Physico-chemical Characteristics Of Water Research Articles

Evaluation of Physicochemical Characteristics of Water and Soil Samples from Cassava Processing Mill in Parts of Edo North, Edo State, Nigeria

The problem of contaminated water sources and soil pollution has persisted in the study area emanating from cassava effluents from the processing of cassava in the study area. Physicochemical analysis was carried out in water and soil samples obtained in and around cassava processing mill in the Environment where cassava is been process to determine areas prone to contamination by taking soil and water samples in the various study location at a depth of 1.2 m for soil samples and 10 m for water samples in a hand dug well. The result from the physicochemical analysis of the Soil and water samples shows traces of heavy metals when compared with the standard set by World Health Organization (WHO). It is evident that in some sites investigated, the water and soil has been polluted by the discharge from the cassava effluent. The research thus point out the need for environmental Education and proper management/location of cassava processing sites in the study area by relevant Agencies.

Industrial waste as a source of surface and groundwater pollution for more than half a century in a sector of the Río de la Plata coastal plain (Argentina)

Environmental liabilities have become one of the most important problems of the last years, especially those of contaminated sites located in urban areas which have been abandoned by pollution intensive industries. Such sites may contain hazardous materials that pose risks to human health and the environment. Industrial waste from the ancient sulfuric acid industry is scattered in a local area at the petrochemical pole in a sector of the Río de la Plata coastal plain. The aim of this work is to define the geochemical processes that determine the alteration of waste in the old sulfuric acid industry (OSAI) area and to study the migration of soluble pollutants to groundwater. A survey of soil and waste deposit was carried out and samples were examined by X-ray diffraction, under a scanning electron microscope and a polarizing microscope. Surface water and groundwater samples, both to the unconfined and semi-confined aquifers, were collected to determine electrical conductivity, pH and major elements. The results show the presence of minerals composed of sulfur associated with jarosite and iron oxides on superficial sediments. The detailed study of soil sediments together with that of the water physicochemical characteristics make it possible to understand the geochemical processes developed in soil that cause the high concentrations of sulfates in groundwater. Furthermore, high SO4−2 concentration registered in the semi-confined aquifer due to its infiltration from the unconfined aquifer shows that the industrial pollution has an important impact at local level. These results may contribute to the understanding of chemical processes and pollutants distribution in highly industrialized coastal plain areas.

Microbial and chemical characterization of commercial washing lines of fresh produce highlights the need for process water control

Abstract Process wash water and washed products from three different fresh produce processing lines were characterized at commercial scale. Different physicochemical and microbiological characteristics of wash water were measured. Great variability between processing lines on the physicochemical quality of process wash water was observed, caused in part by the type of produce washed. The relationship between lower aerobic mesophilic bacteria and higher free chlorine (FC) concentrations in wash water was detected (Pearson's correlation coefficient (PCC) = −0.53). Independently of the FC concentration, most of the water samples (>80%) showed presence of cultivable (limit of detection 1 CFU/100 mL), probably caused by the uncontrolled pH conditions. Higher values of FC and oxidation-reduction potential (ORP) in wash water were related to lower microbial load in washed produce (PCC = −0.82, and − 0.79, respectively). Higher concentration of chlorine was linked to a higher presence of disinfection by-products (DBPs) in the wash water, and washing in chlorinated water led to a significant increase in the concentration of DBPs in produce. However, the accumulation of trihalomethanes (THMs) in process wash water was not correlated with higher concentrations of these DBPs in produce. Industrial relevance The washing step of fresh produce processing lines is a critical process. The dose of disinfectants needs to be adequately optimized to avoid microbial contamination without generating the accumulation of disinfection by-products (DBPs). In this study, critical parameters that influence the efficacy of water disinfection and the occurrence of DBPs in fresh produce processing lines were identified under commercial conditions. The results evidenced that monitoring and control of pH play a critical role by maximizing the concentration of the most active form of chlorine in the water. The parameter UV254 measured on-line in the washing tank, can be suggested as a suitable indicator of the presence of organic matter in fresh produce wash water.

