Cl Flux Research Articles

Chemical and Physical Denudation Rates in the Poços de Caldas Alkaline Massif, Minas Gerais State, Brazil

Chemical and physical denudation rates have been assessed in areas with different lithologies. Surprisingly, there are no studies that attempt to document these rates in the Poços de Caldas Alkaline Massif (PC), the largest alkaline magmatism in South America and an important Al supergene deposit in Brazil. Therefore, the chemical and physical denudation rates were assessed and explained in the PC. Surface water and rainwater samples were collected at the Amoras Stream basin, covering one complete hydrological cycle (2016). All samples were analyzed for dissolved cations, silica, anions, total dissolved solids (TDS), and total suspended solids (TSS). The results reflected the seasonal variation on discharge, water temperature, and electrical conductivity in the Amoras Stream, with most of the cations, anions, silica TDS, and TSS being carried in the wet season. Partial hydrolysis and silicate incongruent dissolution are the main water/rock interactions in the PC, with an atmospheric/soil CO2 consumption rate of 1.6 × 105 mol/km2/a. The annual fluxes of Cl−, PO43−, NO3−, and Al3+ were significantly influenced from rainwater. Chemical and physical weathering rates were 4 ± 0.8 and 3.0 ± 0.6 m/Ma in the PC, respectively, indicating that under the current climatic condition, the weathering profile is in dynamic equilibrium.

First measurements of chlorine 36 (36Cl) wet deposition fluxes in the vicinity of Orano La Hague nuclear reprocessing plant in France

Chlorine 36 (36Cl) is a radionuclide of natural and anthropogenic origin, mainly used as a tracer in geochemical studies. Owing to analytical constraints and its low environmental levels, knowledge of 36Cl behavior in the environment is still very limited. In this study, we use environmental measurements to report for the first time the wet deposition fluxes of 36Cl downwind an anthropogenic source, the Orano nuclear reprocessing plant, which chronically emits 36Cl into the environment. Measurements of 36Cl in rainwater samples at our study site were 1–2 orders of magnitude above the environmental background. The isotope ratios 36Cl/Cl of the samples and the 36Cl content in the rainwater averaged 2.3x10−12 at at−1 and 1.7x108 at l−1 respectively. A decrease in these levels was observed 20 km away from the study site, outside the plant's gas plume, indicating that the marking of 36Cl on the study site is related to the plant discharges. Over the sampling period, wet deposition fluxes at the study site averaged 3.4x103 at m−2s−1, with significant values measured when precipitations scavenge the plant's gas plume down onto our study site. Analysis of these fluxes also revealed the presence of a significant rainout phenomenon in the study area. These results provide new data on the wet deposition flux of 36Cl and will thus enable better assessment of impact studies in a context of decommissioning or accidents involving nuclear power plants.

Chloride hydrogeochemistry of the finger lakes in Central and Western New York, USA

Road deicing salts have impacted the hydrogeochemistry of lakes throughout the snow-belt region of the globe. This paper advances our understanding of the historical change in salt concentrations in, and sources to, the Finger Lakes of western and central New York state, and compares the results to other lakes across the globe. Surface water samples from Honeoye, Canandaigua, Keuka, Seneca, Cayuga, Owasco, Skaneateles and Otisco lakes were analyzed for chloride (Cl) concentrations, and augmented with published and unpublished decade, and for the first time, century-scale Cl data for these lakes and Hemlock Lake. A mass-balance model estimated the Cl flux required to match the measured Cl concentrations in each lake. Cl concentration and flux trends defined two groups of lakes. Group 1: A mid-1900′s peak in Cl concentrations was detected in Seneca and Cayuga lakes, that resulted from a short but significant spike of Cl, most likely from salt mine wastes during pre-Environmental Protection Agency times. Group 2: Hemlock, Honeoye, Canandaigua, Keuka, Owasco, Skaneateles and Otisco lakes, revealed smaller yet increasing concentrations and fluxes over time that were interpreted to reflect increasing use of road deicing salts in their watersheds and supported by correlations to their state and federal road lengths, percentage of impervious surfaces, water residence times in each watershed and the production of road salt in the US, but not to their trophic status, nor their percentage of agricultural land. Estimated Cl inputs from municipal wastewater treatment facilities, individual septic systems and the atmosphere (precipitation) were also insignificant in the Finger Lakes region. These results help clarify the processes responsible for increasing Chloride concentrations in lakes globally.

