Developing the OECD 106 fate testing protocol for active pharmaceuticals in soil.

The ability to determine accurately the fate of APIs in soil is essential for rigorous risk assessment associated with wastewater reuse or biosolid recycling to land, particularly in lower income countries where water and fertiliser is scarce. Four APIs (naproxen, ofloxacin, propranolol and nevirapine) with wide ranging functionality were used as examples in the development of the OECD 106 soil partitioning and/or degradation study, with naproxen used to illustrate applying the full methodology. The data showed key methodological criteria require careful consideration and testing to generate accurate and consistent results. Only glass fibre membranes were suitable for all APIs, without unduly adsorbing APIs to their surface, thus effectively restricting the minimum practical pore size to 0.7 µm. Polypropylene plastic centrifuge tubes were shown to be suitable, with careful determination of recoveries. Direct injection liquid chromatography-mass spectrometry could reliably resolve all 4 APIs down to less than µg L-1 in soil solutions, although allowance for matrix effects via standard additions was required in some cases. Greatest analytical challenges were found for the highest molecular weight API with the greatest affinity for sorption to surfaces (ofloxacin). Key variables that can impact on partitioning such as solution pH and dissolved organic carbon concentrations were shown to vary within tests over time and should be accounted for.

Determination and Prediction of Zinc Speciation in Estuaries.

Lowering of the estuarine Environmental Quality Standard for zinc in the UK to 121 nM reflects rising concern regarding zinc in ecosystems and is driving the need to better understand its fate and behavior and to develop and parametrize speciation models to predict the metal species present. For the first time, an extensive data set has been gathered for the speciation of zinc within an estuarine system with supporting physicochemical characterization, in particular dissolved organic carbon. WHAM/Model VII and Visual MINTEQ speciation models were used to simulate zinc speciation, using a combination of measured complexation variables and available defaults. Data for the five estuarine transects from freshwater to seawater endmembers showed very variable patterns of zinc speciation depending on river flows, seasons, and potential variations in metal and ligand inputs from in situ and ex situ sources. There were no clear relationships between free zinc ion concentration [Zn2+] and measured variables such as DOC concentration, humic and biological indices. Simulations of [Zn2+] carried out with both models at high salinities or by inputting site specific complexation capacities were successful, but overestimated [Zn2+] in low salinity waters, probably owing to an underestimation of the complexation strength of the ligands present. Uncertainties in predicted [Zn2+] are consistently smaller than standard deviations of the measured values, suggesting that the accuracy of the measurements is more critical than model uncertainty in evaluating the predictions.

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.

Mixtures of tritiated water, zinc and dissolved organic carbon: Assessing interactive bioaccumulation and genotoxic effects in marine mussels, Mytilus galloprovincialis.

Release of tritium (3H) in the marine environment is of concern with respect to its potential bioaccumulation and detrimental impact on the biota. Previous studies have investigated the uptake and toxicity of this radionuclide in marine mussels, and the interaction of 3H with dissolved organic ligands and elevated temperature. However, despite the well-established view that toxicity is partly governed by chemical speciation, and that toxic effects of mixture of contaminants are not always additive, there have been no studies linking the prevailing chemistry of exposure waters with observed biological effects and tissue specific accumulation of 3H in combination with other constituents commonly found in natural waters. This study exposed the marine mussel Mytilus galloprovincialis for 14 days to mixtures of 3H (as tritiated water, HTO) and zinc (Zn) at 5 Mbq L-1, and 383, 1913 and 3825 nM Zn, respectively, to investigate (a) 3H and Zn partitioning in soft tissues of mussels, and (b) DNA damage in haemocytes, determined using the single cell gel electrophoresis or the comet assay. Additionally, the extent of association of 3H with dissolved organic carbon (DOC, added as humic acid) over the exposure period was investigated in order to aid the interpretation of biological uptake and effects. Results concluded a clear antagonistic effect of Zn on 3H-induced DNA damage at all Zn concentrations used, likely explained by the importance of Zn in DNA repair enzymes. The interaction of DOC with 3H was variable, with strong 3H-DOC associations observed in the first 3 d of the experiment. The secretion of 3H-binding ligands by the mussels is suggested as a possible mechanism for early biological control of 3H toxicity. The results suggest risk assessments for radionuclides in the environment require consideration of potential mixture effects.

Development of a chemical source apportionment decision support framework for lake catchment management.

Increasing pressures on natural resources has led to the adoption of water quality standards to protect ecological and human health. Lakes and reservoirs are particularly vulnerable to pressure on water quality owing to long residence times compared with rivers. This has raised the question of how to determine and to quantify the sources of priority chemicals (e.g. nutrients, persistent organic pollutants and metals) so that suitable measures can be taken to address failures to comply with regulatory standards. Contaminants enter lakes waters from a range of diffuse and point sources. Decision support tools and models are essential to assess the relative magnitudes of these sources and to estimate the impacts of any programmes of measures. This paper describes the development and testing of the Source Apportionment Geographical Information System (SAGIS) for future management of 763 lakes in England and Wales. The model uses readily available national data sets to estimate contributions of a number of key chemicals including nutrients (nitrogen and phosphorus), metals (copper, zinc, cadmium, lead, mercury and nickel) and organic chemicals (Polynuclear Aromatic Hydrocarbons) from multiple sector sources. Lake-specific sources are included (groundbait from angling and bird faeces) and hydrology associated with pumped inputs and abstraction. Validation data confirms the efficacy of the model to successfully predicted seasonal patterns of all types of contaminant concentrations under a number of hydrological scenarios. Such a tool has not been available on a national scale previously for such a wide range of chemicals and is currently being used to assist with future river basin planning.

