-
at SciVerse ScienceDirect
Atmospheric Environment 77 (2013) 725e737Contents lists
availableAtmospheric Environment
journal homepage: www.elsevier .com/locate/atmosenvFluoride and
sulfur dioxide indoor pollution situation and control
incoal-burning endemic area in Zhaotong, Yunnan, China
Yonglin Liu a,b, Kunli Luo a,*, Ling Li a,b, Muhammad Zeeshaan
Shahid b,c
a Institute of Geographic Sciences and Natural Resources
Research, Chinese Academy of Sciences, Beijing 100101,
ChinabUniversity of the Chinese Academy of Sciences, Beijing
100049, Chinac Institute of Atmospheric Physics, Chinese Academy of
Sciences, Beijing, Chinah i g h l i g h t s To provide the gaseous
F and SO2 pollution level in the coal-burning fluorosis areas.
Gaseous F and SO2 pollution in the baking room with open stoves is
serious. Use calcined dolomite instead of clay can reduce F and S
release greatly. It is a useful way to control gaseous F and SO2
pollution in the fluorosis areas.a r t i c l e i n f o
Article history:Received 7 November 2012Received in revised
form10 May 2013Accepted 17 May 2013
Keywords:Coal-burning endemic fluorosisGaseous fluoride and
sulfur dioxidepollution levelControl researchCalcined dolomitic
siliceous limestone* Corresponding author. Tel.: 86 10 64856503;
faxE-mail addresses: [email protected], liu3
[email protected] (K. Luo).
1352-2310/$ e see front matter 2013 Elsevier
Ltd.http://dx.doi.org/10.1016/j.atmosenv.2013.05.043a b s t r a c
t
The presented study aims to investigate the gaseous fluoride and
sulfur dioxide (SO2) pollution level in thekitchen, traditional
flue-curing barn and outdoor environment and to find economically
feasible methodto reduce fluorine and sulfur release. The gaseous
fluoride and SO2 concentrations in air of outdoorenvironment,
kitchen and traditional flue-curing barn were determined in 56
households in coal-burningendemic fluorosis areas of Zhaotong.
Among these, 21 households in Yujiawan Village, Zhenxiong
County,Zhaotong City were chosen for this experiment to reduce
gaseous fluoride and SO2 concentration intraditional flue-curing
barn air by using calcined dolomitic siliceous limestone (CDSL)
instead of claymixed with coal. The result showed that: (1) gaseous
fluoride and SO2 concentration in the outdoor air inMangbu Township
area was 0.51 mg dm2,day and
-
Table 1The parameters of the portable gas detector.
Parameter Range Parameter Range
Sucking rate ofaspiratorpump
300 ml min1 Operatingenvironment
Temperature: 10 Cto 45 CHumidity: 90% RH(non-condensing)
Detectingrange
0.02e200 ppm Span drift 5% (F.S)/4 h
Accuracy 5% (F.S) Zero drift 2% (F.S)/4 h
Table 2F and total S in the fine coal, clay, CDSL and coal
slime.
Elements No. S (%) F (mg kg1)
Fine coal MB4 2.94 124.5MB7 2.73 106.0MB39 2.11 99.8LD2 2.30
95.5LD5 2.10 115.8LD12 2.00 40.3
Clay MB33 0.14 1303MB35 0.03 178.0MB38 B.D 1214.0LD9 0.82
1181.0LD14 0.13 1663.0LD15 B.D 2422.0
CDSL MB 0.10 137.0LD 0.41 78.8
Coal slime MB3 2.10 161.0MB15 1.80 145.0MB31 1.80 157.0
Note: MB: Mangbu Town, Zhenxiong County, Zhaotong City; LD:
XiaolongdongTown, Zhaoyang District, Zhaotong City; B.D: Below
detection; CDSL: Calcineddolomitic siliceous limestone.
Y. Liu et al. / Atmospheric Environment 77 (2013)
725e737726gaseous fluoride, sulfur dioxide (SO2) and suspended
particles areemittedduring the coal burning (Andoet al.,1998;Dai et
al., 2004; Jinet al., 2006). Exposure to indoor air pollution from
the combustion ofcoal can causemany diseases including endemic
fluorosis, arseniasisand respiratory diseases (Liang et al., 1993a;
Ando et al., 1998;Finkelman et al., 1999; Jin et al., 2006; Zhang
and Smith, 2007). Theindoor gaseous fluoride pollution in
coal-burning endemic fluorosisareas in China have been studied in
many areas, such as LongliCounty (Ando et al., 1998, 2001; Dai et
al., 2004), Guiding County(Yanget al., 2010)
inGuizhouProvince,WushanCountyof ChongqingCity (Liang et al.,
1993b; Ando et al., 1998, 2001) and SouthernShaanxi (He et al.,
2005). Zhaotong City of Yunnan Province is thetypical coal-burning
endemicfluorosis area in China (Ye et al., 2004a,2004b, 2005a,
2005b; Sun, 2005; Cao, 2001; Luo et al., 2007, 2008).Liang et al.
