Monitoramento ambiental de metais - traço no centro regional de ciências nucleares do nordeste (CRCN-NE): impactos e análises no solo e na vegetação.

Abstract

Trace metals concentrate on the soil surface due to precipitation or charge interactions between the metals and the soil. The study of these elements in soils is a method used to measure anthropogenic emissions in ecosystems. This work considers the initial environmental conditions of the land where the Regional Center for Nuclear Sciences was built. Soil samples were taken from 5 representative points on the land; surface soil samples were collected by scraping with plastic material, while soil samples at depths of 0-20 cm and 60-80 cm were obtained from cores made of carbon steel. Initially, the soil samples (0.1g) were transferred to fluorocarbon tubes belonging to a microwave oven, where they underwent acid digestion in the presence of 10 mL of water, 5 mL of HNO3, 4 mL of HF, and 1 mL of HCl. After digestion, the samples were diluted with water to a concentration of 1/25 g/L and analyzed using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The determination of major elements was performed by atomic absorption spectrometry (AAS). For Co, the average value is around 11 mg/kg, which agrees with the average value found in soil. The results obtained for Y varied around 20 mg/kg, while the average value in the Earth's crust is 40 mg/kg. The average concentrations of La were 60 mg/kg at a depth of 60-80 cm and 30-40 mg/kg at the surface, values higher than those reported in the literature. The values obtained for Ce ranged from 53 mg/kg at the surface to 112 mg/kg at a depth of 60-80 cm. The results found at the surface for Fe varied between 10,000-16,000 mg/kg, while the average value for the depth of 60-80 cm was 31,000 mg/kg, a value close to the average for soils. The results for Pb showed an average at the shallowest depths, around 44 mg/kg, and at the depth of 60-80 cm, an average of 25 mg/kg was observed, a value close to the 29 mg/kg reported in the soil. The value of Th varied between 9-12 mg/kg at the studied depths; these concentrations are similar to the average value found in the Earth's crust. The concentration obtained for U ranged from 3-7 mg/kg at the studied depths; these values are higher than the average of this metal in the soil. The concentration of Mg varied between 3750-6200 mg/kg, while the average value cited in the literature for soil is 8000 mg/kg. The soil samples demonstrated homogeneity of metals both in depth and across the area of the land. Considering subsequent analyses, the concentrations of lead did not change over the years, while the concentrations of magnesium doubled over the years.