Phytoplankton responses to dust addition in the Fe-Mn co-limited eastern Pacific sub-Antarctic differ by source region.

The seasonal availability of light and micronutrients strongly regulates productivity in the Southern Ocean, restricting biological utilization of macronutrients and CO2 drawdown. Mineral dust flux is a key conduit for micronutrients to the Southern Ocean and a critical mediator of multimillennial-scale atmospheric CO2 oscillations. While the role of dust-borne iron (Fe) in Southern Ocean biogeochemistry has been examined in detail, manganese (Mn) availability is also emerging as a potential driver of past, present, and future Southern Ocean biogeochemistry. Here, we present results from fifteen bioassay experiments along a north-south transect in the undersampled eastern Pacific sub-Antarctic zone. In addition to widespread Fe limitation of phytoplankton photochemical efficiency, we found further responses following the addition of Mn at our southerly stations, supporting the importance of Fe-Mn co-limitation in the Southern Ocean. Moreover, addition of different Patagonian dusts resulted in enhanced photochemical efficiency with differential responses linked to source region dust characteristics in terms of relative Fe/Mn solubility. Changes in the relative magnitude of dust deposition, combined with source region mineralogy, could hence determine whether Fe or Mn limitation control Southern Ocean productivity under future as well as past climate states.

The characteristics of atmospheric particles and metal elements during winter in Beijing: Size distribution, source analysis, and environmental risk assessment.

In order to investigate the pollution characteristics of size-segregated particles and metal elements (MEs) after the Chinese Air Pollution Prevention Action Plan was released in 2013, an intensive field campaign was conducted in the suburban area of Chaoyang District, Beijing in winter 2016. The size distributions of particle mass concentrations were bimodal, with the first peak in the fine fraction (0.4-2.1 µm) and the second peak in the coarse fraction (3.3-5.8 µm). Moreover, the proportion of fine particles increased and the proportion of coarse particles decreased as the pollution level was more elevated. It was found that the composition of coarse particles is as important as that of fine particles when pollution of aerosol metals in the atmosphere in 2016 were compared to 2013. In addition, according to the size distribution characteristics, 23 MEs were divided into three groups: (a) Fe, Co, Sr, Al, Ti, Ba, and U, which concentrated in coarse mode; (b) Zn, As, Cd, Tl, and Pb, which concentrated in fine mode; and (c) Na, K, Be, V, Cr, Mn, Ni, Cu, Mo, Ag, and Sn, showing bimodal distribution. Under clean air, slight pollution and moderate pollution conditions, most elements maintained their original size distributions, while under severe pollution, the unimodal distributions of most MEs became bimodal distributions. The factors analysis combined with size distributions indicated that Na, Zn, Mo, Ag, Cd, and Tl, showing the moderate to severe contamination on environment, were significantly influenced by diffuse regional emissions or anthropogenic source emissions (vehicle exhaust emissions and combustion process). The environmental risk assessment revealed that the heavy metal loading in the atmospheric particles collected had a high potential for ecological risk to the environment during sampling period because of the high contribution of Cd, Tl, Zn and Pb.

Increasing picocyanobacteria success in shelf waters contributes to long-term food web degradation.

Continental margins are disproportionally important for global primary production, fisheries and CO2 uptake. However, across the Northeast Atlantic shelves, there has been an ongoing summertime decline of key biota-large diatoms, dinoflagellates and copepods-that traditionally fuel higher tropic levels such as fish, sea birds and marine mammals. Here, we combine multiple time series with in situ process studies to link these declines to summer nutrient stress and increasing proportions of picophytoplankton that can comprise up to 90% of the combined pico- and nanophytoplankton biomass in coastal areas. Among the pico-fraction, it is the cyanobacterium Synechococcus that flourishes when iron and nitrogen resupply to surface waters are diminished. Our field data show how traits beyond small size give Synechococcus a competitive edge over pico- and nanoeukaryotes. Key is their ability to grow at low irradiances near the nutricline, which is aided by their superior light-harvesting system and high affinity to iron. However, minute size and lack of essential biomolecules (e.g. omega-3 polyunsaturated fatty acids and sterols) render Synechococcus poor primary producers to sustain shelf sea food webs efficiently. The combination of earlier spring blooms and lower summer food quantity and quality creates an increasing period of suboptimal feeding conditions for zooplankton at a time of year when their metabolic demand is highest. We suggest that this nutrition-related mismatch has contributed to the widespread, ~50% decline in summer copepod abundance we observe over the last 60 years. With Synechococcus clades being prominent from the tropics to the Arctic and their abundances increasing worldwide, our study informs projections of future food web dynamics in coastal and shelf areas where droughts and stratification lead to increasing nutrient starvation of surface waters.