(1993a) have reported the indoor and outdoor gaseousfluoride andSO2
pollution inXiaolongdongTownship, ZhaotongCity.25 gaseous fluoride
samples (46 mg m3) and 99 SO2 samples(1.72 mg m3) in the kitchen
were collected and measured. But thetypes of stove used by
households were not introduced and thegaseousfluoride andSO2
pollution level in the traditionalflue-curingbarn (baking room) was
not studied. Wang et al. (2001) have deter-mined 20 gaseous
fluoride samples (1.5 mg m3) in the kitchenwiththe improved coal
stove in Qinggangling Village, Qinggang Town-ship, Zhaotong City.
But there is no data available about the gaseousfluoride and SO2
concentration in the traditional flue-curing barn airwith the open
stove.
The fluoride (F) content in coal in Zhaotong City was 77mg
kg1
(Luo et al., 2007), that is similar to the Chinese average of
82mgkg1
(Luo et al., 2004; Ren et al., 2006), to the F average of 83 mg
kg1 inWestern Guizhou (Dai et al., 2004) and to the world average
of80 mg kg1 (Swaine, 1990). Therefore, the coal used by
householdsin Zhaotong City is the low-fluorine coal. The F sources
in endemicfluorosis area in Zhaotong City are the high fluorine
clay as an ad-ditive for coal-burning and as a binder for
briquette-making (Li et al.,1995; Luo et al., 2007, 2008). So, we
need to know the gaseousfluoride and SO2 concentrations caused by
low-fluorine coal (LFC)mixed with high-fluorine clay (HFCL) in
Zhaotong City.
Ando et al. (1998, 2001) indicated that direct
inhalationaccounted for 1.9e3.4% of total fluoride dose, 94.5e97.3%
of totalfluoride exposure was caused from dietary food consumption
andonly 0.8e2.1% of total fluoride dosewas caused
fromdrinkingwaterin the coal-burning fluorosis area in Longli
County of GuizhouProvince and Pengshui County of Chongqing
City.
Therefore, it is clear that the F sources in endemic fluorosis
areain Zhaotong City are the high fluorine clay as an additive for
coal-burning and as a binder for briquette-making (Li et al., 1995;
Luoet al., 2007, 2008). So, theoretically, if abandon the
high-fluorineclay (HFCL) as an additive for coal-burning and as a
binder forbriquette-making, the gaseous fluoride pollution in the
traditionalflue-curing barn would be reduced dramatically in
Zhaotong City.So, the gaseous fluoride and SO2 pollution levels in
the traditionalflue-curing barn need to be determined.
Zhaotong City is one of the main areas of middle and high
sulfur(S) coal producing area, and average S content of coal in
Zhaotong is2.36% (Table 2). So, in the coal-burning endemic
fluorosis areas, thesulfate SO42 and inorganic anions change to
acidic compoundsvery easily in the moisture containing atmosphere,
which is moreharmful to human respiratory system (Zhao, 1992; Liang
et al.,1993a; An et al., 1995; Yan, 1996). Liang et al. (1993a)
studied thatif high concentration of gaseous fluoride and SO2
coexisted in air, itwould exacerbate the endemic fluorosis. Thus
SO2 pollution levelalong with the fluorine pollution from coal
burning in coal-burningendemic fluorosis in Zhaotong also needs to
study.
The technology of fluorine and sulfur retention with
calcium-based materials in coal combustion had been studied in
differentyears (Cao, 1992; Zhang et al., 2002; Liu et al., 2006;
Yamada et al.,2008; Chen et al., 2009; Yang et al., 2010) and
satisfactory resultshad been achieved.
Coal briquette in previous study is all honeycomb briquettes.
Butin the rural area of Zhaotong City, local resident are more
perfect touse the briquette that is only mixture of clay and coal
together(Fig.A.1, Fig. 1), not shape up them as a special model
like thehoneycomb briquettes, to bake the corn and chili, or for
living used.
Domestic coal in Zhaotong is mainly crushed coal, accountingfor
more than 70% of coal yield, and the price is only 1/3e1/2 of
thelump coal. If the crushed coal is directly added into the coal
stove inthe practical operation, it can cut off from the air,
resulting in thefire to extinguish. Therefore, binder has to be
added into thecrushed coal.
There is abundant carbonate rock-dolomite, dolomitic
limestoneand limy dolomite in Zhaotong (Fig.A.2), which contain low
con-tents of fluorine (Luo et al., 2007). We try to use the local
lowfluorine calcined carbonate rock to instead of clay as a binder
forbriquette-making. Theoretically, if using the low fluorine
calcineddolomitic siliceous limestone (CDSL) instead of high
fluorine claymixed with coal, the gaseous fluoride and SO2
concentration in thetraditional flue-curing barn air would declined
markedly. So, weneed to know the both gaseous fluoride and SO2
concentrations inindoor air by low-fluorine coal (LFC) mixed with
low-fluorine cal-cium-based materials in Zhaotong City.
