Concentration profile of elemental and organic carbon

Air Quality, Atmosphere & Health https://doi.org/10.1007/s11869-017-0539-z

Concentration profile of elemental and organic carbon and personal exposure to other pollutants from brick kilns in Durango, Mexico Abraham Ortínez-Alvarez 1,2 & Oscar Peralta 2 & Harry Alvarez-Ospina 3 & Amparo Martínez-Arroyo 1 & Telma Castro 2 & Víctor H. Páramo 1 & Luis Gerardo Ruiz-Suárez 1,2 & Jorge Garza 4 & Isabel Saavedra 2 & María de la Luz Espinosa 1 & Andrea De Vizcaya-Ruiz 5 & Arturo Gavilan 1 & Roberto Basaldud 1 & José Luis Munguía-Guillén 6 Received: 15 June 2017 / Accepted: 11 December 2017 # Springer Science+Business Media B.V., part of Springer Nature 2017

Abstract Emission factors and personal exposure measurements were obtained in the working environment of a brick kiln yard in the municipality of Victoria de Durango, Mexico. Two kinds of kiln were evaluated; one was a fixed traditional kiln (FTK); the other was a local variation of an improved kiln called the ecological Marquez brick kiln (MK2). To distinguish it from the original design, we call it the Marquez kiln Durango (MKD). Ambient emission gases of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and non-methane hydrocarbons (NMHC) were continuously followed using Fourier transform infrared spectrophotometry (FTIR). Elemental carbon (EC) and organic carbon (OC) ambient emissions were sampled on quartz filters and analyzed by chemical coulombimetry. Personal exposure to CO was continuously followed using portable monitors, and personal exposure to inhalable particles with diameters of generally 2.5 μm and smaller (PM2.5) was obtained using Teflon filters in portable particle samplers followed by gravimetric analysis. Results show that the FTK emits more PM2.5, EC, and OC per cooking stage than the MKD. In terms of PM2.5 emission factors, relative to the FTK, the MK2 is 61% smaller and the MKD emission factor is 39% smaller. Against our expectations, the MKD showed higher work environment exposure levels. This is due to the untested changes to the original MK2 design and a mismanagement of the operation processes. Personal exposure to CO and PM2.5 of local brick kiln workers was about three times higher than indoor exposure from the use of three-stone wood cookstoves in Mexico. The analysis of emission plumes from FTK and MKD using a coupled emission model dispersion model allowed us to evaluate the impacts, transport, and deposition area of the particle matter in the area surrounding Durango Brickyard (DB). Keywords Elemental carbon . Organic carbon . Particle matter . Brick kiln . Personal exposure . Air modeling * Abraham Ortínez-Alvarez [email protected] 1

Instituto Nacional de Ecología y Cambio Climático, Periférico 5000, Coyoacán, Insurgentes Cuicuilco, 04530 Ciudad de México, Mexico

2

Centro de Ciencias de la Atmósfera, UNAM, Universidad 3000, Ciudad Universitaria, Coyoacán, 04360 Ciudad de México, Mexico

3

Facultad de Ciencias, UNAM, Universidad 3000, Ciudad Universitaria, Coyoacán, 04360 Ciudad de México, Mexico

4

GAMATEK Laboratorios Analíticos, Alanís Valdez 2308, Colonia Industrial, 64440 Monterrey, Nuevo León, Mexico

5

Departamento de Toxicología, Centro de Investigaciones y de Estudios Avanzados del IPN (CINVESTAV-IPN), Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, Del. Gustavo A. Madero, 07360 Ciudad de México, Mexico

6

Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana, Av Universidad 3000, Coyoacan, Ciudad de Mexico, México

Introduction About 4.3 million premature deaths due to exposure to emissions from the combustion of solid and other polluting f uels were estim ated by the World He a l t h Organization in 2012 (WHO 2014). These impose a substantial public health burden in developing countries. One source of pollutants is the manufacture of artisanal bricks using solid fuels such as biomass, charcoal, and waste. This low-technology industry is a major source of pollution to urban cites such as Dhaka in Bangladesh (Guttikunda et al. 2013) or Bogota in Colombia (Pachon et al. 2014), with important health impacts as documented in Lahore, Pakistan (Sughis et al. 2014; Sidra et al. 2015). Other studies show (Guttikunda and Khaliquzzaman 2014; Kaushik et al. 2012; Zuskin et al.

