Arsenate concentrations

Arsenic. Total arsenic concentration can be determined by reduction of all forms to arsine (AsH ) and collection of the arsine in a pyridine solution of silver diethyldithiocarbamate. Organoarsenides must be digested in acidic potassium persulfate prior to reduction. The complex that forms is deep red, and this color can be measured spectrophotometricaHy. Reduction is carried out in an acidic solution of KI—SnCl2, and AsH is generated by addition of 2inc. 

Start the vapour generator cycle so that the absorption cell is flushed with argon gas and the pre-set volume of NaBH4 (1 mL) is pumped into the sample vessel. After the pre-selected reaction time (0.5 minute), AsH3 vapour is flushed into the absorption tube. Record the value of each arsenic signal as a peak height measurement. Read off the arsenic concentration of the sample, which is displayed on the instrument video screen. 

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. 

An experimental study at 350°C on the interaction between NaCl solution and graywacke which occurs widely in island arc geologic setting indicates that the final solution contains (0.6-0.7) ppm As (Bischoff et al., 1981). Analytical data on As concentration of hydrothermal solution at back-arc basins are few. Arsenic concentration of hydrothermal solution at Lau Basin is 6.0-8.2 ppm (Foquet et al., 1991). We can also estimate As concentration of hydrothermal solution based on the solubility data on orpiment and realgar because these As-bearing minerals are common in back-arc basin deposits (e.g., Okinawa Trough, Kuroko deposits). 

Arsenic concentrations of hydrothermal solutions issuing at midoceanic ridges, back-arc basins and island arcs (Shikazono, 1993)... 

Some innovating treatment technologies may be introduced in the treatment of wastewater generated in the aluminum fluoride industry to make its effluent safer. The ion exchange process can be applied to the clarified solution to remove copper and chromium. At a very low concentration, these two pollutants can be removed by xanthate precipitation.24 A combination of lime and ferric sulfate coagulation will effectively reduce arsenic concentration in the wastewater. 

Golding S. Survey of typical soil arsenic concentrations in residential areas of the city of University Place. Washington State Department of Ecology, Olympia, Washington, 2001. 

Pettry D.E., Switzer R.E. Arsenic concentrations in selected soils and parent materials in Mississippi. Mississippi State University Mississippi State, MS 39762, USA. 2000. 

The precision of the method was tested by carrying out replicate analyses (10) on 150 ml aliquots of two seawater samples from the Irish Sea. Mean ( sd) arsenic concentrations of 2.63 0.05 and 2.49 0.05 pg/1 amounts of were found. The recovery of arsenic was checked by analysing 150 ml aliquots of arsenic-free seawater which had been spiked with known amounts of arsenic (V). The results of these experiments shows that there is a linear relationship between absorbance and arsenic concentration and that arsenic could be recovered from seawater with an average efficiency of 98.0% at levels of 1.3-6.6 pg/1. Analagous experiments in which arsenic (III) was used gave similar recoveries. 

Epilayer thickness = 0.75 arsenic concentration = 5 x 1017 cm Epilayer chemically etched to remove 0.16 fim. 

Landrigan et al. (1982) conducted an epidemiologic survey to evaluate occupational exposure to arsine in a lead-acid battery manufacturing plant. Arsine concentrations ranged from nondetectable to 49 /breathing zone samples. A high correlation was found between urinary arsenic concentration and arsine exposure (r=0.84 p=0.0001 for an n of 47). Additionally, arsine levels above 15.6 /ig/m3 (=0.005 ppm) were associated with urinary arsenic concentrations in excess of 50 //g/L. The investigators concluded that exposure to a 200 /ig/m3 arsine exposure standard would not prevent chronic increased absorption of trivalent arsenic. 

Total arsenic concentrations in selected nonbiological materials... 

Arsenic concentrations in field collections of selected species of plants and animals... 

Table 28.1 Total Arsenic Concentrations in Selected Nonbiological Materials...

Table 28.2 Arsenic Concentrations in Field Collections of Selected Species of Plants and Animals (Values listed are in mg As/kg fresh weight [FW] or dry weight [DW].)... 

Ecosystem, Organism, and Other Variables Arsenic Concentration and Effects Reference3... 

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