Radioactive isotopes in atmospheric aerosols over Russia and the Sea of Japan following nuclear accident at Fukushima Nr. 1 Daiichi Nuclear Power Station in March 2011

Artificial radionuclides, such as iodine-131 (¹³¹I), cesium-134 (¹³⁴Cs), and cesium-137 (¹³⁷Cs), as well as natural isotopes of beryllium-7 (⁷Be) and potassium-40 (⁴⁰K) have been registered in atmospheric aerosols over Vladivostok selected from 11 March to 17 June 2011. Additionally, ¹³⁴Cs and ¹³⁷Cs were detected in atmospheric aerosols over Tomsk selected from 16 March to 17 June 2011. Artificial radionuclides were also discovered in atmospheric wet depositions sampled in Vladivostok from 3 to 17 May 2011. Moreover, these radionuclides have been registered in atmospheric aerosols over the sea surface of the Sea of Japan selected from 3 to 31 May 2011 during an expedition of the “Nadezhda” sailing ship. From 18 March to 15 April, an increase in concentrations of atmospheric aerosols over Vladivostok from 108.8 to 321.5 μg/m³ has been registered. It was accompanied by increased activity concentrations of ¹³⁴Cs, ¹³⁷Cs, and the ¹³¹I. During the period from 18 March to 15 April, activity concentrations of ¹³⁷Cs and ¹³⁴Cs in atmospheric aerosols increased 100 times compared with the minimum detectable concentration (MDC) level and peaked in the weekly sample gathered from 8 to 15 April (145.0 and 105.3 μBq/m³, respectively). Variability of concentrations of natural isotopes of ⁷Be and ⁴⁰K was not greater than 1 order of magnitude throughout the sampling period. Maximal values of ¹³⁷Cs and ¹³⁴Cs concentrations (1,281.5?±?141 and 384.4?±?42.3 μBq/m³, respectively) in Tomsk were reached in samples taken from 1 to 2 April. For the atmospheric aerosol samples from the Sea of Japan, the largest concentration of ¹³¹I (392.3?±?215.7 μBq/m³) was detected from 13 to 19 May, while all other samples had much lower concentration values. Synoptic analysis of back trajectories movement of air masses showed that the radioactive cloud came to Vladivostok from the regions of Siberia and northeastern part of China. Synoptic analysis for Tomsk showed that during the period of maximal activity concentrations (1–9 April), air masses were arriving from the European part of Russia and north of Kazakhstan.     

Characteristics of colloids and their affinity for heavy metals in road runoff with different traffic in Beijing,China

The characteristics of colloids in urban road runoff with different traffic in Beijing, China, such as concentration, particle size, chemical property, and affinity for heavy metals were determined. The concentration of colloids was high, and an evident first flush effect was found in the runoff of road with heavy traffic. A large portion of colloids were distributed in the range of 1–10 μm. Traffic activity, rainfall intensity, and time of sample collection would not change the size distribution of colloids in the road runoff. The chemical property of colloids in the road runoff would be influenced by the soil erosion nearby green space, causing the content of organic colloids was high. The correlation coefficient between the concentration of colloids in colloidal fractions and the concentration of heavy metals (Cu, Zn, Cd, Pb, Fe, and Mn) in the road runoff with different traffic decreased with the same sequence from 0.02–0.2 μm, 0.2–0.45 μm, 0.45–1 μm, to 1–10 μm, suggesting that the heavy metals had stronger affinity for the colloids with small size. The concentration of Cu, Pb, and Zn exhibited significant correlations with the concentration of organic colloids in the road runoff. More aggregated spherical particles were found in the TEM image of the road runoff with heavy traffic. Zeta potentials and RMV data showed that the colloids with smaller size and the colloids in the road runoff with lighter traffic were much more stable.

