Observations of H2O2 and PAN in a rural atmosphere

Measurements of gaseous H2O2 and peroxyacetyl nitrate (PAN) concentrations in air are given for a site in rural southern England over an approximately 4-year period. In both cases the data show both diurnal and seasonal patterns. Temperature and wind direction had clear influences on the recorded concentrations of both species. There was an indication of increasing H2O2 concentrations with time. The use of a two-dimensional global model confirmed that this would be expected to occur alongside growth in ozone formation. It is suggested that, during photochemical episodes, the sequential build-up of ozone, PAN and H2O2 could be important in influencing the ability of vegetation to resist the effects of aggressive pollutants.     

Cadmium availability to the cyanobacterium Synechocystis aquatilis in solutions containing chloride

Availability of cadmium to Synechocystis aquatilis (estimated by 109Cd sorption and cadmium toxicity-14C method) in solutions containing cadmium and complexing (KCl) or non-complexing (KNO3) salts, in the range of 0-0.5 m was investigated. Both cadmium surface adsorption and transport into the cells were lower in solutions containing cadmium chloride complexes (CdCl+, CdCl2, CdCl3-) than in those containing cadmium in the form of Cd2+. Also, cadmium toxicity in solutions of higher KCl concentrations, in which CdCl+ and CdCl2 forms predominated, was significantly limited.     

Deposition of ozone to a mature spruce forest: measurements and comparison to models

Removal of ozone at terrestrial surfaces provides a major sink for tropospheric ozone and, therefore, a constraint on the peak concentrations achieved during photochemical episodes. This study reports results from 5 years of almost continuous measurements of vertical profiles of ozone and related meteorological variables over a mature spruce forest in Bavaria. Deposition velocities calculated from flux/gradient and eddy correlation flux measurements have been compared with estimates based on a resistance model and yield satisfactory agreement during fine weather conditions. The results also suggest that biogenic emissions of reactive hydrocarbons from the forest influence the vertical profile of ozone.     

The effect of temperature and salinity on copper body-burden and copper toxicity to Hediste (Nereis) diversicolor

Temperature from 12 to 22°C and salinity from 30.5 to 7.6 increased accumulation of copper in Hediste diversicolor. Copper accumulated ranged from 85.83 to 217.14 g g^-1. Sediments reduced accumulation of copper under temperature-salinity combinations. Accumulated copper ranged from 90.19 to 153.26 g g^-1.However, mortality of the worms was not solely dependent upon copper body-burden. It ranged from 34 to 45% and from 38 to 80% in the presence of sediment. A combination of osmoregulatory and thermal stresses increased the toxic effect of copper to the worms.     

The effects of salinity,temperature and sediment on the toxicity of copper to juvenile Hediste (Nereis) diversicolor (O. F. Muller)

Without sediment, increasing salinity (7.3 to 29.2) and increasing temperature (12 to 22 °C) reduced the toxicity of copper to juvenile Hediste diversicolor. The LC₅₀ values ranged from 357 gL^-1 in 7.3 to 513 g L^-1 in 29.2 at 12°C and from 247 to 500 g L^-1 at 22°C. In deionized water all the juvenile were dead in all solutions to which copper was added (100 to 600 g L^-1). Dead worms were swollen and everted their pharynxs. In higher doses of copper (500 to 600 g L^-1) the worms were abnormal in behaviour in all salinities (0 to 29.2). The ability to swim or crawl was disturbed.With sediments increasing temperature and increasing salinity increased the toxicity of copper to the worms. The LC₅₀ values ranged from 3200 to 4100 g L^-1 at 22°C. The response of the juvenile to copper was antagonistic to increasing temperature and salinity and synergistic to increasing salinity and increasing temperature without and with the sediment respectively.     

Trace metals in interstitial waters from sandstones: acidic inputs to shallow groundwaters

There is some evidence from southern Britain that shallow groundwaters in non-carbonate lithologies may be affected by acidic deposition. To investigate this, interstitial water profiles down to 12 m have been obtained from unsaturated sands or semi-consolidated sandstones from the Folkestone Beds (Lower Greensand) of Surrey and the Sherwood Sandstone of the West Midlands. The pH of the interstitial waters generally increased with depth and reflected an increase in the base saturation of the exchange complex. Beneath the highly acidic surface soil horizons (pH 3.0-3.5), interstitial waters with a pH of 4.0-4.5 were found down to depths of several metres. The pH progressively increased to around pH 5.5 because of base cation desorption and the weathering of silicate minerals. High concentrations of aluminium (10-20 mg litre(-1)) and other metals (Fe, Mn, Cu, Ni, Co, Zn, Be) were found in the interstitial water in the upper unsaturated zone. Most metal concentrations were strongly pH-dependent but also reflected the geochemical characteristics of the parent sands or sandstones. H+ and trace element concentrations were slightly higher beneath areas of afforestation than beneath heathland. The downward fluxes of solutes have been estimated using rainfall-derived chloride as a non-reactive solute. The profiles retain a record of 10-20 years input allowing the past inputs from SO4 and other species to be estimated using solute/chloride ratios. Cation exchange sites are probably depleted over a period of decades and there can be a significant decrease in the unsaturated zone pH as a result of increased or sustained acidic deposition. The shallow groundwater environment (0-15 m) in non-carbonate terrains is therefore a sensitive environment where high metal concentrations may be generated and may ultimately lead to water quality problems in shallow water supplies.     

Relation between mortality of young walleye (Stizostedion vitreum) and recruitment with different forms of compensation

The relation between mortality of young fish and recruitment is important for assessment of the environmental effects of facilities that kill large numbers of young fish, such as electric power stations and hydropower plants. A simulation model with a bioenergetic growth component was applied to examine the relation between mortality of young and recruitment for walleye (Stizostedion vitreum) with different forms of population regulation, including: food limited growth, food limited growth with size-dependent mortality, and food limited growth with age at maturity dependent on size. With food limited growth small increases in mortality of young reduced recruitment considerably, but the population slowly approached a new equilibrium. If mortality of young increased when growth was food limited, the population approached a new equilibrium of natality and mortality because with fewer individuals there was more food per individual, and individuals were larger in size and produced more eggs; this feedback adjusted natality to equal mortality. With either mortality or age at maturity dependent on size, large increases in mortality of young resulted in only small decreases in recruitment.