Deep magma degassing and volatile fluxes through volcanic hydrothermal systems: Insights from the Askja and Kverkfjöll volcanoes, Iceland

Mantle volatiles are transported to Earth's crust and surface by basaltic volcanism. During subaerial eruptions, vast amounts of carbon, sulfur and halogens can be released to the atmosphere during a short time-interval, with impacts ranging in scale from the local environment to the global climate. By contrast, passive volatile release at the surface originating from magmatic intrusions is characterized by much lower flux, yet may outsize eruptive volatile quantities over long timescales. Volcanic hydrothermal systems (VHSs) act as conduits for such volatile release from degassing intrusions and can be used to gauge the contribution of intrusive magmatism to global volatile cycles. Here, we present new compositional and isotopic (δD and δ18O-H2O, 3He/4He, δ13C-CO2, Δ33S-δ34S-H2S and SO4) data for thermal waters and fumarole gases from the Askja and Kverkfjöll volcanoes in central Iceland. We use the data together with magma degassing modelling and mass balance calculations to constrain the sources of volatiles in VHSs and to assess the role of intrusive magmatism to the volcanic volatile emission budgets in Iceland.The CO2/ΣS (10−30), 3He/4He (8.3–10.5 RA; 3He/4He relative to air), δ13C-CO2 (−4.1 to −0.2 ‰) and Δ33S-δ34S-H2S (−0.031 to 0.003 ‰ and −1.5 to +3.6‰) values in high-gas flux fumaroles (CO2 > 10 mmol/mol) are consistent with an intrusive magmatic origin for CO2 and S at Askja and Kverkfjöll. We demonstrate that deep (0.5–5 kbar, equivalent to ∼2–18 km crustal depth) decompression degassing of basaltic intrusions in Iceland results in CO2 and S fluxes of 330–5060 and 6–210 kt/yr, respectively, which is sufficient to account for the estimated CO2 flux of Icelandic VHSs (3365–6730 kt/yr), but not the VHS S flux (220–440 kt/yr). Secondary, crystallization-driven degassing from maturing intrusions and leaching of crustal rocks are suggested as additional sources of S. Only a minor proportion of the mantle flux of Cl is channeled via VHSs whereas the H2O flux remains poorly constrained, because magmatic signals in Icelandic VHSs are masked by a dominant shallow groundwater component of meteoric water origin. These results suggest that the bulk of the mantle CO2 and S flux to the atmosphere in Iceland is supplied by intrusive, not eruptive magmatism, and is largely vented via hydrothermal fields.

H2S-mediated balance regulation of stomatal and non-stomatal factors responding to drought stress in Chinese cabbage.

Increased evidence has shown that hydrogen sulfide (H2S), a novel gasotransmitter, could enhance drought resistance in plants by inducing stomatal closure, with concurrent enhancement of photosynthetic efficiency, but little is known about the mechanism behind this contradictory phenomenon. This study examined the regulating mechanism of H2S in response to drought stress from stomatal and non-stomatal factors in Chinese cabbage. The results showed that exogenous H2S could increase the accumulation of photosynthetic pigments and alleviate the damage caused by drought stress. It also regulated the expression in transcriptional level and the activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (BrRuBisCO) under drought stress. The large subunit of BrRuBisCO was found to be modified by S-sulfhydration, which might be the reason for its increased enzyme activity. The fluxes of Cl-, K+, and H+ in the guard cells were detected by non-invasive micro-test techniques while under drought stress. The results indicated that H2S signaling induced a transmembrane Cl- and H+ efflux and inhibited K+ influx, and the Cl- channel was the main responders for H2S-regulated stomatal movement. In conclusion, H2S signal not only activated the ion channel proteins located in the guard cell membrane to induce stomatal closure, but also regulated the transcriptional expression and the activity of RuBisCO, a non-stomatal factor to enhance the photosynthetic efficiency of leaves. There is therefore a beneficial balance between the regulation of H2S signaling on stomatal factors and non-stomatal factors due to drought stress, which needs to be better understood to apply it practically to increase crop yields.

