Accumulation Of Fine Particles Research Articles

The Dependence of PM Size Distribution from Meteorology and Local-Regional Contributions, in Valencia (Spain) - A CWT Model Approach

ABSTRACTThis paper combines an analysis of hourly air pollution measurements and daily meteorological data with backward air mass trajectories, in order to elucidate local/regional sources and processes (e.g., atmospheric dispersion/stagnation, dust resuspension, etc.) defining PM levels and size distribution in Valencia (Spain). Four size fractions of PM (PM10, PMCOARSE = PM10–PM2.5, PM2.5 and PM1) were independently studied. No chemical/physical interactions among the four different size categories were assumed. Wind dispersion of PM2.5 and PM1 was indicated, whereas atmospheric stagnation conditions triggered the accumulation of fine particles, mainly produced from local combustion. Wind blown dust enhanced PMCOARSE concentrations, particularly throughout warm periods when dry land facilitates dust resuspension. Hourly air mass trajectory points were analyzed by Concentration Weighted Trajectory (CWT) model and Potential Source Contribution Function (PSCF) on a 0.5° × 0.5° resolution grid. The outcome of CWT model and PSCF identified Iberian Peninsula, France, North-West Africa and the Mediterranean as potential exogenous PM source areas. Extreme events of all PM fractions were primarily associated with the prevalence of South-South West airflows, whereas Saharan dust PMCOARSE intrusions also emerged. The availability of hourly meteorological data and the analysis of the chemical species included in PM mass could further clarify the findings of this paper and remove uncertainties.

Impact of membrane addition for effluent extraction on the performance and sludge characteristics of upflow anaerobic sludge blanket reactors treating municipal wastewater

In this study, the impact of membrane incorporation for effluent extraction on the performance of an upflow anaerobic sludge blanket (UASB) reactor treating municipal wastewater was investigated in terms of system performance and sludge characteristics. A laboratory-scale system was operated in two different operational stages: (i) as a sole UASB reactor and (ii) as an anaerobic membrane bioreactor (AnMBR). Membrane incorporation induced an accumulation of fine particles and a decrease in extracellular polymeric substances (EPS), resulting in a decrease in particle size distribution (PSD) and, thus, a drop in sludge settleability. Deterioration of sludge settleability led to an increase in sludge washout, with a resultant increase in chemical oxygen demand (COD) and total suspended solids (TSS) in the UASB effluent. However, suspended solids-free permeate with an average COD of 42mg/L was obtained and despite the sludge bed deterioration, the average transmembrane pressure (TMP) value was 85mbar indicating no severe membrane fouling. Pyrosequencing analysis demonstrated the increase in microbial community indexes of the UASB sludge after membrane addition, exhibiting an increase in both richness and evenness. Considering all responses of the UASB reactor to membrane incorporation, the overall results put UASB reactor forward as a suitable alternative for coupling membranes in AnMBRs.

Inorganic particles increase biofilm heterogeneity and enhance permeate flux

This study investigated the influence of inorganic particles on the hydraulic resistance of biofilm grown on membrane surface during low-pressure dead-end ultrafiltration. Gravity-driven ultrafiltration membrane systems were operated during several weeks without any flushing or cleaning. Smaller (kaolin d0.5 = 3.6 μm) or larger (kaolin with diatomaceous earth 50/50%, d0.5 = 18.1 μm) particles were added to pre-filtered creek water or to unfiltered creek water. It was demonstrated in both experiments that presence of finer particles in the feed water (kaolin) induced formation of compact and homogeneous biofilm structure. On the other hand presence of the larger particles (diatomite) helped to counterbalance the effect of fine particles due to the formation of more heterogeneous and permeable biofilm structure. The hydraulic resistance of biofilms formed with fine particles was significantly higher than the resistance of biofilm formed in (1) absence of any inorganic particles or (2) in presence of the mixed particle population. The membrane orientation (vertical or horizontal) determined which particles were accumulating at the membrane surface, with structural differences shown by Scanning Electron Microscopy (SEM). For vertical membranes, the larger particles were selectively removed due to sedimentation and did not contribute to the biofilm development. Thus the selection of smaller particles due to vertical membrane configuration negatively affected the biofilm structure and permeation rates, and such selective accumulation of fine particles should be avoided.

