Concentration Of Mineral Particles Research Articles

Preferential association of PBDEs and PAHs with mineral particles vs. dissolved organic carbon: Implications for groundwater contamination at e-waste sites

Polybrominated biphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) are commonly detected contaminants at e-waste recycling sites. Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallow surface soils, increasing evidence shows that these compounds can leach into the groundwater. Herein, we compare the leachabilities of PBDEs vs. PAHs from contaminated soils collected at an e-waste recycling site in Tianjin, China. Considerable amounts of BDE-209 (0.3–2 ng/L) and phenanthrene (42–106 ng/L), the most abundant PBDE and PAH at the site, are detected in the effluents of columns packed with contaminated soils, with the specific concentrations varying with hydrodynamic and solution chemistry conditions. Interestingly, the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles, whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent, but showing essentially no correlation with the concentration of mineral particles. The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive, as PBDEs and PAHs often co-exist at e-waste recycling sites (particularly at the sites wherein incineration is being practiced) and share many similarities in terms of physicochemical properties. One possible explanation is that due to its extremely low solubility, BDE-209 predominantly exists in free-phase (i.e., as solid (nano)particles), whereas the more soluble phenanthrene is mainly sorbed to soil organic matter. Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management.

Organic matter in the lacustrine sediments of the Kama-Keltma lowland (Cis-Urals): assessment of distribution and dynamics in the Late Pleistocene and Holocene

The short communication article presents the results of analyses of the lacustrine sediments of Novozhilovo and Chelvinskoe lakes, located at the Kama-Vychegda watershed. Big set (209) of sediments samples from three wells were analyzed by the loss on ignition (550 °C) method. Age of cores and the rate of sediment accumulation were based on the 14 radiocarbon dates. Six stages of deposits accumulation and nature dynamics during the Late Glacial and Holocene in the lakes catchment area are proposed. The first stage (14.15 – 13.5 cal. kyr BP) is characterized by high rates of deposits accumulation at low values of organic matter content, indicating alluvial sedimentogenesis. Peak of accumulation rates as well as a sharp rise in bioaccumulation were observed during the second stage (13.5 – 12.4 cal. kyr BP), which is interpreted as stabilization of the lake level and external environmental conditions. During the third stage (12.4 – 10.7 cal. kyr BP), the sediment accumulation rate decreases rapidly, reaching a minimum by the end of the period. The organic matter content also decreases significantly (to 30 %). The short-term fourth period (10.7 – 10.0 cal. kyr BP) records the transition from the Late Pleistocene (dominance of rarefied periglacial vegetation) to the Early Holocene (predominance of forest communities). This is marked by a drastic increase in the loss on ignition values (up to 92-95%). During the fifth stage (10.0 – 8.8 cal. kyr BP), the sediments accumulation rate increases and the organic matter content decreases to 77-82%. Synchronously with some increase in the concentration of mineral particles. Smoothing of the loss on ignition curve (average values - 92-96%), a marked increase in the sediment accumulation rate during the sixth stage (8.8 - 5.0 cal. kyr BP) probably indicates the stabilisation of external conditions in the lake catchment.

Influence of grease containing mineral particles on friction and wear characteristics between spiral wires inside wire rope

The mine shaft environment is filled with mineral particles and these suspended particles exacerbate the wear behaviour between the wires in wire rope, seriously threatening the safety of mining. In this study, to investigate the influence of mixing mineral (ore, coal) particles of different concentrations and particle sizes in grease on the fretting behaviour between spiral-contacting wires, experiments were carried out on a selfmade test device. The results show that the addition of mineral particles increases the coefficient of friction (COF) and cumulative dissipation energy between steel wires. When the ore particles with a concentration of 15% and a size of 0.048–0.062 mm were added to the grease, the COF between the steel wires reached a maximum of about 0.234. In addition, with the increase of mineral particle concentration and the decrease of particle size, the wear depth, wear amount and specific wear rate of steel wire increase accordingly. Among them, the wear depth, wear amount and specific wear rate reach the maximum after adding ore particles with a concentration of 15% and a size of 0.048–0.062 mm, which are about 30.5 μm, 6706 × 103 μm3, and 2.31 × 10−6 mm3/Nm, respectively. Furthermore, many cutting furrows and crushing pits are added to the wear morphology of steel wire after adding ore particles. The main wear mechanism is severe abrasive wear and fatigue wear. After adding coal particles, the main wear morphology of steel wires is material transfer (attachment of coal particles) and exfoliation, and the main wear mechanism is adhesive wear, fatigue wear and slight abrasive wear.

