Wind Resuspension Research Articles

Application of Resuspension Data of Respirable Particles for Early Phase Inhalation Following Deposition Contamination in Radiological Emergencies.

Abstract In model experiments, wind resuspension rates, Rr, of respirable particles (<10 μm, aerodynamic diameter) and their time dependence after deposition on representatively contaminated urban surfaces were measured under real-life conditions, taking into account different weather conditions (wind velocities, precipitation) as well as countermeasures (fixation). For contamination by dry deposition of particles, short-term resuspension rates averaged over the first half hour, after exposure to wind with a friction velocity, u*, of 0.8 m s−1 ranged between 0.1% h−1 and 2% h−1 depending on the surface material, whereas after wet deposition, resuspension rates were two orders of magnitude lower. The time pattern of the resuspension rates followed a power law decrease, Rr ∝ t −μ , with values of μ close to 1. The measurements revealed a strong dependence on friction velocity, . For a larger area of 200 × 800 m2 contaminated with 106 Bq m−2 of particles in the respirable size range, applying a simple Gaussian dispersion model airborne activity concentration (Bq m−3) was calculated. On this basis, for an initial time of high windspeed, a cautious resuspension factor of Rf = 5 10−6 m−1 is derived for the first day, which diminishes inversely with time. The exposure of persons to external radiation and to inhaled airborne radioactivity is compared with examples for three radionuclides representing strong beta-, gamma- and alpha-radiation.

Estimation of Cs-137 emissions during wildfires and dust storm in Chernobyl Exclusion Zone in April 2020 using ensemble iterative source inversion method

The emission inventories of cesium-137 resulting from the wildfires in the Chernobyl Exclusion Zone (3–24 April 2020) and from the dust storm (16–17 April 2020), which resuspended contaminated ash, were estimated using inverse modeling. The goal of this work was to take into account uncertainties of inexactly known source term and meteorological input data for evaluation of emission inventories and their confidence limits, by developing Ensemble Iterative Source Inversion Method (EISIM). A set of source receptor matrices (SRMs) was calculated using FLEXPART atmospheric transport code with varying source term parameters (size distribution of emitted particles, height distribution of emissions) and meteorological input data. The covariance matrix of model errors was estimated by ensemble averaging of model results obtained after multiplication of the pre-calculated SRMs by the estimated emission inventories at the current iteration step. The emission inventories at each iteration step were evaluated for each of the ensemble members by solving the conventional variational source inversion problem. With iterations, the variance of model error was reduced by an order of magnitude. The estimated total emission of 137Cs from wildfires was 448 GBq, close to the first guess estimation. By using emission inventories within the obtained confidence limits (from 39 to 1530 GBq), different combinations of source term parameters and input meteorological data, FLEXPART could fit observations with a correlation coefficient of more than 0.6 and a normalized mean squared error of less than 10. The obtained estimate of the total emission resulting from the wind resuspension during the dust storm was 27 GBq. The respective estimated confidence interval was from 3 to 93 GBq. By analyzing model error statistics, some of the source term parameters could be reliably evaluated. The fraction of the fine particles (0.25 μm) in total emissions Wsf(0.25)≈0.1 and the fraction of emission below a bottom height of convective plume Wh(1)≈0.5.

SOIL AND ATMOSPHERIC AEROSOL CONTAMINATION AT THE TERRITORIES OF INFLUENCE OF FORMER URANIUM PRODUCTION FACILITIES “PRIDNIPROVSKY CHEMICAL PLANT”