     

Fate of radiocesium in sewage treatment process released by the nuclear accident at Fukushima

The nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) which occurred after the Great East Japan Earthquake on March 11, 2011 resulted in releases of radionuclides such as ¹³⁴Cs (half-life:T_1/2 = 2.06 yr), ¹³⁷Cs (T_1/2 = 30.04 yr) and ¹³¹I (T_1/2 = 8.05 d) to the environment. For this paper, we observed the monthly variations of radiocesium (¹³⁴Cs and ¹³⁷Cs) and stable Cs concentrations in influent, effluent, sewage sludge, and sludge ash collected from a sewage treatment plant 280 km north of the FDNPP from July to December, 2011. Using the stable Cs results, we concluded the mass balance of Cs in the sewage treatment plant showed that about 10% of the Cs entering the sewage treatment plant would be transferred to the sewage sludge, and then Cs in the sewage sludge was totally recovered in the sludge ash. The behavior of Cs was similar to that of Rb, but it was not similar to that of K in the sewage treatment process.     

Accumulation history of radionuclides in the lichen Stereocaulon vesuvianum from Mt. Vesuvius (south Italy)

The fruticose lichen Stereocaulon vesuvianum, growing on the slopes of Mt. Vesuvius (south Italy), was used as a biomonitor of 134Cs, 137Cs, 103Ru and 106Ru derived from the April 26 1986 Chernobyl nuclear reactor accident. Samples were taken at five different quotes (370, 490, 580, 780 and 960 m a.s.l.) and four successive dates (October 1986, December 1986, October 1987 and May 1999). At the first sampling, the concentrations (as Bq kg(-1) dry weight) ranged between 460 and 1020 for 134Cs, 1330 and 2500 for 137Cs, 90 and 200 for 103Ru and 360 and 710 for 106Ru, values generally lower in respect to those measured in soil and higher plants. Of the total 137Cs measured only 14% was due to 1950s and 1960s nuclear weapons tests fallout. Highest average activities of all nuclides were observed at the quote of 960 m and significant correlation (0.7相似文献   

Artificial radioactivity in environmental media (air, rainwater, soil, vegetation) in Austria after the Fukushima nuclear accident

Several environmental media in Austria were monitored for artificial radionuclides released during the Fukushima nuclear accident. Air (up to 1.2 mBq/m³ particulate ¹³¹I) and rainwater (up to 5.2 Bq/L ¹³¹I) proved to be the media best suited for the environmental monitoring, allowing also a temporal resolution of the activity levels. Significant regional differences in the wet deposition of ¹³¹I with rain could be observed within the city of Vienna during the arrival of the contaminated air masses. Forward-trajectory analysis supported the hypothesis that the contaminated air masses coming from the northwest changed direction to northeast over Northern Austria, leading to a strong activity concentration gradient over Vienna. In the course of the environmental monitoring of the Fukushima releases, this phenomenon—significant differences of ¹³¹I activity concentrations in rainwater on a narrow local scale (8.1 km)—appears to be unique. Vegetation (grass) was contaminated with ¹³¹I and/or ¹³⁷Cs at a low level. Soil (up to 22 Bq/kg ¹³⁷Cs) was only affected by previous releases (nuclear weapon tests, Chernobyl). Here, also significant local differences can be observed due to different deposition rates during the Chernobyl accident. The effective ecological half-lives of ¹³⁷Cs in soil were calculated for four locations in Austria. They range from 7 to 30 years. No Austrian sample investigated herein exceeded the detection limit for ¹³⁴Cs; hence, the Fukushima nuclear accident did not contribute significantly to the total radiocesium inventory in Austrian environmental media. The levels of detected radioactivity were of no concern for public health.     

Colloid and suspended particle migration experiments in a granite fracture

To determine the mobility of colloids (0.001–0.45 μm) and suspended particles (> 0.45 μm) in granite fractures, laboratory particle-migration and conservative tracer studies have been carried out in a natural fracture within a large granite block, with overall dimensions of 83×90×60 cm. Flow fields within this horizontal fracture were controlled through a set of 9 boreholes drilled orthogonally to the fracture. Laboratory experiments were performed using a range of average water velocities which contained values low enough to closely approximate the natural flow velocities of < 2 m yr⁻¹ in plutonic rocks of the Canadian Shield. The particles used had diameters between 0.02 and 22 μm, and included latex spheres, glass spheres and colloidal silica. Migration experiments were carried out with a filtered groundwater, ionic strength of 0.01 mol kg⁻¹, obtained from a granite fracture within the Whiteshell Research Area of Manitoba. Flushing experiments showed that suspended particles as large as 40 μm could be mobilized from the fracture surface. The mobility of suspended particles was significantly less than that of colloids. However, within the size range of colloids used in these studies (0.022–0.090 μm), colloid size did not affect colloid migration. Although, in general, colloids eluted ahead of the conservative tracer, colloid mobility was significantly reduced when the average groundwater velocity dropped below between 32 and 240 m yr⁻¹. Colloid transport was found to be very sensitive to flow path and flow direction.     

