Deposition Of Suspended Particulate Matter Research Articles

Air pollution mitigation and suspended particulate matter retention potential of selected plant species across seasonal variation in the urban area.

Air pollution is a pressing environmental concern in urban areas, especially in densely populated cities like Delhi, India. However, plant species can effectively capture airborne suspended pollutants. Given this, the present study aimed to investigate the seasonal variations (pre- and post-monsoon) in the pollution-mitigating potential, biochemical characteristics, and suspended particulate matter (SPM) capturing capacities of select plant species in Delhi. Also, using biochemical parameters, plant morphology, and socioeconomic factors, the study computed tolerance indices such as the Air Pollution Tolerance Index (APTI) and Anticipated Performance Index (API). Ficus religiosa L. exhibited the highest APTI value of 11.94, while Polyalthia longifolia (Sonn.) Thwaites displayed the lowest 7.99 APTI value during the pre-monsoon. Ficus benghalensis L. showed the maximum SPM adhesion on the leaves, with a deposition of 1305.46µg/cm2, whereas F. religiosa exhibited the lowest SPM deposition of 56.62µg/cm2. Moreover, the statistical analysis indicated a positive correlation between ascorbic acid and chlorophyll content (R2 > 0.6) with APTI. Also, F. religiosa demonstrated a significant Pearson's correlation (P < 0.05) between chlorophyll content and SPM deposition during the pre-monsoon. The study highlighted the dynamic nature of plant-based air pollution mitigation. It offered valuable insights into the potential of green infrastructure as a sustainable solution for addressing air quality concerns in urban environments. The results emphasized the significance of selecting adequate plant species and considering seasonal variations in developing urban greening strategies to combat air pollution.

Dynamics of Suspended Particulate Matter in an Impounded River Under Dry and Wet Weather Conditions

AbstractThe dynamics of suspended particulate matter (SPM) and SPM‐associated biological and physicochemical processes in a river vary under dry and wet weather conditions and hydraulic structures, which moves a free‐flowing river to a semi‐lacustrine environment. This study investigated the response of SPM dynamics and riverbed morphodynamics to climate and anthropogenic stressors based on in‐situ observations and biogeochemical analyses of river water and riverbed sediment. The biochemical analyses and flocculation tests demonstrate abundant biopolymers and high flocculation potential of the river water during the pre‐flood period with algal bloom. This might promote SPM deposition and high‐concentration sediment layer (HCSL) formation on the riverbed. The high fractions of clay minerals and organic carbon in the riverbed sediment indicate the deposition of organic‐rich biomineral flocs. Vertical turbidity profiles with “long tails” of high turbidity near the riverbed also confirmed SPM deposition and HCSL formation. However, the highly turbulent flow conditions during the post‐flood period disturbed the tails of high turbidity and homogenized the vertical profiles of turbidity, temperature, and dissolved oxygen. Additionally, terrestrial humic substances were discharged from the watershed during this period, increasing the deflocculation and stabilization of SPM but decreasing deposition on the riverbed, thereby reducing the fractions of clay minerals and organic carbon in the sediment. This study demonstrated the interaction mechanism of SPM dynamics and riverbed morphodynamics with hydrological and biogeochemical processes in an impounded river under dry and wet weather conditions. The findings provide insights into water resource management to deal with climate change and anthropogenic stressors.

Effect of capping mode on control of phosphorus release from sediment by lanthanum hydroxide.

