Chemical speciation and health risks of airborne heavy metals around an industrial community in Nigeria

Abstract

Quantification of PM_2.5 (particulate matter <2.5?µm) bound heavy metals and their potential health risks were carried out around a cement manufacturing company in Ewekoro, Nigeria. The PM_2.5 samples were collected using Environtech gravimetric sampler. A four-staged sequential extraction procedure was used to fractionate PM_2.5 bound chromium (Cr), lead (Pb), aluminum (Al), copper (Cu), and silver (Ag), and further analyzed using inductively coupled plasma mass spectrometry. Chemical speciation results reveal bioavailable levels of Pb (4.05?µg/m³), Cr (10.75?µg/m³), Al (16.47?µg/m³), Cu (4.38E-01?µg/m³), and Ag (1.22E-02?µg/m³) in the airborne particulates. Pb and Cr levels exceeded the World Health Organization allowable limit of 0.5 and 2.5E-05?µg/m³, respectively. The labile phases showed strong indication of the presence of Cr and Cu metal. Excess cancer risks exposure for adults, outdoor workers and children were higher than the acceptable risk target level of 1E-06. Non-carcinogenic health risk estimated using hazard quotients (HQs) and hazard indices (HIs) showed ingestion route within the safe level of HI <1 implying no adverse effect while inhalation route exceeded the safe level for all receptors. Enforcement of pollution control by authorized agencies, and screening of greenbelts as sinks for air pollutants is strongly recommended.     

Apparent resistance to fall in forced vital capacity in children with increasing mass level of fine particulate: A physiological phenomenon

Abstract

Forced vital capacity (FVC) of children in the age group 10–12 years are reported as a function of quantum increase in PM_2.5 level in ambient air. The data are reported for the children in the categories based on their respective body mass index (BMI). FVC (% predicted) values decreased with increasing level of PM_2.5. The subjects are found to respond in a selective manner as plateau was observed for FVC values against some selected ranges of PM_2.5 concentration levels (74 µgm^?3 to >117 µgm^?3). To explain this unusual behavior, sac theory is proposed which explains the observations of FVC for subjects of all categories with different BMI values.     

Air quality modeling for health risk assessment of ambient PM10, PM2.5 and SO2 in Iran

In this study, we have estimated the number of total mortality (T-mortality), cardiovascular morbidity (CV-mortality), respiratory mortality (R-mortality), hospital admissions due to cardiovascular diseases (HA-CVD), respiratory diseases (HA-RD), chronic obstructive pulmonary diseases (COPD) and acute myocardial infarction (AMI) due to exposure to particulate matter less than 10 µm (PM₁₀), 2.5 µm (PM_2.5) and sulfur dioxide (SO₂) in western Iran in 2016. The World Health Organization (WHO) method was used to assess the mortality and morbidity among the exposed people. The results showed that about 3.9% CM (95% CI: 2.9–7.8%), 3.9% HA-RD (95% CI: 2.4–7.8%) and 4.4% HA-CVD (95% CI: 3.0–6.8%) for ambient PM₁₀ and about 7.3% TM (95% CI: 4.2–9.7%), 12.1% CM (95% CI: 3.5–14.6%) and 3.0% RM (95% CI: 0–6.3%) for PM_2.5 are respectively attributed to concentrations exceeding 10 µg/m³. Furthermore, 3.2% HA-COPD (95% CI: 0–5.04%) and 4.2% AMI (95% CI: 1.6–4.3%) can be attributed to SO₂ concentrations greater than 10 µg/m³, respectively. To reduce the adverse health effect of PM, health advices provided by health authorities should be given to general population especially vulnerable people such as people with chronic lung and heart pathologies, elderly and children during the dusty days.     

