Pesticide Analysis in Vegetables Using QuEChERS Extraction and Colorimetric Detection

A novel combination of extraction and detection methods is demonstrated for pesticide residue analysis in vegetable samples. Acetylcholinesterase (AChE) inhibition was used as a simple colorimetric test for organophosphates/carbamates (OP/C), and was tested with extracts from the widely-used QuEChERS extraction method. In the absence of pesticide, diluted (50% with water) acetonitrile did not inhibit enzyme activity, demonstrating the compatibility of this extraction solvent with the AChE inhibition test. QuEChERS extraction of chlorpyrifos-spiked tomato, spinach and lettuce samples indicated a high sensitivity to OP/C, with AChE inhibition occurring in the ppb range. The applicability of this method combination was tested by screening tomatoes from 18 different sources, including private gardens, farmer’s market venders, and local supermarkets. Tomatoes from one private garden, three “certified naturally grown” farmer’s market venders and two “organic” supermarket source had AChE inhibition significantly above nominally pesticide-free controls, suggesting the presence of OP/C residue. These residues were likely below levels of health concern, as indicated by lack of complete AChE inhibition, and the absence of inhibition upon sample dilution. This study demonstrates that the combination of QuEChERS extraction and AChE-inhibition detection provides a relatively simple and inexpensive alternative for detection of OP/C in vegetable samples

ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo

(abbreviated) We aim to study the inner wind of the well-known AGB star CW Leo. Different diagnostics probing different geometrical scales have pointed toward a non-homogeneous mass-loss process: dust clumps are observed at milli-arcsec scale, a bipolar structure is seen at arcsecond-scale and multi-concentric shells are detected beyond 1". We present the first ALMA Cycle 0 band 9 data around 650 GHz. The full-resolution data have a spatial resolution of 0".42x0".24, allowing us to study the morpho-kinematical structure within ~6". Results: We have detected 25 molecular lines. The emission of all but one line is spatially resolved. The dust and molecular lines are centered around the continuum peak position. The dust emission has an asymmetric distribution with a central peak flux density of ~2 Jy. The molecular emission lines trace different regions in the wind acceleration region and suggest that the wind velocity increases rapidly from about 5 R* almost reaching the terminal velocity at ~11 R*. The channel maps for the brighter lines show a complex structure; specifically for the 13CO J=6-5 line different arcs are detected within the first few arcseconds. The curved structure present in the PV map of the 13CO J=6-5 line can be explained by a spiral structure in the inner wind, probably induced by a binary companion. From modeling the ALMA data, we deduce that the potential orbital axis for the binary system lies at a position angle of ~10-20 deg to the North-East and that the spiral structure is seen almost edge-on. We infer an orbital period of 55 yr and a binary separation of 25 au (or ~8.2 R*). We tentatively estimate that the companion is an unevolved low-mass main-sequence star. The ALMA data hence provide us for the first time with the crucial kinematical link between the dust clumps seen at milli-arcsecond scale and the almost concentric arcs seen at arcsecond scale.Comment: 22 pages, 18 Figures, Astronomy & Astrophysic

[OI]63micron jets in class 0 sources detected by Herschel

We present Herschel PACS mapping observations of the [OI]63 micron line towards protostellar outflows in the L1448, NGC1333-IRAS4, HH46, BHR71 and VLA1623 star forming regions. We detect emission spatially resolved along the outflow direction, which can be associated with a low excitation atomic jet. In the L1448-C, HH46 IRS and BHR71 IRS1 outflows this emission is kinematically resolved into blue- and red-shifted jet lobes, having radial velocities up to 200 km/s. In the L1448-C atomic jet the velocity increases with the distance from the protostar, similarly to what observed in the SiO jet associated with this source. This suggests that [OI] and molecular gas are kinematically connected and that this latter could represent the colder cocoon of a jet at higher excitation. Mass flux rates (\.M$_{jet}$(OI)) have been measured from the [OI]63micron luminosity adopting two independent methods. We find values in the range 1-4 10$^{-7}$ Mo/yr for all sources but HH46, for which an order of magnitude higher value is estimated. \.M$_{jet}$(OI) are compared with mass accretion rates (\.M$_{acc}$) onto the protostar and with \.M$_{jet}$ derived from ground-based CO observations. \.M$_{jet}$(OI)/\.M$_{acc}$ ratios are in the range 0.05-0.5, similar to the values for more evolved sources. \.M$_{jet}$(OI) in HH46 IRS and IRAS4A are comparable to \.M$_{jet}$(CO), while those of the remaining sources are significantly lower than the corresponding \.M$_{jet}$(CO). We speculate that for these three sources most of the mass flux is carried out by a molecular jet, while the warm atomic gas does not significantly contribute to the dynamics of the system.Comment: 37 pages and 12 figures, accepted for publication on Astrophysical Journa