Influence of different mineral particles in lubricating grease on the fretting behavior between steel wires under different contact forms

The suspended mineral particles in the mine aggravate the wear of hoisting wire rope and seriously threaten the mine safety. In order to explore the effect of different mineral particles on the fretting behavior between steel wires, the wear test of steel wires under different contact forms was performed by a homemade tester. Results show that the coefficient of friction between steel wires decreases with increasing the concentrations of mineral particles (coal particles and ore particles). The wear coefficient of steel wire decreases with the increase of the coal particle concentration, while for the grease mixed with ore particles, the wear coefficient presents the opposite change rule. Compared with the original grease and the grease mixed with coal particles, the wear scars of steel wire under the grease mixed with ore particles condition show more serious furrows, micro cracks and pits. The wear mechanisms of steel wire lubricated by the grease mixed with different mineral particles are abrasive wear, adhesive wear and fatigue wear.

The influences of phytoplankton species, mineral particles and concentrations of dispersed oil on the formation and fate of marine oil-related aggregates

The formation and fallout of oil-related marine snow have been associated with interactions between dispersed oil and small marine particles, like phytoplankton and mineral particles. In these studies, the influences of phytoplankton species, mineral particle concentration, and oil concentration on the aggregation of oil in seawater (SW) were investigated. The experiments were performed in a low-turbidity carousel incubation system, using natural SW at 13 °C. Aggregation was measured by silhouette camera analyses, and oil compound group distribution and depletion by gas chromatography (GC-FID or GC–MS). Aggregates with median sizes larger than 500 μm in diameter were measured in the presence of dispersed oil and the phytoplankton species Thalassiosira rotula, Phaeocystis globosa, Skeletonema pseudocostatum, but not with the microalgae Micromonas pusilla. When mineral particles (diatomaceous earth) were incubated at different concentrations (5–30 mg/L) with dispersed oil and S. pseudocostatum, the largest aggregates were measured at the lower mineral particle concentration (5 mg/L). Since dispersed oil rapidly dilutes in the marine water column, experiments were performed with oil concentrations of from 10 mg/L to 0.01 mg/L in the presence of S. pseudocostatum and diatomaceous earth. Aggregates larger than 500 μm was measured only at the highest oil concentrations (10 mg/L). However, oil attachment to the marine particles were also measured at low oil concentrations (≤1 mg/L). Depletion of oil compound groups (n-alkanes, naphthalenes, PAHs, decalins) were measured at all oil concentrations, both in aggregate and water phases, with biodegradation as the expected main depletion process. These results showed that oil concentration may be important for oil-related marine snow formation, but that even oil droplets at low concentrations may attach to the particles and be transported by prevailing currents.

Comparative analysis of crystallization behavior induced by different mineral fillers in polypropylene nanocomposites

A comparative analysis of crystallization behavior induced by several mineral fillers in polypropylene nanocomposites was performed. Morphological changes and thermal properties of nanocomposites were evaluated, considering the influence of shape, crystalline morphology, and concentration of mineral particles. For this study, hydrated magnesium silicates with different particle morphologies, such as platelets (talc) and fibers (sepiolite), were used for nanocomposites. In addition, to analyze the effect of mineral crystallinity on nanocomposites, talc and sepiolite from different origin and genesis were selected. Nanocomposites were compounded and injection molded, using different filler concentration (0, 1, and 3% w/w) for each mineral particle. To evaluate the particle influence on nanocomposite crystallinity, X-ray diffraction was used to determine crystalline phases and crystal orientation, meanwhile differential scanning calorimetry was performed to obtain thermal properties. Main results revealed that talc has a higher nucleating effect on polypropylene matrix than sepiolite fibers, regardless of their origin and genesis. Meanwhile, a transcrystalline layer that surrounds the fiber surface is observed for nanocomposite containing sepiolite. Moreover, Argentinean talc induces different crystalline phases in nanocomposite with respect to Australian one, which partly influences on mechanical properties.

