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Ziyuan Zhou - One of the best experts on this subject based on the ideXlab platform.
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Associations of ambient air Pollutant Exposure with seminal plasma MDA, sperm mtDNA copy number, and mtDNA integrity.
Environment international, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p
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associations of ambient air Pollutant Exposure with seminal plasma mda sperm mtdna copy number and mtdna integrity
Environment International, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p < 0.001) (medians with 5th and 95th percentiles). There were no significant differences in sperm mtDNA copy number and mtDNA integrity between the two campuses. Furthermore, daily average PM10 Exposure during 0-90 days before semen ejaculation was found to be significantly and positively associated with seminal plasma MDA level (10.4; 95% CI, 4.4, 16.4) (percentage change per 10-unit increase in air Pollutant concentration; same meanings for the results below); daily average SO2 Exposure for 70-90 days and NO2 Exposure for 0-9 days prior to sampling were also positively associated with MDA level (74.7; 95% CI, 32.1, 119 and 11.9; 95% CI, 4.8, 19.0, respectively). AQI for 0-90 days and 70-90 days prior to sampling positively correlated with seminal plasma MDA concentrations (11.4; 95% CI, 4.7, 18.1 and 12.2; 95% CI, 5.3, 19.1, respectively). Additionally, daily average SO2 Exposures for 10-14 and 0-9 days prior to sampling were negatively associated with sperm mtDNA copy number and mtDNA integrity, respectively (-9.0; 95% CI, -16.4, -1.6 and -38.3; 95% CI, -64.1, -11.8, respectively). However, only the correlations between SO2 Exposure and AQI value for 70-90 days prior to sampling and MDA levels remained significant after multiplicity adjustment. CONCLUSIONS The results indicate that bad air quality, especially SO2 Exposure during certain periods of sperm development, might be correlated with oxidative damage to sperm. These findings can deepen the understanding of the potential impacts of air pollution on sperm quality.
Jian Hang - One of the best experts on this subject based on the ideXlab platform.
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the influence of solar natural heating and nox o3 photochemistry on flow and reactive Pollutant Exposure in 2d street canyons
Science of The Total Environment, 2021Co-Authors: Jiarui Liu, Xuemei Wang, Guanwen Chen, Qun Wang, Shuhang Cui, Yong Zhang, Peng Gao, Jian HangAbstract:Abstract This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-e model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) Pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106–107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate Pollutant Exposure in near-road buildings. As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 Exposure is generally about 40%–380% larger than passive CO Exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2–3 K and influences chemical rate slightly, thus this impact on reactive Pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.
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The influence of solar natural heating and NO x -O 3 photochemistry on flow and reactive Pollutant Exposure in 2D street canyons.
The Science of the total environment, 2020Co-Authors: Jiarui Liu, Xuemei Wang, Guanwen Chen, Qun Wang, Shuhang Cui, Yong Zhang, Peng Gao, Jian HangAbstract:Abstract This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-e model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) Pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106–107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate Pollutant Exposure in near-road buildings. As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 Exposure is generally about 40%–380% larger than passive CO Exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2–3 K and influences chemical rate slightly, thus this impact on reactive Pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.
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Numerical studies of passive and reactive Pollutant dispersion in high-density urban models with various building densities and height variations
Building and Environment, 2020Co-Authors: Yong Zhang, Xuemei Wang, Jiarui Liu, Peng Gao, Lan Chen, Hualiang Lin, Jian HangAbstract:Abstract Vehicular Pollutant Exposure in the near-road buildings of high-density urban areas has been rarely studied. This paper investigates the impacts of high-density building morphology on passive (CO) and reactive (NOx-O3) Pollutant dispersion in three-dimensional (3D) urban-like models, e.g. medium (street width W = 30 m,λp = 0.25, λf = 0.6) and compact (W = 18 m,λp = 0.39,λf = 0.94) layouts with uniform (H = 72 m) or various heights (H1 = 48 m,H2 = 96 m). Personal intake fraction P_iF and its spatially-averaged value for the entire building wall ( W) are utilized for Exposure assessment. Some meaningful findings are proposed: 1) When wind blows through neighborhood-scale (~1 km) urban models, it decelerates rapidly and then reaches a flow balance where pedestrian-level velocity and Pollutant Exposure vary depending on building densities and height variations. 2) Uniform-height cases attain overall W of ~0.3–1.3 ppm in target streets. The compact layout (λf = 0.94) experiences weaker vertical exchange where downward helical flows transport more Pollutants to windward wall than medium-type (λf = 0.6), inducing two-order larger windward-side W (~1 ppm) than leeward-side (~0.01 ppm). 3) Building height variations obtain greater velocity and smaller W (~0.2–1.0 ppm) in front of taller buildings than those behind them ( W~2.6–4.2 ppm). 4) No matter with or without height variations, densifying building arrays (λf = 0.6 to 0.94) raises windward-side W and mitigates leeward-side W, but overall W for both sides of target streets only change slightly. 5) With present NOx-O3 photochemistry (source emissions NO:NO2 = 10:1, background [O3] = 20 ppbv), NO2 Exposure is 40%–230% larger than passive CO Exposure, but NO is near to CO. This study implies the near-road Pollutant Exposure in high-density urban models is sensitive to building morphology which should be carefully designed.
