Should a water colour parameter be included in lake total phosphorus prediction models used for the Water Framework Directive?

Under the Water Framework Directive (WFD) lakes are classified according to a variety of criteria. This classification facilitates state of the environment assessments and helps identify work needed to achieve the objectives of the WFD, which are broadly to maintain and/or restore water quality and ecological status at a level recognised as good or high. To achieve high or good status, lakes must meet a criterion for total phosphorus (TP) that is linked to a predicted reference condition value that is derived by various models. Lakes which fail to meet good status may require expensive remedial actions to be undertaken, thus accurate identification of the reference condition TP concentration is vital for effective environmental management. However, the models currently employed could be improved for some regions, particularly those with carbon rich soils. By examining 19 reference condition lakes (i.e. lakes essentially non-impacted by humans) in peaty areas of Scotland, we found that a simple parameter linked to water colour and humic substances was a better predictor of TP than the currently employed models (R(2) 0.585 vs R(2) < 0.01). Therefore, for Scotland and elsewhere, in regions with carbon rich soils and lakes with humic waters the TP predictive models could be improved by development and incorporation of a parameter related to water colour and humic components

Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris.

Biochar is the degradation-resistant product generated by the pyrolysis of organic materials and is produced for the intended use of land application in order to promote carbon sequestration and soil improvement. However, despite the many potential benefits biochar application offers, it is important to quantify any ecological impacts that may result from soil amendment in order to avoid potentially causing negative effects upon soil biota which are crucial in the many ecosystem services provided by soil. Any impacts on earthworms in particular are important to evaluate because of their pivotal role in organic matter breakdown, nutrient cycling and soil formation. In this study, we conducted a series of ecotoxicological assays to determine lethal and sublethal (avoidance, mass change and moisture content) effects of heavy biochar applications that reflect levels that may be used in soil restoration efforts. Two earthworm species, Eisenia fetida, an epigeic species, and Lumbricus terrestris, an anecic species, were utilised as test organisms. Two types of biochar, produced from wheat straw and rice husk feedstocks, respectively, were applied to OECD artificial soil and to a natural soil (Kettering loam) at rates of up to 20% w/w. The influence of biochar application on soil porewater chloride, fluoride and phosphate concentrations was also assessed. The biochar applications induced only a subtle level of avoidance behaviour while effects on survival over a 4-week exposure period were inconsistent. However, death and physical damage to some individual earthworms at high biochar application rates were observed, the mechanisms and processes leading to which should be investigated further. Earthworm development (mean mass change over time) proved to be a more sensitive measure, revealing negative effects on L. terrestris at 10% and 20% (w/w) wheat biochar applications in OECD soil and at 20% (w/w) applications of both biochars in Kettering loam. The moisture content of E. fetida remained remarkably consistent across all treatments (~ 82%), indicating that this is not a sensitive measure of effects. The high rates of biochar application resulted in increased chloride (2 to 3-fold) and phosphate (100-fold) concentrations in simulated soil porewaters, which has important implications for soil fertility and production but also for environmental management

Evaluation and characterisation of metal sorption and retention by drinking water treatment residuals (WTRs) for environmental remediation

Drinking water treatment residuals (WTRs) are wastes generated when water is clarified using aluminium or iron salts. They are increasingly being considered as a resource with potential reuse value, particularly in relation to soil or water remediation. Adsorption–desorption capacity of Al-based (Al-WTR) and Fe-based (Fe-WTR) materials was investigated here for Pb and Zn, both separately and in combination, as a preliminary trial to assess their utility for immobilising contaminant metals in environmental settings. Maximum adsorption observed at the highest test solution concentrations imposed (400 mg/L) was similar for each WTR type and each metal; Al-WTRs sorbed Zn at 3579 mg/kg and Pb at 4025 mg/kg, while Fe-WTRs sorbed Zn and Pb at 3579 mg/kg and 3980 mg/kg, respectively. Equilibrium adsorption data were tested against Langmuir, Freundlich, and Temkin isotherm models, which indicated a substantial reserve capacity for further Pb sorption and that multiple sorption mechanisms were involved. Subsequent desorption tests with 0.001 M CaCl2 solution indicated that &gt; 89.76% of sorbed metal remained sorbed. When in solution together, both metals were strongly sorbed by WTRs, but a slight preference for Pb was observed. The results indicate that WTRs would be very effective immobilising agents if placed in contaminated soil or if used to treat contaminated waters