The use of in situ active capping to control phosphorus release from sediment has attracted more and more attentions in recent years. It is important to identify the effect of capping mode on the control of phosphorus release from sediment by the in situ active capping method. In this study, the impact of capping mode on the restraint of phosphorus migration from sediment into overlying water (OW) by lanthanum hydroxide (LH) was studied. Under no suspended particulate matter (SPM) deposition condition, LH capping effectively restrained the liberation of endogenous phosphorus into OW during anoxia, and the inactivation of diffusive gradient in thin film-unstable phosphorus (UPDGT) and mobile phosphorus (PMobile) in the topmost sediment served as a significant role in the restraint of endogenous phosphorus migration into OW by LH capping. Under no SPM deposition, although the transformation of capping mode from the single high dose capping to the multiple smaller doses capping had a certain negative impact on the restraint efficiency of endogenous phosphorus liberation to OW by LH in the early period of application, it increased the stability of phosphorus in the static layer in the later period of application. Under SPM deposition condition, LH capping had the capability to mitigate the risk of endogenous phosphorus liberation into OW under anoxia conditions, and the inactivation of UPDGT and PMobile in the topmost sediment was a significant mechanism for the control of sediment phosphorus liberation into OW by LH capping. Under SPM deposition condition, the change in the covering mode from the one-time high dose covering to the multiple smaller doses covering decreased the efficiency of LH to limit the endogenous phosphorus transport into OW in the early period of application, but it increased the performance of LH to restrain the sedimentary P liberation during the later period of application. The results of this work suggest that the multiple LH capping is a promising approach for controlling the internal phosphorus loading in freshwater bodies where SPM deposition often occurs in the long run.

Investigating theBiochemical Responses in Wheat Cultivars Exposed to Thermal Power Plant Emission.

The current study aimed to assess how high concentrations of ozone (O3) and suspended particulate matter (SPM) alter biochemical properties of high yielding wheat cultivars (i.e., HD3086 and HD2967) grown under 10km radius in 8 villages, located around Thermal Power Plant (TPP), Auraiya, Uttar Pradesh, India. Significant foliar damage was brought on by O3 and SPM exposure in both wheat cultivars and noted for consecutive 2 years as per emission patterns, air movement and biochemical defense capabilities. The detected air pollutants at the chosen experimental site ranged from 34 to 46ppb O3 and 139-189µg/m3 SPM. Range of biochemical parameter for both cultivars are as pH 6.6-7.1, relative water content (RWC) 44-62%, chlorophyll 0.23-0.35mg/g, ascorbic acid (AA) 54-68mg/g and air pollution tolerance index (APTI) 47-72. It has been observed that SPM deposition had a meaningful impact (P-value = 0.05) on the chlorophyll, pH, RWC and APTI.

From macrophyte to algae: Differentiated dominant processes for internal phosphorus release induced by suspended particulate matter deposition

In shallow lakes, eutrophication leads to a shift of the macrophyte-dominated clear state towards an algae-dominated turbid state. Phosphorus (P) is a crucial element during this shift and is usually concentrated in the suspended particulate matter (SPM) in water. However, the dominant processes controlling internal P release in the algae- (ADA) and macrophyte-dominated (MDA) areas under the influence of P-concentrated SPM remains unclear. In this study, we conducted monthly field observations of P exchange across the sediment-water interface (SWI) with the deposition of SPM in the ADA and MDA of Lake Taihu. Results revealed that both algae- and macrophyte-originated SPM led to the depletion of oxygen across the SWI during summer and autumn. Redox-sensitive P (Fe-P) and organic P (Org-P) were the dominant mobile P fractions in both areas. High fluxes of P across the SWI were observed in both areas during the summer and autumn. However, the processes controlling P release were quite different. In MDA, P release was mostly controlled by a traditional Fe-P dissolution process influenced by the coupled cycling of iron, sulfur, and P. In the ADA, Org-P control was intensified with the deterioration of algal bloom status, accompanied with the dissolution of Fe-P. Evidence from the current study revealed that the dominant process controlling the internal P release might gradually shift from Fe-P to a coupled process of Fe-P and Org-P with the shift of the macrophyte- to an algae-dominated state in shallow eutrophic lakes. The differentiated processes in the MDA and ADA should be given more attention during future research and management of internal P loadings in eutrophic lakes.