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The influence of aspect ratios and wall heating conditions on flow and passive Pollutant Exposure in 2D typical street canyons
Building and Environment, 2020Co-Authors: Jian Hang, Yuanyuan Lin, Xieyuan Chen, Guanwen Chen, Taihan Chen, Zhiwen Luo, Xuelin Zhang, Qun WangAbstract:Abstract Deep street canyons and unfavourable meteorological conditions usually induce high Pollutant Exposure. Validated by experimental data, this paper employs computational fluid dynamic simulations with RNG k-e model to investigate the flow, and passive Pollutant dispersion within scale-model two-dimensional street canyons(H = 3 m). As a novelty, this paper quantifies the impacts of various wall heating scenarios(bottom, leeward/windward wall and all-wall heating), ambient velocity(Uref = 0.5–2 m s−1, Froude numbers Fr = 0.25–4.08, Reynolds numbers Re = 95602–382409) and aspect ratios(building height/street width, AR = 0.5, 0.67, 1, 2, 3) on personal intake fraction for entire streets( ). The governing equations are implicitly discretized by a finite volume method (FVM) and the second-order upwind scheme with Boussinesq model for quantifying buoyancy effects. The SIMPLE scheme is adopted for the pressure and velocity coupling. In most isothermal cases, one-main-vortex structure exists as AR = 0.5–3( = 0.43–3.96 ppm and 1.66–27.51 ppm with Uref = 2 and 0.5 m s−1). For non-isothermal cases with Fr = 4.08(Uref = 2 m s−1), wind-driven force dominates urban airflow as AR = 0.5–1 and four heating conditions attain similar (0.39–0.43 ppm, 0.57–0.60 ppm, 0.91–0.98 ppm). As AR = 2, windward and all-wall heating get two-vortex structures with greater (3.18–3.33 ppm) than others( = 2.13–2.21 ppm). As AR = 3, leeward-wall heating slightly reduces (~3.72–3.96 ppm), but the other three produce two-vortex structures with greater (6.13–10.32 ppm). As Fr = 0.25(Uref = 0.5 m s−1), leeward-wall heating always attains smaller (1.20–7.10 ppm) than isothermal cases(1.66–27.51 ppm) as AR = 0.5–3, however the influence of the other three is complicated which sometimes raises or reduces . Overall, smaller background wind speed (Fr = 0.25) with two-vortex structures attains much larger . Special attention is required at night(all-wall heating), noon(bottom-heating) and cloudy period(no-wall heating) as AR = 2–3, while it is during windward-wall heating and cloudy period for AR = 0.5–1.
