DISTRIBUTION OF Cr, Pb, Cu, Cd AND Zn IN SEDIMENTS OF THE DOBCZYCE DAM RESERVOIR (SOUTHERN POLAND)

Sediments play a fundamental role in the behaviour of contaminants in aquatic systems. Various processes in sediments, eg adsorption-desorption, oxidation-reduction, ion exchange or biological activities, can cause accumulation or release of metals and anions from the bottom of reservoirs, and have been recently studied in Polish waters [1-3]. Sediment samples from layer A: (1 divided by 6 cm depth in direct contact with bottom water); layer B: (7 divided by 12 cm depth moderate contact); and layer C: (12+ cm depth, in theory an inactive layer) were collected in September 2007 from six sites representing different types of hydrological conditions along the Dobczyce Reservoir (Fig. l). Water depths at the sampling points varied from 3.5 to 21 m. We have focused on studying the distribution and accumulation of several heavy metals (Cr, Pb, Cd, Cu and Zn) in the sediments. The surface, bottom and pore water (extracted from sediments by centrifugation) samples were also collected. Possible relationships between the heavy-metal distribution in sediments and the sediment characteristics (mineralogy, organic matter) as well as the Fe, Mn and Ca content of sediments, have been studied. The 02 concentrations in water samples were also measured. The heavy metals in sediments ranged from 19.0 to 226.3 mg/kg of dry mass (ppm). The results show considerable variations in heavy-metal concentrations between the 6 stations, but not in the individual layers (A, B, C). These variations are related to the mineralogy and chemical composition of the sediments and their pore waters.

Solutions of a two-dimensional dam-break problem

Solutions of a two-dimensional dam break problem are presented for two tailwater/reservoir height ratios. The numerical scheme used is an extension of one previously given by the author [J. Hyd. Res. 26(3), 293–306 (1988)], and is based on numerical characteristic decomposition. Thus approximate solutions are obtained via linearised problems, and the method of upwind differencing is used for the resulting scalar problems, together with a flux limiter for obtaining a second order scheme which avoids non-physical, spurious oscillations.

Household attributes and the future demand for retirement housing

Ageing populations provoke the question of how much bespoke housing should be provided for the elderly. Older people are generally reluctant to move but as they age health circumstances may encourage moves into specialised accommodation. This paper reports an exercise in estimating the future demand for specialised independent living housing and the extent to which that demand will be for owner occupied accommodation or renting, using data for England. The approach is based on a behavioral model related to health and housing issues. The forecasts indicate a substantial increase in demand, growing at a faster rate than the population as a whole. If supply does not rise to meet these demands, serious problems arise in the quality of life of, and cost of caring for, older people; with implications for health care and social services.

Retirement and succession on the family farm

For farmers, the decision as to when to retire is probably one of the hardest that they will have to face during their working lives. The business of farming brings special circumstances which means that retirement is more often a process than a definitive action. This paper seeks firstly to clarify those special circumstances, and then, by means of flow charts, to identify the key decisions which must be faced if the retirement is to be successful. The practise of handing on the farmland and the other business assets to the next generation are regarded as separate but interrelated stages in the process of retirement, both having legal, financial and human consequences which are considered. By way of conclusion, the parameters for a successful retirement are considered, both from the standpoint of the retirer and of the successor.