This studywill focus on the following problems: 1), what are
theindoor and outdoor gaseous fluoride and SO2 pollution level in
theendemic fluorosis areas in the improved stove used area in
Zhao-tong City. 2), what are the gaseous fluoride and SO2 pollution
levelin traditional flue-curing barn (baking room) by open stoves
tobake the corn and chili in Zhaotong City. 3), the gaseous
fluorideand SO2 concentration in the traditional flue-curing barn
in the
-
Fig. 1. The mode of baking corn and chili and building structure
of traditional flue-curing barn.
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e737
727households after use the calcined dolomitic siliceous
limestone(CDSL) instead of clay mixed with coal in Zhaotong
City.
1.1. Study areas
Zhaotong is the typical karst region (Fig.A.2) in the
Southwestarea of China. The major strata are Early and Later
Paleozoic strataand Early Mesozoic strata, which are thousands
meter carbonatedeposits (dolomite and limestone mainly). If this
natural carbonaterock can be utilized, it not only makes full use
of local materials, butalso reduces cost and secondary pollution in
the industrial Ca-based sorbent production process. The Ca-based
and Mg-basedmaterials are suitable for inconvenient traffic and
economic less-developed mountainous areas in the Southwestern area
of China.Fig. 2. Location map of the experimental sites. Note:
Administrative division of China is dCounty (District), Township,
Village (Administrative Village) and Natural Village
(group).Yujiawan Village (Fig. 2) is located in Mangbu Township,
about1 km northwest of Mangbu Town with average elevation 1625.8
m,mean annual temperature 10.8 C, annual rainfall 1388mmand
frost-free period more than 250 days. Xiaolongdong Township (Fig.
2) islocated in the eastern of Zhaoyang District, Zhaotong City,
about10.3 km from Zhaotong Urban Area. The elevation is from 1910 m
to3152 m. The annual temperature is 11 C and the annual rainfall
is750 mm. The frost-free period is more than 200 days. So, the
town-ship is a typical cold indigent area. Group 22 (Fig. 2) is
located in thesoutheast of Xiaolongdong Township, about 12 km from
the Xiao-longdong Town. In two severe endemic fluorosis areas in
Zhaotongthe improvedcoal stovewithchimney isused
forheatingandcookingfrom1990s. Thepopularization test on
reducingfluorine and sulfur influorosis areas was done in Yujiawan
Village, Zhaotong City.ivided into six government levels, that is,
Province, Prefecture-level city (Prefecture),
-
42
35
6
78
910
12
1113
1
1- colorimetric cylinder; 2-condensing tube; 3- high-temperature
combustion furnace; 4-silica boat; 5-quartz tube; 6-push rod;
7-water mouth;8-explosion-
proof ball; 9-distillation flask;10-temperature adjusting
slot;11-thermocouple;12-temperature controller;13-oxygen bottle
abc
Fig. 3. Combustion hydrolysis set to determine F content in
solid samples.
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e7377281.2.
The mode of cooking and heating and baking foodstuffs
In most households of coal-burning fluorosis area, including
thestudy households, fuels such as coal briquettes are burned
inimproved stove (with furnace cover and chimney leading out of
theroof) all day in the whole year for cooking and heating
(Fig.A.3).Some households use the open furnace for cooking and
heating.The corn and chili are usually baked by the open furnace
(Fig.A.1) inthe traditional flue-curing barn (Fig. 1). Meanwhile,
the study areais the indigent area in China. The study area is
typical karstmountain area and has a complicated landform and
physiognomy(Fig.A.2). The house structure is generally 2e3 m high
ranch housewith 3 rooms connecting to each other, and each room is
about 10e20 m2. Most of kitchen in many households are the
living-room.The kitchen in some households is not only the
living-room butalso the sleeping room. Even if the kitchen, the
living-room and thebedroom are not the same room, they usually
connect to each otherfor heating and saving energy. For the most
part, the traditionalflue-curing barn (baking room) in Zhaotong
City, Yunnan Provinceis separate and does not connect with other
rooms. In addition, thekitchen is closed and is used as temporary
traditional flue-curingbarn and it also does not connect with other
rooms in the harvestseason.
2. Experiment and analytical method
2.1. Sampling method of gaseous fluoride and SO2 in air
To determine gaseous fluoride in the air, lime-paper
sampling(LTP) was used (Li et al., 1989). Lime suspension liquidwas
preparedusing followingmethod: 56 g calcium oxidewasmixedwith
250mldistilled water in the 2000 ml beaker, meanwhile, slowly
adding250 ml of 72% perchloric acid under stirring. A mixed
solution washeated until white smoke emitting. After cooling, 200
ml distilledwater was added, and then mixture was heated until
white smokeemit. The whole procedure was repeated three times.