Contribution of electromagnetic and tomographic technique to the study of the impact of salinity in soils of the experimental station of Al Ain Atti (Errachidia, Morocco)

Soil salinity is widespread particularly in arid areas. Much work has been done to remedy this natural contamination and make them more favorable to receive experimental soil of vegetation adapted to grow in these contrasting environments of scarce water resources. Over the 80 years, Morocco has experienced excessive dryness whose effects have been severely felt in the region of Errachidia. The depletion of the Quaternary alluvial aquifer has required the exploitation of deep reservoirs. In order to optimize the use of salt water in arid, the Institute of Agricultural Research tested soil experimenting three plant species; the Triplex, Acacia and Cypress. This experiment was not only economic objectives; increasing agricultural yields and production, but also reduce the impact of desertification in this region. So these are environmental reasons which have led researchers to realize this experiment whose purpose is to examine the ability of these plants to grow and adapt to irrigation by saline water from the deep aquifer in place. The experimental site is located on the left bank of the national road to Erfoud (Errachidia). In its entirety, the redesigned covering about 10 hectares. The studies that have been conducted mainly concerned pedogenetic analyzes and observations the development height of the plantation tested, regardless of the experimental ground heterogeneity. This is why we undertook a geophysical survey which aims to provide information on the quality of the tested soils and accumulation of salinity at different depths of the experimental ground. To achieve our goal, we used the technique of electrical and electromagnetic investigation in order to identify the main lines of a possible spatial heterogeneity. Recall that the work of OKAY (2010) on an experiment coring by examining the evolution of the newly formed fracturing have proved that the result of resistivity measurement is correlated with that of the chargeability. The electrical resistivity is closely related to the concentration of mineral particles. Characterization studies at the La Ronde tailings mine (Agnico-Eagle Ltd, in Abitibi), showed quite encouraging results (Campos, 2004; Anterrieu, 2006). Since it is a salt-bearing areas (highly conductive) and given that the induced polarization is very sensitive to the ground conductivity; by measurement of residual potential, so we took measures chargeability tomography, the result is compared to the resistivity measured at different soils (control and irrigated), which will better clarify the impact of salinity on the quality of the disturbed soil. Indeed, the chargeability response it possible to characterize the different irrigated soils and its variation is attributed not only to the effect of saline irrigation but also the existence of an heterogeneity of the original ground. Prospecting in electrical tomography has displayed vertically and horizontally anomalies existing within the experimental site of the station of Ain Al Atti, it showed that:- accumulation of salinity becomes wider going from the control ground to that of Acacias.- surveyed the ground at least appear more homogeneous in surface, but their conductivity varies in depth.- salinity origin and the concretion formed on the surface greatly influenced chargeability and resistivity measured on the different experimental soils.

Physicochemical Properties of Individual Airborne Particles in Beijing during Pollution Periods

ABSTRACT Particulate pollution is a serious environmental problem in China and has received much attention from the public. Airborne particles were collected during haze days in Beijing from June 2013 to May 2014. The morphology and elemental composition were investigated with transmission electron microscopy coupled with energy dispersive X-ray spectrometry (TEM-EDX). Six types of individual particles were identified, including sulfate particles (35.1%), mineral particles (26.0%), metal particles (13.5%), fly ash (13.2%), organic particles (5.9%), and soot aggregates (5.7%). Non-carbonaceous particles are mainly “S-rich”, ranging from 37.4% in spring to 56.7% in summer, with certain amount of “Si-rich”, “Ca-rich”, “Fe-rich”, and “K-rich” particles. The relative number percentage of sulfate particles shows a positive correlation with relative humidity (RH), suggesting that high RH might accelerate the sulfation of individual particles. Based on air mass backward trajectories, the high pollution in Beijing might be influenced by local emissions and air masses from adjacent areas south of Beijing. Air masses from Inner Mongolia carry higher concentrations of mineral particles and alleviate the abundance of “S-rich” and other particles.

Changes of the Bacterial Abundance and Communities in Shallow Ice Cores from Dunde and Muztagata Glaciers, Western China.

In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups.