Problems Statement and Purpose. The territory of the former Uranium production facility “Prydniprovsky Chemical Plant” (“PChP”) are located in Kamensky city, Dnipropetrovsk region, occupy the area of the upper and lower terraces of the Dnieper River (more than 300 hectares), where the remained legacy facilities and residues of the former uranium ore processing are located. After 1991 the production of Uranium concentrates ceased without remediated. Thus, up to 40 million tons of radioactive and chemical mineral residues of uranium production have accumulated within its industrial site and at the adjacent territories. Systemic monitoring studies began only in 2005. The studied environment characteristics were soils contamination, the tailings facilities where Uranium ore processing residues had accumulated, as well as atmospheric contamination by airborne aerosols. The purpose of this study stage is a comprehensive analysis of the spatial distribution of radionuclides of Uranium series at the legacy site territory and factors that can lead to a significant expansion of the contaminated area and scale of chronic environmental pollution under the influence of atmospheric transport and human exposure by inhalation. Data & Methods. The field sampling and analytical methods (gamma, alpha spectrometry and liquid scintillation counting methods) for determination of radionuclides of U-Th decay series were in use for this study. Soils samples from the top layers (0–5 cm) and gamma-dose rate surveys performed. A two-week continues integrated sampling data on the radioactive aerosols ambient activity concentrations and radioactive atmospheric fallout from 7-th locations at the legacy site and adjacent areas used for the environment radioactivity site-specific analyses. For determination of radionuclides in the environment samples (aerosols, soils and in the raw ore mineral residues) the low background gamma-spectrometry method with HPGe detectors have been in use. The content of metals associated with aerosols measured on filters using atomic absorption spectrometry methods. The data analysis for longterm series of observations (2005–2017) carried out using statistical methods. The compliance environment contamination analyses for the legacy site were carried comparing averaged observed data with the established safety criteria and regional background observation data. Results. The main current sources of radiation emission to the environment at the legacy site are open dispersed residues of Uranium production accumulated at the tailings facilities and at the former U‑extraction infrastructure. The spatial analyses of the gamma dose rate at the U‑production legacy site and its soil chemical contamination showed that about 30% of its territory requires decontamination. It is shown that the effects of aerosol radioactive particles dispersion from the contaminated “hot spots” at the territory such as tailings and former U‑production infrastructure are local and do not extend significantly beyond the industrial site. The greatest effects of wind re-suspension and propagation observed during the period of earthworks during construction of the U‑tailings covers and residues management at the contaminated facilities. In worst cases during earthwork at the U‑tailings facilities specific activity concentrations of 238U, 226Ra associated with aerosols (dust) nearby the tailings facilities may exceed 100 times above background radioactivity concentrations level observed at the distance about 10 km from the legacy site in the Kamyanske city. However, the air contamination with radioactive dusts in the worst meteorological conditions (dry windy period observation) did not exceed safe level of air concentrations according national radiation safety standards of Ukraine. The content of metals associated with aerosol particles can also increase by 2–10 times, but also their transfer by wind at the site is local and does not have a significant impact on residential areas of the city. Significant inhalation risks may arise during the dismantling of production equipment and buildings of former uranium production. Therefore, during implementation of any engineering remediation works, it is advisable to provide dust suppression control and to remove all dispersed materials from the former Uranium extraction before dismantling of the contaminated buildings and U‑production equipment. The introduced methods of air sampling at the PChP legacy site and low background analytical methods for radionuclide determination in the laboratories allow to recommend them for site specific environment monitoring programs bringing the radioactive contamination PChP site in a safe state

До питання про основні напрямки повітряної міграції 137Cs у зоні відчуження

Retrospective studies of the contribution of emissions from the Shelter object to the formation of the radioaerosol situation in the Exclusion Zone before the construction of the New Safe Confinement were conducted. An algorithm for estimating the average volumetric activity of 137Cs in the air depending on the wind direction is proposed based on data on the activity of air filters exposed in the monitoring posts of the ASKRO system. It was established that the predominant contributions to the arrival of radioactive aerosols in each of the six selected settlements in the Exclusion Zone in previous years were made by the winds of the northern group. It was found that the reliable periods of high activity transport did not always coincide with the wind direction from the Chornobyl nuclear power plant. From the absence of reliable correlations between wind speeds and the values of the 137Cs volumetric activity in the air, the same as from the presence of developed vegetation during periods of maximum activity, it was concluded that the wind resuspension processes have an insignificant contribution to the formation of the radioaerosol situation in the territory of the Exclusion Zone. It is assumed that forest fires make the most significant contribution to radioactive air pollution in this area

Eutrophication management in a Great Lakes wetland: examination of the existence of alternative ecological states