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the impact of urban open space and lift up building design on building intake fraction and daily Pollutant Exposure in idealized urban models
Science of The Total Environment, 2018Co-Authors: Chenyuan Sha, Xuemei Wang, Yuanyuan Lin, Yifan Fan, Xi Chen, Jian HangAbstract:Abstract Sustainable urban design is an effective way to improve urban ventilation and reduce vehicular Pollutant Exposure to urban residents. This paper investigated the impacts of urban open space and ‘lift-up’ building design on vehicular CO (carbon monoxide) Exposure in typical three-dimensional (3D) urban canopy layer (UCL) models under neutral atmospheric conditions. The building intake fraction (IF) represents the fraction of total vehicular Pollutant emissions inhaled by residents when they stay at home. The building daily CO Exposure (Et) means the extent of human beings' contact with CO within one day indoor at home. Computational fluid dynamics (CFD) simulations integrating with these two concepts were performed to solve turbulent flow and assess vehicular CO Exposure to urban residents. CFD technique with the standard k-e model was successfully validated by wind tunnel data. The initial numerical UCL model consists of 5-row and 5-column (5 × 5) cubic buildings (building height H = street width W = 30 m) with four approaching wind directions (θ = 0°, 15°, 30°, 45°). In Group I, one of the 25 building models is removed to attain urban open space settings. In Group II, the first floor (Lift-up1), or second floor (Lift-up2), or third floor (Lift-up3) of all buildings is elevated respectively to create wind pathways through buildings. Compared to the initial case, urban open space can slightly or significantly reduce Pollutant Exposure for urban residents. As θ = 30° and 45°, open space settings are more effective to reduce Pollutant Exposure than θ = 0° and 15°.The Pollutant dilution near or surrounding open space and in its adjacent downstream regions is usually enhanced. Lift-up1 and Lift-up2 experience much greater Pollutant Exposure reduction in all wind directions than Lift-up3 and open space. Although further investigations are still required to provide practical guidelines, this study is one of the first attempts for reducing urban Pollutant Exposure by improving urban design.
Guowei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Associations of ambient air Pollutant Exposure with seminal plasma MDA, sperm mtDNA copy number, and mtDNA integrity.
Environment international, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p
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associations of ambient air Pollutant Exposure with seminal plasma mda sperm mtdna copy number and mtdna integrity
Environment International, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p < 0.001) (medians with 5th and 95th percentiles). There were no significant differences in sperm mtDNA copy number and mtDNA integrity between the two campuses. Furthermore, daily average PM10 Exposure during 0-90 days before semen ejaculation was found to be significantly and positively associated with seminal plasma MDA level (10.4; 95% CI, 4.4, 16.4) (percentage change per 10-unit increase in air Pollutant concentration; same meanings for the results below); daily average SO2 Exposure for 70-90 days and NO2 Exposure for 0-9 days prior to sampling were also positively associated with MDA level (74.7; 95% CI, 32.1, 119 and 11.9; 95% CI, 4.8, 19.0, respectively). AQI for 0-90 days and 70-90 days prior to sampling positively correlated with seminal plasma MDA concentrations (11.4; 95% CI, 4.7, 18.1 and 12.2; 95% CI, 5.3, 19.1, respectively). Additionally, daily average SO2 Exposures for 10-14 and 0-9 days prior to sampling were negatively associated with sperm mtDNA copy number and mtDNA integrity, respectively (-9.0; 95% CI, -16.4, -1.6 and -38.3; 95% CI, -64.1, -11.8, respectively). However, only the correlations between SO2 Exposure and AQI value for 70-90 days prior to sampling and MDA levels remained significant after multiplicity adjustment. CONCLUSIONS The results indicate that bad air quality, especially SO2 Exposure during certain periods of sperm development, might be correlated with oxidative damage to sperm. These findings can deepen the understanding of the potential impacts of air pollution on sperm quality.
Xuemei Wang - One of the best experts on this subject based on the ideXlab platform.
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the influence of solar natural heating and nox o3 photochemistry on flow and reactive Pollutant Exposure in 2d street canyons
Science of The Total Environment, 2021Co-Authors: Jiarui Liu, Xuemei Wang, Guanwen Chen, Qun Wang, Shuhang Cui, Yong Zhang, Peng Gao, Jian HangAbstract:Abstract This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-e model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) Pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106–107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate Pollutant Exposure in near-road buildings. As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 Exposure is generally about 40%–380% larger than passive CO Exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2–3 K and influences chemical rate slightly, thus this impact on reactive Pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.
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The influence of solar natural heating and NO x -O 3 photochemistry on flow and reactive Pollutant Exposure in 2D street canyons.
The Science of the total environment, 2020Co-Authors: Jiarui Liu, Xuemei Wang, Guanwen Chen, Qun Wang, Shuhang Cui, Yong Zhang, Peng Gao, Jian HangAbstract:Abstract This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-e model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) Pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106–107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate Pollutant Exposure in near-road buildings. As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 Exposure is generally about 40%–380% larger than passive CO Exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2–3 K and influences chemical rate slightly, thus this impact on reactive Pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.