Air Qual Atmos Health

Fig. 1 Number of brick kilns by state in Mexico in 2010

1998) that the emissions of several pollutants affect the respiratory health of brick makers or brick workers. In some Asian cities, the brick kiln industry is expanding due to increased urbanization and city sprawl which create demand for building materials (Bhanarkar et al. 2002). In Latin America, the artisanal brick sector has been considered an informal industry that contributes to air pollution and other environment deterioration without regulations or emission standards (UNEP-CCAC 2016). In general, these non-controlled industrial activities release multiple pollutants known to contribute to pulmonary diseases (asthma, bronchitis, emphysema, etc.) and non-pulmonary diseases including myocardial infarction (MI), stroke, and even cancer (cervical cancer and brain cancer) (Raaschou-Nielsen et al. 2011). Brick kiln emissions mainly consist of particle matter (PM) containing dust, EC and OC, also volatile organic compounds (VOCs), and nitrogen oxides (NOx) (Aslam et al. 1994; Joshi and Dudani 2008). Study of the health impact of these pollutants has focused on epidemiological and toxicological studies, although mainly based on ambient PM. Fewer studies have reported personal exposure to CO and PM 2.5 by brick workers. A study in Nepal (Sanjel et al. 2017) compares the incidence of symptoms and respiratory diseases in workers of brick kilns, in Fig. 2 Brick kiln types. a Traditional brick clamp. b Fixed traditional. (Source: INECC archives)

which firing brick kiln workers are more exposed to pollutants, about 14 to 19%, in comparison to store workers. Kaushik et al. (2012) reported that the respiratory effects on brick workers are caused by processes of toxic damage that involve oxidative stress, resulting from an increase in the generation of reactive oxygen species which induce tissue damage and a decrease in the antioxidant response Raza et al. (2014) report PM2.5 ambient concentrations during the whole of the brick making process to be from 301 to 628 μg/m 3 , in brick workers in Pakistan. Another study in Lahore, Pakistan, Sughis et al. (2014) showed that brick kiln workers were presumably exposed to mineral clay dust from the bricks, as well as to smoke emitted from the kilns, which are generally fueled by coal, biomass, and other materials, such as tires (Schmidt 2013). In the Greater Dhaka region, the brick industry releases high levels of ash and sulfur content (Guttikunda et al. 2013). Receptor modeling studies estimate an average contribution of 30–40% from brick kilns to the total measure of PM 2.5 pollution in the Dhaka Metropolitan Area (DMA) (Begum et al. 2008, 2013). The air quality models show that PM2.5 ambient concentrations over DMA ranged from 4 to 56 μg/m3 and an average of 30 μg/m 3 over the manufacturing period.

Air Qual Atmos Health Fig. 3 Basic design of MK2 kiln. Source: Bruce et al. (2007)

In terms of other important pollutants, the artisanal brick industry, with low-technology combustion systems and therefore the incomplete burning of organic fuels and mud, produces polycyclic aromatic hydrocarbons (PAHs) (Franco et al. 2008), which have been consistently linked to genomic, respiratory, and neurological toxicity (Gamboa et al. 2008; Perera et al. 2008; Svecova et al. 2009). During the brick manufacturing process, exposure to PAHs may lead to health risks not only for brick workers but also for other people, including children living in communities where brick making is carried out (Martínez-Salinas et al. 2010), in which PAHs are components of the particle matter. In Mexico, INECC (2016) estimates around 17,000 artisanal brick kilns in 2010, distributed throughout the whole country (Fig. 1). Problems similar to those in other parts of the world arise in some Mexican cities where the manufacture of bricks is carried out on a domestic scale, without technology or regulation and with a high environmental and health impact. Alegría-Torres et al. (2013) shows that the artisanal brick kiln sector releases inorganic compounds including CO2, CO, sulfur and nitrogen components, and PM. It is estimated that each artisanal kiln requires the direct labor of four people, resulting in 68,000 individuals directly exposed to pollutant emissions. Brick production is mainly performed in periurban sites with medium and high densification. In most cases, production takes place in the immediate vicinity of workers’ homes and the activity involves the whole family, who live in conditions of extreme poverty and malnutrition. In this sector, use of child and elderly labor is common. These two groups are highly vulnerable. Kilns in Mexico are the ceramic square Roman type with a fixed structure (FTK) and brick clamps, with average dimensions of 10 m2, similar to those described for other countries (Kulkarni and Rao 2016; Blackman et al. 2006). Average productions range from 10,000 to 15,000 bricks per production batch. In this type of traditional brick kiln, the combustion

