River water

Bachmann et al.(1999) postulated that wind energy initiated, and has maintained, high turbidity in hypertrophic (mean chlorophyll a= 92 µg l-1) Lake Apopka, Florida (mean depth= 1.6 m; area= 12? 500 ha). They asserted that the turbid condition was initiated by a ...

Senegal river water has positive alkalinity (0.55 meq l À 1 ) and positive calcite-residual alkalinity (0.30 meq l À 1 ). Without leaching, this water presents a possible alkalinization and sodication hazard for the soil. The effect of flooding on soil solution chemistry in an irrigated nondrained vertisol under rice was monitored during 3 years in northern Senegal. During flooding, soil solution redox potential dropped to about À 0.15 V, and alkalinity increased to 15 meq l À 1 . Mg content increased as well, from about 1 to 5 meq l À 1 , whereas Cl and SO 4 contents decreased to very low levels at the end of the growing season (0.05 meq l À 1 ). After the fallow, nonflooded period between two crop cycles, the soil solution composition returned to its initial neutral sulfate and chloride composition. The observed cycle in soil solution chemistry could not be explained by water and solute transfer because infiltration rates were very low, due to air entrapment in the soil profile. Geochemical control by calcite and gypsum was excluded during irrigation. Mössbauer spectroscopy showed that iron oxides were both well-and poorly crystallized goethite. Goethite dissolution was assessed by pH -Eh stability diagrams.

A multi-class method for the simultaneous quantification and confirmation of 47 pharmaceuticals in environmental and wastewater samples has been developed. The target list of analytes included analgesic and anti-inflammatories, cholesterol lowering statin drugs and lipid regulators, antidepressants, antiulcer agents, psychiatric drugs, ansiolitics, cardiovasculars and a high number (26) of antibiotics from different chemical groups. A common pre-concentration step based on solid-phase extraction with Oasis HLB cartridges was applied, followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) measurement. All compounds were satisfactorily determined in just one single injection, with a chromatographic run time of only 10 min. The process efficiency (combination of the matrix effect and the extraction process recovery) for the 47 selected compounds was evaluated in nine effluent wastewater (EWW) samples, and the use of different isotope-labelled internal standards (ILIS) was investigated to correct unsatisfactory values. Up to 12 ILIS were evaluated in EWW and surface water (SW). As expected, the ILIS provided satisfactory correction for their own analytes. However, the use of these ILIS for the rest of pharmaceuticals was problematic in some cases. Despite this fact, the correction with analogues ILIS was found useful for most of analytes in EWW, while was not strictly required in the SW tested. The method was successfully validated in SW and EWW at low concentration levels, as expected for pharmaceuticals in these matrices (0.025, 0.1 and 0.5 g/L in SW; 0.1 and 0.5 g/L in EWW). With only a few exceptions, the instrumental limits of detection varied between 0.1 and 8 pg. The limits of quantification were estimated from sample chromatograms at the lowest spiked levels tested and normally were below 20 ng/L for SW and below 50 ng/L for EWW. The developed method was applied to the analysis of around forty water samples (river waters and effluent wastewaters) from the Spanish Mediterranean region. Almost all the pharmaceuticals selected in this work were detected, mainly in effluent wastewater. In both matrices, analgesics and anti-inflammatories, lipid regulators and quinolone antibiotics were the most detected groups.