AbstractThe degradation and loss of ecologically important wetlands has been a topical issue in the Great Lakes region, where 60–80% of the coastal wetlands have been lost since the 1800s. The present modeling study aims to guide the restoration efforts in Cootes Paradise marsh, one of the most degraded shallow wetlands in Southern Ontario. We use a process‐based eutrophication model designed to reproduce the biotic competition among multiple phytoplankton and macrophyte functional groups. Our primary focus is to offer guidelines for wetland restoration by characterizing the ecophysiological processes of the autotrophic assemblage, such as the nutrient uptake from the water column and/or the sediment pore waters, the relative ability to harvest light and fuel photosynthesis, and temperature control of the algal/macrophyte growth and basal metabolism. We predict that the additional reduction of external phosphorus loading in Cootes Paradise could induce an abrupt, non‐linear shift from the current turbid phytoplankton‐dominated state to a desirable clear macrophyte‐dominated state. The emergence of this critical (or tipping) point, where the shift to another ecological state may occur, can be accelerated by the presence of a thriving macrophyte community with an enhanced ability to sequester phosphorus. However, it may also be delayed by the presence of a suite of biogeochemical mechanisms (often referred to as “feedback loops”), such as the remobilization of legacy P due to sediment diagenetic processes, wind resuspension, bioturbation, hydraulic loading from local tributaries, water‐level fluctuations, and the leachable P pool of dead plant material that can be returned into the water column through senescence. Our study identifies the restoration actions required to minimize the likelihood of prolonged hysteresis and to facilitate a shift to a desirable ecological state in the foreseeable future. The areal expansion of aquatic vegetation will not only lead to the establishment of a thriving meadow and emergent vegetation community, but may also pave the way for submerged macrophytes through a suite of synergistic mechanisms. Additional point‐source loading reductions will facilitate the transition to an alternative stable clear macrophyte‐dominated state, but could also consolidate the future resilience of the marsh.

Spatial and temporal dynamics of the mesozooplankton (Crustacea: Cladocera, Copepoda and Decapoda) in a Pampean shallow hyposaline lake during drought conditions

The Sauce Grande Lake, a shallow, eutrophic, and hyposaline lake, was studied through monthly samplings during a year (December 2009- November 2010). The drought that affected the region since 2009 and during the entire study period interrupted the regular inflow from the river and outflow to the Atlantic Ocean. The lake presented an increase of salinity values and highly turbid conditions as a result of the drought conditions and wind resuspension. Small cladocerans such as Moina micrura and the copepod Boeckella poopoensis dominated the mesozooplankton community. The salinity determined the mesozooplankton composition; meanwhile, the abundance dynamic was ruled by temperature in conjunction with the eutrophic conditions during the study period. In a global context of climate change, and in a region where drought and wet cycles are frequent, these results further contribute to understanding the processes affecting the zooplankton community structure and dynamics during extreme climate events.

Predicting the likelihood of a desirable ecological regime shift: A case study in Cootes Paradise marsh, Lake Ontario, Ontario, Canada

Abstract Environmental modelling is one of the pillars of the management process, representing an “information integrator” that brings together scientists, managers, and other stakeholders in a joint assessment of our understanding of the system being managed and the compelling knowledge gaps we seek to answer through monitoring and research. The overarching goal of the present modelling study is to offer insights into the restoration and management of Cootes Paradise marsh, one of the most degraded shallow wetlands in Southern Ontario. We use a mechanistic model to leverage our understanding of the major phosphorus biogeochemical pathways in Cootes Paradise. We also develop a network of statistical models that accommodates the spatial heterogeneity of the prevailing water quality conditions in the marsh. Combining the insights from both models, we found that a drastic reduction of point- and nonpoint-source nutrient loading could trigger a non-linear shift from the current turbid-phytoplankton dominated state to a clear-macrophyte dominated state. The restoration trajectory of the system can be profoundly modulated by the presence of a thriving macrophyte community with an enhanced ability to sequester phosphorus (i.e., the net amount of phosphorus taken up per unit of plant tissue). Critical remedial actions to re-establish the targeted macrophyte species in their native marsh habitats include both the intensification of local planting efforts and the control of invasive plant species. Another important finding of our modelling analysis is that the signature of the water quality improvements brought about by nutrient loading reductions dissipates as we move from the marsh’s western end to the central area due the presence of confounding factors, such as the hydraulic loading from Spencer Creek, internal nutrient loading, wind resuspension, and bioturbation. Given the high uncertainties associated with forecasting drastic (and costly) remedial actions, we argue in favour of a socioeconomic assessment of Cootes Paradise marsh as an ecosystem service provider to determine the benefits in terms of monetary values when we examine different courses of management options.

