Water arsenic concentration

Table 3.7 lists some arsenic measurements for various marine waters. Arsenic concentrations in seawater are usually 1.1-1.9 pg L-1 with an average of 1.7 pg L-1 (Matschullat, 2000), 305. The typical concentration of arsenic at the surface of open ocean water is about 1.5 pg L-1 and deep waters in at least the Pacific and... 

In contrast to open ocean water, arsenic concentrations in estuary waters often significantly vary with time and location. The arsenic contents of estuary waters and sediments depend on many factors, including... 

Fig. 17. Arsenic in water Highest reported well water arsenic concentrations by country (from WHO, 2004c)...

Although bedrock influences river-water arsenic concentrations, rivers with typical pH and alkalinity values (ca. pH 5-7, HCO <100 mgL ) generally contain lower concentrations of arsenic, even where groundwater concentrations are high, because of oxidation and adsorption of arsenic onto particulate matter in the stream bed and dilution by surface runoff. Arsenic concentrations in the range <0.5-2.7 pgL have been reported for seven river-water samples from Bangladesh, with one sample containing 29 p,g (BGS and DPHE, 2001). 

There is much evidence for arsenic release into shallow sediment pore waters and overlying surface waters in response to temporal variations in redox conditions. Sullivan and Aller (1996) investigated arsenic cycling in shallow sediments from an unpolluted area of the Amazonian offshore shelf. They found pore-water arsenic concentrations up to 300 p.g in anaerobic sediments with nearly coincident peaks of dissolved arsenic and iron. The peaks for iron concentration were often slightly above those of arsenic (Figure 1). The magnitude of the peaks and their depths varied from place to place and possibly seasonally but were typically between 50 cm and 150 cm beneath the sediment-water interface (Sullivan and Aller, 1996). There was no correlation between pore-water arsenic concentrations and sediment arsenic concentrations (Figure 1). 

McCreadie H., Blowes D. W., Ptacek C. J., and Jambor J. L. (2000) The influence of reduction reactions and solids composition on pore-water arsenic concentrations. Environ. Sci. TechnoL 34, 3159-3166. 

Ayotte, J. D., Ryker, S. J., and Proctor, A., 2001, Variation in bedrock ground-water arsenic concentrations and implications for human-health studies in New England in Geological Society of America, 2001 annual meeting, Boston, MA. 

Several studies have reported daily and seasonal variations in raw water arsenic concentration. For example, one study reported diurnal variations in arsenic of 39-59 and 57-83 p,g/L in a stream (16). Seasonal concentration variations have also been reported (17-20), including 11-21 (21) and 16-63 p,g/L (22) in surface waters and 10-220 pg/L (23) in a groundwater. Variations in arsenic concentration and speciation will become increasingly important to water utilities trying to meet a lowered MCL. 

Figure 5.3. Arsenic concentration in treated water (arsenic concentration in the polluted water = 100 xg L ). FeCls was used as the coagulant. The system was operated at different feed water flow rate (F) to membrane area (A) ratios (FM = from 4.7 to 36.7 L m h ) corresponding to the time intervals marked by dotted lines.

Biomonitoring Measuring arsenic concentration in biofluids (most established being urine arsenic levels) and tissue samples remains the most classical approach. Study included 70 research subjects from four villages in endemic arsenicosis area, Shanyin coxmty, Shanxi province. Authors detected saliva, urine and water arsenic concentrations using inductively coupled plasma mass spectrometer (ICP-MS) and atomic fluorescence spectrometry-230 [22 ]. 

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