Performance of AERMOD and CALPUFF models on SO2 and NO2 emissions for future health risk assessment in Tema Metropolis

AERMOD results were compared with the reported CALPUFF results to estimate the concentrations and temporal distributions of SO₂ and NO₂ from Tema Oil Refinery with particlar attention to heavy rainy season (HRS), minor rainy season (MRS), and dry season (DS). Statistical indices, including the fractional bias (FB), geometric mean variance (VG), normalized mean square error (NMSE), index of agreement (IOA), and geometric mean bias (MG), were used to assess the reliability of the models. Overall, AERMOD better predicted ambient SO₂ and NO₂ levels than the reported CALPUFF model. For SO₂, AERMOD showed a good agreement with FB, IOA, and MG while CALPUFF showed a good prediction in NMSE and VG. Also, AERMOD predicted NO₂ well with NMSE, IOA, MG, and VG compared with FB for CALPUFF. The MRS results showed higher hourly maximum concentrations (107.4 µg/m³ for SO₂ and 31.7 µg/m³ for NO₂). Maximum daily concentrations were slightly higher in HRS (37.7 µg/m³ for SO₂ and 9.6 µg/m³ for NO₂) compared to MRS and DS. The performace of the models may provide a better understanding for future epidemiological studies.     

Estimating PM2.5 concentrations with statistical distribution techniques for health risk assessment in Bangkok

Abstract

Ambient PM_2.5 data in the Central Business District (CBD) of Bangkok monitored by Pollution Control Department and Bangkok Metropolitan Administration were collected over three years in Bangkok from 2015 to 2017. The other air pollutions data were used as the dependent variables to develop mathematic models with statistical distribution technique. Multiple linear regression technique was selected as the main statistical distribution methodology for estimating PM_2.5 concentrations in non-monitored areas. The predicted PM_2.5 concentrations were validated against the measured PM_2.5 concentrations by various statistical techniques. The validation found that the model had strong significant correlations for ambient and roadside area with R ²?=?0.88 and 0.96, respectively. The non-carcinogenic health risk assessment of PM_2.5 was quantified as the hazard quotient (HQ) from both the measured and predicted data. The risk areas and HQ were compared using the inverse distance weighting interpolation technique and illustrated as GIS-based maps. During December to February, the HQ values of PM_2.5 were exceed 1 (HQs?>?1) at all area of CBD; however, the highest HQ was found in the southern part of CBD. The finding could be used for residential health awareness in that area.     

Characterization of metal(loid)s in indoor and outdoor PM2.5 of an office in winter period

The characterization of indoor (a naturally ventilated office) and outdoor (adjacent courtyard) metals in PM_2.5 during a winter period in Xi'an, China were carried out. The results indicated that the average mass concentrations of PM_2.5 in indoor and outdoor environments all exceeded the daily average limit of 75 µg m^–3 set by the Chinese government. The dominant metals in PM_2.5 were Ca, Al, Zn, Mg, Fe, and Pb in both indoor and outdoor air. Concentration of As was much higher than the standard of 6 ng m^–3 issued by the government. Enrichment factor analysis showed that anthropogenic emissions might be the primary sources of As, Cd, Pb, and Zn, while crust was the main origin of Co. A majority of indoor-to-outdoor concentration ratios of metal were lower than 1 indicating mostly the contribution of outdoor sources rather than indoor ones. As and Cr in both indoor and outdoor air posed the highest noncarcinogenic and carcinogenic risks, respectively. The noncarcinogenic and carcinogenic risks were 2.74 and 2.54 × 10^?4 indoor and 4.04 and 3.87 × 10^?4 outdoor, which suggested that possible adverse health effects should be of concern.     

Effects of air pollution and habitual exercise on the risk of death: a longitudinal cohort study

