S. Murao

Quantitative analysis of untreated hair samples for monitoring human exposure to heavy metals

Abstract The method of quantitative analysis for untreated hair samples, which we developed three years ago, has proved to be quite useful for investigating environments contaminated by certain toxic elements. In the present work, the experimental conditions are improved. Loss of certain elements owing to irradiation damage, which has remained as one of the experimental uncertainties, was examined. It was found that the concentration of sulfur decreases gradually throughout the irradiation, while for the other elements, including arsenic and mercury, no changes occur under our measuring conditions. Furthermore, the degree of alteration of elemental concentration depending on the position along the hair was investigated. As a result, concentrations of some elements at different positions on a 14-cm-length hair, which was taken from a small-scale miner in the Philippines, showed some dependence on the distance from the root reflecting her history as a miner, while mercury does not show large deviation from a main trend. It was also found that concentration of mercury in hairs taken from different parts of a body does not show large difference. These results demonstrate that mercury and arsenic concentration in hairs, obtained by the present method, become a good index for an estimation of human exposure to these toxic elements. Changes of concentration of some elements depending on the way of cleaning before irradiation are studied in detail and the optimum way of washing is established.

PIXE measurement of human hairs from a small-scale mining site of the Philippines

In gold-producing regions of the Philippines, so-called pocket miners are mining and smelting the ore bygold amalgamation. The amalgamation process and smelting of amalgam are usuallydone inside houses especiallyin the kitchen. It is of concern that people become exposed to vapor mercurybyinhalation with this practice. The Mines and Geosciences Bureau of the Philippines – Cordillera Administrative Region (CAR) communicates to pocket miners the hazards of mercuryto the bodyas well as the damage that mercurycauses to the environment. Knowing the toxicityof mercury, miners came to request that their head hairs be analyzed. Consequently, a standard-free method of quantitative analysis for untreated bio-samples was applied to the hairs to estimate their degree of exposure to mercury. The analytical result indicated the anomalous accumulation of mercury especially for women who stay longer and often smelt the amalgam inside the house. 2002 Published byElsevier Science B.V.

QUANTITATIVE ANALYSIS OF UNTREATED HUMAN NAILS FOR MONITORING HUMAN EXPOSURE TO HEAVY METALS

In order to address global environmental issues, a standard-free method developed by ourselves has been successfully applied to various kinds of bio-samples. Especially, a method for untreated hairs has been applied in many polluted areas to study human exposure to toxic elements. In addition to hair, nail is expected to give us valuable information about human exposure to toxic elements. However, the analysis requires relatively large amounts of samples and laborious sample preparation techniques which necessitate internal standards. In this work, we have developed a quantitative method for untreated human-nail analysis based on the standard-free method. It requires neither large amounts of nails nor complicated target preparation procedure. Furthermore, it is perfectly free from any ambiguity in target preparation such as volatilization of certain elements and contamination of the sample during chemical ashing. The optimum conditions of irradiating nail samples are established, and accuracy and reproducibility of the present method are confirmed. It is found that ultrasonic washing in distilled water is effective for many nail samples preventing the loss of elements from the sample. It is also found that elemental concentration in nails strongly depends on their sampling positions.

A THREE-DETECTOR MEASURING SYSTEM USING A PURE-Ge DETECTOR

A three-detector measuring system making use of a pure-Ge detector combined with two Si(Li) detectors has been developed. The efficiency curve of the pure-Ge detector has been determined easily as relative efficiencies to those of the existing Si(Li) detectors, since this system allows us to analyze a sample with the pure-Ge and the Si(Li) detectors simultaneously under the same irradiating conditions. It is found that detection efficiencies of the pure-Ge detector decrease just above the absorption edge of Ge owing to absorption of X-rays in the dead layer of the detector. Accuracy of the efficiency curve thus obtained was confirmed by analyzing a few samples whose elemental concentrations are known. It is confirmed that a pure-Ge detector can be used in place of a Si(Li) detector for the purpose of analysis of elements Z ≧ 19, since its energy resolution is almost equal to that of a high-performance Si(Li) detector and efficiencies at high energies are far better. Moreover, it becomes possible to detect prompt γ-rays and to analyze light elements such as fluorine, which arouses much interest from the point of view of environmental contamination. Detection limit of fluorine is found to be less than 0.1 ppm for water samples.