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process was investigated, using supernatant samples obtained from shaking experiments of sediment-water pairs simulating natural disturbances. The concentrations (dry-matter mass basis) of individual compounds (Cfraction) in two particle size fractions (0.1-1 and 1-10 μm) in the supernatants were generally slightly higher than those in the original sediment (Csed). Cfraction/Csed ratios ranged from 0.45 to 5.9 (median 1.5) without consistent differences among congener groups or consistent correlations against the number of chlorine atoms. The dioxin concentrations in the water column associated with the remaining sediment particles can therefore be estimated by those in the original sediment and by the concentration of suspended sediment particles in the water. The concentration of each compound in the remaining sediment particles (mostly 0.1-10 μm in size) can be roughly estimated by multiplying the concentration in the original sediment by 1.5.     

Resuspension of coarse particles in the region of Chernobyl

Measurements of resuspension into air in the coarse particle range (>10 μm in aerodynamic diameter) were performed as part of a field measurement experiment at four sites around Chernobyl during wind-driven and anthropogenic enhanced resuspension (agricultural activities). Caesium-137 was used to quantify the magnitude of resuspension. The mean resuspension factor of coarse particles was between 1×10^-10 and 6×10^-10 m^-1 for wind-driven resuspension. During agricultural activities, the resuspension increased by up to three orders of magnitude. Coarse particles comprised about one-third of the total amount of resuspended Caesium-137. The activity size distribution of Caesium-137 was not uniform in the coarse particle range: approximately 44% of the activity was found in the range 10–20 μm aerodynamic diameter. The determination of the number concentration of particles >20 μm aerodynamic diameter showed a linear relation between particle number and activity: the mean activity per particle was 0.75±0.15 μBq at the site Novozybkov, Russia. The resuspension factor was found to decrease exponentially with increasing relative soil moisture content. At higher soil humidity, the portion of coarse particles of the total resuspended activity was larger.     

Growth of ultrafine particles by brownian coagulation

Current atmospheric observations tend to support the view that continental tropospheric aerosols (particularly urban aerosols) show multimodal mass distributions in the size range of 0.01–100 μm. The origin of these aerosols is both natural and anthropogenic. Recently, trimodal sub-μm size distributions from combustion measurements at 0.008, 0.035 and 0.15 μm were also observed. Our interest in the present study is the secondary process of growth of sub-μm size aerosols by the coagulation process alone. Using the ‘J-space’ (integer-space) distribution method of Salk (Suck) and Brock (1979, J. Aerosol Sci.10, 58–590), we report an accurate numerical simulation study of the evolution of ultrafine to fine particle size distributions. Comparision with the analytic solution of Scott (1968, J. atmos. Sci.25, 54–64) was made to test the accuracy of our J-space or integer-space distribution method. Our multimodal sub-μ particle size distribution study encompassed the particle size range of 0.001–0.20 μm. Details of particle growth in each mode and interaction between different modes in the multimodal distribution were qualitatively analyzed.     

