Annotated Bibliography for the photographic paper hydrogen sulfide assay (Thanks to Dr. Horwell for consulting on this bibliography):

Horwell, C.J., Allen, A.G., Mather, T.A., Patterson, J.E., 2004. Evaluation of a simple passive sampling technique for monitoring volcanogenic hydrogen sulphide. J. Environ. Monitor. 6, 630 - 635.

Summary: Describes the basic protocol for developing the photographic paper test strips. The sensitivity determined for the assay in this paper was <<30 ppb to approximately 1000 ppb of Hydrogen Sulfide. The silver halide in the photo paper reacts with hydrogen sulfide to form silver sulfide which cause the color of the paper to change from white, to yellow to brown and then black. the color of the paper from "H2S + 2AgCl = Ag2S + 2HCl". Light exposure is not a major problem as " The fixing process also removes any colour change from the effect of sunlight on the samplers." Paper clearly describes laboratory testing conditions that we should replicate.

The reaction rate with the photopaper assay is linear, until the AgCl is used up which is indicated by the test strips black color: "The absorption characteristics of the samplers at different H2S concentrations are illustrated in Fig. 3a & b. From this it is evident that, at least at the two lower concentrations, absorp- tion was linear (an unchanging relationship was obtained between the quantity of sulfide absorbed and exposure time) for vy10 mg cm22 S22 absorbed. With continuing exposure to H2S the rate of absorption becomes non-linear, as availability of AgCl declines. The results suggest that full saturation (complete loss of AgCl) occurs at app. 15 ug cm2 S2. These features were in agreement with observed colour changes, with the fully saturated strips being dark brown– black in colour."

Hardiness of the teststrips: they can be washed with cold water and exposed to light without loss of fidelity: "No significant difference in measured sulfide was obtained between the different fixing/washing procedures tested, giving confidence that field samples can be quite robustly handled, and washed, in cold water, to remove any particulate surface contaminants."

Important to use test strips made from the same batch of photo paper: "It is likely that the physical and chemical composition of photographic paper may vary slightly between batches. It is, therefore, advisable that a sampling run should always be carried out from a single batch of samplers manufactured under identical and controlled conditions."

Horwell, C.J., Patterson, J.E., Gamble, J.A., Allen, A.G., 2005. Monitoring and mapping of hydrogen sulphide emissions across an active geothermal field: Rotorua, New Zealand. J. Volcanol. Geotherm. Res. 139, 259-269.

Summary: Describes use of photographic paper testing strips in Rotorua, New Zealand. Great images of the final strips as well as helpful in thinking through how we might design a town or neighborhood wide survey with these strips. This study was a year long. There is also useful information on possible false positives which include:

"Metallic silver can also react with oxidizing species such as nitrogen dioxide in oxygen, producing mixtures of silver nitrate (AgNO3) and silver oxide (Ag2O, which also causes blackening) (Kim, 2003). Similarly, silver halides respond with a colour change reaction when exposed to reduced sulphur compounds. In the atmosphere reduced sulphur exists in the form of compounds including H2S, di methyl sulphide ((CH3)2S), carbon disulphide (CS2), carbonyl sul- phi de ( COS) , met hyl mer capt an ( CH3 SH) and dimethyl disulphide ((CH3)2S2). Of these compounds, hydrogen sulphide and dimethyl sulphide dominate the reduced sulphur gas emissions budget due, respectively, to their volcanogenic and oceanic sources (Berresheim et al., 1995). Silver oxide may be formed in the presence of oxidizing species such as NO2 or H2O2, however, in the volcanic regions where H2S is likely to be of concern, concentrations of such oxidants tend to be low, so that in the absence of light, any darkening of a silver halide substrate is due overwhelmingly to the presence of sulphide. Since dimethyl sulphide is not emitted during volcanic activity, H2S measurement in volcanic regions, using the technique described here, is virtually interference-free."

Papers providing evidence for aspects of this test:

Paper documenting how Hydrogen Sulfide Tarnishing Silver and produces Silver Sulphide, the rate of this reaction depends on levels oxygen and humidity: Pope, D., Gibbens, H.R., Moss, R.L., 1968. The tarnishing of Ag at naturally-occurring H2S and SO2 levels. Corrosion Science 8, 883 – 887.

Book about amount of silver halide in Ilford Photographic paper: C. B. Neblette, Photography - Its principles and practice, Chapman & Hall Ltd, London, 4th edn., 1942.

Papers on potential false positives:

"Metallic silver can also react with oxidizing species such as nitrogen dioxide in oxygen, producing mixtures of silver nitrate (AgNO3) and silver oxide (Ag2O, which also causes blackening) (Kim, 2003)." (Horwell 2005) Kim, H., 2003. Corrosion process of silver in environments containing 0.1 ppm H2S and 1.2 ppm NO2. Materials and Corrosion 54, 243 – 250.

Reduced Sulphur compounds also cause silver halide to tarnish for more on rates of reduced sulphur compounds in the environment see: Berresheim, H., Wine, P.H., Davis, D.D., 1995. Sulfur in the atmosphere. In: Singh, H.B. (Ed.), Composition, Chemistry and Climate of the Atmosphere. Van Nostrand Reinhold, New York, pp. 251 – 307.

Alternative passive H2S monitoring systems: Natusch, D.F.S., Sewell, J.R., Tanner, R.L., 1974. Determination of hydrogen sulfide in air—an assessment of impregnated paper tape methods. Analytical Chemistry 46, 410 – 415.

Shooter, D., Watts, S.F., Hayes, A.J., 1995. A passive sampler for hydrogen sulfide. Environmental Monitoring and Assessment 38, 11 – 23.

1. 1. Purnell, N. G. West and R. N. Brown, Chem. Ind., 1981, 17, 594–599.

Plant growth maybe reduced in areas of high hydrogen sulfide: H. Sase, T. Takamatsu and T. Yoshida, Can. J. For. Res., 1998, 28, 87–97.