Total Suspended Material Research Articles

Preliminary examination of influence of Chlorophyll, Total Suspended Material, and Turbidity on Satellite Derived-Bathymetry estimation in coastal turbid water

The satellite-Derived Bathymetry (SDB) has been researched for almost the past five decades, but the application of SDB for operational use is still in its initial stages. The higher concentration of suspended material is a major barrier in assessing bathymetry accurately with remote sensing data. The influence of various optically active substances (OAS) needs to be quantified to develop a more robust SDB algorithm. The goal of the study is to improve the accuracy of SDB by understanding the spatial distribution of Chlorophyll (Chl), Total Suspended Material (TSM), and Turbidity in coastal water. A preliminary investigation using the numerical analysis between Landsat-7 & 8 spectral bands, OAS parameters, and bathymetry is presented in this paper. SDB has been derived using three machine learning algorithms; Linear, Random Forest (RF), and Support Vector Machine (SVM) Regression. The resulting SDB residuals have been analyzed in relation to Chlorophyll, Turbidity, and TSM in coastal seawater. The study found that most of the erroneous SDB residuals and extreme values were distributed in high or medium concentrated OAS regions. The result of the study may further enhance SDB estimation accuracy by considering the influence of the above three OAS in coastal waters.

Spatio-temporal variability of Turbidity over Ukai Reservoir, by using RS2/R2A LISS III Satellite datasets

Turbidity is an optical determination of water clarity. It is one of the most important optically active water parameter to assess the water quality through the remote sensing observations. Turbidity measurements come from suspension of sediment such as silt or clay, inorganic materials, or organic matter such as algae, plankton and decaying material. Turbidity and total suspended matter often overlap each other. However, it is not a direct measurement of the total suspended materials in water. Instead, as a measure of relative clarity, turbidity is often used to indicate changes in the total suspended solids concentration in water without providing an exact measurement of solids. Through remote sensing we can monitor the turbidity in large water bodies, rives, coastal areas etc. An algorithm has been developed to estimate the turbidity (in NTU: Nephelometric Turbidity Unit) over inland waters (Ukai reservoir) using empirical relationship between normalized Green and Red bands (NDTI : Normalized Difference Turbidity Index) of Resourcesat-2 and Resourcsat-2A Linear Imaging Self Scanning-III (RS2 and R2A LISS-III) dataset. Derived algorithm shows a strong coefficient of determination (R2 = 0.97) with the in-situ turbidity measurements. The field measurements were carried out over Ukai reservoir on 27-28th March 2018, where synchronous in situ water leaving reflectance and turbidity were measured. Model was derived between in situ measured turbidity and NDTI derived from spectral reflectance of band 2 (Green) and band 3 (Red) of RS2 and R2A LISS-III. The model was applied to derive the turbidity maps of Ukai reservoir for pre-monsoon (March, April and May months) season during the period 2012 to 2018. Overall turbidity ranges from 1.47-20 NTU during the field data collection of pre-monsoon season and overall scene derived turbidity ranges are between 2 – 33 NTU. The highest observed turbidity value was more than fourteen times greater than the lowest value that shows the natural variability within the reservoir for the same season. Remotely sensed data sets can increase the abilities of water resources researchers and decision making persons to monitor waterbodies more effectively and frequently.

Evaluation and Monitoring of Water Quantity and Quality of the Buriganga River in Bangladesh using Multi-temporal Landsat Images

