Probabilistic impacts of climate change on flood frequency using response surfaces I: England and Wales

The impacts of climate change on hydrology are an important focus of research around the world, but the use of large ensembles to drive impact models is not necessarily straightforward and has to be redone when new projections are released. Here, an alternative sensitivity framework approach is demonstrated, using a set of typical response surfaces alongside the probabilistic UK Climate Projections (UKCP09). These projections comprise sets of 10,000 changes in a number of variables, available for 10 river-basin regions covering England and Wales. Estimates of the potential range of impacts on 20-year return period flood peaks are presented for different types of catchment in each region. Regional average impact ranges are compared for a number of time horizons and emissions scenarios. Results show clear differences in impacts between catchments of different types and between regions. South-East England has the highest impacts with the greatest uncertainty range, while the Dee region has the lowest impacts and smallest uncertainty range. Regional differences are due to both spatial differences in projections and a differing regional balance in the number of catchments of each type. Ease of application of multiple projections is a clear advantage of this sensitivity-based approach to impact assessment, which could be extended to other regions and sectors.     

Restoration of Mountain Big Sagebrush Steppe Following Prescribed Burning to Control Western Juniper

Western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroachment into mountain big sagebrush (Artemisia tridentata spp. vaseyana (Rydb.) Beetle) steppe has reduced livestock forage production, increased erosion risk, and degraded sagebrush-associated wildlife habitat. Western juniper has been successfully controlled with partial cutting followed by prescribed burning the next fall, but the herbaceous understory and sagebrush may be slow to recover. We evaluated the effectiveness of seeding perennial herbaceous vegetation and sagebrush at five sites where juniper was controlled by partially cutting and prescribed burning. Treatments tested at each site included an unseeded control, herbaceous seed mix (aerially seeded), and the herbaceous seed mix plus sagebrush seed. In the third year post-treatment, perennial grass cover and density were twice as high in plots receiving the herbaceous seed mix compared to the control plots. Sagebrush cover and density in the sagebrush seeded plots were between 74- and 290-fold and 62- and 155-fold greater than the other treatments. By the third year after treatment, sagebrush cover was as high as 12 % in the sagebrush seeded plots and between 0 % and 0.4 % where it was not seeded. These results indicate that aerial seeding perennial herbaceous vegetation can accelerate the recovery of perennial grasses which likely stabilize the site. Our results also suggest that seeding mountain big sagebrush after prescribed burning encroaching juniper can rapidly recover sagebrush cover and density. In areas where sagebrush habitat is limited, seeding sagebrush after juniper control may increase sagebrush habitat and decrease the risks to sagebrush-associated species.     

Chemical contaminants in feedlot wastes: concentrations, effects and attenuation

Commercial feedlots for beef cattle finishing are potential sources of a range of trace chemicals which have human health or environmental significance. To ensure adequate protection of human and environmental health from exposure to these chemicals, the application of effective manure and effluent management practices is warranted. The Australian meat and livestock industry has adopted a proactive approach to the identification of best management practices. Accordingly, this review was undertaken to identify key chemical species that may require consideration in the development of guidelines for feedlot manure and effluent management practices in Australia. Important classes of trace chemicals identified include steroidal hormones, antibiotics, ectoparasiticides, mycotoxins, heavy metals and dioxins. These are described in terms of their likely sources, expected concentrations and public health or environmental significance based on international data and research. Androgenic hormones such as testosterone and trenbolone are significantly active in feedlot wastes, but they are poorly understood in terms of fate and environmental implications. The careful management of residues of antibiotics including virginiamycin, tylosin and oxytetracycline appears prudent in terms of minimising the risk of potential public health impacts from resistant strains of bacteria. Good management of ectoparasiticides including synthetic pyrethroids, macrocyclic lactones, fluazuron, and amitraz is important for the prevention of potential ecological implications, particularly towards dung beetles. Very few of these individual chemical contaminants have been thoroughly investigated in terms of concentrations, effects and attenuation in Australian feedlot wastes.     

