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Distribution and physicochemical properties of particulate matter in swine confinement barns
Environmental Pollution 250 (2019) 746e753
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Distribution and physicochemical properties of particulate matter in swine confinement barns* Dan Shen 1, Sheng Wu 1, Zhaojian Li, Qian Tang, Pengyuan Dai, Yansen Li, Chunmei Li* National Experimental Teaching Demonstration Center of Animal Science, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 15 November 2018 Received in revised form 16 April 2019 Accepted 16 April 2019 Available online 17 April 2019
Air pollutants accumulated in confined livestock barns could impact the health of animals and staff. Particulate matter (PM) and ammonia (NH3) concentrations are typically high in enclosed livestock houses with weak ventilation. The objective of this study was to investigate the distribution of PM in different size fractions and the levels of NH3 in a high-rise nursery (HN) barn and a high-rise fattening (HF) barn on a swine farm and to analyse the physicochemical properties of fine PM (PM2.5, PM with aerodynamic diameter 2.5 mm). The concentrations of total suspended particles (TSP, PM with aerodynamic diameter 100 mm), inhalable PM (PM10, PM with aerodynamic diameter 10 mm), PM2.5 and NH3 were monitored continuously for 6 d in each barn. The results showed that the concentrations of PM and NH3 varied with position, they were significantly higher inside the barns than outside (P < 0.01) and significantly higher in the forepart than at the rear of the two barns (P < 0.05). In the HF barn, the values of the two parameters were 0.777 ± 0.2 mg m 3 and 26.7 ± 7 mg m 3, respectively, significantly higher than the values observed in the HN barn at all monitored sites (P < 0.05). The PM concentrations increased markedly during feeding time in the two barns. Chemical characteristics analysis revealed that the main sources of PM2.5 in the two barns may have consisted of blowing dust, feed, mineral particles and smoke. In conclusion, the air quality at the forepart was worse than that at the rear of the barns. Activities such as feeding could increase the PM concentrations. The components of PM2.5 in the two barns were probably blowing dust, feed, mineral particles and smoke from outside. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Swine confinement barn Particulate matter Ammonia Physicochemical property
1. Introduction In livestock production, intensive poultry and pig housing are the main sources of particulate matter (PM) and ammonia (NH3) emissions. Both PM and NH3 are two major pollutants in pig facilities environments (Wang-Li et al., 2013; Kristensen and Wathes, 2000), and concerns have been raised on their potential hazard to human health and the environment (Yao et al., 2018). High concentrations of PM, especially fine particulate matter (PM2.5, PM with aerodynamic diameter 2.5 mm), which may penetrate into the alveoli through the respiratory tract based on its small size, are considered a potential hazard to worker health and animal welfare (Arphorn et al., 2018; Lee et al., 2018). Recent studies have
*
This paper has been recommended for acceptance by Charles Wong. * Corresponding author. E-mail addresses: [email protected], [email protected] (C. Li). 1 Both the authors contributed equally to this work.
https://doi.org/10.1016/j.envpol.2019.04.086 0269-7491/© 2019 Elsevier Ltd. All rights reserved.
highlighted the role of ambient PM as an important environmental pollutant that is associated with many different cardiopulmonary diseases and with lung cancer. Gaseous pollutants, bacteria, and viruses could attach to the PM, which can be dispersed over long distances, and cause infectious and allergic diseases (Winkel et al., 2015). The PM2.5, one of the leading challenges to global public health, is well known to cause various adverse cardiopulmonary effects (Feng et al., 2016). Exposure to ambient PM2.5 can also induce dysfunction of the male reproductive system (Qiu et al., 2017). The respiratory health of finishing pigs was shown to be significantly affected by PM10 (Michiels et al., 2015), and nursery pigs are more sensitive to PM than fattening pigs because their immune systems are relatively weak (Yao et al., 2010). Although the health effects of PM have been well documented, there is no threshold level of PM concentration that is known to have no adverse health effects (WHO, 2013). Ammonia, another major pollutant in swine barns, is mainly released from manure, is a wellknown toxic gas that poses a potential health hazard to both producers and pigs (Banhazi et al., 2008). Increased NH3
D. Shen et al. / Environmental Pollution 250 (2019) 746e753
concentrations could result in a higher incidence of pleuritic lesions (Michiels et al., 2015). In addition, excessive NH3 can pollute the surrounding environment when released by the ventilating system, leading to acidification of the soil and nitrogen deposition in ecosystems (NRC, 2003). Globally, the livestock sector is responsible for approximately 65% of anthropogenic emissions of NH3, including energy consumption and land-use change. The concentrations of PM and NH3 in livestock houses are impacted by the type of housing system used, the ventilation rate, the animal species and the sampling method (Ellen et al., 2000). Other important factors include animal activity, stock density, temperature and relative humidity (Chen et al., 2011). Investigations of the indoor concentrations of PM and NH3 in different conventional pig-fattening facilities have shown that there is a strong correlation between PM emission rates and housing systems, ventilation rates and operation practices (Ransbeeck et al., 2013). Swine confinement buildings are becoming larger and more intensive due to increasing market demand, and the air pollution inside these buildings is getting worse. Some papers have reported PM concentrations, emission levels and key factors for PM generation in pig houses (Ransbeeck et al., 2013; Kwon et al., 2016). Knowledge of the distribution and preliminary source analysis of PM are also very important for controlling the PM concentration the swine confinement buildings, but there are few studies of PM spatial distribution or ultrastructural observation of PM2.5 in enclosed swine confinement buildings, and data on the effects of feeding and ventilation rate on PM generation, especially for swine confinement buildings, are sparse. The present study aimed to investigate the distribution of indoor PM and NH3 and to conduct an ultrastructural analysis of PM2.5 in high-rise nursery (HN) and high-rise fattening (HF) pig barns. The correlation of PM and NH3 concentrations with environmental parameters such as temperature, relative humidity, and illumination was also assessed. 2. Materials and methods 2.1. Swine facility The barns in this study are typical of those presently used in China and are located at a large-scale closed swine farm in Zunyi city of Guizhou province. A total of 30 fattening barns and 10 nursery barns are located at the farm; all are oriented in a northsouth direction and were built in 2011. One high-rise nursery barn and one fattening barn were selected as the experimental barns. The stocking population of nursery pigs and fattening pigs were 325 and 152 respectively, and each of the two barns was 26.0 m long and 15.0 m wide. Each house had a 2.0 m-high sidewall and a 1.2 m-high first-floor manure pit underneath the slatted floor where manure was stored for approximately 3 months (Fig. S1). There was no ventilation window in the HN barn, although it had a suspended ceiling; air flowed into the barn through 40 oblique adjustable air inlets in the ceiling (Fig. S2). The nursery pigs were 6 weeks old, and all weighed approximately 13 kg. The breeds were (Duroc Large Yorkshire Landrace) three hybrids. The barn was equipped with a mechanical ventilation system consisting of exhaust fans of type QYT-1530 installed in the north wall 0.8 m above the ground. The ventilation was controlled by exhaust fans which operated depending on the temperature inside the barn during the daytime from 8:00 to 20:00. All four fans were turned on when the temperature was higher than 24 C; when the temperature was lower than 23 C, only one fan was operated to maintain weak ventilation. The primary heating devices in the HN barn were model KD741 heat preservation lamps. There was only one shaft