After cooling,mixture was filtered by glass sand funnel (G3). Then,
1000 ml of2.5 M sodium hydroxide solution was added to the filtrate
understirring. The solution was depositing, keeping static, dumping
su-pernatant into 5000mlvolumetricflask. Every time the
supernatantmust be dumped into 5000 ml volumetric flask. 1% calcium
hy-droxide suspension liquid was finished at last. Lime filter
paper wasprepared using following method: 12.5 cm qualitative
filter paperwas placed into the first glass culture dish with 1%
calcium hy-droxide suspension liquid. After soaking and draining
filter paper(calcium hydroxide suspension liquid must be replaced
afterimpregnating 5e6 pieces of filter paper), it was placed into
thesecond glass culture dish with 1% calcium hydroxide
suspensionliquid. Drained filter paper was spread on a big
qualitative filterpaper (cleanliness and no-fluoride). The
impregnated filter paperwasbakedat 60 C in electric dryingoven.
Thebakedfilterpaperwasplaced in a plastic sealed bag, and then it
was put into dry cabinet.
The method of hanging the lime filter paper in outdoor air is
asfollows: a piece of lime filter paper should be place on the
bottom ofthe sampling box and be fixed by the circlip. The sampling
box withfilter paper should be far away from the chimney of the
stove and isfastened above a fixed object, about 3.5w4 m away from
theground. The method of hanging the lime filter paper in indoor
was:a piece of lime filter paper should lie on the bottom of the
samplingbox and be fixed by the circlip (Fig.A.4). The sampling box
withfilter paper should be 1.5 m away from the stove and about 1.5
maway from the ground. Two pieces of lime filter paper should
befixed in every room. The surface of lime filter paper must
facedown. The top of sampling box should be covered, in order
toprevent fly ash from falling on the filter paper. The lime filter
papermust be exposed to air more than 7 days. When the sampling
boxwas collected, the lime filter paper was put into a plastic seal
bagimmediately. After that the lime filter paper should be put into
drycabinet in the lab. The determination of F content must be
finishedwithin 6 weeks. The specific sampling method may be
referred toMinistry of Environmental Protection of the Peoples
Republic ofChina (2003).
The method of sampling SO2: Because the temperature in
thetraditional flue-curing barn is very high, air sampler and
aspiratorpump would be damaged while SO2 is sampled by the method
offormaldehyde absorbing-pararosaniline spectrophotometry.
There-fore, the portable gasdetector
(BeijingXinhualaoScience&TradeCo.,Ltd) was used to determine
the indoor and outdoor SO2 concentra-tion. Table 1 is the
parameters of portable gas detector. In order toensure measurement
accuracy, zero correction and range correctionmust be done.
Zero correction:When the digital readout display is stable in
theclean air, it shows the value on the liquid crystal display
(LCD)screen is 000 through adjusting the zero potentiometer.
Rangecorrection: whether the show value returns to zero, the
digitalreadout display is stable in the clean air. The bag filled
up withstandard SO2 gasmust be connected to the instrument inlet
with anair duct, and dont adjust the potentiometer S until the
indicationvalue stays stable, then stop gas input when the value
shows nodifference with the sample concentration value. This
procedureshould be repeated once. If the difference between two
values iswithin error, the correction is finished. If the
difference exceeds theerror range, the corrective procedure should
be repeated. When theSO2 concentration is determined in situ, the
gas detector should be1 m away from the stove, about 1 m high from
the ground (Fig.A.5).Evacuation time must be more than 45 min.
Meanwhile, the tem-perature and pressure in situ should be
recorded.
2.2. Analytical methods
2.2.1. Analytical method of fluoride in airThe gaseous fluoride
content was determined by fluoride ion-
selective electrode (ISE) method. 0.1, 0.2, 0.4, 1.0, 2.0, 4.0,
8.0, 16.0and 40 mg ml1 of fluoride standards were prepared using
the100 mg ml1 of fluoride standard solution. The standard curve
wasdrawn by using semi logarithmic chart. Related coefficient of
theregression equation was greater than 0.999; Slope was within
the(54 0.2t) mv.
Determination of sample: The lime filter paper was cut insquares
of 5 mm by 5mm, and put into 100ml plastic beaker. 25 mlof total
ionic strength adjustment buffer (TISAB) and 25 ml ofdistilled
water were added into 100 ml plastic beaker. Mixture wascleaned 30
min in the ultrasonic cleaner. The 100 ml plastic beaker
-
Table 3Gaseous fluoride and SO2 concentration in outdoor air in
Yujiawan village, MangbuTownship and Group 22, Xiaomi Village.
Study areas Number ofsamples
Gaseous fluoride(mg dm2 day)(daily average)
SO2 (mg m3)(one-hour average)
Min Max Mean Min Max Mean
Yujiawan 9
-
Table 4Gaseous fluoride and SO2 concentration in the traditional
flue-curing barn air inZhaotong City.