Implications of changes in solids retention time on long term evolution of sludge filterability in anaerobic membrane bioreactors treating high strength industrial wastewater

Long-term experiments were conducted to assess the impact of changing the solids retention time (SRT) on sludge filterability in anaerobic membrane bioreactors (AnMBRs), treating corn-based bioethanol thin stillage. Well established parameters, such as capillary suction time (CST) and specific resistance to filtration (SRF), developed for sludge dewatering, were used to evaluate the SRT effect on sludge filterability. Our results clearly demonstrated that SRT is one of the most important factors influencing sludge filterability in AnMBRs. SRT effects the accumulation of fine particles and solutes, which were found to affect attainable flux and fouling, in reactor broth. A better filterability was observed at a SRT of 20 days compared to elevated SRTs, i.e. 50 days. A clear correlation between sludge filtration characteristics and membrane filtration resistance could not be established especially at short SRTs, whereas many parameters such as total suspended solids (TSS), CST, soluble microbial products (SMP) and supernatant filterability were found to be mutually correlated. Net membrane fluxes between 9 and 13 L m−2 h−1 were obtained at 0.5 m s−1 cross-flow velocity and the long term fouling was controlled by using frequent filtration and backwash cycles.

First find of biogenic activity in the Palaeoproterozoic of the Singhbhum craton (E India)

Abstract The Palaeoproterozoic succession of the Singhbhum craton in E. India was hitherto considered as almost entirely siliciclastic and partly volcanogenic. Here we describe, from the fine-grained, tidally influenced shale facies of the Palaeoproterozoic Chaibasa Formation (2.1-1.6 Ga), a fine, originally more or less horizontal, wavy to strongly undulating (later locally deformed) lamination. Investigation of these laminae shows that they must be ascribed to the accumulation of fine particles on microbial mats that covered a sandy substrate. The structures must therefore be considered as stromatolites, features that are accepted as proof of the presence of micro-organisms, in this case most probably cyanobacteria. The interpretation of biogenic activity is supported by microscopic analysis. It is the first description of traces left by biogenic activity that took place in the Palaeoproterozoic of the Singhbhum craton.

Analysis of Segregation Data for a Dry Mineral-Based Construction Materials Plant

In this work, segregation data for seven commercial products at a dry mineral-based construction materials plant have been analyzed. The segregation manifests itself as an increase of the fines content to unacceptable levels at the end of complete emptying from a surge silo situated upstream of packing. Results for preliminary tests for sifting segregation and fluidization show the difficulty in estimating a priori the segregation patterns observed in practice. Knowledge of the segregation mechanisms occurring with similar materials at silo filling and the discharge flow pattern is utilized to explain the segregation at silo emptying: Accumulation of fine particles at the silo walls during filling and discharge in expanded flow cause fines-rich regions from the vicinity of walls in the lower parts of the silo to be withdrawn last. Large variations in the magnitude of segregation for each product cannot be explained for example by production run size, but are caused by size variations in the silo input, uneven distribution of fines over the heap surface during filling, unpredictable stagnant zones during discharge, and sampling procedure. Segregation at discharge mainly increases with increasing particle size distribution, but the product with the widest size distribution does not segregate the most. The width of the particle size distribution for the products correlates with the mass fraction of fine particles, and inclusion of a special additive (synthetic fibers) in very small proportions is also seen to affect segregation. Therefore, a regression model based on the mass fraction of fines and fibers was employed to organize the products according to the magnitude of segregation. Results for the model show that segregation does not always increase with an increase in the width of the particle size distribution and is negatively affected by inclusion of light and elongated particles (fibers).

Effects of process parameters and hopper angle on segregation of cohesive ternary powder mixtures in a small scale cylindrical silo