Background:Exercise may exacerbate the adverse health effects of air pollution by increasing the inhalation of air pollutants. We investigated the combined effects of long-term exposure to fine particle matter (PM_2.5) and habitual exercise on deaths from natural causes in Taiwan.Methods:We recruited 384 130 adults (aged ≥ 18 yr) with 842 394 medical examination records between 2001 and 2016, and followed all participants until May 31, 2019. We obtained vital data from the National Death Registry of Taiwan. We estimated PM_2.5 exposure using a satellite-based spatiotemporal model, and collected information on exercise habits using a standard self-administered questionnaire. We analyzed the data using a Cox regression model with time-dependent covariates.Results:A higher level of habitual exercise was associated with a lower risk of death from natural causes, compared with inactivity (hazard ratio [HR] 0.84, 95% confidence interval [CI] 0.80–0.88 for the moderate exercise group; HR 0.65, 95% CI 0.62–0.68 for the high exercise groups), whereas a higher PM_2.5 exposure was associated with a higher risk of death from natural causes compared with lower exposure (HR 1.02, 95% CI 0.98–1.07, and HR 1.15, 95% CI 1.10–1.20, for the moderate and high PM_2.5 exposure groups, respectively). Compared with inactive adults with high PM_2.5 exposure, adults with high levels of habitual exercise and low PM_2.5 exposure had a substantially lower risk of death from natural causes. We found a minor, but statistically significant, interaction effect between exercise and PM_2.5 exposure on risk of death (HR 1.03 95% CI 1.01–1.06). Subgroup analyses, stratified by PM_2.5 categories, suggested that moderate and high levels of exercise were associated with a lower risk of death in each PM_2.5 stratum, compared with inactivity.Interpretation:Increased levels of exercise and reduced PM_2.5 exposure are associated with a lower risk of death from natural causes. Habitual exercise can reduce risk regardless of the levels of PM_2.5 exposure. Our results suggest that exercise is a safe health improvement strategy, even for people residing in relatively polluted regions.

Air pollution and physical inactivity are both major public health challenges worldwide.¹ Air pollution was the fifth leading cause of disability related to health and accounted for 4.9 million deaths worldwide in 2017.² More than 91% of the global population lives in areas where air quality does not meet the World Health Organization (WHO) guidelines.³ In addition, physical inactivity was the fourth leading risk factor for death globally, accounting for 5.3 million deaths worldwide in 2012.⁴ The WHO has challenged its member states to reduce physical inactivity by 15% by 2030.⁵As people exercise, their ventilation rate increases, which increases the volume of air pollutants they inhale. This may exacerbate the adverse health effects of air pollutants. Thus, the risk–benefit relation between air pollution and exercise needs to be assessed to understand whether it is safe to exercise regularly in polluted regions. Indeed, some studies have shown that acute exposure to air pollution when exercising may override the benefits of exercise.^6,7 It is possible that the effects of long-term exposure to air pollution may be irreversible and cause a much larger disease burden than short-term exposure. Limited information exists on the combined effects of long-term exposure to air pollution and habitual exercise on human health, and findings have been inconsistent depending on health outcome. Three cohort studies have explored the relation between air pollution, physical activity and risk of death in Hong Kong,⁸ Denmark and the United States,⁹ with relatively small sample sizes.¹⁰ Therefore, we sought to investigate the combined effects of habitual exercise and long-term exposure to fine particle matter (PM_2.5) on the risk of death from natural causes (i.e., deaths not attributable to accident, suicide or homicide) using a longitudinal cohort of adults in Taiwan, where the annual PM_2.5 concentrations are 1.6 times higher than the WHO-recommended limit. We hypothesized that the beneficial effects of habitual exercise on risk of death may outweigh the risk of high levels of air pollutants inhaled during exercise.     

Characterizing of fine particulate matter (PM1) on the platforms and outdoor areas of underground and surface subway stations

A campaign was conducted to assess the PM₁ concentration and elemental composition on the platforms and adjacent outdoor areas of an underground subway station (Imam Khomeini) and a surface subway station (Sadeghiye) in Tehran from June 2014 to November 2014. The respective mean concentrations of PM₁ on the platforms and in the outdoor areas of Imam Khomeini station were 42.04 and 30.92 µg/m³ and for Sadeghiye station 31.42 and 26.02 µg/m³. Statistical analyses demonstrated that the platforms of the Imam Khomeini and Sadeghiye stations were influenced by the adjacent ambient air of these stations (p < 0.05). PM₁ was found to be highly enriched with Fe on the platforms of metro systems, which were more frequently encountered in the Imam Khomeini station than the Sadeghiye station as 41.06% and 37.73% of the total PM₁ mass respectively. Minor elements, particularly Ba, Pb, Cr, Cu, Ni, Mn, Ti, V, and Zn, were elevated for the platform of Imam Khomeini and, to a lesser degree, the platform of Sadeghiye stations, which may be due to abrasion processes between rail tracks, wheels, and brake pads.     

