Earthworms to improve glyphosate degradation in biobeds.

In this work, earthworm effect on the efficiency of biobeds for glyphosate degradation was studied. Three biomixtures with and without the addition of earthworms (Eisenia fetida species) were evaluated. The initial concentration of glyphosate was 1000 mg/kg biomixture. Glyphosate and biological parameters were measured as a function of time. Earthworm survival, biomass, and reproduction were evaluated as well. All biomixtures that contain earthworms reached 90% of glyphosate degradation at 90 days in comparison with the biomixtures without earthworms that reached 80% approximately at the same time. Also, within the biomixtures that contained earthworms, glyphosate degradation rate was significantly higher in the one made up with soil and wheat stubble (Ws-E) showing excellent capacity for aminomethylphosphonic acid (AMPA) degradation, the main metabolite of glyphosate degradation. In addition, a study performed after the vermiremediation process showed that E. fetida can tolerate high glyphosate concentration without modifications in its life traits. It can be concluded that the use of E. fetida within the biobeds is an excellent combination to improve glyphosate and AMPA removal.

Earthworms to assess the innocuousness of spent biomixtures employed for glyphosate degradation.

In this study, the innocuousness of different biomixtures employed for glyphosate degradation was tested through Eisenia fetida earthworms. Eight biomixtures were prepared with local materials: alfalfa straw (AS), wheat stubble (WS), river waste (RW) and two different soils (A and B). Each biomixture was divided into two equal portions: one without glyphosate application (control substrate) and the other was sprayed with a commercial glyphosate formulation of 1,000 mg glyphosate a.i. kg-1 biomixture (applied substrate). The bioassay started when all sprayed biomixtures reached high percentages of glyphosate degradation (spent biomixtures). Three parameters were studied: survival, adults and juveniles biomass and reproduction. The results allowed the identification of three biomixtures (AWS, BWS and BWSRW) for good maintenance and development of E. fetida. In addition, at the end of the bioassay two of the viable biomixtures (AWS and BWS) showed the highest performance of juvenile earthworms compared to a reference soil. The Principal Component Analysis (PCA) indicated that the biomixtures containing high silt and clay percentages and minor density renders higher values of earthworm growth and reproduction. Therefore, these innocuous biomixtures can be used as organic amendments or recycled materials for new treatments on biobeds.

Benthic invertebrates structure in wetlands of a tributary of the middle Parana River (Argentina) affected by hydrologic and anthropogenic disturbances.

The present study was aimed at analyzing chromium concentrations in water column and bottom sediments in the main channel of Northern Salado River (tributary of Middle Parana River) and its floodplain. The main changes caused by human activities and hydrological disturbances on benthic invertebrate structure were also analyzed. Sediment concentrations of the reference area varied between 44.2 and 97.1 microg Crg(-1) (dw), and in the impacted zone, between 85.5 and 209 microg Cr g(-1) (dw) reaching the highest values in the wetland floodplain. Alfa, beta and gamma diversities in the reference section have been 33, 9 and 66 species, and in the disturbed section, they have been 37, 8.33 and 74 species, respectively The species dominant in the disturbed habitats were characterized by a small body size and short life cycles, as the species of olig chaetes Naidinae. The extreme flooding produced a rejuvenation of the area with the consequent physical re-structuration produced by flooding, showing: a marked decrease in chromium levels in sediments and in organic matter content, which allowed the colonization of insects (Ephemeroptera and Trichoptera).