Inorganic phosphorous availability and mobility in a manufactured soil.

Manufactured soils, created by combining various organic and inorganic waste materials and byproducts, may be tailored to specific applications, providing an alternative to the extraction of natural soils. It is important for them to be capable of supporting plant growth without the need for significant management or fertiliser applications, the over-application of which can have adverse environmental effects. We examined the dynamics of phosphorus (P) transformations within a manufactured soil and the implications for nutrient cycling. A freshly prepared manufactured soil (32.5 % composted green waste, 32.5 % composted bark, 25 % horticultural grit, and 10 % lignite clay) was studied over one year in temperature and moisture controlled mesocosms. Leachate was collected to achieve high-resolution monitoring of leached phosphate concentrations. Initially, leached dissolved inorganic phosphorus (DIP) concentrations were low (0.02 ± 0.01 mg P L-1), before increasing by 160 µg P L-1 d-1 over the first 42 days to 5.57 ± 1.23 mg P L-1. After reaching a maximum concentration, DIP concentrations remained relatively consistent, varying by only 1.67 mg P L-1 until day 270. The increase in leached DIP was likely driven by soil organic matter mineralisation and the cleavage of carbon­phosphorus bonds by the soil microbes to satisfy carbon demand with mineralogical influences, such as a decrease in apatite content, also contributing. Sorption and desorption from soil particles were the processes behind the P loss from the soil, which was followed by slow diffusion and eventual loss via leaching. The fertiliser application on phosphate dynamics resulted in increased DIP leaching. P concentrations observed in the manufactured soil were within the range considered sufficient to support plant growth. However, the mean leached phosphorus concentrations were higher than reported eutrophication thresholds suggesting that these soils may pose a risk to surface waters in their current form.

Temporal variability in nutrient concentrations and loads in the River Tamar and its catchment (SW England) between 1974 and 2004.

This study reports the results from the analyses of a 30-year (1974-2004) river water quality monitoring dataset for NO x -N (NO3-N + NO2-N), NH4-N, PO4-P and SiO2-Si at the tidal limit of the River Tamar (SW England), an agriculturally dominated and sparsely populated catchment. Annual mean concentrations of NH4-N, PO4-P and SiO2-Si were similar to other rural UK rivers, while annual mean concentrations of NO x -N were clearly lower. Estimated values for the 1940s were much lower than for those of post-1974, at least for NO3-N and PO4-P. Flow-weighted mean concentrations of PO4-P decreased by approximately 60 % between 1974 and 2004, although this change cannot be unequivocally ascribed to either PO4-P stripping from sewage treatment work effluents or reductions in phosphate fertiliser applications. Lower-resolution sampling (to once per month) in the late 1990s may also have led to the apparent decline; a similar trend was also seen for NH4-N. There were no temporal trends in the mean concentrations of NO x -N, emphasising the continuing difficulty in controlling diffuse pollution from agriculture. Concentrations of SiO2-Si and NO x -N were significantly and positively correlated with river flows ≤15 m(3) s(-1), showing that diffuse inputs from the catchment were important, particularly during the wet winter periods. In contrast, concentrations of PO4-P and NH4-N did not correlate across any flow window, despite the apparent importance of diffuse inputs for these constituents. This observation, coupled with the absence of a seasonal (monthly) cycle for these nutrients, indicates that, for PO4-P and NH4-N, there were no dominant sources and/or both undergo extensive within-catchment processing. Analyses of nutrient fluxes reveal net losses for NO3-N and SiO2-Si during the non-winter months; for NO3-N, this may be due to denitrification. Areal fluxes of NO x -N from the catchment were towards the higher end of the range for the UK, while NH4-N and PO4-P were closer to the lower end of the ranges for these nutrients. These data, taken together with information on sestonic chlorophyll a, suggest that water quality in the lower River Tamar is satisfactory with respect to nutrients. Analyses of these monitoring data, which were collected at considerable logistical and monetary cost, have revealed unique insights into the environmental behaviour of key nutrients within the Tamar catchment over a 30-year period.

Role of recent climate change on carbon sequestration in peatland systems.