Evaluating land application of pulp and paper mill sludge: A review

It is estimated that >400 Mt of board and paper are produced globally per year, and that 4.3–40 kg (dw) of sludge like material, pulp and paper mill sludge (PPMS), is generated for every tonne of product. PPMS are now more widely reused in agriculture as a soil amendment due to their high organic content of 40–50% by weight, perceived low toxicity and possible liming capabilities. Within this review article historic and recent literature on PPMS land spreading are combined with knowledge of European and UK regulation to explore the benefits, potential impacts and viability of land spreading PPMS. The review reveals that risks relating to potential N immobilisation in soils post-application can be readily mitigated, if desired, by coapplication of an N source, or even pre-treatment of sludge via composting. The benefits to crops have been demonstrated emphatically, while negative ecological impacts under typical field application rates have not been observed to date. The case is therefore strong for continued land application of the material as an environmentally responsible and sustainable use option. However, there are currently gaps in the literature regarding longer-term implications of PPMS applications in agriculture and in regards to the possible presence of emerging contaminants in some PPMS materials, both of which have been identified as areas that merit further research

Assessing the impacts of land spreading water treatment residuals on the anecic earthworm Lumbricus terrestris, soil microbial activity and porewater chemistry.

Water treatment residuals (WTRs), by-products of drinking water clarification, are increasingly recycled to land to promote circular economy and reduce disposal costs, yet there is a lack of published literature on their effects on soil ecology. In the present study, the effects of WTRs on earthworm growth, soil respiration, and soil porewater chemistry are investigated throughout a seven-week outdoor mesocosm trial. WTRs derived from both aluminium and iron coagulants were applied to a loam soil at 0-20 % (w/w). Additionally, soil from a field that had received long-term WTR applications and that of an adjacent non-treated reference field were included in the study. Earthworm mass increase was significantly higher in all but one laboratory treated soils when compared to the control. Furthermore, a linear regression model can be used to predict increases in weekly soil respiration based on the application rates of both Al and Fe WTRs. In addition, a significant increase in soil respiration was observed from the treated farm soils during the first four weeks of the trial. Measured sodium, magnesium, potassium and iron porewater concentrations were higher in the treated farm soils than reference site soil in a majority of samples, although these differences may be related to land management. Laboratory treated soils had elevated porewater arsenic concentrations (e.g. ~17 µg L-1 in controls vs ~62 µg L-1 in the 20 % w/w Al WTR treatment in week 1), while porewater nickel concentrations were respectively elevated and lowered in Al WTR and Fe WTR amended samples. Overall, observed disturbances to soil ecology were determined to be minimal. This article is protected by copyright. All rights reserved

Growth of non-polar InGaN quantum dots with an underlying AlN/GaN distributed Bragg reflector by metal-organic vapour phase epitaxy

Non-polar (11-20) InGaN quantum dots (QDs) have been grown using a modified droplet epitaxy method by metal-organic vapour phase epitaxy on top of a 15-period AlN/GaN distributed Bragg reflector (DBR) on a-plane GaN pseudo-substrate prepared by epitaxial lateral overgrowth (ELOG), in which the QDs are located at the centre of a ca. 180 nm GaN layer. The AlN/GaN DBR has shown a peak reflectivity of ~80% at a wavelength of ~454 nm with a 49 nm wide, flat stop-band. Variations in layer thicknesses observed by cross-sectional scanning transmission electron microscopy have been identified as the main source of degradation of the DBR reflectivity. The presence of trenches due to incomplete coalescence of the ELOG template and the formation of cracks due to relaxation of tensile strain during the DBR growth may distort the DBR and further reduce the reflectivity. The DBR top surface is very smooth and does not have a detrimental effect on the subsequent growth of QDs. Enhanced single QD emission at 20 K was observed in cathodoluminescence.This work has been funded by the EPSRC (Grant No. EP/H047816/1 and EP/J001627/1).This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.spmi.2015.10.00

Persistent organic pollutants (PCB, DDT, HCH, HCB & BDE) in eels (Anguilla anguilla) in Scotland: current levels and temporal trends.

