Dynamics of arsenic-containing compounds sorption on sediments

• Published in: Journal of soils and sediments 2004-06, Vol.4 (2), p.95-100
• Main Authors: Reczynski, Witold, Posmyk, Grzegorz, Nowak, Katarzyna
• Format: Article
• Language: English
• Subjects: Aluminium; Aluminum; Aquatic environment; Arsenic; Arsenic compounds; Chemical composition; Dimethylarsinic acid; Drinking water; Dynamics; Equilibrium; Fluvial sediments; Inland waters; Iron; Lake deposits; Lake sediments; Lakes; Manganese; Methods; Mineral composition; Organic matter; pH effects; Reservoirs; Rivers; Sediment; Sediment samplers; Sediment samples; Sediments; Sorption; Speciation; Suburban areas; Suspension; Water pollution
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/BF02991052

BackgroundRiver and lake sediments constitute complex and difficult analytical samples. On the other hand, sediments play a fundamental role in the distribution of toxic compounds in aquatic systems and in the evaluation of the current state and the course of changes taking place in the environment.Among elements present in the environment in trace concentrations, but having well-elaborated toxic properties, one of most dangerous is arsenic. The element occurs in the environment in several chemical forms, predominant are inorganic forms of As(V) and As(III), and methylated forms such as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA).ObjectivesReported herein are experiments, which were undertaken with the aim of examining the dynamics of arsenic sorption in sediments and its dependence on speciation of the element and the pH in the environment. Simultaneously, influence of organic matter content and chemical composition of the sediments on As sorption, were investigated.MethodsSediment samples (upper 10 cm layer) were collected from three sites located in the vicinity of Cracow:Rudawa river — 37 km long river, flowing mainly through the suburban area;Vistula river — heavily contaminated, main Polish river;Dobczyce reservoir — artificial reservoir on Raba river, total capacity of 125,000,000 m3, supplying about 60% of drinking water to the city of Cracow.Using XRD and IR methods, mineral composition of sediments was analysed. Concentrations of iron, manganese, aluminium and arsenic as well as organic matter content in solid samples were analysed.Sorption experiment100 g of dry sediment sample was placed in a 400 ml volume glass beaker. 300 ml of arsenic containing solution was poured into the beaker. Every 30 min (total experiment time span equalled 7 to 7.5 hours), 0.5 ml of the suspension’ (the beaker content was constantly mixed) was collected and centrifuged, and the concentration of arsenic was determined in the supernatant.In the series of experiments, solution contained about 0.05 µg/ml of arsenic in organic (DMAA) and inorganic forms, at different pH values — 3, 5, 7 and 9.Results and DiscussionExamined sediments of Vistula river and Dobczyce Lake were characterised by relatively high concentrations of arsenic, iron, manganese and aluminium.Rudawa river. At pH 3, the concentration of inorganic As in solution decreased from an initial value of 0.049 µg/ml to 0.012 µg/ml in 7.5 hours time. The same decreasing tendency was found at pH 5