Suspended Particulate Matter Size Research Articles

SEASONAL VARIATION AND THEIR CHARACTERIZATION OF SUSPENDED PARTICULATE MATTER IN THE AIR OF SUBWAY STATIONS

In order to accumulate fundamental data on the atmospheric environments in subway, the mass concentration, particle size distribution and elemental constitution of suspended particulate matter (SPM), and the concentration and constitution of polycyclic aromatic hydrocarbon (PAH), were measured and analyzed at three subway stations with different air supply systems on the same line. The mass concentration of SPM in the subway stations showed seasonal variations, and was higher in December and October than in March and June. It was also higher at the subway stations than in the aboveground throughout the seasons. The concentrations of SPM in the size range of 0.5–5.0 μm were higher in the subway stations than aboveground, suggesting this size of SPM was generated by the operation of trains. The elements that were observed at high concentrations in the subway SPM were Fe, Ba, Cu and Ca. On the other hand, the elements of which concentrations were relatively higher in the aboveground air were Cl, Na and K. Polycylic aromatic hydrocarbons collected at the subway stations showed similar concentrations and characteristics to those observed in the urban atmosphere.

Quantification of errors in transmissometer-derived concentration of suspended particulate matter in the coastal zone: implications for flux determinations

Optical beam transmissometers were tested at two shallow water sites off the English coast of the southern North Sea. Concentration and particle size of suspended particulate matter (SPM) or suspended sediment were measured over tidal cycles using transmissometers and laser sizer. SPM concentrations and horizontal fluxes, derived from calibrated transmissometer data, were compared with measured concentrations and fluxes, determined gravimetrically from filtered samples.SPM displayed a bimodal particle size spectrum with primary modes at 20 and 125–250 μm. The first site, in the Wash embayment, was dominated by tidal resuspension with semi-diurnal addition of a coarse resuspension mode to a fine background mode. The second site, adjacent to the mouth of the Humber estuary, was dominated by tidal advection of the turbid Humber plume so that SPM concentration and quality varied diurnally as a strong lateral concentration gradient (from turbid, plume water to clear, plankton-rich shelf water) advected along the coast.Short-term variability of particle size and type diminished the correlation between optical beam attenuation and SPM concentration. Transmissometer calibration was improved by adopting a two-part correlation. At the resuspension site, the two parts were separated by onset and cessation of resuspension, one part corresponding to SPM in long-term suspension, the other to resuspended SPM. At the turbid plume site, the two parts were separated by advection of the salinity front so that one part characterised lower salinity, turbid plume water, the second part higher salinity, clear shelf water.Calculated flood and ebb SPM fluxes were inaccurate (up to 23% error) using conventional transmissometer calibration, but error reduced to an average 3% using two-part calibrations. There were large errors (up to 51%) in net tidal SPM flux estimates, but these reduced to an average 16% using two-part calibrations.

Geochemistry of Suspended Particulate Matter (SPM) in the Murray-Darling River System: A Conceptual Isotopic/Geochemical Model for the Fractionation of Major, Trace and Rare Earth Elements