Combined uncertainty estimation for the determination of the dissolved iron amount content in seawater using flow injection with chemiluminescence detection.

This work assesses the components contributing to the combined uncertainty budget associated with the measurement of the Fe amount content by flow injection chemiluminescence (FI-CL) in <0.2 µm filtered and acidified seawater samples. Amounts of loaded standard solutions and samples were determined gravimetrically by differential weighing. Up to 5% variations in the loaded masses were observed during measurements, in contradiction to the usual assumptions made when operating under constant loading time conditions. Hence signal intensities (V) were normalised to the loaded mass and plots of average normalised intensities (in V kg-1) vs. values of the Fe amount content (in nmol kg-1) added to a "low level" iron seawater matrix were used to produce the calibration graphs. The measurement procedure implemented and the uncertainty estimation process developed were validated from the agreement obtained with consensus values for three SAFe and GEOTRACES reference materials (D2, GS, and GD). Relative expanded uncertainties for peak height and peak area based results were estimated to be around 12% and 10% (coverage factor k = 2), respectively. The most important contributory factors were the uncertainty on the sensitivity coefficient (i.e., calibration slope) and the within-sequence-stability (i.e., the signal stability over several hours of operation; here 32 h). For GD, using peak height measurements, these factors contributed respectively 69.7% and 21.6% while the short-term repeatability accounted for only 7.9%. Therefore, an uncertainty estimation based on the intensity repeatability alone, as is often done in FI-CL studies, is not a realistic estimation of the overall uncertainty of the procedure.

Resolution of renal failure 1 month after onset through angioplasty of renal artery stenosis.

The stent placement in patients with atherosclerotic renal artery stenosis and impaired renal function (STAR) and revascularization versus medical therapy for renal-artery stenosis (ASTRAL) trials concluded that renal artery angioplasty was not superior to medical management in delaying progression to renal failure or controlling blood pressure in a selected population. (1,2) There were several criticisms of the STAR trial's methodology, and an important criticism of ASTRAL was that the patient was excluded if their clinician was uncertain of the value in correcting the stenosis. Anuric renal failure by renal artery stenosis is a rare occurrence and falls outside this criteria.

Development of a risk prediction model of pneumothorax in percutaneous computed tomography guided transthoracic needle lung biopsy.

INTRODUCTION: To retrospectively evaluate the incidence of and the risk factors for pneumothorax and intercostal catheter insertion (ICC) after CT-guided lung biopsy and to generate a risk prediction model for developing a pneumothorax and requiring an ICC. METHODS: 255 CT-guided lung biopsies performed for 249 lesions in 249 patients from August 2014 to August 2019 were retrospectively analysed using multivariate logistic regression analysis. Risk prediction models were established using backward stepwise variable selection and likelihood ratio tests and were internally validated using split-sample methods. RESULTS: The overall incidence of pneumothorax was 30.2% (77/255). ICC insertion was required for 8.32% (21/255) of all procedures. The significant independent risk factors for pneumothorax were lesions not in contact with pleura (P < 0.001), a shorter skin-to-pleura distance (P = 0.01), the needle crossing a fissure (P = 0.004) and emphysema (P = 0.01); those for ICC insertion for pneumothorax were a needle through emphysema (P < 0.001) and lesions in the upper lobe (P = 0.017). AUC of the predictive models for pneumothorax and ICC insertion were 0.800 (95% CI: 0.745-0.856) and 0.859 (95% CI: 0.779-0.939) respectively. Upon internal validation, AUC of the testing sets of pneumothorax and ICC insertion were 0.769 and 0.822 on average respectively. CONCLUSION: The complication rates of pneumothorax and ICC insertion after CT-guided lung biopsy at our institution are comparable to results from previously reported studies. This study provides highly accurate risk prediction models of pneumothorax and ICC insertion for patients undergoing CT-guided lung biopsies.

Automated, high frequency, on-line dimethyl sulfide measurements in natural waters using a novel "microslug" gas-liquid segmented flow method with chemiluminescence detection.