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door at the forepart of the barn, and this door was usually kept closed. In the HF barn, there were 4 small ventilation windows (L W: 90 45 cm) above the regular windows in the sidewall of the barn. The fattening pigs in the HF barn were approximately 130e150 kg in weight and 25 weeks old. There were 20 pens and 152 fattening pigs in the HF barn. The ventilation in this barn was also controlled by exhaust fans based on the temperature inside the barn, and the operation of the exhaust fan system was the same as that in the HN barn. There was no heat preservation lamp. The remaining devices were the same as those in the HN barn (Table S1). 2.2. Swine barn management Feeding arrangement: Nursery pigs were fed pelleted feed manually at 9:00 and 14:30; the total amount of feed was 0.5 kg daily each. Fattening pigs were fed 4.5 kg of pelleted feed once daily each at 10:00 using an automatic feeder. Ventilation management: Ceiling ventilation was used in the HN barn. The fans were turned on at 8:00 to adjust the ventilation. There were four small air intake windows in the end wall at the south side of the HF barn, which was ventilated via a combination of the ceiling vents and the air intake windows. The fans in the HF barn were turned on at 8:00, and the ventilation was regulated by the temperature control system. Lighting management: Both the lighting and the heat preservation lamps in the HN barn were turned on during the monitoring period (07:00e19:00), while only the lighting lamps were turned on in the HF barn. 2.3. Measurement strategy The environmental parameters were monitored from 1st to 12th April 2017. The PM (TSP, PM10 and PM2.5), NH3 concentrations, temperature, relative humidity and illumination were measured at different horizontal locations (east, west, forepart, rear and outside) at a height of 0.5 m and at different heights (0.5 m, 1.0 m and 1.5 m) in the middle of the barns (Fig. S1). Monitoring of each barn was performed from 07:00 to 19:00 at 2-h intervals for 6 d (7 times per day). The specific dates on which the measurements were made from 1st to 6th April in the HN barn and 7th to 12th April in the HF barn. The temperature and relative humidity in each barn were recorded at 30-min intervals during a 24-h period. The outside measuring site was 5 m from the entrance to the pig barn. The PM2.5 was collected inside the pig barns at a flow rate of 16.7 L min 1 for 12 h per day for 6 d and subjected to ultrastructural observation. 2.4. Monitoring equipment A BTPMeHS1 ambient air particle sampler (Dandong Baite Instrument Co., Ltd., Liaoning, China) was used to collect PM2.5 from the HN and HF barns. The sampler was set at a flow rate of 16.7 L min 1 for 12 h per day. Particulate samples were captured on prebaked quartz filters (47 mm diameter, Whatman Inc., Clifton, NJ, USA) and were stored at 20 C after sampling. Ultrastructural observation was conducted using a SU8010-type field scanning electron microscope (SEM, Hitachi, Tokyo, Japan) and the relative content of chemical elements were measured using an energy-dispersive X-ray spectroscope (EDS, Bruker, Germany) attached to the SEM. The PM concentrations in the two barns were measured using a DustTrak™ ІІ 8532 Handheld Aerosol Monitor (TSI Inc., Minnesota, USA). This direct-reading portable PM monitor operates on the principle of scattered light beams; it can detect PM at concentrations ranging from 0.001 to 150 mg m 3 and has a measurement accuracy of ±0.001 mg m 3. The software provided with monitors
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could also show the concentrations of PM2.5, PM10 and TSP. Concentrations of NH3 were continuously measured using a JK40-ІV portable gas detector (Ji Shun'an Technology Co., Ltd., Guangdong, China) that has a detection range of 0e100 ppm and an accuracy of ±3% (F.S). It was connected to an electrochemical sensor with a resolution of ±0.01 ppm. Eight RC-4HC temperature and relative humidity recorders (Jingchuang Electric Co., Ltd., Jiangsu, China) with measurement accuracies of ±0.5 C and ±3% RH were used simultaneously to record the temperature and relative humidity at various locations within the barns. An LX-101 light illumination meter (Luchang Electric Co., Ltd.) was used to record illumination in the barns. All instruments were calibrated according to the manufacturer's instructions prior to measurement. Airflow speed in barns is regarded as a key environmental parameter that has important effects on the concentrations of PM, gases and other components. Airflow speed was also measured using a DEM6 three-cup wind anemometer (Tianjin Meteorological Instrument Factory, Tianjin, China) in this work; unfortunately, data on weak airflow speed were not obtained. 2.5. Data analysis The data were statistically analysed using GraphPad Prism 6.0 software, which is designed and marketed specifically for use in scientific graphing and statistical analysis. Difference analysis was performed using ANOVA; P values less than 0.05 (P < 0.05) or 0.01 (P < 0.01) were taken to indicate statistically significant differences. If the difference was significant, the LSD method was used for multiple comparisons. The test results are expressed as “mean ± standard deviation (SD)”. Pearson correlation coefficients were calculated to quantify the correlations between environmental parameters. 3. Results and discussion 3.1. Temperature and relative humidity As shown in Fig. S3 and Fig. S4, the temperature in the HN and HF barns ranged from 23.2 C to 26.1 C and 21.7 Ce24.6 C, respectively. The relative humidity in the two barns was 67.2%e 77.5% and 70.6%e75.5%, respectively. The temperature and humidity in the two barns were maintained in the relatively optimum range by light management, the housing system and the ventilation method. The temperature in the HN barn was higher than that in the HF barn because the optimal temperature for weanling nursery pigs is approximately 26 Ce28 C. The average temperature and relative humidity outside the barns were 14.2 C and 66.7%, respectively; thus, the temperature outside was lower than the indoor temperature. The great variation in the temperature inside the HF barn may be related to the local weather, which varied greatly. The relatively small variation in the temperature inside the HN barn might be due to better heat preservation in that facility.
3.2. Particulate matter and ammonia concentrations 3.2.1. PM and NH3 concentrations in nursery and fattening barns The mean TSP, PM10, PM2.5 and NH3 concentrations in the two barns are shown in Table 1. The mean concentrations of TSP, PM10 and PM2.5 inside the HN barn were 0.635 ± 0.1 mg m 3, 0.388 ± 0.09 mg m 3 and 0.210 ± 0.09 mg m 3, respectively. Another study reported that a mechanically ventilated nursery barn with a structure similar to the barn studied in this work had higher PM concentrations, approximately 1.5 mg m 3 for TSP and 1 mg m 3 for PM10. This difference may have been caused by the stocking density, which was 1.2 head$m 2 in this study and 2.2 head$m 2 in the barn that yielded the peak value in the published paper (Kwon et al., 2016). The mean NH3 concentration in the experimental HN barn was 12.2 ± 3 mg m 3. A previous paper reported that nursery barns equipped with variable-speed pit fans that directly exhaust the air from manure pits, had a low NH3 concentration of approximately 3 mg m 3. Another important factor that may have affected the NH3 concentration was the stocking density, which was 1.18 head$m 2 in the reported paper, lower than that in the present study (Liu et al., 2017). The measured levels inside the HF barn were 0.777 ± 0.2 mg m 3 for TSP, 0.338 ± 0.1 mg m 3 for PM10 and 0.144 ± 0.06 mg m 3 for PM2.5. In another study, the measured TSP concentration in an ordinary barn was higher (1.14 ± 0.6 mg m 3) than the TSP concentration observed here, whereas it was lower (0.375 ± 0.2 mg m 3) when the finishing barn was treated with daily soybean oil sprinkling (Heber et al., 2006). The PM10 concentration in the present study was lower than reported for other fattening barns, in which it ranged from 0.459 to 1.75 mg m 3. This maybe because there was only one ventilator in the barn described in the reported paper, and inadequate ventilation may have led to the accumulation of PM. However, this result is not consistent with the PM2.5 concentration, which was higher in this study than has been reported for other fattening barns (Ransbeeck et al., 2013). This might be due to the high PM2.5 concentration outside the barns, which was even higher than that inside the abovementioned barns. The average concentration of NH3 in the HF barn was 26.7 mg m 3, which is among the highest levels reported in related studies (Ransbeeck et al., 2013; Liu et al., 2017). The gaps in the slatted concrete were slightly too narrow to allow faeces to drop fully in the HF barn; therefore, some faeces were stored on the concrete slats during this experiment. This may explain why the NH3 concentration was so high. It exceeded the standard of 25 mg m 3 set forth in NY/T 388e1999 “Environmental quality standard for the livestock and poultry farm” (The Ministry of Agriculture of the People's Republic of China, 1999), indicating a potential health hazard to the fattening pigs. It was shown that the concentration of PM2.5 outside exceeded both the air quality guideline of 0.025 mg m 3 recommended by WHO (2000) and the second standard concentration of 0.075 mg m 3 in China. The PM2.5 and PM10 concentrations near the
Table 1 Levels of particulate matter (PM) and ammonia (NH3) in high-rise nursery (HN) and high-rise fattening (HF) barns. Item HN
HF
Outside
TSP (mg$m Mean ± SD Max Min Mean ± SD Max Min Mean ± SD Max Min
0.635 ± 0.1 1.08 0.228 0.777 ± 0.2 2.18 0.307 0.163 ± 0.1 0.371 0.0310
3
)
PM10 (mg$m 0.388 ± 0.09 0.658 0.152 0.338 ± 0.1 0.835 0.116 0.111 ± 0.07 0.226 0.0180
3
)
PM2.5 (mg$m 0.210 ± 0.09 0.415 0.0950 0.144 ± 0.06 0.374 0.0380 0.0880 ± 0.05 0.185 0.00400
3
)
NH3 (mg$m 12.2 ± 3 20.6 3.12 26.7 ± 7 45.9 14.3 2.27 ± 1 6.60 1.66
3
)
D. Shen et al. / Environmental Pollution 250 (2019) 746e753
Fig. 1. Comparison of particulate matter (PM) and ammonia (NH3) concentrations in high-rise nursery (HN) and high-rise fattening (HF) barns during the daytime from 7:00 to 19:00. Values are expressed as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001.