Seasonal Variation in Schools’ Indoor Air Environments and Health Symptoms among Students in an Eastern Mediterranean Climate

The indoor air quality (IAQ) in classrooms highly affects the health and productivity of students. This article aims to clarify seasonal variation in indoor environment and sick building syndromes (SBS) symptoms in an Eastern Mediterranean climate. A series of field measurements were conducted during the fall and winter seasons from October 2011 to March 2012 in 12 naturally ventilated schools located in the Gaza Strip. Data on environmental perception and health symptoms were obtained from 724 students by using a validated questionnaire. The results showed that indoor PM₁₀ and PM_2.5 concentrations were 426.3 ± 187.6 μg/m³ and 126.6 ± 94.8 μg/m³, respectively. The CO₂ concentrations and ventilation rate widely exceeded their reference values during the winter season. The prevalence rates of general symptoms were relatively high at baseline assessment in the fall season and increased significantly during follow-up in the winter season. Significant increases in disease symptoms such as mucosal irritation and pre-existing asthma symptoms among students could be related to poor indoor air quality. Five distinct groups of SBS symptoms from factor analysis of students’ related symptoms were significantly correlated with PM₁₀ and PM_2.5, CO₂, ventilation rate, and indoor temperature. As vulnerable children, this situation negatively affects their school performance and health.     

Elevated levels of urinary 17-ketosteroids in central Indian children residing near sewage treatment plant and solid waste disposal plant: A preliminary study

Urinary excretion of 17-ketosteroid (17-KS) was assessed in male pre-pubertal subjects aged (8–11 years; n = 90). Children living near sewage treatment plant and solid waste disposal plant (Group P) showed significantly higher levels of urinary 17-KS (Group P: 3.27 ± 1.63 µg/mL/CRE; p < 0.01) than children living in cleaner area (0.50 ± 0.53 µg/mL/CRE; Group C). Occurrence of urinary dibutyl phthalate in representative subjects of Group P (odds ratio: 9; p < 0.05; 95% of Confidence interval (CI) 1.93–72.99) was higher compared to Group C. Urinary concentrations of Cd (0.85 µg/g CRE ± 0.11), Mn (24.25 µg/g CRE ± 6.11) and Pb (12.39 µg/g CRE ± 2.86) in Group P were significantly (p < 0.01) higher than those found in Group C (Cd (0.28 µg/g CRE ± 0.03), Mn (13.33 µg/g CRE ± 3.20) and Pb (5.67 µg/g CRE ± 0.53)). Analyses of ambient air samples (PM₁₀) in polluted area revealed major occurrence of phthalates, whereas derivatives of trifluoromethyl, dione, etc. were identified in PM_2.5 fraction. Metal (Cd, Co, Mn and Pb) concentrations in ambient air (24 h, PM₁₀) were higher in polluted area compared to cleaner area. We conclude that elevated levels of urinary 17-KS in Group P could be attributed to higher exposure of these subjects to Endocrine disrupting chemicals (EDCs) compared to Group C.     

In vivo and in vitro evidence for the involvement of Nrf2-antioxidant response element signaling pathway in the inflammation and oxidative stress induced by particulate matter (PM10): the effective role of gallic acid

Environmental pollution is one of the risk factors for respiratory diseases. The nuclear factor erythroid 2-related factor 2 (Nrf2) is the major mechanisms contributing to cellular defense against oxidative damage. Gallic acid (GA) is regarded as potent anti-inflammatory and antioxidant agents. The aim was to evaluate the role of Nrf2 pathway in particulate matter (PM₁₀) exposure on lung and epithelial cells with an emphasis on the role of GA. In in vivo part, the rats were divided as control, GA (30?mg/kg), particulate matter (PM) (0.5, 2.5, and 5?mg/kg), and PM?+?GA. In in vitro study, the cells were divided as control, PM₁₀ (100, 250, and 500?µg/ml), GA (50 µmol/L) and PM₁₀+GA. Inflammation, oxidative stress and Nrf2-pathway factors were assessed. PM₁₀ groups showed a considerable increase in the epithelial permeability and inflammatory parameters. We also found a significant decrease in the expression of Nrf2 and its up-stream regulators genes. Accordingly, the biosynthesis of glutathione (GSH) and other antioxidant activities significantly decreased. Gallic acid was identified to restore the antioxidant status to the normal levels. Our findings approved that Nrf2 is involved in PM₁₀-induced oxidative damages and showed that Nrf2 activation by natural agents could ameliorate respiratory injuries induced by PM₁₀.     