A Study of Cooling Pond Fog Generation

Airborne particulate and soil materials sampled in the vicinity of a lead/zinc smelter and subsequently digested In nitric-perchloric acids have been analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP/AES). The samples were collected in two communities; a study community situated immediately adjacent to the smelter complex and a control community some 50 kilometers distant. Enrichment of airborne as well as soil materials is discussed and there is evidence of lead, zinc, copper, cadmium, arsenic, and antimony enrichment from the smelting processes. In addition, an aqueous extraction of the airborne materials isolated sulfate, nitrate, fluoride, and ammonia and gave evidence of enrichment due to fugitive SO _x , NO _x , HF, and NH₃ gaseous emissions.     

Evaluation of a “mussel watch” project for heavy metals in Scottish coastal waters

Results are presented of an extensive survey of the heavy metal content of intertidal mussels, Mytilus edulis (L.), from around the Scottish coasts. An important first conclusion is that areas can be identified in which mussels acquire relatively elevated concentrations of certain heavy metals. In general, areas of known pollution display elevated concentrations of several metals, but some areas not greatly influenced by man's activities also show elevated concentrations of a single metal. Comparisons are made of the strategies employed in this and other similar surveys and suggestions made for the design of future exercises.     

Chemical speciation of metals in sediment elutriates

Surface sediments from two localities in Lake Ontario (Hamilton Harbour and Portsmouth Harbour in Kingston, Ontario) were elutriated with lake water. The distribution of chemical species of metals (Fe, Cu, Ni, Pb, Mn, Cd, and Zn) and nutrients (N and P) was investigated in the elutriates and in the lake water by using the computer program geochem and separation by Chelex 100 resin. The concentration of Mn in the water increased from 10^?6.44M to 10^?5.09M during the elutriation of Lake Ontario sediments. The concentrations of other investigated metals were smaller and different in each of the elutriates. Both methods, the calculations by geochem and the separation by Chelex 100, showed that only Mn was present in the four elutriates as a free ion. However, the chemical speciation of other metals by these two methods was only partially similar. All four sediments released significant quantities of NH₃ which was associated in the elutriates mainly with H. The pH of the lake water decreased from 8.4 to 7.5 during the elutriation.     

The Tucker opening-closing micronekton net and its performance in a study of the deep scattering layer

An opening-closing, single-sample net system designed to capture micronektonic organisms is described. The net is opened and closed at the mouth by mechanical time-release devices, and can be hauled from small ships on hydrographic wire. Data are presented from a series of 4 hauls made with this system during a study of sonic scattering layers. The population maxima of euphausiids, sergestid prawns and physonect siphonophores corresponded to the level of the main scattering layer. Fishes were concentrated below the layer, and amphipods above it.     

The effects of a simulated acid precipitation on leaf litter quality and the growth of a detritivore in a buffered lotic system

The effects of a simulated acid rain on leaf litter quality and the growth of a detritivore in a buffered lotic system were investigated. Exposure of Populus balsamifera L. saplings to a simulated acid precipitation prior to leaf abscission resulted in significant decreases in foliar nitrogen content and increases in carbon: nitrogen ratios. During decomposition of the leaf litter in a buffered lotic system, microbial activity was significantly reduced. Growth of Tipula commiscibilis Diane (Diptera: Tipulidae) larvae decreased significantly when fed conditioned leaves exposed to a simulated acid precipitation prior to abscission. Reductions in detritivore growth were correlated with lower potential quality of the leaf litter resulting from increased carbon: nitrogen ratios and reduced levels of microbial activity. Thus, even in well buffered freshwater ecosystems, acid precipitation can have significant indirect effects on microbial activity and macroinvertebrate growth.     

Can adsorption isotherms predict sediment bioavailability?

The adsorption and desorption of 2,4-dichlorophenol (DCP) and pentachlorophenol (PCP) were studied for a range of synthetic particles, a dimethylditallowammonium exchanged clay and a natural sediment. The synthetic particles were Dowex 1X8400, Toyopearl Phenyl 650M and Toyopearl SP 650M. The bioaccumulation of the DCP and PCP from these particles was then studied using the oligochaete, Lumbriculus variegatus. There is a correlation between contaminant-particle interactions, as determined from adsorption and desorption isotherms, and bioaccumulation. Bioaccumulation by L. variegatus was found to be highest from the systems where differences in the classification of adsorption and desorption isotherms were observed.