Study areas Parameters Min Max Mean S.D Skew
Yujiawan F (mg m3) (daily average) 1.92 28.0 10.1 9.78 1.57SO2
(mg m3) (one-houraverage)
2.62 57.3 14.4 18.5 2.24
Group 22,XiaomiVillage
F (mg m3) (daily average) 1.21 20.7 7.2 7.54 1.40SO2 (mg m3)
(one-houraverage)
2.37 14.8 6.8 4.00 1.08
Note: S.D: standard deviation.
Y. Liu et al. / Atmospheric Environment 77 (2013)
725e7377302.3.2. Conversion formula of sulfur dioxideThe conversion
formula of sulfur dioxide is:
mg m3 M=22:4 ppm 273=273 T Ba=101325
M: Molecular weight of SO2 (64 g mol1); T: temperature
values(C); Ba: the values of atmospheric pressure (Pa).
2.4. Experimental methods for popularization test on
reducingfluorine and sulfur
The popularization test on reducing fluorine and sulfur
influorosis areas was done in Yujiawan Village, Zhaotong
City(Fig.A.2). First, dolomitic siliceous limestone near
experimentalvillages was calcined into powder (CDSL) in lime
factory, and thentransported to experimental households.
Experimental groups(EGs) (Fig.A.6) substituted local CDSL for clay
(Fig.A.7) mixed withlow-fluorine coal. The mixing ratio of CDSL to
coal was 3:7, namely,there had 30 kg CDSL and 70 kg coal in 100 kg
mixed fire coal(Fig.A.8). But the contrast groups (CGs) (Fig.A.1)
still did cookingand baked the food with the traditional mixed fire
coal-low-fluorine coal mixed with high-fluorine clay.
3. Results and analysis
3.1. Fluoride and total S content in solid
F and total S content in fine coal, coal slime (coal slime: it
is theresidue through coal washing technology), clay and CDSL are
listed(Table 2). The Table 2 shows that the F content in fine coal
ismaximum of 124.5 mg kg1, with average of 96.9 mg kg1, which
isslightly higher than the Chinese average of 82 mg kg1 (Luo et
al.,2004). And the F content in clay (Fig.A.7) is maximum of2422 mg
kg1, with average of 1327 mg kg1, which is close to thatFig. 5. The
gaseous fluoride (a) and SO2 (b) concentration in the trad(1516 mg
kg1) in clay reported by Luo et al. (2007). So, thehouseholds use
the LFC mixed with HFCL as their domestic energyfor cooking,
heating and baking foodstuffs.
On the basis of classification for coal quality (GAQS and
IQPRC,2004), total S content in the middle and high S coal is
1.5e3.0%,high S coal with>3.0% and low S coal with
-
Fig. 6. Comparison of experimental results between in Guiding,
Guizhou Province (GG) and in Zhaotong City, Yunnan Province.
Table 5F content (mg kg1) in fresh and roasted corn in 2010.
Study areas Sampleproperties
Fresh Baked(in EGs)
Baked(in CGs)
Yujiawan, MangbuTown
Corn 1.1 5.1 10.2Chili 0.8 9.0 35.2
Group 22, XiaomiVillage
Corn 1.7 4.7 10.5Chili 2.5 43.7 144.1
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e737 731et
al., 2001; Ye et al., 2004b). Therefore, through determining
thegaseous fluoride and SO2 pollution level before and
afterimprovement, the fluorine and sulfur removal effect (Fig.4) of
theimproved coal stove was studied.
Daily average of gaseous fluoride concentration in the
kitchenwith open furnacewas 11.5 mgm3 (Fig.4(a)) (reference value
(Lianget al., 1992) is 10 mgm3). One-hour average of SO2
concentration inthe kitchen with open furnace was 14.8 mg m3
(Fig.4(b)) that wasmuch higher than indoor SO2 standard (0.5 mg
m3). Afterimproving the stove, the daily average of gaseous
fluoride concen-tration in the kitchenwith improved coal stovewas
3.7 mgm3, withone-hour average of SO2 concentration of 0.94 mg m3.
Comparingbefore and after improvement, the average value of
gaseousfluorideconcentration in the kitchen air was decreased by
68.3% and waswithin the reference value (10 mgm3) (Fig. 4(a)). The
average valueof SO2 concentration in the kitchen air was decreased
by 93.7% andwas still higher than the standard value (0.5 mg m3)
(Fig.4(b)).Although the SO2 concentration in the kitchen air had
decreasedmarkedly, the SO2 concentration in the kitchen with
improved coalstove was still higher than the indoor air standard
(0.5 mg m3).Hence, decreasing the SO2 concentration in indoor
airmust be comeinto notice. From the above, the improved coal stove
with chimneygreatly improved the indoor and outdoor air
quality.