Dimethyl sulfide (DMS) is the major biogenic volatile sulfur compound in surface seawater. Good quality DMS data with high temporal and spatial resolution are desirable for understanding reduced sulfur biogeochemistry. Here we present a fully automated and novel "microslug" gas-liquid segmented flow-chemiluminescence (MSSF-CL) based method for the continuous in-situ measurement of DMS in natural waters. Samples were collected into a flow tank and DMS transferred from the aqueous phase to the gas phase using a vario-directional coiled flow, in which microvolume liquid and gas slugs were interspersed. The separated DMS was reacted with ozone in a reaction cell for CL detection. The analytical process was automated, with a sample throughput of 6.6 h-1. Using MSSF for DMS separation was more effective and easily integrated with CL detection compared with the commonly used bubbling approach. Key parameters of the proposed method were investigated. The linear range for the method was 0.05-500 nM (R2 = 0.9984) and the limit of detection (3 x S/N) was 0.015 nM, which is comparable to the commonly used gas chromatography (GC) method and sensitive enough for direct DMS measurement in typical aquatic environments. Reproducibility and recovery were assessed by spiking natural water samples (river, lake, reservoir and pond) with different concentrations of DMS (10, 20 and 50 nM), giving relative standard deviations (RSDs) ≤1.75% (n = 5) and recoveries of 94.4-107.8%. This fully automated system is reagent free, easy to assemble, simple to use, portable (weight ~5.1 kg) and can be left in the field for several hours of unattended operation. The instrumentation can provide high quality DMS data for natural waters with an environmentally relevant temporal resolution of ~9 min.

Uncertainty associated with the leaching of aerosol filters for the determination of metals in aerosol particulate matter using collision/reaction cell ICP-MS detection.

High quality observational data with a firm uncertainty assessment are essential for the proper validation of biogeochemical models for trace metals such as iron. Typically, concentrations of these metals are very low in oceanic waters (nM and sub nM) and ICP-MS is therefore a favoured technique for quantitative analysis. Uncertainties in the measurement step are generally well constrained, even at sub-nM concentrations. However, the measurement step is only part of the overall procedure. For the determination of trace metal solubilities from aerosols in the surface ocean, aerosol collection on a filter paper followed by a leaching procedure is likely to make a significant contribution to the overall uncertainty. This paper quantifies the uncertainties for key trace metals (cobalt, iron, lead and vanadium), together with aluminium as a reference element, for a controlled, flow through laboratory leaching procedure using filters collected from three different sampling sites (Tudor Hill (Bermuda), Heraklion (Crete) and Tel-Shikmona (Israel)) and water, glucuronic acid and desferrioxamine B as leachants. Relative expanded uncertainties were in the range of 12-29% for cobalt, 12-62% for iron, 13-45% for lead and 5-11% for vanadium. Fractional solubilities for iron ranged from 0.2 ±â€¯0.1% to 16.9 ±â€¯3.5%.

Examining the sensitivity of ultrasound-guided large core biopsy for invasive breast carcinoma in a population screening programme.

INTRODUCTION: To evaluate the sensitivity of ultrasound-guided core-needle biopsy (UCB) in invasive breast carcinoma and to establish causes of false-negative biopsy in a population screening programme. METHOD: We identified 571 consecutive women diagnosed with surgically proven invasive breast cancer. Histology from 14-gauge UCB was compared with surgical histology to identify true-positive and false-negative ultrasound core biopsies. True-positive and false-negative groups were compared for tumour size and histology. On blinded review of UCB images and pathology reports from false negative (n = 20) and a random sample of true-positive cases (n = 80), we compared core sample number and needle visualisation in the lesion. RESULTS: Of 571 carcinomas sampled with UCB, 551 (96.5%) were true positive and 20 (3.5%) were false negative. The mean core number was 2.0 (range 1-3) for false negatives and 2.25 (range 1-4) for true positives (P = 0.27). Mean tumour sizes were 13.3 and 16.2 mm for the false-negative and true-positive groups, respectively (P = 0.25). Tubular carcinomas represented 30% (6/20) of false-negative cases compared with 5.1% (28/551) of the true-positive cases (P < 0.001). On blinded review, needle visualisation within the lesion was demonstrated in 47.4% (9/19) of false-negative cases and 76.3% (61/80) of true-positive cases (P = 0.02). CONCLUSION: We demonstrated a sensitivity of 96.5% with a mean of 2.21 cores. False-negative results were more likely in the absence of post-fire needle position verification and with tubular carcinomas. Neither tumour size nor core number predicted diagnostic accuracy.

Distribution of size fractionated dissolved iron in the Canary Basin.