Buriganga River, the study area, is one of the most polluted and decreasing expeditiously its area in Bangladesh due to rapid urbanization, effluents of industries and factories surrounding the river, sewage disposal from Dhaka City and some anthropogenic activities. The objective of this study is to evaluate and monitor the water quantity and quality of the river using satellite remote sensing techniques. Unsupervised and indices based classification were used to derive and monitor landuse-landcover (LULC), surface water distribution (SWD), land surface temperature(LST) and total suspended material (TSM) using four sets of Landsat TM/ETM+/OLI/TIRS images of the study area from 1989 to 2015. The indices are Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI). LULC classification results showed that the water bodies and vegetation decreased and consequently urban as well bared area increased from 1989 to 2015. Results of indices (NDVI and NDWI) analysis are similar to that of unsupervised LULC outputs, that is, the water bodies decreased with increasing urban structures of the study area. The surface water distribution monitoring results from the suitable change detection GIS model indicate that the water bodies have decreased about 31.07% and accretion rate increased rapidly from 1989 to 2015 along the river bank due to urbanization and accretion activity is more prominent in north, northeast, northwest, south, southeast and eastern part. The study also shows that the rate of TSM is sporadically increasing during the study period i.e., the maximum and minimum value of TSM was 56215.53 and 1956 mg/l in 1989 and 14188714.35 mg/l and 333942 mg/l in 2015 respectively; this indicates that the water is harmful for aquatic life. Both the analyzed satellite image outcome and in situ observations reveal that land surface temperature is also increased in some part of the study area. The study results could be used to make policy for upgrading the water quality and to maintain the extent and water quantity for agriculture, navigation and fisheries sectors of the Buriganga River.
 The Dhaka University Journal of Earth and Environmental Sciences, Vol. 8(1), 2019, P 61-69

A Study Some Physical and Chemical Properties of Khuweisah Valley Basin East Of Misaan Governorateby Using Rs&Gis

The study dealt with some physical and chemical properties of khuweisah I order to Clearfy andhighlight contrast in those properties between two seasons, summerwho represented by (July) andwho represented by winter (January). Also high light contrast on differences among the sites during the same season for the period from (1987–2018).Three samples were chosen for each season in order to explain the differences. By analyzing the results of the properties temperature values are gradually increasing during the summer season due to atmospheric and solar radiation effects. Also showed the results that the values of turbidity had increased during summer seasondue to total suspended materials in the water.The dissolved oxygen concentrations in summer season were high due to increased concentrations of salts in this season, value of (PH) more salty in summer season, moderate during winter. Concentrations of other elements were variable among sites in the same season

Chlorophyll and Total Suspended Materials Concentrations and Remote Sensing Reflectance Data measured at the Red Tide Area of Jinhae, Geoje, and East Sea during August from 1998 to 2003 and August 2013

The chlorophyll and total suspended materials concentrations and remote sensing reflectance data were observed for red tides occurring every summer in waters around the Korean Peninsula. In observation area and date, the field survey were performed (1) in the Jinhae and Geoje coasts during August 1998, August 1999, August 2001, and August 2003, (2) in East Sea coast during August 2013. The remote sensing reflectance data were obtained from portable spectroradiometer. The chlorophyll concentration data were obtained from spectrophotometric method and the total suspended materials concentration data were obtained from filter-weight difference method. The remote sensing reflectance data were validated using Moon et al.(2012). The chlorophyll concentration data were validated using baseline correction and subtraction of 750 nm value, and the total suspended materials concentration data were validated using variation of humidity.

Catchment-scale influences on riverine organic matter in southern New Zealand

Riverine particulate organic matter (POM) is a critical vector for nutrient cycling of carbon at both regional and global scales. POM and suspended sediment (SS) are transported concomitantly through rivers, and their concentrations change in association to landscape transformations and natural fluctuations. The proportion of POM to SS mobilised in rivers under base flow is an important component of carbon flux to oceans, and is a useful metric for understanding hillslope–river coupling and hydraulic connectivity. We quantified POM during base flow conditions in southern New Zealand to assess the role of different catchment characteristics that control the spatial variability of organic matter in the fluvial environment. The proportion of POM to total suspended material (TSM) can be <5%, or much higher at 50–80% across southern New Zealand, with the highest concentrations associated with lowland agricultural catchments. Particulate organic carbon yields were estimated to be between 0.04 and 2.7 t km−2 a−1 discharged into the Pacific Ocean. The POM% responds to both intrinsic and extrinsic catchment characteristics, affecting the availability of organic material and mechanisms for transport including vegetation cover, topographic controls, and hydrological controls. Across southern New Zealand it is evident that riverine organic matter is spatially organised and connected to broader hillslope processes, albeit difficult to predict at the catchment scale.