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Numerical studies of passive and reactive Pollutant dispersion in high-density urban models with various building densities and height variations
Building and Environment, 2020Co-Authors: Yong Zhang, Xuemei Wang, Jiarui Liu, Peng Gao, Lan Chen, Hualiang Lin, Jian HangAbstract:Abstract Vehicular Pollutant Exposure in the near-road buildings of high-density urban areas has been rarely studied. This paper investigates the impacts of high-density building morphology on passive (CO) and reactive (NOx-O3) Pollutant dispersion in three-dimensional (3D) urban-like models, e.g. medium (street width W = 30 m,λp = 0.25, λf = 0.6) and compact (W = 18 m,λp = 0.39,λf = 0.94) layouts with uniform (H = 72 m) or various heights (H1 = 48 m,H2 = 96 m). Personal intake fraction P_iF and its spatially-averaged value for the entire building wall ( W) are utilized for Exposure assessment. Some meaningful findings are proposed: 1) When wind blows through neighborhood-scale (~1 km) urban models, it decelerates rapidly and then reaches a flow balance where pedestrian-level velocity and Pollutant Exposure vary depending on building densities and height variations. 2) Uniform-height cases attain overall W of ~0.3–1.3 ppm in target streets. The compact layout (λf = 0.94) experiences weaker vertical exchange where downward helical flows transport more Pollutants to windward wall than medium-type (λf = 0.6), inducing two-order larger windward-side W (~1 ppm) than leeward-side (~0.01 ppm). 3) Building height variations obtain greater velocity and smaller W (~0.2–1.0 ppm) in front of taller buildings than those behind them ( W~2.6–4.2 ppm). 4) No matter with or without height variations, densifying building arrays (λf = 0.6 to 0.94) raises windward-side W and mitigates leeward-side W, but overall W for both sides of target streets only change slightly. 5) With present NOx-O3 photochemistry (source emissions NO:NO2 = 10:1, background [O3] = 20 ppbv), NO2 Exposure is 40%–230% larger than passive CO Exposure, but NO is near to CO. This study implies the near-road Pollutant Exposure in high-density urban models is sensitive to building morphology which should be carefully designed.
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the impact of urban open space and lift up building design on building intake fraction and daily Pollutant Exposure in idealized urban models
Science of The Total Environment, 2018Co-Authors: Chenyuan Sha, Xuemei Wang, Yuanyuan Lin, Yifan Fan, Xi Chen, Jian HangAbstract:Abstract Sustainable urban design is an effective way to improve urban ventilation and reduce vehicular Pollutant Exposure to urban residents. This paper investigated the impacts of urban open space and ‘lift-up’ building design on vehicular CO (carbon monoxide) Exposure in typical three-dimensional (3D) urban canopy layer (UCL) models under neutral atmospheric conditions. The building intake fraction (IF) represents the fraction of total vehicular Pollutant emissions inhaled by residents when they stay at home. The building daily CO Exposure (Et) means the extent of human beings' contact with CO within one day indoor at home. Computational fluid dynamics (CFD) simulations integrating with these two concepts were performed to solve turbulent flow and assess vehicular CO Exposure to urban residents. CFD technique with the standard k-e model was successfully validated by wind tunnel data. The initial numerical UCL model consists of 5-row and 5-column (5 × 5) cubic buildings (building height H = street width W = 30 m) with four approaching wind directions (θ = 0°, 15°, 30°, 45°). In Group I, one of the 25 building models is removed to attain urban open space settings. In Group II, the first floor (Lift-up1), or second floor (Lift-up2), or third floor (Lift-up3) of all buildings is elevated respectively to create wind pathways through buildings. Compared to the initial case, urban open space can slightly or significantly reduce Pollutant Exposure for urban residents. As θ = 30° and 45°, open space settings are more effective to reduce Pollutant Exposure than θ = 0° and 15°.The Pollutant dilution near or surrounding open space and in its adjacent downstream regions is usually enhanced. Lift-up1 and Lift-up2 experience much greater Pollutant Exposure reduction in all wind directions than Lift-up3 and open space. Although further investigations are still required to provide practical guidelines, this study is one of the first attempts for reducing urban Pollutant Exposure by improving urban design.
