Sampling, storage and laboratory approaches for dissolved organic matter characterisation in freshwaters: Moving from nutrient fraction to molecular-scale characterisation

Recent research has highlighted the importance of dissolved organic matter (DOM) for ecosystem function and because of this paradigm shift, it has become crucial to not only quantify its contribution to river nutrient loads but also to characterise its composition. There has been a significant research effort utilising optical methods, such as fluorescence and UV-Vis spectrophotometry, in order to start exploring DOM character. However, these methods still lack the granularity to understand the chemical composition at the molecular level, which is vital to properly understanding its functional role in freshwater ecosystems. As a direct result, there has been a shift towards including molecular-scale analyses to investigate the in-stream processing of the material. Alongside this, recent methodological advancements, particularly in mass spectrometry are opening new opportunities for probing one of the most complex environmental mixtures. However, in order to fully exploit these opportunities, it is key that the way that samples are collected, processed and stored is considered carefully such that sample integrity is maintained. There are additional challenges when collecting water samples for analysis at molecular scale, for example the ultra-low concentrations of individual compounds within DOM means that the samples are sensitive to contamination. This paper discusses current sample collection, processing and storage protocols for this C, N and P quantification and characterisation in freshwaters, and proposes a new standardised protocol suitable for both nutrient fraction quantification and molecular scale analyses, based on method development and testing undertaken in our UK Natural Environment Research Council large grant programme, characterising the nature, origins and ecological significance of Dissolved Organic Matter IN freshwater Ecosystems (DOMAINE).

Potential exposure of hands inside protective gloves-a summary of data from non-agricultural pesticide surveys

The results of individual surveys are compared and general observations are made about the protective nature of protective gloves. A total of 190 measurements of contamination by involatile components of pesticide products were made inside the gloves. Protective gloves were nearly always found to be contaminated inside, except for public hygiene insecticide uses. Disposable gloves were sometimes used when applying public hygiene insecticides, while gloves worn for other applications were normally re-used. The data suggest that when expressing inner glove exposure as 'amount of product per unit time', the data distributions of the non-zero results appeared similar for all activities except for the application of antifoulings. A median value for all non-zero data was indicated at 1.36mg product per minute; a 75th percentile at 4.21mg min(-1) and a 95th percentile at 71.9mg min(-1), assuming product densities of 1.0g ml(-1). In default of better information, these indicators can be used in health-based risk assessment. A further 47 data related to exposure inside new gloves, and 21 data to deposition on outer gloves. These indicate that in general, gloves provide a reasonable degree of protection to non-agricultural pesticides. Due regard should be paid to 'human factors' when considering contamination inside gloves. When people take off dirty gloves, it is difficult to avoid touching the glove exterior. With gloves off, the subject can touch contaminated surfaces. Donning dirty gloves furnishes an inevitable contact with contamination on the outside of the gloves, and can introduce that contamination inside. A common mode of contamination could contribute to the similar distributions for hand contamination inside gloves, from very different uses.