Remote sensing, isotopic composition and metagenomics analyses revealed Doce River ore plume reached the southern Abrolhos Bank Reefs

On November 5th, 2015, the Fundão dam rupture released >50 million m3 of ore tailings into the Doce River, Minas Gerais State, Brazil. The huge volume of mud spread along the river and reached the sea, 17 days after the disaster, in Regência, Espírito Santo State (ES). In 2018, after three years of the disaster, the impacts of the ore tailings in the marine environment are still unclear. This study aims to investigate possible short-term impacts in marine biodiversity caused by the ore tailings' mud over the reef ecosystems that are closest to the disaster area: i.e. recently discovered reefs in the southern Abrolhos Bank. A remote sensing surveillance including winds, sea surface temperature, total suspended material and watercolor (MODIS Aqua data) indicated that the iron tailings plume reached the southern portion of Abrolhos Bank on June 16th, 2016. Subsequently, to obtain further evidence of the presence of the tailings in the coral reefs, water samples were collected in a gradient spanning from the river estuary to the reefs in southern Abrolhos Bank, we also analyzed the isotopic and microbial composition of the samples, as well as the reef benthic composition. Despite no clues of negative impact on benthic (coral) communities, isotopic analysis confirmed the presence of the plume over the reefs area. This study serves as a baseline for future long-term impact assessments of the health of coral reefs in the Abrolhos Bank.

Potential role of scallops Argopecten irradians in deposition of particulate nutrient and trace elements in a eutrophic estuary, northern China

Anthropogenic inputs of nutrients and trace elements have globally significant impacts on coastal waters. In order to evaluate the effect of the filter-feeding bay scallop Argopecten irradians on benthic-pelagic coupling in a eutrophic estuary (Laizhou Bay), biodeposition of total suspended materials, particulate nutrient (C, N, P) and trace elements (Cu, Zn, Pb, Cr, Cd, Hg, As) were determined using modified sediment traps during autumn 2013. Results showed that biodeposition rates of the bay scallops were rather high compared with those reported for other bivalves. The allometric relationship between the biodeposition rate (BDR; g ind.(-1) d(-1)) and soft tissue dry weight (W; g ind.(-1)) was modeled (BDR = aW(b)) with the value of a being 1.24 in September and dropping to 0.96 in October. The biodeposition contributed to the enrichment of organic matter, C and N in the local sediment. Trace element concentrations in the scallop biodeposits were significantly higher than those of the natural surrounding sediments, especially during the months of October and November. A. irradians significantly increases the mass fluxes from the water column to the bottom, with estimated 1140 tonnes of total suspended material being deposited to the seabed each day in the culture zone. Results also suggest that biotransformation and biodeposition by such efficient filter-feeders may play a pivotal role in the fate and transportation of particulate nutrient and trace elements in aquatic ecosystems. In coastal waters and estuaries subject to anthropogenic inputs, suspended bivalve aquaculture could be environmentally advantageous via intense filtering and biodeposition, potentially mitigating eutrophication trace and element pressures.