Predicting Copper Speciation in Estuarine Waters-Is Dissolved Organic Carbon a Good Proxy for the Presence of Organic Ligands?

A new generation of speciation-based aquatic environmental quality standards (EQS) for metals have been developed using models to predict the free metal ion concentration, the most ecologically relevant form, to set site-specific values. Some countries such as the U.K. have moved toward this approach by setting a new estuarine and marine water EQS for copper, based on an empirical relationship between copper toxicity to mussels (Mytilus sp.) and ambient dissolved organic carbon (DOC) concentrations. This assumes an inverse relationship between DOC and free copper ion concentration owing to complexation by predominantly organic ligands. At low DOC concentrations, the new EQS is more stringent, but above 162 µM DOC it is higher than the previous value. However, the relationship between DOC and copper speciation is poorly defined in estuarine waters. This research discusses the influence of DOC from different sources on copper speciation in estuaries and concludes that DOC is not necessarily an accurate predictor of copper speciation. Nevertheless, the determination of ligand strength and concentrations by Competitive Ligand Exchange Adsorptive Cathodic Stripping Voltammetry enabled the prediction of the free metal ion concentration within an order of magnitude for estuarine waters by using a readily available metal speciation model (Visual MINTEQ).

The impact of natural and anthropogenic Dissolved Organic Carbon (DOC), and pH on the toxicity of triclosan to the crustacean Gammarus pulex (L.).

Regulatory ecotoxicology testing rarely accounts for the influence of natural water chemistry on the bioavailability and toxicity of a chemical. Therefore, this study identifies whether key omissions in relation to Dissolved Organic Carbon (DOC) and pH have an impact on measured effect concentrations (EC). Laboratory ecotoxicology tests were undertaken for the widely used antimicrobial compound triclosan, using adult Gammarus pulex (L.), a wild-type amphipod using synthetic fresh water, humic acid solutions and wastewater treatment works effluent. The toxicity of triclosan was tested at two different pHs of 7.3 and 8.4, with and without the addition of DOC and 24 and 48hour EC values with calculated 95% confidence intervals calculated. Toxicity tests undertaken at a pH above triclosan's pKa and in the presents of humic acid and effluent, containing 11 and 16mgL(-1) mean DOC concentrations respectively, resulted in significantly decreased triclosan toxicity. This was most likely a result of varying triclosan speciation and complexation due to triclosan's pKa and high hydrophobicity controlling its bioavailability. The mean 48hour EC50 values varied between 0.75±0.45 and 1.93±0.12mgL(-1) depending on conditions. These results suggest that standard ecotoxicology tests can cause inaccurate estimations of triclosan's bioavailability and subsequent toxicity in natural aquatic environments. These results highlight the need for further consideration regarding the role that water chemistry has on the toxicity of organic contaminants and how ambient environmental conditions are incorporated into the standard setting and consenting processes in the future.

Abandoned metal mines and their impact on receiving waters: A case study from Southwest England.

Historic mine sites are a major source of contamination to terrestrial and river environments. To demonstrate the importance of determining the significance of point and diffuse metal contamination and the related bioavailability of the metals present from abandoned mines a case study has been carried out. The study provides a quantitative assessment of a historic mine site, Wheal Betsy, southwest England, and its contribution to non-compliance with Water Framework Directive (WFD) Environmental Quality Standards (EQS) for Cd, Cu, Pb and Zn. Surface water and sediment samples showed significant negative environmental impacts even taking account of the bioavailability of the metal present, with lead concentration in the stream sediment up to 76 times higher than the Canadian sediment guidelines 'Probable Effect Level'. Benthic invertebrates showed a decline in species richness adjacent to the mine site with lead and cadmium the main cause. The main mine drainage adit was the single most significant source of metal (typically 50% of metal load from the area, but 88% for Ni) but the mine spoil tips north and south of the adit input added together discharged roughly an equivalent loading of metal with the exception of Ni. The bioavailability of metal in the spoil tips exhibited differing spatial patterns owing to varying ambient soil physico-chemistry. The data collected is essential to provide a clear understanding of the contamination present as well as its mobility and bioavailability, in order to direct the decision making process regarding remediation options and their likely effectiveness.

Development of a chemical source apportionment decision support framework for catchment management.

EU legislation, including the Water Framework Directive, has led to the application of increasingly stringent quality standards for a wide range of chemical contaminants in surface waters. This has raised the question of how to determine and to quantify the sources of such substances so that measures can be taken to address breaches of these quality standards using the polluter pays principle. Contaminants enter surface waters via a number of diffuse and point sources. Decision support tools are required to assess the relative magnitudes of these sources and to estimate the impacts of any programmes of measures. This work describes the development and testing of a modeling framework, the Source Apportionment Geographical Information System (SAGIS). The model uses readily available national data sets to estimate contributions of a number of nutrients (nitrogen and phosphorus), metals (copper, zinc, cadmium, lead, mercury, and nickel) and organic chemicals (a phthalate and a number of polynuclear aromatic hydrocarbons) from multiple sector sources. Such a tool has not previously been available on a national scale for such a wide range of chemicals. It is intended to provide a common platform to assist stakeholders in future catchment management.