The distribution of size fractionated dissolved iron (DFe, <0.2 mum) species was determined in the upper water column (0-150 m) of the Canary Basin (25-32 degrees N and 18-24 degrees W) on a research cruise in October 2002. A DFe concentration gradient resulting from a decrease in both soluble iron (SFe, <0.02 microm) and colloidal iron (CFe, 0.02-0.2 microm) was shown to extend from the coast of North West Africa into the oligotrophic gyre (varying from approximately 1 nM in the shelf region to 0.15 nM in the most off shore waters). At the time of this study, the dominant dissolved Fe input to the region was deduced to be the advection of shelf and upwelled waters rather than Saharan dust deposition. SFe and CFe fractions had mean concentrations (+/- one standard deviation) of 0.25 +/- 0.11 and 0.21 +/- 0.16 nM, respectively (n = 58). Colloidal iron formed a highly variable fraction of DFe (ca. 0-80%, mean of 42%) in the region but was less variable in the low iron, oligotrophic intermediate waters (0.18 +/- 0.06 nM, 31.7 degrees N, 22.0 degrees W, 0-1300 m depth). The high variability found at the most productive near-shelf stations was driven by biological processing and mixing of different water masses. In contrast, less variability between SFe and CFe at the remote off shore stations suggested that vertical variations in the water column were controlled more by chemical partitioning and vertical particle fluxes with evidence of preferential biological uptake and/or removal of SFe in the most remote surface waters.

Investigation of iron(III) reduction and trace metal interferences in the determination of dissolved iron in seawater using flow injection with luminol chemiluminescence detection.

A detailed investigation into the performance of two flow injection-chemiluminescence (FI-CL) manifolds (with and without a preconcentration column) for the determination of sub-nanomolar dissolved iron (Fe(II)+Fe(III)), following the reduction of Fe(III) by sulphite, in seawater is described. Kinetic experiments were conducted to examine the efficiency of reduction of inorganic Fe(III) with sulphite under different conditions and a rigorous study of the potential interference caused by other transition metals present in seawater was conducted. Using 100microM concentrations of sulphite a reduction time of 4h was sufficient to quantitatively reduce Fe(III) in seawater. Under optimal conditions, cobalt(II) and vanadium(IV)/(III) were the major positive interferences and strategies for their removal are reported. Specifically, cobalt(II) was masked by the addition of dimethylglyoxime to the luminol solution and vanadium(IV) was removed by passing the sample through an 8-hydroxyquinoline column in a low pH carrier stream. Manganese(II) also interfered by suppression of the CL response but this was not significant at typical open ocean concentrations.

Hydroxamate siderophores: occurrence and importance in the Atlantic Ocean.

Siderophores are chelates produced by bacteria as part of a highly specific iron uptake mechanism. They are thought to be important in the bacterial acquisition of iron in seawater and to influence iron biogeochemistry in the ocean. We have identified and quantified two types of siderophores in seawater samples collected from the Atlantic Ocean. These siderophores were identified as hydroxamate siderophores, both ferrioxamine species representative of the more soluble marine siderophores characterized to date. Ferrioxamine G was widely distributed in surface waters throughout the Atlantic Ocean, while ferrioxamine E had a more varied distribution. Total concentrations of the two siderophores were between 3 and 20 pM in the euphotic zone. If these compounds are fully complexed in seawater, they represent approximately 0.2-4.6% of the <0.2 microm iron pool. Our data confirm that siderophore-mediated iron acquisition is important for marine heterotrophic bacteria and indicate that siderophores play an important role in the oceanic biogeochemical cycling of iron.

Design of an automated flow injection-chemiluminescence instrument incorporating a miniature photomultiplier tube for monitoring picomolar concentrations of iron in seawater.

A flow-injection (FI)-based instrument under LabVIEW control for monitoring iron in marine waters is described. The instrument incorporates a miniature, low-power photomultiplier tube (PMT), and a number of microelectric and solenoid actuated valves and peristaltic pumps. The software allows full control of all flow injection components and processing of the data from the PMT. The optimised system is capable of 20 injections per hour, including preconcentration and wash steps. The detection limit (3 sd of the blank) is 21 pM at sea and the linear range is 21-2000 pM with a 60-second sample load time. Typical precision between replicate FI peaks is 5.9 +/- 3.2 % (n =4) over the linear range.

Real-time monitoring of picomolar concentrations of iron(II) in marine waters using automated flow injection-chemiluminescence instrumentation.

A shipboard-deployable, flow-injection (FI) based instrument for monitoring iron(II) in surface marine waters is described. It incorporates a miniature, low-power photon-counting head for measuring the light emitted from the iron(II)-catalyzed chemiluminescence (CL) luminol reaction. System control, signal acquisition, and data processing are performed in a graphical programming environment. The limit of detection for iron(II) is in the range 8-12 pmol L(-1) (based on 3 s of the blank), and the precision over the range 8-1000 pmol L(-1) varies between 0.9 and 7.6% (n = 4). Results from a day-night deployment during a north-to-south transect of the Atlantic Ocean and a daytime transect in the Sub-Antarctic Front are presented together with ancillary temperature, salinity, and irradiance data. The generic nature of the components used to assemble the instrument make the technology readily transferable to other laboratories and the modular construction makes it easy to adapt the system for use with other CL chemistries.