The relative contribution of sewage and diffuse phosphorus sources in the River Avon catchment, southern England: implications for nutrient management

In order to effectively manage nutrient river load reductions and target remediation strategies, it is important to determine the relative contributions of diffuse and point sources across the river catchment. This study used a geographical information system (GIS) to apply phosphorus (P) export coefficients (obtained from the literature) to 58 water quality monitoring sites across a large, urbanised, mixed land use catchment, typical of southern lowland England (the River Avon, Warwickshire, UK). These coefficients were used to estimate the annual P load at each monitoring site, and also the relative contribution of point source (from sewage treatment works (STW)) and diffuse input (from both livestock and agricultural land use). The estimated annual P loads showed very close agreement (r2=0.98) with the measured total phosphorus (TP) loads. Sites with the highest proportion of P derived from STW had the highest TP concentrations and loads, and also had greater variations between seasons, with elevated P concentrations occurring during the summer months. The GIS model was re-run to determine the effect of an 80% reduction in P output from STW serving over 10,000 people, thereby assessing the effect of implementing the European Union's Urban Waste Water Treatment Directive (UWWTD). The exported TP load was reduced by 52%, but the sites with the highest TP concentrations were still those with the highest proportion of P derived from STW. The GIS model was re-run to estimate the impact of 80% P reductions at a further 11 STW of varying sizes. This reduced the total TP load by only 29 tonnes year-1, but greatly reduced the P concentrations in many highly nutrient contaminated tributaries. The number of sites with P concentrations greater than 1 mg l-1 was cut from 15 (before UWWTD implementation) to 2. These findings suggest that after UWWTD implementation, resources should focus on introducing tertiary sewage treatment at the remaining large STW, before targeting diffuse inputs. This conclusion is also likely to apply to other lowland river catchments in southern England, most of which have similar population densities to the River Avon.     

Refurbishment of Five Ancient Weirs on the River Avon

This paper reviews the work which was carried out during the Avon Weirs Project - from feasibility through site investigation and detailed design, to construction. The design included measures to (a) ensure the stability of the structures against uplift and piping failure, and (b) provide protection to the bank and bed of the river. In addition, the design satisfied the requirement to provide fish passes at all weirs and canoe ramps at Evesham and Chadbury weirs. Most of the funding was provided by the River Avon Weirs'Trust.     

Refurbishment of Control Structures on the River Avon at Strensham Lock

Three control structures at Strensham lock maintain the water level in the upstream pound of the River Avon for navigation, ecology and angling purposes. The National Rivers Authority † , which currently owns the structures, is responsible for their maintenance and for the operation of the vertical-lift sluice gates which are opened to control flooding. Construction work has recently been completed to secure the structures, which were in a poor state of repair and in danger of collapsing. The two sluice structures were completely rebuilt and the weir was modified.
The paper describes the planning, design and construction of the works, which are located within a 'site of special scientific interest'.     

Weak acid concentrations and river chemistry in the tovdal river, southern Norway

Water samples were collected weekly from the Tovdal river at Boen in southern Norway over the period August 1978–December 1979, and were analysed for pH, sulphate, chloride, nitrate, sodium, potassium, calcium, magnesium, ammonium, aluminium, dissolved silica and weak and strong acids. During the 16 month study period, the river pH showed a much smaller than normal seasonal variation, ranging from a maximum of 5.14 to a minimum of 4.64. The general pattern of the variation in the concentration of both the atmosphere-derived species (sulphate, nitrate and ammonium) and the ground-derived alkalis (calcium, magnesium and potassium) was a steady increase during the autumn and winter to a broad peak during the spring, followed by a minimum concentration during the summer. Nitrate and ammonium exhibited some differences from this pattern since they are rapidly metabolized. The peak in the concentration of sulphate and nitrate which occurred in the spring of 1979 was matched by an equivalent increase in the alkalis leached from the ground, indicating that ground interactions were rapid during the snow-melt period. In the autumn of 1979, the sulphate concentration increased to values higher than in the previous autumn, and, since the concentrations of the leached alkalis did not increase by an equivalent amount, the pH decreased.The seasonal variation in the measured weak acid concentration also exhibited a late winter/spring maximum and a summer minimum. The measured weak acid concentration is shown to have the theoretical dependence on the aluminium, silica and ammonium concentrations together with a dependence on the total organic carbon concentration. For data from the Langtjern catchment, this dependence was found to be 2.3 μeq mgC⁻¹, and, with a value of 4.75 μeq mgC⁻¹, the theoretical relationship satisfactorily fitted the weak acid data from the Tovdal in the spring of 1977, and was also consistent with the measurements from the present study. The seasonal variation in the measured weak acid content was largely explained by the variation in the concentration of the inorganic weak acid species.     