A preliminary survey of water physico-chemical characteristics and aquatic macroinvertebrate communities in El Mekhada marsh, north-eastern Algeria

The water physico-chemistry and aquatic macroinvertebrates were investigated for the first time in El Mekhada marsh, Algeria. The aim of this study was to assess the general ecological condition of the marsh by studying the spatial and seasonal variation of physico-chemical parameters and macroinvertebrate communities. Sampling was conducted at four sites surrounding the marsh, in wet and dry seasons from February to September 2016. Physico-chemical characteristics were similar among sampling sites and seasons (p > 0.05), except for water temperature, which showed significantly higher values in the wet period than in the dry period (p < 0.05). A total of 1066 macroinvertebrate individuals belonging to 43 taxa were collected. Macroinvertebrate descriptors revealed no significant variation across the marsh (p > 0.05), and only taxa abundance was significantly higher in the wet season than in the dry season (p < 0.05). NMDS reflected the previously detected variation and showed a clear separation in macroinvertebrate assemblages between seasons. The SIMPER analysis revealed that the mean abundance of most taxa was lower in the dry season. This study highlights that the studied marsh is taxonomically rich (34 families); therefore, its conservation and protection is necessary.

Comparative water quality assessment between a young and a stabilized hydroelectric reservoir in Aliakmon River, Greece

In this work, a comparative study on the water quality characteristics of two in-line water reservoirs (artificial lakes) in Aliakmon River (Western Macedonia, Greece) is performed. Polyfytos Reservoir and Ilarion Reservoir were created in 1975 and 2012 respectively, in order to serve the homonymous hydroelectric stations. In young artificial lakes, severe deterioration of water quality may occur; thus, the monitoring and assessment of their water quality characteristics and their statistical interpretation are of great importance. In order to evaluate any temporal or spatial variations and to characterize water quality of these two in-line water reservoirs, water quality data from measurements conducted from 2012 to 2015 were statistically processed and interpreted by using a modified National Sanitation Foundation water quality index (WQI). The water physicochemical characteristics of the two reservoirs were found to be generally within the legislation limits, with relatively small temporal and spatial variations. Although Polyfytos Reservoir showed no significant deviations of its water quality, Ilarion Reservoir exhibited deviations in total Kjeldahl nitrogen, nitrite nitrogen, total suspended solids, and turbidity due to the inundated vegetation decomposition. The conducted measurements and the use of the modified NSFWQI revealed that during the inundation period of Ilarion Reservoir, its water quality was "moderate" and that the deviations were softened through time, leading to "good" water quality during its maturation period. Three years since the creation of Ilarion Reservoir, water quality does not match that of Aliakmon River (feeding water) or that of the stabilized reservoir (Polyfytos Reservoir), whose quality is characterized as "high." The use of a WQI, such as the proposed modified NSFWQI, for evaluating water quality of each sampling site and of an entire water system proved to be a rapid and relatively accurate assessment tool.

The effect of magnetic treatment on the physico-chemical and microbiological characteristics of hard waters

ABSTRACTThe main objective of this study was to investigate the effect of magnetic treatment on the physico-chemical and bacteriological characteristics of hard waters. The scaling power of tested waters was evaluated using the rapid controlled precipitation (RCP) method. Results showed that magnetic treatment affects calcium carbonate crystallization. The RCP tests confirmed that the scaling power of the magnetically treated water was inhibited. Experimental results also indicated a significant improvement in the bacteriological quality of the treated water. Average reductions of 2.02 log Total coliforms, 0.95 log Escherichia coli and 1.06 log Faecal streptococci were obtained.