Impact on growth and yield of Rice (Oryza sativa) Cultivars (PB1509 and Arize6444) from SPM deposition under Thermal Power Plant Air Shed

The impact of environmental pollution (such as air pollution) on agricultural costs has received a great deal of global attention in the last 20 years. In recent years, air pollution has received serious concerns from researchers, media and the public sectors, but air pollution from agricultural production activities has not received enough attention. Air pollution is considered to be one of the major reasons for the deterioration in crops growth and productivity. The present study was carried out to explore the effect of total suspended particulate matter (SPM) deposition prevailing in the air shed (10km radius) of Thermal Power Plant (TPP), Auraiya on yield of of rice cultivars (PB1509 and Arize6444). The rice cultivars were grown for two consecutive years on farmers field of selected 8 villages located within the air shed. The SPM deposition on rice cultivars flag leaves was maximum (3.1mgcm-2) at Singanpur within 2-4 km area on the leeward side from the TPP and less impact was seen on the windward side 7-9 km at Hajiyapur (1.7 mgcm-2). Leaf area index (LAI) range of both cultivars was from 1.3 to 3.9. Yield and LAI were adversely affected by SPM deposition. Among two cultivars, the yield of Arize6444 was more adversely affected than PB1509.

Fluorescence Spectral Characteristics of Dissolved Organic Matter in Songhua Lake Sediment

Dissolved organic matter (DOM) has a significant impact on the main pollution indicators of the lake (e.g., COD), and sediment is the main source of pollution in the lake. Research on the fluorescence spectral characteristics of DOM in sediments is important to reveal the mechanism of lake pollution. In this study, sediments were collected from 20 sites in Songhua Lake. The DOM components in the sediment were analyzed using the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) technique, and the properties of the sediment DOM were clarified via spectroscopy. Additionally, the relationship between DOM and eutrophication of the water column was explored. The results showed that four components were identified from the sediment DOM of Songhua Lake:humic-like C1 (330/415 nm), C2 (255/440 nm), C3 (365/470 nm), and protein-like C4 (280/355 nm). The high HIX and low BIX indicated that the source of sediment DOM was mainly terrestrial and included some biological sources. The spatial distribution of the fluorescence intensity of the four components was relatively similar, showing that the fluorescence intensity was higher in the upstream (S1-S7) than that in the downstream (S8-S20). The massive deposition of suspended particulate matter (SPM) carried by the three rivers (Huifa River, Songhua River, and Jiao River) was the main reason for this spatial distribution. Eutrophication status in the water column of Songhua Lake was similar to the fluorescence intensity distribution of sediment DOM. Meanwhile, there was a strong correlation between eutrophication level and sediment DOM fluorescence intensity in the downstream water column of Songhua Lake.

The Resuspension and Deposition of Biomediated Sediments in Upper South Cove, Nova Scotia, Canada

Sutherland, T.F.; Amos, C.L., and Grant, J., 2022. The resuspension and deposition of biomediated sediments in Upper South Cove, Nova Scotia, Canada. Journal of Coastal Research, 38(1), 19–34. Coconut Creek (Florida), ISSN 0749-0208. Coastal seabed sediment stability is mediated by microalgal and bacterial biofilms. The resuspension of organic suspended particulate matter (SPM) in biomediated sediments increases nutrient fluxes to the water column and supplements particulate food supplies for suspension feeders. Thus, quantifying benthic-pelagic exchange pathways of biogeochemical parameters is essential to provide an accurate assessment of carrying capacities of coastal embayments supporting both natural and cultured bivalve populations. Benthic-pelagic transport coefficients such as erosion threshold (U*CRIT-SPM-EROSION), net erosion rate (NERSPM), peak erosion rate (PERSPM), depositional threshold (U*CRIT-SPM-DEPOSITION), and deposition rate (DRSPM) were determined using an in situ benthic flume (Sea Carousel) in the protected inner termination of Upper South Cove (USC). The layered gel-like muddy seabed consisted of a thin biofilm or flocculated material overlying highly reduced black sediments. Eroded material was analyzed for concentrations of SPM, chlorophyll-a (CHL), phaeopigment (PHA), and organic/inorganic content. All stations exhibited a consistent pattern of staggered erosion thresholds of seabed constituents, where U*CRIT-SPM > U*CRIT-PHA > U*CRIT-CHL. Erosion thresholds of these sediment constituents were inversely related to NERSPM, NERCHL, and NERPHA fluxes as part of a principal component analysis. U*CRIT-SPM-EROSION was generally higher than U*CRIT-SPM-DEPOSITION across the individual USC stations, suggesting that SPM deposition largely occurs before erosion. A tight coupling was observed between both the mean NERSPM (1.37×10–3 kg m–2 s–1) and DRSPM (1.23×10–3 kg m–2 s–1) and the occurrence frequency between erosion (44.2%) and deposition (52.5%) phases derived from a 4-day U* time-series profile. Although these results highlight a tight benthic-pelagic coupling system in USC, some overlap appears to occur between the deposition and erosion phases, which can be attributed to the presence of diverse SPM size classes that alter during erosion (shearing) and velocity deceleration (floc-forming) processes. Benthic-pelagic coupling supports the sustained near-bottom turbidity conditions observed in USC.