Phosphorus release rates from sediments and pollutant characteristics in Han River, Seoul, Korea

The Han River is 469.7-km long and drains a 26219-km(2) watershed. The sediments in the river are highly polluted due to inputs from upstream tributaries as well as partially treated municipal wastewaters that are discharged to the river. The water quality and strategy for control are important because the river is the primary drinking water supply for the City of Seoul, as well as being a major source for irrigation and industrial water. The Jamsil submerged dam partitions the river to isolate an upstream area for drinking water, but also captures sediments. Samples from four sites were studied to determine sediment pollutant concentrations and phosphorus release rates. Phosphorus tends to desorb from sediments when the concentration of overlying water is less than 1.4 mg/l. Water column P concentrations range from 0.04 to 0.1 mg/l, which suggests that sediments will act as a P source. In a series of batch experiments, P was released at approximately 15-20 mg/m(2)week in the winter (1-5 degrees C) and as much as 90 mg/m(2)week in the summer (20-24 degrees C), and is also a function of pH and dissolved oxygen concentration. The sediment total phosphorus concentration, which averages 833 mg/kg, is evenly distributed among non-apatite-P (33%), apatite-P (32%) and residual-P (34%). An equilibrium model is proposed to describe release rate.     

River water quality of the River Cherwell: an agricultural clay-dominated catchment in the upper Thames Basin, southeastern England

The water quality of the River Cherwell and a tributary of it, the Ray, are described in terms of point and diffuse sources of pollution, for this rural area of the upper Thames Basin. Point sources of pollution dominate at the critical ecological low flow periods of high biological activity. Although the surface geology is predominantly clay, base flow is partly supplied from springs in underlying carbonate-bearing strata, which influences the water quality particularly with regards to calcium and alkalinity. The hydrogeochemistry of the river is outlined and the overall importance of urban point sources even in what would normally be considered to be rural catchments is stressed in relation to the European Unions Water Framework Directive. Issues of phosphorus stripping at sewage treatment works are also considered: such stripping on the Cherwell has reduced phosphorus concentrations by about a factor of two, but this is insufficient for the needs of the Water Framework Directive.     

Factors affecting the concentrations of cadmium, zinc, copper and lead in the sediments of the Vesdre River

The main factors influencing Cd, Zn, Cu and Pb concentrations in the sediments of the highly polluted Vesdre River (eastern Belgium) have been investigated. Only negative correlations were demonstrated between the clay content and heavy metals. The composition of the clay minerals could partially explain this paradox. However, the pretreatment of the minerals might influence the geochemical data obtained from analysis. Iron-hydroxides and phosphates seem to be the main sinks for Pb, Cd and Zn whereas organic components might play a less important role.     

Historical changes in lead concentrations in tree-rings of sycamore,oak and Scots pine in north-west England

Lead concentrations in tree rings of sycamore (Acer pseudoplatanus L.), oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) sampled at a parkland in north-west England were measured in wood formed since the mid-1800s. Concentrations of Pb in Scots pine and oak peaked in wood formed between 1900 and 1940, most likely because of Pb accumulation in heartwood, indicating that oak and Scots pine are unsuitable for monitoring temporal changes in Pb deposition at the study site. In contrast, Pb concentrations in sycamore, a species that has similar heartwood and sapwood chemistry, were relatively constant in wood formed between the mid-1800s and 1950. Lead concentrations decreased steadily in sycamore tree rings formed after the 1950s, and decreased more abruptly in wood formed after 1985. This sharp decrease in wood Pb cannot be due to decreases in soil Pb concentration. Stable Pb isotope analysis was used to further investigate Pb patterns in sycamore wood. Excess 206Pb/207Pb ratios in tree-rings of sycamore were relatively constant, approximately 1.17, in wood formed prior to the 1930s, but decreased steadily thereafter reaching a minimum value of approximately 1.16 in wood formed between 1975 and 1985 after which time 206Pb/207Pb ratios increased. This pattern is consistent with changes in Pb isotope ratios measured in peat, sediment and aerosol samples in the UK. However, the magnitude of the decrease in 206Pb/207Pb (largely due to gasoline Pb) is considerably lower than in other studies and our estimates indicate that less than 20% of the total Pb in sycamore wood measured since the mid-1800s is derived from gasoline emissions. A more likely explanation for the pattern of Pb observed in sycamore tree rings is that soil Pb accumulates within rings of the diffuse porous wood over a number of years. Such uptake patterns would result in lower Pb concentrations in the outer (more recently formed) tree rings, which coincide with recent reductions in Pb deposition in the UK. Overall, this study indicates that tree ring chemistry is unsuitable for monitoring historical changes in Pb deposition at the study site.     