of firing materials is inefficient in terms of consumption of raw materials, energy, and labor (Lloyd and Prior 2016). The main fuels used are firewood, industrialized wood, waste oils, fuel oil, tires, and industrial and domestic waste (Umlauf et al. 2009). These materials generate a large number of pollutants such as PM, EC, OC (Weyant et al. 2014), CO2, methane (CH4), VOCs, CO, NOx, PAHs (Chen et al. 2017a, b), and persistent toxins, such as dioxins and furans (García-Ubaque et al. 2010). There are many variations in the operation modes of different kilns used for manufacturing bricks in Mexico, so the objective of this study was to measure emissions under current operating conditions, not under controlled experimental conditions. In this study, we measured temporary concentration profiles of brick kiln plume releases of PM2.5, OC, and EC from an FTK and a modified MK2

Fig. 4 MKD kiln with side observation ports and flat roof. Source: INECC archive

Air Qual Atmos Health Fig. 5 Brick making process stages

kiln called MK Durango (MKD). Additionally, measurements to evaluate personal exposure levels of kiln operators to polluting gases and particles were performed. Also, from the emission inventory, an emission dispersion assessment of the DB was carried out through an inventorydispersion modeling assembly using virtual balloons (Yu and Gong 2012) from the Google Earth platform and HYSPLIT (hybrid single-particle Lagrangian integrated trajectory) (Draxler and Hess 1998).

Brick kilns in Durango Types of brick kilns The clamp kiln is merely a mesh pile of dried bricks with tunnels at the bottom allowing heat from fires to pass

through the pile of bricks and upward. The FTK (Fig. 2b) is usually constructed with adobe and brick walls and a base to mesh pile the bricks; it has no fixed roof, and its top is sealed with a mixture of adobe, clay, and mud during the burning process. Both kilns are very energy inefficient and the combustion processes are far from the optimal (Cárdenas et al. 2009; Kulkarni and Rao 2013, 2016). They require more fuel to reach proper firing temperatures, resulting in a large temperature gradient of between 1273 K at the base and 473 K at the dome, as well as the uneven heat inside the kiln producing low-quality bricks. The MK2 kiln reduces energy demand by using two combustion chambers connected by a lower duct, open/close valves in the duct and chimneys, dome-shaped ceilings that promote uniform heat flow, and the deposit of particulate material at the bottom (Fig. 3).

Fig. 6 Location of the DB in relation with the urban area of Durango de Victoria municipality. Source: INEGI 2017, Google Earth

Air Qual Atmos Health Table 1 period

Production data parameters measured during the evaluation

Parameters

FTK

MKD

Units

Total bricks per batch

10,600

7700

piece

Raw brick mass

2.53

2.36

kg

Cooked brick mass Pine wood fuel

2.22 NA

2.11 1198

kg kg dry basis

Fuel mix

NA

NA

kg dry basis

Pine wood Laminated pine

1676 428

NA NA

kg dry basis kg dry basis

Pine logs Pinus montezumaea Total ash content Production time

96 2

NA NA

kg dry basis kg dry basis

44.2 18.7

15.7 19.7

kg h

Total sampled gas Sample mass of CO2 Sample mass of CH4 Number of particle samples

17.30 30.3 0.08 9

18.13 21.9 0.03 9

m3 at STP g g filters

NA not applicable, STP standard conditions for temperature and pressure a

Reverchon et al. (2015)

Prior to operation, bricks are mesh-piled in both chambers. At the beginning of operation, the duct and chimneys are closed. At a certain moment, the duct valve connecting to the second chamber is opened, passing moisture, particles, and combustion gases from the first to the second chamber, where they will be absorbed by the bricks in a pre-cooking stage; then, the duct is closed, and the first chamber chimney is opened to release heat (González 2010). Cooked bricks are removed from the first chamber, and a new batch is introduced therein. The second chamber is fired, repeating the operation with pre-cooked bricks that require less fuel. Alongside, the third batch is also pre-cooked while trapping gases and particles from the cooking process of the second batch. The MK2 reduces fuel consumption and emissions up to 50% compared to FTK and clamp kilns (Bruce et al. 2007). In Durango, there were approximately 710 kilns in 2016, including FTK and clamp kilns, where FTKs produce 90% of the total bricks and clamp kilns the remaining 10%. DB has a MKD kiln built

Fig. 7 Crane sampling system on kiln domes for measuring combustion gases and particles. (Source: Gamatek photo archive)

following the original design of connected dual kilns; however, some modifications to the original design were made, such as the viewing ports used to supervise the cooking processes according to the flame color inside the kiln (Fig. 4).

