A dose metrics perspective on the association of gold nanomaterials with algal cells.

A single-cell inductively coupled plasma mass spectrometry technique was used to explore the influence of particle properties on the association of nanomaterials (NMs) with algal cells. We investigated the effect of particle size, shape, and surface chemistry [citrate and natural organic matter (NOM) coating] on the association of gold (Au) NMs with algal cells using particle mass, particle number, surface area (SA), and volume-specific surface area (VSSA) as dose metrics. Particle number was found to be a better dose metric than particle mass, SA, and VSSA in view of the strong correlation obtained between the number of associated Au NMs with cells and the number of Au NMs in the exposure medium. When particle number was used as the dose metric, there was no selectivity of Au NM cellular association irrespective of particle size and shape, and the cellular association was proportional to the effective number of particles to which the cells were exposed. The surface chemistry of the Au NMs, however, decreased the level of cellular association of some NMs (60 nm spheres). Particle number is the main element used for the classification of NMs according to the recommended definition for NM by the European Commission. The key finding of our study supports the implementation of this definition for safety purposes.Environmental Biolog

Interaction between a nano-formulation of atrazine and rhizosphere bacterial communities: atrazine degradation and bacterial community alterations.

Environmental Biolog

Engineered nanoselenium supplemented fish diet: toxicity comparison with ionic selenium and stability against particle dissolution, aggregation and release

Transformation of nutrients to their nano-form, such as selenium (Se) engineered nanonutrients (Se-ENNs), is expected to enhance the absorption of the nutrients into fish and increase the efficiency of the feed. However, dissolution, aggregation, and release of ENNs from the feed matrix may decrease the efficiency of the Se-ENNs. In this study, we provided fish feed supplemented with Se-ENNs which do not aggregate or dissolve and the particles are also not released from the feed matrix. As a proof of principle, we compared the toxicity of a diet containing Se-ENNs of two different sizes (60 nm and 120 nm) with diets containing ionic Se. The adverse effects were measured by monitoring the survival rate, acetylcholinesterase (AChE) levels and swimming behavior of zebrafish over 21 days of feeding with either the Se-ENNs or ionic Se supplemented fish diets. The number size distribution of the 60 nm Se-ENNs in the diet was similar to that in MilliQ water, while the size distribution of the 120 nm Se-ENNs in the diet was slightly wider. Ion and particle release from Se-ENNs containing diets in the exposure media was not observed, indicating the stability of the particles in the feed matrices. To determine toxicity, zebrafish (Danio rerio) were nourished using a control diet (without Se and Se-ENNs), Se (sodium selenite) containing diets (with 2.4 or 240 mg Se per kg feed) and Se-ENNs containing diets (with 2.4 or 240 mg Se-ENNs of 60 or 120 nm per kg feed) for 21 days. Both sizes of Se-ENNs were taken up in the fish, however only the 120 nm Se-ENNs were detected in the brains of fish. Zebrafish fed with Se-ENNs supplemented diets (60 and 120 nm) showed normal swimming behavior compared to the control. No significant alteration was determined in the AChE activity of the fish fed with the Se-ENNs supplemented diet. In contrast, feeding the zebrafish with a diet containing 240 mg kg−1 Se led to lethal effects. These observations clearly depict the potential benefits of using Se-ENNs as nutrients in fish feed.Environmental Biolog

Source characterisation and distribution of selected PCBs, PAHs and alkyl PAHs in sediments from the Klip and Jukskei Rivers, South Africa

A study of the distribution of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) utilising 16 priority PAHs, benzo(e)pyrene, perylene, 19 alkylated PAHs and 31 ortho substituted PCBs in South Africa is presented. It was aimed to (a) deduce characteristic contamination patterns for both PCBs and PAHs and (b) provide the first comprehensive dataset for establishment of source characterisation of PCBs and PAHs. This is in line with new South African legislation on mandatory monitoring of PCB and PAH emissions. Bar charts, principal component analysis (PCA) and biplots were utilised to identify signature contamination patterns and distribution of PCBs and PAHs within the Jukskei and Klip Rivers. Sediments from the Jukskei and Klip River catchments both showed distinct contamination signatures for hexa to nonachlorinated PCBs, characteristic of contamination by Aroclor 1254 and 1260 technical mixtures. PCB signature patterns in order of abundance were 138 > 180 > 206 > 153 > 187 > 149 and 138 > 153 > 180 > 149 > 187 > 110 > 170 for the Jukskei and Klip River sediments, respectively. The upstream Alberton point had the highest Σ31 PCB and Σ (parent+alkyl) PAH concentrations in the Klip River of 61 and 6000 μg kg−1 dry weight (dw), respectively. In the Jukskei River, the upstream Marlboro point had the highest Σ31 PCB concentration of 19 μg kg−1 dw and the N14 site recorded the highest Σ (parent+alkyl) PAH concentration of 2750 μg kg−1 dw. PAH concentrations in both the Jukskei and Klip Rivers were significantly higher than the PCB concentrations. Fluoranthene, phenanthrene and pyrene were found in the highest concentrations in both the Jukskei and Klip River sediments. Both the Jukskei and Klip River sediments showed trends of a mixed pyrogenic-petrogenic PAH source contamination