Sewage effluent clean-up reduces phosphorus but not phytoplankton in lowland chalk stream (River Kennet, UK) impacted by water mixing from adjacent canal

Information is provided on phosphorus in the River Kennet and the adjacent Kennet and Avon Canal in southern England to assess their interactions and the changes following phosphorus reductions in sewage treatment work (STW) effluent inputs.A step reduction in soluble reactive phosphorus (SRP) concentration within the effluent (5 to 13 fold) was observed from several STWs discharging to the river in the mid-2000s. This translated to over halving of SRP concentrations within the lower Kennet. Lower Kennet SRP concentrations change from being highest under base-flow to highest under storm-flow conditions. This represented a major shift from direct effluent inputs to a within-catchment source dominated system characteristic of the upper part to the catchment. Average SRP concentrations in the lower Kennet reduced over time towards the target for good water quality. Critically, there was no corresponding reduction in chlorophyll-a concentration, the waters remaining eutrophic when set against standards for lakes.Following the up gradient input of the main water and SRP source (Wilton Water), SRP concentrations in the canal reduced down gradient to below detection limits at times near its junction with the Kennet downstream. However, chlorophyll concentrations in the canal were in an order of magnitude higher than in the river. This probably resulted from long water residence times and higher temperatures promoting progressive algal and suspended sediment generations that consumed SRP. The canal acted as a point source for sediment, algae and total phosphorus to the river especially during the summer months when boat traffic disturbed the canal's bottom sediments and the locks were being regularly opened. The short-term dynamics of this transfer was complex. For the canal and the supply source at Wilton Water, conditions remained hypertrophic when set against standards for lakes even when SRP concentrations were extremely low.     

Phosphorus load estimation in the Saginaw River, MI using a Bayesian hierarchical/multilevel model

We propose the use of Bayesian hierarchical/multilevel ratio approach to estimate the annual riverine phosphorus loads in the Saginaw River, Michigan, from 1968 to 2008. The ratio estimator is known to be an unbiased, precise approach for differing flow-concentration relationships and sampling schemes. A Bayesian model can explicitly address the uncertainty in prediction by using a posterior predictive distribution, while in comparison, a Bayesian hierarchical technique can overcome the limitation of interpreting the estimated annual loads inferred from small sample sizes by borrowing strength from the underlying population shared by the years of interest. Thus, by combining the ratio estimator with the Bayesian hierarchical modeling framework, long-term loads estimation can be addressed with explicit quantification of uncertainty. Our study results indicate a slight decrease in total phosphorus load early in the series. The estimated ratio parameter, which can be interpreted as flow-weighted concentration, shows a clearer decrease, damping the noise that yearly flow variation adds to the load. Despite the reductions, it is not likely that Saginaw Bay meets with its target phosphorus load, 440 tonnes/yr. Throughout the decades, the probabilities of the Saginaw Bay not complying with the target load are estimated as 1.00, 0.50, 0.57 and 0.36 in 1977, 1987, 1997, and 2007, respectively. We show that the Bayesian hierarchical model results in reasonable goodness-of-fits to the observations whether or not individual loads are aggregated. Also, this modeling approach can substantially reduce uncertainties associated with small sample sizes both in the estimated parameters and loads.     