Influence of land cover on riverine dissolved organic carbon concentrations and export in the Three Rivers Headwater Region of the Qinghai-Tibetan Plateau

The Qinghai-Tibetan plateau (QTP) stores a large amount of soil organic carbon and is the headwater region for several large rivers in Asia. Therefore, it is important to understand the influence of environmental factors on river water quality and the dissolved organic carbon (DOC) export in this region. We examined the water physico-chemical characteristics, DOC concentrations and export rates of 7 rivers under typical land cover types in the Three Rivers Headwater Region during August 2016. The results showed that the highest DOC concentrations were recorded in the rivers within the catchment of alpine wet meadow and meadow. These same rivers had the lowest total suspended solids (TSS) concentrations. The rivers within steppe and desert had the lowest DOC concentrations and highest TSS concentrations. The discharge rates and catchment areas were negatively correlated with DOC concentrations. The SUVA254 values were significantly negatively correlated with DOC concentrations. The results suggest that the vegetation degradation, which may represent permafrost degradation, can lead to a decrease in DOC concentration, but increasing DOC export and soil erosion. In addition, some of the exported DOC will rapidly decompose in the river, and therefore affect the regional carbon cycle, as well as the water quality in the source water of many large Asian rivers.

Investigations on groundwater quality in Tiruchirappalli city, Tamilnadu, India

Monitoring of stream water physico-chemical characteristics and heavy metal concentration is necessary to establish the levels of contamination in wastewater. With increasing urbanization and industrialization, there has been a rapid increase in industrial effluent discharge into the water bodies, leading to increased pollution load. Groundwater quality in Tiruchirappalli City, Tamilnadu, India, was studied and major dissolved constituents including heavy metals of concern such as chloride, fluoride, nitrate, nickel, copper and iron have been documented in this paper. Thus, this study helps to determine the groundwater potential and aquifer characteristics of the study area.

Phyto-Ecological Assessment of Mahakali River, Far-western Nepal

An assessment of phyto-ecology and socio-economy of wetlands of Mahakali River system of far-western Nepal was carried through rapid ecological assessments, participatory discussions, transects and quadrat studies, and laboratory analyses to reveal the interactions between physico-chemical characteristics of water and soil, biodiversity and socio-economic regimes. Mahakali river system was flanked by a number of tributaries, steep cliffs, rocks, and was closely associated with riverine and mixed Shorea robusta (Sal) forests, resulting in richness and diversity of habitats and plant species. Vegetation succession was found to conspicuous as transcends farther from river edge, the Phragmites karka was gradually succeeded by Saccharum spontaneum and riverine forest species such as Acacia catechu, Dalbergia sissoo, Bombax ceiba, Eugenia jambolina, Aegle marmelos, etc. A total 140 plant species including 78 ethnomedicinal were inventoried, representing about 27 percent of the district flora. This study serves as a baseline data of phyto-ecological attributes of Mahakali River and can be taken as a reference to investigate the temporal changes in Mahakali River system. J. Nat. Hist. Mus. Vol. 29, 2015, Page: 32-48

Physicochemical Parameters and Planktonic Species as Indicators to Assess Water Quality of River Basin and Winam (Nyanza) Gulf of Lake Victoria Catchment, Kisumu County, Kenya (East Africa)