Brick cooking process The manufacture of bricks with traditional kilns in Mexico has been documented in other studies (Cárdenas et al. 2009). It consists of the following four stages (Fig. 5). The first (mixing) stage is where clay, sand, organic material (manure and/or sawdust, among others), and water are mixed until a homogeneous paste is obtained. In the second stage (molding), the paste is placed in wooden or metal molds and the bricks are shaped. Then, in the third stage (drying), the bricks are aligned under an open sky to be sunbaked. In the final fourth stage kiln (firing), the bricks are placed into the kiln vault, and then, the kiln is sealed with clay, the fuel is fed into the tunnel, and a fire is started and maintained as needed according to the main operator’s expertise. In some cases, the operator uses air blowers to improve firing combustion. Cárdenas et al. (2009) reported that during fire baking, water loss occurs by evaporation from 373 to 423 K; at 473–623 K, the organic matter contained in the bricks is burned; at 723– 923 K, there is a loss of mass by clay dehydroxylation; there are no significant changes at temperatures greater than 1023 K. However, continuous firing and heating is required during the brick cooking process to maintain these high temperatures and ensure that all the bricks are cooked properly and achieve even quality (Cárdenas et al. 2012). These temperatures are not always reached and may vary depending on the fuel feeding, type of soil, and the proportions of materials used during brick manufacture.

Materials and methods Sampling site DB is located 25 km southeast of Victoria de Durango city at 1886 m.a.s.l. (meters above sea level). Currently, most of the


Fig. 8 Sample system train for gas and particle concentration determination in the FTK and MKD. (Source: Maíz (2012); Gamatek)

kilns in the DB are FTK and clamp kilns. However, Durango’s Air Quality Management Program (PROAIRE Durango 2016) suggests introducing new MKD kilns with low-cost technology and relocating 720 kilns including FTK and clamp type ones from the urban area of Victoria de Durango to DB (104° 28′ 32.72″ W and 23° 53′ 51.64″ N) (Fig. 6).

Production data parameters in the kilns During the current evaluation conditions, both kilns use a batch production method according to the following characteristics (Table 1):

Gases and PM2.5 There is no standard method to measure emissions of particles and gases from traditional kilns due to the lack of a proper stack with sampling ports to use an isokinetic sampling method (Baroutian et al. 2006) on both kilns. However, some measurements have been developed in Mexico using US Environmental Protection Agency standardized reference methods (US-EPA 2017) for combustion gases and particles (Maíz 2012). The FTK does not have a stack, so the combustion gases are released through the sealed cover of the kiln top and the cracks in its walls. Some particle matter is retained in the seal material. The MKD has two stacks of 1 m each, which are not tall enough to use isokinetic methods. Gases and particles were released through one or the other according to the firing process. Therefore, both kilns were sampled with a system of cranes on the domes (Fig. 7). CO and CH4 were measured with a spectrophotometer (Gasmet Technologies Oy, Model DX4000, www.gasmet. com) following, respectively, US-EPA method NSPS RM

3A and American Society for Testing and Materials (ASTM) method D 6348-03. The measuring probe was placed on the crane beside the PM2.5 high volume sampler. PM2.5 sampling was performed following reference method RFPS-0498-116 with a BGI Incorporated PQ200 Air Sampler and a very sharp cut cyclone (www.bgi.mesalabs.com) attached to the crane arm within a thermal cover to withstand the high temperatures of exhaust gases and particles (Fig. 8). The instruments had capacity to move over the kiln dome and capture gases and particles, always following the emission plumes. PM2.5 samples were collected on quartz filters (Pallflex, 47 mm) and replaced every 2 h to obtain a temporary profile, so the mass concentration of the analyte Ci (1) is proportional to the sampled mass mi and the volume of gases v passing through the sampler: Ci ¼

mi V

ð1Þ

The total carbon mass released by each kiln was calculated, assuming that the total carbon content in the fuel and the carbon lost by the bricks was emitted as CO2, CO, CH4, NMHC, EC, and OC. Assuming these species were

Table 2

Configuration of personal exposure equipment

Sampling type FTK and MKD

PM2.5

CO

Worker (W-01) Worker (W-02) Fixed point (FP)

x x x

x None x

Air Qual Atmos Health 20x10

3

PM

18

2.5

16 FTK MKD

3

PM2.5 ( g/m )

