Sebastian Elgueta

Atrazine dissipation in a biobed system inoculated with immobilized white-rot fungi

ABSTRACT Due to environmental concerns about accumulation of the herbicide atrazine in food products and water reservoirs, there is a need to develop safe and economical methods for its dissipation. The main aim of this study was to evaluate atrazine dissipation in a biobed system inoculated with immobilized white-rot fungi in a pelletized support (PS). All fungal isolates evaluated were efficient in colonizing the surface and inner parts of the PS, with no differences observed in the colonization over the assay. The highest atrazine dissipation (93%) was observed for Stereum hirsutum Ru-104 after 60 days of incubation. In contrast, the lowest atrazine dissipation (78%) was observed for the non-inoculated biobed over an identical period. Trametes versicolor HL01 was involved in the highest phenoloxidase activity. This activity indicates that inoculated and non-inoculated biobeds were biologically active over the incubation period. A high respiration rate in the biobed was observed when it was inoculated with S. hirsutum Ru-104. Inoculation of fungi on PS systems may be a coadjutant in the increase of fungal efficiency in enzymatic production.

Pesticide residues in leafy vegetables and human health risk assessment in North Central agricultural areas of Chile

ABSTRACT To investigate pesticide residue concentrations and potential human health risk, a study was conducted in 118 leafy vegetable samples collected in 2014–2015 from the North Central agricultural areas of Chile. The pesticide residues were determined using the multiresidue QuEChERS method by gas chromatography as well as high-performance liquid chromatography. The results indicated that 27% of the total samples contained pesticide residues above the maximum residue limits of each active ingredient. The maximum estimated daily intake obtained for carbon disulphide (CS2), methamidophos, azoxystrobin and cypermethrin were 0.57, 0.07, 0.06 and 0.05 mg kg−1, respectively, which was higher than their acceptable daily intake. It is concluded that inhabitants of the North Central agricultural area of Chile are not exposed to health risks through the consumption of leafy vegetables with the exception of methamidophos. Nevertheless, the high levels of methamidophos detected in leafy vegetables could be considered a potential chronic health risk.

PELLETIZATION OF Anthracophyllum discolor FOR WATER AND SOIL TREATMENT CONTAMINATED WITH ORGANIC POLLUTANTS

Pellets of the white-rot fungus Anthracophyllum discolor with activated carbon and sawdust (complex pellets) were formulated for the degradation of lignin in water and the bioremediation of soil contaminated with pentachlorophenol (PCP). The complex pellets were formed by a center of activated carbon and sawdust surrounded by fungal mycelium, whereas simple pellets consisting of only mycelium were hollow spheres. Degradation of lignin was performed in an airlift reactor at initial lignin concentration of 1000 mg L -1 and the fungal pellets were re-used two times in batch operations. Complex pellets degraded lignin by 87 and 72% in the first and second cycle, respectively, and they were significantly more effective than simple pellets. In addition, complex pellet showed higher manganese peroxidase activity in the reactor. For the bioremediation of soil contaminated with PCP (150 mg kg -1 of soil) the pellets were added to soil surface. PCP degradation in soil with complex pellets was 85% at 28 days of bioaugmentation, being higher than in soil with simple pellet. A fungus growth was also observed only in soil with complex pellet. Sawdust and activated carbon appear to be suitable carriers of A. discolor for degradation of organic pollutants in wastewater and soil.

Atrazine, chlorpyrifos, and iprodione effect on the biodiversity of bacteria, actinomycetes, and fungi in a pilot biopurification system with a green cover

ABSTRACT The use of biopurification systems can mitigate the effects of pesticide contamination on farms. The primary aim of this study was to evaluate the effect of pesticide dissipation on microbial communities in a pilot biopurification system. The pesticide dissipation of atrazine, chlorpyrifos and iprodione (35 mg kg−1 active ingredient [a.i.]) and biological activity were determined for 40 days. The microbial communities (bacteria, actinomycetes and fungi) were analyzed using denaturing gradient gel electrophoresis (DGGE). In general, pesticide dissipation was the highest by day 5 and reached 95%. The pesticides did not affect biological activity during the experiment. The structure of the actinomycete and bacterial communities in the rhizosphere was more stable during the evaluation than that in the communities in the control without pesticides. The rhizosphere fungal communities, detected using DGGE, showed small and transitory shifts with time. To conclude, rhizosphere microbial communities were not affected during pesticide dissipation in a pilot biopurification system.