Larger Particle Size Fractions Research Articles

Inhibiting effects of humic acid on iron flocculation hindered As removal by electro-flocculation on air cathode iron anode

Activated carbon air cathode combined with iron anode oxidation-flocculation synergistic Arsenic (As) removal was a new groundwater purification technology with low energy consumption and high efficiency for groundwater with high As concentration. The presence of organic matter such as humic acid (HA) had ambiguous effects on formation of organic colloids in the system. The effects of the particle size distribution characteristics of these colloids on the formation characteristics of flocs and the efficiency of As purification was not clear. In this work, we used five different pore size alumina filter membranes to separate mixed phase solutions and studied the corresponding changes in iron and arsenic concentrations in the presence and absence of humic acid conditions. In the presence of HA, the arsenic concentration of < 0.05 µm particle size components was 1.01, 1.28, 3.07, 7.69, 2.85 and 1.24 times of that in the absence of HA. At the same time, the arsenic content in 0.05–0.1 µm and 0.1–0.45 µm particle size components was also higher than that in the system without HA, which revealed that the presence of HA hindered the flocculation behavior of As distribution to higher particle sizes in the early stage of the reaction. The presence of HA affected the flocculation rate of iron flocs from small to large particle size fractions and it had limited effect on the behavior of large-size flocs in adsorption of As. These results provide a theoretical basis for targeted, rapid, and low consumption synergistic removal of arsenic and organic compounds in high arsenic groundwater.

Impact of ultrafine particles and total particle number concentration on five cause-specific hospital admission endpoints in three German cities

IntroductionNumerous studies have shown associations between daily concentrations of fine particles (e.g., particulate matter with an aerodynamic diameter ≤2.5 µm; PM2.5) and morbidity. However, evidence for ultrafine particles (UFP; particles with an aerodynamic diameter of 10–100 nm) remains conflicting. Therefore, we aimed to examine the short-term associations of UFP with five cause-specific hospital admission endpoints for Leipzig, Dresden, and Augsburg, Germany. Material and methodsWe obtained daily counts of (cause-specific) cardiorespiratory hospital admissions between 2010 and 2017. Daily average concentrations of UFP, total particle number (PNC; 10–800 nm), and black carbon (BC) were measured at six sites; PM2.5 and nitrogen dioxide (NO2) were obtained from monitoring networks. We assessed immediate (lag 0–1), delayed (lag 2–4, lag 5–7), and cumulative (lag 0–7) effects by applying station-specific confounder-adjusted Poisson regression models. We then used a novel multi-level meta-analytical method to obtain pooled risk estimates. Finally, we performed two-pollutant models to investigate interdependencies between pollutants and examined possible effect modification by age, sex, and season. ResultsUFP showed a delayed (lag 2–4) increase in respiratory hospital admissions of 0.69% [95% confidence interval (CI): −0.28%; 1.67%]. For other hospital admission endpoints, we found only suggestive results. Larger particle size fractions, such as accumulation mode particles (particles with an aerodynamic diameter of 100–800 nm), generally showed stronger effects (respiratory hospital admissions & lag 2–4: 1.55% [95% CI: 0.86%; 2.25%]). PM2.5 showed the most consistent associations for (cardio-)respiratory hospital admissions, whereas NO2 did not show any associations. Two-pollutant models showed independent effects of PM2.5 and BC. Moreover, higher risks have been observed for children. ConclusionsWe observed clear associations with PM2.5 but UFP or PNC did not show a clear association across different exposure windows and cause-specific hospital admissions. Further multi-center studies are needed using harmonized UFP measurements to draw definite conclusions on the health effects of UFP.

Detection of SARS-CoV-2 in Air and on Surfaces in Rooms of Infected Nursing Home Residents.