This paper provides information on the impact of recent climate change on carbon sequestration in peatland systems in South West England. This is important because peatlands have the potential to sequester and hold large quantities of anthropogenically released CO2. This paper investigates whether there has been a reduction in the strength of carbon sinks in a valley mire and blanket bog, which occur on the limits of the biogeographical envelop for peatlands in Britain. Past rates of carbon accumulation were calculated from peat depth and the sequential analysis of peat age, bulk density and carbon content from cores taken from valley mire and blanket bog. At the valley mire site contemporary net ecosystem carbon balance (NECB) was calculated by measuring inputs to the peat body, via net primary productivity (NPP), of Sphagna. Losses of C from the peat body were calculated by measuring CH4, and aquatic carbon, calculated from catchment export of particulate and dissolved organic carbon. The study found similar mean rates of carbon accumulation since 1850 of 11.26 t ±â€¯0.68 t CO2e ha-1 yr-1 (307 g C m-2 yr-1) in valley mire and 11.77 t ±â€¯0.88 t CO2e ha-1 yr-1 (321 g C m-2 yr-1) in blanket bog. The mean present-day CO2 sequestration rate for Sphagna on valley mire was calculated to be 9.13 t ±â€¯0.98 t CO2e ha-1 yr-1 (249 g C m-2 yr-1). Both past and contemporary rates of CO2 sequestration were found to be at the maxima of those reported for temperate peatlands. NPP was found to vary according to microform with higher rates of carbon sequestration found in lawn and hummock microforms compared with pools. Our work suggests that recent changes in the climate appear to have had limited impact on the strength of peatland carbon sinks in South West England.

Biochar incorporation increased nitrogen and carbon retention in a waste-derived soil.

The synthesis of manufactured soils converts waste materials to value-added products, alleviating pressures on both waste disposal infrastructure and topsoils. For manufactured soils to be effective media for plant growth, they must retain and store plant-available nutrients, including nitrogen. In this study, biochar applications were tested for their ability to retain nitrogen in a soil manufactured from waste materials. A biochar, produced from horticultural green waste, was added to a manufactured soil at 2, 5 and 10 % (by weight), then maintained at 15 °C and irrigated with water (0.84 mL m-2 d-1) over 6 weeks. Total dissolved nitrogen concentrations in soil leachate decreased by 25.2, 30.6 and 44.0 % at biochar concentrations of 2, 5 and 10 %, respectively. Biochar also changed the proportions of each nitrogen-fraction in collected samples. Three mechanisms for biochar-induced nitrogen retention were possible: i) increased cation and anion exchange capacity of the substrate; ii) retention of molecules within the biochar pore spaces; iii) immobilisation of nitrogen through microbial utilisation of labile carbon further supported by increased soil moisture content, surface area, and pH. Dissolved organic carbon concentrations in leachate were reduced (-34.7 %, -28.9 %, and -16.7 %) in the substrate with 2, 5 and 10 % biochar additions, respectively. Fluorescein diacetate hydrolysis data showed increased microbial metabolic activity with biochar application (14.7 ±â€¯0.5, 25.4 ±â€¯5.3, 27.0 ±â€¯0.1, 46.1 ±â€¯6.1 µg FL g-1 h-1 for applications at 0, 2, 5, and 10 %, respectively), linking biochar addition to enhanced microbial activity. These data highlight the potential for biochar to suppress the long-term turnover of SOM and promote carbon sequestration, and a long-term sustainable growth substrate provided by the reuse of waste materials diverted from landfill.

The role of alkalinity in setting water quality metrics: phosphorus standards in United Kingdom rivers.

UK implementation of the European Union Water Framework Directive (for the 2015-2021 cycle) Ecological Status (ES) classification for river phosphorus is based on the calculation of reference conditions for reactive phosphorus (RP) using river alkalinity measurements. Underpinning this approach is that the alkalinity is primarily from rock weathering and is free of anthropogenic influences. However, the potential contribution of anthropogenic alkalinity needs to be considered and, if possible, quantified. In the rural South West River Basin District of England, 38 river sites were examined with respect to river alkalinity loads in order to test this consideration. At river base flow when RP can cause enhanced algal growth, 9 sites (24%) had effluent alkalinity contributions amounting to 25-49% of the total riverine alkalinity load, while 11 (29%) of the sites received ≥50% of their alkalinity load from effluent. When flows increased above base flow to Q95 flow at these 11 sites, catchment diffuse run-off became the largest load of alkalinity at 9 of the sites, and that at the Q95 flows, combined effluent and diffuse alkalinity loads contributed 68-100% of the total alkalinity load. Anthropogenic alkalinity is likely to be present in diffuse run-off, but it is difficult to apportion alkalinity loads between natural and contaminant sources. It is likely that diffuse loads of alkalinity will dominate on the annual timescales used to assess WFD compliance, even at sites where ground water alkalinity dominates at base river flows. In principle, inclusion of anthropogenic alkalinity in the calculation of ES boundary concentrations for RP may lead to a relaxation of the standards. In practice this may not follow. It is likely that at the river sites used initially to develop the algorithms now used for P standard setting, anthropogenic alkalinity was present, to varying and unknown degrees, and that this alkalinity would have influenced the measured and reference RP and biological metrics on which the P standards are based. Apart from RP, alkalinity is also used to underpin water quality metrics for additional chemical and biological parameters, and for this reason, understanding the complex factors determining river alkalinity loads should be an important task for water quality regulators.