The Aznalco´llar tailings dam at Boliden Apirsa's Aznalco´llar/Los Frailes Ag-Cu-Pb-Zn mine 45 km west of Seville, Spain, was breached on 25 April 1998, flooding approximately 4600 hectares of land along the Rı´os Agrio and Guadiamar with approximately 5.5 million m 3 of acidic water and 1.3Â10 6 m 3 of heavy metal-bearing tailings. Most of the deposited tailings and approximately 4.7Â10 6 m 3 of contaminated soils were removed to the Aznalco´llar open pit during clean-up work undertaken immediately after the spill until January 1999. Detailed geomorphological and geochemical surveys of the post-clean-up channel, floodplain and valley floor, and sediment and water sampling, were carried out in January and May 1999 at 6 reaches representative of the types of river channel and floodplain environments in the Rı´o Guadiamar catchment affected by the spill. The collected data show that the clean-up operations removed enough spill-deposited sediment to achieve pre-spill metal (Ag, As, Cd, Cu, Pb, Sb, Tl, Zn) concentrations in surface sediment. These concentrations, however, are still elevated above pre-mining concentrations, and emphasise that mining continues to contaminate the Agrio-Guadiamar river system. Dilution by relatively uncontaminated sediment appears to reduce metal concentrations downstream but increases in metal and As concentrations occur downstream, presumably as a result of factors such as sewage and agriculture. River water samples collected in May 1999 have significantly greater dissolved concentrations of metals and As than those from January 1999, probably due to greater sulphide oxidation from residual tailings with concomitant release of metals in the warmer early summer months. These concentrations are reduced downstream, probably by a combination of dilution and removal of metals by mineral precipitation. Single chemical extractions (de-ionised water, CaCl 2 0.01 mol l À1 , CH 3 COONH 4 1 M, CH 3 COONa 1 M and ammonium oxalate 0.2 M) on alluvial samples from reaches 1 and 6, the tailings, pre-spill alluvium and marl have shown that the order of sediment-borne contaminant mobility is generally Zn> Cd >Cu > Pb >As. Pb and As are relatively immobile except possibly under reducing conditions. Much of the highly contaminated sediment remaining in the floodplain and channel still contains a large proportion of tailings-related sulphide minerals which are potentially reactive and may continue to release contaminants to the Agrio-Guadiamar river system. Our work emphasises the need for pre-mining geomorphological and geochemical data, and an assessment of potential contributions of contaminants to river systems from other, non-mining sources. #

The retention of suspended particles transported by river flow on surfaces of freshwater plants is a potentially important process in the contamination of aquatic biota. Field experiments have been performed to test the role of Ž . benthic algae periphyton in trapping inorganic suspended solids transported by the river water and to discriminate between the caesium content of periphyton caused by the adherence of inorganic solids and by the active uptake inside the organisms. The contribution of caesium of suspended solids adhering to biotic surfaces was estimated by Ž . determining the scandium content scandium method . The scandium method was used because this element is geologically ubiquitous in soils and it is not taken up actively by plants and other organisms. The mass of suspended particles retained on the surfaces of microorganisms growing on submerged substrates were determined by comparing the scandium content of suspended material with that in algal communities. Neutron activation analysis was used as the analytical method for determination for both scandium, and caesium. The results indicate that the suspended particle fraction can contribute up to 80% of the caesium contamination of periphyton samples. Active caesium uptake and accumulation by aquatic biota represents the remaining 20% of the total caesium contamination. ᮊ

Since most of the water source on the earth surface is saline in nature, hydrogen generation from saline water is of great importance. In this paper, we have developed a membrane protected anode, using anionic backbone of sulfonated polystyrene-block-(ethylene-ran-butylene)-block-polystyrene polymer (S-PSEBS) over the anode (IrO2/Ti) which is capable of electrostatically repelling the chloride ions (Cl−) from the electrode surface and thereby enhancing the oxygen evolution rather than the chlorine evolution. The electrochemical behavior of both polymer modified and bare IrO2/Ti electrodes were characterized by electrochemical polarization studies and the gas evolution efficiencies were calculated. The surface morphology of the electrodes was investigated using scanning electron microscope (SEM). The results suggest that nearly 95% oxygen evolution efficiency could be achieved when the surface of IrO2/Ti electrode was modified with a permselective membrane.► The S-PSEBS coated electrode was found to be more effective for oxygen evolution reaction in saline water electrolysis. ► The maximum oxygen evolution efficiency of 95% was achieved. ► The results proved that hydrogen can be generated from the earth abundant saline water.

The sensitive multiresidual analytical method for simultaneous analysis of 14 most commonly used agricultural pesticides in Serbia was developed and optimized. The selected insecticides, fungicides and herbicides belong to seven chemical classes (organophosphates, neonicotinoids, carbamates, diacylhydrazines, benzimidazoles, triazines and phenylureas). The method was based on solid-phase extraction followed by liquid chromatography-tandem mass spectrometry. The following parameters that may affect the SPE procedure efficiency were optimized: the sorbent type in combination with different elution solvents, the sample pH and the sample volume. For each pesticide, MS n analysis was performed and distinctive ions and transitions were selected for identification and quantification, as well as for confirmation purposes. External matrix-matched calibration method was used to eliminate variable matrix effect and ensure precise quantification. Good recoveries (72-129%), and low limits of detection (0.4-5.5 ng L −1 ) and quantification (1.1-18.2 ng L −1 ) were achieved for all selected pesticides. The developed and optimized method was successfully applied in the analysis of several river waters, as well as ground waters in Serbia, influenced by agriculture. The most frequently detected pesticide was carbendazim. Dimethoate, carbofuran and propazine were also found in the investigated samples.