There is an ongoing debate on airborne transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) as a risk factor for infection. In this study, the level of SARS-CoV-2 in air and on surfaces of SARS-CoV-2 infected nursing home residents was assessed to gain insight in potential transmission routes. During outbreaks, air samples were collected using three different active and one passive air sampling technique in rooms of infected patients. Oropharyngeal swabs (OPS) of the residents and dry surface swabs were collected. Additionally, longitudinal passive air samples were collected during a period of 4 months in common areas of the wards. Presence of SARS-CoV-2 RNA was determined using RT-qPCR, targeting the RdRp- and E-genes. OPS, samples of two active air samplers and surface swabs with Ct-value ≤35 were tested for the presence of infectious virus by cell culture. In total, 360 air and 319 surface samples from patient rooms and common areas were collected. In rooms of 10 residents with detected SARS-CoV-2 RNA in OPS, SARS-CoV-2 RNA was detected in 93 of 184 collected environmental samples (50.5%) (lowest Ct 29.5), substantially more than in the rooms of residents with negative OPS on the day of environmental sampling (n = 2) (3.6%). SARS-CoV-2 RNA was most frequently present in the larger particle size fractions [>4 μm 60% (6/10); 1-4 μm 50% (5/10); <1 μm 20% (2/10)] (Fischer exact test P = 0.076). The highest proportion of RNA-positive air samples on room level was found with a filtration-based sampler 80% (8/10) and the cyclone-based sampler 70% (7/10), and impingement-based sampler 50% (5/10). SARS-CoV-2 RNA was detected in 10 out of 12 (83%) passive air samples in patient rooms. Both high-touch and low-touch surfaces contained SARS-CoV-2 genome in rooms of residents with positive OPS [high 38% (21/55); low 50% (22/44)]. In one active air sample, infectious virus in vitro was detected. In conclusion, SARS-CoV-2 is frequently detected in air and on surfaces in the immediate surroundings of room-isolated COVID-19 patients, providing evidence of environmental contamination. The environmental contamination of SARS-CoV-2 and infectious aerosols confirm the potential for transmission via air up to several meters.

Raman spectroscopic evaluation of crystallinity, chemical composition and stability of pharmaceutical powder aerosols

Raman spectroscopy was used to evaluate the effects of temperature and humidity on the physicochemical stability of inhalable spray-dried (SD) powders containing budesonide (BUD) and crystalline or amorphous lactose. Powders prepared by spray drying of BUD-lactose solution or suspension containing lactose crystals in BUD solution were stored for 0, 1 and 7 days at 25 °C/60 RH or 40 °C/75 RH. Bulk powders along with the large and small particle size fractions collected on stages 2 and 5, respectively, of the Next Generation Impactor (NGI) were chemically characterised. SD powder from solution contained BUD and lactose in amorphous form and both components were homogeneously distributed in bulk and in the particles collected from the two NGI stages. In contrast, SD powder from suspension showed heterogeneous distribution of lactose and drug in the particles containing crystalline lactose. After 1 day of storage at either condition, recrystallisation and changes in the chemical composition of the particles for the SD powder from solution occurred. The number of drug-only particles increased by 70 on stage 5, whereas most particles on stage 2 still contained both drug and lactose. These changes were not observed in the SD powder from suspension after storage, confirming superior stability of the SD powder obtained from suspension.

Characterization of PM-Bound Heavy Metal at Road Environment in Tianjin: Size Distribution and Source Identification

To determine the size distribution and source identification of PM-bound heavy metals in roadside environments, four different particle size (&lt;0.2 μm, 0.2–0.5 μm, 0.5–1.0 μm and 1.0–2.5 μm) samples were collected and analyzed from four different types of roads during the summer of 2015 in Tianjin. The results showed that the concentrations of PM-bound heavy metal from the roadside environment sampling sites were 597 ± 251 ng/m3 (BD), 546 ± 316 ng/m3 (FK), 518 ± 310 ng/m3 (JY) and 640 ± 237 ng/m3 (WH). There were differences in the concentrations of the heavy metal elements in the four different particle size fractions. The concentrations of Cu, Zn, Cd, Sn and Pb were the highest in the larger particle size fraction (0.5–2.5 μm). Cd, Cu, Zn and Pb were the elements that indicated emissions from tire wear and brake pad wear. The concentrations of Cr, Co and Ni were the highest in the smallest particle size fraction (&lt;0.5 μm), indicating that motor vehicle exhaust was their main source. The correlation analysis results showed that there are differences in the concentration, distribution and correlation of different PM-bound heavy metals in different particle size fractions. The PCA results show that the accumulative interpretation variances of PM0.2, PM0.2–0.5, PM0.5–1.0 and PM1.0–2.5 reached 80.29%, 79.56%, 79.57% and 71.42%, respectively. Vehicle exhaust was the primary source of PM-bound heavy metal collected from the roadside sampling sites, while brake pad wear and tire wear were the second most common sources of the heavy metal.