Донные отложения как индикатор первичного и источник вторичного загрязнения речных вод углепромышленных территорий Восточного Донбасса

For the first time for East Donbass coal-mining areas the material structure and impurity levels of small and average rivers’ bottom sediments were studied. Data of a wide range of heavy metals and minerals in bottom sediments and in the pelitic fraction (<0.01 mm), which is the most informative at assessment of river alluvium impurity degree, are obtained. As the made model experiment result data on region bottom sediments as aquatic environment secondary pollution source are obtained. It is defined that under certain hydrodynamic conditions such as wind resuspension, water discharge change, dredging etc. region river sediments can be a secondary water pollution source with compounds of manganese, iron, copper, chrome and lithium. The rivers were ranked according to the secondary pollution danger’s degree and negative impact on water quality based on the scoring method. The obtained data showed that the major part of the region rivers are characterized by medium and low levels of potential impact on the rivers aquatic environment.

Phosphorus dynamics in the water of tropical semiarid reservoirs in a prolonged drought period

Abstract Aim To verify the vertical distribution of phosphorus in the water and to identify the predominant forms of P in the water column for understand the phosphorus dynamics in tropical semiarid reservoirs during a prolonged drought period. Methods Two reservoirs from the semiarid region of Rio Grande do Norte were analysed during the period from May 2015 to June 2016. Were analysed: Suspended solids (SS), chlorophyll a (Chl-a), dissolved oxygen (OD) and temperature. Vertical profiles were plotted for total phosphorus (PT), total dissolved phosphorus (PTD), particulate phosphorus (PP), dissolved organic phosphorus (POD) and soluble reactive phosphorus (FRS). Results The phosphorus values distributed in the water column were high for both reservoirs, presenting the highest values during the periods with lower depth. Gargalheiras presented greater predominance of PT and PP, while Cruzeta had the highest values of FRS. Chl-a and SS values were also consistent with phosphorus values: Chl-a was higher in Gargalheiras, while SS, mainly inorganic, were higher in Cruzeta. Gargalheiras presented anoxic conditions close to the sediment from May 2015 to December 2015, which may induce the release of phosphorus from the sediment to the water column. Values that are too high during the shallower months, especially in Cruzeta, may have been influenced by the release of P from sediment through wind resuspension. Conclusions The amounts and predominant types of phosphorus in the water column are of great importance to understand the phosphorus dynamics and will support restoration plans for the studied environments. In this study it was possible to verify that the reservoirs are susceptible to the release of P from the sediment due to the environmental conditions, mainly low depths, resuspension of the wind and anoxia in the hypolimnion.

Source apportionment and environmental fate of lead chromates in atmospheric dust in arid environments

The environmental fate of lead derived from traffic paint has been poorly studied in developing countries, mainly in arid zones. For this purpose, a developing city located in the Sonoran desert (Hermosillo, Mexico), was chosen to conduct a study. In this paper the lead chromate (crocoite) sources in atmospheric dust were addressed using a combination of Raman microspectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and Pb isotope measurements. A high concentration of Pb and Cr as micro- and nanostructured pigments of crocoite is reported in yellow traffic paint (n=80), road dust (n=146), settled dust in roofs (n=21), and atmospheric dust (n=20) from a developing city located in the Sonoran Desert. 10 samples of peri-urban soils were collected for local geochemical background. The paint photodegradation and erosion of the asphaltic cover are enhanced by the climate, and the presence of the mineral crocoite (PbCrO4) in road dust with an aerodynamic diameter ranging from 100nm to 2μm suggests its integration into the atmosphere by wind resuspension processes. A positive PbCr correlation (R2=0.977) was found for all studied samples, suggesting a common source. The Pb-isotope data show signatures in atmospheric dust as a product of the mixing of two end members: i) local soils and ii) crocoite crystals as pigments in paint. The presence of lead chromates in atmospheric dust has not been previously documented in Latin America, and it represents an unknown health risk to the exposed population because the identified size of crystals can reach the deepest part of lungs.

