Vertical gradients of ozone and carbon dioxide within a deciduous forest in Central Pennsylvania

Ambient concentrations of ozone (O(3)) and carbon dioxide (CO(2)) were measured at locations from the forest floor to the top of the canopy in a deciduous forest at the Moshannon State Forest in northcentral Pennsylvania. O(3) concentrations were measured from May-September for three years (1993-1995) while CO(2) concentrations were measured only during July and August of 1994. O(3) concentrations increased steadily during the day at all locations, peaking during the middle to late afternoon hours. O(3) concentrations then steadily declined to their lowest point, just before dawn. Vertical O(3) concentration gradients varied seasonally and among years. However, O(3) concentrations were highest within the forest canopy and lowest at the forest floor, with an average difference of approximately 13%. Differences in O(3) concentrations between the canopy and forest floor were greatest at night. O(3) concentrations were slightly higher at locations within the canopy than above the canopy. CO(2) concentrations were consistenly higher near the forest floor and were higher above the canopy than within the canopy. CO(2) concentrations were higher at night than during the day at all locations, especially near the forest floor.     

Organic carbon concentration profiles in recent cave sediments: records of agricultural pollution or diagenesis?

Recent (<7 years old) cave sediments in Speedwell Cavern, Derbyshire, show an approximately exponential decay of organic carbon with depth. This phenomenon was thought to be due to one of two causes: (i) changing agricultural practice within the catchment feeding the cave, especially the increased use of sewage sludge and animal slurry as fertilizer; (ii) a relatively constant organic carbon concentration over time in the input sediment, with subsequent carbon mineralization during diagenesis. Carbon isotope composition of the organic material and the evolution of H/C ratio with depth indicate that the latter hypothesis is correct and that the profiles result from microbial diagenesis, not increased organic carbon inputs. By comparison with sediment of known (7 years) age, temporal decay constants for organic matter can be derived; these lie between rates previously determined for organic matter decomposition in marine sediments and soils. The H/C ratio of organic matter can be modelled as a function of time and proceeds in a similar fashion to soil organic material.     

Mass transfer resistance in ASFF reactors for waste water treatment

Analysis of mass transfer resistances was performed for an aerated submerged fixed-film reactor (ASFF) for the treatment of waste water containing a mixture of sucrose and ammonia. Both external and internal mass transfer resistances were considered in the analysis, and characterized as a function of feed flow-rate and concentration. Results show that, over a certain operating regime, external mass transfer resistance in the system was greater for sucrose removal than ammonia. This is because the reaction rates for carbon removal were much larger than those of nitrogen. As a result, existence of any form of mass transfer resistance caused by inadequate mixing or diffusion limitations, strongly affects the overall removal rates of carbon more than nitrogen. Effects of the internal m?ss transfer resistance were virtually non-existent for ammonia removal. This behaviour was found over two orders of magnitude range for the effective diffusivity for ammonia, and one order of magnitude for the film specific surface area. However, over the same parameters' range, it is found that sucrose removal was strongly affected upon lowering its effective diffusivity and increasing the film specific surface area.     

The uptake of particulates by an urban woodland: site description and particulate composition

Woodlands may improve local air quality by increasing the uptake rates of gaseous, particulate and aerosol pollutants from the atmosphere and can also act as relatively permanent sinks for some pollutants. Rough Wood, Walsall was selected for a study of the material which accumulates on tree foliage because of its location in a densely populated urban area, and its proximity to a motorway with high traffic flow (the M6) and to other pollutant sources. Methods were developed for leaf washing to allow determination of the quantity of dust and the identification of the dust particles present on oak leaves. Elemental analysis of particles was also undertaken using scanning electron microscopy coupled with electron probe microanalysis. A large proportion of particles were organic in origin. Of the inorganic particles, the majority contained silicon and aluminium in varying proportions suggesting that they were soil derived. Some particles were clearly identified as the products of combustion, and sea or road salt was present on leaf surfaces. Some particles contained copper, tin and titanium which may reflect the proximity of Rough Wood to local metal workings. The number of particles counted on leaf surfaces decreased as distance from the motorway increased.     