Silicon cycle in Indian estuaries and its control by biogeochemical and anthropogenic processes

We study the silicon biogeochemical cycle and its associated parameters in 24 and 18 Indian estuaries during dry and wet periods respectively. We focus more specifically on dissolved Si (DSi), amorphous Si (ASi,) lithogenic Si (LSi), Particulate Organic Carbon (POC), Total Suspended Material (TSM), Dissolved Inorganic Nitrogen (DIN), salinity and fucoxanthin, a marker pigment for diatoms. Overall, we show that the estuaries have strong inter and intra variability of their biogeochemical parameters both seasonally and along salinity gradients. Based on Principal Component Analysis and clustering of categorised (upper and lower) estuaries, we discuss the four major processes controlling the Si variability of Indian estuaries: 1) lithogenic supply, 2) diatom uptake, 3) mixing of sea water and, 4) land use. The influence of lithogenic control is significantly higher during the wet period than during the dry period, due to a higher particle supply through monsoonal discharge. A significant diatom uptake is only identified in the estuaries during dry period. By taking into account the non-conservative nature of Si and by extrapolating our results, we estimate the fluxes from the Indian subcontinent of DSi, ASi, LSi to the Bay of Bengal (211 ± 32, 10 ± 4.7, 2028 ± 317Gmol) and Arabian Sea (80 ± 15, 7 ± 1.1, 1717 ± 932Gmol). We show the impact of land use in watersheds with higher levels of agricultural activity amplifies the supply of Si to the coastal Bay of Bengal during the wet season. In contrast, forest cover and steep slopes cause less Si supply to the Arabian Sea by restricting erosion when entering the estuary. Finally, Si:N ratios show that nitrogen is always in deficit relative to silicon for diatom growth, these high Si:N ratios likely contribute to the prevention of eutrophication in the Indian estuaries and coastal sea.

Influence of water fluctuations on the limnological characteristics of two floodplain lagoons (Ribeira do Iguape Valley, state of São Paulo, Brazil)

Abstract Aim: Current study assessed the influence of hydrometric levels on the limnological characteristics of two river floodplain systems in the Ribeira do Iguape Basin (state of São Paulo, Brazil). Methods: Rainfall data were collected dailyfrom an automatic weather station in Jacupiranga SP Brazil and daily hydrometric level records were obtained from automatic linigraphs installed on the two adjacent rivers. Moreover, pH, electrical conductivity and dissolved oxygen were measured by a multiparametric probe. Water samples were collected to analyze nitrate, ammoniac nitrogen, total nitrogen and phosphorus, total alkalinity and suspended material. The samplings were carried out in April and July, representative months for low and high water periods, respectively. Results and Conclusions: Statistical analysis highlighted the “effect of homogenization”, attributed to the hydrological pulses in several studies carried out in river-floodplain systems. This effect in current study was more underscored at Lagoon 2, which remained connected for a longer period with the adjacent river, when compared to Lagoon 1- River Jacupiranguinha system. Higher dissolved oxygen concentrations at Lagoon 2, in contrast with the Lagoon 1 featuring anoxia during the whole period under analysis, were also attributed to the above-mentioned greater hydrological connectivity. Current study highlights that the water-mediated transferences during the high water period may contribute not only towards the fertilization of marginal lagoons (inputs of nutrients and organic matter) but also to significant pollutant loads, according to land use along the watersheds. In the case of Lagoon 1- River Jacupiranguinha system, even though further studies are needed and strongly recommended, it is reasonable to assume that the discharges of mining effluents into the river may result in ecological damage not only to the receiving water body but also to the connected ecosystems.

The cascade construction of artificial ponds as a tool for urban stream restoration — The use of benthic diatoms to assess the effects of restoration practices