Environmental releases from fuel cycle facility: part 1: radionuclide resuspension vs. stack releases on ambient airborne uranium and thorium levels

Airborne activity levels of uranium and thorium series were measured in the vicinity (1.1 km) of a uranium (UF4) processing plant, located in Malvési, south of France. Regarding its impact on the environment, this facility is characterized by its routine atmospheric releases of uranium and by the emission of radionuclide-labelled particles from a storage pond filled with waste water or that contain dried sludge characterized by traces of plutonium and thorium (230Th). This study was performed during a whole year (November 2009–November 2010) and based on weekly aerosol sampling. Thanks to ICP-MS results, it was possible to perform investigations of uranium and thorium decay product concentration in the air. The number of aerosol filters sampled (50) was sufficient to establish a relationship between airborne radionuclide variations and the wind conditions. As expected, the more the time spent in the plume, the higher the ambient levels. The respective contributions of atmospheric releases and resuspension from local soil and waste ponds on ambient dust load and uranium-bearing aerosols were estimated. Two shutdown periods dedicated to facility servicing made it possible to estimate the resuspension contribution and to specify its origin (local or regional) according to the wind direction and remote background concentration. Airborne uranium mainly comes from the emission stack and, to a minor extent (∼20%), from wind resuspension of soil particles from the surrounding fields and areas devoted to waste storage. Moreover, weighed activity levels were clearly higher during operational periods than for shutdown periods.

Experimental Modeling of Wind-Driven Bin-by-Bin Resuspension Factors of Freshly Fallen Radionuclides After an Energetic Release From a Radiological Dispersal Device

Small-scale experiments were carried out to characterize the resuspension factor of radioactive lanthanum oxide powder in an environmentally controlled wind tunnel, with the majority using particle sizes less than 10 μm in order to assess the impact of wind resuspension stresses and surface roughness conditions on resuspension. Operational principles of the measuring devices used in the radionuclide resuspension experiments and corresponding uncertainties are discussed. The average bin-by-bin particle resuspension factors (ki) for particle sizes, in the range of 0.25–7.00 μm and 7.00–12.5 μm for downwind fallout locations, were calculated and are reported here as 1.14×10−3 1/m and 4.39×10−2 1/m, respectively.

Low-tide rainfall effects on metal content of suspended sediment in the Sacramento-San Joaquin Delta

Rain falling at or near low tide is capable of eroding and transporting cohesive sediment from intertidal areas. Given that metals adsorb strongly to silt- and clay-sized particles, it is conceivable that low-tide rainfall may also liberate previously-deposited metals from storage in intertidal sediment. To investigate the potential for rainfall as an agent of remobilization, this study tested the hypothesis that suspended sediment in a tidal creek during low tide rainfall events contains different suites of adsorbed metals than during wind-only events and fair weather days. Water samples were collected during low-tide rain events in winter and wind resuspension events in summer. The concentrations of suspended sediment, particulate organic carbon and nitrogen, and the total adsorbed concentration (gL−1) of most metals were higher for a low-tide rainfall event than during wind-only and fair-weather conditions. Metal contents (gg−1) were also greater during the rain event for most metals. Principal components analysis and relationships between metal content and suspended sediment concentration suggest that rainfall during low tide can mobilize a different source of sediment than wind–wave resuspension and regular tidal action. The metal content of bulk sediment samples from around the study area could not be matched satisfactorily to the suspended sediment in any of the events. This implies that bulk sediment composition should not be used to extrapolate to suspended sediment composition in terms of adsorbed metal content.

A one‐dimensional eco‐geomorphic model of marsh response to sea level rise: Wind effects, dynamics of the marsh border and equilibrium

In this study we investigate the long term evolutionary trend of tidal marshes and their possible tendency to approach equilibrium. We account of the dynamic interaction between the marsh and its adjacent environment, allowing for both variations of marsh elevation and displacement of the marsh boundary. We thus consider a 1‐D configuration consisting of a tidal channel merging into a 1‐D marsh. Starting from some initial configuration of the channel we model how a salt marsh forms at the landward end of the channel and determine the long term evolution of the channel ‐ marsh configuration under different scenarios of relative sea level rise. Previously established results on the morphodynamic evolution of a tidal channel are extended accounting for the effects of vegetation and wind driven sediment resuspension in regions where tidal stresses are too weak to mobilize sediments. Results suggest that, for sufficiently low rates of relative sea level rise the marsh platform may be able to reach an equilibrium elevation, provided wind resuspension is able to maintain a sufficiently large sediment concentration close to the marsh boundary. This is in general agreement with recent results based on zero dimensional modeling. However, we find that the marsh boundary is unstable, as progradation or retreat is generally experienced depending on a delicate balance between tidal transport and transport driven by wind setup. In this sense, actual morphodynamic equilibrium is a rather exceptional and unstable state.

