Chromium speciation and existing natural attenuation conditions in lagoonal and pond sediments in the former chemical plant of Porto-Romano (Albania) |
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| Authors: | A Shtiza R Swennen A Tashko |
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| Institution: | (1) Faculty of Sciences, Geology Department, Katholieke Universiteit Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium;(2) Faculty of Geology and Mining, Geochemistry Department, Polytechnic University Tirana, Rr. Elbasanit, Tirana, Albania |
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| Abstract: | Near the outskirts of the Albanian port of Durres on the Adriatic Coast, at a place called Porto Romano, an old chemical complex
has been producing chromate salts for a period of ∼20 years (1972–1993). As a result large quantities of chromite ore processing
residue (COPR) waste were released mainly as suspended particles and/or dissolved species in effluents, which settled in a
decantation pond area, 200 × 250 m in size, east of the industrial plant. Unfortunately, pollutants were spread out with time.
Knowing that chromium mobility and toxicity in natural settings is species dependent, the species characterization has been
carried out in different sampling media (pond sediments, lagoonal sediments and water samples). Five pond profiles were sampled
within the decantation area up to a depth of ∼1 m, till the underlying Quaternary lagoonal silty-clays were reached. Total
Cr content is highly variable with values between 1,130 and 24,409 mg/kg which is clearly higher than the defined local background
values for lagoonal silty-clays (198 mg/kg of Cr). Leaching of Cr(VI) especially occurs in the pond sediments, which are low
in OC, CEC and clay content, under acidic and neutral pH conditions (e.g. up to ∼2,230 mg/kg Cr(VI) leached from a sample
containing a total concentration of Cr 12,200 mg/kg). Moreover, leaching of the Cr(III) occurs only under strictly acidic
conditions (maximum 1,144 mg/kg leached from a sample containing a total Cr-concentration of 17,608 mg/kg). In this study
also a number of natural attenuation conditions (i.e. reaction with lagoonal clays rich in organic matter and iron as well
as isomorphous substitution) have been recognized. |
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| Keywords: | COPR Speciation Chromate (Cr(VI)) Chromite (Cr(III)) Mineralogy Geochemical modelling Local background (LB) |
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