Presence (+) or absence (-) of planktonic species is the direct indication of differences in physicochemical characteristics of water because all living microorganisms appear, survive, develop and multiply in suitable specific habitats within an aquatic ecosystem. Planktonic species as indicators with relation to physicochemical parameters were studied to assess water quality of ten selected (S1-S10) sampling stations along Nyalenda swamp (S1), River Kisat (S2-S5) and part of Winam (Nyanza) Gulf (S6-S10) within Lake Victoria Catchment in Kisumu County, Kenya (East Africa). There are 14 genera (Amphora, Aulacoseira, Closterium, Cyclotella, Cymbella, Diatoma, Fragillaria, Gomphocymbella, Navicula, Nitzschia, Pinnularia, Stephomodiscus, Surillela and Synedra) composed of 28 planktonic species. During the field study, Genus Nitzschia is represented by its five species but only four species N. lucastris; N. palea; N. recta and N. sub-acicularis together with other three genus and four species which are Cymbella cistula; Cymbella sp; Diatoma hiemiale; Navicula granatum are present with 100% frequency in all the ten sampling stations (S1-S10) and very well adapted within wide range of pH, dissolved oxygen, conductivity, turbidity, alkalinity, total nitrogen and phosphorus levels. Six species belong to five genera: Aulacoseira ambigua; Aulacoseira nyassensis; Cyclotella kutzinghiana; Diatoma elongatum; Navicula sp; and Surilella ovalis appeared with 80% frequency. There are six genera: Amphora, Cyclotella, Cymbella, Fragillaria, Navicula and Synedra represented by two species each, while other five genera including Closterium, Gomphocymbella, Pinnularia, Stephomodiscus and Surillela are represented with one single species each. There are two species of genus Amphora but only one Amphora sp appeared with 70% frequency. Three planktonic species: Nitzschia dessipata, Synedra cunningtonii, and Synedra ulna are with 60% frequency; three species: Amphora ovalis; Fragilaria aethiopica; and Stephomodiscus astraca appear with 50% frequency; two species: Aulacoseira schroidera and Cyclotella ocellata are with 30% frequency; and three species: Closterium aciculare, Diatoma valgare, and Pinnularia viridis appeared with 20% frequency and lastly, other two remaining species: Fragillaria longissimi and Gomphocymbella beccari are present only in sampling station (S5) with 10% frequency. Each planktonic species is an indicator species of its own low or high levels of physicochemical parameters. Study revealed that mean monthly values of physicochemical levels of pH, dissolved oxygen, alkalinity and silicate show significant difference (p=0.001 ≤ 0.05) but electrical conductivity (381.25 μS/cm to 839.65 μS/cm), turbidity (32.37 NTU to 134.98 NTU), total nitrogen (388.56 μg/l to 908.88 μg/l), phosphorus (329.21 μg/l to 1246.38 μg/l) levels are higher than permissible standards of WHO, EU, KEBS and NEMA. Based on these results, these water bodies are polluted and not good source for drinking water. It is recommended that planktonic species should be used in the field as quick bio-indicator(s) to assess the water quality of any global aquatic ecosystem(s).

The Benthic Fauna and Water Physicochemical Characteristics in the Estuarine Ecosystem of the Mouth of Moulouya River (Morocco)

The Benthic Fauna and Water Physicochemical Characteristics in the Estuarine Ecosystem of the Mouth of Moulouya River (Morocco)

Trophic Status of the Dniester Delta Lakes in 2006-2017

Purpose. Assessment of trophic status of the Dniester deltaic part lakes (Bile, Svine, Tudorovo and Putrino) in 2006-2017. Methods. Determination of hydrological, hydrochemical and hydrobiological characteristics of the lakes aquatic environment has been performed using standard methodologies. Three indicators of eutrophication have been used: chlorophyll a concentration, number of bacterioplankton, trophic indices TSI and TRIX. Results. Peculiarities of physicochemical characteristics of water in the Dniester deltaic lakes have been analysed. Increased nutrients concentration has been revealed in all the lakes during past 12 years. The lowest oxygen content and oxygen saturation was established in water of the Putrino Lake, where at the same time the highest concentrations of total nitrogen and phosphorus were observed. Analysis of long-term changes of chlorophyll a and bacterioplankton has been done. Based on the lakes integrated study in summer time of 2006-2017, assessment of water trophic state has been for the first time performed for each deltaic lake. Statistical interrelations between trophic state indicators and physicochemical characteristics of the lakes have been revealed. Conclusions. It was established that the assessment of four deltaic lakes trophic status based on chlorophyll a, bacterioplankton and TSI trophic index practically coincided and evidenced increased of the lakes’ trophic status and decrease of water quality in 2012-2017 compared with previous years. All the eutrophication indicators in water of the lakes Svine, Tudorovo and Putrino during six last years corresponded to hypertrophic status, while in the Bile Lake most of eutrophication indicators were lower and corresponded to eutrophic status. Trophic index TRIX, which was developed for seawater assessment, practically always showed somewhat higher trophic status of the lakes than other indicators.