Estimation of thyroid doses and health risks resulting from the intake of radioactive iodine in foods and drinking water by the citizens of Tokyo after the Fukushima nuclear accident

The release of radioactive materials from the Fukushima nuclear power plant after the Great East Japan Earthquake on 11 March 2011 poses health risks. In this study, the intake of iodine 131 (I-131) in drinking water and foods (milk, dairy products, and vegetables) by citizens of Tokyo was estimated. The effects of countermeasures (restrictions on the distribution of foods and the distribution of bottled water for infants) on reducing intake were also evaluated. The average thyroid equivalent doses without countermeasures from 21 March 2011 were 0.42 mSv in adults, 1.49 mSv in children, and 2.08 mSv in infants. Those with countermeasures were 0.28, 0.97, and 1.14 mSv respectively, reductions of 33%, 35%, and 45%. Drinking water contributed more to intake by adults and children than foods. The intake of I-131 within the first 2 weeks was more than 80% of the estimated intake, owing to its short half-life, indicating that rapid countermeasures are important in reducing intake. The average risks of cancer incidence and mortality due to I-131 for infants were estimated to be 3 × 10⁻⁵ and 0.2 × 10⁻⁵, respectively, lower than the annual risks of traffic accidents, naturally occurring radioactive material (potassium 40), and environmental pollutants such as diesel exhaust particles.     

Mobilization of colloids in groundwater due to infiltration of water at a coal ash disposal site

We investigated groundwaters in the vicinity of a coal ash site near an electric generating station in the western U.S.A. The purpose of the study was to ascertain why fine particles or colloids appear in some subsurface water samples there. If such fine particles are merely introduced during bailing or pumping operations which suspend otherwise immobile soil colloids, we should exclude these particulate materials from the water samples before analysis intended to quantify what is moving through the aquifer. However, if the colloids were truly suspended and moving with the groundwater flow in situ, then we should includes their contribution to our assessment of the mobile loads.Application of very careful sampling techniques (slow pumping rates, no atmospheric exposure) did not cause the large quantities of colloids observed previously to disappear from well water in which they occured. Additionally, the same sampling procedures did not cause similar abundances of colloids to appear in waters collected from neighboring wells installed and developed in the same manner and in the same geologic strata. Thus we believe sampling artifacts do not explain the colloids' presence in the groundwater samples.On the other hand, the groundwater chemistry and the nature of the suspended colloids (size, composition) strongly suggest these fine particles were suspended and therefore moving with the groundwater flow. At wells exhibiting large amounts of suspended colloids (≈10–100 mg L⁻¹), the water was enriched in CO₂ and depleted in O₂ relative to nearby locations. The colloids were typically between 0.1 and 2 μm in size and were primarily silicates. These results suggest to us that, where infiltrating water is percolating through a site that has been mixed with coal ash, the secondary carbonate mineral in the soils are being dissolved; removal of this cementing carbonate phase may consequently release soil silicate colloids to be carried in the flowing water.Such processes may enhance contaminant transport in groundwater by augmenting the pollutant load moving in the groundwater, and increasing the permeability of the porous medium to pollutant infiltration with water water and/or rainwater.     

Distribution of polybrominated diphenyl ethers and dust particle size fractions adherent to skin in indoor dust,Pretoria, South Africa

In order to determine human exposure to the indoor toxicant, selection of dust fraction and understanding dust particle size distribution in settled indoor dust are very important. This study examined the influence of dust particle size on the concentration of polybrominated diphenyl ethers (PBDEs) congeners, assessed the distribution of dust particle size and characterized the main indoor emission sources of PBDEs. Accordingly, the concentrations of PBDE congeners determined in different indoor dust fractions were found to be relatively higher in the order of dust particle size: 45–106 μm?>?(<45 μm)?>?106–150 μm. The finding shows arbitrary selection of dust fractions for exposure determination may result in wrong conclusions. Statistically significant moderate correlation between the concentration of Σ₉PBDEs and organic matter content calculated with respect to the total dust mass was also observed (r?=?0.55, p?=?0.001). On average, of total dust particle size <250 μm, 93.4 % (m/m%) of dust fractions was associated with less than 150 μm. Furthermore, of skin adherent dust fractions considered (<150 μm), 86 % (v/v%) is in the range of particle size 9.25–104.7 μm. Electronic materials treated with PBDEs were found the main emission sources of PBDE congeners in indoor environment. Based on concentrations of PBDEs determined and mass of indoor dust observed, 150 μm metallic sieve is adequate for human exposure risk assessment. However, research in this area is very limited and more research is required to generalize the fact.     