Redistribution of iron oxides in aggregates induced by pe + pH variation alters Cd availability in paddy soils

In this study, the effect of unstable pe + pH levels on the transformation of Fe oxides in different-sized soil fractions and its impact on Cd speciation were explored. Paddy soil samples collected from two locations in China were cultivated for two months under one of four pe + pH conditions: flooding + N2 (T1), flooding (T2), 70% water holding capacity (T3), and 70% water holding capacity + O2 (T4). Chemical analysis and X-ray diffraction (XRD) were used to identify the mineralogical phases and species of Fe and Cd in paddy soils. The results show that the decrease of soil pe + pH level favored the transformation of well-crystallized Fe oxides (Fec), such as hematite and goethite, into poorly-crystallized (Feo) and organically-complexed (Fep) forms. The transformation promoted the binding of Cd to Fe oxides and was primarily responsible for up to a 41.8% decrease of soil DTPA (diethylenetriaminepentaacetic acid)-extractable-Cd content. In addition, the decline in pe + pH value reduced Fe concentrations in soil particle fractions of 0.2–2-mm (17.8%–30.6%) and <0.002-mm (20.7%–31.7%) of the two flooding treatments. The decreased Fe concentrations were closely associated with less Fec contents in these same fractions and more Feo and Fep in coarser aggregates (P < 0.01). Importantly, the increase in contents of Feo and Fep in the 0.002–2 mm fraction were significantly correlated with content of Fe-/Mn-oxide-bound Cd (OX-Cd) in larger particle-size fractions (P < 0.01). Furthermore, the increasing content of OX-Cd played a crucial role in reducing DTPA-Cd content. This study demonstrates that low pe + pH values favor the transformation of crystalline Fe oxides into a poorly-crystallized and organically-complexed phase, which facilitates Cd accumulation in coarser aggregates and enhances Cd stability in paddy soils.

Activity size distributions of radioactive airborne particles in an arid environment: a case study of Kuwait

Atmospheric radioactive airborne released from several natural and artificial sources can travel for long distances and disperse in different directions. Both the physical and chemical characteristics of the atmospheric aerosols control this movement. The concentrations of 210Pb, 210Po, 7Be, 40K and 137Cs radionuclides in the ground surface air were determined in three particle sizes (2.4-10.2, 0.73-2.4 and less than 0.73μm). High-volume air samples were collected from five different locations representing the five governorates of Kuwait using high-volume air samplers connected to a five-stage cascade impactor. The radioactivity concentrations of almost all fallout radionuclides were concentrated on the fine particle size fractions. The cosmogenic 7Be radioactivity level in all locations was relatively comparable and varied between 1.16 and 18.38mBq/m3, with a geometric mean value of 6.80mBq/m3. 137Cs was infrequently recorded with concentration varied between 4 and 14.3μBq/m3. The geometric mean levels of the 210Po and 210Pb were 0.899mBq/m3 and 1.03mBq/m3, respectively, indicating that anthropogenic sources likely enrich 210Po. 40K was concentrated on large particle size fractions with a geometric mean value of 2.34mBq/m3, reflecting the effects of the local dust sources. It was concluded that the radiological hazards due to airborne radioactive inhalation are low and can be negligible, where the annual estimated effective dose is about 64.0μSv. The radioactive airborne measurements compose the base of estimating the aerosols residence time, resuspension rate of dust, soil redistribution and source apportionment, particularly the 210Pb and 210Po radionuclides.

