The Contrasting Behaviour of Arsenic and Germanium Species in Seawater

Abstract

The vertical profiles of inorganic arsenic [As(III)+As(V)], monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), inorganic germanium and monomethylgermanium (MMGe) were investigated at three sampling stations in the Pacific Ocean. In addition, the concentrations of these species in various surface waters have also been determined. The vertical profile of both inorganic arsenic and germanium displayed low concentrations, 1100 to 1450 ng dm3 for inorganic arsenic and <0.7 to 2 ng dm3 for inorganic germanium, in the surface zone. The concentrations of inorganic arsenic increased with depth to maximum concentrations that varied from 1500 to 2200 ng dm3 at a depth of 2000 m and then slowly decreased to concentrations that varied from 1300 to 1900 ng dm3 at a depth of 5000 m. On the other hand, the vertical profiles of inorganic germanium displayed a relatively constant concentration (4 to 8 ng dm3) from a depth of 2000 m to 5000 m. These vertical profiles of inorganic germanium were linearly correlated with those of silicate with a Ge/Si molar ratio of 0.715×106. Both MMAA and DMAA displayed maximum concentrations in surface water and abruptly dropped with depth from 0 to 200 m. The concentration in surface water was 12 ng dm3 for MMAA and varied from 48 to 185 ng dm3 for DMAA. At depths >200 m, MMAA and DMAA were generally at comparable concentrations of about 3 ng dm3. In the case of MMGe, it was uniformly distributed throughout the water column at a concentration of approximately 16 ng dm3, indicating that MMGe was not involved in the biogeochemical cycling of inorganic germanium. In deep waters (>200 m), the concentrations of both inorganic arsenic and germanium increased from the southern Tasman Sea to the north. The increase in inorganic arsenic concentration was linearly correlated with that of phosphate and the increase in inorganic germanium concentration was linearly correlated with that of silicate, with apparent δAs/δP and δGe/δSi molar ratios of 4.53×103 and 0.73×106, respectively. © 1997 by John Wiley & Sons, Ltd.

Speciation and Seasonal Variations of Dissolved Inorganic Arsenic in Jiaozhou Bay, North China

“…Average As concentrations in open seawater usually show little variation and typically range between 14 and 25 nmol/l (Cutter et al 2001;Ellwood and Maher 2002). As a member of Group V in the Periodic Table, the behavior of arsenic is similar to that of phosphate and shows nutrient-like depth profiles in the ocean, indicating uptake by phytoplankton and regeneration from degradation of organic detritus (Andreae 1979;Sanders 1979;Middelburg et al 1988;Sanders and Riedel 1993;Santosa et al 1994Santosa et al , 1996Santosa et al , 1997Cutter and Cutter 1998;Cutter and Measures 1999;Cutter et al 2001). The As content in riverine and estuarine waters are more variable as a result of varying bedrock lithology and river inputs, but are usually low, at typically less than 2 μg l −1 for river water and 4 μg l −1 for estuarine water under natural conditions (Smedley and Kinniburgh 2002).…”

Arsenic and high affinity phosphate uptake gene distribution in shallow submarine hydrothermal sediments

“…3e). A similar observation in the Pacific Ocean water column (Santosa et al 1997), hints that the global sediment As and P cycles are not mutually exclusive. Calculated reactive S and Fe ratios (Fig.…”

“…Indeed, Mn, Fe and S chemistry are the main chemical components that strongly influence environmental As mobility (Takamatsu et al 1985; Cullen and Reimer 1989; Dando et al 1995; Santosa et al 1997; Ouvrard et al 2002; Smedley and Kinniburgh 2002; Dixit and Hering 2003; O’Day et al 2004; O’Day 2006; Maity et al 2005; Lafferty et al 2011; Breuer and Pichler 2013; Chi Fru et al 2013; Dekov et al 2013; Giovannelli et al 2013; Gilhooly et al 2014; Kilias et al 2013; Price et al 2013a, b; Ruiz-Chancho et al 2013; Villalobos et al 2014; Godelitsas et al 2015). Mn oxides specifically oxidize As(III) and then adsorb and precipitate the resulting As(V) (Takamatsu et al 1985; Ouvrard et al 2002; Maity et al 2005; Lafferty et al 2011; Villalobos et al 2014).…”

Arsenic in Natural Environments

“…At their sampling sites in the Pacific Ocean, Santosa et al (1997) found that MMA(V) and DMA(V) concentrations were highest at the surface with 0.012-0.016 μg L −1 and 0.048-0.185 μg L −1 , respectively. The concentrations sharply declined to depths of 200 m. From depths of 200 to at least 5000 m, MMA(V) and DMA(V) concentrations stabilized at about 0.003 μg L −1 (Santosa et al, 1997).…”