barns were far higher than the atmospheric PM concentration in Zunyi city based on the data reported online during the experimental period, which were 0.035 mg m 3 for PM2.5 and 0.064 mg m 3 for PM10. High ambient PM and NH3 concentrations could affect the concentrations inside the barns because these materials can be carried into the barns through their ventilation systems (Kaasik and Maasikmets, 2013). Although the ambient PM and NH3 concentrations were high, they were lower than those inside the two barns; this demonstrates that the pig farm is an important contributor of air pollutants to the ambient environment. The emission of NH3 from all the barns resulted in high NH3 concentrations outside the barns, which in turn affected the NH3 concentrations inside. The air quality inside and outside the barns shows mutual interaction. A comparison of the mean values of PM and NH3 concentrations is provided in Fig. 1. The concentration of TSP in the HF barn was significantly higher than that in the HN barn (P < 0.05). It has been reported that larger PM fractions originate mainly from manure pez et al., 2011b). Manure was the main source and feed (Cambra-Lo of NH3. More feed was provided to the fattening pigs, and they excreted more manure than the nursery pigs. The feed and dried manure on the concrete floor became the main contributors to larger PM (>10 mm) fractions in the air, and the presence of more manure and urine in the HF barn induced higher NH3 concentrations. 3.2.2. Comparison of PM and NH3 concentrations at different positions in the two barns The PM and NH3 concentrations at different sampling sites in the two barns are shown in Table 2. The concentrations of TSP detected at the 1.5 m monitoring position in the middle of the HN
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barn were significantly higher than those at the forepart and rear of the barn (P < 0.05), and the monitoring site at 1.0 m showed significantly higher TSP concentrations than the site in the rear (P < 0.05). There was no significant difference in NH3 concentration at different spatial positions, although the NH3 concentration in the rear was the lowest. In the HF barn, the TSP concentration was significantly higher at the forepart than in the rear (P < 0.05), where the TSP concentration was the lowest among all measurement sites. The NH3 concentrations were significantly lower in the rear of the barn than at the forepart and middle regions (P < 0.05). The fact that the concentrations of PM and NH3 were lowest at the rear of the two barns can be explained by the fact that the intake windows through which the fresh air entered were located in the rear of the barns. As reported in a published paper, ventilation is the major factor influencing in-house PM and NH3 concentrations (Ni et al., 2017). Large amounts of fresh air diluted the PM and NH3 concentrations in the rear of the barn, whereas the PM and NH3 accumulated easily in the middle and forepart of the barn. On the east and west sides of the HF barn, windows were also provided through which fresh air could enter; thus, the NH3 concentrations in these areas were also lower than that in the middle. The TSP and NH3 concentrations were higher in the HF barn than in the HN barn at all monitored sites. This is consistent with the results shown in Fig. 1. The more manure was stored and the more feed was used, the greater was the amount of suspended PM that was found (Lin et al., 2012).
3.2.3. The PM concentration variation during feeding As shown in Fig. 2, PM concentrations began to increase 15 min before feeding and reached their peak values of 2.51 mg m 3,
Fig. 2. Particulate matter (PM) concentration variation 15 min before and after feeding (mean ± SD). The negative sign indicates before feeding and 0:00 refers to the start of feeding.
Table 2 Spatial differences of particulate matter (PM) and ammonia (NH3) concentrations in high-rise nursery (HN) and high-rise fattening (HF) barns. Point
HN barn PM (mg$m
1.5 m 1.0 m 0.5 m forepart rear east west
HF barn 3
)
NH3 (mg$m
TSP
PM10
PM2.5
0.787 ± 0.1a 0.739 ± 0.1ab 0.723 ± 0.1abc 0.515 ± 0.2bc 0.475 ± 0.2c 0.634 ± 0.2abc 0.576 ± 0.2abc
0.473 ± 0.1 0.445 ± 0.1 0.401 ± 0.1 0.334 ± 0.08 0.312 ± 0.1 0.385 ± 0.1 0.366 ± 0.1
0.222 ± 0.07 0.217 ± 0.08 0.204 ± 0.09 0.203 ± 0.1 0.201 ± 0.1 0.203 ± 0.08 0.216 ± 0.1
12.7 ± 3 11.9 ± 3 10.5 ± 2 13.6 ± 4 9.87 ± 4 13.2 ± 3 13.5 ± 5
3
)
PM (mg$m
3
)
NH3 (mg$m
TSP
PM10
PM2.5
0.829 ± 0.3ab 0.840 ± 0.3ab 0.760 ± 0.3ab 0.884 ± 0.4a 0.618 ± 0.1b 0.771 ± 0.2ab 0.734 ± 0.2ab
0.360 ± 0.1 0.347 ± 0.1 0.351 ± 0.1 0.377 ± 0.1 0.272 ± 0.06 0.332 ± 0.2 0.329 ± 0.1
0.153 ± 0.07 0.152 ± 0.07 0.144 ± 0.07 0.175 ± 0.09 0.120 ± 0.06 0.136 ± 0.07 0.128 ± 0.06
3
)
40.3±9a 40.9±8a 41.0±8a 37.7±8ab 27.2±5cd 31.7±6bcd 27.1±6d
Note: The values are shown as the mean ± SEM based on 7 measurements per day for 6 d at each position. Values followed by different superscripted letters are significantly different between positions (P < 0.05); values followed by the same letters show no significant differences.
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Table 3 Pearson correlation coefficient values for temperature (T), relative humidity (RH), illumination (I), particulate matter (PM2.5, PM10 and TSP) and ammonia (NH3) concentrations in a high-rise nursery (HN) barn. Environmental parameter
T ( C)
RH (%)
RH (%) I (lx) TSP (mg$m 3) PM10 (mg$m 3) PM2.5 (mg$m 3) NH3 (mg$m 3)
0.0215 0.122 0.311* 0.0215 0.00899 0.480***
1
I (lx)
0.281* 0.0556 0.0241 0.735*** 0.0260
TSP (mg$m
3
)
3
PM10 (mg$m
)
PM2.5 (mg$m
3
)
1 0.398** 0.341** 0.175 0.154
Note: Asterisks indicate significant correlations between the measured variables. *P < 0.05,
1 0.704*** 0.192 0.349** **
P < 0.01,
***
1 0.249* 0.169
1 0.141
P < 0.001.
Table 4 Pearson correlation coefficient values for temperature (T), relative humidity (RH), illumination (I), particulate matter (PM2.5, PM10 and TSP) and ammonia (NH3) concentrations in a high-rise fattening (HF) barn. EP RH (%) I (lx) TSP (mg$m 3) PM10 (mg$m 3) PM2.5 (mg$m 3) NH3 (mg$m 3)
T ( C)
RH (%) **
0.631 0.353* 0.277* 0.304* 0.510** 0.0826
I (lx)
TSP (mg$m
3
)
PM10 (mg$m
3
)
PM2.5 (mg$m
3
)
1 0.418* 0.526** 0.590** 0.735*** 0.0734
1 0.055 0.221 0.380* 0.615**
1 0.756*** 0.594** 0.213
Note: Asterisks indicate significant correlations between the measured variables. *P < 0.05,
1.16 mg m 3 and 0.37 mg m 3 for TSP, PM10 and PM2.5, respectively, approximately 2 min after feeding. The level then decreased gradually, but some PM remained suspended in the air for a long period after feeding. The feed residue would be raised and suspended in the air by the activity of the pigs. It was also reported that animal and staff activities coincided with the higher PM concentrations in the barns (Ahmed et al., 2011). Strong indoor airflow could also resuspend the PM and prevent it from settling (Lin et al., 2012; Li et al., 2013).
3.3. Correlations Table 3 and Table 4 show the Pearson correlation coefficients among temperature, relative humidity, illumination, PM and NH3 inside the two barns. Indoor TSP, PM10 and PM2.5 concentrations were almost mutually significantly correlated in the two barns (P < 0.05), similar to a result reported in a previous study (Van Ransbeeck et al., 2013). Furthermore, the PM2.5 concentration was significantly positively correlated with the relative humidity in the HN barn (P < 0.05) and there was a significant negative correlation between TSP concentration and temperature in the HN barn (P < 0.05). It was also found by Vu cemilo et al. (2008) that increased temperature significantly reduced the indoor concentrations of PM2.5, PM10 and TSP; these authors pointed out that more ventilation would be provided as the temperature increased, leading to lower PM concentrations. The correlation between the PM2.5 concentration and the relative humidity inside the pig buildings was positive. Research in cowsheds has shown that a large proportion of liquid components, such as water vapour and compounds, can be contained in the fine PM fractions and that these fractions can also aggregate into larger particles in moist environments (Kaasik and Maasikmets, 2013). The NH3 concentrations were positively correlated with the concentrations of TSP in the HN barn (P < 0.05). This could be explained that part of NH3 can be adhered to the surface of PM. The temperature and NH3 concentrations in the HN barn were positively correlated. The NH3 was generated by microbial fermentation; a temperature above the optimal would stimulate NH3 production (Bluteau et al., 2009). There was a positive
**
P < 0.01,
***
1 0.698*** 0.144
1 0.0164
P < 0.001.
correlation between indoor temperature and illumination in the HF barn, while the correlation was not significant in the HN barn. This could be explained by the fact that the illumination and temperature were maintained at relatively stable levels in the HN barn to accommodate the special requirements of nursery pigs, whereas the illumination and temperature in the HF barn changed as the conditions outside varied. No correlation between the concentration of relative humidity and NH3 was detected. The correlations between environmental parameters inside and outside the two barns are shown in Table S2. In the HN barn, only the TSP was positively correlated with the level outside (P < 0.05), whereas in the HF barn both PM10 and PM2.5 were positively correlated with the levels outside (P < 0.01). The coarser particles settled more rapidly because of their heavier gravity, while the finer particles could be carried from the barn more easily along with the airflow, thus, the correlation between PM levels inside and outside the barn would be expected to be stronger for fine fractions (Kaasik and Maasikmets, 2013). The illumination inside the HF barn was significantly correlated with the illumination outside due to the presence of windows.
