A high-resolution ammonia emission inventory in China
Xin Huang,1Yu Song,1Mengmeng Li,1Jianfeng Li,1Qing Huo,1Xuhui Cai,1Tong Zhu,1
Min Hu,1and Hongsheng Zhang2
Received11July2011;revid10November2011;accepted26January2012;published24March2012.
[1]The existence of gas-pha ammonia(NH3)in the atmosphere and its interaction
with other trace chemical species could have a substantial impact on tropospheric
chemistry and global climate change.China is a large agricultural country with an
enormous animal population,tremendous nitrogen fertilizer consumption and,
conquently,a large emission of NH3.Despite the importance of NH3in the global
nitrogen(N)cycle,considerable inaccuracies and uncertainty exist regarding its emission
in China.In this study,a comprehensive NH3emission inventory was compiled for
China on a1kmÂ1km grid,which is suitable for input to atmospheric models.We
attempted to estimate NH3emissions accurately by taking into consideration as many
native experiment results as possible and parameterizing the emission factors(EFs)by the
ambient temperature,soil acidity and other factors.The total NH3emission in China was approximately9.8Tg in2006.The emission sources considered included livestock excreta
(5.3Tg),fertilizer application(3.2Tg),agricultural soil(0.2Tg),nitrogen-fixing plants
(0.05Tg),crop residue compost(0.3Tg),biomass burning(0.1Tg),urine from rural
populations(0.2Tg),chemical industry(0.2Tg),waste disposal(0.1Tg)and traffic
(0.1Tg).The regions with the highest emission rates are located in Central and Southwest
China.Seasonally,the peak ammonia emissions occur in spring and summer.
Citation:Huang,X.,Y.Song,M.Li,J.Li,Q.Huo,X.Cai,T.Zhu,M.Hu,and H.Zhang(2012),A high-resolution ammonia emission inventory in China,Global Biogeochem.Cycles,26,GB1030,doi:10.1029/2011GB0
04161.
1.Introduction
[2]Ammonia(NH3)is a very important alkaline constit-uent in the atmosphere,and it has a wide variety of impacts.
A large part of atmospheric aerosols consist of sulfate neutralized to various extents by NH3.NH3is a key pre-cursor to the neutralization of HNO3and H2SO4in the atmosphere to form the condary inorganic aerosols (NH4)2SO4,NH4HSO4and NH4NO3,which contribute to ambient particulate matter[Seinfeld and Pandis,2006],as shown in following chemical reaction equations:
2NH3gðÞþH2SO4gðÞ⇌NH4
ðÞ2SO4sðÞð1ÞNH3gðÞþH2SO4gðÞ⇌NH4HSO4sðÞð2Þ
NH3gðÞþHNO3gðÞ⇌NH4NO3sðÞð3ÞMeasurements have indicated that the mass of condary sulfate,nitrate and ammonium could account for25–60%of the total PM2.5(fine particles in the ambient air,2.5m m or less in aerodynamic diameter)mass in China[He et al., 2001;Niu et al.,2006;Fang et al.,2009].Results from recent studies show that the fine particles can be depos-it
ed deep in the lungs,which may lead to incread mor-bidity[Dockery et al.,1993].Fine particles also can result in regional visibility degradation by light scattering[Ye et al.,2011].Global climate change due to ambient par-ticulate matter has gained increasing attention in recent years.The aerosol particles have a significant effect on radiative forcing by both direct scattering and the absorption of solar radiation and modification of the shortwave reflec-tive properties of clouds[Charlson et al.,1992;Martin et al.,2004],thereby exerting a cooling effect on the planet.In addition,NH3,as an important alkaline gas in the atmosphere,can react readily with acidic substances and neutralize the acidity of precipitation.Gaous ammonia and ammonium compounds in particles are eventually deposited to the soil or water bodies.NH4+deposited to the soil may either be taken up by plant roots or be subjected to nitrification yielding NO3À,as shown in following equa-tions.Both process result in proton relea into the soil [Krupa,2003].Conquently,ammonia emission is also known as one of the caus of soil acidification,eutrophi-cation and even the perturbation of ecosystems[Van Breemen et al.,1983;Pearson and Stewart,1993].
NH4þþ2O2→2HþþNO3ÀþH2Oð4Þ
1State Key Joint Laboratory of Environmental Simulation and Pollution
Control,Department of Environmental Science,Peking University,Beijing,
China.