3.4. The gaseous fluoride and SO2 pollution in the traditional
flue-curing barn
The time for hanging lime filter paper in the traditional
flue-curing barn was from October 30th or 31st, 2010 to
November8th, 2010 in Yujiawan Village, Zhenxiong County. The time
wasfrom November 19th or 20th, 2010 to December 3rd or 4th, 2010
inGroup 22, Xiaomi Village, Zhaoyang District. The exposed time
oflime filter paper exceeded 7 days.
For the most part, the traditional flue-curing barn (Fig.1) in
Zhao-tong City, Yunnan Province is separate and do not connect with
otherrooms. But hitherto, there is no report on gaseous fluoride
and sulfurdioxide indoor pollution level in the traditional
flue-curing barn.
Table 4 showed that gaseous fluoride and SO2 indoor pollutionin
the traditional flue-curing barnwas very serious. So, the
gaseousfluoride, SO2 and other harmful elements polluted the corn
andchili in the traditional flue-curing barn. Luo et al. (2011)
have alsoinvestigated the stove-improving effects in Zhenxiong
County,Zhaotong City, Yunnan Province in 2011 and again indicated
thatthe dental fluorosis (Fig.A.9) rate of childrenwas still high
(82.7%) inthe coal-burning fluorosis areas in Zhaotong City after
improvingthe stove. The main reason is that the residents use open
furnace tobake corn and chili in the traditional flue-curing barn
in the harvestseason.Consequently, in order to solve the
coal-burning endemic fluo-rosis in Zhaotong areas radically, the
gaseous fluoride, SO2 andother toxic substance pollution in the
traditional flue-curing barnmust be reduced dramatically.
4. Effectiveness evaluation for reducing fluorine and sulfur
4.1. Study areas
There are 150 total households and 673 total populations
inYujiawan Village (elevation of 1600 m), Zhenxiong County and
80total households and 280 total populations in Group 22 (elevation
of2076 m), Xiaomi Village, Zhaoyang District. The area is the
seriousfluorosis areas (Ye et al., 2004a, 2005a, 2005b). There are
21 experi-mental groups (EGs) and19contrast groups (CGs)
inYujiawanVillage,Zhenxiong County. The experimental time which was
the harvestseason of corn is from October 20th, 2010 to December
6th, 2010.
4.2. The F and SO2 pollution in the traditional flue-curing
barn
Fig.5(a) shows that the F release has been decreased
aftersubstituting CDSL for clay mixed with coal in Yujiawan
Village,Zhenxiong County. The gaseous fluoride concentration (5.5
mgm3)in the traditional flue-curing barn air in EGs in Yujiawan
Village is45.27% less than that (10.1 mg m3) in CGs. It proved that
thegaseous fluoride pollution in the traditional flue-curing barn
hadbeen reduced markedly. The SO2 concentration (1.3 mg m3) in
thetraditional flue-curing barn air (Fig.5(b)) in EGs in Yujiawan
Villageis 91% less than that (14.4 mg m3) in CGs.
Comparison of experimental results between in Guiding
County,Guizhou Province (Yang et al., 2010) and in Zhaotong City,
YunnanProvince (Fig.6), the indoor gaseous fluoride
concentration(1.4 mg m3) in EGs in Guiding County, Guizhou Province
was lowerthan that (5.5 mg m3) in the traditional flue-curing barn
in Yujia-wan Village, Zhaotong City (Fig.6(a)). The indoor SO2
concentration(0.17 mg m3) in EGs in Guiding County, Guizhou
Province waslower than that (1.3 mg m3) in the traditional
flue-curing barn inYujiawan Village, Zhaotong City (Fig.6(a)). The
indoor gaseousfluoride (3.6 mg m3) concentration in CGs in Guiding
County,
-
Fig. 7. The F content in the baked corn (A) and chili (B) of
2009 and 2010 in fluorosis area.
Y. Liu et al. / Atmospheric Environment 77 (2013)
725e737732Guizhou Province was lower than that in the traditional
flue-curingbarn air in Yujiawan Village, Zhaotong City (10.1 mg m3)
(Fig.6(b)),and SO2 (0.45 mg m3) concentration was also lower than
that inYujiawan Village, Zhaotong City (14.4 mg m3) (Fig.6(b)). The
Fcontent in the bitumite, anthracite, clay and lime in Guiding
County,Guizhou Province was 2170 mg kg1, 231 mg kg, 2098 mg kg1
and850 mg kg1, respectively (Yang et al., 2010). The F content in
finecoal, coal slime, clay and CDSL in Zhaotong City, Yunnan
Provincewas 91 mg kg1, 154 mg kg1, 1327 mg kg1 and 108 mg
kg1,respectively. The reason for this difference was different
ventilatedconditions. All houses in Guiding County, Guizhou
Province had anattic above the cooking/living and sleeping rooms,
used for fooddrying and storage (He et al., 2005; Yang et al.,
2010). So, there wasno separate traditional flue-curing barn in
Guiding County, GuizhouProvince. Therefore, the indoor ventilation
in Guiding County,Guizhou Province was very well and that was
beneficial to gaseousfluoride and SO2 dispersion. But the
traditional flue-curing barn inZhaotong City, especially in Mangbu
Township, Zhenxiong County,was separate and did not connect with
other rooms, and the vol-ume of traditional flue-curing barn was
small (9e18 m3). So, thebuilding structure of flue-curing barn was
not beneficial to gaseousfluoride and SO2 dispersion. It is clear
that the gaseous fluoride andSO2 pollution in the traditional barn
in Zhaotong City had greatinfluence on F and S content in corn and
chili (Table 5; Fig. 8).