Fungal fragments in moldy houses: A field study in homes in New Orleans and Southern Ohio

Smaller-sized fungal fragments (<1 μm) may contribute to mold-related health effects. Previous laboratory-based studies have shown that the number concentration of fungal fragments can be up to 500 times higher than that of fungal spores, but this has not yet been confirmed in a field study due to lack of suitable methodology. We have recently developed a field-compatible method for the sampling and analysis of airborne fungal fragments. The new methodology was utilized for characterizing fungal fragment exposures in mold-contaminated homes selected in New Orleans, Louisiana and Southern Ohio. Airborne fungal particles were separated into three distinct size fractions: (i) >2.25 μm (spores), (ii) 1.05–2.25 μm (mixture), and (iii) <1.0 μm (submicrometer-sized fragments). Samples were collected in five homes in summer and winter and analyzed for (1→3)-β-d-glucan.The total (1→3)-β-d-glucan varied from 0.2 to 16.0 ng m⁻³. The ratio of (1→3)-β-d-glucan mass in fragment size fraction to that in spore size fraction (F/S) varied from 0.011 to 2.163. The mass ratio was higher in winter (average=1.017) than in summer (0.227) coinciding with a lower relative humidity in the winter. Assuming a mass-based F/S-ratio=1 and the spore size=3 μm, the corresponding number-based F/S-ratio (fragment number/spore number) would be 10³ and 10⁶, for the fragment sizes of 0.3 and 0.03 μm, respectively. These results indicate that the actual (field) contribution of fungal fragments to the overall exposure may be very high, even much greater than that estimated in our earlier laboratory-based studies.     

The physical characteristics of sulfur aerosols

A review of the physical characteristics of sulfur-containing aerosols, with respect to size distribution of the physical distributions, sulfur distributions, distribution modal characteristics, nuclei formation rates, aerosol growth characteristics, and in situ measurement, has been made.Physical size distributions can be characterized well by a trimodal model consisting of three additive lognormal distributions.When atmospheric physical aerosol size distributions are characterized by the trimodal model, the following typical modal parameters are observed:1. Nuclei mode – geometric mean size by volume, DGV_n, from 0.015 to 0.04 μm. σ_gn=1.6, nucler mode volumes from 0.0005 over the remote oceans to 9 μm³ cm⁻³ on an urban freeway.2. Accumulation mode – geometric mean size by volume, DGV_a, from 0.15 to 0.5 μm, σ_ga=1.6–2.2 and mode volume concentrations from 1 for very clean marine or continental backgrounds to as high as 300 μm³ cm⁻³ under very polluted conditions in urban areas.3. Coarse particle mode – geometric mean size by volume, DGV_c, from 5 to 30 μm, σ_gn=2–3, and mode volume concentrations from 2 to 1000 μm³ cm⁻³.It has also been concluded that the fine particles (D_p<2 μm) are essentially independent in formation, transformation and removal from the coarse particles (D_p>2 μm).Modal characterization of impactor-measured sulfate size distributions from the literature shows that the sulfate is nearly all in the accumulation mode and has the same size distribution as the physical accumulation mode distribution.Average sulfate aerodynamic geometric mean dia. was found to be 0.48±0.1 μm (0.37±0.1 μm vol. dia.) and σ_g=2.00±0.29. Concentrations range from a low of about 0.04 μg m⁻³ over the remote oceans to over 8 μg m⁻³ under polluted conditions over the continents.Review of the data on nucleation in smog chambers and in the atmosphere suggests that when SO₂, is present, SO₂-to-aerosol conversion dominates the Aitken nuclei count and, indirectly, through coagulation and condensation, the accumulation mode size and concentration. There are indications that nucleation is ubiquitous in the atmosphere, ranging from values as low as 2 cm⁻³ h⁻¹ over the clean remote oceans to a high of 6×10⁶ cm⁻³ h⁻¹ in a power plant plume under sunny conditions.There is considerable theoretical and experimental evidence that even if most of the mass for the condensational growth of the accumulation mode comes from hydrocarbon conversion, sulfur conversion provides most of the nuclei.     