Analysis of Suspended Particulate Matter and Its Drivers in Sahelian Ponds and Lakes by Remote Sensing (Landsat and MODIS): Gourma Region, Mali

The Sahelian region is characterized by significant variations in precipitation, impacting water quantity and quality. Suspended particulate matter (SPM) dynamics has a significant impact on inland water ecology and water resource management. In-situ data in this region are scarce and, consequently, the environmental factors triggering SPM variability are yet to be understood. This study addresses these issues using remote sensing optical data. Turbidity and SPM of the Agoufou Lake in Sahelian Mali were measured from October 2014 to present, providing a large range of `values (SPM ranging from 106 to 4178 mg/L). These data are compared to satellite reflectance from Landsat (ETM+, OLI) and MODIS (MOD09GQ, MYD09GQ). For each of these sensors, a spectral band in the near infrared region is found to be well suited to retrieve turbidity and SPM, up to very high values (R2 = 0.70) seldom addressed by remote sensing studies. The satellite estimates are then employed to assess the SPM dynamics in the main lakes and ponds of the Gourma region and its links to environmental and anthropogenic factors. The main SPM seasonal peak is observed in the rainy season (June to September) in relation to precipitation and sediment transport. A second important peak occurs during the dry season, highlighting the importance of resuspension mechanisms in maintaining high values of SPM. Three different periods are observed: first, a relatively low winds period in the early dry season, when SPM decreases rapidly due to deposition; then, a period of wind-driven resuspension in January‒March; and lastly, an SPM deposition period in April–May, when the monsoon replaces the winter trade wind. Overall, a significant increase of 27% in SPM values is observed between 2000 and 2016 in the Agoufou Lake. The significant spatio-temporal variability in SPM revealed by this study highlights the importance of high resolution optical sensors for continuous monitoring of water quality in these poorly instrumented regions.

Remediation of internal phosphorus loads with modified clays, influence of fluvial suspended particulate matter and response of the benthic macroinvertebrate community

Clay-based phosphorus (P) sorbents have been increasingly used as geoengineering materials for the management sediment-derived internal P loading in eutrophic lakes. However, the long-term behavior of these sorbents has remained elusive along with their response to burial under suspended particulate matter (SPM), and their effect on macroinvertebrate communities occupying dynamic regions at the sediment-water interface of shallow and turbid lakes. In this study, field mesocosm experiments were undertaken in Lake Chaohu, China, to study the effects of the application of lanthanum-modified bentonite (LMB) and thermally-modified calcium-rich attapulgite (TCAP) on sediment internal P loading and to assess their influence on macroinvertebrate community structure. A complementary laboratory core incubation study was also undertaken to investigate the effects of SPM deposition on LMB and TCAP performance. In the field, both LMB and TCAP effectively intercepted P released from sediment for up to five months. A P fractionation analysis indicated that LMB and TCAP application results in a substantial increase in inert P fractions in sediment. Laboratory studies indicated that deposition of SPM may increase in mobile P both in the upper sediment and across the new post-SPM deposition sediment-water interface. Importantly, a comparison of sediment chemical extractions and estimated P fluxes suggests that chemically-defined forms of P in the sediment may be used as a proxy to estimate the net sediment P flux. Significantly, the surficial application of either LMB or TCAP did not cause negative effects on macroinvertebrate communities. This study indicates that to sustain a low P flux across the sediment-water interface in shallow, turbid lakes, repeat dosing of geoengineering materials, temporally aligned to the deposition of fluvial SPM, may be required.