3.4. Ultrastructure of PM2.5 The PM2.5 suspended in the pig barns was a mixture of various elements and compounds. The PM can be divided into anthropogenic sources and natural sources such as soil dust and minerals. Fig. 3 shows a scanning electron micrograph of PM deposited on a glass fibre filter. In Fig. 3A, particles collected from the HN barn are magnified 2000 times. Fig. 3B illustrates the presence of roughly spherical and irregularly shaped particles in the PM collected from the HN barn. Based on the figures and descriptions in the work of pez et al. (2011a; 2011b), who collected feed, manure, Cambra-Lo skin, feather and hair particles from pig and poultry houses and analysed the shapes of PM obtained from different sources, this indicates that the source of the PM may have included manure and feed. A high percentage of irregularly shaped particles mainly derived from traffic abrasion and re-suspension processes, has also been reported (Satsangi and Yadav, 2014). The loose, smooth surfaces of the strip-, rod- and bar-shaped particles collected from the
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Fig. 3. Microscopic morphology of fine particulate matter (PM2.5) collected in the pig barns. A, particles collected from the HN barn and deposited on a glass fibre filter ( 2000); B, roughly spherical and irregularly shaped particles from the HN barn ( 10 000); C, smooth surface of the strip- and rod-shaped particles from the HF barn ( 20 000); D, Globular aggregated crystals and capsule-shaped particles from the HF barn ( 40 000).
HF barn are shown in Fig. 3C. These particles might be mineral particles similar to those shown in a published paper (Cambra pez et al., 2011b); one portion of these particles may be priLo marily derived from feed, and another portion may be derived from blowing dust outside the barn. In Fig. 3D, particles collected from the HF barn are shown to be an agglomerations consisting of many fine, spherical, fragmented angular particles with short chain structures, similar to another report (Yue et al., 2006). In general, smoke morphology also includes crystalline spherical particles depending on the type of fuel used, the combustion conditions and atmospheric processes. Smoke dust, mainly from the combustion of fossil fuels and incomplete combustion emissions, entered the barn through the air intake (Li et al., 2011). The household wastes in the experimental pig farm were treated by combustion, and this was regarded as a source of PM in the swine barns.
3.5. PM2.5 elemental composition analysis The PM2.5 elemental composition determined by SEM-EDS is shown in Fig. 4. The analysis of the elemental composition of the particles was conducted using 5 different particles collected on the filter. Table 5 shows that the highest mass fraction element in the particles was oxygen, the content of which was 40.30%, followed by C, Si, P, N, Zn, Mg, Na, Fe, Ca and K. The elements C, O, and Si have been reported to be the major constituents of feed and skin partipez et al., 2010), and dust blown from the soil is cles (Cambra-Lo also enriched in the elements O and Si. Combined with our morphological observations, this indicates that PM2.5 was mainly organic matter. Similar results were reported by Wagner et al. (2012) and Aarnink et al. (1999). It was speculated that the main sources of PM2.5 in swine barns are manure and feed, with a small
Fig. 4. SEM-EDS of particle samples (A). SEM micrographs were digitized, the images were processed, and primary feature data measurements were made (B).
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D. Shen et al. / Environmental Pollution 250 (2019) 746e753
Table 5 Chemical composition of particulate matte expressed as mass percentage. Spectrum
C
N
O
Na
Mg
Si
P
K
Ca
Fe
Zn
1 3 4 5 Mean value
18.5 21.4 35.8 31.4 24.9
5.96 e 8.99 10.8 7.83
45.0 40.2 37.6 37.7 40.3
0.810 0.940 1.31 1.05 1.08
3.98 e 0.200 0.00 1.34
15.8 30.4 15.4 19.1 19.8
9.69 e e e 8.83
0.230 0.370 e e 0.210
e 0.800 0.00 e 0.320
e 1.24 0.730 e 0.920
e 4.64 e e 5.45
Note: “-”indicates no detection.
contribution from fossil fuel combustion particles and blowing dust particles. 4. Conclusions The following conclusions are based on the observed factors and characteristics of PM and NH3 distribution in two enclosed highrise pig barns. The air quality outside the barn was better than that inside the pig houses. The indoor air quality in the rear of the barn was better than the air quality in other areas of the barn. The concentrations of TSP and NH3 in the fattening barn were significantly higher than those in the nursing barn. The PM concentrations gradually increased approximately 15 min before feeding, reached a maximum at feeding time, and then decreased. Feeding is a main factor that increased indoor PM concentrations. There was significant negative correlation of PM and NH3 concentrations with airflow speed. Indoor TSP, PM10 and PM2.5 concentrations are positively correlated with each other. Furthermore, the PM concentration was positively correlated with relative humidity, but negatively correlated with temperature. The PM is composed mainly of oxygen, carbon, silicon, phosphorus and nitrogen. It is speculated that the sources of PM2.5 in swine barns are blowing dust, feeds, mineral particles and smoke. Conflicts of interest The authors have no conflicts of interest to declare. Acknowledgments This study was supported by the National Key Research and Development Program of China (2016YFD0500505), the National Natural Science Foundation of China (No. 31772648) and Postgraduate Research & Practice Innovation Program of Jiangsu Province (SJCX17_0191). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.envpol.2019.04.086. References Aarnink, A.J.A., Roelofs, P.F.M.M., Ellen, H., Gunnink, H., 1999. Dust sources in animal houses. In: Proceedings of the International Symposium on Dust Control in Animal Production Facilities, 30 May-2 June. Aarhus (D), pp. 34e40. Ahmed, Z.A.M., Ghamdi, Z.H.E., Alnamshaan, M.M., 2011. Indoor air particulates in broiler environment during winter. Int. J. Poult. Sci. 10, 269e275. Arphorn, S., Ishimaru, T., Hara, K., Mahasandana, S., 2018. Considering the effects of ambient particulate matter on the lung function of motorcycle taxi drivers in Bangkok, Thailand. J. Air Waste Manag. Assoc. 68, 139e145. Banhazi, T.M., Seedorf, J., Rutley, D.L., Pitchford, W.S., 2008. Identification of risk factors for sub-optimal housing conditions in Australian piggeries: Part 2. Airborne pollutants. J. Agric. Saf. Health 14, 21e39. , D.I., Leduc, R., 2009. Ammonia emission rates from dairy Bluteau, C.V., Masse livestock buildings in eastern Canada. Biosyst. Eng. 103, 480e488. pez, M., Aarnink, A.J.A., Zhao, Y., Calvet, S., Torres, A.G., 2010. Airborne Cambra-Lo particulate matter from livestock production systems: a review of an air
pollution problem. Environ. Pollut. 158, 1e17. pez, M., Hermosilla, T., Lai, H.T.L., Aarnink, A.J.A., Ogink, N.W.M., 2011a. Cambra-Lo Particulate matter emitted from poultry and pig houses: source identification and quantification. T. Asabe 54, 629e642. pez, M., Torres, A.G., Aarnink, A.J.A., Ogink, N.W.M., 2011b. Source analCambra-Lo ysis of fine and coarse particulate matter from livestock houses. Atmos. Environ. 45, 694e707. Chen, Y., Lim, T.T., Heber, A.J., Ni, J.Q., 2011. Development of emission models for commercial swine finishing barns. 2011 Louisville, Kentucky, August 7 - August 10, 2011. Ellen, H.H., Bottcher, R.W., Wachenfelt, E.V., Takai, H., 2000. Dust levels and control methods in poultry houses. J. Agric. Saf. Health 6, 275. Feng, J., Yu, H., Liu, S., Su, X., Li, Y., Pan, Y., Sun, J., 2016. PM2.5 levels, chemical composition and health risk assessment in Xinxiang, a seriously air-polluted city in North China. Environ. Geochem. Hlth. 1e13. Heber, A.J., Lim, T.T., Ni, J.Q., Tao, P.C., 2006. Quality-assured measurements of animal building emissions: particulate matter concentrations. J. Air Waste Manag. Assoc. 56, 1642e1648. Kaasik, A., Maasikmets, M., 2013. Concentrations of airborne particulate matter, ammonia and carbon dioxide in large scale uninsulated loose housing cowsheds in Estonia. Biosyst. Eng. 114, 223e231. Kristensen, H.H., Wathes, C.M., 2000. Ammonia and poultry welfare: a review. World Poultry Sci. J. 56, 235e245. Kwon, K.S., Lee, I.B., Ha, T., 2016. Identification of key factors for dust generation in a nursery pig house and evaluation of dust reduction efficiency using a CFD technique. Biosyst. Eng. 151, 28e52. Lee, Y.Y., Lin, S.L., Yuan, C.S., Lin, M.Y., Chen, K.S., 2018. Reduction of atmospheric fine particle level by restricting the idling-vehicles around a sensitive area. J. Air Waste Manag. Assoc. 269, 172. Li, Q.F., Wang-Li, L., Wang, K., Chai, L., Cortus, E.L., Kilic, I., Bogan, B.W., Ni, J.Q., Heber, A.J., 2013. The national air emissions monitoring study's southeast layer site: Part II. Particulate matter. T. Asabe 56, 1173e1184. Li, W., Shao, L., Shen, R., Yang, S., Wang, Z., Tang, U., 2011. Internally mixed sea salt, soot, and sulfates at Macao, a coastal city in South China. J. Air Waste Manag. Assoc. 61, 1166e1173. Lin, X.J., Cortus, E.L., Zhang, R., Jiang, S., Heber, A.J., 2012. Ammonia, hydrogen sulfide, carbon dioxide and particulate matter emissions from California highrise layer houses. Atmos. Environ. 46, 81e91. Liu, S.L., Ni, J.Q., Radcliffe, J.S., Vonderohe, C.E., 2017. Mitigation of ammonia emissions from pig production using reduced dietary crude protein with amino acid supplementation. Bioresour. Technol. 233, 200e208. n, R.D.P., Sierens, A., Michiels, A., Piepers, S., Ulens, T., Van Ransbeeck, N., Sacrista Haesebrouck, F., Demeyer, P., Maes, D., 2015. Impact of particulate matter and ammonia on average daily weight gain, mortality and lung lesions in pigs. Prev. Vet. Med. 121, 99e107. Ministry of Agriculture of the People's Republic of China, 1999. NY/T 388-1999 Environmental Quality Standard for the Livestock and Poultry Farm (in Chinese). Ni, J.Q., Liu, S., Diehl, C.A., Lim, T.T., Bogan, B.W., Chen, L., Chai, L., Wang, K., Heber, A.J., 2017. Emission factors and characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter at two high-rise layer hen houses. Atmos. Environ. 154, 260e273. NRC, 2003. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs. The National Academies Press, Washington, DC. Qiu, L., Chen, M., Wang, X., Qin, X., Chen, S., Qian, Y., Liu, Z., Cao, Q., Ying, Z., 2017. Exposure to concentrated ambient PM2.5 compromises spermatogenesis in a mouse model: role of suppression of hypothalamus-pituitary-gonads axis. Toxicol. Sci. 162, 318e326. Ransbeeck, N.V., Langenhove, H.V., Demeyer, P., 2013. Indoor concentrations and emissions factors of particulate matter, ammonia and greenhouse gases for pig fattening facilities. Biosyst. Eng. 116, 518e528. Satsangi, P.G., Yadav, S., 2014. Characterization of PM2.5 by X-ray diffraction and scanning electron microscopyeenergy dispersive spectrometer: its relation with different pollution sources. Int. J. Environ. Sci. Te. 11, 217e232. Van Ransbeeck, N., Van Langenhove, H., Demeyer, P., 2013. Indoor concentrations and emissions factors of particulate matter, ammonia and greenhouse gases for pig fattening facilities. Biosyst. Eng. 116, 518e528. Vucemilo, M., Matkovi c, K., Vinkovi c, B., Macan, J., Varnai, V.M., Prester, L., Grani c, K., Orct, T., 2008. Effect of microclimate on the airborne dust and endotoxin concentration in a broiler house. Czech J. Anim. Sci. 53, 83e89. Wagner, J., Naik-Patel, K., Wall, S., Harnly, M., 2012. Measurement of ambient
