Biomedical subjects

Rudy Swennen

Publications and source records attributed to Rudy Swennen.

5 recordsLinked to original sources

PubMed2006

Leachability of heavy metals and arsenic from slags of metal extraction industry at Angleur (eastern Belgium).

At Angleur (eastern Belgium), a 53,000 m3 dump site, related to former Zn extraction, contains high concentrations of heavy metals and arsenic associated with minerals such as arsenopyrite (FeAsS), franklinite (ZnFe2O4) and willemite (Zn2SiO4). Eight representative samples were investigated by means of a modified availability test, which pointed towards a considerable availability of Cd, Pb and Zn. In addition a detailed analysis of leaching behaviour as a function of pH was performed by means of a pH(stat) leaching test. The results of this test were supported by modelling predictions with MINTEQA2. pH(stat) titration results also allowed determination of the acid neutralising capacity, making it possible to predict heavy metal release upon acidification, assuming a worst-case scenario. On a short- to medium-long term (+/-100 years) a release of 900 mg/kg Zn has to be expected upon assumed natural acidification. However, a leaching test performed at the natural pH (i.e. pH 8 for the sample studied) indicates that heavy metal release is very limited and far below the European limit values for slag material on dumps category 1. Therefore, despite the elevated total heavy metal and As concentrations on the site, leaching is relatively low under present environmental conditions. Moreover, the slag material has a rather elevated pH (6.5-8) and no acid mine drainage is produced. Glass phases seem very important in controlling heavy metal mobility since potential reactive minerals that are locked up in a silicate matrix are protected against leaching.

Arsenic↗

PubMed2004

Assessment of acid neutralizing capacity and potential mobilisation of trace metals from land-disposed dredged sediments.

In the past decades, large amounts of contaminated sediments have been dredged and spread out along rivers. The understanding of the fate and the behaviour of contaminants in dredged sediments is essential to deal with the management of contaminated sediments. Heavy metal leaching behaviour in dredged sediments of different ages since disposal, varying from 10 to 70 years, was assessed by pH(stat) leaching test and potentiometric titrations. Based on the pH(stat) titration results, two operationally defined pools of heavy metals, i.e., a labile and a slowly labile pool of heavy metals, were distinguished and quantified by mathematical description of leaching behaviour. The mathematical description of leaching behaviour during pH(stat) and potentiometric titrations allowed deduction of four groups of elements with a different type of leaching behaviour. Considering heavy metals, Zn, Cd and Ni displayed a leaching behaviour similar to acid neutralizing capacity (ANC), whereas the release of Cu, Pb and Cr was slower than ANC. However, no significant differences with regard to heavy metal leaching behaviour were found between sediments with different time since disposal on land. The elevated acid neutralizing capacity of the dredged sediments analysed in this study strongly decrease the risk of soil acidification with associated heavy metal leaching. The prediction of soil acidification over an extended period of time, together with the potential release of trace metals, was considered an important advantage of pH(stat) leaching tests compared to conventional leaching procedures.

Journal Article↗

PubMed2004

Influence of ripening on pHstat leaching behaviour of heavy metals from dredged sediments.

The influence of oxidation and ripening on the kinetics of heavy metal release from anoxic sediments was investigated by means of porewater analysis and pH(stat) leaching tests. During simulated land disposal of an anoxic river sediment, a considerable heavy metal (Cd, Zn and Ni) release into the porewater was observed after 25 days of exposure of the sediment to the air. The release kinetics of Cd and Zn during pH(stat) leaching indicated that their release was related to the oxidation of Cd- and Zn-sulfides. It was not completely clear whether the release of Ni was due to the oxidation of Ni-sulfides or to the introduction of H(+)(generated by the oxidation of sulfides or introduced by titration). The release of Cu seemed to be explained by the oxidation of both Fe-sulfides and Cu-sulfides. As such, pH(stat) experiments provided an indirect way to assess the mineralogy of the anoxic sediment. During ripening of the sediment, the release rate of Zn and Cd in pH(stat) leaching tests increased. For Ni, however, a similar release pattern was observed in the anoxic sediment and in the ripened sediments. Two weeks' drying at 100 degrees C resulted in an increase in the leachability of Cu. Nevertheless, at pH 4 and 6, the thermally treated sediment displayed a slower leaching of Cd and Zn than the ripened sediment. Although thermal treatment is often used to simulate ageing in soils, it cannot be used to simulate ripening of anoxic sediments.

Environmental Pollutants↗

PubMed2004

Secondary mobilisation of heavy metals in overbank sediments.

Heavy metal mobility was studied in overbank sediments of the Grote Beek river in Central Belgium. The geochemical signature of heavy metals in fine-scale sampled overbank sediments was compared with data on heavy metal emission into the river. The influence of acidification, organic and inorganic complexation on heavy metal mobility in overbank sediments was studied by single and sequential extractions and leaching tests. As confirmed by these tests, the elevated CaCl(2) content of the river water significantly enhanced the mobilisation of especially Cd, while Zn was mobilised to a lesser extent. The mobilisation of As on the other hand decreased in the presence of elevated CaCl(2) concentrations. Based on the results of single extractions, two highly contaminated zones with a different Cd mobility were observed in one of the overbank profiles. A detailed investigation of Cd leaching behaviour in the zone of Fe-accumulation during pH(stat) leaching tests, suggested that it was related to the association of Cd with Fe-oxides, while adsorption was the dominant binding form of Cd in the clay-rich part of the overbank sediment profile.

Aluminum Silicates↗

PubMed2003

Solid phase speciation of arsenic by sequential extraction in standard reference materials and industrially contaminated soil samples.

Availability, mobility, (phyto)toxicity and potential risk of contaminants is strongly affected by the manner of appearance of elements, the so-called speciation. Operational fractionation methods like sequential extractions have been applied for a long time to determine the solid phase speciation of heavy metals since direct determination of specific chemical compounds can not always be easily achieved. The three-step sequential extraction scheme recommended by the BCR and two extraction schemes based on the phosphorus-like protocol proposed by Manful (1992, Occurrence and Ecochemical Behaviours of Arsenic in a Goldsmelter Impacted Area in Ghana, PhD dissertation, at the RUG) were applied to four standard reference materials (SRM) and to a batch of samples from industrially contaminated sites, heavily contaminated with arsenic and heavy metals. The SRM 2710 (Montana soil) was found to be the most useful reference material for metal (Mn, Cu, Zn, As, Cd and Pb) fractionation using the BCR sequential extraction procedure. Two sequential extraction schemes were developed and compared for arsenic with the aim to establish a better fractionation and recovery rate than the BCR-scheme for this element in the SRM samples. The major part of arsenic was released from the heavily contaminated samples after NaOH-extraction. Inferior extraction variability and recovery in the heavily contaminated samples compared to SRMs could be mainly contributed to subsample heterogeneity.

Arsenic↗