2Laboratory for Atmosphere-Ocean Studies,Department of
Atmospheric and Oceanic Science,School of Physics,Peking University,
Beijing,China.
Copyright2012by the American Geophysical Union.
刚性屋面
0886-6236/12/2011GB004161
GLOBAL BIOGEOCHEMICAL CYCLES,VOL.26,GB1030,doi:10.1029/2011GB004161,2012
The most important ammonia emitters are livestock waste and fertilizer,which jointly contribute over57%globally and over80%in Asia[Zhao and Wang,1994;Bouwman et al.,1997;Streets et al.,2003].China is a country with den rural populations,and it has the world’s top-ranking agricultural production.Both of the factors contribute significantly to the global ammonia emissions budget.Pre-vious rearchers have demonstrated that approximately 14Tg NH3is relead in China annually,making it one of the most important emitters,with a contribution of20%to the global budget a
nd55%of Asian emissions.What is worth mentioning,global ammonia column was mapped bad on the obrvation of IASI nsor(Infrared Atmo-spheric Sounding Interferometer)onboard EUMETSAT’s Meteorological Operational Satellite(MetOp-A),which also demonstrated that China is an important emitter[Claris et al.,2009].
[3]There are veral ammonia inventories for China [Zhao and Wang,1994;Olivier et al.,1998;Xing and Zhu, 2000;Streets et al.,2003;Ohara et al.,2007].However, the inventories have weakness.First,they often u uniform and European-bad EFs for the entire country. Ammonia volatilization,especially from nitrogen fertilizer application and animal waste management systems,depend strongly on soil acidity and ambient temperature[Kirk and Nye,1991;European Environment Agency(EEA),2009]. The EFs should be parameterized by such factors.Second, not all ammonia emission sources are included during esti-mation,such as vehicle exhaust and wastewater treatment. This omission could introduce inaccuracies in the estimation of total emissions.Third,the prevailing inventories often have coar temporal and spatial resolutions.Agricultural activities such as fertilization and crop burning exhibit a-sonal variations due to planting and harvesting practices. Ammonia volatilization also strongly depends on the tem-perature,which fluctuates asonally.Hence,a temporal resolution of one year tends toward overestimation in winter and under
estimation in summer.Spatially,the existing inventories are mostly compiled at coar spatial resolutions, such as at the provincial level[Wang et al.,1997],at1 Â1 [Bouwman et al.,1997]and at a30minÂ30min grid [Streets et al.,2003].For a modeling study of the NH3cycle and air quality simulation,a more detailed inventory is preferred.
[4]A comparison of measured and predicted NH4NO3 concentrations also indicates that the existing inventories might be overestimated by approximately20–75%in East Asia[Kim et al.,2006].Therefore,an accurate ammonia emission inventory is needed to reflect various sources with a fine spatial and temporal resolution for China,especially for air environmental quality simulation.In this study,a comprehensive ammonia inventory for the year2006is developed.The sources of ammonia considered include the following:(1)farmland ecosystem(soil and nitrogen-fixing plant emission,fertilizer application and crop residue com-post),(2)livestock wastes(free-range,intensive and grazing rearing systems),(3)biomass burning(forest and grass fires,crop residue burning and fuel wood combustion), (4)excrement of rural populations;5)chemical indus-try(ammonia synthesis and nitrogen fertilizer production), (6)waste disposal(wastewater and solid waste treatment), and(7)traffic sources.The activity data are from province-specific statistical data ts,with the exception of a MODIS burned area product(MCD45A1),which was ud in the asssment of bio
包山楚简mass burning emissions.The EFs are characterized by asons and locations,in which the ammonia volatilization from nitrogen fertilizer and animal agriculture is parameterized by the ambient temperature, soil acidity and other crucial influential factors.
2.Data and Methods
[5]Ammonia emission is calculated as a product of activity data and corresponding EFs.The important sources and its activity data are listed in Table1,more detailed information could be found in Table S1in the auxiliary material.1
2.1.Farmland Ecosystem
[6]Farmland ecosystems are an important source of ammonia emission.The emitters include synthetic fertil-izer application,agricultural soil,nitrogen-fixing plants and the compost of crop residues.