4.3. Fluoride and sulfur content in baked foodstuffs
Table 5 shows F content in corn and chili. The F content
inroasted corn and chili in the CGs using clay as binder was 2e4
timesFig. 8. The S content in the baked corn andhigher than that of
EGs using CDSL as binder. Luo et al. (2010) re-ported that the F
content (3.0 mg kg1) in the roasted corn inMuxuan Township,
Zhaotong City which was the non-fluorosis areawas higher than the
permitted level of fluoride content in foods(1.5 mg kg1) (NSPRC,
1984). But there was not dental and skeletalfluorosis. Luo et al.
(2010) made the safety line (less than4.0 mg kg1) of fluoride
content in roasted corn in coal-burningfluorosis areas. The F
content (Table 5) in corn baked by coalmixed with CDSL was close to
the safe line of 4 mg kg1 (Luo et al.,2010). The F content (Table
5) in chili baked by coal mixed withCDSL was still much higher than
the safe line of 4 mg kg1, butsignificantly lower than that of CGs
using clay as binder. Therefore,the gaseous fluoride pollution in
the traditional flue-curing barnwas reduced markedly after CDSL
instead of clay as binder.
Local residents in the fluorosis areas in Zhaotong largely eat
thebaked corn and chili of last year before harvesting fresh corn
andchili. Fig. 7 showed that the F content in the baked corn of
2009 wasobviously higher than that of 2010 (Fig.7(A)). But the F
content inthe baked chili of 2009 had no significant difference as
comparedwith that of 2010 (Fig.7(B)).
Sulfur (S) that constitutes the cell protein, tissuefluid,
andvariousimportant component of coenzyme is an essential human
chemicalelement. But excessive intake of Swould increases lipid
peroxidationand may cause damage to the visual system (Parcell,
2002; Ozturket al., 2011). Fig. 8 showed S content in corn and
chili. The S con-tent (Fig. 8) in roasted corn (mean: 0.28 102) and
chili (mean:0.45 102) in the CGs using clay as binder was much
higher thanfresh corn (mean: 0.14 102) and fresh chili (mean: 0.4
102).The mixture of clay and middle and high sulfur coal, which
ischili of 2009 and 2010 in fluorosis area.
-
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e737
733produced by localmines, is used as amain household energy to
bakethe foodstuffs. Because of this traditional baking method, the
cornand chili are contaminated by the SO2 emitted during the
coalburning. The S content (Fig. 8) in roasted corn (mean: 0.14
102)and chili (mean: 0.35 102) in the EGs using CDSL as binder
wasmuch lower than roasted corn (mean: 0.28 102) and roasted
chili(mean: 0.45 102) in the CGs using clay as binder, and they
wasequivalent to the S content in fresh corn and fresh chili.
Therefore, theSO2 pollution in the traditional flue-curing barn was
reduced mark-edly after CDSL instead of clay as binder.
The S content in the baked corn (mean: 0.34 102) and chili(mean:
0.6 102) of 2009 was higher than that in the baked corn(mean: 0.28
102) and chili (mean: 0.45 102) of 2010. As thegrain is stored with
long time, the corn and chili continue to adsorbthe sulfide emitted
during the coal burning.
5. Conclusions
Based on the systematic study of the gaseous fluoride and
SO2pollution level in outdoor environment, the kitchen and
thetraditional flue-curing barn, as well as the experiment for
fluorineand sulfur retention, main conclusions in this study have
beensummarized as follows:
1) Meanvalueof gaseousfluoride inoutdoor air
inYujiawanVillage,Zhenxiong County (0.51 mg dm2 day) and in Group
22, XiaomiVillage, ZhaoyangDistrict (2.7 mg dm2 day)was both lower
thanthe ambient air quality standard (3 mg dm2 day). But
somewerehigher than the ambient air standard. So, to some extent,
theoutdoor air was polluted by fluoride emitted by
coal-burning.
2) The households in Zhaotong City use LFC mixed HFCL as
do-mestic energy. By comparing before and after improving
coalstove, the gaseousfluoride and SO2 concentration in the
kitchenair has been declined markedly. The gaseous fluoride
concen-tration (3.7 mg m3) in the kitchen air is much lower
thanambient air quality (7 mg m3) and reference value (10 mg
m3).Although the SO2 concentration in the kitchen air has
decreasedFig. A.1. Corns and chilies (corns are placed in the
attic) are baked by the mixmarkedly, it is still higher (0.94mgm3)
than indoor SO2 qualitystandard (0.5 mg m3). So, reducing the SO2
pollution in thekitchen with improved coal stove is main direction
from nowon. The epidemiological survey should be carried out.
