A. H. Oliveira

Application of instrumental neutron activation analysis and inductively coupled plasma-mass spectrometry to studying the river pollution in the State of Minas Gerais

Instrumental neutron activation analysis (INAA) and inductively coupled plasma-mass spectrometry (ICP-MS) have been used for the determination of toxic heavy metals and other pollutants in the water of the Das Velhas river in the State of Minas Gerais, in south-east Brazil. Elemental concentrations of about 60 elements were measured in water samples collected to different parts of this river and from two affluents. There was a good agreement between the two analytical methods and the results were complementary. The results indicated an increase in the concentration of several polluting elements in the water from mining industry area.

Determination of natural radioactivity in beach sand in the extreme south of Bahia, Brazil, using gamma spectrometry

The natural radionuclides activity concentrations in beach sand of the extreme south of Bahia, Brazil, was measured by Gamma Spectrometry. The Radium Equivalent Activity, the external hazard index, the absorbed dose rate and the annual effective dose were assessed and compared with internationally published values for external dose and activity concentrations. The activity concentrations of 226 Ra, 232 Th and 40 K in beach sand ranged from 8.4 to 8,300 Bqkg -1 with a mean value of 910 Bq.kg -1 , from 21 to 18,450 Bqkg -1 with a mean value of 2,220 Bqkg -1 and from 3.4 to 3,110 Bqkg -1 with a mean value of 352 Bqkg -1 , respectively. The results indicate that the absorbed dose rates range from 21 to 14,450 nGyh -1 with mean value of 1,792 nGy.h -1 . The highest value of gamma dose rates among the studied beaches were found in Cumuruxatiba (14,450 nGyh -1 ). The annual effective dose range between 0.03 and 17.70 mSvy -1 , with the mean value of 2.20 mSvy -1 . In four studied beaches, the assessed outdoor annual effective doses are above the worldwide average of 0.07 mSvy -1 as reported by the United Nations Scientific Committee on the Effects of Atomic Radiation. Especially in the area of black sands, a big part of Cumuruxatiba beach, whose annual effective dose of 17.70 mSvy -1 is much higher than worldwide average.

Comparison of Neutron Activation Analysis and ICP-MS used for river water pollution control

This paper compares the performance and limitations of two analytical methods for samples from the environment: Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma with Mass Spectrometry (ICP-MS). A Brazilian river, the Das Velhas, was chosen as the test-site. This river runs through a Fe, Mn and Au mining area. The two methods were initially tested on three international reference materials: SLRS-3 (riverine water, Research Council Canada), GS-N (granite, ANRT, France) and SOIL-7 (soil, International Atomic Energy Agency, Vienna, Austria). Actual river samples (water and sediments) were analysed next. The INAA and ICP-MS results were generally in good agreement. However, ICP-MS analysis occasionally suffered from random flask contamination (e.g. Zn). The concentrations obtained by ICP-MS for certain elements (e.g. Zr) were lower than the certified values and results from INAA, probably because the dissolution of their natural forms (oxides) was not complete. For INAA, only one irradiation run was used. Some elements with short half-life radioisotopes (e.g. Mn, Mg or V) and usually analysable by NAA were not detected. The results obtained for the Das Velhas river showed a strong relationship between mining activity and pollutant concentrations. Increased concentrations of certain metals corresponded to passage of the river through the industrial mining area. The use of both INAA and ICP-MS enabled accurate results for water and sediment samples to be obtained for approximately 50 elements. For water analysis, ICP-MS was clearly the most convenient method, as INAA was handicapped by the effect of radiolysis which prevented irradiation of liquid samples. For sediment analysis, sample preparation time for ICP-MS was time consuming. INAA avoided these problems and could be used as a reference method. Routinely, a particular method was selected for each element.