P.J. Shaw

Separation of molecular size classes of aquatic humic substances using ultrafiltration and dialysis

Abstract A procedure for separating aquatic humic substances into discrete molecular size fractions by the combined use of ultrafiltration and dialysis was tested. The molecular size distributions of separated fractions were examined by application of samples to a gel filtration chromatography column. Variations in the elution patterns observed for the separated fractions of small and intermediate molecular size were largely consistent with predicted effects of separation procedures. In contrast, humic substances of large molecular size were not separated effectively by dialysis using dialysis membranes of large molecular weight cut‐off. Small quantities of humic material of large molecular size were observed in most of the ultrafiltrates. This phenomenon may have been an artefact of filtration and/or the result of reconfiguration of material after separation.

Impacts of phytoplankton activity on dissolved nitrogen fluxes in the tidal reaches and estuary of the Tweed, UK

Monthly surveys were conducted from April to August 1997 to quantify the uptake of dissolved nitrogen species (nitrate, ammonium and urea) and oxygen production in the tidal reaches and estuary of the Tweed. 15N isotope labelling was used in conjunction with in situ incubation methods to determine the uptake of dissolved nitrogen in surface water samples. Respiration, gross and net oxygen production were measured simultaneously. Phytoplankton activity in the Tweed resulted in low rates of dissolved nitrogen uptake (<0.4 nmol N l?1 h?1) and caused small changes in the dissolved oxygen concentration. Uptake of nitrate and urea was associated with phytoplankton biomass and was highest during periods of net autotrophic production (May, June and August). Reductions in the total downstream fluxes of dissolved nitrogen due to phytoplankton activity were appreciable despite the low rates of uptake of dissolved nitrogen and were found to be strongly dependent on the flushing time of the estuary

Applicability and reliability of gel filtration to study aquatic humic substances revisited; The effects of pH on molecular size distributions

Abstract The effect of pH on the molecular size distribution of dissolved humic substances (DHS) in surface waters from four different lakes in northern Europe was studied using Sephadex G‐100 gel filtration chromatography (GFC). New methods for the analysis of the elution profiles obtained are introduced, employing parallel graphical and statistical approaches. For all samples investigated, the proportion of the DHS eluted in the excluded fraction tended to diminish with decreasing pH. At the same time, the remaining DHS eluted tended to decrease in apparent molecular size with decreasing pH. Analyses of the elution profiles revealed that the apparent conformational flexibility of the DHS in the samples was greatest for the samples of lowest ionic strength. The applicability and reliability of GFC as a tool for the investigation of aquatic humic substances are discussed.

The effect of acidification on abiotic interactions of dissolved humic substances, iron and phosphate in epilimnetic water from the humex lake Skjervatjern

Abstract The responses to pH of abiotic interactions between dissolved humic substances, iron and phosphate were investigated by examining redistributions of 55FeCl3 and 32PO43− added to epilimnetic lakewater from Lake Skjervatjern. The simultaneous movement of 55Fe and 32P to fractions of 10 000–20 000 and > 100 000 Daltons nominal molecular weight, as indicated by Sephadex gel filtration, diminished in response to decreasing pH. Variations in transformations to larger molecular size fractions with incubation time revealed by gel filtration were erratic, but indicated that transformations of added 55Fe and 32P are complete after circa 24 h. Movement of 32P to particle size fractions (>0.2 μm) was not dependent on pH, whilst transformations of 55Fe to material of particle size increased as pH was lowered. Precipitation of added 55Fe and 32P was minimal at all pH values tested. Responses of precipitation losses to pH were not coincident for both radionuclides.

