We search for far-infrared (FIR) counterparts of known supernova remnants (SNRs) in the Galactic plane (10 • <| l |< 60 • ) at 70 -500 µm using the Herschel Infrared Galactic Plane Survey (Hi-GAL). Of 71 sources studied, we find that 29 (41 %) SNRs have a clear FIR detection of dust emission associated with the SNR. Dust from 8 of these is in the central region, and 4 indicate pulsar wind nebulae (PWNe) heated ejecta dust. A further 23 have dust emission in the outer shell structures which is potentially related to swept up material. Many Galactic SNe have dust signatures but we are biased towards detecting ejecta dust in young remnants and those with a heating source (shock or PWN). We estimate the dust temperature and mass contained within three PWNe, G11.2−0.3, G21.5−0.9, and G29.7−0.3 using modified blackbody fits. To more rigorously analyse the dust properties at various temperatures and dust emissivity index β, we use point process mapping (PPMAP). We find significant quantities of cool dust (at 20-40 K) with dust masses of M d = 0.34 ± 0.14 M , M d = 0.29 ± 0.08 M , and M d = 0.51 ± 0.13 M for G11.2−0.3, G21.5−0.9, and G29.7−0.3 respectively. We derive the dust emissivity index for the PWN ejecta dust in G21.5−0.3 to be β = 1.4 ± 0.5 compared to dust in the surrounding medium where β = 1.8 ± 0.1.

We calculate dust spectral energy distributions (SEDs) for a range of grain sizes and compositions, using physical properties appropriate for five pulsar wind nebulae (PWNe) from which dust emission associated with the ejecta has been detected. By fitting the observed dust SED with our models, with the number of grains of different sizes as the free parameters, we are able to determine the grain size distribution and total dust mass in each PWN. We find that all five PWNe require large ($\ge 0.1 \, {\rm \mu m}$) grains to make up the majority of the dust mass, with strong evidence for the presence of micron-sized or larger grains. Only two PWNe contain non-negligible quantities of small ($\lt 0.01 \, {\rm \mu m}$) grains. The size distributions are generally well-represented by broken power laws, although our uncertainties are too large to rule out alternative shapes. We find a total dust mass of $0.02\rm {-}0.28 \, {\rm M}_\odot$ for the Crab Nebula, depending on the composition and distance from the synchrotron source, in agreement with recent estimates. For three objects in our sample, the PWN synchrotron luminosity is insufficient to power the observed dust emission, and additional collisional heating is required, either from warm, dense gas as found in the Crab Nebula, or higher temperature shocked material. For G54.1+0.3, the dust is heated by nearby OB stars rather than the PWN. Inferred dust masses vary significantly depending on the details of the assumed heating mechanism, but in all cases large mass fractions of micron-sized grains are required.

Dust destruction by supernovae is one of the main processes removing dust from the interstellar medium (ISM). Estimates of the efficiency of this process, both theoretical and observational, typically assume a shock propagating into a homogeneous medium, whereas the ISM possesses significant substructure in reality. We self-consistently model the dust and gas properties of the shocked ISM in three supernova remnants (SNRs), using X-ray and infrared (IR) data combined with corresponding emission models. Collisional heating by gas with properties derived from X-ray observations produces dust temperatures too high to fit the far-IR fluxes from each SNR. An additional colder dust component is required, which has a minimum mass several orders of magnitude larger than that of the warm dust heated by the X-ray emitting gas. Dust-to-gas mass ratios indicate that the majority of the dust in the X-ray emitting material has been destroyed, while the fraction of surviving dust in the cold component is plausibly close to unity. As the cold component makes up virtually all the total dust mass, destruction timescales based on homogeneous models, which cannot account for multiple phases of shocked gas and dust, may be significantly overestimating actual dust destruction efficiencies, and subsequently underestimating grain lifetimes.

We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar and supernova dust emission. We infer an interstellar dust extinction map with an average A V = 1.08 ± 0.38 mag, consistent with a small contribution ( 22%) to the Crab's overall infrared emission. The Crab's supernova dust mass is estimated to be between 0.032 and 0.049 M (for amorphous carbon grains) with an average dust temperature T dust =41±3 K, corresponding to a dust condensation efficiency of 8-12%. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different interstellar dust corrections, lower SPIRE flux densities, and higher dust temperatures than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V band dust extinction of A V = 0.20 − 0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index α radio =0.297±0.009 and an infrared spectral index α IR =0.429±0.021. We have identified a millimetre excess emission in the Crab's central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab's efficient dust condensation (8-12%) provides further evidence for a scenario where supernovae can provide substantial contributions to the interstellar dust budgets in galaxies.