First astronomical detection of the CF+ ion

We report the first astronomical detection of the CF+ (fluoromethylidynium) ion obtained by recent observations of its J = 1 - 0 (102.6 GHz), J = 2 - 1 (205.2 GHz), and J = 3 - 2 (307.7 GHz) pure rotational emissions toward the Orion Bar. Our search for CF+, carried out using the IRAM 30m and APEX 12m telescopes, was motivated by recent theoretical models that predict CF+ abundances of a few x E-10 in UV-irradiated molecular regions where C+ is present. The measurements confirm the predictions. They provide support for our current theories of interstellar fluorine chemistry, which suggest that hydrogen fluoride should be ubiquitous in interstellar gas clouds.Comment: 2 pages, 1 figure (uses iaus.sty), to appear in IAU Symposium No. 231, Astrochemistry - Recent Successes and Current Challenges, eds. D. C. Lis, G. A. Blake & E. Herbst (Cambridge Univ. Press

Intermittency in two-dimensional Ekman-Navier-Stokes turbulence

We study the statistics of the vorticity field in two-dimensional Navier-Stokes turbulence with a linear Ekman friction. We show that the small-scale vorticity fluctuations are intermittent, as conjectured by Nam et al. [Phys. Rev. Lett. vol.84 (2000) 5134]. The small-scale statistics of vorticity fluctuations coincides with the one of a passive scalar with finite lifetime transported by the velocity field itself.Comment: 4 pages, 7 figure

Mapping water in protostellar outflows with Herschel: PACS and HIFI observations of L1448-C

We investigate on the spatial and velocity distribution of H2O along the L1448 outflow, its relationship with other tracers, and its abundance variations, using maps of the o-H2O 1_{10}-1_{01} and 2_{12}-1_{01} transitions taken with the Herschel-HIFI and PACS instruments, respectively. Water emission appears clumpy, with individual peaks corresponding to shock spots along the outflow. The bulk of the 557 GHz line is confined to radial velocities in the range \pm 10-50 km/s but extended emission associated with the L1448-C extreme high velocity (EHV) jet is also detected. The H2O 1_{10}-1_{01}/CO(3-2) ratio shows strong variations as a function of velocity that likely reflect different and changing physical conditions in the gas responsible for the emissions from the two species. In the EHV jet, a low H2O/SiO abundance ratio is inferred, that could indicate molecular formation from dust free gas directly ejected from the proto-stellar wind. We derive averaged Tkin and n(H2) values of about 300-500 K and 5 10^6 cm-3 respectively, while a water abundance with respect to H2 of the order of 0.5-1 10^{-6} along the outflow is estimated. The fairly constant conditions found all along the outflow implies that evolutionary effects on the timescales of outflow propagation do not play a major role in the H2O chemistry. The results of our analysis show that the bulk of the observed H2O lines comes from post-shocked regions where the gas, after being heated to high temperatures, has been already cooled down to a few hundred K. The relatively low derived abundances, however, call for some mechanism to diminish the H2O gas in the post-shock region. Among the possible scenarios, we favor H2O photodissociation, which requires the superposition of a low velocity non-dissociative shock with a fast dissociative shock able to produce a FUV field of sufficient strength.Comment: 16 pages, 13 figures, accepted for publication on Astronomy & Astrophysic