Segregation of two ternary powder mixtures at filling and at discharge of a 0.4m3 cylindrical silo has been investigated experimentally. The material distribution at silo filling was determined by sampling from the upper layers of the heap at different radial positions and with varying levels of fill. Discharge flow patterns were elaborated with tracer objects in the majority of experiments and the composition of the bulk solids during emptying was determined by sampling across the entire discharge stream. The effects of free fall distance and intermittent discharge and filling on segregation at filling as well as the effect of hopper angle on segregation at discharge were investigated. Furthermore, the influence of filling rate is discussed. Based on the results, side-to-side segregation with accumulation of fine particles to the silo walls clearly increases with increasing free fall distance. Segregation is also aggravated in situations where the silo is filled and discharged intermittently, because the shape of the powder bed’s surface changes when a portion of the silo contents is withdrawn. The effect of filling rate remains unclear and should be more deeply investigated in the future. The hopper angle determines the discharge flow pattern, i.e., funnel or mass flow, but the composition of the powder mixture towards the end of complete emptying is mainly determined by the material distribution at the levels of fill that are withdrawn last. The presented findings increase the understanding of the effect of process parameters and silo design on segregation, and can be used for mitigating the detrimental effects of segregation of bulk solids handled in silos.

Shift from native mussels to alien oysters: Differential effects of ecosystem engineers

Blue mussel ( Mytilus edulis) beds in the intertidal Wadden Sea (coastal North Sea) have been replaced by introduced Pacific oysters ( Crassostrea gigas). To test the effects of these habitat-generating suspension feeders on associated macrozoobenthos, a field experiment was designed. Circular plots (‘rings’) were composed either of oysters, mussels, both together or none at all. These four treatments were arranged in June 2006 in 5 blocks along low tide line. Rings enclose 3 m 2 of bare muddy sand surrounded by a 1-m-wide belt (10 m 2) of the densely packed epibenthic suspension feeders. Sediment, infauna, mobile epifauna and settling sessile epifauna were sampled. Epibenthic suspension feeders caused an accumulation of fine particles and organic content in the sediment. This was particularly true for mixed treatments indicating interactive effects of both bivalves on sediment characteristics. Mussels caused finer sediment grain-size composition compared to bare sediment. This did not occur among oysters but both bivalves increased organic content. The presence of mussels and oysters increased the abundance of infaunal and epibenthic mobile species differently. The polychaete Lanice conchilega was more abundant on oyster rings and the oligochaete Tubificoides benedeni on mussel rings. Densities of juvenile shore crabs Carcinus maenas and young periwinkles Littorina littorea (< 10 mm shell height) were higher on mussel rings; while abundance of L. littorea ≥ 10 mm shell height was higher on oyster rings. Juveniles of the barnacle Elminius modestus and of mussels showed no preference while oyster spat preferentially settled on conspecifics. We conclude that a shift in dominance from mussels to oysters alters habitat structures which entail differential abundances of associated organisms. This exchange of suspension feeder species is not neutral to community structure because resident mussels and alien oysters function differently as ecosystem engineers.

Geochemical properties of airborne particulate matter (PM 10) collected by automatic device and biomonitors in a Mediterranean urban environment

The mineralogy and geochemistry (major and trace elements) of particulate matter collected from 14 April to 29 May 2003 by automatic device (PM 10) and entrapped by moss and lichen exposed in bags in a monitoring site of Naples urban area were studied with the aim to obtain useful information for risk assessment and control measures feasibility. PM 10 concentrations were generally above the threshold values fixed by the 1999/30/EC directive. Constant and low intensity winds enhanced re-suspension of fine particles and dispersion of gaseous pollutants. PM 10 samples contained trace elements in relatively lower amounts compared to literature reports from other Mediterranean monitoring sites. Significant correlations between Al, Ca, Cu, Fe, K, Mg and Mn indicated that soil dust largely contributed to the accumulation of fine particles on filters and exposed mosses and lichens. Highly significant correlations were also found between Ni and V, indicative of oil combustion processes, Fe, Cu and Cr, indicative of vehicle emissions and mechanical components abrasion, and Na and Mg, indicative of marine aerosols. Lead and Hg did not correlate significantly with any other element. Comparison of element EFs, calculated with respect to the composition of Naples surface soils, indicated higher contribution of soil dust to PM and moss chemical composition compared with lichens, which in turn, according with their better preserved vitality, intercepted/absorbed more efficiently anthropogenic particles and elements of metabolic interest. Crystalline and amorphous detrital components (quartz, calcite, feldspars, volcanic glass, mica, kaolinite and smectite) and sea-bearing salts phases (halite, gypsum, Mg–K sulphates, Mg–Ca carbonates) were the main minerals in PM 10, along with silica fibers and tuff particles.