D. Shen et al. / Environmental Pollution 250 (2019) 746e753 particulate matter concentrations and particle types near agricultural burns using electron microscopy and passive samplers. Atmos. Environ. 54, 260e271. Wang-Li, L., Cao, Z., Li, Q., Liu, Z., Beasley, D.B., 2013. Concentration and particle size distribution of particulate matter inside tunnel-ventilated high-rise layer operation houses. Atmos. Environ. 66, 8e16. WHO, 2000. Air Quality Guidelines, second ed. WHO Regional Publications, Copenhagen, Denmark, pp. 186e194. WHO, 2013. Health Effects of Particulate Matter. WHO Regional Office for Europe, Copenhagen, Denmark. Winkel, A., Mosquera, J., Koerkamp, P.W.G.G., Ogink, N.W.M., Aarnink, A.J.A., 2015. Emissions of particulate matter from animal houses in The Netherlands. Atmos. Environ. 111, 202e212.
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Distribution and physicochemical properties of particulate matter in swine confinement barns* Dan Shen 1, Sheng Wu 1, Zhaojian Li, Qian Tang, Pengyuan Dai, Yansen Li, Chunmei Li* National Experimental Teaching Demonstration Center of Animal Science, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 15 November 2018 Received in revised form 16 April 2019 Accepted 16 April 2019 Available online 17 April 2019
Air pollutants accumulated in confined livestock barns could impact the health of animals and staff. Particulate matter (PM) and ammonia (NH3) concentrations are typically high in enclosed livestock houses with weak ventilation. The objective of this study was to investigate the distribution of PM in different size fractions and the levels of NH3 in a high-rise nursery (HN) barn and a high-rise fattening (HF) barn on a swine farm and to analyse the physicochemical properties of fine PM (PM2.5, PM with aerodynamic diameter 2.5 mm). The concentrations of total suspended particles (TSP, PM with aerodynamic diameter 100 mm), inhalable PM (PM10, PM with aerodynamic diameter 10 mm), PM2.5 and NH3 were monitored continuously for 6 d in each barn. The results showed that the concentrations of PM and NH3 varied with position, they were significantly higher inside the barns than outside (P < 0.01) and significantly higher in the forepart than at the rear of the two barns (P < 0.05). In the HF barn, the values of the two parameters were 0.777 ± 0.2 mg m 3 and 26.7 ± 7 mg m 3, respectively, significantly higher than the values observed in the HN barn at all monitored sites (P < 0.05). The PM concentrations increased markedly during feeding time in the two barns. Chemical characteristics analysis revealed that the main sources of PM2.5 in the two barns may have consisted of blowing dust, feed, mineral particles and smoke. In conclusion, the air quality at the forepart was worse than that at the rear of the barns. Activities such as feeding could increase the PM concentrations. The components of PM2.5 in the two barns were probably blowing dust, feed, mineral particles and smoke from outside. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Swine confinement barn Particulate matter Ammonia Physicochemical property
1. Introduction In livestock production, intensive poultry and pig housing are the main sources of particulate matter (PM) and ammonia (NH3) emissions. Both PM and NH3 are two major pollutants in pig facilities environments (Wang-Li et al., 2013; Kristensen and Wathes, 2000), and concerns have been raised on their potential hazard to human health and the environment (Yao et al., 2018). High concentrations of PM, especially fine particulate matter (PM2.5, PM with aerodynamic diameter 2.5 mm), which may penetrate into the alveoli through the respiratory tract based on its small size, are considered a potential hazard to worker health and animal welfare (Arphorn et al., 2018; Lee et al., 2018). Recent studies have
*
This paper has been recommended for acceptance by Charles Wong. * Corresponding author. E-mail addresses: [email protected], [email protected] (C. Li). 1 Both the authors contributed equally to this work.
https://doi.org/10.1016/j.envpol.2019.04.086 0269-7491/© 2019 Elsevier Ltd. All rights reserved.
highlighted the role of ambient PM as an important environmental pollutant that is associated with many different cardiopulmonary diseases and with lung cancer. Gaseous pollutants, bacteria, and viruses could attach to the PM, which can be dispersed over long distances, and cause infectious and allergic diseases (Winkel et al., 2015). The PM2.5, one of the leading challenges to global public health, is well known to cause various adverse cardiopulmonary effects (Feng et al., 2016). Exposure to ambient PM2.5 can also induce dysfunction of the male reproductive system (Qiu et al., 2017). The respiratory health of finishing pigs was shown to be significantly affected by PM10 (Michiels et al., 2015), and nursery pigs are more sensitive to PM than fattening pigs because their immune systems are relatively weak (Yao et al., 2010). Although the health effects of PM have been well documented, there is no threshold level of PM concentration that is known to have no adverse health effects (WHO, 2013). Ammonia, another major pollutant in swine barns, is mainly released from manure, is a wellknown toxic gas that poses a potential health hazard to both producers and pigs (Banhazi et al., 2008). Increased NH3
D. Shen et al. / Environmental Pollution 250 (2019) 746e753
concentrations could result in a higher incidence of pleuritic lesions (Michiels et al., 2015). In addition, excessive NH3 can pollute the surrounding environment when released by the ventilating system, leading to acidification of the soil and nitrogen deposition in ecosystems (NRC, 2003). Globally, the livestock sector is responsible for approximately 65% of anthropogenic emissions of NH3, including energy consumption and land-use change. The concentrations of PM and NH3 in livestock houses are impacted by the type of housing system used, the ventilation rate, the animal species and the sampling method (Ellen et al., 2000). Other important factors include animal activity, stock density, temperature and relative humidity (Chen et al., 2011). Investigations of the indoor concentrations of PM and NH3 in different conventional pig-fattening facilities have shown that there is a strong correlation between PM emission rates and housing systems, ventilation rates and operation practices (Ransbeeck et al., 2013). Swine confinement buildings are becoming larger and more intensive due to increasing market demand, and the air pollution inside these buildings is getting worse. Some papers have reported PM concentrations, emission levels and key factors for PM generation in pig houses (Ransbeeck et al., 2013; Kwon et al., 2016). Knowledge of the distribution and preliminary source analysis of PM are also very important for controlling the PM concentration the swine confinement buildings, but there are few studies of PM spatial distribution or ultrastructural observation of PM2.5 in enclosed swine confinement buildings, and data on the effects of feeding and ventilation rate on PM generation, especially for swine confinement buildings, are sparse. The present study aimed to investigate the distribution of indoor PM and NH3 and to conduct an ultrastructural analysis of PM2.5 in high-rise nursery (HN) and high-rise fattening (HF) pig barns. The correlation of PM and NH3 concentrations with environmental parameters such as temperature, relative humidity, and illumination was also assessed. 2. Materials and methods 2.1. Swine facility The barns in this study are typical of those presently used in China and are located at a large-scale closed swine farm in Zunyi city of Guizhou province. A total of 30 fattening barns and 10 nursery barns are located at the farm; all are oriented in a northsouth direction and were built in 2011. One high-rise nursery barn and one fattening barn were selected as the experimental barns. The stocking population of nursery pigs and fattening pigs were 325 and 152 respectively, and each of the two barns was 26.0 m long and 15.0 m wide. Each house had a 2.0 m-high sidewall and a 1.2 m-high first-floor manure pit underneath the slatted floor where manure was stored for approximately 3 months (Fig. S1). There was no ventilation window in the HN barn, although it had a suspended ceiling; air flowed into the barn through 40 oblique adjustable air inlets in the ceiling (Fig. S2). The nursery pigs were 6 weeks old, and all weighed approximately 13 kg. The breeds were (Duroc Large Yorkshire Landrace) three hybrids. The barn was equipped with a mechanical ventilation system consisting of exhaust fans of type QYT-1530 installed in the north wall 0.8 m above the ground. The ventilation was controlled by exhaust fans which operated depending on the temperature inside the barn during the daytime from 8:00 to 20:00. All four fans were turned on when the temperature was higher than 24 C; when the temperature was lower than 23 C, only one fan was operated to maintain weak ventilation. The primary heating devices in the HN barn were model KD741 heat preservation lamps. There was only one shaft
747