We search for far-infrared (FIR) counterparts of known supernova remnants (SNRs) in the Galactic plane (360 • in longitude and b = ± 1 • ) at 70 -500 µm with Herschel. We detect dust signatures in 39 SNRs out of 190, made up of 13 core-collapse supernovae (CCSNe), including 4 Pulsar Wind Nebulae (PWNe), and 2 Type Ia SNe. A further 24 FIR detected SNRs have unknown types. We confirm the FIR detection of ejecta dust within G350.1−0.3, adding to the known sample of ∼ 10 SNRs containing ejecta dust. We discover dust features at the location of a radio core at the centre of G351.2+0.1, indicating FIR emission coincident with a possible Crab-like compact object, with dust temperature and mass of T d = 45.8 K and M d = 0.18 M , similar to the PWN G54.1+0.3. We show that the detection rate is higher among young SNRs. We produce dust temperature maps of 11 SNRs and mass maps of those with distance estimates, finding dust at temperatures 15 T d 40 K. If the dust is heated by shock interactions the shocked gas must be relatively cool and/or have a low density to explain the observed low grain temperatures.

Summary 0[ The macro!invertebrate faunas of 56 _lter!beds in 37 sewage works throughout Great Britain were surveyed in relation to the physico!chemical characteristics of the bed environment[ Faunal samples were collected from the surface medium and from the bed e/uent[ Fifty!nine of the beds were sampled twice "autumn and spring#^the others were sampled in the spring only[ 1[ Eighty!seven species were found\ of which 28 occurred in the surface samples[ Of these latter species\ 13 "nine oligochaetes\ eight insects\ four copepods and three mites# were particularly successful\ being widespread and often abundant[ The worm Lumbricillus rivalis\ the moth~y Psychoda alternata and the mite Histiostoma feron! iarum were almost ubiquitous[ 2[ The _lter!bed fauna was essentially hygropetric and microbivorous[ All but one "the predatory mite Platyseius italicus# of the 13 particularly successful species grazed the bio_lm[ 3[ The successful species characteristically had prolonged or frequent periods of reproduction[ Therefore\ they could respond rapidly to changes in the bed environ! ment and they were able to persist despite continuous wash!out from the bed[ 4[ DECORANA ordination indicated that abiotic variables likely to a}ect faunal com! position were principally] the organic loading the bed received\ the amount of bio_lm present\ air temperature\ the size of the bed medium\ and bed age[ All except air temperature are under operational control\ so there is potential for the faunal com! munity structure to be modi_ed\ if required\ by manipulation of the bed environment[ 5[ Classi_cation by TWINSPAN identi_ed the moth~y Psychoda albipennis and the copepod Bryocamptus pygmaeus as indicators of beds that received a low organic loading\ whereas abundant Psychoda alternata "×0999 larvae litre −0 medium# indi! cated more heavily loaded beds[ 6[ The results of the present study emphasize the prime importance of the physico! chemical environment in shaping faunal community structure in sewage _lter!beds[ 7[ The study illustrates how knowledge of the faunal community of sewage _lter!beds and its relationship to the bed environment and to bed performance can potentially aid the management of such beds to improve puri_cation e.ciency or reduce~y nuisance[ Key!words] multivariate analysis\ sewage _lter!bed fauna\ species associations[ Journal of Applied Ecology "0887# 24\ 619Ð636

We present complicated dust structures within multiple regions of the candidate supernova remnant (SNR) the ‘Tornado’ (G357.7−0.1) using observations with Spitzer and Herschel. We use Point Process Mapping, ppmap, to investigate the distribution of dust in the Tornado at a resolution of 8″, compared to the native telescope beams of 5 − 36″. We find complex dust structures at multiple temperatures within both the head and the tail of the Tornado, ranging from 15 to 60 K. Cool dust in the head forms a shell, with some overlap with the radio emission, which envelopes warm dust at the X-ray peak. Akin to the terrestrial sandy whirlwinds known as ‘Dust Devils’, we find a large mass of dust contained within the Tornado. We derive a total dust mass for the Tornado head of 16.7 $\rm M_{\odot }$, assuming a dust absorption coefficient of κ300 =0.56$\, \rm m^2\, kg^{-1}$, which can be explained by interstellar material swept up by a SNR expanding in a dense region. The X-ray, infra-red, and radio emission from the Tornado head indicate that this is a SNR. The origin of the tail is more unclear, although we propose that there is an X-ray binary embedded in the SNR, the outflow from which drives into the SNR shell. This interaction forms the helical tail structure in a similar manner to that of the SNR W50 and microquasar SS433.

Radiocarbon (14C) is a powerful tracer of fossil emissions because fossil fuels are entirely depleted in 14C, but observations of 14CO2 and especially 14CH4 in urban regions are sparse. We present the first observations of 14C in both methane (CH4) and carbon dioxide (CO2) in an urban area (London) using a recently developed sampling system. We find that the fossil fraction of CH4 and the atmospheric concentration of fossil CO2 are consistently higher than simulated values using the atmospheric dispersion model NAME coupled with emission inventories. Observed net biospheric uptake in June–July is not well correlated with simulations using the SMURF model with NAME. The results show the partitioning of fossil and biospheric CO2 and CH4 in cities can be evaluated and improved with 14C observations when the nuclear power plants influence is negligible.