Morphological, physical and chemical properties of aeolian sandy soils in northern China

The morphological and physico-chemical properties of four pedons representing the major aeolian sandy soils in the arid and semi-arid regions of China were studied for their potential for amelioration and utilization. The aeolian sandy soils of this area show wide variation in their morphological and physico-chemical properties as a result of differences in mean annual precipitation, parent material, vegetation and topography where they are found. The characteristics of and differences among aeolian sandy soils are described in detail. The processes forming these sandy soils are characterized by: (1) fine particle accumulation; (2) crust formation; (3) organic matter accumulation; (4) soil water physical property changes; and (5) total chemical composition changes. The four pedons are classified into four taxonomic groups, based on soil genetic theory. They are Hyperaripsamments, Aripsamments, Semiaripsamments, and Ustpsamments.

Nonlinear effects in particulate processes

The nonlinear effects in various particulate processes are analyzed within the context of population balance modeling. Our main objective is to indicate the origin of the nonlinear effects and to categorize them in a systematic manner. To illustrate the importance of the nonlinear effects, a continuous milling process is considered, which has been analyzed in the literature with linear population balance models only. A continuous stirred tank mill (CSTM) and a plug-flow tube mill (PFTM) of identical volume were numerically simulated. It is well known that the accumulation of fine particles has a slowing-down effect on the breakage kinetics, which leads to non-intuitive results in terms of the produced particle size distribution. A nonlinear population balance theory is presented to account for these effects, and numerical simulations indicate the enormous potential of the new theory.

Changes in soil properties after afforestation in Horqin Sandy Land, North China

We studied the changes in soil properties after afforestation on desertification-affected sandy soils to estimate how much time would be required for soils to recover enough for use in sustainable food production. We surveyed soils near and within 3-, 9-, and 19year- old plantations of poplar (Poplus simonii) in the central part of Naiman County, eastern Inner Mongolia, China. Changes in the soil properties following afforestation included an accumulation of fine particles (clay + silt) and soil organic carbon (SOC) in the surface horizons. The contents of fine particles and SOC increased slowly in the first 9-year period and then rapidly between 10 and 19 years, being higher at concave than convex sites. Soil parameters such as available moisture level, amounts of available N and available P, and CEC that control soil fertility showed a similar trend to that of the contents of fine particles and SOC. The contents of fine particles and SOC were higher at the windward edge than in the center of the 19-year-old poplar plantation, suggesting that the accumulation of fine particles was caused by the decrease in wind velocity due to the presence of vegetation. The increase in the SOC content may be caused by the increased carbon input to soils from the vegetation and by the deposition of fine particles with a higher C concentration than that of native sandy soils. Soil fertility, represented by the amounts of available N in the upper 20 cm layer of the soil, recovered after 19 years under poplars, and was similar to that of adjacent fertile cropland. However, the amount of available N under plantations younger than 10 years was lower than that in cropland soils, suggesting that a period of between 10 and 20 years is required for soils to recover from desertified conditions and be utilized for intensive crop farming once again.

A portable pulsed cavity ring-down transmissometer for measurement of the optical extinction of the atmospheric aerosol.

A small portable system is described which is used to directly determine the optical extinction of the atmospheric aerosol. The requisite highly sensitive measurement of the optical extinction is accomplished simultaneously at two wavelengths in the near-infrared (1064 nm) and visible (532 nm), using the pulsed cavity ring-down (CRD) approach. The measurement at the two wavelengths can aid in separating the scattering and absorption components of the optical extinction. Rayleigh equivalent optical extinction of approximately 10 x 10(-6) m(-1) from particulate matter in the atmospherically important 0.1-2.5 pm diameter size range (fine particle accumulation mode) can be readily observed with short (<5 s) integration times. Optical extinction is inversely related to the visual range, and so the instrument provides a direct measurement of this particulate-related air quality indicator. The instrument can also provide particle size range-selected multiwavelength optical property measurements, which can be inverted to provide valuable information about the extant airborne particulate distribution.