door at the forepart of the barn, and this door was usually kept closed. In the HF barn, there were 4 small ventilation windows (L W: 90 45 cm) above the regular windows in the sidewall of the barn. The fattening pigs in the HF barn were approximately 130e150 kg in weight and 25 weeks old. There were 20 pens and 152 fattening pigs in the HF barn. The ventilation in this barn was also controlled by exhaust fans based on the temperature inside the barn, and the operation of the exhaust fan system was the same as that in the HN barn. There was no heat preservation lamp. The remaining devices were the same as those in the HN barn (Table S1). 2.2. Swine barn management Feeding arrangement: Nursery pigs were fed pelleted feed manually at 9:00 and 14:30; the total amount of feed was 0.5 kg daily each. Fattening pigs were fed 4.5 kg of pelleted feed once daily each at 10:00 using an automatic feeder. Ventilation management: Ceiling ventilation was used in the HN barn. The fans were turned on at 8:00 to adjust the ventilation. There were four small air intake windows in the end wall at the south side of the HF barn, which was ventilated via a combination of the ceiling vents and the air intake windows. The fans in the HF barn were turned on at 8:00, and the ventilation was regulated by the temperature control system. Lighting management: Both the lighting and the heat preservation lamps in the HN barn were turned on during the monitoring period (07:00e19:00), while only the lighting lamps were turned on in the HF barn. 2.3. Measurement strategy The environmental parameters were monitored from 1st to 12th April 2017. The PM (TSP, PM10 and PM2.5), NH3 concentrations, temperature, relative humidity and illumination were measured at different horizontal locations (east, west, forepart, rear and outside) at a height of 0.5 m and at different heights (0.5 m, 1.0 m and 1.5 m) in the middle of the barns (Fig. S1). Monitoring of each barn was performed from 07:00 to 19:00 at 2-h intervals for 6 d (7 times per day). The specific dates on which the measurements were made from 1st to 6th April in the HN barn and 7th to 12th April in the HF barn. The temperature and relative humidity in each barn were recorded at 30-min intervals during a 24-h period. The outside measuring site was 5 m from the entrance to the pig barn. The PM2.5 was collected inside the pig barns at a flow rate of 16.7 L min 1 for 12 h per day for 6 d and subjected to ultrastructural observation. 2.4. Monitoring equipment A BTPMeHS1 ambient air particle sampler (Dandong Baite Instrument Co., Ltd., Liaoning, China) was used to collect PM2.5 from the HN and HF barns. The sampler was set at a flow rate of 16.7 L min 1 for 12 h per day. Particulate samples were captured on prebaked quartz filters (47 mm diameter, Whatman Inc., Clifton, NJ, USA) and were stored at 20 C after sampling. Ultrastructural observation was conducted using a SU8010-type field scanning electron microscope (SEM, Hitachi, Tokyo, Japan) and the relative content of chemical elements were measured using an energy-dispersive X-ray spectroscope (EDS, Bruker, Germany) attached to the SEM. The PM concentrations in the two barns were measured using a DustTrak™ ІІ 8532 Handheld Aerosol Monitor (TSI Inc., Minnesota, USA). This direct-reading portable PM monitor operates on the principle of scattered light beams; it can detect PM at concentrations ranging from 0.001 to 150 mg m 3 and has a measurement accuracy of ±0.001 mg m 3. The software provided with monitors
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could also show the concentrations of PM2.5, PM10 and TSP. Concentrations of NH3 were continuously measured using a JK40-ІV portable gas detector (Ji Shun'an Technology Co., Ltd., Guangdong, China) that has a detection range of 0e100 ppm and an accuracy of ±3% (F.S). It was connected to an electrochemical sensor with a resolution of ±0.01 ppm. Eight RC-4HC temperature and relative humidity recorders (Jingchuang Electric Co., Ltd., Jiangsu, China) with measurement accuracies of ±0.5 C and ±3% RH were used simultaneously to record the temperature and relative humidity at various locations within the barns. An LX-101 light illumination meter (Luchang Electric Co., Ltd.) was used to record illumination in the barns. All instruments were calibrated according to the manufacturer's instructions prior to measurement. Airflow speed in barns is regarded as a key environmental parameter that has important effects on the concentrations of PM, gases and other components. Airflow speed was also measured using a DEM6 three-cup wind anemometer (Tianjin Meteorological Instrument Factory, Tianjin, China) in this work; unfortunately, data on weak airflow speed were not obtained. 2.5. Data analysis The data were statistically analysed using GraphPad Prism 6.0 software, which is designed and marketed specifically for use in scientific graphing and statistical analysis. Difference analysis was performed using ANOVA; P values less than 0.05 (P < 0.05) or 0.01 (P < 0.01) were taken to indicate statistically significant differences. If the difference was significant, the LSD method was used for multiple comparisons. The test results are expressed as “mean ± standard deviation (SD)”. Pearson correlation coefficients were calculated to quantify the correlations between environmental parameters. 3. Results and discussion 3.1. Temperature and relative humidity As shown in Fig. S3 and Fig. S4, the temperature in the HN and HF barns ranged from 23.2 C to 26.1 C and 21.7 Ce24.6 C, respectively. The relative humidity in the two barns was 67.2%e 77.5% and 70.6%e75.5%, respectively. The temperature and humidity in the two barns were maintained in the relatively optimum range by light management, the housing system and the ventilation method. The temperature in the HN barn was higher than that in the HF barn because the optimal temperature for weanling nursery pigs is approximately 26 Ce28 C. The average temperature and relative humidity outside the barns were 14.2 C and 66.7%, respectively; thus, the temperature outside was lower than the indoor temperature. The great variation in the temperature inside the HF barn may be related to the local weather, which varied greatly. The relatively small variation in the temperature inside the HN barn might be due to better heat preservation in that facility.
3.2. Particulate matter and ammonia concentrations 3.2.1. PM and NH3 concentrations in nursery and fattening barns The mean TSP, PM10, PM2.5 and NH3 concentrations in the two barns are shown in Table 1. The mean concentrations of TSP, PM10 and PM2.5 inside the HN barn were 0.635 ± 0.1 mg m 3, 0.388 ± 0.09 mg m 3 and 0.210 ± 0.09 mg m 3, respectively. Another study reported that a mechanically ventilated nursery barn with a structure similar to the barn studied in this work had higher PM concentrations, approximately 1.5 mg m 3 for TSP and 1 mg m 3 for PM10. This difference may have been caused by the stocking density, which was 1.2 head$m 2 in this study and 2.2 head$m 2 in the barn that yielded the peak value in the published paper (Kwon et al., 2016). The mean NH3 concentration in the experimental HN barn was 12.2 ± 3 mg m 3. A previous paper reported that nursery barns equipped with variable-speed pit fans that directly exhaust the air from manure pits, had a low NH3 concentration of approximately 3 mg m 3. Another important factor that may have affected the NH3 concentration was the stocking density, which was 1.18 head$m 2 in the reported paper, lower than that in the present study (Liu et al., 2017). The measured levels inside the HF barn were 0.777 ± 0.2 mg m 3 for TSP, 0.338 ± 0.1 mg m 3 for PM10 and 0.144 ± 0.06 mg m 3 for PM2.5. In another study, the measured TSP concentration in an ordinary barn was higher (1.14 ± 0.6 mg m 3) than the TSP concentration observed here, whereas it was lower (0.375 ± 0.2 mg m 3) when the finishing barn was treated with daily soybean oil sprinkling (Heber et al., 2006). The PM10 concentration in the present study was lower than reported for other fattening barns, in which it ranged from 0.459 to 1.75 mg m 3. This maybe because there was only one ventilator in the barn described in the reported paper, and inadequate ventilation may have led to the accumulation of PM. However, this result is not consistent with the PM2.5 concentration, which was higher in this study than has been reported for other fattening barns (Ransbeeck et al., 2013). This might be due to the high PM2.5 concentration outside the barns, which was even higher than that inside the abovementioned barns. The average concentration of NH3 in the HF barn was 26.7 mg m 3, which is among the highest levels reported in related studies (Ransbeeck et al., 2013; Liu et al., 2017). The gaps in the slatted concrete were slightly too narrow to allow faeces to drop fully in the HF barn; therefore, some faeces were stored on the concrete slats during this experiment. This may explain why the NH3 concentration was so high. It exceeded the standard of 25 mg m 3 set forth in NY/T 388e1999 “Environmental quality standard for the livestock and poultry farm” (The Ministry of Agriculture of the People's Republic of China, 1999), indicating a potential health hazard to the fattening pigs. It was shown that the concentration of PM2.5 outside exceeded both the air quality guideline of 0.025 mg m 3 recommended by WHO (2000) and the second standard concentration of 0.075 mg m 3 in China. The PM2.5 and PM10 concentrations near the
Table 1 Levels of particulate matter (PM) and ammonia (NH3) in high-rise nursery (HN) and high-rise fattening (HF) barns. Item HN
HF
Outside
TSP (mg$m Mean ± SD Max Min Mean ± SD Max Min Mean ± SD Max Min
0.635 ± 0.1 1.08 0.228 0.777 ± 0.2 2.18 0.307 0.163 ± 0.1 0.371 0.0310
3
)
PM10 (mg$m 0.388 ± 0.09 0.658 0.152 0.338 ± 0.1 0.835 0.116 0.111 ± 0.07 0.226 0.0180
3
)
PM2.5 (mg$m 0.210 ± 0.09 0.415 0.0950 0.144 ± 0.06 0.374 0.0380 0.0880 ± 0.05 0.185 0.00400
3
)
NH3 (mg$m 12.2 ± 3 20.6 3.12 26.7 ± 7 45.9 14.3 2.27 ± 1 6.60 1.66
3
)
D. Shen et al. / Environmental Pollution 250 (2019) 746e753
Fig. 1. Comparison of particulate matter (PM) and ammonia (NH3) concentrations in high-rise nursery (HN) and high-rise fattening (HF) barns during the daytime from 7:00 to 19:00. Values are expressed as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001.