Tensile behavior of polyolefin composites: the effect of matrix parameters

ABSTRACTPolyolefin composites were prepared from 14 PE matrices and three different mineral fillers (montmorillonite, palygorskite and glass microspheres) via melt compounding in an extruder. Mechanical properties of the obtained systems were analyzed with emphasis on elongation at break and conditions for ductile/brittle failure were determined. When filler content is raised beyond a certain “critical” value, tensile properties are dramatically altered and transition occurs from ductile behavior to brittle fracture. This transition is displayed by a well‐defined “step” on the plot of strain at break versus concentration of particles. The value of “critical filler content” was found to depend mainly on level of crystallinity of a matrix while other parameters (chemical nature of filler particles, their size, shape and surface treatment) are less significant. “Critical filler content” will decrease with growth of crystallinity of a polymer and with highly crystalline HDPEs it is as low as 2–8 vol %. Otherwise, with noncrystallizing and low‐crystalline polymers elongation at break decreases gradually with concentration of mineral particles and ductile type deformation is maintained at fairly large filler fractions. The results presented here will be useful for a proper selection of a matrix polymer in composites with mineral fillers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43819.

Determination of the concentration of mineral particles and suspended organic substance based on their spectral absorption

A method to determine the concentrations of the particulate mineral matter (CPMM) and the particulate organic matter (CPOM) is suggested. The values of CPMM and CPOM are calculated from the measurements of the spectral coefficients of the light absorption aPOM(440) and aPMM(750) using empirical equations. The latter have been obtained by comparing the concentrations of the suspended solids measured by means of the gravimetric method with the spectral values of the optical density of the suspended matter settled on membrane filters. The data used are typical of the coastal waters of inland and marginal seas and the open ocean and cover the range of three and two orders of magnitude for the concentrations of CPMM and CPOM, respectively.

Determining Functional Relations in Multivariate Oceanographic Systems: Model II Multiple Linear Regression

Abstract A method for estimating multivariate functional relationships between sets of measured oceanographic, meteorological, and other field data is presented. Model II regression is well known for describing functional relationships between two variables. However, there is little accessible guidance for the researcher wishing to apply model II methods to a multivariate system consisting of three or more variables. This paper describes a straightforward method to extend model II regression to the case of three or more variables. The multiple model II procedure is applied to an analysis of the optical spectral scattering coefficient measured in the coastal ocean. The spectral scattering coefficient is regressed against both suspended mineral particle concentration and suspended organic particle concentration. The regression coefficients from this analysis provide adjusted estimates of the mineral particle scattering cross section and the organic particle scattering cross section. Greater accuracy and efficiency of the coefficients from this analysis, compared to semiempirical coefficients, is demonstrated. Examples of multivariate data are presented that have been analyzed by partitioning the variables into arbitrary bivariate models. However, in a true multivariate system with correlated predictors, such as a coupled biogeochemical cycle, these bivariate analyses yield incorrect coefficient estimates and may result in large unexplained variance. Employing instead a multivariate model II analysis can alleviate these problems and may be a better choice in these situations.

Coupling of Shoreline Erosion and Biodiversity Loss: Examples from the Black Sea

The shoreline zone is an area where the sea and land contact and plays a very important role in integrating a sea and its watershed in a whole system. Among the main environmental problems of the coastal zones, two critical ones are - coastal erosion and a biodiversity loss. Problems are most pronounced in semi-enclosed seas as the Black sea. Using results of the long-term studies in different parts of the Black Sea shoreline this paper attempts to make some steps to deepen our understanding of interactions between biodiversity loss and shoreline erosion. An analysis of the results from several case studies was done. Some mechanisms of interrelations between coastal erosion and biodiversity changes are also discussed. The increased concentration of mineral particles, especially hydrophilic ones, as a result of coastal erosion, is a threat not only to benthic organisms, but also to planktonic microalgae and copepods. This negative impact sharply decreases total productivity of coastal waters. De-vegetation of the beaches and cliffs increases movement of sand and soil particles from beaches and cliffs due to high acceleration of wind and water erosion. This also leads to an increased turbidity of marine waters and an associated decrease in their productivity. Other results suggest there is a decrease in mollusk shell production leading to acceleration of a beach degradation which may also increase cliff abrasion. Coastal de-vegetation, marine community degradation and coastline erosion interrelate through a network of chains of cause-and-effect that forms the positive feed-forward and feed-back loops. This creates a self-acceleration mechanism of a development of coastal erosion and biodiversity loss.