14 12 10 8 6 4 2 1

2

3

4

5

6

7

8

9

Sample Number

2600

Elemental carbon

2400

2000

FTK MKD

3

Elemental Carbon ( g/m )

2200

1800 1600 1400 1200 1000 800 600 400 200

1

2

3

4

5

6

7

8

9

Sample Number

11x10

3

Organic carbon

10

3

Organic carbon ( g/m )

9 FTK MKD

8 7 6 5 4 3 2 1

1

2

3

4

5 Sample Number

6

7

8

9


Fig. 9

Concentration profiles of PM2.5 and elemental and organic carbon in micrograms per cubic meter during firing process

well mixed through any emission point, emission ratios relative to total carbon (TC = CO 2 + CO + CH 4 + NMHC + EC + OC) were obtained. Then, emission factors (g/mg of brick) can be obtained using a carbon balance method (Weyant et al. 2014).

Table 4

Ash amount and carbon percentage

Kiln

Ash amount (kg)

Carbon content (% dry base)

FTK (combustion chamber) FTK (upper part)

10.10

3.71

34.62

1.40

5.16

4.20

11.61

4.14

MKD (combustion chamber) MKD (smoked bricks)

Organic and elemental carbon Personal exposure OC represents a large variety of organic compounds that can be classified into general compound classes such as aliphatic, aromatic compounds, acids, etc. (Cao et al. 2004). EC, in some cases also called black carbon (Chow et al. 2004; Bond et al. 2013), is actually a mixture of graphite-like particles and light-absorbing organic matter. Moreover, the surface of EC particles contains numerous adsorption sites that are capable of enhancing catalytic processes. BParticle total carbon (PTC)^ refers to the total, noncarbonate fraction of particulate carbon; as such, it includes what are commonly called OC and EC carbon fractions (NIST Certificate of Analysis 2009). Quartz filters containing PM2.5 were analyzed to determine the content of carbon by the coulombimetry method (Klimaszewska et al. 2009). The instrument consists of a furnace (CM5300) and a coulombimetric titration unit (CM5014). The sample is oxidized in a furnace at a constant temperature (973 K to quantify PTC and 773 K for OC), and the gases produced in the combustion process were carried through magnesium perchlorate anhydride, acid dichromate on silocel, and manganese dioxide, to eliminate the interfering gases sulfur dioxide (SO2), sulfur trioxide (SO3), hydrogen sulfide (H2S), water (H2O), hydrochloric acid (HCl), hydrogen iodide (HI), hydrogen bromide (HBr), chlorine (Cl2), and nitrogen oxides (NOx), and finally, the pure CO2 was measured by coulombimetric titration (Alvarez-Ospina et al. 2016). The coulombimetric detector quantifies the carbon content in a range from 0.01 to 100 μg. EC was calculated using the following Eq. (2): EC ¼ PTC–OC

ð2Þ

Table 3 Average emission concentration over the entire evaluation period. Particulate matter PM2.5 and elemental and organic carbon (μg/ m3) Pollutant

FTK

MKD

FTK/MKD ratio

PM2.5 Elemental carbon Organic carbon

8.39 0.67 4.57

4.07 0.28 2.24

2.05 2.39 2.04

CO and PM2.5 at respiratory tract level measurements were done with personal monitoring instrument kits. CO exposure was measured with a Langan T15 CO meter (www.langan. biz) using an electrochemical cell (Huang et al. 2012). PM2.5 samples were collected with a personal impactor (MSP Corp. Model 200, www.mspcorp.com) assisted by a 4 l per minute (l.p.m.) flow vacuum pump (SKC-224-PCXR8, www.skcinc. com) (Morales-Betancourt et al. 2017). Samples were collected on 37-mm-diameter Teflon filters for 4 h in the FTK and 3 h each in the MKD. This is because the MKD filters were saturating faster than the FTK filters. Gravimetric standard protocols were followed (Chen et al. 2017a, b). Three sampling kits were used in the working environment. One kit was carried out by the person responsible for feeding the kiln (W-01); a second kit was carried out by the assistant to the main operator (W-02), and the third kit was on the outer wall at a fixed point (FP) on the kilns, approximately 3 m away from the kiln supply port. For the MKD, it was placed in front of the observation porthole. The kit carried by W-02 was not fitted with a CO monitor (Table 2).

Dispersion model Two coupled models were used to estimate possible impacts of emissions, transport, and end point of particle matter from kilns on the environment and human health. The implementation of the HYSPLIT dispersion model (Connan et al. 2013) on Google Earth was coupled with an emission model, under development, also on the Google Earth platform, and its Keyhole Markup Language (KML) metadata standard (De Paor and Whitmeyer 2011).