Particle size distribution of n-alkanes and polycyclic aromatic hydrocarbons (PAHS) in urban and industrial aerosol of Algiers,Algeria

The distribution of ambient air n-alkanes and polycyclic aromatic hydrocarbons (PAHs) associated to particles with aerodynamic diameters lesser than 10 μm (PM₁₀) into six fractions (five stages and a backup filter) was studied for the first time in Algeria. Investigation took place during September of 2007 at an urban and industrial site of Algiers. Size-resolved samples (<0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and7.2–10 μm) were concurrently collected at the two sampling sites using five-stage high-volume cascade impactors. Most of n-alkanes (~72 %) and PAHs (~90 %) were associated with fine particles ≤1.5 μm in both urban and industrial atmosphere. In both cases, the n-alkane contents exhibited bimodal or weakly bimodal distribution peaking at the 0.95–1.5-μm size range within the fine mode and at 7.3–10 μm in the coarse mode. Low molecular weight PAHs displayed bimodal patterns peaking at 0.49–0.95 and 7.3–10 μm, while high molecular weight PAHs exhibited mono-modal distribution with maximum in the <0.49-μm fraction. While the mass mean diameter of total n-alkanes in the urban and industrial sites was 0.70 and 0.84 μm, respectively, it did not exceed 0.49 μm for PAHs. Carbon preference index (~1.1), wax% (10.1–12.8), and the diagnostic ratios for PAHs all revealed that vehicular emission was the major source of these organic compounds in PM₁₀ during the study periods and that the contribution of epicuticular waxes emitted by terrestrial plants was minor. According to benzo[a]pyrene-equivalent carcinogenic power rates, ca. 90 % of overall PAH toxicity across PM₁₀ was found in particles ≤0.95 μm in diameter which could induce adverse health effects to the population living in these areas.     

Uptake of Cd(II) and Pb(II) by microalgae in presence of colloidal organic matter from wastewater treatment plant effluents

The present study addresses the key issue of linking the chemical speciation to the uptake of priority pollutants Cd(II) and Pb(II) in the wastewater treatment plant effluents, with emphasis on the role of the colloidal organic matter (EfOM). Binding of Cd(II) and Pb(II) by EfOM was examined by an ion exchange technique and flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry in parallel to bioassays with green microalga Chlorella kesslerii in ultrafiltrate (<1 kDa) and colloidal isolates (1 kDa to 0.45 μm). The uptake of Cd by C. kesslerii was consistent with the speciation analysis and measured free metal ion concentrations, while Pb uptake was much greater than that expected from the speciation measurement. Better understanding of the differences in the effects of the EfOM on Cd(II) and Pb(II) uptake required to take into account the size dependence of metal binding by EfOM.     

Identification of magnetic particulates in road dust accumulated on roadside snow using magnetic, geochemical and micro-morphological analyses

The aim of this study is to test the applicability of snow surveying in the collection and detailed characterization of vehicle-derived magnetic particles. Road dust extracted from snow, collected near a busy urban highway and a low traffic road in a rural environment (southern Finland), was studied using magnetic, geochemical and micro-morphological analyses. Significant differences in horizontal distribution of mass specific magnetic susceptibility (χ) were noticed for both roads. Multi-domain (MD) magnetite was identified as the primary magnetic mineral. Scanning electron microscope (SEM) analyses of road dust from both roads revealed: (1) angular-shaped particles (diameter ∼1-300 μm) mostly composed of Fe, Cr and Ni, derived from circulation of motor vehicles and (2) iron-rich spherules (d ∼ 2-70 μm). Tungsten-rich particles (d < 2 μm), derived from tyre stud abrasion were also identified. Additionally, a decreasing trend in χ and selected trace elements was observed with increasing distance from the road edge.     