Acute Effects of Particulate Air Pollution on the Incidence of Coronary Heart Disease in Shanghai,China

Introduction

Evidence based on ecological studies in China suggests that short-term exposure to particulate matter (PM) is associated with cardiovascular mortality. However, there is less evidence of PM-related morbidity for coronary heart disease (CHD) in China. This study aims to investigate the relationship between acute PM exposure and CHD incidence in people aged above 40 in Shanghai.

Methods

Daily CHD events during 2005–2012 were identified from outpatient and emergency department visits. Daily average concentrations for particulate matter with aerodynamic diameter less than 10 microns (PM₁₀) were collected over the 8-year period. Particulate matter with aerodynamic diameter less than 2.5 microns (PM_2.5) were measured from 2009 to 2012. Analyses were performed using quasi-poisson regression models adjusting for confounders, including long-term trend, seasonality, day of the week, public holiday and meteorological factors. The effects were also examined by gender and age group (41–65 years, and >65 years).

Results

There were 619928 CHD outpatient and emergency department visits. The average concentrations of PM₁₀ and PM_2.5 were 81.7μg/m³ and 38.6μg/m³, respectively. Elevated exposure to PM₁₀ and PM_2.5 was related with increased risk of CHD outpatients and emergency department visits in a short time course. A 10 μg/m³ increase in the 2-day PM₁₀ and PM_2.5 was associated with increase of 0.23% (95% CI: 0.12%, 0.34%) and 0.74% (95% CI: 0.44%, 1.04%) in CHD morbidity, respectively. The associations appeared to be more evident in the male and the elderly.

Conclusion

Short-term exposure to high levels of PM₁₀ and PM_2.5 was associated with increased risk of CHD outpatient and emergency department visits. Season, gender and age were effect modifiers of their association.     

Study of PM10, PM2.5, and PM1 levels in during dust storms and local air pollution events in urban and rural sites in Tehran

The aim of this study is to survey the PM₁₀, PM_2.5, and PM₁ concentrations in rural and urban areas in Tehran province during cold, warm and dust storm days from December 22, 2016 to June 5, 2017 using Grimm Model aerosol spectrometer. During the study period, daily PM₁₀, PM_2.5, and PM₁ concentrations ranged from 27.2 to 244.96, 8.4 to 77.9, and 6.5 to 56.8 μg/m³ in urban sites, and 22.8 to 286.4, 6 to 41.1, and 2.1 to 20.2 μg/m³ in rural parts, respectively. Particularly, both daily WHO limits for outdoor PM₁₀ (50.0 μg/m³) and PM_2.5 (25.0 μg/m³) exceeded in 95% and 83% of the outdoor measurements in winter and 82% and 58% in total sampled days in urban site, respectively. The 24-h average PM₁₀ and PM_2.5 concentrations also exceeded by 59% and 18% in winter and by 36% and 14% of all sampling days in rural site, respectively. During the dust storm, the 24-h average PM₁₀, PM_2.5, and PM₁ concentrations were, respectively 4.7, 2, and 1.96 times higher than those in urban site and 2, 1.7, and 1.3 times more than those in rural site in all sampled days.     