Eels are an ideal biomonitor for persistent organic pollutants (POPs) because of their high lipid content, longevity and tendency to remain within a defined range during their freshwater life phase. This study investigated concentrations of POPs in eels (Anguilla anguilla) from 30 sites across Scotland, including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (BDEs), DDT (and metabolites), hexachlorocyclohexanes (alpha, beta, gamma-HCH), hexachlorobenzene (HCB), hexachlorobutadiene (HCBD) and pentachlorobenzene. Despite its EU-wide ban approximately 30 years ago, DDT and its derivatives were detected in almost all samples. PCB 153 and 138 were the most widely detected PCB congeners, while BDE 47 was the dominant BDE. Pentachlorobenzene was not detected, while HCBD was detected once only. alpha-HCH, beta-HCH and HCB concentrations were very low (generally <3 microg/kg or below detection). When compared with 1986 and 1995 data, the results revealed considerable decreases in p,p'-DDE concentrations. More drastic reductions were evident for gamma-HCH, reflecting the tightening restrictions on pesticide use imposed over the previous decades

Magnesium oxide loaded mesoporous silica: Synthesis, characterisation and use in removing lead and cadmium from water supplies

Water pollution by potentially toxic elements such as cadmium (Cd) and lead (Pb) is a persistent problem in many parts of the world. It continues to have profound implications for drinking water supplies, wastewater discharge and environmental quality of rivers and lakes. Treatment is routinely needed but is not always accessible or practical for a given location or situation, hence new treatment options are the focus of much research. Nanotechnology has great potential to enhance water purification and decontamination efficiency. Nanomaterials have been shown to efficiently remove organic and inorganic pollutants, including metals, from contaminated waters but they can have a tendency to flocculate and thereby lose removal efficiency. Research aimed at stabilising nanoparticles into matrices such as silica offers a way forward. In this study, mesoporous silica (mSiO2, also referred to as MCM-41) was prepared and loaded with magnesium oxide nanoparticles (MgO-NP) to form a MgO-silica composite (MgO-mSiO2) and characterised using UV–Vis, FTIR, XRD, BET, and SEM techniques. The MgO-NP, mSiO2 and MgO-mSiO2 were then evaluated for their Cd and Pb removal capacity across varying conditions of pH, metal concentration, adsorbent: solution volume ratio and contact time. Sorption data were evaluated using the Freundlich, Langmuir and Temkin isotherm models. The MgO-mSiO2 was found to have a very high sorption capacity across the conditions tested, with >99% Cd removal across pH range 3–9 and >99% Pb removal across pH range 5–9. When tested at pH 6–7, the MgO-mSiO2 achieved nearly 100% adsorption efficiencies across the contact times tested (15–180 min)

Portable X-ray fluorescence (pXRF) analysis of heavy metal contamination in church graveyards with contrasting soil types.

Human remains have been interred in burial grounds since historic times. Although the re-use of graveyards differs from one country, region or time-period to another, over time graveyard soil may become contaminated or enriched with heavy metal elements. This paper presents heavy metal element soil analysis from two UK church graveyard study sites with contrasting necrosols, but similar burial densities and known burial ages dating back to the 16th Century and some possibly older than 1,000 years. Portable X-Ray fluorescence (pXRF) element laboratory-based analyses were undertaken on surface and near-surface soil pellets. Results show elevated levels of Fe, Pb, Mn, Cr, Cu, Zn and Ca in both necrosols when compared with background values. Element concentration anomalies remained consistently higher than background samples down to 2 m , but reduced with distance away from church buildings. Element concentration anomalies are higher in the clay-rich necrosol than in sandy necrosol. Study results implications suggest that long-used necrosols are likely to be more contaminated with heavy-metal elements than similar soil outside graveyards with implications for burial grounds management, adjacent populations and where burial grounds have been deconsecrated and turned to residential dwellings

Multi-scale investigation of uranium attenuation by arsenic at an abandoned uranium mine, South Terras

Detailed mineralogical analysis of soils from the UK’s historical key uranium mine, South Terras, was performed to elucidate the mechanisms of uranium degradation and migration in the 86 years since abandonment. Soils were sampled from the surface (0 – 2 cm) and near-surface (25 cm) in two distinct areas of ore processing activities. Bulk soil analysis revealed the presence of high concentrations of uranium (<1690 ppm), arsenic (1830 ppm) and beryllium (~250 ppm), suggesting pedogenic weathering of the country rock and ore extraction processes to be the mechanisms of uranium ore degradation. Micro-focus XRF analysis indicated the association of uranium with arsenic, phosphate and copper; µ-XRD data confirmed the presence of the uranyl-arsenate minerals metazeunerite (Cu(UO2)2(AsO4)2·8H2O) and metatorbernite (Cu(UO2)2(PO4)2·8H2O) to be ubiquitous. Our data are consistent with the solid solution of these two uranyl-mica minerals, not previously observed at uranium-contaminated sites. Crystallites of uranyl-mica minerals were observed to coat particles of jarosite and muscovite, suggesting that the mobility of uranium from degraded ores is attenuated by co-precipitation with arsenic and phosphate, which was not previously considered at this site