Determination of tin in biological materials by atomic absorption spectrophotometry and neutron activation analysis

Towards highly economical and accurate wastewater sensors by reduced parts of the LED-visible spectrum

Interest is growing in simple, fast and inexpensive systems to analyze urban wastewater quality in real time. In this research project, a methodology is presented for the characterization of COD, BOD₅, TSS, TN, and TP of wastewater samples, without the need to alter the samples or use chemical reagents, from a few wavelengths, belonging to the different color groups that compose the visible spectrum in isolation: (380-700 nm): violet (380-427 nm), blue (427-476 nm), cyan (476-497 nm), green (497-570 nm), yellow (570-581 nm), orange (581-618 nm), and red (618-700 nm). In this study, about 650 raw and treated urban wastewater samples from over 43 WWTPs and a total of 36 estimation models based on genetic algorithms have been calculated. Seven models were calculated for each pollutant parameter; one model for each color group of the visible spectrum, except for TN, which includes an additional model combining the wavelengths of the violet and red region of the spectrum. All the calculated models showed high accuracy, with an R² between 80 and 85 % for COD, BOD₅ and TSS, and 66-74 % for TN and TP. The tests carried out have shown the accuracy of the models of the different color groups to be very close to each other. However, it is noted that the models making use of the wavelengths between 497 and 570 nm (green) were the ones that showed the best performance in all the parameters under study. This research work lays the foundations for the development of cheaper, faster, and simpler wastewater monitoring and characterization equipment.

Accumulation of metals in autopsy tissues of subjects living in Tarragona County, Spain

The concentrations of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), tin (Sn), vanadium (V) and zinc (Zn) were determined in autopsy tissues collected from subjects who at the time of death had lived in Tarragona (Catalonia, Spain) over a period of, at least, the previous 10 years. Samples of liver, lung, kidney, brain and bone were obtained from a total of 78 non-occupationally exposed subjects, autopsied between 1997 and 1999. Arsenic, Cd, Co, Cr, Cu, Pb, Mn, Hg, Ni, Sn, V and Zn were determined by inductively coupled plasma spectrometry (ICP/MS). The results were analyzed with respect to age, sex, smoking and drinking habits, and the subject's place of residence. Most tissue concentrations of As, Co, Cr, Hg and V were near to the analytical detection limit or, in some cases, even below it. However, the levels of Cu were slightly higher than the average concentrations found in other studies. Also, tissue concentrations of Mn, Sn and Zn were similar to those found in previous surveys, while those of Ni were lower than previously reported. Although the current levels of tissue Cd and Pb were comparatively lower than in studies in other areas, the distribution of both metals was similar to previously-reported trends. From the tissue metal concentrations observed in the present study, it would appear that neither environmental exposure nor a dietary excess of these elements could be considered a health hazard to people living in the study area.