Biomassa e concentração de nutrientes e silício em cana-de-açúcar cultivada em solo adubado com diatomita - DOI:10.5039/agraria.v15i4a8755

Anthropogenic activities increase the amount of potentially toxic elements (PTEs) in the environment and consequently affect the quality of soils and water resources. This study aimed to investigate the concentrations, spatial distribution, and sources of soil and sediment pollution at the watershed scale for the following PTEs: aluminum (Al), barium (Ba), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), lanthanum (La), manganese (Mn), neodymium (Nd), nickel (Ni), lead (Pb), praseodymium (Pr), scandium (Sc), samarium (Sm), thorium (Th), titanium (Ti), vanadium (V), yttrium (Y) and zinc (Zn). One hundred and eighty-eight composite samples collected from preserved Cerrado areas, channel banks, agricultural areas, pastures, and riverbed sediments were used. Environmental contamination was assessed using geochemical indices and ecological risk assessment. The concentration of these elements often followed the order of riverbed sediment > channel bank > pasture > agricultural areas. Based on the pollutant load index, riverbed sediments and channel banks were classified as polluted, acting as a source of PTEs. The Gurgueia watershed, Brazil, was classified as unpolluted to moderately polluted, with low to no enrichment by PTEs. These values serve as a basis for future monitoring of the impacts resulting from the advance of agricultural and industrial activities in the region.

With the global increase in microplastic pollution, even environments considered pristine have shown signs of being affected by these contaminants. In this context, it becomes essential to conduct studies that identify and quantify the presence of microplastics in remote regions such as Antarctica. This continent is particularly relevant due to its low anthropogenic influence and its essential role in regulating planetary ecosystems and biodiversity. In this study, 49 Antarctic samples were analyzed using pretreatment techniques with NaCl and ZnCl₂ saline solutions, followed by fluorescence microscopy using Nile Red dye to estimate the microplastic abundance index. Both solutions showed good performance in the separation and identification of particles. Approximately 37% of the samples showed contamination by potential microplastics (PMPs), with a higher concentration of particles retained on paper filters and fibers observed in the supernatants. The results indicate that the presence of MPs in Antarctica is irregular and not ubiquitous, differing from other studies that suggest a wider distribution. It is speculated that the observed contamination results from oceanic transport from other regions of the planet and from sources associated with human activities on the Antarctic continent (e.g., tourism and research).

Nitrogen fertilization in flooded rice systems can promote nitrate leaching and groundwater contamination, particularly where groundwater is used for human consumption. This study aimed to assess soil susceptibility to nitrate leaching toward groundwater in rice-growing areas of Rioja, San Martín, Peru. Sampling was based on a semidetailed soil map of the Rioja sector, from which 14 soil series were identified; one georeferenced point was established per series, with soil collected at two depths (0–20 and 20–40 cm). From these points, four representative soil profiles were selected through a Delphi consensus process and classified as Typic Endoaquepts (P1 and P2), a Typic Endoaquoll (P3), and a Fluventic Endoaquept (P4). The 28 saturated hydraulic conductivity (Ks) measurements were used to develop a local pedotransfer function, in which the inverse of bulk density was the main predictor of Ks. Profile-specific Ks estimates were incorporated into HYDRUS-1D to simulate nitrate transport under an identical fertilization regime over 10 years. Ks averaged 0.21 cm·h⁻¹ with high variability (CV = 84.12%), and the pedotransfer function explained 42.9% of this variability (R²adj = 0.383, RMSE = 0.127 cm·h⁻¹). Despite receiving identical fertilizer inputs, the four profiles showed simulated nitrate transport differing by up to 19.9%, driven by differences in soil hydraulic properties and profile structure rather than by management practices. Flow-weighted mean nitrate concentrations at the lower model boundary ranged from 48.33 to 57.96 mg·L⁻¹; two profiles (P4 and P1) exceeded the 50 mg·L⁻¹ WHO guideline, reflecting a greater leaching risk in soils that are more stratified and have higher hydraulic conductivity, while the profile with the highest organic carbon content (P3) showed lower susceptibility, likely due to greater denitrification. These findings indicate that local soil properties are a key control on nitrate leaching susceptibility, supporting the need for soil-type-specific nitrogen management to protect groundwater resources.