Hydrogen Fluoride in High-Mass Star-forming Regions

Hydrogen fluoride has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J=1-0 toward two high-mass star formation sites, NGC6334 I and AFGL 2591. In NGC6334 I the HF line is seen in absorption in foreground clouds and the source itself, while in AFGL 2591 HF is partially in emission. We find an HF abundance with respect to H2 of 1.5e-8 in the diffuse foreground clouds, whereas in the denser parts of NGC6334 I, we derive a lower limit on the HF abundance of 5e-10. Lower HF abundances in dense clouds are most likely caused by freeze out of HF molecules onto dust grains in high-density gas. In AFGL 2591, the view of the hot core is obstructed by absorption in the massive outflow, in which HF is also very abundant 3.6e-8) due to the desorption by sputtering. These observations provide further evidence that the chemistry of interstellar fluorine is controlled by freeze out onto gas grains.Comment: accepted in Ap

Herschel observations of extra-ordinary sources: Detection of Hydrogen Fluoride in absorption towards Orion~KL

We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules ("weeds"), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 x 10^13 cm^-2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H2 column density within the low-velocity molecular outflow, we obtain a lower limit of ~1.6 x 10^-10 for the HF abundance relative to hydrogen nuclei, corresponding to 0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J=2--1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 x 10^-9 derived by Neufeld et al. (2010) for cold, foreground clouds on the line of sight towards G10.6-0.4.Comment: 5 pages, 3 figures, paper to be published in the Herschel special issue of A&A letter

Shockingly low water abundances in Herschel / PACS observations of low-mass protostars in Perseus

Protostars interact with their surroundings through jets and winds impacting on the envelope and creating shocks, but the nature of these shocks is still poorly understood. Our aim is to survey far-infrared molecular line emission from a uniform and significant sample of deeply-embedded low-mass young stellar objects in order to characterize shocks and the possible role of ultraviolet radiation in the immediate protostellar environment. Herschel/PACS spectral maps of 22 objects in the Perseus molecular cloud were obtained as part of the `William Herschel Line Legacy' survey. Line emission from H$_\mathrm{2}$O, CO, and OH is tested against shock models from the literature. Observed line ratios are remarkably similar and do not show variations with source physical parameters. Observations show good agreement with the shock models when line ratios of the same species are compared. Ratios of various H$_\mathrm{2}$O lines provide a particularly good diagnostic of pre-shock gas densities, $n_\mathrm{H}\sim10^{5}$ cm$^{-3}$, in agreement with typical densities obtained from observations of the post-shock gas. The corresponding shock velocities, obtained from comparison with CO line ratios, are above 20 km\,s$^{-1}$. However, the observations consistently show one-to-two orders of magnitude lower H$_\mathrm{2}$O-to-CO and H$_\mathrm{2}$O-to-OH line ratios than predicted by the existing shock models. The overestimated model H$_\mathrm{2}$O fluxes are most likely caused by an overabundance of H$_\mathrm{2}$O in the models since the excitation is well-reproduced. Illumination of the shocked material by ultraviolet photons produced either in the star-disk system or, more locally, in the shock, would decrease the H$_\mathrm{2}$O abundances and reconcile the models with observations. Detections of hot H$_\mathrm{2}$O and strong OH lines support this scenario.Comment: 28 pages, 12 figures, accepted to Astronomy & Astrophysic

Spitzer's mid-infrared view on an outer Galaxy Infrared Dark Cloud candidate toward NGC 7538

Infrared Dark Clouds (IRDCs) represent the earliest observed stages of clustered star formation, characterized by large column densities of cold and dense molecular material observed in silhouette against a bright background of mid-IR emission. Up to now, IRDCs were predominantly known toward the inner Galaxy where background infrared emission levels are high. We present Spitzer observations with the Infrared Camera Array toward object G111.80+0.58 (G111) in the outer Galactic Plane, located at a distance of ~3 kpc from us and ~10 kpc from the Galactic center. Earlier results show that G111 is a massive, cold molecular clump very similar to IRDCs. The mid-IR Spitzer observations unambiguously detect object G111 in absorption. We have identified for the first time an IRDC in the outer Galaxy, which confirms the suggestion that cluster-forming clumps are present throughout the Galactic Plane. However, against a low mid-IR back ground such as the outer Galaxy it takes some effort to find them.Comment: Accepted for publication in ApJL -- 11 pages, 2 figures (1 colour