A series of cascade artificial ponds were constructed to improve the ecological status of the stream. To evaluate the effects of restoration practices, a bioassessment, based on phytobenthic algae — the diatoms, was made. Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) of diatom assemblages allowed for evaluating the influence of a series of cascade artificial ponds on stream integrity. To reveal which environmental factors had the greatest influence on shaping diatom assemblages, the BIO-ENV procedure was used, and in order to examine whether these factors had equal influence on diatoms along the stream, Redundancy Analysis (RDA) was used. The analysis of diatom assemblages allowed for the calculation of the diatom indices in order to assess the water quality and the ecological status of the stream. Artificial ponds constructed on the stream had significant effects on the integrity of the stream ecosystem. Diatom assemblages characteristic of stream habitats were disrupted by the species from ponds. HCA and PCA revealed that the stream was clearly divided into three sections: ponds, stream parts under the influence of ponds, and stream parts isolated from ponds. The ponds thus altered stream environmental conditions. Benthic diatom assemblages were affected by a combination of four environmental factors: the concentration of ammonium ions, dissolved oxygen, conductivity, and the amount of total suspended material in the water. These factors, together with water pH, had a diverse influence on diatom assemblages alongside the stream, which was caused by a series of cascade ponds. In theory, this restoration practice should restore the stream close to its natural state, but bioassessment of the stream ecosystem based on diatoms revealed that there was no improvement of the ecological status alongside the stream. The construction of artificial ponds disrupted stream continuity and altered the character of the stream ecosystem.

Microbial activities and organic matter degradation at three sites in the coastal North Atlantic: Variations in DOC turnover times and potential for export off the shelf

The Mid-Atlantic Bight is a highly productive region where considerable quantities of organic matter are processed, transformed, and respired. Much of this organic matter is in the form of dissolved organic carbon (DOC). We investigated the activities of heterotrophic microbial communities responsible for DOC processing at three sites in the coastal Mid-Atlantic Bight/northern end of the South Atlantic Bight: near the Chesapeake Bay mouth, off Cape Hatteras, and near Cape Lookout, NC. Activities of endo- and exo-acting extracellular enzymes (polysaccharide hydrolases, and glucosidase and peptidases, respectively), and bacterial protein production were measured in surface and subsurface waters at the three stations. Total suspended material, cell counts, and particle-associated enzyme activities were also quantified. Water masses at each station showed distinct physical characteristics (temperature, salinity, total suspended material), and differed notably in rates and spectrum of enzyme activities, as well as in the fraction of particle-associated activities. Despite similar cell counts, bacterial productivity differed by a factor of ca. 30 among depths and stations. Glucosidase and peptidase activities differed by a factor of ca. 40 among stations, but the differences in enzyme activities among stations did not scale with the differences in bacterial productivity. Theoretical turnover times of dissolved carbohydrates – calculated from total dissolved carbohydrate concentrations and polysaccharide hydrolase activities – range from weeks to months, suggesting that dissolved carbohydrates may be among the components of DOC that can be advected from the Mid-Atlantic Bight into the open ocean, connecting the carbon cycle in the ocean margin with the ocean's interior.

Reconstruction of hyperspectral reflectance for optically complex turbid inland lakes: test of a new scheme and implications for inversion algorithms.

A new scheme has been proposed by Lee et al. (2014) to reconstruct hyperspectral (400 - 700 nm, 5 nm resolution) remote sensing reflectance (Rrs(λ), sr-1) of representative global waters using measurements at 15 spectral bands. This study tested its applicability to optically complex turbid inland waters in China, where Rrs(λ) are typically much higher than those used in Lee et al. (2014). Strong interdependence of Rrs(λ) between neighboring bands (≤ 10 nm interval) was confirmed, with Pearson correlation coefficient (PCC) mostly above 0.98. The scheme of Lee et al. (2014) for Rrs(λ) re-construction with its original global parameterization worked well with this data set, while new parameterization showed improvement in reducing uncertainties in the reconstructed Rrs(λ). Mean absolute error (MAERrs(λi)) in the reconstructed Rrs(λ) was mostly < 0.0002 sr-1 between 400 and 700nm, and mean relative error (MRERrs(λi)) was < 1% when the comparison was made between reconstructed and measured Rrs(λ) spectra. When Rrs(λ) at the MODIS bands were used to reconstruct the hyperspectral Rrs(λ), MAERrs(λi) was < 0.001 sr-1 and MRERrs(λi) was < 3%. When Rrs(λ) at the MERIS bands were used, MAERrs(λi) in the reconstructed hyperspectral Rrs(λ) was < 0.0004 sr-1 and MRERrs(λi) was < 1%. These results have significant implications for inversion algorithms to retrieve concentrations of phytoplankton pigments (e.g., chlorophyll-a or Chla, and phycocyanin or PC) and total suspended materials (TSM) as well as absorption coefficient of colored dissolved organic matter (CDOM), as some of the algorithms were developed from in situ Rrs(λ) data using spectral bands that may not exist on satellite sensors.

