The total sedimentation rate was measured fortnightly for a year in a large shallow lake (Lough Neagh, Northern Ireland, surface area 383 km 2 , mean depth 8.9 m) at five sites using 10 sediment traps. The total sedimentation rate included both primary and secondary sedimentation. As the annual average total sedimentation rate, 53.2 Ϯ 44.1 g m Ϫ2 d Ϫ1 , is more than 25 times the primary value, secondary sedimentation due to wind-induced resuspension is very important. The average of the largest 30% of wave mixed layer (WML) values, a function of wind speed and effective fetch, strongly correlates with the total sedimentation rate (r 2 values of 0.69 and 0.98 at two westerly sites) at most of the sites. As the WML value approaches the water depth, then the orbital motion of the waves and the associated turbulence cause sediment disturbance and resuspension. Changing WML values, then, provide a basis to describe the ''random redistribution'' (RR) of sediment in lakes and these resuspension events can occur as frequently as 2-3 times every two weeks. This study provides, for the first time, clear results and a description of the process of RR of sediment in a lake, particularly the link between wind and sediment resuspension.

[1] A data set of 49 sediment cores from 41 lakes in the United Kingdom and Ireland was used to investigate how the variability of anthropogenic Pb concentration and accumulation rate affects using lake sediments to reconstruct Pb contamination of the atmosphere at the regional scale. The anthropogenic Pb concentration, when averaged over six to eleven lakes in subregions, was sufficient to isolate the trend in Pb contamination of the atmosphere since 1850 from lake-specific influences. While the anthropogenic Pb accumulation rate varied considerably within subregions, as a result mainly of variable sediment focusing, the results showed that the maximum focusing factor is typically 1.5 to 3 and rarely above 4. Careful application of this finding may allow the history and geographical variation of Pb deposition from the atmosphere at the regional and global scales to be described using lake sediments. A model that relates anthropogenic Pb concentration in lake sediment to Pb flux from the atmosphere was developed and used to reconstruct Pb flux from the atmosphere in three subregions; the reconstructed flux varies from 2.7 ± 0.9 to 18.9 ± 5.2 mgPb m À2 yr À1 across the subregions in 1860-1870 to 7.4 ± 2.1 to 34.5 ± 6.0 mgPb m À2 yr À1 in 1940-1950.

The Oona Water (102 km 2 ) is a tributary of the Blackwater River (1,480 km 2 ), an Irish cross border catchment and the largest of the six influent rivers to Lough Neagh. An intensive investigation into the magnitude of phosphorus and sediment transfers from field (0.15 km 2 ), farm (0.62 km 2 ) and landscape (84.50 km 2 ) scale sub-catchments showed that total phosphorus transfers were 1.73, 1.82 and 2.50 kg/ha, respectively, during the 2001-2002 hydrological year. Two important features of these data were noted. Firstly, higher transfers from the landscape scale sub-catchment were related to phosphorus inputs between storm events. These were mainly in the soluble form and maintained the river in a hypertrophic state during low flow despite there being no major point source discharges in the catchment. A mass P balance estimate of all domestic wastewater effluents indicated that this is a minor source but may have major impacts at extreme low flows. Secondly, despite the Oona Water being a grassland catchment the main phosphorus fraction recorded was in the particulate form (>50%) and strongly correlated with suspended sediments (SSs), manganese and iron during both storm and non-storm periods. Previous Irish studies have indicated that the main edge-of-field phosphorus transfers from grassland soils are in the soluble form. While erosive overland flow cannot be ruled out from soils of low permeability in the Oona Water, it is also likely that soluble P is entrained to equilibrium by manganese and iron rich SSs from multiple sources that will include stream bank and bed sediments.

The lack of Australian species data has pragmatically led to the use of toxicological data from the Northern Hemisphere to develop water-quality guidelines. However, it is unknown whether Australian species and ecosystems are equally as sensitive and if an uncertainty factor is warranted for Australian guideline setting. In the present study, it is hypothesized that an uncertainty factor is not required. This was tested by generating species sensitivity distributions by 2 parametric methods using marine Northern Hemisphere and Australian/New Zealand data. Sufficient acute data were found for only 3 compounds: 4-chlorophenol, phenol, and ammonia. For ammonia and 4-chlorophenol, the 95% species protection levels generated with Australian and Northern Hemisphere data were essentially the same. For phenol, protection levels derived from Australian data were approximately 10-fold higher. Therefore, the derived benchmark concentration from Northern Hemisphere data should be protective. It is tentatively concluded that there is no need for an uncertainty factor when deriving water-quality guidelines for marine Australian ecosystems using Northern Hemisphere data. It is, however, noted that this is based on only 3 compounds.

Separate phases of metal partitioning behaviour in freshwater lakes that receive varying degrees of atmospheric contamination and have low concentrations of suspended solids were investigated to determine the applicability of the distribution coefficient, K D. Concentrations of Pb, Ni, Co, Cu, Cd, Cr, Hg and Mn were determined using a combination of filtration methods, bulk sample collection and digestion and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Phytoplankton biomass, suspended solids concentrations and the organic content of the sediment were also analysed. By distinguishing between the phytoplankton and (inorganic) lake sediment, transient variations in K D were observed. Suspended solids concentrations over the 6-month sampling campaign showed no correlation with the K D (n = 15 for each metal, p > 0.05) for Mn (r 2 = 0.0063), Cu (r 2 = 0.0002, Cr (r 2 = 0.021), Ni (r 2 = 0.0023), Cd (r 2 = 0.00001), Co (r 2 = 0.096), Hg (r 2 = 0.116) or Pb (r 2 = 0.164). The results implied that colloidal matter had less opportunity to increase the dissolved (filter passing) fraction, which inhibited the spurious lowering of K D. The findings conform to the increasingly documented theory that the use of K D in modelling may mask true information on metal partitioning behaviour. The root mean square error of prediction between the directly measured total metal concentrations and those modelled based on the separate phase fractions were ± 3.40, 0.06, 0.02, 0.03, 0.44, 484.31, 80.97 and 0.1 μg/L for Pb, Cd, Mn, Cu, Hg, Ni, Cr and Co respectively. The magnitude of error suggests that the separate phase models for Mn and Cu can be used in distribution or partitioning models for these metals in lake water.