Capillary electrochromatography : fundamentals and applications

III+226hlm.;24c

Mercury in Active-Layer Tundra Soils of Alaska: Concentrations, Pools, Origins, and Spatial Distribution

Tundra soils serve as major sources of mercury (Hg) input to the Arctic Ocean via river runoff and coastal erosion; yet little information is available on tundra soil Hg concentrations, pool sizes, origins, and dynamics. We present a detailed investigation of Hg in the active layer (upper ~100 cm subject to seasonal thaw) of tundra soils across 11 sites in Alaska. Soil Hg concentrations in organic horizons (151±7 µg kg-1) were in the upper range of temperate soil organic horizons, and concentrations in mineral horizons (98±6 µg kg-1) were much higher than in temperate soils. Soil Hg concentrations declined from inland to coastal sites, in contrast to a hypothesized northward increase expected because of proximity to coastal atmospheric mercury depletion events (AMDEs). Principle component analyses and elemental ratios results show that exogenic sources dominated over geogenic sources-in A-horizons (66±4%), and mineral B-horizons (51±1%). 14C age-dating suggested recent origins of Hg in surface soils but showed that mineral soils (more than 7,300 years old) must have accumulated atmospheric inputs across millennia leading to high soil concentrations and pools. We estimated a total Northern Hemisphere (NH) active-layer tundra soil Hg pool of 184 Gg (range of 136 Gg to 274 Gg), suggesting a globally important Hg storage pool. Tundra soils are subject to seasonal thaw and freeze dynamics, thereby providing large inputs to rivers, lakes, and the Arctic Ocean. Understanding processes that mobilize Hg from tundra soils will be critical to understanding future Arctic wildlife and humans Hg exposures

Using nitrogen isotope fractionation to assess the oxidation of substituted anilines by manganese oxide

We explored the N isotope fractionation associated with the oxidation of substituted primary aromatic amines, which are often the position of initial attack in transformation processes of environmental contaminants. Apparent (15)N-kinetic isotope effects, AKIE(N), were determined for the oxidation of various substituted anilines in suspensions of manganese oxide (MnO(2)) and compared to reference experiments in homogeneous solutions and at electrode surfaces, as well as to density functional theory calculations of intrinsic KIE(N)for electron and hydrogen atom transfer reactions. Owing to the partial aromatic imine formation after one-electron oxidation and corresponding increase in C-N bond strength, AKIE(N)-values were inverse, substituent-dependent, and confined to the range between 0.992 and 0.999 in agreement with theory. However, AKIE(N)-values became normal once the fraction of cationic species prevailed owing to (15)N-equilibrium isotope effects, EIE(N), of 1.02 associated with N atom deprotonation. The observable AKIE(N)-values are substantially modulated by the acid/base pre-equilibria of the substituted anilines and isotope fractionation may even vanish under conditions where normal EIE(N) and inverse AKIE(N) cancel each other out. The pH-dependent trends of the AKIE(N)-values provide a new line of evidence for the identification of contaminant degradation processes via oxidation of primary aromatic amino groups

Photochemistry of oxidized Hg(I) and Hg(II) species suggests missing mercury oxidation in the troposphere

Mercury (Hg), a global contaminant, is emitted mainly in its elemental form Hg0 to the atmosphere where it is oxidized to reactive HgII compounds, which efficiently deposit to surface ecosystems. Therefore, the chemical cycling between the elemental and oxidized Hg forms in the atmosphere determines the scale and geographical pattern of global Hg deposition. Recent advances in the photochemistry of gas-phase oxidized HgI and HgII species postulate their photodissociation back to Hg0 as a crucial step in the atmospheric Hg redox cycle. However, the significance of these photodissociation mechanisms on atmospheric Hg chemistry, lifetime, and surface deposition remains uncertain. Here we implement a comprehensive and quantitative mechanism of the photochemical and thermal atmospheric reactions between Hg0, HgI, and HgII species in a global model and evaluate the results against atmospheric Hg observations. We find that the photochemistry of HgI and HgII leads to insufficient Hg oxidation globally. The combined efficient photoreduction of HgI and HgII to Hg0 competes with thermal oxidation of Hg0, resulting in a large model overestimation of 99% of measured Hg0 and underestimation of 51% of oxidized Hg and ∼66% of HgII wet deposition. This in turn leads to a significant increase in the calculated global atmospheric Hg lifetime of 20 mo, which is unrealistically longer than the 3–6-mo range based on observed atmospheric Hg variability. These results show that the HgI and HgII photoreduction processes largely offset the efficiency of bromine-initiated Hg0 oxidation and reveal missing Hg oxidation processes in the troposphere

The clinical implications of sunitinib-induced hypothyroidism: a prospective evaluation

