Seasonal trends in erythemal and carcinogenic ultraviolet radiation at mid-southern latitudes 1989-1991

The effects of UVB radiation on temperate southern hemisphere forests

The temperate forests of the southern hemisphere are the most likely forests to be affected by increased levels of ultraviolet-B (UVB) radiation resulting from reduced ozone. The review describes these forests and then discusses the morphological changes, physiological effects, and protection mechanisms, particularly UV absorbing compounds that result from present day and increasing UVB radiation. Possible avenues for future research are explored.

Erythemal ultraviolet insolation in New Zealand at solar zenith angles of 30 and 45

Solar UV radiometers with spectral responsivities that are close to the erythemal/carcinogenic action spectrum of skin have been installed at several centers of population in New Zealand, including Auckland, 37 degrees S, Wellington, 41 degrees S and Christchurch, 43.5 degrees S. The data set covers the period from the time the radiometry program commenced in 1988/1989 to the end of the southern summer, March 1995. The radiometers were recalibrated annually and the data were corrected for changes in the absolute responsivity of the radiometers. Erythemally effective UV irradiances at solar zenith angles of 30 degrees and 45 degrees were then extracted from the data set. No monotonic trend in these data is apparent, although there are statistically significant differences in mean irradiances from one year to the next. An example of this is the decrease observed in all sites following the Mt. Pinatubo eruption in June 1991. The maximum erythemally effective insolations at solar zenith angles of 30 degrees and 45 degrees were consistently lower in Christchurch than in the other two New Zealand sites. This could arise from higher levels of atmospheric turbidity and/or tropospheric ozone at this location. Also, a seasonal increase in erythemally effective UV insolation from spring to autumn was observed each year in all three New Zealand sites.

Inactivation of enterococci and fecal coliforms from sewage and meatworks effluents in seawater chambers

Inactivation in sunlight of fecal coliforms (FC) and enterococci (Ent) from sewage and meatworks effluents was measured in 300-liter effluent-seawater mixtures (2% vol/vol) held in open-topped chambers. Dark inactivation rates (kDs) were measured (from log-linear survival curves) in enclosed chambers and 6-liter pots. The kD for FC was 2 to 4 times that for Ent, and inactivation was generally slower at lower temperatures. Sunlight inactivation was described in terms of shoulder size (n) and the slope (k) of the log-linear portion of the survival curve as a function of global solar insolation and UV-B fluence. The n values tended to be larger for Ent than for FC, and the k values for FC were around twice those for Ent in both effluent-seawater mixtures. The combined sunlight data showed a general inactivation rate (k) ranking in effluent-seawater mixtures of meatworks FC > sewage FC > meatworks Ent > sewage Ent. Describing 90% inactivation in terms of insolation (S90) gave far less seasonal variation than T90 (time-dependent) values. However, there were significant differences in inactivation rates between experiments, indicating the contribution to inactivation of factors other than insolation. Inactivation rates under different long-pass optical filters decreased with the increase in the spectral cutoff wavelength (lambda 50) of the filters and indicated little contribution by UV-B to total inactivation. Most inactivation appeared to be caused by two main regions of the solar spectrum--between 318 and 340 nm in the UV region and > 400 nm in the visible region.

Photodegradation of sulfamethoxazole: a chemical system capable of monitoring seasonal changes in UVB intensity

Sulfamethoxazole (SMX) in its nonionized form in aqueous solution has ultraviolet (UV) absorption that is maximal at 268 nm but extends through the ultraviolet-B (UVB) region. It was found to be extremely susceptible to photodegradation when exposed to artificial UV radiation through a Pyrex filter or to unfiltered natural sunlight. The SMX anion was more stable. The quantum yields of the photodegradation of both forms were determined by use of monochromatic light and ferrioxalate chemical actinometry, the values of 0.47 (pH 3.0) and 0.084 (pH 9.0) at the maximum absorption wavelengths (268 and 257 nm, respectively) being obtained. Using literature data on sunlight intensity, the photochemical shelf-life of SMX solutions exposed to direct sunlight was calculated for Sydney (latitude 33.5 degrees S) as a function of season of the year and verified experimentally. A fixed correlation was established between the rate constant for SMX degradation and UVB intensity measured by a radiometer, suggesting the capacity of this chemical system to monitor changes in the UVB region of sunlight.