Evaluation of centrifugal ultrafilters for size fractionation of total mercury and methylmercury in freshwaters

2013 ◽  
Vol 10 (4) ◽  
pp. 323 ◽  
Author(s):  
David Kocman ◽  
Scott C. Brooks ◽  
Carrie L. Miller ◽  
Xiangping L. Yin

Environmental context Although mercury associated with colloids is an important part of the aquatic Hg cycle, there is currently no fast and reliable method to separate complexes smaller than traditional filter pore sizes. We test commercially available centrifugal ultrafilters for their applicability to size fractionation of total Hg and methylmercury in freshwaters. Sorption of Hg onto the filters precludes their use for fractionation of inorganic Hg, the approach proved to be very suitable for methylmercury fractionation regardless of sample organic matter content. Abstract Amicon Ultra-15 centrifugal filters with nominal molecular weight cut-offs of 100, 30 and 3kDa, were tested for separating Hg complexes in freshwaters. Experiments used Hg-contaminated water from East Fork Poplar Creek (EFPC) and laboratory-prepared Hg solutions containing Suwannee River natural organic matter (SR-NOM). Investigations focussed on Hg and dissolved organic carbon blank levels, Hg sorption and leaching, Hg mass balance closure and spike recoveries of inorganic and methylmercury (MeHg). Hg spike recoveries for EFPC samples were low (57±16%, n=30) due to sorption. MeHg recovery averaged 87±9% (n=15) suggesting it was less affected by sorptive losses. SR-NOM samples yielded similar dissolved organic matter (DOM) and MeHg size fractionation patterns with ~20% of the MeHg found in the less than 3-kDa fraction. Overall, the distribution of MeHg followed a pattern similar to the DOM, indicating the importance of both sample DOM quantity and quality for MeHg partitioning in aquatic systems. Although the use of these ultrafilters for inorganic Hg in freshwater samples is not recommended, they were successfully used for MeHg in EFPC where the majority of MeHg was found to be either dissolved or associated with phases smaller than 3kDa.

2014 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Eny Heriani R.N. ◽  
Wasinton Simanjuntak ◽  
Ilim .

This study was carried out to investigate treatment of brackish water using a combination of electrocoagulation and adsorption using carbosil prepared from rice husk with pyrolysis method. Electrocoagulation was applied with the aim to remove natural organic matter in the sample, using aluminim as electrodes, with the particular purpose to study the effect of potenstials.For this purpose, electrocoagulation experiments were conducted at potential of 4, 6, and 8 volt at fixed contact time of 60 minutes.The performance of the method was defined in term of absorbance reduction at the wavelengths of 254 and 285 nm, since the absorbance at these two wavelenghts was found to correlate well with the amount of organic matter in the water samples. The treated water was then subjected to adsorption process at different contac times of 5. 10, and 15 minutes, and the performance of the process was evaluated in term of electrical conductivity reduction.The results obtained indicate that for electrocoagulation process, the higest reduction of natural organic matter content was achieved using potential of 8 volt, and adsorption porcess of 15 minutes was found to result in reduction of electrical conductivity from 15.13 mS/cm to 10.10 mS/cm.Characterization of the carbosil using SEM/EDX technique revealed that the carbosil has practically homogeneous surface and able to adsorb salt and several other elements from the brackish water. Key words : adsorption, brackish water, carbosil, electrocoagulation


2009 ◽  
Vol 9 (2) ◽  
pp. 173-180 ◽  
Author(s):  
I. García ◽  
L. Moreno

Filtration with granular activated carbon (GAC) after an enhanced coagulation (EC) process was evaluated in order to determine the effectiveness of GAC in the reduction of natural organic matter (NOM), which should result in much lower formation of trihalomethane in the disinfection step. The results show that a combination of EC and GAC considerably reduces the organic matter content, which is mainly fulvic acid. This type of organic matter is removed with high coagulant dosages which neutralize their high anionic charge. A further reduction of NOM is achieved due the adsorption of NOM by GAC. As a result, the average trihalomethane (THM) concentration was only 14.5±5 μg L−1. Enhanced coagulation alone decreased the NOM concentration by 50%, but the remaining NOM reacted in the chlorination step and a higher average THM concentration was found (38±23 μg L−1). An average THM concentration of 73.8±41.2 μg L−1 was found at the drinking water plant of Boaco when conventional treatment was used. This THM concentration sometimes exceeds the maximum contaminant level of 80 μg L−1 established by the United States Environmental Protection Agency (USEPA), but not the Nicaraguan threshold of 460 μg L−1.


2018 ◽  
Vol 28 (3) ◽  
pp. 17-29
Author(s):  
Izabela Krupińska

Abstract The article discusses effectiveness of treatment of groundwater with increased natural organic matter content with the use of organic polyelectrolytes. The effects of water treatments were determined by the ionic character of the polyelectrolyte and its dose. Due to the amount of removed general ferric and coloured matters a greater usefulness of anionic and non-ionic polyelectrolytes was shown, while due to decreased turbidity and TOC, cationic flocculants proved more useful. Using the Praestol 2540 semi-anionic polyelectrolyte as the substance aiding the coagulation process decreased the effectiveness of groundwater treatment, especially in terms of the removal of iron and organic substances when using the PIX-112 coagulating agent.


Author(s):  
O. A. Lipatnikova

The study of heavy metal speciation in bottom sediments of the Vyshnevolotsky water reservoir is presented in this paper. Sequential selective procedure was used to determine the heavy metal speciation in bottom sediments and thermodynamic calculation — to determine ones in interstitial water. It has been shown that Mn are mainly presented in exchangeable and carbonate forms; for Fe, Zn, Pb и Co the forms are related to iron and manganese hydroxides is played an important role; and Cu and Ni are mainly associated with organic matter. In interstitial waters the main forms of heavy metal speciation are free ions for Zn, Ni, Co and Cd, carbonate complexes for Pb, fulvate complexes for Cu. Effects of particle size and organic matter content in sediments on distribution of mobile and potentially mobile forms of toxic elements have been revealed.


Author(s):  
Amita M Watkar ◽  

Soil, itself means Soul of Infinite Life. Soil is the naturally occurring unconsolidated or loose covering on the earth’s surface. Physical properties depend upon the amount, size, shape, arrangement, and mineral composition of soil particles. It also depends on the organic matter content and pore spaces. Chemical properties depend on the Inorganic and organic matter present in the soil. Soils are the essential components of the environment and foundation resources for nearly all types of land use, besides being the most important component of sustainable agriculture. Therefore, assessment of soil quality and its direction of change with time is an ideal and primary indicator of sustainable agricultural land management. Soil quality indicators refer to measurable soil attributes that influence the capacity of a soil to function, within the limits imposed by the ecosystem, to preserve biological productivity and environmental quality and promote plant, animal and human health. The present study is to assess these soil attributes such as physical and chemical properties season-wise.


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