MEASURING SEA SURFACE SALINITY OF THE JAKARTA BAY USING REMOTELY SENSED OF OCEAN COLOR DATA ACQUIRED BY MODIS SENSOR

Observations on oceanographic parameters using remote sensing techniques intensively have been done for more than 3 decades for estimating and mapping the sea surface temperature (SST) and the abundance of phytoplankton expressed as the concentration of chlorophyll-a and applied them in studying the ocean phenomenon. As a result, the product of these 2 parameters for all over the oceans in the world has been established and available in daily basis. However, on the contrary, there is still limited application for sea surface salinity (SSS) which is also one of the most important oceanographic features. This paper describes a novel method of deriving SSS from remotely sensed ocean color. The method is based on two important observations of optical properties in regions of freshwater influences. The first is the strong effect of Colored Dissolved Organic Matter (CDOM or yellow substance) on ocean color when present in relatively high concentrations. The second is the close relationship between salinity and CDOM originating from fresh water runoff. In this paper, these relationships are demonstrated for the Jakarta Bay, Indonesia. The MODIS sensor in Terra and Aqua satellites imageries and 10 in situ measurements conducted near-simultaneously with the satellites over flight over the bay in 2004 and 2006 were implemented for deriving CDOM and SSS. The empirical relationships demonstrated in this study allow the satisfactory prediction of CDOM and SSS in the Jakarta Bay from remotely sensed ocean color. The root mean square (r.m.s) error difference between the observed and predicted parameters are 0.14 m-1 and 0.93 psu for CDOM g440 g and SSS, respectively, over a range of salinity from 24 to 33 psu. This range is in good agreement with field surveys. Parameters that may influence CDOM, such as Chlorophyll-a (CHL-a) and total suspended material (TSM) concentrations were also analyzed. Results showed that there were no relationship at all between CDOM and CHL-a, and between CDOM and TSM. These indicate that phytoplankton plays a minor role in regulating CDOM abundance, and also suggest that CDOM contribution from sediment and/or from sediment resuspension is negligible. Thus, CDOM sources in the Jakarta Bay are mainly from riverine inputs. SSS maps created from the satellite-retrieved ocean color identify features in the surface salinity distribution such as salinity front of &gt; 32 psu that migrated in and out of the bay according to seasons. Therefore, the ability to obtain synoptic views of SSS such as presented in this paper provides great potential in furthering the understanding of coastal environments.

Temporal variability of suspended sediment transport and rating curves in a Mediterranean river basin: The Celone (SE Italy)

In the Mediterranean region suspended sediment transport is the predominant process in sediment export in most river basins. The aim of this paper is to analyze suspended sediment variability over a period of 12months in the Celone river, a temporary river located in the Puglia region (SE-Italy), and to evaluate sediment rating curves for estimating suspended sediment concentrations for subsequent load calculations. Similarly to most temporary rivers, the Celone river shows relevant differences among mean daily flows and the extreme instantaneous flows during floods. To take into account these peculiarities, the rating curves were developed as a function of hydrological conditions: high, normal and low flows. Continuous measures of streamflow and frequent samplings of suspended solid concentrations (SSCs) during flood events, normal flow and low flow were used. The plot of the SSC against discharge takes the form of a hysteresis loop. Clockwise, anticlockwise and mixed-shaped loops were observed. Suspended sediment yield was found to be in the range of 250–384tkm−2y−1. The results show that about 94% of the total suspended materials were transported during the high flow regime, while less than 0.1% were under low flow conditions. Moreover, it was observed that 90% of the total annual suspended loads were moved between November to May. Flash floods that occur in summer exhibit the highest values of SSC. The proposed method, which was based on sediment rating curves, has proved to be valuable to generate SSC data for high and normal flows although it tends to underestimate the highest values. It can represent a useful tool for water resource managers who need a quick and inexpensive method, specific for temporary rivers, to evaluate suspended sediment yield.