On the sensitivity of particle size to relative humidity for Los Angeles aerosols

A TDMA system (Tandem Differential Mobility Analyzer; Rader D.J. and McMurry P.H. J. Aerosol Sci. 17, 771–787, 1986) was used to measure the sensitivity of particle size to relative humidity for monodisperse Los Angeles aerosols. Measurements were made at Claremont, CA on 13 days between 19 June and 3 September 1987, in conjunction with the Southern California Air Quality Study (SCAQS). The particle sizes that were studied ranged from 0.05 μm to 0.5 μm diameter at ambient relative humidity (typically 45–65%).The data provide clear evidence that these atmospheric aerosols were externally mixed. Monodisperse ambient aerosols were often found to split into nonhygroscopic (no water uptake) and hygroscopic portions when humidified. An average of 30% of the particles in the 0.2–0.5 μm range were nonhygroscopic. However, the proportion of the particles that was nonhygroscopic varied considerably from day to day and was, on occasion, as high as 70–80% of the particles. There was no clear evidence for nonhygroscopic 0.05 μm particles, but the data are not definitive on this point.The data also show that for the hydrophilic aerosol fraction, the larger particles (0.4–0.5 μm) grew more when humidified than did smaller particles (0.05–0.2 μm). As relative humidities were increased from 50% to 90%, particle diameters grew by average factors of 1.46 ±0.02 (for 0.5 μm particles), 1.49 ± 0.08 (0.4 μm), 1.19 ± 0.08 (0.2 μm) and 1.12 ± 0.05 (0.05 μm). Similarly, when particles were dried from 50% RH to 6–10% RH, particle diameters changed by factors ranging from 0.94 ± 0.03 (0.5 μm) to 0.98 ± 0.01 (0.05 μm).     

Antifungal efficacy of some natural phenolic compounds against significant pathogenic and toxinogenic filamentous fungi

In terms of food safety, species of the Fusarium, Aspergillus and Penicillium genera are considered the most significant because they produce the great majority of known mycotoxins. Developing resistance against commonly used fungicides have become a critical problem in area such as agriculture, the storage and production of food and even in human medicines. The need for research and development of new alternative antifungal treatment based on natural antifungal substances is obvious. Here, the antifungal efficacy of 21 phenolic components of essential oils and plant substances were tested against these filamentous fungi with respect to their different molecular structures. Minimum inhibitory concentration values MIC₅₀ and MIC₁₀₀ were successfully estimated for 15 substances by means of probit analysis. Thymol and carvacrol were evaluated as the most effective. The MIC₅₀ values for thymol ranged from 30 to 52 μg mL⁻¹. The MIC₁₀₀ values for thymol ranged from 76 to 255 μg mL⁻¹, respectively. For carvacrol, the MIC₅₀ values ranged from 37 to 76 μg mL⁻¹, and the MIC₁₀₀ ranged from 131 to 262 μg mL⁻¹. The results also revealed differences in the efficacy of phenols depending on molecular structures and different inter-species sensitivity.     

Polychlorinated dibenzo-p-dioxin and dibenzofuran in urban air of an Andean city

Particle-bound polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air were monitored together with particulate matter less than 10 μm (PM₁₀) at three sampling sites of the Andean city of Manizales, Colombia; during September 2009 and July 2010. PCDD/Fs ambient air emissions ranged from 1 fg WHO-TEQ m⁻³ to 52 fg WHO-TEQ m⁻³ in particulate fraction. The PM₁₀ concentrations ranged from 23 μg m⁻³ to 54 μg m⁻³. Concentrations of PM₁₀ and PCDD/Fs in ambient air observed for Manizales - a medium sized city with a population of 380 000 - were comparable to concentrations in larger cities. The highest concentrations of PCDD/Fs and PM₁₀ found in this study were determined at the central zone of the city, characterized by public transportation density, where diesel as principal fuel is used. In addition, hypothetical gas fractions of PCDD/Fs were calculated from theoretical K_p data. Congener profiles of PCDD/Fs exhibited ratios associated with different combustion sources at the different sampling locations, ranging from steel recycling to gasoline and diesel engines. Taking into account particle and gas hypothetical fraction of PCDD/Fs, Manizales exhibited values of PCDD/Fs equivalent to rural and urban-industrial sites in the southeast and center of the city respectively. Poor correlation of PCDDs with PM₁₀ (r = −0.55 and r = 0.52) suggests ambient air PCDDs were derived from various combustion sources. Stronger correlation was observed of PCDFs with PM₁₀. Poor correlation between precipitation and reduced PM₁₀ concentration in ambient air (r = −0.45) suggested low PM₁₀ removal by rainfall.