Effect of Soil Washing Using Oxalic Acid on Arsenic Speciation and Bioaccessibility in Soils

Objectives : Soil washing process has been widely applied for remediation of contaminated soil with arsenic and heavy metals in Korea. The application of soil washing could change physical and chemical properties of soils and metal speciation in soil, which could affect the risk to the environment and human health. Thus, it is necessary to evaluate metal and arsenic speciation and their mobility in soil after soil remediation in order to evaluate effectiveness of soil remediation process and manage soil quality effectively. The purpose of this study is to evaluate the risk of arsenic in soil after remediation of arsenic contaminated soil via soil washing.Methods : Arsenic contaminated soil collected at the abandoned mine site was washing with oxalic acid. The arsenic contaminated soil was divided into 2,000-500 µm, 500-250 µm, 250-150 µm, 150-75 µm, 75-38 µm, &lt; 38 µm particle size fractions. After soil washing for each soil particle size fraction, arsenic speciation via sequential extraction and bioaccessibility in the soils were evaluated. Results and Discussion : Generally, arsenic and metal concentrations were higher in the soil fractions with smaller particle sizes. But high arsenic concentration was observed at the large particle size fractions (&gt;250 µm), which might be due to the presence of mineral phases containing arsenic such as arsenolite or pyrite in the large particle size fraction soils. Sequential extraction showed that arsenic in mine soils was majorly present as associated with amorphous oxides. After soil washing with oxalic acid, arsenic in soils associated with amorphous oxides was greatly decreased, whereas the arsenic fraction associated sulfide and organic matter was increased. Soil washing decreased the bioaccessible arsenic concentration (mg/kg) in soil, but increased the bioaccessibility (%) depending on the soil characteristics. Conclusions : Soil washing changed arsenic species in soils, which affected mobility and risk of arsenic in soil.

Soil organic carbon pool and chemical composition under different types of land use in wetland: Implication for carbon sequestration in wetlands

This study was conducted to understand how different wetland vegetation-land use types influenced the storage and stability of soil organic carbon (SOC) in surface soils. We determined the concentration and chemical composition of SOC in both density (including light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) and particle size fractions (including <2μm, 2-63μm, 63-200μm and 200-2000μm) in four wetland land use types covered with different vegetation: lake-sedge, reed, willow and poplar wetlands. Results showed that the concentrations and stock of SOC and LFOC in willow and poplar wetlands were significantly higher than those in lake-sedge and reed. However, a higher proportion of alkyl-C and a lower proportion of O-alkyl-C were observed in lake-sedge and reed wetlands than in willow and poplar, suggesting that accumulated C in willow and poplar wetlands was less stable than that in lake-sedge and reed. For all particle-size fractions except the silt (2-63μm), the SOC concentrations were highest in willow and lowest in reed wetland surface soils, while their alkyl-C/O-alkyl-C (A/O-A) and hydrophobic-C/hydrophilic-C ratios progressively decreased from lake-sedge and reed wetland surface soils to poplar and willow surface soils. Moreover, the ratios of A/O-A and hydrophobic-C/hydrophilic-C in surface soils generally decreased with increasing concentrations of SOC in particle-size fractions, with these stability indexes being lowest in the largest particle-size fraction. These results indicate that the wetland vegetation-land use types that could incorporate more C into finer particle-size fractions had a greater potential for sequestering more stable C in such wetland ecosystems. Different wetland vegetation-land use types resulted in significant changes in the concentration and chemical structure of SOC, which could affect soil C sequestration and dynamics, C cycling in wetland ecosystems. Although both willow and poplar forests could increase SOC stock, the stability of SOC in willow wetland was higher. Therefore, on balance (stock and stability) the land use of wetland for willow forest could be a more promising way for enhancing soil C sequestration in wetlands.

In vitro lung and gastrointestinal bioaccessibility of potentially toxic metals in Pb-contaminated alkaline urban soil: The role of particle size fractions.