Vernacular Roof-Types in North Avon and South Gloucestershire

Abstract

The article gives a detailed account of examples, mostly dating from the early seventeenth century, of domestic wall painting on plaster, at sites along the seaboard plain of north Lancashire, which are set within the context of earlier work on such painting. Included are an heraldic representation, at Woodplumpton; and three instances of painted representations of structural features, at Fleetwood, Southport and Pilling. The last-named, where there is the representation of parts of a timber cruck framing is in association with a related, painted date panel.     

Measurement and distribution of various heavy metals in the Danube River and Danube Canal aquatic communities in the vicinity of Vienna, Austria.

Samples of mud, water, algae and fish were collected from the Danube River and Danube Canal and analysed by neutron activation techniques for various trace metals. The study was conducted over a ten-months time period. Results show no significant variation in levels of Cr, Co, Sb, Zn, Fe and Sc during the period of study. Comparison of the results obtained for the river with those obtained for the canal indicate that, with the exception of one sampling site, there are no statistically significant differences. Generally the values lie in the range accepted as normal for most fresh water systems. One site in the canal was found to have high Cr content in the mud samples at a point where the Vienna River joins the canal.     

Spatial and temporal trends in nitrate concentrations in the River Derwent, North Yorkshire, and its need for NVZ status

Long-term spatial and temporal variations in nitrate-N concentrations along the River Derwent have been examined using Environment Agency data to investigate the relative importance of impacts of atmospheric N deposition, land use, and changes in management. Where moorland and rough grazing dominate upstream of Forge Valley and Malton, over the 20 years since 1988 mean nitrate-N concentrations were initially increasing significantly, but are now levelling off, with peaks at ca. 4.5 mg N l⁻¹. As expected in a catchment in a nitrate vulnerable zone (NVZ), more agricultural land use increases mean nitrate concentrations and the occurrence of distinct winter maxima, though the latter have become markedly less pronounced since 2001. It is suggested that this improvement is a combined effect of imposition of NVZ designation in the lower reaches in 2002, animal number declines associated with the Foot & Mouth outbreak in the region in 2001, and the impact of farmers' responses to increasing fertilizer prices and to beneficial pollutant mineral N inputs from the atmosphere. Minima in nitrate-N concentrations in summer have become much less pronounced over the past decade and are typically ca. 60% higher in concentration than a decade earlier. This probably is attributable to the effects of pollutant-N leaching to depths in soil below the rooting zone when near surface biotic uptake is low in winter. The resultant N mineralization in summer enhances summer nitrate leaching. The Derwent is a relatively clean river; however, its entire catchment was designated justifiably as a NVZ in January 2009, apparently based upon a projected 95 percentile nitrate-N concentration > 11.29 mg l^− 1 for 2010 based upon forward projection of data from 1990 to 2004 for Derwent Bridge. A survey of water quality in March 2009 showed that some agricultural areas are still making a significant contribution to the total nitrate level well downstream, at the point responsible for implementation of NVZ status. At 3 of the 29 sites sampled, nitrate concentration exceeded 60 mg l^− 1.     

Nutrient hydrochemistry for a groundwater-dominated catchment: the Hampshire Avon, UK

The patterns in nitrate and phosphorus sources, loads and concentrations in a groundwater-dominated lowland catchment, the Hampshire Avon, are examined and water quality signatures are used to identify a typology of headwater stream types. The major separations in water quality are linked to geology and groundwater chemistry as modified by the impacts of point source sewage effluents. The water quality of the major tributaries and the main stem of the River Avon are linked to the relative contributions of these source types, the impact of further direct effluent inputs to the main channel and in-stream processing. The tributaries and main stem of the Avon act as net sinks for total reactive phosphorus (TRP). Low concentrations of TRP were found in the Chalk groundwater and the groundwater system acts as an efficient buffer, removing and retaining TRP from water draining from the catchment surface into the aquifer. Thermodynamic analysis of calcium carbonate (CaCO3) solubility controls indicates that this natural 'self-cleansing mechanism' system within the groundwater may be directly linked to CaCO3-P co-precipitation within the aquifer matrix.     