Effects of the insect growth regulator (S)-methoprene on survival and reproduction of the freshwater cladoceran Moina macrocopa

This study examines the acute and chronic effects of the insecticide (S)-methoprene on the survival and reproduction of the freshwater cladoceran Moina macrocopa. In laboratory toxicity tests, the 24- and 48-h LC50 values for (S)-methoprene were 0.51 and 0.34 mg litre(-1), respectively. Survival, longevity and fecundity were reduced at 0.05 mg litre(-1) and higher concentrations. At 0.005 and 0.01 mg litre(-1), longevity and fecundity increased slightly as compared to control animals. If environmental concentrations of methoprene do not exceed 0.05 mg litre(-1), as is generally the case, application of this insecticide is unlikely to induce detrimental effects on natural cladoceran populations. The stimulatory effect of very low levels of methoprene on reproductive performance is consistent with the hypothesis of a regulatory role of juvenile hormone-like compounds in crustacean reproduction.     

Enzymatic degradation of poly([R,S] β-hydroxybutyrate)

The synthetic analogue of a bacterially produced polyester, poly(-hydroxybutyrate) (PHB) was synthesized from racemic -butyrolactone using anin situ trimethyl aluminum-water catalyst. The polymer was fractionated into samples differing in molecular weight and isotactic diad content. The latter was closely related to degree of crystallinity. The biodegradation of these fractions were examined by monitoring mass loss over time in the presence of anAlcaligenes faecalis T1 extracellular bacterial poly(-hydroxybutyrate) depolymerase. The fraction with high isotactic diad tacticity content showed little or no degradation over a 50 hour incubation period, whereas the fraction of intermediate isotactic diad content degraded in a continuous steady fashion at a rate that was less than that for bacterial PHB. The low isotactic diad fraction underwent a rapid initial degradation, followed by no further mass loss. The presence of stereoblocks in the polymer structure of the various fractions was an influence on the degree of susceptibility towards degradation and is related to sample crystallinity.     

Reproduction of mallards following overwinter exposure to selenium

Forty pairs of mallards (Anas platyrhynchos) were fed 15 ppm selenium as selenomethionine for about 21 weeks during winter. Twenty pairs served as controls. At the end of 21 weeks, which coincided with the onset of the reproductive season, selenium treatment was ended. Four birds died while on selenium treatment. Treated females lost weight, and their egg-laying was delayed. Hatching success of some of the first eggs laid by selenium-treated females was lower than that of controls, and a few of these early eggs contained deformed embryos, but, after a period of about two weeks off the selenium-treated diet, reproductive success returned to a level comparable with that of controls. The return to normal reproductive success was the result of a corresponding decrease in selenium concentrations in eggs once selenium treatment ended.     

Petroleum and hazardous chemical spills in Newark Bay, New Jersey, USA from 1982 to 1991

Newark Bay, New Jersey, is particularly vulnerable to ecological damage from petroleum and chemical spills, as a result of the enclosed nature and shallow depth of the bay, the high frequency of shipping traffic, and the numerous chemical and petroleum transfer terminals located alongs its shores. To evaluate the potential impacts to the natural resources of this coastal estuarine ecosystem, chemical and petroleum accidents reported to the US Coast Guard (USCG) between 1982 and 1991 were compiled to determine the frequency and volume of these incidents in Newark Bay and in each of its major tributaries. Records obtained from the USCG National Response Center's computerized database indicated that more than 1453 accidental incidents, resulting in the release of more than 18 million US gallons of hazardous materials and petroleum products, occurred throughout Newark Bay during this period of time. The bulk of the materials released to the aquatic environment consisted of petroleum products, specifically No. 6 Fuel Oil (103 spills, 12 829 272 US gal) and gasoline (207 spills, 48 816 US gal). The majority of the reported incidents occurred in the Arthur Kill and its tributaries, as well as in the Kill Van Kull and the Passaic River. The results of this study indicated that the accidental discharge of petroleum and hazardous chemicals represents a significant source of chemical pollution in Newark Bay. Based on the frequency of spills and the volume of materials released to the aquatic environment, it is likely that these events are having a deleterious effect on the Newark Bay ecosystem.