Kinetics and reactions of hydrogen sulphide in solution of flooded rice soils

Abstract

The sulphide-ion electrode was used to study tile kinetics and reactions of free hydrogen sulphide in solution of flooded rice soiIs. The observed sulphide potential obeyed the Nernst equation over a range of sulphide-ion concentration from 10 -1 to 10 -19 M.Peak H2S concentrations were lowest in neutral soils high in iron and manganese; moderately high in soils low in iron or high in organic matter; and highest in acid sulphate soil low in iron. Harmful concentrations of H~S may be present in acid sulphate and acid soils low in iron during tile first few weeks after flooding. Tile concentrations in acid sulphate soils can be drastically lowered by liming.There was thermodynamic evidence for the presence of FeS and ZnS in the solutions of most soils.

Photoredoction of the chloropropionic acid of careentrazone‐ethyl in sodium sulfide crane flat meadow solutions

“…California rice field surface waters are oxidizing by comparison (S 2− < LOQ, E h +286.4 to +291.4 mV) and irradiated by intense UV light (47–1,386 μW/cm 2 at 310 nm, 84–3,180 ×W/cm 2 at 360 nm). Nondetectable S 2− , though consistent with the 1.4 μg/L (0.019 μM) concentration previously observed in a Japanese rice field [17], was possibly attributed to metal complexation (i.e., Fe[II], Mn[II], Zn[II], Cu[II], and Hg[II]) [18], bacterial oxidation (i.e., Chromatium, Chlorobium, Beggiatoa, Thiothrix , and Thiobacillus sp.) [37,38], auto‐oxidation by O 2 with dissolved metal catalysis (i.e., Fe[II], Cu[II], Mn[II], Co[II], and others) [39], and volatilization from water ( K H 1.05 × 10 −1 M atm −1 at 25°C for H 2 S [38]).…”

“…The polluted hypolimnion of Big Soda Lake (NV, USA) produced H 2 S/HS − levels of 786 mg/L [16], and the Salton Sea (CA, USA) as well as Europe's Black Sea are notorious for high concentrations. For flooded rice fields, one study determined 1.4 μg/L in surface water [17], whereas higher levels in soil interstitial water (<30 mg/L) [18,19] are consistent with its more reduced condition. Redox coupling of H 2 S/HS − with quinoids could follow, giving hydroquinone structures that are believed to be components of humic materials [2].…”

Role of Microorganisms in the Atmospheric Sulfur Cycle

“…There is no doubt that soil microorganisms can produce H2S by reduction of sulfate and by degradation of sulfurcontaining organic substances, but there does not appear to be any ., evidence that significant amounts of H2S are emitted from soils under natural conditions. This is not very surprising because soils have a substantial capacity for sorption of H2S (Smith et al, 1973), and there is good reason to believe that H2S produced by reduction of sulfate and other microbial processes in soils is rapidly converted to metallic sulfides (chiefly FeS) and that very little, if any, of this gas escapes to the atmosphere (see Ogata and Bower, 1965;Ponnamperuma, 1972;Kittrick, 1976;Ayotade, 1977). Harter and McLean (1965) were unable to detect evolution of H2S during incubation of a flooded Toledo soil that accumulated large amounts of sulfide (>2000 ILg/g soil) when incubated under waterlogged conditions.…”

Effects of Flooding on Soils

“…At the pH values of flooded soils, the bulk of the water-soluble hydrogen sulfide is present as H 2 S and HS~, but the activity of S 2~ is sufficient to precipitate Fe 2 + and Zn 2 + as insoluble sulfides (Ayotade, 1977). This keeps the concentration of H 2 S in the soil solution below 0.1 mg/liter, the toxic limit for rice.…”