Possible applications of ferrate(VI) in the treatment of industrial wastewater effluent in the laboratory

This paper shows the effects of ferrate(VI) application in the treatment of industrial wastewater effluent in laboratory conditions. Samples used are a mixture of wastewater effluent from various industrial plants whose composition was determined by analyzing samples before the ferrate(VI) treatment. Determining physical-chemical characteristics of the samples showed very high chemical oxygen demand (COD) and the concentrations of individual pollutants are higher than the maximum allowed. In the tested samples, the COD was from 18 (sample 1) to 580 times (sample 2) greater than allowed (allowed 45 - 150 mg/l), while the concentrations of certain metals were several times higher than allowed (Cu allowed 0,1 mg/l, Zn allowed 0,2 mg/l). Also, a high concentration of total phosphorus content (allowed 2 mg/l) and fluoride was found (allowed 20 mg/l), 2-3 times higher than permissible. The applied Na2FeO4 was synthesized by electrochemical method and applied in situ. Physical-chemical testing of samples, after treatment with different amounts (2, 5, 8, and 10 ml) of Na2FeO4, concentration of 8 g/l showed that ferrate(VI) can be used as a multifunctional agent in the purification of industrial wastewater, where in the amount of contaminating matter is reduced below the maximum permitted level. It was demonstrated the high efficiency of ferrate(VI) as a strong oxidant in the removal of total P and suspended materials. Also pointed out was the high sorption power of the generated ferric(III)hydroxide, which with its developed surface absorbs 95,5% of the F- and removes it from the solution in the form of sludge. Showed a high efficiency of ferrate(VI) in the total removal of P (70 to 99,5%), and F- (89 to 95,5%), but depending on the presence of the total COD value or the presence of the total organic substances. At high values of the COD major part of ferrate(VI) is consumed in the oxidation of organic material and the formation of Fe(OH)3, which accelerate the process of decomposition of ferrate(VI), which contributes to lower the efficiency of the removal of P and F-.

SEDIMENTATION RATES IN CACHOEIRA DE CIMA RESERVOIR, MOGI GUAÇU MUNICIPALITY, SP, BRAZIL

The aim of this study was to analyze the sedimentation rates of suspended material and to estimate the lifetime of the Cachoeira de Cima reservoir, in Mogi Guaçu municipality, Sao Paulo State. Sedimentation chambers were used to collect samples of suspended material. Sedimentation rates for total suspended material (TSM) ranged between 0.27 and 40.70 mg cm-2 d, for inorganic suspended material (ISM), between 0.05 and 34.19 mg cm-2 d, and organic suspended material (OSM), between 0.18 and 6.52 mg cm-2 d. Sedimentation rates of TMS, IMS and OMS at the Cachoeira de Cima reservoir are higher in the rainy season. The lifetime of the reservoir is estimated at 75 years.

Fog occurrence and chemical composition in the Po valley over the last twenty years