3) Based on the above explained experiments for fluorine
andsulfur reducing, the indoor gaseous fluoride and SO2 pollutionin
traditional flue-curing barn have obvious decrease afterCDSL
instead of clay as binder. Therefore, the food adsorptioncapacity
to fluorine and sulfur is reduced.
4) The mean fluorine content in clay is 1327 mg kg1, yet in
theCDSL is less than 100 mg kg1, which suggests that the
overallfluorine content in the system of coal plus 30% of this
lowfluorine CDSL is far less than that in coal with ordinary
clay.Therefore, abandoning the hundreds of years traditional wayof
mixed clay with coal will make the gaseous fluoride con-centration
in indoor air greatly reduced.
The cost of adding calcined dolomitic siliceous limestoneinstead
of clay as a binder for briquette-making.
The calcined dolomitic siliceous limestone has some
cohesive-ness and can be used as a binder for fine coal burning in
ZhaotongCity. The calcined dolomitic siliceous limestone in the
residentialcoal combustion is not only a binder, but also
sulfur-fixing agent andcombustion improver. If the calcined
dolomitic siliceous limestoneis added into the residential coal
combustion, the cost of 1000 kgcoal will increase 5e10 (1e2 US$)
Yuan (RMB). Also, about 4000 kgcoals are burned every year by
people living in fluorosis area inSoutheast China for baking food,
half of them are lump coal, whoseprice is twice of fine coal, 100
Yuan (RMB) (14 US $) more than finecoal. Thus, increased cost of
the briquettes is offset by using less orno lump coal. Actually,
the cost of baking foodstuffs does not in-crease by using the
calcined dolomitic siliceous limestone.
This method is simple, and drawing the carbonate material
inlocal is very easy, but let local people substitute the calcined
car-bonate for the clay, which added in the coal for hundreds of
years isnot easy. Therefore, the promotion of this method needs
time anddepends on the vigorous propaganda and support of
government.ture of coal and clay, and improved coal stove is
treated as open furnace.
-
Fig. A.3. Edibility method of baked corn.
Fig. A.2. Carbonate rocks widely distributing in coal-burning
endemic fluorosis area in Zhaotong.
Fig. A.4. Sampling method of indoor gaseous fluoride.
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e737734
-
Fig. A.6. Corn and chili are baked by the mixture of coal and
calcined dolomitic siliceous limestone.
Fig. A.5. Sampling method of indoor SO2.
Fig. A.7. The outcrop of fire-resistant clay around Group 22 in
Xiaolongdong Township.
Y. Liu et al. / Atmospheric Environment 77 (2013) 725e737
735
-
Fig. A.8. The mixture of coal and calcined dolomitic siliceous
limestone in the EGs.
Fig. A.9. A child suffering dental fluorosis in Yuqing Village
in Zhenxiong County(10 years old).
Y. Liu et al. / Atmospheric Environment 77 (2013)
725e737736Acknowledgments
This work is supported by the National High-Tech R&D
Program(863 Program) (Nos. 2004AA601080 and 2006AA06Z380) and
Na-tional Natural Science Foundation of China (No.
40872210,41172310). Special thanks are given to Science and
TechnologyBureau of Zhaotong and local personnel for their support
in sam-pling and collection of clay, calcined dolomitic siliceous
limestoneand coal samples. We thank Dr. Huijie Li for their
selfless help insampling. Many thanks are also given to Dr. Yongxin
Xu and Ms.Wulan Tan for their help in the fluorine and sulfur
determinations.Thank Ms Yuling Zhang for crushing samples.
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Fluoride and sulfur dioxide indoor pollution situation and
control in coal-burning endemic area in Zhaotong, Yunnan, China1
Introduction1.1 Study areas1.2 The mode of cooking and heating and
baking foodstuffs
2 Experiment and analytical method2.1 Sampling method of gaseous
fluoride and SO2 in air2.2 Analytical methods2.2.1 Analytical
method of fluoride in air2.2.2 Analytical method of solid
sample
2.3 Method of calculation2.3.1 Calculation formula of
fluoride2.3.2 Conversion formula of sulfur dioxide
2.4 Experimental methods for popularization test on reducing
fluorine and sulfur
3 Results and analysis3.1 Fluoride and total S content in
solid3.2 The outdoor gaseous fluoride and SO2 pollution3.3 The
gaseous fluoride and SO2 pollution in the kitchen3.4 The gaseous
fluoride and SO2 pollution in the traditional flue-curing barn
4 Effectiveness evaluation for reducing fluorine and sulfur4.1
Study areas4.2 The F and SO2 pollution in the traditional
flue-curing barn4.3 Fluoride and sulfur content in baked
foodstuffs
5 ConclusionsAcknowledgmentsReferences