Biogeochemical implications of increased mineral particle concentrations in surface waters of the northwestern North Pacific during an Asian dust event

[1] Simultaneous observations were made in the marine atmospheric boundary layer and surface ocean during spring 2007 to investigate potential impacts of Asian dust on a semi-pelagic region of the northwestern North Pacific. The results suggest that mineral dust aerosols were scavenged by sea fog, and their deposition to the ocean increased the particle concentration in surface seawater. The atmospheric input of mineral dust to the ocean surface from this event was calculated to be 40 to 680 mg m−2 event−1. A general relationship for the solubility of iron from dust particles led to an estimate of 20 to 330 μg m−2 for the amount of bio-available iron delivered during the dust event. This input of bio-available iron is comparable to total dissolved iron added during an iron fertilization experiment in the northwestern North Pacific in which an enhancement of primary production was observed.

Light scattering by particles suspended in the sea: The role of particle size and density

Optical scattering and particle size measurements are reported at 78 stations along the south and west coast of Britain. The composition of the particles is mainly mineral (70% by mass on average) and the light scattering per unit concentration of suspended particles, the specific scattering coefficient, was observed to vary by over an order of magnitude, from less than 0.1 to over 1 m 2 g −1. More than 3 4 of this variance is explained by changes in the apparent density (dry weight/‘wet’ volume) and mean size of the particles. For this data set, the specific scattering coefficient can be written b* M =(2.35/ ρD A ) where b* M is the scattering coefficient per unit concentration of mineral particles, ρ the apparent density and D A the mean particle diameter by area. The standard error of the numerator in this equation is 0.08. In fact, most (64%) of the variance in b* M is explained by differences in the apparent density of the particles, with variations in particle diameter alone accounting for only 15% of the variance. Because particles in coastal waters flocculate into aggregates containing mineral and organic material as well as water, the apparent density of the particles is variable and considerably less than solid mineral material. Provided a suitable atmospheric correction for visible-band imagery over shelf seas can be applied, it may be possible to estimate b* using satellite remote-sensing measurements of reflectance at two wavelengths. This work has shown that maps of b* produced in this way will be sensitive to variations in near-surface particle density as well as size. It may, however, be possible to use site-specific empirical relationships between particle size and density to derive both of these parameters from space.

Watershed discharge modulates relationships between landscape components and nutrient ratios in stream seston

In order to understand the environmental controls of the elemental composition of suspended particles in streams and rivers, we examined relationships between the stoichiometry of suspended particles and catchment characteristics (e.g., topography and land cover) under contrasting hydrological conditions in streams from the Upper Peninsula of Michigan, USA. Particulate C:N, N:P, and C:P ratios varied considerably among streams on each of 10 separate sampling dates and within most streams through time. When averaged across the study period by stream, particulate C:N:P ratios were strongly related to several catchment properties. For example, particulate C:P and N:P ratios were negatively related to the percentage of catchment used for agriculture but positively related to the percentage of catchment found as wetlands. These relationships reflected, in part, variable concentrations of mineral particles, which were strongly related to stream length, agriculture, and upstream lake area. In addition, the strength of the relationships between particulate elemental composition and catchment properties changed depending upon hydrologic condition of the Ontonagon watershed. For example, periods of wetness, as indicated by high river discharge, were found to increase the strength of seston C:N ratio-percentage of wetlands relationships but to reduce the strength of seston C:P ratios-percentage of wetlands relationships. Our results thus demonstrate that the balance of elements fluxing through forested streams is strongly affected by catchment properties but that these effects are sensitive to watershed discharge. At times of high discharge, there are strong connections to catchment sources while in-stream processes appear to predominate at time of low discharge.