Orthophosphate-P in the nutrient impacted River Taw and its catchment (SW England) between 1990 and 2013.

Excess dissolved phosphorus (as orthophosphate-P) contributes to reduced river water quality within Europe and elsewhere. This study reports results from analysis of a 23 year (1990-2013) water quality dataset for orthophosphate-P in the rural Taw catchment (SW England). Orthophosphate-P and river flow relationships and temporal variations in orthophosphate-P concentrations indicate the significant contribution of sewage (across the catchment) and industrial effluent (upper R. Taw) to orthophosphate-P concentrations (up to 96%), particularly during the low flow summer months when maximum algal growth occurs. In contrast, concentrations of orthophosphate-P from diffuse sources within the catchment were more important (>80%) at highest river flows. The results from a 3 end-member mixing model incorporating effluent, groundwater and diffuse orthophosphate-P source terms suggested that sewage and/or industrial effluent contributes ≥50% of the orthophosphate-P load for 27-48% of the time across the catchment. The Water Framework Directive (WFD) Phase 2 standards for reactive phosphorus, introduced in 2015, showed the R. Taw to be generally classified as Poor to Moderate Ecological Status, with a Good Status occurring more frequently in the tributary rivers. Failure to achieve Good Ecological Status occurred even though, since the early-2000s, riverine orthophosphate-P concentrations have decreased (although the mechanism(s) responsible for this could not be identified). For the first time it has been demonstrated that sewage and industrial effluent sources of alkalinity to the river can give erroneous boundary concentrations of orthophosphate-P for WFD Ecological Status classification, the extent of which is dependent on the proportion of effluent alkalinity present. This is likely to be a European - wide issue which should be examined in more detail.

Bacterio-plankton transformation of diazepam and 2-amino-5-chlorobenzophenone in river waters.

Benzodiazepines are a large class of commonly-prescribed drugs used to treat a variety of clinical disorders. They have been shown to produce ecological effects at environmental concentrations, making understanding their fate in aquatic environments very important. In this study, uptake and biotransformations by riverine bacterio-plankton of the benzodiazepine, diazepam, and 2-amino-5-chlorobenzophenone, ACB (a photo-degradation product of diazepam and several other benzodiazepines), were investigated using batch microcosm incubations. These were conducted using water and bacterio-plankton populations from contrasting river catchments (Tamar and Mersey, UK), both in the presence and absence of a peptide, added as an alternative organic substrate. Incubations lasted 21 days, reflecting the expected water residence time in the catchments. In River Tamar water, 36% of diazepam (p < 0.001) was removed when the peptide was absent. In contrast, there was no removal of diazepam when the peptide was added, although the peptide itself was consumed. For ACB, 61% was removed in the absence of the peptide, and 84% in its presence (p < 0.001 in both cases). In River Mersey water, diazepam removal did not occur in the presence or absence of the peptide, with the latter again consumed, while ACB removal decreased from 44 to 22% with the peptide present. This suggests that bacterio-plankton from the Mersey water degraded the peptide in preference to both diazepam and ACB. Biotransformation products were not detected in any of the samples analysed but a significant increase in ammonium concentration (p < 0.038) was measured in incubations with ACB, confirming mineralization of the amine substituent. Sequential inoculation and incubation of Mersey and Tamar microcosms, for 5 periods of 21 days each, did not produce any evidence of increased ability of the microbial community to remove ACB, suggesting that an indigenous consortium was probably responsible for its metabolism. As ACB degradation was consistent, we propose that the aquatic photo-degradation of diazepam to ACB, followed by mineralization of ACB, is a primary removal pathway for these emerging contaminants. As ACB is photo-produced by several benzodiazepines, this pathway should be relevant for the removal of other benzodiazepines that enter the freshwater environment.

A high resolution temporal study of phytoplankton bloom dynamics in the eutrophic Taw Estuary (SW England).