Nutrient uptake in a highly turbid estuary (the Humber, United Kingdom) and adjacent coastal waters

Surveys were conducted in April and June 1995 to quantify the uptake of dissolved nutrients in a highly turbid estuary (the Humber, United Kingdom) and to determine the factors controlling nutrient uptake rates. A combination of isotope labelling methods were used in conjunction with on-deck incubation techniques to estimate the uptake of dissolved nutrients (PO43−, NH4+, NO3−, and urea) in surface samples collected from coastal waters. Similarly, isotope labelling and laboratory incubgation techniques were employed to estimate dissolved nitrogen uptake (NH4+, NO3−, and urea) in surface samples collected from the estuary mouth. Nutrient uptake rates were at the low end of ranges for coastal and estuarine environments reported in the literature. Concentrations of chlorophyll and the availability of photosynthetically active radiation were identified as potentially important factors controlling the uptake rates of nutrients. Uptake rates of dissolved nitrogen in the Humber mouth appeared to be related to the location of smapling sites. Depletion rates of dissolved nutrients in situ were estimated on the basis of integrated water column nutrient uptake rates and indicated assimilation of up to 16% of nutrients in the entire water column. Estimated depletion rates did not indicate preferential loss of any of the nutrient species investigated.

Source segregation and food waste prevention activities in high-density households in a deprived urban area

A waste audit and a household questionnaire survey were conducted in high-density housing estates in one of the most economically and socially deprived areas of England (Haringey, London). Such areas are under-represented in published research. The study examined source segregation, potential participation in a food waste segregation scheme, and food waste prevention activities in five estates (1034 households). The results showed that: contamination of recyclables containers was low; ca. 28% of the mixed residual wastes weight was recyclable; food waste comprised a small proportion of the waste from these residents, probably because of their relatively disadvantaged economic circumstances; and the recycling profile reflected an intermittent pattern of behaviour. Although the majority of respondents reported that they would participate in a food waste separation scheme, the response rate was low and many responses of dont know were recorded. Municipalities committed to foster improved diversion from landfill need to recognise that there is no quick and easy fix, regardless of local or national aspirations. Lasting and sustained behaviour change requires time and the quality of service provision and associated infrastructure play a fundamental role in facilitating residents to participate effectively in waste management activities that maximise capture of source-segregated materials. Populations in deprived areas that reside in high-rise, high-density dwellings are hard-to-reach in terms of participation in recycling schemes and exceptional efforts and additional resources are usually required to improve performance.

Destined for indecision? A critical analysis of waste management practices in England from 1996 to 2013

European nations are compelled to reduce reliance on landfill as a destination for household waste, and should, in principle, achieve this goal with due recognition of the aims and principles of the waste hierarchy. Past research has predominantly focused on recycling, whilst interactions between changing waste destinies, causes and drivers of household waste management change, and potential consequences for the goal of the waste hierarchy are less well understood. This study analysed Local Authority Collected Waste (LACW) for England, at national, regional and sub-regional level, in terms of the destination of household waste to landfill, incineration and recycling. Information about waste partnerships, waste management infrastructure and collection systems was collected to help identify and explain changes in waste destinies. Since 1996, the proportion of waste landfilled in England has decreased, in tandem with increases in recycling and incineration. At the regional and sub-regional (Local Authority; LA) level, there have been large variations in the relative proportions of waste landfilled, incinerated and recycled or composted. Annual increases in the proportion of household waste incinerated were typically larger than increases in the proportion recycled. The observed changes took place in the context of legal and financial drivers, and the circumstances of individual LAs (e.g. landfill capacity) also explained the changes seen. Where observed, shifts from landfill towards incineration constitute an approach whereby waste management moves up the waste hierarchy as opposed to an attempt to reach the most preferred option(s); in terms of resource efficiency, this practice is sub-optimal. The requirement to supply incinerators with a feedstock over their lifespan reduces the benefits of developing of recycling and waste reduction, although access to incineration infrastructure permits short-term and marked decreases in the proportion of LACW landfilled. We conclude that there is a need for clearer national strategy and co-ordination to inform and guide policy, practice, planning and investment in infrastructure such that waste management can be better aligned with the principles of the circular economy and resource efficiency. If the ongoing stand-off between national political figures and the waste sector continues, Englands waste policy remains destined for indecision.

