Environmental agate mining impacts and potential use of agate residue in rangeland

The impacts of agate exploitation on soils and the adjacent landscapes are poorly understood. In addition, agate processing produces residues whose potential use in agriculture must be evaluated, in order to develop cleaner production practices. The aims of this study were: i) to estimate the effects of agate mining on the soil and the adjacent landscapes; ii) to evaluate the chemical and mineralogical composition of agate; and iii) to test the use of agate powder in native grassland soils. Remote sensing techniques were used to map the soil uses around mine sites to evaluate their interference with the adjacent landscapes. Agate powder, an industrial residue, was chemically and mineralogically characterized, and its effects on soil were tested. We used 0; 1000; 2000; 4000 and 8000 kg ha(-1) of agate powder applied to natural grassland in a randomized block design experiment with four replications. The application was repeated in the 47th week after the initial application. The findings showed that the mines had a weak effect on the surrounding landscapes (i.e., native forest, native pasture and annual crops). However, locally, the soil organic matter contents of mine areas decreased, while the potential acidity and toxic aluminum levels increased. Low doses of agate used in rangeland soils had a healthy effect on soil pH, potential acidity and toxic aluminum, while high doses decreased the available K in soil and in the dry matter of the rangeland plants. Little effects were observed on the Si content in the soil or in the plants. Finally, our study highlights that agate exploitation has local impacts on the soil and adjacent landscapes and that agate residue may be used in rangelands at low doses with beneficial results for some soil attributes. These results consists in cleaner production practices for beneficing industry, farmers and environmental since preserving rangeland areas. (C) 2020 Elsevier Ltd. All rights reserved.