Benthic pH gradients across a range of shelf sea sediment types linked to sediment characteristics and seasonal variability

This study used microelectrodes to record pH profiles in fresh shelf sea sediment cores collected across a range of different sediment types within the Celtic Sea. Spatial and temporal variability was captured during repeated measurements in 2014 and 2015. Concurrently recorded oxygen microelectrode profiles and other sedimentary parameters provide a detailed context for interpretation of the pH data. Clear differences in profiles were observed between sediment type, location and season. Notably, very steep pH gradients exist within the surface sediments (10–20 mm), where decreases greater than 0.5 pH units were observed. Steep gradients were particularly apparent in fine cohesive sediments, less so in permeable sandier matrices. We hypothesise that the gradients are likely caused by aerobic organic matter respiration close to the sediment–water interface or oxidation of reduced species at the base of the oxic zone (NH4+, Mn2+, Fe2+, S−). Statistical analysis suggests the variability in the depth of the pH minima is controlled spatially by the oxygen penetration depth, and seasonally by the input and remineralisation of deposited organic phytodetritus. Below the pH minima the observed pH remained consistently low to maximum electrode penetration (ca. 60 mm), indicating an absence of sub-oxic processes generating H+ or balanced removal processes within this layer. Thus, a climatology of sediment surface porewater pH is provided against which to examine biogeochemical processes. This enhances our understanding of benthic pH processes, particularly in the context of human impacts, seabed integrity, and future climate changes, providing vital information for modelling benthic response under future climate scenarios

On trace metal geochemistry in the Danube River and western Black Sea

Trace metal concentrations were measured in the Danube River estuary and in the shelf area of the north-western Black Sea. Total dissolved concentrations (<0.45 mu M) of the freshwater in the river end-member were found to be: Cd = 117 pM, Pb=81 pM, Co = 266 pM, Zn = 6 nM, Mn = 19 nM, Ni = 15 nM, Cu = 36 nM, Al = 384 nM and Fe = 20 nM. These concentrations are surprisingly low for an area where serious contamination has been suspected. This is particularly true of Cd, Pb and Zn, which are generally anthropogenic in polluted regions. The observed low concentrations, in particular for Fe, Mn, Co and Al can be attributable to the precipitation of hydrated oxides as a consequence of high pH of the Danube River. Concentrations of metals in the particulate fraction are similar to those in other major rivers of the world. The evolution of the total dissolved trace metal concentrations in the surface waters within the salinity gradient suggests: (1) no noticeable exchange between the particulate and the dissolved fraction for Cu, Ni and Zn; and (2) evidence for a low solid to liquid exchange for the other metals (Cd, Fe, Mn, Co and Pb) which brings about a two-fold increase in their concentrations from lower to higher salinity. Another source of dissolved material is suspected at around salinity 15. This source may be from localized-patches in the sediment where specific redox conditions may induce a vertical flux of dissolved metals: the bottom waters above these patches are characterized by a diminution of the dissolved O-2 and high concentrations of metals. The colloidal fraction (between 10 kD and 0.45 mu m) was established on a limited number of samples for Cd, Cu, Mn and Fe and was found to be significant: 40% of Cu, 40% of Cd, similar to 50% of Mn and 60% of Fe of the so-called dissolved phase are actually associated with colloidal material. It represents at least 40% of the total dissolved concentration in the fresh water and in the mixing zone. This proportion decreases linearly with salinity for Cd and Cu. Fe is mostly in colloidal form with a maximum (similar to 80%) between salinity 5 and 10. The surface distribution of the total dissolved metals throughout the study area show a limited influence of the Danube on the concentrations observed for the 'open sea' (salinity = 18). Most of the riverine flux seems to follow the general circulation to the south-west area. These 'open Black Sea' concentrations are the same order of magnitude as average surface concentrations in the Mediterranean Sea. (C) 1998 Academic Press

Impact of the first month of Covid-19 lockdown on oncologic surgical activity in the Ile de France region university hospital otorhinolaryngology departments

International audienceObjective: To evaluate the impact of the first month of lockdown related to the Covid-19 epidemic on the oncologic surgical activity in the Ile de France region university hospital otorhinolaryngology departments.Material and methods: A multicenter prospective observational assessment was conducted in 6 university hospital otorhinolaryngology departments (Paris Centre, Nord, Est and Sorbonne) during the 1-month periods before (Month A) and after (Month B) lockdown on March 17, 2020. The main goal was to evaluate lockdown impact on oncologic surgical activity in the departments. Secondary goals were to report population characteristics, surgery conditions, postoperative course, progression of Covid status in patients and surgeons, and adverse events.Results: 224 procedures were performed. There was 10.9% reduction in overall activity, without significant difference between departments. Squamous cell carcinoma and larynx, hypopharynx, oropharynx, oral cavity and nasal cavity and sinus locations were predominant, at 79% and 75.8% of cases respectively, with no significant differences between months. T3/4 and N2/3 tumors were more frequent in Month B (P=.002 and .0004). There was no significant difference between months regarding surgical approach, type of reconstruction, postoperative course, tracheotomy and nasogastric feeding-tube time, intensive care stay or hospital stay. None of the Month A patients were Covid-19-positive, versus 3 in Month B, without adverse events. None of the otorhinolaryngologists involved in the procedures developed symptoms suggesting Covid-19 infestation.Conclusion: The present study underscored the limited impact of the Covid-19 epidemic and lockdown on surgical diagnosis and cancer surgery in the Ile de France university otorhinolaryngology departments, maintaining chances for optimal survival without spreading the virus

Significance of tumour volume measurements in tongue cancer: A novel role in staging

10.1111/j.1445-2197.2007.04176.xANZ Journal of Surgery778632-637AJSN