Distribution of rare metals in kuroko-type ore: a PIXEPROBE study

Abstract We have performed PIXE analysis of kuroko-type ore from Okinawa, Japan using the proton microprobe (PIXEPROBE). The specimens are modern analogue of kuroko ore from the JADE hydrothermal site of the Okinawa Trough. We analysed five kinds of ores dredged from the sea floor: (1) barite ore with small sulfide dissemination; (2) sphalerite-pyrite chimney; (3) pyrite ore; (4) sulfide veinlets in strongly altered rock; and (5) pyrite megacrystals in strongly altered rock. The analyses revealed that the trace element distribution is regulated by the occurrence mode of the ore, and within each ore, by the crystal structure. The distribution suggests that the hydrothermal system for kuroko ore formation is quite heterogeneous and its chemistry is controlled by local factors such as difference in temperature, and that in situ PIXE analyses are essential for effective beneficiation strategy for the rate-metals from kuroko-type ore.

TRACE ELEMENT ANALYSIS OF TAILINGS FROM AN INDIGENOUS MINING COMMUNITY, BENGUET, PHILIPPINES

Tailings from an indigenous mining community were analyzed by PIXE to study the residual amount of gold and to check the relative increase in mercury content after the mineral dressing. The result showed that gold is sometimes left in the tailings at ore-grade concentration up to 30 ppm, and that relative mercury content is not increasing drastically. Since the tailings are trade target in the local community, it would be necessary for stakeholders to have a common and fair facility where they can assay gold content of the tailing at regular interval.

APPLICATION OF PIXE TO MONITOR THE QUALITY OF SALT FROM SALT FARMING AREAS IN THAILAND

In salt farms of Thailand, saline ground water is pumped up and then solar-evaporated to produce salt for commercial purpose. However, when they continue to precipitate salt in the same pools, the product is stained yellow or brown in color. In order to recover only white salt, workers cut trees and create a new pool next to the old one. Due to this practice, year by year, salt-farming area loses vegetation cover and expands barren section of salt damage. In order to understand the changes of in salt grains, salt was collected and measured by PIXE. The result indicates that manganese is clearly responsible for the coloring, and possibly also irons. This information is expected to base the discussion to stop deforestation in the salt-damaged area.

METHOD OF QUANTITATIVE ANALYSIS OF FLUORINE IN ENVIRONMENTAL SAMPLES USING A PURE-Ge DETECTOR

We recently developed and reported a three-detector measuring system making use of a pure-Ge detector combined with two Si(Li) detectors. The efficiency curve of the pure-Ge detector was determined as relative efficiencies to those of the existing Si(Li) detectors and accuracy of it was confirmed by analyzing a few samples whose elemental concentrations were known. It was found that detection of fluorine becomes possible by analyzing prompt γ-rays and the detection limit was found to be less than 0.1 ppm for water samples. In this work, a method of quantitative analysis of fluorine has been established in order to investigate environmental contamination by fluorine. This method is based on the fact that both characteristic x-rays from many elements and 110 keV prompt γ-rays from fluorine can be detected in the same spectrum. The present method is applied to analyses of a few environmental samples such as tealeaves, feed for domestic animals and human bone. The results are consistent with those obtained by other methods and it is found that the present method is quite useful and convenient for investigation studies on regional pollution by fluorine.

THE ROLE OF PIXE IN ENVIRONMENTAL MONITORING AND EDUCATION OF SMALL-SCALE MINERS OF GOLD

Artisanal/small-scale gold mining is one of the important livelhood for deprived people in many countries. The activity is expected to support peoples life and activate local economy. However amalgamation method is common to recover gold in this type of mining, and due to this practice, mercury is being released into the natural environment. During the ore treatment process, miners uptake mercury not only by inhalation of the vapor but also by absorption of liquid mercury through the skin. In order to cope with health problems and environmental damages arising from the use of mercury, there should be coordination between national/local government, aid agencies and scientific institutes. In addition, the environmental education and risk communication are keys to mitigate the environmental damage by the miners. For such purpose, quick and precise trace element analysis as a base of discussion on occupational health risk is indispensable and our trial proved that PIXE is one of the most flexible and versatile system. In this paper examples of trial through a Japan-Philippines partnership will be presented.

Elemental behavior during the fractionation of felsic magma at Hobenzan polymetallic province, SW Japan

Abstract We have performed PIXE microprobe analysis of rock-forming minerals in granitoids at the Hobenzan polymetallic region of unique CuBiAsCoWB mineralization. The analysis was carried out at CSIRO using 5 to 30 μm beam of 3 MeV protons, and the following elements were detected: Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Mo and Sn. In the case of biotite, incompatible elements such as Rb and Y show positive correlation with the Differentiation Index (DI) of the rocks. Ore forming elements such as Zn and Sn have similar trend to that of the incompatible elements. This fact implies that some of the ore forming elements do not directly enter the magmatic fluid that is evacuated from parental magma but they need to be extracted from minerals through water/rock interaction to be components of the mineralizing fluid. Our result also indicated that biotite is an ideal mineral to monitor the elemental behavior during the evolution of a magmatic-hydrothermal system.