An Assessment of Risk from Particulate Released from Outdoor Wood Boilers

Use of outdoor wood boilers (OWB) has increased due to cost of fossil fuels. OWB short stacks release particles close to the breathing level, producing high levels of particulate matter ≤2.5 μm in diameter (PM_2.5). This assessment determines OWB contribution to local cancer risk and estimates thresholds for acute non-cancer risks. Carcinogenic PAHs in wood smoke (PM_2.5) cancer risks range from 2.7 × 10^–3 for the upper bound scenario (95% UCL value of PM_2.5 (665 μg/m³)) to 7.6 × 10^–5 for the lower bound (mean (186 μg/m³)). These risks represent a 7-fold increase of acceptable cancer risk for the lower bound value and 2 orders of magnitude above acceptable levels for the upper bound values. Non-cancer effects such as asthma and cardiopathies include respiratory attacks, hospital emergency room visits, and hospitalizations. Inhaled dose acute risk thresholds of 96, 120, and 250 μg PM 2.5/6 hours are proposed. Operation of an OWB that emits 100 grams PM_2.5/h was modeled and found to increase the exposures that exceed the 120-μg-risk level at and in residences within 500 to 1000 feet. The increases are projected to occur during periods of poor air mixing due to decreased wind speeds or inversions. Our analysis proposes a 6-h PM_2.5 inhaled dose threshold to predict peak periods of unhealthy air quality instead of 24-h and annual averages standards, which mask peak emissions.     

Heavy Metal Content in PM2.5 Air Samples Collected in the Metropolitan Area of Monterrey,México

The air PM_2.5 concentration and its heavy metal content (Fe, Pb, Mn, Ni, As) were measured in the Metropolitan Area of Monterrey, Méxicoin Mexico, an area that is characterized by both very active and diverse industrial activity and intense highway traffic and industrial activity. The 24-h PM_2.5 samples were collected in two different zones during a 1-year-long measurement program (February 2008–February 2009). The year PM_2.5 average was above 15 μg/m³ exceeding Mexican and international standards. The difference of PM_2.5 in each zone was not statistically significant. The greatest metal content was for iron, followed by lead, manganese, nickel and arsenic. The difference in metal content for Pb, Mn, and As was statistically significant.     

Distribution,sources, and health risk assessment of polycyclic aromatic hydrocarbons in dust from urban environment in the Niger Delta,Nigeria

The concentrations of the 16 U.S. Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) were measured in urban street dust with a view to understanding the potential risk to urban residents exposed to street dust, sources, and distribution of the PAHs. Gas chromatography–mass spectrometry was used to measure the concentrations of the PAHs after ultra-sonication with hexane/dichloromethane and clean up. The total concentrations of the ?16 PAHs in the urban street dust from Warri and its environs ranged from 165.1 to 1012 µg kg^?1. The isomeric ratios and the PCA indicated that combustion of petroleum and biomass are the major sources of PAHs in Warri and its environs. The total BaP carcinogenic and mutagenic potency concentrations (?BaP_TEQ and ?BaP_MEQ) were in the range of 0.03 to 219 µg kg^?1 and 0.52 to 182 µg kg^?1, respectively. The incremental life cancer risk from exposure of the residents of Warri and its environs ranged from 4.07 × 10^?7 to 3.11 × 10^?3 and 2.13 × 10^?7 to 1.49 × 10^?3 for the children and adults, respectively, which were higher than the baseline value of acceptable risk of 10^?6 (i.e., one case per million people).     

Dynamic changes of canopy-scale mesophyll conductance to CO₂ diffusion of sunflower as affected by CO₂ concentration and abscisic acid

Leaf‐level measurements have shown that mesophyll conductance (g_m) can vary rapidly in response to CO₂ and other environmental factors, but similar studies at the canopy‐scale are missing. Here, we report the effect of short‐term variation of CO₂ concentration on canopy‐scale g_m and other CO₂ exchange parameters of sunflower (Helianthus annuus L.) stands in the presence and absence of abscisic acid (ABA) in their nutrient solution. g_m was estimated from gas exchange and on‐line carbon isotope discrimination (Δ_obs) in a ¹³CO₂/¹²CO₂ gas exchange mesocosm. The isotopic contribution of (photo)respiration to stand‐scale Δ_obs was determined with the experimental approach of Tcherkez et al. Without ABA, short‐term exposures to different CO₂ concentrations (C_a 100 to 900 µmol mol^?1) had little effect on canopy‐scale g_m. But, addition of ABA strongly altered the CO₂‐response: g_m was high (approx. 0.5 mol CO₂ m^?2 s^?1) at C_a < 200 µmol mol^?1 and decreased to <0.1 mol CO₂ m^?2 s^?1 at C_a >400 µmol mol^?1. In the absence of ABA, the contribution of (photo)respiration to stand‐scale Δ_obs was high at low C_a (7.2‰) and decreased to <2‰ at C_a > 400 µmol mol^?1. Treatment with ABA halved this effect at all C_a.     