Enhancement of natural radionuclides in the surroundings of the four largest coal-fired power plants in Spain

The production of electricity in coal-fired power plants (CFPP) is considered a NORM (Naturally Occurring Radioactive Materials) activity because the coals they burn can present relatively high contents of the naturally occurring radionuclides. In this study, the main radiological impact pathways into the surrounding environments of the four largest coal-fired power plants in Spain were analyzed. These pathways are, first, atmospheric evacuations and wind resuspension and, second, effluent evacuations to nearby rivers or directly to the sea. The atmospheric releases of radionuclides were evaluated by the analyses of soil profiles in the vicinities of the CFPPs. No significant enhancement of radionuclides in the surface soil was observed at the points of maximum deposition of combustion gases, located from 4.3 to 13 km away depending on the considered CFPP. However, an increase of (40)K, (226)Ra, and (232)Th in the surface soils was observed in the first kilometre from the chimney for two CFPPs. This suggested that these radionuclides were released in particulate form. There was also a net influence of the climate in which the CFPPs were located. This was observed in the two CFPPs that were in dry environments, while no increase was observed in the other two, located in more humid environments. The liquid effluents released usually presented an enhancement of dissolved chemical species regarding the initial intake water. Enrichments of the (234,238)U and (226)Ra contents in the water used in the plants' routine procedures were observed, and of (210)Po in the wastewater of just one of the plants. In any case, this enhancement was below the parametric value for the Total Indicative Dose for the hypothetical human consumption of the released waters. As a consequence of these releases of radionuclides, local products destined for human consumption produced in the vicinity of the facilities might incorporate natural radionuclides by these pathways, finding no significant enhancement of the natural radionuclide contents due to the CFPPs.

Effects of Land-Use Change on Characteristics and Dynamics of Watershed Discharges in Babeldaob, Palau, Micronesia

This study assessed the impacts of differing levels of land development in four watersheds in Palau on river sediment yield and on sedimentation and turbidity. Area corrected sediment yield was strongly related to land development (r2=0.96,P=0.02), varying from 9.7 to 216 tons km−2yr−1between the least and most developed watershed. Mean sedimentation rates on reefs ranged from 0.7 to 46 mg cm−2d−1, and mean turbidity ranged from 9 to 139 mg l−1. The higher values exceeded those known to harm corals. Because Palau's watersheds and estuaries are small, river floods were short-lived (typically lasting less than a day) and the estuaries adjusted just as quickly to a number of different estuarine circulation patterns that, in turn, generated a large variability in the export of riverine fine sediment to the reefs. The ultimate fate of the fine sediment deposited on the reefs depended on wind resuspension, local currents, and geomorphology (whether the bay was open or semi-enclosed). Palau's small estuaries were generally not as effective as bigger estuaries in trapping sediments and thus at sheltering the reefs. Therefore, greater efforts are needed to control and mitigate land activities that contribute to the increase in sediment yield.

Suspended particulate matter in Lake Erie derived from MODIS aquatic colour imagery

This paper explores the use of Moderate Resolution Imaging Spectroradiometer (MODIS) wavebands in the red/near-infra-red for estimating concentrations of suspended particulate matter (SPM) in the moderately turbid, optically complex waters of Lake Erie. Observations show that at wavelengths shorter than 550 nm, more than 50% of the absorption signal is accounted for by dissolved organic matter and phytoplankton, confirming that algorithms incorporating these wavelengths may not be appropriate for these waters. Single band and band ratios at wavelengths greater than 667 nm are tested for their suitability for monitoring SPM concentrations in these waters. A simplified regional semi-analytical model is utilized which is independent of variations in dissolved organic matter and chlorophyll absorption, enabling estimates of SPM concentrations from MODIS water-leaving radiance at 748 nm with an average root mean square (RMS) error of 40%. Knowledge of the vertical distribution of particles enables estimates of total water column suspended loads which are then related to wind re-suspension events. The method is applied to MODIS water-leaving radiance at 748 nm to produce a time series of surface and total water column suspended loads in Lake Erie for the period 2003–2007.

