Structural investigations of molecular solutes within nanostructured ionic liquids.

Ionic liquids (ILs) containing sufficiently long alkyl chains form amphiphilic nanostructures with well-defined polar and non-polar domains. Here we have explored the robustness of these amphiphilic nanostructures to added solutes and gained insight into how the nature of the solute and IL ions affect the partitioning of these solutes within the nanostructured domains of ILs. To achieve this, small angle X-ray scattering (SAXS) investigations were performed and discussed for mixtures of 9 different molecular compounds with 6 different ILs containing imidazolium cations. The amphiphilic nanostructure of ILs persisted to high solute concentrations, over 50 mol% of added solute for most 1-butyl-3-methylimidazolium ILs and above 80 mol% for most 1-decyl-3-methylimidazolium ILs. Solute partitioning within these domains was found to be controlled by the inherent polarity and size of the solute, as well as specific interactions between the solute and IL ions, with SAXS results corroborated with IR spectroscopy and molecular dynamics simulations. Molecular dynamics simulations also revealed the ability to induce π+-π+ stacking between imidazolium cations through the use of these added molecular compounds. Collectively, these results provide scope for the selection of IL ions to rationally influence and control the partitioning behaviour of given solutes within the amphiphilic nanostructure of ILs.

Validation and application of a modified QuEChERS method for extracting neonicotinoid residues from New Zealand maize field soil reveals their persistence at nominally hazardous concentrations.

The widespread use of neonicotinoid insecticides is controversial due to their persistence in the environment and concern for the long-term consequences of their use. We present a simple, low-cost method for the sensitive and efficient extraction from soil of thiamethoxam, clothianidin and imidacloprid, the three neonicotinoid insecticides approved in New Zealand as seed coatings. We have validated this method by applying it to uncontaminated soil samples spiked with environmentally relevant concentrations of the three targets. Absolute recoveries were >80% with instrument detection limits <1 ng g-1 wet soil. We also applied the method to soil samples collected from maize fields in New Zealand's North Island and found imidacloprid in 43 out of 45 samples and clothianidin in every one. Mean imidacloprid concentrations varied from 0.5 to 9.4 ng g-1 (wet weight) and clothianidin from 2.1 to 26.7 ng g-1 (wet weight). Imidacloprid concentrations exceed the New Zealand Environmental Protection Agency's Environmental Exposure Limit of 1 ng g-1 (dry weight) at eight of the nine sites sampled. These results are remarkable because we have detected multiple neonicotinoid residues at every site sampled. Imidacloprid residues appear to persist at significant concentrations at five of our sites from an application at least two years previously. This is only the third study to report the presence of neonicotinoid residues in NZ's environment and the first to show that those residues are persistent in the environment at nominally hazardous concentrations.

Leaf Stable Isotope and Nutrient Status of Temperate Mangroves As Ecological Indicators to Assess Anthropogenic Activity and Recovery from Eutrophication.

We measured nitrogen stable isotope values (δ15N), and total phosphorus (%P) and total nitrogen (%N) contents in leaves of the temperate mangrove (Avicennia marina sp. australasica) from three coastal ecosystems exposed to various levels of human impact (Manukau, high; Mangawhai, low; and Waitemata, intermediate) in northern New Zealand. We measured δ15N values around 10‰ in environments where the major terrestrial water inputs are sewage. The highest average total nitrogen contents and δ15N values were found in the Auckland city region (Manukau Harbour) at 2.2%N and 9.9‰, respectively. The lowest values were found in Mangawhai Harbour, situated about 80 km north of Auckland city, at 2.0%N and 5.2‰, respectively. In the Waitemata Harbour, also located in Auckland city but with less exposure to human derived sewage inputs, both parameters were intermediate, at 2.1%N and 6.4‰. Total phosphorus contents did not vary significantly. Additionally, analysis of historical mangrove leaf herbarium samples obtained from the Auckland War Memorial Museum indicated that a reduction in both leaf total nitrogen and δ15N content has occurred over the past 100 years in Auckland's harbors. Collectively, these results suggest that anthropogenically derived nitrogen has had a significant impact on mangrove nutrient status in Auckland harbors over the last 100 years. The observed decrease in nitrogenous nutrients probably occurred due to sewage system improvements. We suggest that mangrove plant physiological response to nutrient excess could be used as an indicator of long-term eutrophication trends. Monitoring leaf nutrient status in mangroves can be used to assess environmental stress (sewage, eutrophication) on coastal ecosystems heavily impacted by human activities. Moreover, nitrogen and phosphorus leaf contents can be used to assess levels of available nutrients in the surrounding environments.