The Taw Estuary (SW England) is eutrophic as a result of enhanced nutrient inputs from its catchment. However, factors influencing the timing and extent of phytoplankton bloom formation are not fully understood in this system. In this study, high resolution chemical and biological sampling was undertaken in late-winter/spring and summer 2008 in order to gain further insights into bloom dynamics in the Taw Estuary. Temporal variations in chlorophyll a maxima in the upper and middle estuary during summer were controlled by river flow and tidal amplitude, with nutrient limitation probably less important. Concentrations of chlorophyll a were highest during low river flow and neap tides. Increased river flows advected the chlorophyll maximum to the outer estuary, and under highest river discharges, chlorophyll a concentrations were further reduced. This feature was even more pronounced when spring tides coincided with high flows. The main bloom species were the diatoms Asterionellopsis glacialis and Thalassiosira guillardii. Using two multivariate statistical techniques in combination, five distinct physical and biogeochemical states in the Taw estuarine waters were identified. These states can be summarised as: A(1), high chlorophyll a, high temperature, long residence times, nutrient depletion; A(2), strong coastal water influence; B(1), decreasing chlorophyll a, increasing river flow and/or spring tides; B(2), transitional between states A(1) and B(3); B(3), high river flow. It was thus possible to differentiate between contrasting environmental conditions that were either beneficial or detrimental for the development of algal blooms. A conceptual model of diatom - dominated primary production for the Taw Estuary is proposed which describes how physical controls (river flow, tidal state) moderate plankton biomass production in the upper and mid - estuarine regions.

Temporal variability in dynamic and colloidal metal fractions determined by high resolution in situ measurements in a UK estuary.

In recent environmental legislation, such as the Water Framework Directive in the European Union (WFD, 2000/60/EC), the importance of metal speciation and biological availability is acknowledged, although analytical challenges remain. In this study, the Voltammetric In situ Profiler (VIP) was used for high temporal resolution in situ metal speciation measurements in estuarine waters. This instrument simultaneously determines Cd, Cu and Pb species within a size range (ca. <4 nm) that is highly relevant for uptake by organisms. The colloidal metal fraction can be quantified through a combination of VIP measurements and analyses of total dissolved metal concentrations. VIP systems were deployed over tidal cycles in a seasonal study of metal speciation in the Fal Estuary, southwest England. Total dissolved concentrations were 4.97-315 nM Cu, 0.13-8.53 nM Cd and 0.35-5.75 nM Pb. High proportions of Pb (77±17%) and Cu (60±25%) were present as colloids, which constituted a less important fraction for Cd (37±30%). The study elucidated variations in the potentially toxic metal fraction related to river flow, complexation by organic ligands and exchanges between dissolved and colloidal phases and the sediment. Based on published toxicity data, the bioavailable Cu concentrations (1.7-190 nM) in this estuary are likely to severely compromise the ecosystem structure and functioning with respect to species diversity and recruitment of juveniles. The study illustrates the importance of in situ speciation studies at high resolution in pursuit of a better understanding of metal (bio)geochemistry in dynamic coastal systems.

Dissolved silver in European estuarine and coastal waters.

Silver is one of the most toxic elements for the marine microbial and invertebrate community. However, little is known about the distribution and behaviour of dissolved silver in marine systems. This paper reports data on dissolved and sediment-associated silver in European estuaries and coastal waters which have been impacted to different extents by past and present anthropogenic inputs. This is the first extended dataset for dissolved silver in European marine waters. Lowest dissolved silver concentrations were observed in the Gullmar Fjord, Sweden (8.9 +/- 2.9 pM; x +/- 1sigma), the Tamar Estuary, UK (9.7 +/- 6.2 pM), the Fal Estuary, UK (20.6 +/- 8.3 pM), and the Adriatic Sea (21.2 +/- 6.8 pM). Enhanced silver concentrations were observed in Atlantic coastal waters receiving untreated sewage effluent from the city of A Coruna, Spain (243 +/- 195 pM), and in the mine-impacted Restronguet Creek, UK (91 +/- 71 pM). Anthropogenic wastewater inputs were a source of dissolved silver in the regions studied, with the exception of the Gullmar Fjord. Remobilisation of dissolved silver from historically contaminated sediments, resulting from acid mine drainage or sewage inputs, provided an additional source of dissolved silver to the estuaries. The ranges in the log particle-water partition coefficient (K(d)) values of 5-6 were similar for the Tamar and Mero estuaries and agreed with reported values for other estuaries. These high K(d) values indicate the particle reactive nature of silver with oxic sediments. In contrast, low K(d) values (1.4-2.7) were observed in the Fal system, which may have been due to enhanced benthic inputs of dissolved silver coupled to limited scavenging of silver on to sediments rich in Fe oxide.