Potentially toxic metals (PTMs), associated with different size particles in soil, may play an important role in adverse health effect and risk for human. The objective is to evaluate the lung and gastrointestinal bioaccessibility and risk of PTMs in Pb-contaminated alkaline urban soil depending on the particle size fractions. The size fractions of 50-250μm, 5-50μm, 1-5μm, <1μm in Pb-contaminated alkaline urban soil from Baoji Heavy Industrial Base City, NW China, were screened by Sequential Wet Sieving Separation Procedure (SWSSP) based on Stokes' Law. The concentrations of 9 potentially toxic metals (As, Ba, Co, Cr, Cu, Mn, Ni, Pb and Zn) in each particle size fractions were characterized by ICP-OES and ICP-MS, and the in vitro bioaccessibility dependent of size fractions were evaluated by the simulation fluids of Artificial Lysosomal Fluid (ALF) and Gamble for lung, PBET, SBET, IVG, SBRC, UBM for gastric and intestinal, respectively. Health risks were assessed considering simulated external exposure using intestinal and lung bioaccessibility. The lung and gastrointestinal bioaccessibility and exposure risks of PTMs in fine particle size (i.e. <1μm) was higher than larger particle size fractions (i.e. 50-250μm, 5-50μm, 1-5μm), however, some different variations of bioaccessibility observed the simulation fluids and time dependent. In case of single PTMs, the lung bioaccessibilities of PTMs in ALF were higher than those in Gamble fluids, most prominent in Co, Cu, Mn and Zn, while the gastrointestinal [G+I] bioaccessibility of PTMs was less than those in gastric [G], like Cu, Mn, Pb and Zn mostly. The non-carcinogenic risks of these PTMs to children via inhalation were acceptable and higher than those of adults, but reverse for carcinogenic risk. Comparatively, the non-carcinogenic and carcinogenic risks of PTMs via ingestion pathway were both higher than those for adults. Although the risks from ingestion were in acceptable range, the total carcinogenic risks for children were more than 10-4, which would bring carcinogenic risks and should be paid attention to. It was noted that the toxic metal, Co in all size fractions was the most important contributor for noncarcinogenic risks and Cr mostly for carcinogenic risks via inhalation pathway for adults and children in local areas. However, Pb was the most important contributor for noncarcinogenic risk both for adults and children via ingestion pathway relative to Co and Cr for carcinogenic risks through hand-to-mouth ingestion. Those observations demonstrated the important role that the smaller particle fractionations in Pb-contaminated alkaline soil played in both bioaccessibility and the refinement of human health-risk assessments for the inhalation and ingestion pathway.

Extraction of Li and Co from industrially produced Li-ion battery waste – Using the reductive power of waste itself

Industrially produced spent lithium-ion batteries (LIBs) waste contain not only strategic metals such as cobalt and lithium but also impurity elements like copper, aluminum and iron. The current work investigates the distribution of the metallic impurity elements in LIBs waste, and their influence on the acid dissolution of target active materials. The results demonstrate that the presence of these, naturally reductive, impurity elements (e.g. Cu, Al, and Fe) can substantially promote the dissolution of active materials. Through the addition of Cu and Al-rich larger size fractions, the extraction efficiencies of Co and Li increased up to over 99%, to leave a leach residue that is rich in graphite. By this method, the use of high cost reductants like hydrogen peroxide or ascorbic acid could be avoided. More importantly, additional Co and Li associated with the Cu and Al electrode materials could be also recovered. This novel approach contributes not only to improved reduction efficiency in LIBs waste leaching, but also to improved total recovery of Co and Li from LIBs waste, even from the larger particle size fractions, which are typically lost from circulation.

Evaluation of the strength, sorption and thermal properties of bamboo plastic composites

