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A similar cause for environmental concern is the presence of mercury in the agricultural soils of the Panoche Fan. To the west of the San Joaquin Valley, a major, mercury mineralization district is located near the town of Idria. The New Idria Mine, operated between 1858 and 1972, was the second largest mercury producer in North America.
Streams that drain the north, east, and south sides of the mining district all contribute sediment to the Panoche Fan. Chemical analyses of soil samples from the Fan clearly show that the soil contains elevated mercury levels. These high levels of mercury could be caused by a combination of natural geochemical dispersion and mining activity, considering the time period of major mercury production at the New Idria Mine (scroll back to \"Mapping the Chemistry of the Earth\' Surface\" for a discussion of dispersion halos).
Like the selenium, the mercury data were generated using AAS. The rocks were digested and the solution was then reduced to form elemental mercury, which was separated as mercury vapor and measured with AAS. This method is called the cold vapor-AAS method. Return to this point in index.
Robots in the laboratory
Geochemical studies generate large quantities of samples to be analyzed in the laboratory. Although technological advances have produced vast improvements in analytical measurements and data reduction, the manual preparation of samples has remained a time-consuming problem. As a result, one of the most rapidly growing areas in laboratory automation is the use of robotics for sample preparation.
What does a robot have in common with a technician= An arm, hand, and fingers. The robots arm moves up/down, in/out, and rotates 360x.
The fingers grip tubes and flasks, and the hand rotates for pouring liquids.
A laboratory robot generally consists of an arm, a hand, and a pair of fingers. These components are programmed to duplicate the sample preparation usually performed by a laboratory technician. The centrally positioned robot moves samples in and out of laboratory work stations. Each work station performs a specific function such as dispensing acids, mixing, heating, centrifuging, filtering, and weighing.
There are several advantages to the use of robotics. Robots have improved productivity by a factor of 2 or 3. Because sample preparation requires the use of hazardous chemicals, the robot minimizes human exposure to these chemicals. By delegating the repetitive applications to the robot, the technician is available to assume greater responsibilities. Finally, robots provide consistency in sample preparation and improve the precision of the data.
In USGS laboratories, robotics have been applied to a range of techniques including sample disaggregation, the decomposition of tens of thousands of samples per year for the ICP-AES methods, the weighing of 7,000 charges of flux per year for the XRF major element analyses method, and other similar sample preparation methods. The use of laboratory robotics continues to increase as the benefits from each application are realized. Return to this point in index.
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