Microplastic pollution within the marine environment is of pressing concern globally. Accordingly, spatial monitoring of microplastic concentrations, composition and size distribution may help to identify sources and entry pathways, and hence allow initiating focused mitigation. Spatial distribution patterns of microplastics were investigated in two compartments of the southern North Sea by collecting sublittoral sediment and surface water samples from 24 stations. Large microplastics (500−5000 µm) were detected visually and identified using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The remaining sample was digested enzymatically, concentrated onto filters and analyzed for small microplastics (11−500 µm) using Focal Plane Array (FPA) FTIR imaging. Microplastics were detected in all samples with concentrations ranging between 2.8-1188.8 particles kg-1 for sediments and 0.1-245.4 particles m-3 for surface waters. On average 98% of microplastics were <100 µm in sediments and 86% in surface waters. The most prevalent polymer types in both compartments were polypropylene, acrylates/polyurethane/varnish, and polyamide. However, polymer composition differed significantly between sediment and surface water samples as well as between the Frisian Islands and the English Channel sites. These results show that microplastics are not evenly distributed, in neither location nor size, which is illuminating regarding the development of monitoring protocols.

Methane is an important greenhouse gas and tropospheric ozone precursor. Simultaneous observation of ethane with methane can help identify specific methane source types. Aerodyne Ethane-Mini spectrometers, employing recently available mid-infrared distributed feedback tunable diode lasers (DFB-TDL), provide 1 s ethane measurements with sub-ppb precision. In this work, an Ethane-Mini spectrometer has been integrated into two mobile sampling platforms, a ground vehicle and a small airplane, and used to measure ethane/methane enhancement ratios downwind of methane sources. Methane emissions with precisely known sources are shown to have ethane/methane enhancement ratios that differ greatly depending on the source type. Large differences between biogenic and thermogenic sources are observed. Variation within thermogenic sources are detected and tabulated. Methane emitters are classified by their expected ethane content. Categories include the following: biogenic (<0.2%), dry gas (1-6%), wet gas (>6%), pipeline grade natural gas (<15%), and processed natural gas liquids (>30%). Regional scale observations in the Dallas/Fort Worth area of Texas show two distinct ethane/methane enhancement ratios bridged by a transitional region. These results demonstrate the usefulness of continuous and fast ethane measurements in experimental studies of methane emissions, particularly in the oil and natural gas sector.

Recent years have shown the importance of tunable semiconductor lasers in optical sensing. We describe the status quo concerning DFB laser diodes between 760 nm and 3,000 nm as well as new developments aiming for up to 80 nm tuning range in this spectral region. Furthermore we report on QCL between 3 μm and 16 μm and present new developments. An overview of the most interesting applications using such devices is given at the end of this paper.

Abstract. Recently apatite-type phases (e.g. La10_x(Si/Ge)6026_+z) have been attracting significant interest due to their high oxide ion conduction. In the case of the Ge based systems there is some uncertainty regarding the nature of the conducting phase, whether it is indeed apatite based or cation deficient La2GeOs-type. In this paper we report a detailed investigation of the phase with composition La9.33Ge6026. We show that for synthesis temperatures in the range 1150-1300 ~ the hexagonal apatite-type structure is obtained (a = b = 9.913(4), c = 7.282(4) A), but heating to higher temperatures (> 1300 ~ leads to the occurrence of extra peaks in the XRD pattern around the apatite peaks. Attempts to refine the extra peaks on a monoclinic apatite-type cell have so far proved unsuccessful, and the exact nature of this system is not clear, although the XRD pattern appears to resemble that of an apatite-type phase more closely than that of La2GeOs. In addition to the change in the XRD pattern, there is also a significant change in the oxide ion conductivity. Specifically the activation energy for samples prepared/sintered at high temperatures (1500 ~ is significantly higher than for those prepared/sintered at lower temperatures (1150 ~ The changes observed appear to be due to loss of Ge, and if the sample is heated at high temperature (1500 ~ for several days, the formation of La2GeO5 becomes apparent. This loss of Ge is a significant problem for the possible use of these materials in SOFCs. In addition to the data on L&j.33Ge6026, we also present conductivity data for La2GeO5 and La4GeO8 for comparison.

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