A conceptual isotopic/geochemical model is presented to explain the variation of major, trace and rare earth element (REE) geochemistry and Sr isotope systematics in suspended particulate matter (SPM) as a function of particle/colloid size. This conceptual model is an extension of a previous investigation of the origin of SPM in the Murray-Darling River system (MDRS) that utilised Sr isotope systematics to examine aspects of SPM (particle/colloid) origin, structure and mineralogy. The geochemical processes that give rise to the often coherent trends in major, trace and REE geochemistry and Sr isotopic signature as a function of particulate ( 1 μm) size in the MDRS have been identified using an enhanced SPM size fractionation technique as a basis to not only obtain a broad range of particle/colloid size ranges, but also to provide sufficient material for subsequent geochemical and isotopic analysis. The conceptual isotopic/geochemical model proposed here contains three major components: (i) the differential weathering of micas and alkali (K-) feldspars to form the majority of the particulate ( 1 μm) fractions (low 87Sr/86Sr ratio), with a range of geochemical signatures related to the relative proportions of inorganic and organic constituents, and (iii) the presence of natural organic matter as coatings on the particulate ( 1 μm) matter and possibly as organo-colloids which exert an increasing influence in particular on bulk colloid geochemistry with decreasing colloid size. This conceptual isotopic/geochemical model also accounts for the distinct variation in major, trace and REE geochemistry and Sr isotopic systematics between the particulate ( 1 μm) fractions, the variation being primarily a function of the distinctly different precursor mineralogies of the SPM fractions and geochemical fractionation during the weathering and transport. Additionally, this model explains a systematic fractionation of REE apparent within colloidal (>1 μm) fractions. Statisitcal (hierachical cluster) analysis of two particulate and three colloidal fractions from 23 samples from the MDRS is used as a basis to investigate geochemical and mineralogical associations within the particulate and colloidal size fractions and to provide additional supporting evidence for the conceptual isotopic/geochemical model.

Aggregation and resuspension of suspended particulate matter at a seasonally stratified site in the southern North Sea: physical and biological controls

The physical and biological characteristics of suspended particulate matter (SPM) have been investigated at a site in the southern North Sea characterised by a seasonally stratified water column and a muddy sand bed. Significant variability in SPM concentration, composition, size and settling velocity was observed over tidal, spring/neap and seasonal time scales. Tidal currents alone are not sufficient to resuspend the bulk of the sea-bed sediment. However, sea-bed erosion does occur when wind/wave action enhances the bed shear stress during winter storms. Also, during winter and summer aggregated organic-rich material with a modal settling velocity of 0.2 mm s -1, originating from the sediment/water interface or from pelagic organic detritus, is subject to spring-tide or wind/wave resuspension. Phytoplankton production in the surface mixed layer (SML) is nutrient limited during much of the summer, but there can be sufficient light penetration to allow production at or below the thermocline. So production in the bottom mixed layer (BML) can be either light or nutrient limited, and BML nutrient levels do not gradually recover during the summer. Aggregation of phytoplankton is an important process at this site, resulting in significant modification of settling behaviour and hence dynamics of SPM. Settling velocity and particle size measurements indicate that both diatom and dinoflagellate blooms form large aggregates towards the end of their growth phase, with modal settling velocities between 2 and 5 mm s -1. Nitszchia pseudoseriata aggregates were relatively stable, remaining as viable sites for primary production over several cycles of tidal resuspension and deposition. Moreover, they efficiently ‘scavenged’ fine inorganic particles from the water column as they settled out. Tidal resuspension of these aggregates results in much higher water-column residence times than would be calculated simply from settling rate and water depth. This allows a greater proportion of remineralisation to be performed in the water column, rather than within the sea bed.

The size of suspended particulate matter in air.

By means of the NASN cascade impactor the particle sizes of ambient aerosols can be measured by fractionating the particles according to their aerodynamic dimensions, and the fractions can be quantified gravimetrically. Data obtained with this instrument show that particulate matter suspended in urban air in the United States and Great Britain is remarkably uniform in distribution and that the particles are predominantly less than 1 microm in diameter. In Ankara, Turkey, the high proportion of particles larger than 1 microm in diameter are associated with the incomplete combustion of lignite; particulate concentrations in Ankara, however, are considerably higher than those measured elsewhere. The growth of particles in air during temperature inversions occurs in Cincinnati; the greater proportion of large particles found there during inversion periods can account for the reduction in visibility. Aerosols in the vicinity of highways are composed of particles larger than those found some distance away because of the reentrainment of debris by the traffic-induced turbulence. On the other hand, highway configuration and traffic volume have little effect on the size distribution of aerosols in samples collected away from the turbulence area of the roadway. Aerosols measured inside buildings are predominantly smaller in size and exhibit a narrower range of sizes than aerosols outside buildings.