Orthophosphate concentrations in the River Thames: reductions in the past decade

Ten years ago plans were made to reduce the phosphorus load from sewage-treatment works' effluents into the River Thames. This was driven by the EC Urban Wastewater Treatment Directive in relation to sensitive areas (eutrophic). Modelling work identified the most significant loads to tackle first. Phosphorus removal had been commissioned at 36 works by 2003. The orthophosphate load to the River Thames from these works has reduced from 5755 to 688 kg P/day. The impact of the improvement programme on the quality of the river was assessed by comparing pre- and post-investment data. Orthophosphate concentrations in the river have reduced from between about 0.5 and 2 mg P/L to 0.2 and 0.4 mg P/L. These observations match the model predictions. Chlorophyll a concentrations in the river have also reduced. This was unexpected given that the orthophosphate concentrations still exceed the values thought to be limiting for algal growth.     

灼烧对河道底泥中磷迁移转化特性的影响

研究了灼烧河道底泥过程中磷的环境浸出行为以及磷的潜在活性和生物有效性.结果发现,当灼烧温度为150℃时,溶解性活性磷(SRP)的累计浸出量最大(300.05 mg/kg),而灼烧温度为750 ℃时,SRP的累计浸出量最小(184.33 mg/kg).灼烧强化了底泥中NaOH-nrP和BD-P向NH4C1-P、A1-P、Ca-P的转化.随着灼烧温度升高,这种强化作用明显增加.底泥灼烧温度不同.生物有效磷的形成量也不同.当灼烧温度>550 oC时,生物有效磷的形成受到明显抑制;当灼烧温度为750 ℃时,生物有效磷形成量下降了43.44%.     

江南水乡古镇--乌镇的特色及保护

阐述了江南水乡古镇——乌镇的历史文化特征，从民居、老街、廊棚、桥等多方面，介绍了乌镇的江南水乡风情，并对乌镇的社会文化特征作了分析，提出了古镇的保护措施。     

江南古村落的景观价值及保护利用探讨

对古村落的景观价值进行了研究,分析了古村落环境布局的特点及启迪,提出了古村落景观资源的保护利用措施,以提高人们对古村落的景观价值及保护利用的认识,从而使中国古村落的景观价值、建筑遗产价值和文化价值得到更广泛的关注。     

Long-term changes in mercury concentrations in fish from the middle Savannah River

Total mercury levels were measured in largemouth bass (Micropterus salmoides), sunfish (Lepomis spp.), and catfish (primarily Ameiurus spp. and Ictalurus punctatus) from 1971 to 2004 in the middle Savannah River (river km 191 to 302), which drains the coastal plain of the southeastern U.S. Total mercury concentrations were higher in largemouth bass (overall mean of 0.55 mg/kg from 1971 to 2004), a piscivorous (trophic level 4) species than in the other taxa (means of 0.22-0.26 mg/kg), but temporal trends were generally similar among taxa. Mercury levels were highest in 1971 but declined over the next 10 years due to the mitigation of point source industrial pollution. Mercury levels in fish began to increase in the 1980s as a likely consequence of mercury inputs from tributaries and associated wetlands where mercury concentrations were significantly elevated in water and fish. Mercury levels in Savannah River fish decreased sharply in 2001-2003 coincident with a severe drought in the Savannah River basin, but returned to previous levels in 2004 with the resumption of normal precipitation. Regression models showed that mercury levels in fish changed significantly over time and were affected by river discharge. Mercury levels in Savannah River fish were only slightly lower in 2004 (0.3 to 0.8 mg/kg) than in 1971 (0.4 to 1.0 mg/kg) despite temporal changes during the intervening years.     

Seasonal export of phosphorus from a lowland catchment: upper River Cherwell in Oxfordshire, England

The export of phosphorus from a lowland catchment, the River Cherwell in southern England, was measured over a period of 1 year. The results describe total phosphorus concentrations in the water and river discharge at 4-day intervals. These were used to estimate the load of total phosphorus exported from the catchment. These annual loads were compared with exports estimated from sewage inputs and diffuse inputs calculated from land-coverage data, with assigned phosphorus export coefficients for particular land uses. The method was further developed to examine seasonal changes in phosphorus exports by predicting monthly losses using annual export coefficients normalised with respect to the relative hydraulic runoff for a particular month. The results show a strong seasonal dependence of total exports, with retention of phosphorus in the river system in the spring to early autumn and release of stored material during the winter. This pattern remained true, even with 50% increase in the main land-cover export and a similar increase in treated sewage exports.