Study of Changes of Trophic Status of the Kuchurganske Reservoir in 2006-2018

Purpose. Assessment of the trophic status of water in the Kuchurganske Reservoir in 2006-2018. Methods. Determination of hydrological, hydrochemical and hydrobiological characteristics of the water body's environment has been done using standard methodologies. Four indicators of water eutrophication have been used: chlorophyll a concentration, bacterioplankton number, trophic indices TSI and TRIX. Results. Features of physicochemical characteristics of water in the water-body have been analysed. Higher water temperature has been registered in the middle and lower parts of the water-body compared with its upper reaches. Mineral content increase in water has been found in the direction from lower to upper part; the critical for hydrobionts life decrease of oxygen concentration has been registered in the upper reaches the most often. Analysis of long-term changes in chlorophyll a and bacterioplankton has been carried out. Statistical interconnections have been established between trophic state indicators and physicochemical characteristics of the reservoir. A close positive correlation has been registered between chlorophyll а content and bacterioplankton number, which is caused by the functional dependence of bacteria on the organic matter produced by phytoplankton. It has been shown that with an increase of water volume in the reservoir the value of these indicators of trophic status went down, which was proved by close negative correlation dependence between those values and the depth of water-body. It was demonstrated for the first time that water transparency revealed close significant negative correlation with all the indices and indicators of water trophic status, which evidenced the possibility to use the transparency as a simple indicator of water trophic state as established that the Kuchurganske Reservoir’s trophic status assessment on chlorophyll a, bacterioplankton and the TSI trophic index practically coincided and evidenced the increase in trophic status of the water-body from eutrophic to hypertrophic in last 2016-2018. The reservoir’s upper reaches were characterized by higher water trophicity compared with the central and lower parts. The values of TRIX trophic index developed for marine water assessment had practically always been showing higher trophic status compared to other indicators.

POLLUTION SOURCES IN WATER OF YOUNG RESERVOIRS - CASE OF ILARION HYDROELECTRIC DAM, GREECE

Evaluation of spatial/ temporal water quality data at reservoirs has shown differences after the dam construction as well as longterm changes of water chemistry. One of the most recent reservoirs created in Europe is Ilarion Reservoir in Western Macedonia Greece (2012). In this work, the water physicochemical characteristics of this young reservoir and the spatiotemporal water quality variation of the feeding river and its main tributaries have been studied, and statistically interpreted. The aqueous system of the young reservoir after two years of formation does not seem to have reached its stabilization age but a stabilization tendency appears at some quality parameters. The dissolution of plant residues covering the flooded areas and the water volume changes affected the water quality, while excesses of legislation s limits for some parameters have been observed. The most affected parameters, remaining at high levels are TKN, ammonia, nitrite nitrogen and color. The feed water quality is generally within the legislation s limits with the exception of nitrite and ammonium nitrogen parameters which exceed the maximum permissible legislation s limits and are the main pollution sources of the young reservoir. Monitoring these parameters is necessary to determine if the observed excess values could lead to eutrophic conditions and toxic habitat for fishes. The statistical analysis indicated some significant parameters responsible for large variations in water quality and allowed the identification and apportionment of pollution sources as an aspect of the temporal/spatial variations in water quality, indispensable for effective water quality management.