Halogen (F, Cl, Br, and I) concentrations of the upper continental crust through time as recorded in ancient glacial diamictite composites

The continental crust is an important reservoir for incompatible elements, including the halogen elements (F, Cl, Br, and I), but their concentrations remain poorly known, thus hindering better understanding of the role of the crust in Earth’s halogen cycle. We present halogen data (F, Cl, Br, and I) for twenty-four well-characterized glacial diamictite composites that derive from the upper continental crust (UCC) and were deposited during discrete glacial events at ∼2.9 Ga, ∼2.4–2.2 Ga, 0.75–0.58 Ga, and ∼0.30 Ga. A good correlation between Cl and the highly soluble Na (R2 = 0.70), together with low and scattered Cl concentrations in the diamictites (2–279 ppm), indicates significant Cl loss during chemical weathering of the continents. The other halogens (F, Br, and I), however, are not strongly affected by chemical weathering as revealed by their correlations with less soluble elements like K, P, Nd, and Lu, which may be due to their retention in secondary minerals and/or organic matter. Increasing concentrations of F in the composites through time may reflect the evolving composition of the UCC. Using the median values of the Neoproterozoic and Paleozoic diamictite composites, halogen concentrations of the present-day weathered UCC are estimated to be: 575 ± 87 ppm F, 29 ± 20 ppm Cl, 0.65 ± 0.14 ppm Br, and 0.05 ± 0.01 ppm I (errors quoted at the median absolute deviation). Linear correlations between halogens and other elements provide estimates for minimum halogen concentrations of the present-day crystalline UCC: 394 ± 67 ppm F, 83 ± 24 ppm Cl, 0.41 ± 0.04 ppm Br, and 0.03 ± 0.01 ppm I (with 2σ uncertainties). These estimates are all lower than normalized concentrations of elements of similar incompatibility during igneous differentiation, which may reflect loss of halogens via magmatic degassing/exsolution and/or chemical weathering during the formation of the continental crust. The distinct behavior of Cl compared to Br and I during continental weathering leads to a wide range of Br/Cl (2–265 * 10−3) and I/Cl (122–197,952 * 10−6) ratios, and Br/I ratios that are distinctly higher than those of pelagic sediments and marine pore fluids. Similar halogen signals have been reported from the lithospheric mantle and may reflect recycling of terrigenous sediments. The calculated weathering flux of Cl from the continents is quite small compared to the total Cl content of seawater (<8–34 %), suggesting that Cl in seawater is mainly derived from outgassing of the mantle and/or late volatile accretion. On the other hand, the significantly higher Br and I contents in terrigenous organic-rich sediments compared to those of crystalline bedrocks suggest that significant amounts of Br and I were transported from the oceans to the continents.

In-situ growth of anionic covalent organic frameworks efficaciously enhanced the monovalent selectivity of anion exchange membranes

The development of monovalent selective ion exchange membranes with excellent performance is required owing to the continuous refinement of electrodialysis technology. Here, a tailored strategy for the in-situ growth of a sulfonate-rich covalent organic framework (sCOF) on the anion exchange membrane (AEM) was proposed to construct an ideal platform (sCOF/aAEM3) for superior anion separation. Specifically, sCOF and AEM were covalently linked (-C=N-) to ensure the high stability of the modified layer, which is an important application parameter. The sCOF layer, with a thickness of approximately 2.97 μm, was formed using the Bottom-Up in-situ growth method. The appearance of sulfonate in the pores of sCOF induced a strong electronegativity of −38.85 eV at pH = 7. The periodic structure of sCOF achieved a regularly sulfonate arrangement, which maximized the utilization of the functional group, causing strong electrostatic repulsion on SO42−. The electrodialysis process showed that sCOF/aAEM3 exhibited a superior perm-selective performance (PSO42−Cl− =18.92). In addition, the unique open 1D channel of sCOF endowed sCOF/aAEM3 with an enhanced ion flux of Cl− from 2.96 to 3.35 × 10−8 mol cm2 s−1. This facile strategy has been used for two other commercial AEMs having elevated perm-selectivity, which indicates the great potential for extensive applications.

Recovery of the N,N-Dibutylimidazolium Chloride Ionic Liquid from Aqueous Solutions by Electrodialysis Method.

Ionic liquids (ILs), named also as liquid salts, are compounds that have unique properties and molecular architecture. ILs are used in various industries; however, due to their toxicity, the ILs’ recovery from the postreaction solutions is also a very important issue. In this paper, the possibility of 1,3-dialkylimidazolium IL, especially the N,N-dibutylimidazolium chloride ([C4C4IM]Cl) recovery by using the electrodialysis (ED) method was investigated. The influence of [C4C4IM]Cl concentration in diluate solution on the ED efficiency was determined. Moreover, the influence of IL on the ion-exchange membranes’ morphology was examined. The recovery of [C4C4IM]Cl, the [C4C4IM]Cl flux across membranes, the [C4C4IM]Cl concentration degree, the energy consumption, and the current efficiency were determined. The results showed that the ED allows for the [C4C4IM]Cl recovery and concentration from dilute solutions. It was found that the [C4C4IM]Cl content in the concentrates after ED was above three times higher than in the initial diluate solutions. It was noted that the ED of solutions containing 5–20 g/L [C4C4IM]Cl allows for ILs recovery in the range of 73.77–92.45% with current efficiency from 68.66% to 92.99%. The [C4C4IM]Cl recovery depended upon the initial [C4C4IM]Cl concentration in the working solution. The highest [C4C4IM]Cl recovery (92.45%) and ED efficiency (92.99%) were obtained when the [C4C4IM]Cl content in the diluate solution was equal 20 g/L. Presented results proved that ED can be an interesting and effective method for the [C4C4IM]Cl recovery from the dilute aqueous solutions.