Effects of upstream hydropower operation and oligotrophication on the light regime of a turbid peri-alpine lake

Anthropogenic activities in catchments can alter the light regimes in downstream natural waters, affecting light attenuation and the perceived optical properties of the waters. We analyzed the effects of upstream hydropower operation and oligotrophication on light attenuation and reflectance in Lake Brienz (Switzerland). For this purpose, we reconstructed its light regime for the pre-dam condition and for periods of 4-fold increased primary productivity, based on direct observations of light and beam attenuation as well as concentrations of optically active compounds, especially observed and simulated mineral particle concentrations. Based on our assessment, light attenuation before the construction of upstream dams was double the current value during summer and nearly half in winter. This result is consistent with pre-dam measurements of Secchi depths in the early 1920s. Using a simple optical model, a significant increase in reflectance since the 1970s was estimated, assuming a 4-fold decrease of optical active organic compounds within the lake. As reflectance is perceived by human eyes as turbidity, this may explain subjective reports by local residents of increasing turbidity in recent years.

Retrieval of chlorophyll fluorescence from reflectance spectra through polarization discrimination: modeling and experiments

The polarization discrimination technique we recently developed, shows that it is possible to separate the elastic scattering and the chlorophyll fluorescence signal from the water-leaving radiance by making use of the fact that the elastically scattered components are partially polarized, while the fluorescence signal is unpolarized. The technique has been shown to be applicable to a wide range of water conditions. We present an extension of experimental and analytical results, which serve to define the scope of this technique and its range of applicability. A new analysis, based on vector radiative transfer computations, and on laboratory and field measurements on eastern Long Island and in the Chesapeake Bay, shows that the technique is generally effective for both open ocean and coastal waters, but that it is limited if the ocean bottom albedo and/or multiple scattering due to very high mineral particle concentrations result in depolarizing the water-leaving radiance. In addition, we show that in contrast with the polarization-based retrieval, the traditional method of extracting fluorescence height using the baseline method can give significant errors, particularly for coastal waters where it strongly overestimates the fluorescence values.

Suspended minerogenic particle distributions in high‐energy coastal environments: Optical implications

This paper examines suspended minerogenic particle distributions in the near‐coastal ocean, Oceanside, California. The environment is dominated by resuspension of particles from a well‐sorted sandy sediment. We obtain information on the suspended mineral matter from the relocatable numerical sedimentation model, TRANS98. Inputs for the model include bottom particle size distribution, wind speed, wave period and height, and near‐bottom current speed. Model output is a vertical profile of mineral particle concentrations and size distributions at selected depths. The mineral particle size distribution allows the calculation of the total scattering coefficient of suspended minerogenic matter. The particle size distribution for the bed at Oceanside is approximately Gaussian lognormal in character. The predicted size distribution near bottom is a skewed Gaussian lognormal; then the distribution shifts toward the increasing importance of smaller size classes as we approach the water surface. Deeper stations maintain a lognormal character up into the surface layers while the shallower stations switch to a particle size distribution of the smallest size class being the modal class in the surface layers. Hyperbolic size distributions have been proposed for the Oceanside site from optical observations. These distributions would have a slope of 2.1 for coastal water which would decrease to as low as 1.3 for shallow nearshore stations and near the bottom. None of the proposed hyperbolic slopes provides an adequate approximation of the particle distributions predicted by TRANS98. The larger particle size classes are significantly overestimated by hyperbolic models, which causes the total scattering coefficient of the minerogenic matter to be overestimated. These results indicate that hyperbolic slope models cannot be used to retrieve particle size distributions by inversions involving the total scattering coefficient nor are they accurate estimators of the minerogenic scattering coefficient.

Mineral Particles in Cloud Droplets Produced in an Artificial Cloud Experimental System (ACES)

An instrument that collects cloud droplets one by one was designed to measure the fraction of cloud droplets containing mineral particles. Sampling was performed in the artificial cloud experimental system (ACES) established in the vertical shaft of an abandoned mine. The collected droplets were observed with a scanning electron microscope (SEM), and their constituents were analyzed by an energy dispersive X-ray analyzer (EDX). The ratio of droplets including mineral particles was above 50%, reflecting the high concentration of mineral particles at the bottom of the shaft. When small droplets were sprayed by an industrial fog generator at the bottom of the shaft, the fraction of cloud droplets with mineral particles decreased but remained above 20%. This result suggests that mineral particles in the free atmosphere may also act as cloud condensation nuclei and be incorporated into cloud droplets at the early stage of cloud formation. Significant influences on the climate model, biogeochemistry, and atmosp...