The use of monitoring data for identifying factors influencing phytoplankton bloom dynamics in the eutrophic Taw Estuary, SW England.

Using the Taw Estuary as an example, data routinely collected by the Environment Agency for England and Wales over the period 1990-2004 were interrogated to identify the drivers of excessive algal growth. The estuary was highly productive with chlorophyll concentrations regularly exceeding 100 microg L(-1), mostly during periods of low freshwater input from the River Taw when estuarine water residence times were longest. However, algal growth in mid estuary was often inhibited by ammonia inputs from the adjacent sewage treatment works. The reported approach demonstrates the value of applying conventional statistical analyses in a structured way to existing monitoring data and is recommended as a useful tool for the rapid assessment of eutrophication. However, future estuarine monitoring should include the collection of dissolved organic nutrient data and targeted high temporal resolution data because the drivers of eutrophication are complex and often very specific to a particular estuary.

Characterisation and quantification of organic phosphorus and organic nitrogen components in aquatic systems: a review.

This review provides a critical assessment of knowledge regarding the determination of organic phosphorus (OP) and organic nitrogen (ON) in aquatic systems, with an emphasis on biogeochemical considerations and analytical challenges. A general background on organic phosphorus and organic nitrogen precedes a discussion of sample collection, extraction, treatment/conditioning and preconcentration of organic phosphorus/nitrogen from sediments, including suspended particulate matter, and waters, including sediment porewaters. This is followed by sections on the determination of organic phosphorus/nitrogen components. Key techniques covered for organic phosphorus components are molecular spectrometry, atomic spectrometry and enzymatic methods. For nitrogen the focus is on the measurement of total organic nitrogen concentrations by carbon hydrogen nitrogen analysis and high temperature combustion, and organic nitrogen components by gas chromatography, high-performance liquid chromatography, gel electrophoresis, mass spectrometry, nuclear magnetic resonance spectrometry, X-ray techniques and enzymatic methods. Finally future trends and needs are discussed and recommendations made.

Simultaneous Determination of Dissolved Organic Carbon and Total Dissolved Nitrogen on a Coupled High-Temperature Combustion Total Organic Carbon-Nitrogen Chemiluminescence Detection (HTC TOC-NCD) System.

The marine biogeochemistries of carbon and nitrogen have come under increased scrutiny because of their close involvement in climate change and coastal eutrophication. Recent studies have shown that the high-temperature combustion (HTC) technique is suitable for routine analyses of dissolved organic matter due to its good oxidation efficiency, high sensitivity, and precision. In our laboratory, a coupled HTC TOC-NCD system with a sample changer was used for the automated and simultaneous determination of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in seawater samples. TOC control software was used for TOC instrument control, DOC data acquisition, and data analysis. TDN data acquisition and manipulation was undertaken under LabVIEW. The combined system allowed simultaneous determination of DOC and TDN in the same sample using a single injection and provided low detection limits and excellent linear ranges for both DOC and TDN. The risk of contamination has been remarkably reduced due to the minimal sample manipulation and automated analyses. The optimised system provided a reliable tool for the routine determination of DOC and TDN in marine waters.

The determination of trace metals in estuarine and coastal waters using a voltammetric in situ profiling system.

This work presents the optimisation, validation and field deployment of a voltammetric in situ profiling (VIP) system for the simultaneous determinations of dynamic Cd(II), Cu(II) and Pb(II) in estuarine and coastal waters. Systematic studies in NaNO3 (as a supporting electrolyte) and seawater, indicated that variations in ionic strength, pH and dissolved oxygen did not affect the response of the instrument, whereas an Arrhenius type temperature response was observed. The VIP instrument allows the determination of 2-3 samples h(-1), and has a detection limit (defined as 3sigma) in seawater for Cd(II): 23 pM, Cu(II): 1.13 nM, and Pb(II): 23 pM. The VIP system accurately measured the total dissolved concentrations of Cd(II), Cu(II) and Pb(II) in two certified reference materials; SLRS-3, a river water, and SLEW-2, an estuarine water. Field evaluation of the instrumentation and analytical methods was achieved through a series of surveys in the Plym Estuary (Devon, UK), from which environmental data are presented.