Results and discussion Emission profile of PM2.5 and elemental and organic carbon Sampling was performed for about 18 h in both kilns, taking samples every 2 h to complete 1 m3 for each sample. Figure 9

Air Qual Atmos Health Table 5

Operating parameters of FTK and MKD kilns

Parameters

FTK

MKD

FTK/MKD ratio

Effective sampling time (h) Captured PM2.5 mass (μg) Total carbon mass in PM2.5 filters (μg) Organic carbon content in PM2.5 filter (μg) CO2 mass (g) CH4 mass (g)

17.27 75.59 47.33 41.20 30.32 0.08

18.15 37.93 23.66 34.12 21.92 0.03

0.95 1.99 2.01 1.20 1.38 2.66

Total carbon emitted into the atmosphere (kg C) Total energy consumed (GJ)

1736.77 83.38

1079.93 42.51

1.60 1.96

Energy consumption (GJ/mg) Total carbon emitted (kg C/mg)

3620.23 75.40

2596.10 65.94

1.39 1.14

shows the concentration profile for PM2.5, EC, and OC in both kilns. The MKD combustion gases were conducted directly to the first of the stacks instead of the second chamber for 6 h and then redirected to the second chamber as is established in the protocol (Marquez 2013), resulting in a rapid increase of particles and combustion gas emissions in the first stack. In the first sampling cycle, the concentrations of PM2.5, EC, and OC were higher for the MKD than the FTK. However, after the second sampling cycle, emissions of these three pollutants from the MKD were consistently lower than from the FTK. Fueling the kilns is not a continuous process, and feeding too little or too much material into the combustion chamber results in relative concentration peaks caused by the dynamics of fuel combustion. For instance, on the FTK, the concentration peaks for PM2.5, EC, and OC after 14 operation hours are probably due to a slow combustion of organic material mixed with the brick material used to seal the top of the kiln. This top is used to retain heat combustion gases and increase the available heat on the upper layers to complete the cooking of those bricks without overheating bricks on layers below. MKD has a dome, so it does not need that additional heat source. Overall, even with the mismanagement by the MKD operator reported above, and the use of an air blower by the FTK operator to improve fuel combustion, emissions from the FTK are a factor of two higher than the MKD (Table 3). Table 6

Emission factors of kilns

Emission factor

FTK

MKD

Units

PM2.5 PM10 Elemental carbon Organic carbon Greenhouse effect gases Total carbon emitted

632 735 51 345 270 75.4

386 448 38 287 237 65.9

g/mg bricka g/mg brick g/mg brick g/mg brick g/mg brick kg CO2 eq/mg brick

a

The remaining ashes were weighed, and their carbon content determined for the carbon balance on both kilns. As it is a common practice for the FTK to cover the dome with sawdust, this was also weighed, and its carbon content measured (Table 4). Furthermore, the ashes contained in 500 pieces of cooked bricks were also weighed. The values of several measurements and calculated parameters are shown in Table 5. With the exception of sampling time, FTK/MKD ratios were higher than unity in all cases. The carbon balance method (Weyant et al. 2014) was used to estimate emission factors in units of grams of pollutant per milligram of cooked brick (Table 6). The Btotal energy consumed^ was quantified by taking several biomass fuel samples from both kilns to the laboratory (Table 1), in order to determine the biomass caloric values (Núñez-Regueira et al. 2001; Cárdenas et al. 2009, 2012), following (ASTM) method E 711-87. The calculation uses the mass ratio of emitted pollutants, PM2.5, EC, OC, CO2, CH4, to TOC. The emission factor estimation shows that, on average, EC, OC, and PM2.5 from the FTK are about 1.3 higher than from the MKD. This 30% excess may be due to the last stage emissions from the FTK (Fig. 9) when the biomass used for sealing the kiln top is burned and increases particles and gas emissions captured in sampling stage 7. Avoiding the abovementioned mismanagement of the MKD would have made it much more efficient than the FTK.