Natural fiber plastic composites were made from Nigerian grown bamboo (Bambusa vulgaris) and high density polyethylene (HDPE) by extrusion and evaluated for strength, sorption and thermal properties. Composites were manufactured using two different screened bamboo particle size fractions (<2 mm and < 0.5 mm). The composites were tested for flexural properties, water sorption, melt flow and thermal properties. The melt viscosities at 190oC were 22.3 ± 0.91 kPa·s (<2 mm) and 27.4 ± 1.2 kPa·s (<0.5 mm). The results obtained indicated that the composites made with the smaller particle size fraction had higher flexural strength (37.4 ± 1.0 MPa) and modulus of elasticity (2.0 ± 0.2 GPa) than those made with the larger particle size fraction (29.9 ± 1.1 MPa and 1.7 ± 0.1 GPa). Dynamic mechanical analysis (DMA) also showed higher dynamic storage modulus for the <0.5 mm particle-based composites than those made from the <2 mm particle size fraction due to higher density and better interfacial interaction between the fiber and matrix. Also, the composites made with the smaller particles and were more dimensionally stable (water absorption of 5.4% versus 18.5% at 61 d). The bamboo composites had thermal stablility range of 265 – 279oC (onset degradation temperature). The composites made with the smaller bamboo particles possessed the better properties in comparison with those made from the <2 mm. Particle size and density significantly affected the mechanical, physical, thermal and rheological properties of the composites evaluated. Keywords: Bambusa vulgaris, flexural properties, natural fiber plastic composites, particle size

Development of a novel fractal-like kinetic model for elucidating the effect of particle size on the mechanism of hydrolysis and biogas yield from ligno-cellulosic biomass

Abstract The effect of particle size on hydrolysis and biogas production kinetics from a typical ligno-cellulosic biomass was assessed by studying the anaerobic co-digestion of fixed amount of rice husk and cow dung mixture using a newly developed fractal-like kinetic model. British Standard (BS) sieves were used to obtain varying particles size fractions ranging from 0.150 to 0.212 mm, 0.212–0.300 mm, 0.300–0.600 mm, 0.600–1.000 mm and 1.000–1.700 mm from oven dried, milled rice husk and pulverized, dried cow dung respectively. These particle size fractions from both biomass were mixed in a ratio of 1:1 after which, they were loaded into batch reactors and digested anaerobically at ambient conditions for 75 days. Hydrolysis of ligno-cellulosic biomass was observed to depend on the fractal exponent (h), which indexed the presence of inaccessible regions in ligno-cellulosic biomass. Also, hydrolysis was observed to depend on two other intrinsic factors that comprised of the initial hydrolytic rate ( X o Y k o ′ ) and overall affinity constant ( k o ′ S o ) . Larger particle size fractions were associated with higher affinity but lower initial hydrolysis rate while, smaller particle size fractions were associated with lower affinity but higher initial hydrolysis rate. In addition, the fractal model compared favorably with the popular modified Gompertz equation.

Use of near infrared spectroscopy for the rapid low-cost analysis of waste papers and cardboards.

Analytical data and quantitative near infrared (NIR) spectroscopy models for various lignocellulosic components (including Klason lignin and the constituent sugars glucose, xylose, mannose, arabinose, galactose, and rhamnose), ash, and ethanol-soluble extractives were obtained for 53 samples of paper and cardboard. These samples were mostly the type of materials typically found in domestic wastes (e.g. newspapers, printing paper, glossy papers, food packaging). A number of the samples (48) were obtained by separating a sample, after milling, into two particle size fractions. It was found that the fractions containing the smaller particles typically had higher ash and Klason lignin contents and lower glucose and xylose contents than the larger particle size fractions. Nevertheless, all of the sample types had attractive total sugars contents (>50%), indicating that these could be suitable feedstocks for the production of biofuels and chemicals in hydrolysis-based biorefining technologies. NIR models of a high predictive accuracy (R2 of >0.9 for the independent validation set) were obtained for total sugars, glucose, xylose, Klason lignin, and ash, with values for the Root Mean Square Error of Prediction (RMSEP) of 2.36%, 2.64%, 0.56%, 1.98%, and 4.87%, respectively. Good NIR models (R2 of >0.8) were also obtained for mannose, arabinose, and galactose. These results suggest that NIR spectroscopy is a suitable method for the rapid, low-cost, analysis of the major lignocellulosic components of waste paper/cardboard samples.