广州大夫山雨季林内外空气TSP和PM2.5浓度及水溶性离子特征

采用平行同步采样法,于2012年雨季,对广州市大夫山森林公园林内外空气的总悬浮颗粒物(TSP)和细颗粒物(PM_2.5)样品进行了24 h收集,测定了TSP和PM_2.5的质量浓度并分析了样品中水溶性无机离子成分。结果表明:林内外PM_2.5的质量浓度平均值分别为(40.18±10.47)和(55.79±13.01) g/cm³;林内外TSP的质量浓度分别为(101.32 ± 33.19)和(116.61±35.36) g/cm³。林内与林外比,PM_2.5和TSP平均质量浓度都显著减少(P < 0.05),表明森林能显著改善空气环境质量。TSP和PM_2.5中SO₄^2-、Na⁺、NH₄⁺和NO₃^-为水溶性无机离子主要成分,占总离子质量的80%以上,林外这些离子的浓度高于林内(NH₄⁺除外)。这4种离子雨季在空气中的主要存在方式为NaCl、Na₂SO₄、NH₄HSO₄和NH₄NO₃。计算表明,采样期间海盐对大夫山空气TSP和PM_2.5的水溶性组分中Na⁺和Cl^-贡献最大,其它元素主要源自陆地源。林内外TSP和PM_2.5的c(NO₃^-)/c(SO₄^2-)比值在0.3以下,表明固定源是大夫山森林公园空气主要污染贡献者,TSP中c(NO₃^-)/c(SO₄^2-)的比值大于PM_2.5的比值,说明移动源对TSP的贡献大于PM_2.5。     

Assessing the Impact of Advected African Dust on Air Quality and Health in the Eastern United States

Large quantities of African dust are carried into the southeastern United States each summer with concentrations typically in the range of 10 to 100?µg m^?3. Because approximately one-third to one-half of the dust mass is in the size range under 2.5?µm diameter, the advection of African dust has implications for the EPA's newly implemented standard for PM_2.5 particulate matter and for the assessment of human health effects. It will be difficult to assess the impact of African dust events on air quality because they occur during the summer (maximum in July) when photochemical pollution events are frequent and intense in the eastern United States. Indeed, the presence of dust could affect the evolution of photochemical dust events. In order to assess the role of African dust in air quality in the United States, it will be necessary to develop a set of diagnostic indicators; it appears that dust mineralogy and elemental composition might be useful for this purpose. Various satellite products can be used to characterize the spatial coverage of dust events and, when coupled with meteorological tools, to predict impact regions.     

Metabolic rates in harvestmen (Arachnida, Opiliones): the influence of running activity

Abstract. Metabolic rates of adult Lophopilio palpinalis (Herbst, 1799) (Arachnida, Opiliones, Phalangioidea) and Paranemastoma quadripunctatum (Perty, 1833) (Arachnida, Opiliones, Troguloidea) are measured during rest and activity. Carbon dioxide release during rest is continuous in both species. Mean values at 20 °C are 4.2 µL min⁻¹ g⁻¹ for the males of P. quadripunctatum, 4.1 µL min⁻¹ g⁻¹ for the males of L. palpinalis and 4.7 µL min⁻¹ g⁻¹ for the females of L. palpinalis, thus being significantly higher in the egg-producing females. In L. palpinalis, respiratory quotient at rest is 0.84. Spontaneous walking activity with speeds of 15–30 cm min⁻¹ raises the metabolic rate by up to three-fold in both species. Lophopilio palpinalis is made to undertake constant running on a treadmill with speeds of 60, 72 and 96 cm min⁻¹. Enforced activity causes the animals to raise their metabolic rates by up to five-fold above resting rates. Animals reach a steady state of CO₂ release on the treadmill and show a fast t_1/2 on-response, indicating aerobic exercise. The minimum cost of locomotion is determined to be 2.5 × 10⁻³ J cm⁻¹ g⁻¹, thus fitting the predicted values for terrestrial locomotion.