Anomalias aerogamaespectrométricas (K, eU e eTh) da quadrícula de Araras (SP) e suas relações com processos pedogenéticos e fertilizantes fosfatos

Abstract

ABSTRACT. Radionuclides are present in the raw materials utilized in the manufacturing of some fertilizers and, consequently, the redistribution of uranium, thorium and potassium by agricultural activities may lead to the contamination of intensively fertilized soils. Airborne gamma-ray data on K, eU and eTh have shown the coincidence of aerogammaspectrometric anomalies and diabase sills in the Araras region (SP). This area is situated between the coordinates latitude 22 • 00 /22 • 30 south and longitude 47 • 00 and 47 • 30 west. As the contents of radionuclides in basic rocks are low and aerial gamma-ray surveys reveal gamma radiation from the 30 cm of the soil profile (coinciding with topsoil), interest has been raised to investigate which soils are included in the anomalies reported, as well as what sort of agricultural activity is carried out, in order to attest whether the source of radioactivity originated from the chemical fertilizers applied, thus establishing the main purpose of the present research. Integration by GIS has revealed that (i) eU and eTh anomalies occur on Latossolos Roxos massively fertilized with phosphates, on the level and elevated parts of the terrain; (ii) high levels of uranium are associated with clay particle size in regoliths developed on diabase sills; (iii) potassium and thorium anomalies follow Quaternary alluviums which extend along the banks of the Moji river, the occurrence of anomalous K accounting for the presence of feldspars in the included soils, and the occurrence of eTh related to local fertilization and to the transport of clays and iron oxides from the uppermost parts of the terrain, where the Latossolos Roxos under sugarcane are located. Radiochemical analyses of U and Th in fertilizers were in agreement with the literature, and it has been observed the influence of the geological genesis of the source of the raw material utilized in the production of the fertilizer, as well as the increase in uranium concentrations along with the P 2 O 5 content. Ground gamma-ray spectrometric measurements have shown good correlation with the airborne gamma-ray detections. In conjunction with magnetic susceptibility (k) readings have shown that uranium and thorium tend to concentrate in soils originated from the weathering of basic rocks, more developed, of clay texture, and predominance iron oxides. The retention higher than the ones found in diabase quarry.Keywords: Soils contamination, Uranium, Airborne gamma ray, Fertilizers, GIS. RESUMO.Radionuclídeos estão presentes nas matérias-primas utilizadas para a fabricação de alguns fertilizantes e, conseqüentemente, a redistribuição de urânio, tório e potássio pela atividade agrícola pode levar a contaminação dos solos intensivamente fertilizados. Dados aerogamaespectrométricos de K, eU e eTh mostraram, na Quadrícula de Araras (SP), a coincidência entre valores radiométricos anômalos e sills de diabásio. Estaárea está localizada no estado de São Paulo, situada entre as coordenadas 22 • 00 /22 • 30 de latitude sul e 47 • 00 e 47 • 3...

The use of in situ Gamma-Ray Spectrometry to Assess the Environmental Impacts of Intensive Agriculture in terms of Geochemical Mobility in soil and waters

“…Soils generated by the alteration of the Serra Geral Formation diabases are generally characterized by low concentrations of radionuclides (Conceição & Bonotto, 2006a), although several studies have pointed to the existence of radiometric anomalies in associated soils generated by the use of phosphate fertilizers in agriculture, especially for sugarcane (Souza & Ferreira, 2005;Conceição & Bonotto, 2006b). This fact may be related to the radiometric interest zones found in the study region, where presence of diabase-derived clay-rich soils and the occurrence of organic matter might lead to a geochemical sink for many elements and compounds, including radionuclides belonging to U and Th decay series originated from mineral fertilizers (Souza & Ferreira, 2005). However, Olivie Lauquet et al (2001) emphysises that the dissolved organic carbon (DOC) concentrations play an important role in a wetland's behavior as a sink or source of trace elements and their transfer to water systems.…”

“…In the case of agriculture and livestock farming, both activities have the capacity to drastically alter the integrity of soils and hydrological systems through the release of pesticides, nutrients, salts, sediments, organic matter, pathogens, and metals/heavy metals into the environment (Mateo-Sagasta et al, 2018). Thereby, the complexity of mobility of an specific element is given by physical-chemical conditions of soils and waters, whose values of pH, presence of clay minerals (texture), organic compounds, microorganisms, and the concentrations of other chemical species, play a profound role in the geochemical behavior of metals through the mechanisms of sorption/desorption, complexation, reaction and precipitation (Iaea, 1973;Becegato & Ferreira, 2005;Souza & Ferreira, 2005;Conceição & Bonotto, 2006a;Hussain & Hussain, 2011;Mazzilli et al, 2013).…”

Long Term Application of Fertilizers in Eastern Amazon and Effect on Uranium and Thorium Levels in Soils

“…The concentrations of U and Th are 5.6 and 2.6 times higher in triple superphosphate (TSP) than in single superphosphate (SSP), with 172.8 mg kg −1 of U and 2.1 mg kg −1 of Th [21]. In addition to the total U and Th concentrations in P-fertilizers, it is important to determine their bioavailability in soils [71].…”

Gamaespectrometria aplicada em solo agrícola no noroeste do Estado do Rio de Janeiro

“…O GRS-500 não fornece leituras em % de K ou ppm de U e Th. Embora seja possível fazer a conversão das leituras de cps para percentagem ou ppm, tem-se observado, em outros trabalhos empregando o GRS-500, que a prática comumé expressar os resultados em cps (Machado & Penha, 1997;Souza & Ferreira, 2005).…”