represent nitrogen loads to the atmosphere, surface water and
soil/groundwater, respectively Version 1 shows results before reassessment;
Ver-sion 2.1 includes the revised parameters for both pig and poultry processes; Version
2.2 includes the revised equations for aquaculture process; Version 2.3 includes the
4 Discussion
Trang 8Radwanetal.(2004)concludedthatmodelinputneededthe
forNO3–N.Schaffneretal.(2009,2010a,b)appliedadaptedMFA
(2009,2010a,b),Fig.4demonstratesthatequationreassessment
5 Conclusions and recommendations
Acknowledgements
Appendix A Supplementary data
2014.04.006
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