Milligrams of fired brick

Comparative PM2.5 emission factor in several kilns in Mexico A first analysis of PM2.5 emission factors using the same particle sampling method for MKD, FTK, MK2, and traditional clamp kiln (TCK) (Maíz 2012) shows that TCK has the largest PM2.5 emission factor, 1141 g/mg brick; FTK is the second, 632 g/mg brick; MKD is the third, 386 g/mg brick, and MK2 has the smallest (Cárdenas et al. 2012) emission factor, 241 g/mg brick. The

Air Qual Atmos Health Fig. 10 Concentration profiles of CO in parts per million determined by the equipment (W0-1) worker responsible for feeding the kilns: FTK and MKD

difference between MK2 and MKD PM2.5 emission factors is due to a mismanagement of operation at the starting stage and the non-tested modifications, including the addition of the viewing porthole in the MKD.

Personal exposure On the MKD, the first 5 h of cooking bricks exposed the W-01 operator to larger CO concentrations (9.2 ppm) than the FTK, as Fig. 10 indicates. The MKD W-01 operator was under a flat shade roof in front of the fuel/air feeding port. This shade was not present in the FTK. The roof protects the operator from the intense sunlight, but reduces the ventilation of particles and gases emitted from the kiln. Also, the MKD’s observation portholes were venting particles and gases during the whole process. A few hours later, the MKD W-01 operator received only

one exposure burst of 8.9 ppm. The FTK W-01 operator received a CO concentration of 7.4 ppm at the beginning of the process; but he received six emissions bursts reaching 12 ppm, when he was feeding the fire in the combustion chamber. The CO monitor placed at the fixed point, 3 m away from the feeding port, shows that support workers around the feeding port may be exposed to larger CO concentrations for a longer time with the FTK than with the MKD (Fig. 11). This is in spite of the fact that the MKD fixed point was placed in front of the observation portholes, which acted as a vent to the kiln (Fig. 4). On the other hand, MKD workers used an air blower to improve fuel combustion. Additionally, feeding the fire required more time on the FTK. The PM2.5 work-environment concentrations to which the main operator (W-01) was exposed were higher for the MKD than the FTK (Fig. 12). During the brick cooking process, four

Air Qual Atmos Health Fig. 11 Concentration profiles of CO in parts per million measured in fix points, located on the kiln walls. a FTK. b MKD

samples of 3 h each were taken on the portable sampler carried by the MKD W-01, while only three samples, of 4 h each, were taken on the portable sampler carried by the FTK W-01. Overall, the average exposure to PM2.5 as collected in the MKD W-01 was 1.45 higher than in the FTK-W01. For both

kilns, W-01 operator was exposed to particle concentrations approximately five times higher than W-02 assistant. The average exposure of MKD W-02 was 1.76 times higher than FTK W-02. Also, with the exception of stage (P1), the PM2.5 collected in the FP filters was always higher in the

Fig. 12 PM2.5 (μg/m3) concentrations for W-01, W0-2, and FP. a FTK (left). b MKD (right)

Air Qual Atmos Health Table 7

Comparison of estimated average concentrations from brick kilns and cookstoves

Parameters

FTKMexico

MKDMexico

Three stone Cookstoves Masera et al., 2007

Three stone Cookstoves Bruce et al., 2015

WHO

PM2.5 (μg/m3) CO (mg/m3)

341 8.47

415 10.53

300 10.07

200–300 None

10a 7b

a

Annual average value

b

Twenty-four-hour guideline level

MKD than in the FTK working environment. However, average exposure at the MKD-FP was just the same as at the FTKFP. This is due to the weight of the P1 measurement. This poor performance of MKD may be explained by the presence of the flat shade roof, already mentioned above, that favored the accumulation of particles in that working environment, aggravated by the presence of the observation portholes added to the MKD and the incorrect operation of MKD during the first 2 h of firing.

Comparison of personal exposure measurements As there are very few published studies of personal exposure measurements in this kind of working environment, to put the values found in this work into context, we compare with some reported values in other working environments where solid biomass is used (Table 7). Basically, indoor cooking using traditional open-fire wood-burning stoves and firing traditional fixed kilns are approximately the same dirty and unhealthy working environment. The use of improved wood-burning

cookstoves makes a great difference on personal exposure. However, firing the MKD shows no improvement compared to the FTK due to the already mentioned untested design changes and mismanagement of the MKD.