Sunitinib is approved for the treatment of metastatic renal cell carcinoma (RCC) and imatinib-resistant or -intolerant gastrointestinal stromal tumours (GIST). Several studies have identified unexpected rates of thyroid dysfunction with sunitinib treatment. We performed a prospective observational study with the aim of more accurately defining the incidence and severity of hypothyroidism in RCC or GIST patients receiving sunitinib. Thyroid function was assessed at baseline and on days 1 and 28 of each treatment cycle. Thyroid antibodies were assessed at baseline and during follow-up if abnormal thyroid function tests were recorded. Sixteen patients (27%) developed sub- or clinical hypothyroidism and required hormone replacement and 20 patients (34%) showed at least one elevated thyroid-stimulating hormone not requiring therapeutic intervention. Twenty patients (34%) did not develop any biochemical thyroid abnormality. Thus, sunitinib can induce (sub-) clinical hypothyroidism, warranting close monitoring of thyroid function. We propose a new algorithm for managing this side effect in clinical practise

Characteristics of specialists treating hypothyroid patients: the “THESIS” collaborative

Copyright \ua9 2023 Žarković, Attanasio, Nagy, Negro, Papini, Perros, Cohen, Akarsu, Alevizaki, Ayvaz, Bednarczuk, Berta, Bodor, Borissova, Boyanov, Buffet, Burlacu, Ćirić, D\uedez, Dobnig, Fadeyev, Field, Fliers, Fr\uf8lich, F\ufchrer, Galofr\ue9, Hakala, Jiskra, Kopp, Krebs, Kršek, Kužma, Lantz, Laz\ufarov\ue1, Leenhardt, Luchytskiy, McGowan, Melo, Metso, Moran, Morgunova, Mykola, Beleslin, Niculescu, Perić, Planck, Poiana, Puga, Robenshtok, Rosselet, Ruchala, Riis, Shepelkevich, Unuane, Vardarli, Visser, Vrionidou, Younes, Yurenya and Heged\ufcs.Introduction: Thyroid specialists influence how hypothyroid patients are treated, including patients managed in primary care. Given that physician characteristics influence patient care, this study aimed to explore thyroid specialist profiles and associations with geo-economic factors. Methods: Thyroid specialists from 28 countries were invited to respond to a questionnaire, Treatment of Hypothyroidism in Europe by Specialists: an International Survey (THESIS). Geographic regions were defined according to the United Nations Statistics Division. The national economic status was estimated using World Bank data on the gross national income per capita (GNI per capita). Results: 5,695 valid responses were received (response rate 33\ub70%). The mean age was 49 years, and 65\ub70% were female. The proportion of female respondents was lowest in Northern (45\ub76%) and highest in Eastern Europe (77\ub72%) (p <0\ub7001). Respondent work volume, university affiliation and private practice differed significantly between countries (p<0\ub7001). Age and GNI per capita were correlated inversely with the proportion of female respondents (p<0\ub701). GNI per capita was inversely related to the proportion of respondents working exclusively in private practice (p<0\ub7011) and the proportion of respondents who treated >100 patients annually (p<0\ub701). Discussion: THESIS has demonstrated differences in characteristics of thyroid specialists at national and regional levels, strongly associated with GNI per capita. Hypothyroid patients in middle-income countries are more likely to encounter female thyroid specialists working in private practice, with a high workload, compared to high-income countries. Whether these differences influence the quality of care and patient satisfaction is unknown, but merits further study

Characteristics of specialists treating hypothyroid patients:the “THESIS” collaborative

Introduction: Thyroid specialists influence how hypothyroid patients are treated, including patients managed in primary care. Given that physician characteristics influence patient care, this study aimed to explore thyroid specialist profiles and associations with geo-economic factors. Methods: Thyroid specialists from 28 countries were invited to respond to a questionnaire, Treatment of Hypothyroidism in Europe by Specialists: an International Survey (THESIS). Geographic regions were defined according to the United Nations Statistics Division. The national economic status was estimated using World Bank data on the gross national income per capita (GNI per capita). Results: 5,695 valid responses were received (response rate 33·0%). The mean age was 49 years, and 65·0% were female. The proportion of female respondents was lowest in Northern (45·6%) and highest in Eastern Europe (77·2%) (p &lt;0·001). Respondent work volume, university affiliation and private practice differed significantly between countries (p&lt;0·001). Age and GNI per capita were correlated inversely with the proportion of female respondents (p&lt;0·01). GNI per capita was inversely related to the proportion of respondents working exclusively in private practice (p&lt;0·011) and the proportion of respondents who treated &gt;100 patients annually (p&lt;0·01). Discussion: THESIS has demonstrated differences in characteristics of thyroid specialists at national and regional levels, strongly associated with GNI per capita. Hypothyroid patients in middle-income countries are more likely to encounter female thyroid specialists working in private practice, with a high workload, compared to high-income countries. Whether these differences influence the quality of care and patient satisfaction is unknown, but merits further study.</p

Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution

Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean