James W. Readman

Nanoparticle analysis and characterization methodologies in environmental risk assessment of engineered nanoparticles

Environmental risk assessments of engineered nanoparticles require thorough characterization of nanoparticles and their aggregates. Furthermore, quantitative analytical methods are required to determine environmental concentrations and enable both effect and exposure assessments. Many methods still need optimization and development, especially for new types of nanoparticles in water, but extensive experience can be gained from the fields of environmental chemistry of natural nanomaterials and from fundamental colloid chemistry. This review briefly describes most methods that are being exploited in nanoecotoxicology for analysis and characterization of nanomaterials. Methodological aspects are discussed in relation to the fields of nanometrology, particle size analysis and analytical chemistry. Differences in both the type of size measures (length, radius, aspect ratio, etc.), and the type of average or distributions afforded by the specific measures are compared. The strengths of single particle methods, such as electron microscopy and atomic force microscopy, with respect to imaging, shape determinations and application to particle process studies are discussed, together with their limitations in terms of counting statistics and sample preparation. Methods based on the measurement of particle populations are discussed in terms of their quantitative analyses, but the necessity of knowing their limitations in size range and concentration range is also considered. The advantage of combining complementary methods is highlighted.

Antifouling paint booster biocides in the UK coastal environment and potential risks of biological effects.

In the yachting sector of the UK antifouling market, organic biocides are commonly added to antifouling preparations to boost performance. Few data presently exist for concentrations of these compounds in UK waters. In this study the concentrations of tributyltin (TBT) and eight booster biocides were measured before and during the 1998 yachting season. The Crouch Estuary, Essex, Sutton Harbour, Plymouth and Southampton Water were chosen as representative study sites for comparison with previous surveys of TBT concentrations. Diuron and Irgarol 1051 were the only organic booster biocides found at concentrations above the limits of detection. Diuron was measured at the highest concentrations, whilst detectable concentrations of both Irgarol 1051 and diuron were determined in areas of high yachting activity (e.g. mooring areas and marinas). Maximum measured values were 1,421 and 6,740 ng/l, respectively. Lower concentrations of both compounds were found in open estuarine areas, although non-antifouling contributions of diuron may contribute to the overall inputs to estuarine systems. TBT was found to be below or near the environmental quality standard (EQS) of 2 ng/l for all samples collected from estuarine areas frequented by pleasure craft alone, but with much higher concentrations measured in some marinas, harbours and in areas frequented by large commercial vessels. Using the limited published environmental fate and toxicity data available for antifouling booster biocides, a comparative assessment to evaluate the risk posed by these compounds to the aquatic environment is described. TBT still exceeds risk quotients by the greatest margins, but widespread effects due to Irgarol 1051 and less so diuron cannot be ruled out (particularly if use patterns change) and more information is required to provide a robust risk assessment.

Changes in the sedimentary organic carbon pool of a fertilized tropical estuary, Guanabara Bay, Brazil: an elemental, isotopic and molecular marker approach

Sediments from Guanabara Bay, sampled as short-cores (50–60 cm) from eight stations, were analysed for the elemental (C and N), isotopic (δ13C and δ15N) and molecular composition (steroids) of the organic matter. The objective of this study was to examine whether there are changes in the sources of sedimentary organic matter pool due to increasing N, P and particulate loads to the bay over the last 100 years. On average, we found a 10-fold increase in the flux of organic matter to the sediments with a maximum of 41.7 mol C m−2 year−1. C/N and δ13C time–space distribution and mass balance calculations indicate that the organic material results from a mixture of marine, terrestrial and estuarine sources, with a growing predominance of autochthonous inputs in recent years. Dinosterol was predominant in most samples (>50% of all measured sterols). Concentrations of dinosterol increased significantly in the last two decades and reached values as high as 150 μg g−1 dry sediment. Net increases in concentration were estimated using the first-order decay rate constants derived from experimental data. There are strong indications that an increase in carbon storage occurred in response to growing eutrophic conditions. In spite of the high respiration rates occurring in the water column, fast sedimentation rates result in the transfer of a significant carbon fraction to the anoxic sediments. Further decomposition proceeds only in the first 10 cm of sediment as indicated by the decay rates.

Improved removal of estrogenic and pharmaceutical compounds in sewage effluent by full scale granular activated carbon: Impact on receiving river water

Sewage effluents are widely recognised as the main source of emerging contaminants, such as endocrine disrupting chemicals (EDCs) and pharmaceuticals in surface waters. A full-scale granular activated carbon (GAC) plant has been installed as an advanced technology for the removal of these contaminants, in a major sewage treatment works (STW) in South-West England as part of the UK National Demonstration Programme for EDCs. This study presented for the first time, an assessment of the impact of a recently commissioned, post-tertiary GAC plant in the removal of emerging contaminants in a working STW. Through regular sampling followed by solid-phase extraction and analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS), a significant reduction in the concentrations of steroidal estrogens was observed (>43-64%). In addition, significant reductions were observed for many of the pharmaceutical compounds such as mebeverine (84-99%), although the reduction was less dramatic for some of the more widely used pharmaceuticals analysed, including carbamazepine and propranolol (17-23%).

Fluoranthene and pyrene in the suspended particulate matter and surface sediments of the Humber Estuary, UK

Abstract As part of the UK-based Land-Ocean Interaction Study (LOIS) community programme, suspended particulate matter (SPM) and surface sediments have been collected from the Humber estuary, which is a large and complex estuarine system on the east coast of England fed by several rivers including the Trent and Ouse. The samples from four surveys were extracted and analysed to determine the levels of anthropogenic organic contaminants such as fluoranthene and pyrene. Their concentrations in SPM and surface sediments ranged from 44 to 1560 ng g −1 dry weight and 13–1969 ng g −1 dry weight, respectively, and displayed no strong seasonal variation. Mean fluoranthene and pyrene concentrations were higher in the Trent than in the Ouse for both SPM and sediment samples, and were elevated at a sewage outfall, suggesting a multiplicity of inputs for these two compounds. Fluoranthene and pyrene on SPM showed no correlation with salinity, although correlations with suspended solids concentrations (SSC) and particulate organic carbon (POC) have been confirmed.

The partition of fluoranthene and pyrene between suspended particles and dissolved phase in the Humber Estuary: a study of the controlling factors

Abstract Particle–water interactions are one of the most important mechanisms controlling the distribution and movement of hydrophobic organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) in aquatic environments (e.g. estuaries and oceans). To accurately predict the transport and fates of hydrophobic contaminants in estuarine and coastal marine environments, the partition coefficient ( K p ) and organic carbon normalised partition coefficient ( K oc ) are widely used in various biogeochemical models. Such partition coefficients may be calculated from the so-called linear free energy relationships between K p , K oc and more easily measured parameters such as the octanol-water partition coefficient ( K ow ). However K p and K oc values measured for real environmental samples of water and particles obtained from seasonal field surveys in the Humber Estuary, UK deviated from such ideals. For example, K P values showed no correlation with the fraction organic carbon content of particles ( f oc ) and instead of being constant, K oc , values varied with f oc . Both K p and K oc were 1–3 orders of magnitude higher than those predicted from the simple equilibrium–partitioning model, but were in good agreement with several other recently published field studies. To improve our understanding of PAH partitioning, the soot carbon (SC) content of particulate samples was measured so that the simple partition model can be extended to incorporate SC. The partition coefficients derived from the extended partition model are very close to the field K p s. The results suggest that PAHs associated with particles are in fact present in the form of soot and soot-like particles that are not subject to particle–water equilibrations. In other words, the PAHs on soot-like particles are extremely strongly bound and not influenced by further partitioning between the particles and water. However, there are still limitations with the extended partition model as it failed to simulate the field K oc values. No correlation was found between the partition coefficients and salinity, which again we attribute to the non-equilibrium nature of the PAHs. However both K p and K oc generally decreased with increasing suspended solids concentrations (SSC) in the estuary. Such a relationship is probably due to the mixing of soot-like permanently suspended particles with resuspended estuarine sedimentary particles at the higher SSC values, and to the increased concentrations of dissolved organic carbon (DOC) associated with increase in SSC. However, it has been shown that DOC concentrations are not a suitable tool for correcting the SSC effect. There is therefore an urgent need to harmonise the laboratory and field approaches for K p measurements.

Sediment-water interactions of natural oestrogens under estuarine conditions

The natural human female hormones oestrone and 17β-oestradiol have been implicated in the disruption of endocrine systems in some wildlife adjacent to sewage effluents. The sorption behaviour of these two compounds under estuarine conditions was studied by spiking either 2.55 μg of oestrone or 2.65 μg of 17β-oestradiol in kinetic experiments. In equilibrium experiments, 3 ng of oestrone or 3.2 ng of 17β-oestradiol was added in each of the centrifuge tubes. Sorption onto sediment particles was relatively slow, with sorption equilibrium being reached in about 70 and 170 h for oestrone and 17β-oestradiol, respectively. The effects of a variety of environmental parameters on sorption were studied including salinity, sediment concentration (SC), the presence of a third phase, particle size and, also, surfactant concentrations. Results show that although salinity did not induce any statistically significant effect on the sorption of 17β-oestradiol, it did statistically enhance the sorption of oestrone, and a salting constant of 0.3 l mol−1 was derived. The partition coefficient for both compounds decreased with increasing sediment concentration, a phenomenon that has been widely reported and attributed to the presence of colloids (which could enhance dissolved concentrations). In this paper, the true partition coefficients for sediment particles (Kptrue) and colloidal particles (Kctrue) have been calculated, and a Kptrue value of 141 and 102 ml g−1 was obtained for oestrone and 17β-oestradiol, respectively. In addition, Kctrue values for oestrone (222×102 ml g−1) and 17β-oestradiol (135×102 ml g−1) were two orders of magnitude higher than their respective Kptrue values, suggesting that the colloidal particles are significantly stronger sorbents for natural oestrogens than sediment particles. Particles of different sizes were found to have different partition coefficients due to the strong relationships between partition coefficients for the two compounds and particulate organic carbon (POC) contents and specific surface areas (SSAs). The presence of a surfactant was shown to reduce the partition coefficients for the two compounds, although its concentrations being used were higher than those normally found in the natural environment.

Inhibition of barnacle settlement by the environmental oestrogen 4-nonylphenol and the natural oestrogen 17β oestradiol

Abstract The present study examines the effect of a known environmental oestrogen, 4-nonylphenol, on the settlement of the cypris larva of the barnacle, Balanus amphitrite . Cypris larvae were exposed to 4-nonylphenol in a nominal concentration range of 0.01–10.0 μg l −1 . Definitive concentrations of 4-nonylphenol in the test solutions were determined by GC/MS. Cyprid settlement was reduced significantly within this concentration range, following incubation at both 25°C and 28°C for 24–48 h. A naturally occurring oestrogen, 17β oestradiol, was used as a positive control, in the concentration range 0.01–10.0 μg l −1 . Larval settlement was inhibited by 17β oestradiol, but the trend was the opposite to that seen with 4-nonylphenol. No evidence of endocrine disruption was demonstrated, but significant inhibition of larval settlement by both 4-nonylphenol and 17β oestradiol indicated that the compounds may have toxic effects at environmentally realistic and naturally occurring concentrations. The potential for endocrine disruption being more significant at different developmental stages in barnacles is discussed.

Dynamic behaviour of polycyclic aromatic hydrocarbons in Brighton Marina, UK

The distribution of polycyclic aromatic hydrocarbons (PAHs) between various phases is fundamental in the control of their movement and impact in the marine environment. In this study samples of water and sediments were regularly collected from Brighton marina, UK, to quantify the intensity, spatial and temporal variations of PAH contamination. The results show clearly that PAH behaviour in marine systems is highly complex, and controlled by the interplay of PAH sources, compound physicochemical properties, water and sediment movement, and field conditions. Levels of total PAHs (16 compounds) in the dissolved phase were found to vary between <2 and 11,400 ng/l, with higher values observed in the winter months. Total PAH concentration in sediment samples varied between 24 and 4710 ng/g dry weight. PAHs in water were dominated by low molecular mass compounds (2-ring), while PAHs in sediments were mainly derived from 2-4 ring compounds. In addition, dissolved concentrations were increased during sediment dredging and after a period of severe rainfall. PAHs in Brighton marina are likely to be from both pyrolytic and petrogenic sources; as a result, field-derived distribution coefficients for individual PAHs between sediment and water tend to follow the equilibrium partition models, although slight exceedance is apparent. The extended partition model incorporating soot carbon has achieved limited success in better predicting PAH behaviour.

An investigation into the effects of silver nanoparticles on antibiotic resistance of naturally occurring bacteria in an estuarine sediment

The aim of this study was to test whether silver nanoparticles (Ag-NPs) released into estuarine environments result in increased antibiotic resistance amongst the natural bacterial population in estuarine sediments. A 50-day microcosm exposure experiment was carried out to investigate the effects of Ag-NPs (50 nm average diameter) on the antibiotic resistance of bacteria in sediments from an estuary in southwest England. Experimental microcosms were constructed using 3.5 kg sediment cores with 20 l of overlaying seawater treated with (final) Ag-NPs concentrations of 0, 50 or 2000 microg l(-1) (n=3). Sediment samples were screened at the end of the exposure period for the presence of bacteria resistant to eight different antibiotics. Multivariate statistical analyses showed that there was no increase in antibiotic resistance amongst the bacterial population in the sediment due to the dosing of the microcosms with Ag-NPs. This study indicates that, under the tested conditions, Ag-NPs released into the coastal marine environment do not increase antibiotic resistance among naturally occurring bacteria in estuarine sediments. These results contrast previous findings where antimicrobial effects of Ag-NPs on key bacterial species in laboratory experiments have been demonstrated, and reasons for this are discussed. The negligible effects demonstrated on bacterial populations under the selected estuarine conditions, provide important information on no observed effect concentrations (NOECs) for environmental regulation.