Evaluation of pollutant parcel transport from the Durango Brickyard To study the emission, transport, and end point of particle matter pollutants of the DB in the city of Victoria de Durango, the HYSPLIT model was implemented to estimate and compare ambient measurements (Cohen et al. 1995, 1997, 2002; Draxler and Hess 1998; Draxler 1991, 2000; Stein et al. 2000; Rolph et al. 1992, 1993; McQueen and Draxler 1994; Velasco et al. 2016). This work incorporated the metadata brick kiln emission inventory (INECC 2016) developed on KML as its semantic core was coupled with a Gaussian dispersion model developed and maintained by NOAA (http:// ready.arl.noaa.gov/HYSPLIT.php). Both models use the Google Earth platform to transfer and display the key

Fig. 13 FTK plume emission from Durango Brickyard. Source: Google Earth, HYSPLIT with this work data)


Fig. 14 FTK emission plume evaluation from Durango Brickyard October 10, 2015

information for analysis. Figure 13 shows the coupling of both models. Ambient concentrations and the emission plume trajectories (McQueen and Draxler 1994) were modeled for both kilns, the FTK on October 10 (Fig. 14) and the MKD on October 12 (Fig. 15), dates when measurements were carried out. In both cases, Victoria de Durango city was not impacted by the trajectory plume. Also, in both evaluation scenarios, modeled plume PM 2.5 concentrations were higher than 500 μg/m3 during all the modeled day up to 3–5 km from the emitting kiln. Although the plumes are quite narrow, several kilns would be operating at the same time on any working day and the ambient concentrations could increase by a factor

Fig. 15 MKD emission plume in Durango Brickyard October 12, 2015

of 3 to 5 depending on local weather conditions and the number of brick kilns operating.

Conclusions Evaluation under real and uncontrolled operation conditions allowed us to better understand the performance of FTK and MKD kilns in terms of the emission profile of EC, OC, PM2.5, and other species, where the most critical releases of pollutants for both kilns are at the beginning of the cooking process and only for the FTK is there a second critical release at the last stage of the cooking.


Overall, even with the burden of initial mismanagement, the MKD outperforms the FTK kiln in terms of emissions to the atmosphere. The MKD emits fewer pollutants (EC, OC, and PM2.5) than the FTK. In Mexico, ranking PM2.5 emission factors by kiln technology, the largest is from the TCK (1141 g/mg brick), then the FTK (632 g/mg brick), followed by the MKD (386 g/mg brick), and the smallest emission factor from the MK2 (241 g/mg brick). This work shows how easily some of the environmental benefits achieved by the low technology-improved MK2 kiln were lost due to operation by untrained personnel at the MKD kiln. The comparison indicates that applying mitigation technology requires supervision by authorities, training, and good practice on implementation and operation. In terms of personal exposure, in the absence of reported data under similar working conditions, we compare with traditional indoor three-stone cookstove. MKD W01 was exposed to an average of 415 μg/m3 of PM2.5, higher than average exposure of 341 μg/m3 obtained for FTK W-01, and the reported exposure for indoor threestone cookstove environments ranges from 200 to 300 μg/ m3. The WHO standard shows that brick kiln workers are highly exposed to PM2.5 and also EC and OC that are components of the PM2.5 fraction. The average ambient concentration of CO reported for a traditional three-stone cookstove is 10.07 mg/m3, just about the same exposure as MKD W-01 (10.53 mg/m3) and slightly higher than FTK W-01 (8.47 mg/m3). The higher exposure of the MKD operator to emissions is also due to the fixed shade that hampers ventilation at the fuel/air feeding port. Again, good practice in implementation and operation of the low technology-improved MK2 kiln is paramount to obtain the mitigation potential and health co-benefits of this intervention. The coupled emission inventory and dispersion models show that under similar mesoscale meteorological patterns, the city of Victoria de Durango is not under the influence of emissions from the new location for this activity. Nevertheless, according to the modeling outputs, FTK kiln operators and their families that live around DB are exposed to three times higher ambient levels of PM2.5 in comparison with the MKD. Acknowledgments The authors are grateful to the local authorities of the 2010–2016 Durango State administration for facilitating this work; Secretaría de Recursos Naturales y Medio Ambiente (SRNyMA), Eng. Jesús Soto Rentería; also to the 2013–2016 Durango de Victoria municipality administration; to the Federal Ministry of Environment SEMARNAT; to the National Institute of Ecology and Climate Change (INECC) field technicians; Felipe Ángeles, Becki Gatica, Faviola Altúzar, and Beatriz Arely also to GAMATEK field technicians, and to Erika Marcé and Ileana Villalobos who provided very useful comments. Ruiz-Suárez L.G. thanks UNAM for the sabbatical leave that allowed him to participate in this work. The corresponding author would like to thank

the National Council for Science and Technology (CONACYT) for the grant to support his Doctoral degree. The authors declare no financial relationships or other kind of activities with any organizations that might have an interest in the submitted work.

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