2.1.1.Synthetic Fertilizer Application
[7]In China,a large agricultural country with intensive agricultural areas and conventional cultivation practices,N fertilizers are applied extensively,with more than20Tg of N fertilizers applied every year[
National Bureau of Statistics of China(NBSC),2008a].Recent studies have indicated that10–30%of applied N is lost though NH3volatilization [Ju et al.,2009].NH3volatilization depends substantially upon fertilizer types.In China,urea and ammonium bicar-bonate(ABC)are the two dominant N fertilizers,followed by ammonium nitrate(AN)and ammonium sulfate(AS).
Table1.Activity Data for Various Sources
Activity Data Set and Its Description Amount
Synthetic fertilizer application(synthetic fertilizer consumption)22.4Tg
Agriculture soil(cultivated areas) 1.2Â108hectare
Nitrogen-fixing crop(cultivated areas) 2.1Â107hectare
Compost of crop residues(mass composted)235Tg
Livestock wastes(animal population) 1.2Â1010
Biomass burning(burned biomass or burned area)411Tg burned biomass;2118km2burned area Excrement of rural population(rural population using tatty latrine) 2.6Â108
Chemical industry(production)49Tg synthetic ammonia;39Tg N nitrogen fertilizers Waste disposal(waste amount) 2.0Â1010m3wastewater;78Tg solid waste Traffic sources(vehicle population) 1.6Â108
1Auxiliary materials are available in the HTML.doi:10.1029/
2011GB004161.
Urea and ABC accounted for approximately69%and26%, respectively,of the total chemical N fertilizer consumption in2006[NBSC,2007c,2007e].Hence,the N fertilizers considered in our study are classified into five categories: urea,ABC,AN,AS and other(including calcium ammo-nium nitrate and ammonium phosphates).The loss rate strongly depends on numerous factors,including soil prop-erties(pH,calcium content,water content,buffer capacity and porosity),meteorological conditions(temperature,wind speed and precipitation),time of application in relation to a crop canopy and the method of application[Bouwman et al.,1997].如何树立文化自信
[8]In this study,ammonia emissions were estimated by multiplying consumption and gridded(1kmÂ1km)con-dition-specific EFs for five kinds of fertilizer as well as 16major plants.The rates of fertilizer consumption were obtained as the product of cultivated area and the applica-tion ra
te of plants.The plants to which considerable amounts of N fertilizers are applied include early rice,mi-late rice,late rice,non-glutinous rice,wheat,maize,bean, potato,peanut,oil crop,cotton,beet,sugarcane,tobacco, vegetables and fruits[NBSC,2007c,2007e].
[9]The type of fertilizer,the soil properties,the fertiliza-tion method,the application rate and temperature were introduced as parameters to develop EFs for specific condi-tions.For each kind of fertilizer,a reference emission factor (EF0),referring to existing native measurements,was adjusted by soil pH,application rate,temperature and fer-tilization method to develop a specific EF for a given scenario,as shown in following equation:
EF i¼EF0iÂCF pHÂCF rateÂCF TÂCF methodð5Þwhere EF i is the emission factor for a specific condition; EF0i is the reference emission factor for a type i N fertilizer; CF pH is the correction factor for different soil acidity;CF rate is the correction factor for different application rates;CF T is the correction factor for diver temperatures;and CF method is the correction factor for the fertilization method,includ-ing basal dressing and top dressing.The monthly and gridded EFs were developed considering all the factors. Ammonia emissions could then be calculated as the product of monthly fertilizer consumption and corresponding condition-specific EFs.
2.1.1.1.Fertilizer Type
[10]The potential ammonia emission from each fertilizer type often varies widely.ABC is a highly volatile compound that is extensively ud in China.The ammonia loss from the direct u of ABC could be up to30–40%of the applied N [Zhu et al.,1989].Urea,which is less volatile than ABC,is first converted to ammonium bicarbonate by the enzyme urea,which takes approximately2–3days in agricultural soil.Other N fertilizers,such as AN and AS,have a much lower ammonia emission potential(<10%of applied N) [Sutton et al.,1995;Van der Hoek,1998].The EF0for urea and ABC were bad on experiments carried out in Henan and Jiangsu Province through the micrometeorological method[Cai et al.,1986;Zhu et al.,1989].The EF0for other less prevalent fertilizers refers to the up-to-date and reliable EFs provided by the European Environment Agency[EEA, 2009],as shown in Table2.