barns were far higher than the atmospheric PM concentration in Zunyi city based on the data reported online during the experimental period, which were 0.035 mg m 3 for PM2.5 and 0.064 mg m 3 for PM10. High ambient PM and NH3 concentrations could affect the concentrations inside the barns because these materials can be carried into the barns through their ventilation systems (Kaasik and Maasikmets, 2013). Although the ambient PM and NH3 concentrations were high, they were lower than those inside the two barns; this demonstrates that the pig farm is an important contributor of air pollutants to the ambient environment. The emission of NH3 from all the barns resulted in high NH3 concentrations outside the barns, which in turn affected the NH3 concentrations inside. The air quality inside and outside the barns shows mutual interaction. A comparison of the mean values of PM and NH3 concentrations is provided in Fig. 1. The concentration of TSP in the HF barn was significantly higher than that in the HN barn (P < 0.05). It has been reported that larger PM fractions originate mainly from manure pez et al., 2011b). Manure was the main source and feed (Cambra-Lo of NH3. More feed was provided to the fattening pigs, and they excreted more manure than the nursery pigs. The feed and dried manure on the concrete floor became the main contributors to larger PM (>10 mm) fractions in the air, and the presence of more manure and urine in the HF barn induced higher NH3 concentrations. 3.2.2. Comparison of PM and NH3 concentrations at different positions in the two barns The PM and NH3 concentrations at different sampling sites in the two barns are shown in Table 2. The concentrations of TSP detected at the 1.5 m monitoring position in the middle of the HN
749
barn were significantly higher than those at the forepart and rear of the barn (P < 0.05), and the monitoring site at 1.0 m showed significantly higher TSP concentrations than the site in the rear (P < 0.05). There was no significant difference in NH3 concentration at different spatial positions, although the NH3 concentration in the rear was the lowest. In the HF barn, the TSP concentration was significantly higher at the forepart than in the rear (P < 0.05), where the TSP concentration was the lowest among all measurement sites. The NH3 concentrations were significantly lower in the rear of the barn than at the forepart and middle regions (P < 0.05). The fact that the concentrations of PM and NH3 were lowest at the rear of the two barns can be explained by the fact that the intake windows through which the fresh air entered were located in the rear of the barns. As reported in a published paper, ventilation is the major factor influencing in-house PM and NH3 concentrations (Ni et al., 2017). Large amounts of fresh air diluted the PM and NH3 concentrations in the rear of the barn, whereas the PM and NH3 accumulated easily in the middle and forepart of the barn. On the east and west sides of the HF barn, windows were also provided through which fresh air could enter; thus, the NH3 concentrations in these areas were also lower than that in the middle. The TSP and NH3 concentrations were higher in the HF barn than in the HN barn at all monitored sites. This is consistent with the results shown in Fig. 1. The more manure was stored and the more feed was used, the greater was the amount of suspended PM that was found (Lin et al., 2012).
3.2.3. The PM concentration variation during feeding As shown in Fig. 2, PM concentrations began to increase 15 min before feeding and reached their peak values of 2.51 mg m 3,
Fig. 2. Particulate matter (PM) concentration variation 15 min before and after feeding (mean ± SD). The negative sign indicates before feeding and 0:00 refers to the start of feeding.
Table 2 Spatial differences of particulate matter (PM) and ammonia (NH3) concentrations in high-rise nursery (HN) and high-rise fattening (HF) barns. Point
HN barn PM (mg$m
1.5 m 1.0 m 0.5 m forepart rear east west
HF barn 3
)
NH3 (mg$m
TSP
PM10
PM2.5
0.787 ± 0.1a 0.739 ± 0.1ab 0.723 ± 0.1abc 0.515 ± 0.2bc 0.475 ± 0.2c 0.634 ± 0.2abc 0.576 ± 0.2abc
0.473 ± 0.1 0.445 ± 0.1 0.401 ± 0.1 0.334 ± 0.08 0.312 ± 0.1 0.385 ± 0.1 0.366 ± 0.1
0.222 ± 0.07 0.217 ± 0.08 0.204 ± 0.09 0.203 ± 0.1 0.201 ± 0.1 0.203 ± 0.08 0.216 ± 0.1
12.7 ± 3 11.9 ± 3 10.5 ± 2 13.6 ± 4 9.87 ± 4 13.2 ± 3 13.5 ± 5
3
)
PM (mg$m
3
)
NH3 (mg$m
TSP
PM10
PM2.5
0.829 ± 0.3ab 0.840 ± 0.3ab 0.760 ± 0.3ab 0.884 ± 0.4a 0.618 ± 0.1b 0.771 ± 0.2ab 0.734 ± 0.2ab
0.360 ± 0.1 0.347 ± 0.1 0.351 ± 0.1 0.377 ± 0.1 0.272 ± 0.06 0.332 ± 0.2 0.329 ± 0.1
0.153 ± 0.07 0.152 ± 0.07 0.144 ± 0.07 0.175 ± 0.09 0.120 ± 0.06 0.136 ± 0.07 0.128 ± 0.06
3
)
40.3±9a 40.9±8a 41.0±8a 37.7±8ab 27.2±5cd 31.7±6bcd 27.1±6d
Note: The values are shown as the mean ± SEM based on 7 measurements per day for 6 d at each position. Values followed by different superscripted letters are significantly different between positions (P < 0.05); values followed by the same letters show no significant differences.
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Table 3 Pearson correlation coefficient values for temperature (T), relative humidity (RH), illumination (I), particulate matter (PM2.5, PM10 and TSP) and ammonia (NH3) concentrations in a high-rise nursery (HN) barn. Environmental parameter
T ( C)
RH (%)
RH (%) I (lx) TSP (mg$m 3) PM10 (mg$m 3) PM2.5 (mg$m 3) NH3 (mg$m 3)
0.0215 0.122 0.311* 0.0215 0.00899 0.480***
1
I (lx)
0.281* 0.0556 0.0241 0.735*** 0.0260
TSP (mg$m
3
)
3
PM10 (mg$m
)
PM2.5 (mg$m
3
)
1 0.398** 0.341** 0.175 0.154
Note: Asterisks indicate significant correlations between the measured variables. *P < 0.05,
1 0.704*** 0.192 0.349** **
P < 0.01,
***
1 0.249* 0.169
1 0.141
P < 0.001.
Table 4 Pearson correlation coefficient values for temperature (T), relative humidity (RH), illumination (I), particulate matter (PM2.5, PM10 and TSP) and ammonia (NH3) concentrations in a high-rise fattening (HF) barn. EP RH (%) I (lx) TSP (mg$m 3) PM10 (mg$m 3) PM2.5 (mg$m 3) NH3 (mg$m 3)
T ( C)
RH (%) **
0.631 0.353* 0.277* 0.304* 0.510** 0.0826
I (lx)
TSP (mg$m
3
)
PM10 (mg$m
3
)
PM2.5 (mg$m
3
)
1 0.418* 0.526** 0.590** 0.735*** 0.0734
1 0.055 0.221 0.380* 0.615**
1 0.756*** 0.594** 0.213
Note: Asterisks indicate significant correlations between the measured variables. *P < 0.05,
1.16 mg m 3 and 0.37 mg m 3 for TSP, PM10 and PM2.5, respectively, approximately 2 min after feeding. The level then decreased gradually, but some PM remained suspended in the air for a long period after feeding. The feed residue would be raised and suspended in the air by the activity of the pigs. It was also reported that animal and staff activities coincided with the higher PM concentrations in the barns (Ahmed et al., 2011). Strong indoor airflow could also resuspend the PM and prevent it from settling (Lin et al., 2012; Li et al., 2013).