On the significance of wind event frequency for particulate resuspension and light attenuation in coastal waters

Wind-induced resuspension of particulate matter was investigated in a shallow coastal region off southwestern Australia, chosen for its isolation from the complexity of other confounding physical processes. The site had negligible river discharge, low nutrient concentrations and was largely devoid of tidal currents. Moorings were deployed in the micro-tidal waters to measure current speed, wave parameters, backscatter, subsurface irradiance and dissolved oxygen concentration. Two contrasting sites were chosen as representative of high and low wave-energy environments. Turbulent kinetic energy, recorded by the instruments, was dominated by the wind-wave signal. During wind events, at the most exposed site, bed shear stress exceeded the critical stress required to lift and resuspend sediments. At the most enclosed site, bed shear stresses only exceeded the critical stress required to suspend less dense material such as benthic fluff. Wind-waves were found to be the dominant mechanism driving the vertical redistribution of particulate matter. Low frequency storm events and high frequency (daily) sea breezes were found to differ significantly in their retention of particulate matter suspended in the water column. Long periods of calm generally followed the passage of a storm, allowing suspended particulate matter to settle out, while consecutive daily sea breezes were more effective in holding particulate matter in suspension. Linear correlations were found between the backscatter (a proxy for suspended particulate matter), light attenuation and dissolved oxygen concentration. Approximately half the variability in dissolved oxygen concentration could be attributed to the variability in light attenuation, with a decline in concentration during wind resuspension events. Variability in dissolved oxygen concentration was interpreted as a possible indicator of the moderation of pelagic phytoplankton productivity during wind events.

PM10 source apportionment in the surroundings of the San Vicente del Raspeig cement plant complex in southeastern Spain

The concentrations of trace metals, ionic species, and carbonaceous components in PM(10) (particulate matter with aerodynamic diameters smaller than 10µm) were measured from samples collected near an industrial complex, primarily composed of cement plants, in southeastern Spain, from September 2005 to August 2006. Positive matrix factorization and conditional probability function were applied to this data set to identify different types of sources. Six significant sources were identified: crustal matter, traffic, aged sea salt, industrial emissions, secondary aerosol, and sea salt. The difficulty of separating anthropogenic sources from those of natural origin is highlighted in this study; in particular, the crustal source can be connected with both natural (African outbreaks, wind resuspension) and man-made emissions, like fugitive emissions in an industrial environment.

Temporal and spatial dynamics of inherent and apparent optical properties in a shallow coastal lake (Fogliano Lagoon, Circeo National Park)

1 - The spatial and temporal dynamics of apparent and inherent optical properties in the coastal lagoon of Fogliano were measured in three seasonal surveys in 2002. Ultraviolet and visible solar irradiance data from in situ measurements permitted to estimate the related attenuation coefficients. The extinction measurements on filtered (0.22 μm) and unfiltered water samples were also performed. The integrated approach between in situ and laboratory measurements allowed the determination of the role of the suspended and dissolved matter in the attenuation and extinction of ultraviolet and visible radiation within the water column. 2 - The impact of the suspended matter on the lake optical quality was influenced by wind resuspension of particulate matter: the relative role of dissolved matter in the absorption of UV and visible radiation was prevailing at low wind velocity conditions (less than 2.2 ms -1 ), while at high wind velocities (3.9 ms -1 ), particulate matter resuspension strongly influenced the attenuation and the extinction measurements. It is a surprise that the dissolved matter is not influenced by the resuspension. 3 - The extinction in the analyzed wavelengths of filtered and unfiltered water samples and the in situ irradiance measurements allowed us to define new optical parameters and important correlations with limnological and classical optical measurements. 4 - By sampling at high spatial resolution (18 stations in 4 km 2 ), it was possible to evidence a spatial gradient of the optical and limnological properties, these distributions showed a consistent pattern in all three surveys, and were important for the characterisation of the chromophoric dissolved organic matter that was estimated with the spectral slope of the extinction curve spectra. A relatively higher spectral slope was found in the southern basin respect to the northern, where the maximum values of the attenuation coefficients and limnological parameters were found. 5 - These results suggest different sources of dissolved organic matter and/or a different level of photobleaching.