The effects of a thermal discharge on the macroinvertebrate community of a large British river: implications for climate change.

Anthropogenic changes to the temperature regimes of rivers, whether through thermal pollution, removal of shade, or climate change, could affect community stability and cause phenological changes in aquatic species. This study examines the impact of a thermal discharge from a power station on the diversity and composition of the aquatic macroinvertebrate community in the River Severn, UK. Daily temperatures up to 2xa0km downstream of the thermal discharge averaged 4.5°C above ambient. Abundance and taxon richness metrics were reduced at a site approximately 0.5xa0km downstream of the power station outfall, but were largely unaffected at a second site about 2xa0km downstream. The majority of the macroinvertebrate taxa observed were recorded at both control and heated sites, suggesting species were below their thermal tolerance threshold or had developed adaptations to survive increased temperatures. However, indicator species analysis suggests certain taxa were associated with particular sites; abundances of Musculium lacustre, Simulium reptans, and Orthocladiinae were greater at the unheated control site, whereas more pollution-tolerant species such Asellus aquaticus and Erpobdella octoculata were more common in the thermally impacted reaches. Overall, the results provide an indication of potential species and community response to future warming under climate change scenarios.

CONTRASTING EXPERIMENTAL MANIPULATIONS OF THE ACIDITY OF CATCHMENT DRAINAGE WATER: EFFECTS ON INTERACTIONS BETWEEN HUMIC SUBSTANCES, IRON, AND PHOSPHATE

Abiotic interactions occurring between dissolved humic substances, iron, and phosphate were investigated by addition of radioisotope tracers (55FeCl3 and PO43−) to surface water samples collected from catchments subjected to contrasting pH manipulations. Increases from pH 4 to circumneutral pH due to catchment liming resulted in increases in the proportions of added ionic 55Fe and 32P recovered in higher molecular size fractions following gel chromatography. Changes in ionic composition due to catchment liming did not result in marked changes in redistributions of added 55Fe and 32P. Comparatively small differences between the pH values and ionic compositions of the control and artificially acidified subcatchments of a humic lake did not result in substantial changes in the redistributions of added 55Fe and 32P.

Modeling vessel noise emissions through the accumulation and propagation of Automatic Identification System data

Recent research has demonstrated the importance of soundscape characterization, modeling, and mapping with regard to their potential to highlight noise levels that can adversely affect fish behavior. Models and noise maps are seen as valuable tools for generating comprehensive information at relatively low costs; a model-based approach presents a powerful and cost-effective way to evaluate noise levels. This research aims to develop a vessel noise modeling method using Automatic Identification System (AIS) and online data. The vessel noise map is produced using estimated source levels of individual ships at each AIS transmission point along a vessel transit line. The accumulation and propagation of these transit line emissions, in 1 km grid squares, produces an ocean shipping noise map showing average received levels over the desired time period. The results show temporal and spatial differences in vessel noise emissions, with summer months nosier than winter months, and coastal areas and known shipping channels much nosier than the open ocean. Unlike many previous models, this approach uses individual vessel source emissions, and is very computationally efficient even for large datasets.Recent research has demonstrated the importance of soundscape characterization, modeling, and mapping with regard to their potential to highlight noise levels that can adversely affect fish behavior. Models and noise maps are seen as valuable tools for generating comprehensive information at relatively low costs; a model-based approach presents a powerful and cost-effective way to evaluate noise levels. This research aims to develop a vessel noise modeling method using Automatic Identification System (AIS) and online data. The vessel noise map is produced using estimated source levels of individual ships at each AIS transmission point along a vessel transit line. The accumulation and propagation of these transit line emissions, in 1 km grid squares, produces an ocean shipping noise map showing average received levels over the desired time period. The results show temporal and spatial differences in vessel noise emissions, with summer months nosier than winter months, and coastal areas and known shipping c...