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numerical investigations of flow and passive Pollutant Exposure in high rise deep street canyons with various street aspect ratios and viaduct settings
Science of The Total Environment, 2017Co-Authors: Lejian He, Xuemei Wang, Jian Hang, Xiaohui LiAbstract:Abstract Vehicular Pollutant Exposure of residents and pedestrians in high-rise deep street canyons with viaducts and noise barriers requires special concerns because the ventilation capacity is weak and the literature reported inconsistent findings on flow patterns as aspect ratios (building height/street width, H/W) are larger than 2. By conducting computational fluid dynamics (CFD) simulations coupled with the intake fraction iF and the daily Pollutant Exposure Et, this paper investigates the impact of street aspect ratios, viaducts and noise barriers on the flow and vehicular passive Pollutant Exposure in full-scale street canyons (H/W = 1–6, W = 24 m). iF represents the fraction of total emissions inhaled by a population (1 ppm = 10− 6), while Et means the extent of human beings’ contact with Pollutants within one day. CFD methodologies of passive Pollutant dispersion modeling are successfully validated by wind tunnel data in Meroney et al. (1996). As a novelty, the two-main-vortex pattern start appearing in full-scale street canyons as H/W changes from 4 to 5, however previous studies using wind-tunnel-scale models (H = 6cm) reported two to five vortexes as H/W = 2–5. This finding is validated by both smoke visualization in scale-model outdoor field experiments (H = 1.2m, W = 0.6m) and CFD simulations of Reynolds number independence. Cases with two main vortexes (H/W = 5–6) experience much larger daily Pollutant Exposure (~ 103–104 mg/m3/day) than those with single main vortex as H/W = 1–4 (~ 101–102 mg/m3/day). Moreover leeward-side Pollutant Exposures are much larger than windward-side as H/W = 1–4 while oppositely as H/W = 5–6. Assuming a general population density, the total iF is 485–803 ppm as H/W = 1, 2020–12051 ppm as H/W = 2–4, and 51112–794026 ppm as H/W = 5–6. With a single elevated Pollutant source, cases with viaducts experience significantly smaller Pollutant Exposures than cases without viaducts. Road barriers slightly increase Pollutant Exposure in near-road buildings with H/W = 1 while reduce a little as H/W = 3 and 5. Two-source cases can experience 2.60–5.52 times Pollutant Exposure as great as single-source cases.
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Associations of ambient air Pollutant Exposure with seminal plasma MDA, sperm mtDNA copy number, and mtDNA integrity.
Environment international, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p
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associations of ambient air Pollutant Exposure with seminal plasma mda sperm mtdna copy number and mtdna integrity
Environment International, 2020Co-Authors: Guowei Zhang, Fan Jiang, Qing Chen, Huan Yang, Niya Zhou, Lei Sun, Peng Zou, Wang Yang, Jia Cao, Ziyuan ZhouAbstract:BACKGROUND Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air Pollutant Exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. OBJECTIVES We assessed the associations of major air Pollutant Exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. METHODS The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air Pollutant Exposure during 0-90, 0-9, 10-14 and 70-90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air Pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air Pollutant Exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. RESULTS During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p < 0.001) (medians with 5th and 95th percentiles). There were no significant differences in sperm mtDNA copy number and mtDNA integrity between the two campuses. Furthermore, daily average PM10 Exposure during 0-90 days before semen ejaculation was found to be significantly and positively associated with seminal plasma MDA level (10.4; 95% CI, 4.4, 16.4) (percentage change per 10-unit increase in air Pollutant concentration; same meanings for the results below); daily average SO2 Exposure for 70-90 days and NO2 Exposure for 0-9 days prior to sampling were also positively associated with MDA level (74.7; 95% CI, 32.1, 119 and 11.9; 95% CI, 4.8, 19.0, respectively). AQI for 0-90 days and 70-90 days prior to sampling positively correlated with seminal plasma MDA concentrations (11.4; 95% CI, 4.7, 18.1 and 12.2; 95% CI, 5.3, 19.1, respectively). Additionally, daily average SO2 Exposures for 10-14 and 0-9 days prior to sampling were negatively associated with sperm mtDNA copy number and mtDNA integrity, respectively (-9.0; 95% CI, -16.4, -1.6 and -38.3; 95% CI, -64.1, -11.8, respectively). However, only the correlations between SO2 Exposure and AQI value for 70-90 days prior to sampling and MDA levels remained significant after multiplicity adjustment. CONCLUSIONS The results indicate that bad air quality, especially SO2 Exposure during certain periods of sperm development, might be correlated with oxidative damage to sperm. These findings can deepen the understanding of the potential impacts of air pollution on sperm quality.