Effect of Depth and Distance of the Borehole from the Septic Tank on the Physico-Chemical Quality of Water

A study to examine the effect of depth and distance of the boreholes from the septic tank on physico-chemical parameters of the borehole water consumed in Dar Es Salaam, Tanzania was conducted. Samples were collected from 48 boreholes in Ilala, Kinondoni and Temeke districts and subjected to pH, B.O.D (Biological Oxygen Demand), total hardness, copper and lead analyses in relation to safety and quality levels set by WHO and TBS. Analysis by R-statistics indicated that pH and B.O.D significantly (p&lt;0.05) decreased as the depth of borehole increased, whereas total hardness was significantly (p&lt;0.05) higher in very deep boreholes than the other heights. Total hardness and pH were not significantly (p&gt;0.05) affected by distance between septic tank and borehole and the B.O.D levels were significantly higher in the borehole water situated near the septic tank than those which were far. Based on the physico-chemical characteristics of water, 25% of the samples did not comply with WHO and TBS specification limits while 75% complied, most of which had shallow depths and were situated near the septic tank. It may thus be concluded that both the distance and the depth between septic tank and borehole influenced physico-chemical characteristics of water.

Towards developing a river health index

A number of physical, chemical and biological water quality parameters are measured to understand quality conditions of a riverine environment. Various aggregation techniques have been used to reflect the combined effect of the existing or proposed quality levels. Water Quality Index (WQI) has been developed primarily for fresh water environments. Organic pollutants are not considered in many WQIs because analyses of organics are rather expensive. In general, fecal coliform and total coliform counts are measured to reflect biological contamination of water. With growing consensus on considering rivers as ecological entity, rather than merely a source of water for human consumptions, the emphasis is changing from water quality index (WQI) to River Health Index (RHI). As benthic macroinvertebrate species are differentially sensitive to many biotic and abiotic factors in river environment, macroinvertebrate community structure has commonly been used as indicator of stream water condition. A number of river health assessment methodologies have been proposed in past and several indices such as Ecological Health Index (EHI), Ecological Quality Index (EQI), Overall Index of Pollution (OIP) and River Pollution Index (RPI) have been developed using water quality variables and aquatic species for evaluating the ecological health of river systems. This paper attempts to review and summarize some of these indices with particular emphasis on measurable parameters included in such formulations. The analyses suggest that with sufficient scientific experience and understanding in this area, it is possible to define a River Health Index (RHI) by including algae, macroinvertebrates and fish species as measurable parameters along with routine physico-chemical characteristics of river water. One such formulation on RHI has been proposed by the authors in this paper. The novelty of the proposed formulation include simple calculations and presentation of RHI value on 0–100 scale. The biological indices used in ACEDP (2011) requires biological expertise which is not normally available with water resource managers. Hence species identification and counting based simple biotic indices have been proposed so that it can be easily done by non experts also. River Health Level (RHL) can be categorized as ‘critical’ or ‘excellent’ based on RHI value <=20 or >80. Thus RHI values can be used to identify the healthy or unhealthy stretches of the river. RHI can serve as scientific tool to assess the current status, need and effectiveness of any intervention required to improve the condition of the river. Application of this RHI formulation on main stream of river Ganga (India) is under study.

Biogeochemical diversity, O2-supersaturation and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil

Nhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, >15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. From 4 selected alkaline lakes, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm a difference between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning. This difference does not appear to affect lake sedimentation rates, but is reflected in gas emissions. Black-water lakes are CO2 and CH4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 0.86molm−2y−1 and 0.07molm−2y−1, respectively, and no clear trend towards N2O capture or emission was observed. By contrast, green-water lakes are CO2 and N2O sinks but important CH4 sources with fluxes varying significantly throughout the seasons, depending on the magnitude of the phytoplankton bloom. The results highlight important daily and seasonal variations in gas fluxes, and in particular a hot moments for methane emissions, when the O2-supersaturation is reached during the afternoon under extreme bloom and sunny weather conditions, provoking an abrupt O2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 10.2molm−2y−1, i.e., much higher than reported in previous studies for alkaline lakes in Nhecolândia. Carbon dioxide and nitrous oxide consumption is estimated about 1.9molm−2y−1 and 0.73mmolm−2y−1, respectively. However, these balances must be better constrained with systematic and targeted measurements throughout the seasons.