Stages in the life of a magnetic grain: Sediment source discrimination, particle size effects and spatial variability in the South African Karoo

Mineral magnetic properties are commonly used to trace the sources of river and lake sediments with the aim of identifying areas of a catchment experiencing the high rates of soil loss. In some areas, however, there is poor understanding of how magnetic properties are able to discriminate between potential sediment sources. The basis for mineral magnetic source discrimination between topsoils and subsurface material, over different rock parent materials, was investigated in the South African Karoo. The effects of particle size, soil development/alteration and diagenesis processes on the source discrimination were investigated. Good discrimination (up to 100% correct discrimination) was found between the sedimentary sources (soils and subsurface) and dolerite soils due to much higher concentrations of magnetic minerals in the dolerite. There was little evidence of alterations to magnetic properties in subsurface sediments, resulting in only a small ability of properties to differentiate between surface and subsurface sources. It was found that during the development of topsoils there was a loss of high coercivity weakly magnetic grains and an enrichment in small superparamagnetic and stable single domain grains. Particle size was strongly related to magnetic properties with almost all of the secondary superparamagnetic and stable single domain grains created during soil formation being concentrated in the <32μm fraction and the loss of high coercivity grains taking place primarily in the >125μm fractions. The small ability of sediment to discriminate between surface and subsurface sources was based upon the dissolution of primarily χfd and χARM carrying grains in the <32μm fractions and to a lesser extent the 63–32μm fraction. As a result it was recommended that source tracing with the <32μm fraction of soils and sediment should be treated separately from the 63–32μm and larger particle size fractions. The relationships between particle size and magnetic properties were fairly consistent in all soil samples in each source group, raising the possibility that reliable correction factors could be developed for each source group.

Mastication effects on carotenoid bioaccessibility from mango fruit tissue

The release of carotenoids from fresh fruits or vegetables is determined by the encapsulating plant tissue matrix, intracellular carotenoid location within the cell, and the mastication process. The objectives of this study were to assess the particle sizes obtained after mastication of mango fruit tissue, and how the resulting degree of plant tissue rupture affects carotenoid bioaccessibility. A fine and a coarse chewer were selected after screening 20 healthy volunteers for in vivo human mastication, and the collected chewed boluses were subjected to wet sieving fractionation, followed by an in vitro gastric and small intestinal digestion model. Confocal micrographs show that the smallest particle size fraction (0.075mm) consists mostly of fragmented cells and the largest size fraction (2.8mm) contains bulky clusters of whole cells and vascular fibers. Higher amounts of total carotenoids (211–320μg/100g) were observed in the larger particle size fraction (2.8mm) relative to the 1mm (192–249μg/100g) and 0.075mm fractions (136–199μg/100g). Smaller particles showed a greater % release of total carotenoids after in vitro digestion. Xanthophyll derivatives are more bioaccessible than β-carotene for all particle sizes. The effects of particle size or degree of fine vs coarse chewing are unexpectedly small (p>0.05), but the process of chewing substantially reduced the release of β-carotene and xanthophylls by 34% and 18%, respectively. While there is a (small) particle size effect, this appears to not be the primary factor controlling bioaccessibility for soft tissues such as mango, in contrast to previous reports that a single cell wall appears to be enough to prevent bioaccessibility of carotenoids in more robust carrot tissues.

Accelerated solvent extraction of lipids from Amaranthus spp. seeds and characterization of their composition

Standard Soxhlet extraction and accelerated solvent extraction (ASE) methods were compared for the isolation of lipids from different particle size fractions of milled amaranth seeds. Particle size was crucial for the extract yield, which was 9 times higher in case of the finest fraction (<0.23 mm) as compared with the largest particle size fraction (>0.5 mm). Soxhlet and ASE gave similar yields, however extraction rate in case of ASE was several times faster. Response surface methodology (RSM) was used to optimize the ASE parameters for maximizing extract yield from amaranth seeds. Particles size fractions (≤0.23 mm, 0.23–0.5 mm, 0.5–1 mm), extraction time (5–25 min) and temperature (40–110 °C) were selected as independent variables for a central composite design. The highest yield (13.72 g oil/100 g seeds) was obtained using the smallest particle size fraction at the temperature 90 °C and 17 min extraction time. The adequacy of the model was confirmed by extracting seed oil under optimum values given by a model. The content of triacylglycerols, squalene and fatty acid composition of oils were determined by HPLC and GC.