3.3. Correlations Table 3 and Table 4 show the Pearson correlation coefficients among temperature, relative humidity, illumination, PM and NH3 inside the two barns. Indoor TSP, PM10 and PM2.5 concentrations were almost mutually significantly correlated in the two barns (P < 0.05), similar to a result reported in a previous study (Van Ransbeeck et al., 2013). Furthermore, the PM2.5 concentration was significantly positively correlated with the relative humidity in the HN barn (P < 0.05) and there was a significant negative correlation between TSP concentration and temperature in the HN barn (P < 0.05). It was also found by Vu cemilo et al. (2008) that increased temperature significantly reduced the indoor concentrations of PM2.5, PM10 and TSP; these authors pointed out that more ventilation would be provided as the temperature increased, leading to lower PM concentrations. The correlation between the PM2.5 concentration and the relative humidity inside the pig buildings was positive. Research in cowsheds has shown that a large proportion of liquid components, such as water vapour and compounds, can be contained in the fine PM fractions and that these fractions can also aggregate into larger particles in moist environments (Kaasik and Maasikmets, 2013). The NH3 concentrations were positively correlated with the concentrations of TSP in the HN barn (P < 0.05). This could be explained that part of NH3 can be adhered to the surface of PM. The temperature and NH3 concentrations in the HN barn were positively correlated. The NH3 was generated by microbial fermentation; a temperature above the optimal would stimulate NH3 production (Bluteau et al., 2009). There was a positive
**
P < 0.01,
***
1 0.698*** 0.144
1 0.0164
P < 0.001.
correlation between indoor temperature and illumination in the HF barn, while the correlation was not significant in the HN barn. This could be explained by the fact that the illumination and temperature were maintained at relatively stable levels in the HN barn to accommodate the special requirements of nursery pigs, whereas the illumination and temperature in the HF barn changed as the conditions outside varied. No correlation between the concentration of relative humidity and NH3 was detected. The correlations between environmental parameters inside and outside the two barns are shown in Table S2. In the HN barn, only the TSP was positively correlated with the level outside (P < 0.05), whereas in the HF barn both PM10 and PM2.5 were positively correlated with the levels outside (P < 0.01). The coarser particles settled more rapidly because of their heavier gravity, while the finer particles could be carried from the barn more easily along with the airflow, thus, the correlation between PM levels inside and outside the barn would be expected to be stronger for fine fractions (Kaasik and Maasikmets, 2013). The illumination inside the HF barn was significantly correlated with the illumination outside due to the presence of windows.
3.4. Ultrastructure of PM2.5 The PM2.5 suspended in the pig barns was a mixture of various elements and compounds. The PM can be divided into anthropogenic sources and natural sources such as soil dust and minerals. Fig. 3 shows a scanning electron micrograph of PM deposited on a glass fibre filter. In Fig. 3A, particles collected from the HN barn are magnified 2000 times. Fig. 3B illustrates the presence of roughly spherical and irregularly shaped particles in the PM collected from the HN barn. Based on the figures and descriptions in the work of pez et al. (2011a; 2011b), who collected feed, manure, Cambra-Lo skin, feather and hair particles from pig and poultry houses and analysed the shapes of PM obtained from different sources, this indicates that the source of the PM may have included manure and feed. A high percentage of irregularly shaped particles mainly derived from traffic abrasion and re-suspension processes, has also been reported (Satsangi and Yadav, 2014). The loose, smooth surfaces of the strip-, rod- and bar-shaped particles collected from the
D. Shen et al. / Environmental Pollution 250 (2019) 746e753
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Fig. 3. Microscopic morphology of fine particulate matter (PM2.5) collected in the pig barns. A, particles collected from the HN barn and deposited on a glass fibre filter ( 2000); B, roughly spherical and irregularly shaped particles from the HN barn ( 10 000); C, smooth surface of the strip- and rod-shaped particles from the HF barn ( 20 000); D, Globular aggregated crystals and capsule-shaped particles from the HF barn ( 40 000).
HF barn are shown in Fig. 3C. These particles might be mineral particles similar to those shown in a published paper (Cambra pez et al., 2011b); one portion of these particles may be priLo marily derived from feed, and another portion may be derived from blowing dust outside the barn. In Fig. 3D, particles collected from the HF barn are shown to be an agglomerations consisting of many fine, spherical, fragmented angular particles with short chain structures, similar to another report (Yue et al., 2006). In general, smoke morphology also includes crystalline spherical particles depending on the type of fuel used, the combustion conditions and atmospheric processes. Smoke dust, mainly from the combustion of fossil fuels and incomplete combustion emissions, entered the barn through the air intake (Li et al., 2011). The household wastes in the experimental pig farm were treated by combustion, and this was regarded as a source of PM in the swine barns.
3.5. PM2.5 elemental composition analysis The PM2.5 elemental composition determined by SEM-EDS is shown in Fig. 4. The analysis of the elemental composition of the particles was conducted using 5 different particles collected on the filter. Table 5 shows that the highest mass fraction element in the particles was oxygen, the content of which was 40.30%, followed by C, Si, P, N, Zn, Mg, Na, Fe, Ca and K. The elements C, O, and Si have been reported to be the major constituents of feed and skin partipez et al., 2010), and dust blown from the soil is cles (Cambra-Lo also enriched in the elements O and Si. Combined with our morphological observations, this indicates that PM2.5 was mainly organic matter. Similar results were reported by Wagner et al. (2012) and Aarnink et al. (1999). It was speculated that the main sources of PM2.5 in swine barns are manure and feed, with a small
Fig. 4. SEM-EDS of particle samples (A). SEM micrographs were digitized, the images were processed, and primary feature data measurements were made (B).
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Table 5 Chemical composition of particulate matte expressed as mass percentage. Spectrum
C
N
O
Na
Mg
Si
P
K
Ca
Fe
Zn
1 3 4 5 Mean value
18.5 21.4 35.8 31.4 24.9
5.96 e 8.99 10.8 7.83
45.0 40.2 37.6 37.7 40.3
0.810 0.940 1.31 1.05 1.08
3.98 e 0.200 0.00 1.34
15.8 30.4 15.4 19.1 19.8
9.69 e e e 8.83
0.230 0.370 e e 0.210
e 0.800 0.00 e 0.320
e 1.24 0.730 e 0.920
e 4.64 e e 5.45
Note: “-”indicates no detection.
contribution from fossil fuel combustion particles and blowing dust particles. 4. Conclusions The following conclusions are based on the observed factors and characteristics of PM and NH3 distribution in two enclosed highrise pig barns. The air quality outside the barn was better than that inside the pig houses. The indoor air quality in the rear of the barn was better than the air quality in other areas of the barn. The concentrations of TSP and NH3 in the fattening barn were significantly higher than those in the nursing barn. The PM concentrations gradually increased approximately 15 min before feeding, reached a maximum at feeding time, and then decreased. Feeding is a main factor that increased indoor PM concentrations. There was significant negative correlation of PM and NH3 concentrations with airflow speed. Indoor TSP, PM10 and PM2.5 concentrations are positively correlated with each other. Furthermore, the PM concentration was positively correlated with relative humidity, but negatively correlated with temperature. The PM is composed mainly of oxygen, carbon, silicon, phosphorus and nitrogen. It is speculated that the sources of PM2.5 in swine barns are blowing dust, feeds, mineral particles and smoke. Conflicts of interest The authors have no conflicts of interest to declare. Acknowledgments This study was supported by the National Key Research and Development Program of China (2016YFD0500505), the National Natural Science Foundation of China (No. 31772648) and Postgraduate Research & Practice Innovation Program of Jiangsu Province (SJCX17_0191). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.envpol.2019.04.086. References Aarnink, A.J.A., Roelofs, P.F.M.M., Ellen, H., Gunnink, H., 1999. Dust sources in animal houses. In: Proceedings of the International Symposium on Dust Control in Animal Production Facilities, 30 May-2 June. Aarhus (D), pp. 34e40. Ahmed, Z.A.M., Ghamdi, Z.H.E., Alnamshaan, M.M., 2011. Indoor air particulates in broiler environment during winter. Int. J. Poult. Sci. 10, 269e275. Arphorn, S., Ishimaru, T., Hara, K., Mahasandana, S., 2018. Considering the effects of ambient particulate matter on the lung function of motorcycle taxi drivers in Bangkok, Thailand. J. Air Waste Manag. Assoc. 68, 139e145. Banhazi, T.M., Seedorf, J., Rutley, D.L., Pitchford, W.S., 2008. Identification of risk factors for sub-optimal housing conditions in Australian piggeries: Part 2. Airborne pollutants. J. Agric. Saf. Health 14, 21e39. , D.I., Leduc, R., 2009. Ammonia emission rates from dairy Bluteau, C.V., Masse livestock buildings in eastern Canada. Biosyst. Eng. 103, 480e488. pez, M., Aarnink, A.J.A., Zhao, Y., Calvet, S., Torres, A.G., 2010. Airborne Cambra-Lo particulate matter from livestock production systems: a review of an air
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