2.1.1.2.Soil Property
[11]The volatilization of ammonia greatly depends on the soil properties,including bulk density,volumetric water content,CEC,soil acidity and urea activity.The results from the analysis of covariance demonstrate that the vola-tilization is most strongly correlated with pH[Li and Ma, 1993;Corstanje et al.,2008].Several publications have shown the disparity of ammonia volatilization from urea and ABC in different soils[Cai et al.,1986;Zhu et al.,1989]. For fertilizers such as AS,which
form sparingly soluble salts with calcium and thus increa the dissolution of calcium carbonate,the emission rate will be greater in the alkaline soil,whereas for AN,the emission rate is nearly unaffected by the soil pH.Several studies support that ammonia loss progressively increas with an increa in soil pH,and linear regression was ud to yield specific EFs in some studies[Whitehead and Raistrick,1991;Bouwman et al., 2002;Fan et al.,2005;Jones et al.,2007].In our study, linear interpolation method was ud to specify EFs by assuming that a linear relationship between ammonia vola-tilization and soil pH.A soil pH with a spatial resolution of1km in China was provided by the Harmonized World Soil Databa(available from www.iiasa.ac.at/ Rearch/LUC/External-World-soil-databa/HTML/).
2.1.1.
3.Application Rate
[12]The application rate was ud as a modifier for EFs for various types of fertilizers.Ju et al.[2009]reported an increa in ammonia emission with increasing application rate.Experiments on the relationship between application rate and ammonia volatilization are limited.Correction was done only when application rate is relatively high.A value of200kg N haÀ1was considered the high rate,an
d a value of1.18for CF rate was ud for a province with a high application rate[Li et al.,2002;Song et al.,2004;Fan et al.,2006].For regions where the rate was lower than 200kg N haÀ1,no correction was made.
2.1.1.4.Temperature
[13]As the partial pressure of NH3in solution increas exponentially with temperature,we would expect a strong relationship between temperature and ammonia emission. Several studies have noted an increa in emission from N fertilizers with increasing air temperature.EEA[2009]have summarized empirical volatilization rates as functions of
Table 2.EFs,Expresd as Percentage of Volatilized NH3-N From Applied Fertilizer-N,and Correction Coefficients for Different N Fertilizer Categories
Fertilizer Categories
Measured EFs Correction Coefficients Acid Soil Alkaline Soil CF rate a CF T b CF method c
Urea8.8d30.1d 1.180.350.32 ABC18.2e39.1e 1.180.440.32 AN0.8f0.8f 1.180.010.32 AS 2.3g 4.6g 1.180.060.32 Others0.8f0.8f 1.180.010.32 a Values are derived from Li et al.[2002],Song et al.
[2004],and Fan et al.[2006].
b Values are derived from Lu et al.[1980]and EEA[2009].
c Values are derive
d from Lu et al.[1980],Qu[1980],Fillery et al. [1986],Zhang and Zhu[1992],Li and Ma[1993],and Cai et al.[2002].
胎儿宫内发育迟缓d Measurement results of Zhu et al.[1989].
e Measurement results o
f Cai et al.[1986].
f Values recommended by EEA[2009].
g Measurement results of Qu[1980].
spring air temperature for various fertilizers except ABC.We derived a relationship of emission rate and temperature for ABC bad on the available native experimental data [Lu et al.,1980],as listed in
Table 2.Monthly average tem-peratures for a 1km grid were developed on the basis of NCEP (National Centers for Environmental Prediction)final analysis data t.
