ABSTRACT
The use of Sargassum spp., a brown invasive algae, for the production of biochars (BCs) or activated carbons (ACs) and their efficiency to sequestrate chlordecone (CLD) in soil has been recently suggested. The objective of this study was to assess the potential of microwave prepared Sargasso biochar (BCS) amendment in Andosol on the bioavailability of chlordecone in laying hens and piglets, when exposed to this matrix. The efficiency of BCS was compared to a commercial activated carbon, DARCO® (ACD), used as a positive control and to an unamended soil. Samples of CLD-contaminated Andosol were amended with 2% of each carbonaceous matrix and let maturing for 3 months. Thereafter, adequate doses of soil were administered into the laying hens and piglets diets every day during the exposure phase, to simulate involuntary soil ingestion which may happen in practical conditions when animals are reared outside. Finally, bioavailability tests were carried out on target tissue (liver, muscle, adipose tissues and egg yolk). The results showed that the highest reduction of CLD bioavailability was obtained with ACD in both animal species. For laying hens, ACD showed reductions of around 60% (liver: 59%, muscle: 57% and egg yolk: 56%) whereas the BCS showed reduction of around 30% (liver: 31%, muscle: 26% and egg yolk: 30%) compared to the unamended soil. For piglets, only the liver showed interpretable results with reduction of 65% with ACD and 41% with BCS. Overall, BCS is efficient reducing CLD availability but in a lower extend than ACD. This discrepancy may be explained by the variations of physico-chemical characteristics that exist between the two matrices, resulting, from the additional activation phase for DARCO®. Therefore, to improve the efficiency of BCS it would be interesting to move towards DARCO® characteristics by determining out the optimal microwave pyrolysis parameters.
ABSTRACT
Biochars (BCs) and activated carbons (ACs) are well-known carbon-rich materials that are being increasingly studied in environmental sciences for water treatment applications to remediate pollutant sequestration in soil. This study aimed to assess the impact of Sargasso BC particle size and amendment rate on the environmental availability of DDT and DDT metabolites in two distinct Kazakh soils. These two soils were collected in the vicinity of storehouse facilities in Kyzylkairat and Beskainar that store banned pesticides. They presented very distinct concentration levels of DDT and DDT metabolites. Three different types of carbonaceous matrices were tested: Sargasso BC and two commercial ACs (ORBOTM and DARCO©). For the granulometry effect, Sargasso BC was ground, and two particle sizes were tested (<150 µm, >150 µm) and compared to an unground material. Four distinct application rates were tested (0.25, 0.5, 1, and 2% (w/w)). After a three-month maturation period, environmental availability was assessed using an ISO/DIS 16751, part B-modified methodology. Interestingly, the best reductions in DDT environmental availability were obtained with the finest particle size (both ACs and Sargasso BC < 150 µm). More specifically, the effectiveness of the strategy seemed to depend on many factors. Firstly, a clear soil effect was demonstrated, suggesting that the more contaminated the soil, the more efficient this strategy may be. Secondly, the results showed that an increase in the amendment rate improves the immobilization of DDT and DDT metabolites. The sequestration material demonstrated different efficiency values (up to 58 ± 4% for Sargasso BC < 150 µm and 85 ± 4% for DARCO at a 2% application rate). Finally, a clear molecule effect was displayed, demonstrating the following immobilization order: p,p'-DDE > p,p'-DDD > p,p'-DDT > o,p'-DDT.