Contribution of the geographic information system for groundwater to the mapping of subterranean waters in the region Djelfa (Algeria)

The Djelfa region characterized by a semi-arid climate. The quality of groundwater is among the problems that are becoming increasing concern in the region. The physico-chemical characteristics of water are severely affected by high salinity of them. This research is devoted to the use of geographic information systems GIS, for drawing maps of the main parameters that can reveal the spatial variation of physical and chemical characteristics of water to achieve a good estimate of its quality. Mapping is the first step in the creation of geographic information systems. The aim of our work is to present a tool for decision making that can establish useful maps to study the water quality of the Djelfa region.

Physico-chemical water characteristics and aquatic macroinvertebrates of Lake Tsimanampesotse, south-western Madagascar

Saline lakes are known to be amongst the most productive ecosystems in the world. Tsimanampesotse, a ‘conservation hotspot’ soda lake in southwestern Madagascar, was integrated into the Ramsar wetland network in 1998. Despite its importance for aquatic birds, knowledge of its water characteristics and aquatic biota is scarce. Water quality and aquatic invertebrates were investigated in April and August 2013 to provide baseline data in order to measure possible changes of the area in the future. Changes in water temperature (19.5–25.9 °C) and in dissolved oxygen (9.3–11.3 mg l−1) were detected. The water was highly mineralised (EC > 41 000 µS cm−1) and moderately alkaline (pH ∼ 8.0). The maximum concentrations of ammonia and phosphate were relatively high (39.1 and 57.6 mg l−1, respectively). Freshwater runoff from the plateau makes the water quality in the eastern part of the lake better than that in the west. Of the 15 taxa of macroinvertebrate assessed, the crustaceans Grandidierella mahafalensis and Apseudes thaumastocheles were dominant. Decreased water salinity in April increased the abundance and diversity of macroinvertebrates. Despite its incorporation to the protected area, Lake Tsimanampesotse is still impacted by human activities and needs supplementary preservation.

Cadmium, mercury, and nickel adsorption by tetravalent manganese feroxyhyte: selectivity, kinetic modeling, and thermodynamic study.

This study is aiming to investigate tetravalent manganese feroxyhyte (TMFx) adsorption efficiency in removing heavy metals. The motivation of this study was the fact that TMFx is a highly negatively charged nanostructure material and that the metals Cd, Hg, and Ni were characterized as priority pollutants for drinking water. TMFx was evaluated through batch and continuous flow experiments in National Sanitation Foundation (NSF) water matrix which simulated the physicochemical characteristics of natural water. Water's pH significantly influences Cd and Ni adsorption efficiency which gradually increases when pH value rises from 5 to 9, while the corresponding one for Hg remains almost constant. Thermodynamic data showed a spontaneous and an exothermic nature weak-chemisorption (ΔΗ°=-17.5±2kJ/mol) of Cd, Ni, and Hg by TMFx. The determined ranking of adsorption affinity and selectivity (Cd > Ni > Hg) seems to be governed by the metals' speciation, as well as by hydration free energy, which is influenced, however, by their atomic radius. The lower adsorption capacity and selectivity of TMFx for Hg should be attributed both to uncharged species and to higher atomic radius. The similar Cd and Ni speciation in the NSF water matrix leads to the conclusion that the better affinity, selectivity, and adsorption kinetic of Cd versus Ni should be attributed to the lower hydration free energy of Cd which is in turn related to its higher atomic radius. The faster adsorption kinetic (Hg > Cd > Ni) of Hg may be attributed to the lower radius of its anhydrate species. Furthermore, TMFx showed high removal efficiency under continuous flow application in an adsorption bed setup. The determined uptake capacity (q RL) at equilibrium-breakthrough concentration equal to the drinking water regulation limit (RL) of each metal were q 1=2.5μg Hg/mg TMFx, q 5=5.2μg Cd/mg TMFx, and q 20=7.1μg Ni/mg TMFx. Leaching tests of spent TMFx samples from the rapid small-scale column tests (RSSCTs) could be treated either as inert wastes after Cd and Ni adsorption or as non-hazardous waste after Hg adsorption.