Nitrogen exchange across the sediment-water interface after dredging: The influence of contaminated riverine suspended particulate matter

Dredging has been widely implemented in shallow lakes to reduce internal nitrogen (N) loading. The suspended particulate matter (SPM) coming from polluted rivers usually contains high levels of N and ultimately deposits on the dredged sediment surfaces near the river mouth. To study the influence of the riverine SPM on N exchange across the sediment-water interface (SWI) after dredging, a 360-day experiment was carried out comparing un-dredged and dredged sediments from Lake Chaohu, China. Dredged treatments showed a significant increase (p < 0.01) in total N concentrations in the sediments, while the deposition of SPM had little influence on labile NH4+-N concentrations. In addition, NH4+-N concentrations in pore-water and NH4+-N fluxes were significantly lower in dredged than in un-dredged sediments, despite the deposition of SPM. The oxygen production rates and the oxygen penetration depth in the dredged sediments were both higher than those in the un-dredged sediments. The increase of Nitrospira in dredged sediments was consistent with their decreased NH4+-N concentrations and fluxes across the SWI. Therefore, the oxidizing condition, increased oxygen production/consumption rates and Nitrospira relative abundance across the SWI were believed to be correlated with the low N exchange rates in dredged sediments. Dredging for reducing internal N loading in a river mouth area is therefore feasible, although the influence of the riverine SPM should be taken into account when aiming to achieve a long-term internal N loading reduction.

Applying Process-Based Models for Subsurface Flow Treatment Wetlands: Recent Developments and Challenges

To date, only few process-based models for subsurface flow treatment wetlands have been developed. For modelling a treatment wetland, these models have to comprise a number of sub-models to describe water flow, pollutant transport, pollutant transformation and degradation, effects of wetland plants, and transport and deposition of suspended particulate matter. The two most advanced models are the HYDRUS Wetland Module and BIO-PORE. These two models are briefly described. This paper shows typical simulation results for vertical flow wetlands and discusses experiences and challenges using process-based wetland models in relation to the sub-models describing the most important wetland processes. It can be demonstrated that existing simulation tools can be applied for simulating processes in treatment wetlands. Most important for achieving a good match between measured and simulated pollutant concentrations is a good calibration of the water flow and transport models. Only after these calibrations have been made and the effect of the influent fractionation on simulation results has been considered, should changing the parameters of the biokinetic models be taken into account. Modelling the effects of wetland plants is possible and has to be considered when important. Up to now, models describing clogging are the least established models among the sub-models required for a complete wetland model and thus further development and research is required.

The mismatch between bioaccumulation in field and laboratory environments: Interpreting the differences for metals in benthic bivalves

Laboratory-based bioaccumulation and toxicity bioassays are frequently used to predict the ecological risk of contaminated sediments in the field. This study investigates the bioassay conditions most relevant to achieving environmentally relevant field exposures. An identical series of metal-contaminated marine sediments were deployed in the field and laboratory over 31 days. Changes in metal concentrations and partitioning in both sediments and waters were used to interpret differences in metal exposure and bioaccumulation to the benthic bivalve Tellina deltoidalis. Loss of resuspended sediments and deposition of suspended particulate matter from the overlying water resulted in the concentrations of Cu, Pb and Zn (major contaminants) becoming lower in the 1-cm surface layer of field-deployed sediments. Lower exchange rates of overlying waters in the laboratory resulted in higher dissolved metal exposures. The prediction of metal bioaccumulation by the bivalves in field and laboratory was improved by considering the metal partitioning within the surface sediments.

Impact of aerial deposition from thermal power plant on growth and yield of rice (Oryza sativa) and wheat (Triticum aestivum)