Frequency of fog events together with fog water chemical composition, pH, conductivity and liquid water content have systematically been measured from the end of the 1980's at the field station of San Pietro Capofiume, in the eastern Po Valley, Northern Italy. In agreement with what has been observed in other regions in Europe, fog frequency (visibility < 1 km) has decreased over the last three decades. Ionic strength and conductivity of fog samples also decreased over the period indicating a reduction of the ionic load of the droplets. Specifically, the three major inorganic ions (NH4+, SO42−, NO3−), accounting for 86% of the total fog water ionic strength, show a decreasing trend in concentration over the period, which can be linked to the decreasing trend of NH3, SO2 and NOx emissions registered in northern Italy over the same period. Sulphate exhibits the highest relative decrease (76%). Seasonal volume-weighted means of pH show an increasing trend over the observed period. The available data of total water-soluble organic matter concentrations indicate that organic compounds represent a considerable fraction (25% on average) of the total solute mass of fog water. Fog water samples often contain suspended insoluble particles, which were collected by filtering fog water through quartz fibre filters. EC-OC analysis performed on the filters collected over a four-year period, show that the sum of elemental carbon (EC) and water-insoluble organic mass accounts on average for 46%–56% of the total suspended material mass. Insoluble carbonaceous material is composed mainly of organic matter, with EC accounting on average only for 19% of the insoluble carbon.

Absorption-based algorithm of primary production for total and size-fractionated phytoplankton in coastal waters

Most satellite models of production have been designed and calibrated for use in the open ocean. Coastal waters are optically more complex, and the use of chlorophyll a (chl a) as a first-order predictor of primary production may lead to substantial errors due to significant quan- tities of coloured dissolved organic matter (CDOM) and total suspended material (TSM) within the first optical depth. We demonstrate the use of phytoplankton absorption as a proxy to estimate pri- mary production in the coastal waters of the North Sea and Western English Channel for both total, micro- and nano+pico-phytoplankton production. The method is implemented to extrapolate the absorption coefficient of phytoplankton and production at the sea surface to depth to give inte- grated fields of total and micro- and nano+pico-phytoplankton primary production using the peak in absorption coefficient at red wavelengths. The model is accurate to 8% in the Western English Channel and 22% in this region and the North Sea. By comparison, the accuracy of similar chl a based production models was >250%. The applicability of the method to autonomous optical sen- sors and remotely sensed aircraft data in both coastal and estuarine environments is discussed.

Diversity and distribution of &amp;lt;i&amp;gt;amoA&amp;lt;/i&amp;gt;-type nitrifying and &amp;lt;i&amp;gt;nirS&amp;lt;/i&amp;gt;-type denitrifying microbial communities in the Yangtze River estuary

Abstract. Coupled nitrification–denitrification plays a critical role in the removal of excess nitrogen, which is chiefly caused by humans, to mitigate estuary and coastal eutrophication. Despite its obvious importance, limited information about the relationships between nitrifying and denitrifying microbial communities in estuaries, and their controlling factors have been documented. We investigated the nitrifying and denitrifying microbial communities in the estuary of turbid subtropical Yangtze River (YRE), the largest river in Asia, by analyzing the ammonia monooxygenase gene amoA, including archaeal and bacterial amoA, and the dissimilatory nitrite reductase gene nirS using clone libraries and quantitative PCR (qPCR). The diversity indices and rarefaction analysis revealed a quite low diversity for both β-proteobacterial and archaeal amoA genes, but qPCR data showed significantly higher amoA gene copy numbers for archaea than β-proteobacteria. Compared with the amoA gene, a significantly higher level of diversity but lower gene copy numbers were found for the nirS gene. Nitrification and denitrification rates based on 15N incubation experiments supported gene abundance data as denitrification rates were below detection limit, suggesting lower denitrification than nitrification potential. In general, the abundances of the amoA and nirS genes were significantly higher in the bottom samples than the surface ones, and in the high-turbidity river mouth, were significantly higher in the particle-associated (&gt; 3 μm) than the free-living (0.2 ~ 3 μm) communities. Notably, positive correlations between the amoA and nirS gene abundances suggested potential gene-based coupling between nitrification and denitrification, especially for the particle-associated assemblages. Statistical analysis of correlations between the community structure, gene abundances and environmental variables further revealed that dissolved oxygen and total suspended material might be the key factors controlling community spatial structure and regulating nitrification and denitrification potentials in the YRE ecosystem.