Total hydrolysable amino acid mineralisation in sediments across the northeastern Atlantic continental slope (Goban Spur)

Total hydrolysable amino acids (THAA), individual amino acid distributions, total organic carbon (TOC) and total nitrogen (TN) were measured in sediments across the Goban Spur continental slope at water depths of 651, 1296 and 3650 m. Objectives were to examine (1) differences in organic matter (OM) degradation state in surface sediments across the slope from sedimentary amino acid compositions, and (2) whether these differences are related to particle size distributions. Application of a ‘reaction–diffusion’ model to the sediment concentration profiles showed that TOC and THAA degradation rate constants decreased with increasing water depth. Ratios of degradation rate constants of THAA over TOC indicated that THAA turn over faster than TOC at 651 and 1296 m water depth only. From estimates of degradation rate constants of individual amino acids, it was concluded that with increasing water depth fewer amino acids contribute to overall THAA degradation. The contribution of THAA to TOC mineralisation decreased from the upper to the lower slope. Since at all three sampling stations the amino acids with the highest relative contribution to THAA had a higher abundance in sediments with reduced THAA mineralisation rates, we conclude that the overall amino acid reactivity decreases with increasing water column depth. A principal component analyses, carried out on normalised amino acid mole percentages, established significant shifts in amino acid compositions and confirmed that (1) OM degradation state increased from 651 to 3650 m and (2) that OM in the finest fraction at the shallowest station appeared to be considerably less degraded than in the coarser fractions or any size fractions at the deeper stations. Therefore, we conclude that downslope transport, sorting and accumulation of fine particles with continuous mineralisation of OM attached to the particles during vertical and lateral transport results in an increasing organic matter degradation state from the upper slope to the abyssal plain.

前処理省略型ＲＯ海水淡水化設備

The new reverse osmosis system was developed for the purpose of elimination of pretreatment facility, that is, cost reduction and without coagulant injection. In order to prevent the accumulation of fine particles inside RO module, following two points are improved ; a.) Improvement of RO element construction b.) Development of washing procedure to be effective for discharge of fine particles in RO module.Using raw seawater, the improved modules were tested more than two months. The conductivity of permeate was less than 850, μS/ cm and the differential pressure of RO module could be maintained less than 0.05MPa. So it is considered that application of this type of membrane to a small capacity facility for temporary use or for emergency use is practical.

Deposition of Fine Particles in Packed Beds at Hydrotreating Conditions: Role of Surface Chemistry

Accumulation of fine particles by packed-bed catalytic reactors causes increased pressure drop, sometimes causing premature shut down. Deposition in a reactor, i.e., filtration, is enhanced when the particle suspension is unstable. A model system of 0.68 μm of kaolin in light gas oil was selected to study deposition at hydrotreating conditions. The surface of the kaolin was modified by adsorbing polymeric asphaltene molecules. Particle suspensions were circulated through a packed bed of either glass beads or catalyst in a batch reactor at 375 °C. The filtration mechanism switched from cake filtration to deep-bed filtration when kaolin was pretreated with asphaltene. Deposition of kaolin particles in the bed decreased with increasing asphaltene concentration. These results are consistent with steric stabilization of colloids by adsorbed polymers. Hydrotreating of the liquid phase enhanced desorption of the asphaltene polymer from particle surfaces and increased particle flocculation and deposition along th...

Nematode communities from the North Sea: environmental controls on species diversity and vertical distribution within the sediment

Nematode assemblages were sampled seasonally at three subtidal stations along the Belgian coast. The stations were characterized by muddy sediments (station 115), fine sand (station 702) and fine to coarse sand (station 790). The forces structuring vertical distribution were investigated by evaluating abundance, species composition, diversity and trophic composition, and relating these to sediment composition, redox state and food sources.The nematode assemblages at the two finer grained stations (115, 702) were dominated by Daptonema tenuispiculum and Sabatieria punctata. For both species, the vertical distribution in the sediment seemed not dependent on the redoxchemistry, as former believed for S. punctata, but primarily influenced by food availability. This feature could also be recognized for Ixonema sordidum and Viscosia langrunensis, the most abundant nematodes at the coarse sandy station (790).In general, nematode diversity was regulated primarily by sediment granulometry. Coarser sediments (station 790) yielded more diverse communities compared to the fine sediments (station 115, 702), however seasonal fluctuations and variations with depth into the sediment were not obvious. At the silty stations, when the sediment column was more oxidized in March, overall diversity was higher and showed a positive relationship to the mud content which varied with depth into the sediment. This positive relation is probably explained by an enhanced deposition of organic matter associated with the accumulation of fine particles near the river-mouths. Furthermore, the higher abundance, the lower diversity and the higher dominance found at the two silty stations of the eastern and the western part of the Belgian coast, pointed to a stressed, organically enriched environment.The results demonstrate that controls on nematode community structure are complex and that information at both species and community level are required to properly evaluate the effects of natural and anthropogenic impacts.