Thermal power plants (TPP) are a major source of air pollutants particularly suspended particulate matter (SPM) which either remains suspended in air or gets deposited onto soil surface and crop canopy in adjoining areas thereby affecting the growth and productivity of crops. Keeping this in view, a study was undertaken near Dadri TPP situated at NTPC Dadri, Uttar Pradesh, to assess the impact of aerial deposition on crops grown in adjoining areas. Eight different locations situated in different villages located at varying distance within 1-10 km radius were selected for study. Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) fields were identified in the selected villages and their growth and yield parameters were recorded during the entire crop duration. Aerial deposition load on crop canopy was also quantified. Results showed that rice and wheat crops grown nearer to the TPP were most affected in terms of reduction in growth and yield as compared to fields located at far off distances. This was attributed to the deposition of SPM on rice and wheat leaves, which reduced photosynthesis rate leading to lower leaf area index, biological and grain yield of both the crops. In wheat crop, aerial deposition load on leaves was found to be more than rice at all stages. Reduction in grain yield in rice within10 km radius were 13.5% and 20.4%, while in wheat reduction were 21.9% and 19.1% in first and second year of study, respectively. The zone of 1 to 3 km radius from the TPP was found to be most vulnerable in terms of yield loss both in rice and wheat crops. In this zone some more resistant alternative crops can be grown which will help farmers to increase their productivity and income.

Geochemistry of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang Estuary

The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred. In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang estuarine surface waters.

The impact of electric overhead radiant heating on the indoor environment of historic churches

The impact of electric overhead radiant heaters on the microclimate, air flows, transport and deposition of suspended particulate matter (SPM) was monitored between March 2004 and March 2005 in the historic churches of Saint Michael Archangel in Szalowa and Saint Catherine in Cracow (Poland). The measurements show that although irradiation at the floor level increases temperature and reduces relative humidity in the interior of the church, the effect out of the heated zone and for the surfaces sheltered from irradiation is very limited, i.e. their extent is comparable with natural fluctuations inherent to the local climate of the church. The radiant heaters proved to generate little convectional flow of the air. Therefore, the heating system was not found to increase the concentration of SPM indoors; in particular, no re-suspension of particles already present in the church was observed. This work has demonstrated that the overhead radiant heaters are capable of providing localised heat to the areas where people congregate without adversely affecting painted walls and the works of arts displayed in churches. Care, however, should be taken that sensitive works of art are not exposed to the direct infrared radiation.

Floc size and settling velocity within a Spartina anglica canopy

There is increasing interest in tidal wetlands as mechanisms for sustainable and long-term coastal defence. The complexities of the interaction between the deposition of suspended particulate matter (SPM) and submerged vegetation, however, is to a large extent poorly understood. Consequently, accurate parameterisation of cohesive sediment settling fluxes in these environments is a crucial requirement for the development of high-resolution numerical models of wetland morphodynamics. A novel laboratory experiment is described in which the turbulent flow structure within a canopy of the halophytic macrophyte Spartina anglica is examined, and floc characteristics quantified using a unique floc camera configuration able to measure directly the full spectral floc size ( D) and settling velocity ( W s ). We provide the first quantitative observations of floc characteristics from shallow ( h<0.5 m), vegetated flows and investigate the potential influence that variations in vegetative density may have on flocculation, and thus depositional fluxes, in comparison to unvegetated flows. Turbid mud suspensions with concentrations of 100, 250 and 500 mg L −1 were sheared at current speeds of 0.1, 0.2 and 0.3 m s −1 through mono-culture arrays of S. anglica in an annular flume. Experimental stem densities were set at 200, 400 and 800 stems m −2. Mean absolute velocity exhibits an inverse, approximately exponential relationship with vegetative density. The threshold for maximum current attenuation (an 89–90% reduction of free stream velocity) is 400 stems m −2. D and W s range over 3 orders of magnitude from 20 to 1265 μm and from 3.96×10 −3 to 3.37 mm s −1, respectively. Maximum D is larger by a factor of 18 than that observed during the closest comparable in situ study. Our observations exhibit a pronounced positive skew due to incorporation of large, low-density, fast settling aggregates with maximum W s 33% greater than that used in current exploratory numerical models of saltmarsh surface deposition, and 236% greater than that observed during previous in situ studies. The inability to include the largest macroflocs (>160 μm)—the top 4% of our data set (ranked according to D) comprising 223 individuals between 250.46 and 1265.19 μm with settling speeds of 0.23–3.37 mm s −1)—may lead to serious under prediction of total mass settling flux (MSF). Parameterisation and incorporation of these observed distributions for use in numerical models of cohesive sediment deposition on saltmarsh surfaces is a high priority.