Particle Distribution and Composition of Retail Whole Wheat Flours Separated by Sieving

ABSTRACT The purpose of this study was to evaluate the differences among four retail whole wheat flours with respect to particle size distribution and composition of fractions separated by sieving. Interestingly, not only were significant differences discovered among the brands for particle size distribution, but lots within two of the brands were significantly different (P < 0.05), suggesting that flour particle size produced by the same company is not always consistent. Starch damage ranged from 4.67 to 7.69%. As expected, darker colors were associated with the larger particle size fractions, and the colors lightened as particle size decreased. This observation suggested that the differences in particle size resulted from differences in the degree to which the bran fraction of the kernel was milled, an observation substantiated by the distribution of ash in each fraction, which ranged from 0.37 to 38.0% of total ash. Distribution of protein ranged from 0.19 to 61.8% of total protein. These data are rele...

Performance of dust allergen carpet samplers in controlled laboratory studies

Allergens and other pollutants in house dust are collected using a variety of dust samplers that are assumed to operate similarly. This factorial design study compared sampler performance under controlled environmental conditions. House dust with known particle sizes (212-90, 90-45, and <45 μm) and allergen concentrations were sampled from new carpet squares with varying denier, pile height and pile densities. Dust mass and allergen recovery for total dust mites (Der p 1 and Der f 1), cat (Fel d 1) and cockroach allergen (Bla g 1) were assessed using the Eureka Mighty Mite (EURK), the High Volume Small Surface Sampler (HVS), or the American Industrial Hygiene Association (AIHA) method. Allergen concentrations were quantified using enzyme-linked immunosorbent assays, and dust mass results were corrected for carpet fiber shedding. Samplers were compared by exploring mass collection efficiency (CE=fiber corrected dust mass/applied dust mass) and concentration ratio (CR=allergen concentration in collected sample/allergen concentration in test dust). Test dust allergen concentrations varied by particle size fraction due to varying laboratory performance over time. The EURK and HVS samplers had CEs of 41-63% in the small and medium particle size fractions, and collected less than 20% of the available dust from the large size fraction. The AIHA CE ranged from 10% to 17% in the medium and small particle size fractions, but collected little dust in the largest particle size fraction. The AIHA and HVS samplers were more likely to acquire more representative and less variable allergen CRs compared with the EURK method. Health studies that use allergen concentration as an exposure metric need to consider the implications of sampler performance when interpreting links to health outcomes and development of health-based standards for allergens in house dust.

Atmospheric deposition as a source of heavy metals in urban stormwater

Atmospheric deposition is one of the most important pathways of urban stormwater pollution. Atmospheric deposition, which can be in the form of either wet or dry deposition have distinct characteristics in terms of associated particulate sizes, pollutant types and influential parameters. This paper discusses the outcomes of a comprehensive research study undertaken to identify important traffic characteristics and climate factors such as antecedent dry period and rainfall characteristics which influences the characteristics of wet and dry deposition of solids and heavy metals. The outcomes confirmed that Zinc (Zn) is correlated with traffic volume whereas Lead (Pb), Cadmium (Cd), Nickel (Ni), and Copper (Cu) are correlated with traffic congestion. Consequently, reducing traffic congestion will be more effective than reducing traffic volume for improving air quality particularly in relation to Pb, Cd, Ni, and Cu. Zn was found to have the highest atmospheric deposition rate compared to other heavy metals. Zn in dry deposition is associated with relatively larger particle size fractions (>10 μm), whereas Pb, Cd, Ni and Cu are associated with relatively smaller particle size fractions (<10 μm). The analysis further revealed that bulk (wet plus dry) deposition which is correlated with rainfall depth and contains a relatively higher percentage of smaller particles compared to dry deposition which is correlated with the antecedent dry period. As particles subjected to wet deposition are smaller, they disperse over a larger area from the source of origin compared to particles subjected to dry deposition as buoyancy forces become dominant for smaller particles compared to the influence of gravity. Furthermore, exhaust emission particles were found to be primarily associated with bulk deposition compared to dry deposition particles which mainly originate from vehicle component wear.