Micromorphology of a Mousterian paleosol in aeolianites at the site Habonim, Israel

A paleosol with Mousterian tools in aeolianites at the Habonim site (Carmel Coastal plain, Israel) is a complex pedosedimentary sequence which records a succession of soil-forming episodes and stages of coastal dune instability. We identified three strong soils and one accretionary soil within Mousterian pedocomplex via micromorphological techniques, coupled with FTIR and SEM/EDAX. In the lowermost, red sandy soil (hamra) in Unit IV, decalcification led to the formation of micritic coatings, disrupted by faunal churning, while rubefication resulted in red ferric segregations. Illuviation of ferruginious clay in the form of clay coatings is lacking, probably due to its strong incorporation into the matrix. Redox features were intensified in the pseudogley of the next stage (Unit III). Polyphase calcitic features here indicate that illuviation of clay pre-dates illuviation of micrite and its later recrystallization into sparitic calcite. Further deterioration of drainage conditions and increased accumulation of fine particles led to the formation of vertisol (Unit II). Paleovertisol is characterized by a maximum of clay, stress-originated microfabric, abundant Mn precipitates and calcitic pseudomorphs. The peak of landscape instability occurred later and is recorded in the upper Unit I, in which micromorphological signs of colluvial and aeolian processes are juxtaposed with various ferric accumulations, associated with gleying. The final episode occurred at a time of climatic instability, devegetation, and probably, a simultaneous groundwater rise in the littoral zone.

Analytical Solution for Fine Particle Accumulation in Soil Filters

This paper presents a mathematical solution for fine particle accumulation in soil filters. The solution accounts for particle transport in the base soil and uses a lumped parameter to account for the effects of physicochemical forces influencing particle deposition. It considers particle release without subsequent entrapment in the base soil and particle deposition without subsequent release in the filter, and thus represents an upper-bound solution. The particle capture probability approach is adopted to determine the deposition in the filter. The model is demonstrated using a soil filter typically used in practice to protect fine-grained soils, and the potential for fine particle accumulation in the filter is assessed. The results show that fine particle accumulation in the filter material is significantly influenced by a deposition coefficient which is a function not only of the physical characteristics of the material, such as its particle size and pore size distributions, but also of the pore fluid composition and the size of the migrating particles in the pore stream. Because of its closed-form nature, the solution can be easily adopted in practice to assess the potential of fine particle accumulation in soil filters. A stepwise procedure is suggested to use the solution.

Fine Particle Translocation in Soils Developed on Glacial Deposits, Southern Baffin Island, N.W.T., Canada

Accumulations of fine particles have been observed in coarse-grained, well-drained soils in Arctic areas, and have also been reported in alpine and temperate areas. Both silt caps on cobbles and silt-enriched horizons have been explained as the result of frost sorting. Detailed particle-size analysis of soils from the eastern Canadian Arctic reveals trends which are inconsistent with the frost-sorting hypothesis. In the soil matrix, all particles finer than fine sand show surpluses at some depth. The depth of maximum surplus increases from 15 cm for very fine sand to 55 cm or more for fine clay. The excess clay is offset by deficits higher in the profile, implying redistribution of primary clay. Increases over parent material silt content occur throughout the profiles, implying addition of silt-sized particles to the soil. This surplus of silt is consistent with the addition and infiltration of loess. Both the depths of maximum fine particle accumulation and the amount of accumulated material increase with age, but appear to reach finite limits. Analysis of silt caps reveals surpluses in all size fractions finer than fine sand at all depths. Excess silt is greatest in silt caps in the upper 20 cm, clay increases are greatest between 40 and 60 cm, and silt caps trend toward parent material composition at depths greater than 60 cm. The distribution of sand within the silt caps also differs from parent material. The mechanism suggested for particle translocation is illuviation by rain. The interstitial