Controlling factors of rhythmic sedimentation processes on an intertidal estuarine mudflat — Role of the turbidity maximum in the macrotidal Seine estuary, France

The aim of this study is to analyse and to quantify the fine particles transfer (i.e.< 63 μm) in the marine part of the man-altered macrotidal Seine estuary (France) by (i) an analysis of a two year time-series of altimeter data, which reveals the bed elevation variations on an intertidal mudflatd located at the Seine mouth and (ii) measurements of the concentration of suspended particulate matter (SPM) contained within the turbidity maximum (TM). The results of this analysis reveal that sedimentation on the mudflat is mainly controlled by the dynamics of the TM such that during the largest spring tides (i.e. tidal ranges > 7.1 m). Then, deposition of SPM from the turbidity maximum becomes important, allowing fine particles to settle on the mudflat, where the current velocities are low (< 0.4 m s − 1 ). On tides of lower range (< 7.1 m) bed elevation levels suggest that erosion of the mudflat surface dominates, however dewatering processes also occur in the soft mud deposits resulting in compaction. During periods of wave activity and periods of increasing river discharge, the mudflat surface experiences rapid erosion. These periods of erosion (sudden or progressive) imply a transfer of fine-grained material from the mudflat surface back into the TM. The long term (∼ 22 months), high frequency (1 measurement every 10 min) and high resolution (0.6 mm) dataset obtained from the altimeter allows quantification of the volume of material exchanged between the intertidal area and the estuarine standing stock of SPM. The maximum of deposition on the studied mudflat during the study was of 27 cm, with highest deposition occurring after the periods of highest river flow and implying that between 25 and 40% of the maximum estimated mass of SPM held within the estuarine TM (300,000–500,000 T) had been temporarily deposited on the mudflat. Likewise following periods of resuspension by wave activity, bed elevations reduced by an order of ∼ 1 cm, suggesting a release of between 1–1.5% of the TM load from the mudflat back into suspension. The study shows that lateral exchanges of sediment between the intertidal reaches of the estuary and the water column are an important part of the sediment budget, and that the supply of sediment available for deposition (i.e. the TM) has a causal relationship with sedimentation rates experienced by intertidal mudflats.

Fluvial suspended sediment dynamics: Implications for particulate organic carbon transport modeling

The effect of fluvial suspended sediment aggregation on the hydrodynamic transport properties of particulate organic carbon (POC) was investigated using a combination of field measurement and numerical modeling. Field‐based settling tube experiments were conducted to obtain particle settling velocity frequency distributions of a 4‐km‐long section of a lake outlet river at two distinct discharge levels (6.8 and 29.7 m3 s−1). Results of field studies conducted in April 2001 and April 2002 showed that the lacustrine settling velocity frequency distributions of suspended particulate matter (SPM) and POC were altered owing to the formation of riverine aggregates having comparatively higher settling velocities. Data suggest that aggregation promoted deposition fluxes of POC; these fluxes were in turn closely tied to the processes that controlled deposition of SPM. Data interpretation was aided by the employment of a hydrodynamic sediment transport model. The approach used to integrate aggregation in the sediment transport simulations represents the interaction of multiple settling velocity mass fractions. Both field data and modeling demonstrated the effect of aggregation on the increase in deposition fluxes of POC.

Application of EDXRF and Thin Window EPMA for the Investigation of the Influence of Hot Air Heating on the Generation and Deposition of Particulate Matter

This paper presents a systematic micro-analytical study for the assessment of the influence of a typical hot-air “blow-in” heating system on the generation, transport and deposition of suspended particulate matter (SPM) in the church of Rocca Pietore (Italian Alps). This kind of heating system is very popular in cold regions due to its fast response and economic properties. The size, chemical composition and abundance of individual particles responsible for the negative impact on the displayed artworks are determined by ultra-thin window EPMA. EDXRF is used to determine the bulk chemical composition of SPM. Some gaseous pollutants (SO2, NO2 and O3) are sampled with the application of passive diffusion tubes and quantified with ion-chromatography and spectrophotometry. It is pointed out that several deterioration processes, such as the abrasion of the plastered walls, the re-suspension of the particulate pollution and the generation of NO2 gas, arise mainly from using the heating system. Each of these observations is a concern for the preservation of the displayed works of art.