2.1.1.5.Fertilization Method
绿豆芽怎么炒
[14]The method of fertilization is another important factor affecting the volatilization of ammonia.We considered two common fertilization methods:basal dressing and top dressing.For the same fertilizer,the EF for basal dressing is approximately 32%of that for top dressing [Lu et al.,1980;Qu ,1980;Fillery et al.,1986;Zhang and Zhu ,1992;Li and Ma ,1993;Cai et al.,2002].The application time and amount of fertilizer ud as basal dressing and top dressing are referenced from the Chine planting information net-work (v/)and census data and inves-tigation results [NBSC ,2007a,2007e;Wang et al.,2008].2.1.2.Agriculture Soil
[15]Many organisms in soils are involved in the decom-position of organic matter excrete NH 3directly or N com-pounds which could be readily hydrolyzed to NH 3.The NH 3fluxes from soil are related cloly to the biological activity in the soil and other meteorological factors [Bouwman et al.,1997].There is limited information on ammonia emissions from cultures without fertilizers in China.Background emission levels of ammonia from agricultural soil were reviewed by Yan et al.[200
3],and an EF value of 1–2kg NH 3-N ha À1yr À1was recommended as the loss of ammonia in temperate regions.The province-level area of arable land refers to the census data [NBSC ,2007e].The provincial ammonia emission from agricultural soil was calculated as a product of arable land and EF.2.1.3.Nitrogen-Fixing Crop
[16]Nitrogen-fixing crops,even if not given fertilizer-N,have been estimated to fix as much N as fertilized crops.Thus,emissions of NH 3may be expected to be similar to tho from fertilized agricultural crops.The most widely cultivated nitrogen-fixing plants in China are beans (mostly soybean,accounting 77%cultivated area),peanuts and green
manure.The ammonia emissions may be approximately estimated as follows:
E NH 3¼∑A i ÂN
F i ÂEF NH 3ðÞ
ð6Þ
where E NH 3is the emitted NH 3from N-fixing crops;A i is the area covered by N-fixing crops i ;NF i is the nitrogen fixation rate of type i N-fixing crops;and EF NH 3is the ammonia EF for crops i.
[17]The province-level cultivated areas of the three nitrogen-fixing crop groups were provided by the National Bureau of Statistics of China [NBSC ,2006,2007e].The N fixation rates of the crops are 105,120and 130kg N/ha/yr,respectively [Kuenzler and Craig ,1986;Yan et al.,2003].Data on NH 3fluxes over legume crops are spar,but the 0.01kg NH 3/kg N suggested by EEA was ud in our estimation [EEA ,2006].
香芹炒牛肉2.1.4.Compost of Crop Residues
[18]Composting refers to the u of both aerobic and anaerobic microbial process to degrade waste materials for beneficial reu.In the rural China,crop straws and other agricultural residues are often composted to add soil nutrients.A large amount of ammonia is relead during this biological process.The ammonia emissions from this source are assd by multiplying the amount and the corresponding EFs.Provincial crop residue production can be estimated bad on crop production and production-to-residue ratios [Lal ,2005;NBSC ,2007e].The portion of crop residues for composting refers to an investigation covering most of the provinces in China [Gao and Ma ,2002].The ammonia EF for the composting operation is 0.32kg/ton [Stephen et al.,2004].
2.2.Livestock Wastes
[19]Nitrogen in animal excrement in the form of urea can rapidly hydrolyze to form ammonium carbonate and then volatilize as gaous ammonia.Early inventories of ammo-nia emission from livestock wastes were calculated as the product of livestock numbers and annual EFs per animal [Buijsman et al.,1987].More recent inventories have improved the single EFs per animal with specific EFs for the various phas of manure management,including animal housing,manure storage,manure spreading and the grazing stage [Pain et al.,1998;Zhang et al.,2010].Recently,the mass-flow approach has been widely ud at the national and global scale [Webb et al.,2006;Beun et al.,2008].Ammonia is emitted from a pool of ammoniacal nitrogen (TAN),which is not incread during manure management,but it is depleted by the loss though ammonia volatiliza-tion,leaching and other pathways during different stages.This approach enables the rapid estimation of the con-quences of abatement at the upstream stage on the ammonia loss at the downstream stage,which is more accurate than the previous methods [Webb and Mislbrook ,2004].
[20]Bad on the mass-flow methodology in the EEA ’s inventory guidebook [EEA ,2009],we analyzed the trans-formation and migration of nitrogen in the animal husbandry (Figure 1).The ammonia emissions from each stage of livestock manure management are affected by many factors,
such as species,gender,age,bodyweight,nitrogen content of the feed,housing structure,manure storage
system,
Figure 1.N flows in the manure management system and ammonia volatilization (TAN:ammoniacal nitrogen).
