Influence of 2,4-D residues on the soil microbial community and growth of tree species.

The 2,4-D (2,4-dichlorophenoxyacetic acid) has low half-life in the soil, but it is capable of altering the soil microbial community. The objective of this study was to evaluate the influence of 2,4-D residues on the structure of the soil microbial community and the growth of tree species. The tolerance and phytoremediation potential of tree species were evaluated. The microbial analysis was performed by T-RFLP. The 2,4-D herbicide reduced the plant height of K. lathrophyton, number of leaves of C. ferrea and K. lathrophyton and root dry matter allocation for C. brasiliense, I. striata, P. heptaphyllum, and T. guianensis. Cucumis sativus intoxication on soil contaminated with 2,4-D was not significant. The structure of Fungi community in the rhizospheric soils of C. ferrea was altered. The herbicide 2,4-D increased the diversity of Fungi in rhizospheric soils of P. heptahyllum and R. grandis. Most tree species were tolerant, and the evaluation time was sufficient to remedy 2,4-D. The structures of the microbial communities Archaea, Bacteria, and Fungi were little influenced by 2,4-D. The diversity of the Archaea domain was not affected, the diversity of the Bacteria in Inga striata decreased while the fungi increased in Protium heptaphyllum and Richeria grandis with 2,4-D.

Sensitivity of the macrophytes Pistia stratiotes and Eichhornia crassipes to hexazinone and dissipation of this pesticide in aquatic ecosystems.

Herbicide wastes from agriculture areas can contaminate water resources and affect non-target organisms. Since herbicides reach groundwater and rivers, these residues can damage the aquatic ecosystem. Hexazinone is an herbicide widely used in sugarcane cultivation and has a potential to contaminate water resources. Therefore, studies are necessary to know the possible damages of this herbicide on aquatic organisms, as well as the behavior of this pesticide in those systems. In this study, our objective was to evaluate the sensitivity of the macrophytes Pistia stratiotes and Eichhornia crassipes to hexazinone, as well as the dissipation of these pesticides. The variables intoxication, fresh matter accumulation, and leaf anatomy were used to evaluate the sensitivity of the macrophytes to hexazinone. The hexazinone concentration in water was performed by HPLC-MS. Hexazinone concentrations equivalent to 111 and 333 µg L-1 were toxic to the macrophytes. Pistia stratiotes produced less fresh matter production than Eichhornia crassipes when exposed to the hexazinone. The hexazinone application did not change the adaxial epidermic (EAD), abaxial epidermic (EAB), palisade parenchyma (PP), aerenchyma (AER) and leaf blade (LAF) of Pistia stratiotes at any concentration tested. Concentrations equivalent to 333 µg L-1 changed the PP and LAF of Eichhornia crassipes. The presence of this herbicide in water negatively affects the fresh matter accumulation and leaf structure of the Pistia stratiotes and Eichhornia crassipes, respectively. The presence of these macrophytes delayed the dissipation of hexazinone due to them impair other pathways of degradation of this herbicide in aquatic environments. The presence of this herbicide in water negatively affects the growth and development of the Pistia stratiotes and Eichhornia crassipes.

Phytoremediation of Brazilian tree species in soils contaminated by herbicides.

The phytoremediation potential of Brazilian trees species Calophyllum brasiliense, Eremanthus crotonoides, Hymenaea courbaril, Inga striata, and Protium heptaphyllum was investigated for contaminated soils containing ametryn and hexazinone. Visual injury, chlorophyll content, plant height, leaf temperature, leaf number, and water-efficient use were evaluated. Residual herbicides at soil substrates were analyzed by LC/MS. Among the species C. brasiliense and H. courbaril were tolerant to both herbicides. P. Heptaphyllum presented tolerance at ametryn treatment. E. crotonoides, I. striata, and P. heptaphyllum died in hexazinone treatment. A high content of residual ametryn was found for E. crotonoides. In ametryn treatment, residual herbicide has decreased for C. brasiliense and E. crotonoides species. C. brasiliense highlighted among others becoming a good agent for phytoremediation of soils contaminated with traces of ametryn and hexazinone.