spreading technique,time spent outside or inside and meteorological conditions[Zhang et al.,2010].Although numerous experiments have been performed on ammonia emission during livesto
ck production,few measurements have been recorded in China.Conquently,China-specific EFs must be recalculated on the basis of the native practice of livestock production and environmental conditions. [21]In China,animals are raid in veral completely different systems,including free-range,intensive and grazing system.Ammonia emissions were calculated pa-rately for the three systems.The typical animal categories in China are listed in Table3.Gender and age are also taken into account in the definition of livestock subcategories. The available statistical data,official surveys(www. caaa/)and industry reports for husbandry were collected to obtain the number of each livestock class[Editorial Office of China Animal Industry Yearbook(EOCAIY), 2007].The annual excretions of TAN by each livestock class were derived bad on the rearing period[China Agricultural University(CAU),1997;Zhou et al.,2010], the daily amount of excrement[CAU,1997;Ministry of Environmental Protection of People’s Republic of China (MEPPRC),2001;K.Wang et al.,2009],the nitrogen content and the percent of TAN[CAU,1978;Webb and Mislbrook,2004;EEA,2009](Table3).In the following stepwi procedure of manure management,slurry and solid manures were calculated parately.Monthly emissions estimation was conducted bad on temperature-depended EFs(Table S2).We assumed that the animal population is same during every month of the whole year since the monthly fluctuation of meat productions is very small (www.caaa/).Monthly specific EFs were devel-oped using provincial monthly average temperature from NCEP final analysis data t.2.2.1.Housing
[22]Housing emission is related to the portion of excreta deposited inside buildings.Various livestock class have different fractions of time spent in buildings(Table S2). Emissions from different locations were calculated by mul-tiplying the amount of TAN and EFs.Ammonia volatiliza-tion from the housing stage depends on factors such as housing conditions,humidity,temperature and animal waste handling practices[Anderson et al.,2003].In our study,we characterized the EFs by flooring type,waste handling practice and temperature variations.Deep litter flooring is commonly ud in free-range and grazing systems,but solid flooring is widespread in intensive large-scale farming.The differences between the methods are summarized by Hutchings et al.[2001].The handling practice of waste in the housing stage has been surveyed in some provinces in China[Liu et al.,2008],and the EFs for slurry and solid were derived from previous studies[Webb and Mislbrook, 2004;Department for Environment,Food and Rural Affairs, 2005;EEA,2009].The temperature adjustment of the vola-tilization rate was accomplished though the diver EFs at different temperature intervals[Mannebeck and Oldenburg, 1991;Koerkamp et al.,1998].
2.2.2.Storage
[23]According to the actual treatment of housing waste in China,usually no treatment is given for the excrement deposited outside buildings,and tho excreted inside are usually ttled in two ways:bio
广州电网gas generation and com-posting.The handling practices of manure storage are dif-ferent in different parts of China.According to Liu et al.’s investigation,approximately10%more manure is ud to produce biogas in the Southern provinces in the free-range rearing system[Liu et al.,2008].Unfortunately,there is limited data on the fraction of different storage methods in
Table3.Parameters Ud in Estimates of Annual TAN Excretion per Animal for Each Livestock Class
Livestock Class Period a
(day)
Excrement b
(kg/day/cap)爱的奉献歌曲原唱
Nitrogen Contents c
(%)
TAN Content d
(%) Urine Faece Urine Faece
Beef<1year365 5.007.00.900.3860 Beef>1year36510.0020.00.900.3860 Dairy cows<1year365 5.007.00.900.3860 Dairy cows>1year36519.0040.00.900.3860 Goat<1year3650.66 1.5 1.350.7560 Goat>1year3650.75 2.6 1.350.7550 Sheep<1year3650.66 1.5 1.350.7560 Sheep>1year3650.75 2.6 1.350.7550 Sow365 5.70 2.10.400.3470 Weaner75 1.200.50.400.3470 Fattening pig75 3.20 1.50.400.3470 Hor365 6.5015.0 1.400.2060 Donkey365 6.5015.0 1.400.2060 Mule365 6.5015.0 1.400.2060 Camel365 6.5015.0 1.400.2060 Laying hen365-0.12- 1.6370 Laying duck365-0.13- 1.1070 Laying goo365-0.13-0.5570 Broilers50-0.09- 1.6370 Meat duck55-0.10- 1.1070 Meat goo70-0.10-0.5570
a Values are derived from CAU[1997]and Zhou et al.[2010].
b Values are derived from CAU[1997],MEPPRC[2001],and K.Wang et al.[2009].
c Values are derive
d from CAU[1978].
d Values ar
e derived from Webb and Mislbrook[2004]and EEA[2009].