Select Amino Acids Increase Anion Secretion in Human Bronchial Epithelial Cells (HBEC) with F508del and Nonsense Mutations: Alternative Approach to Restoring Airway Anion Secretion in Cystic Fibrosis

ObjectiveChloride and bicarbonate transport across the apical membrane via CFTR is critical for homeostasis of airway surface liquid and mucociliary clearance. Cystic fibrosis (CF) is caused by mutations in the CFTR gene resulting in mucus buildup, bacterial colonization, inflammation and respiratory insufficiency. F508del and nonsense mutations are the most common mutations characterized by defective protein processing and trafficking (F508del) or early termination of CFTR synthesis (G542X, R1162X). A combination of CFTR modulators (VX445/661/770; VX) has largely improved CFTR function in patients with F508del but is ineffective in nonsense mutations. We have shown that select amino acids (SAA) can modulate trafficking and activity of CFTR and alternative anion‐secretory pathways, and thus could improve clinical outcomes in CF patients.HypothesisSAA can stimulate anion secretion in primary HBEC with F508del/F508del, F508del/R1162X and G542X/G542X mutation.MethodsTransepithelial short‐circuit current (Isc) was measured in differentiated HBEC treated with DMSO or VX for 24h and bathed in vehicle or SAA in Ussing chambers. After blocking ENaC with benzamil, benzamil‐insensitive (anion) Isc was either continuously recorded for 90min, or sequentially blocked with CFTRinh172, CaCCinhA01 and bumetanide in 15min intervals. Isotope (36Cl) flux studies and whole‐cell patch clamp technique were used to confirm chloride movements, and CFTR and alternative anion‐secretory channel expression was analyzed by immunofluorescence.ResultsAnion Isc increased in all mutations and was more sustained when exposed to SAA compared to vehicle (F508del: 15.4±0.5 vs 1.4±0.2; R1162X: 19.4±0.3 vs 2.3±0.3; G542X: 17.2±0.5 vs 1.6±0.2 µA.cm‐2; P&lt;0.001). SAA recovered 48.7, 57.3 and 40.9% of normal Isc (21.9±0.5 µA.cm‐2). Treatment with VX increased anion Isc in F508del and R1162X (11.4±0.7 and 5.7±0.4 µA.cm‐2; P&lt;0.001) but not in G542X (1.7±0.2 µA.cm‐2). In F508del, the CFTR response increased from 20.7% (non‐treated cells) to 32.9 and 85.5% of the anion Isc when treated with SAA or VX, and in R542X from 3.7% to 46.3 and 16.0%, respectively. Both, SAA and VX did not affect CaCC, but SAA increased the bumetanide‐sensitive Isc from 31.0 to 50.5% in F508del, and from 33.3 to 56.3% in R1162X, while VX reduced the bumetanide response to 5.4 and 4.5%. Isotope flux studies showed that SAA (‐0.21±0.08 μEq.h‐1.cm‐2) and VX (‐0.19±0.02 μEq.h‐1.cm‐2) increased net Cl‐ secretion in F508del when compared to vehicle (‐0.03±0.01 μEq.h‐1.cm‐2; P&lt;0.05). SAA, but not VX increased Cl‐ secretion in G542X (‐0.21 0.07 vs ‐0.08±0.02 μEq.h‐1.cm‐2). In patch clamp recordings, SAA and VX resulted in a significant reduction in CFTRinh172 whole cell current in F508del. Immunofluorescence imaging demonstrated increased CFTR and alternative anion‐secretory channel expression along the apical membrane in SAA cells while VX showed increased expression of only CFTR.ConclusionsThese studies demonstrate that SAA stimulates anion current and increases Cl‐ secretion via CFTR and alternative secretory pathways in different mutations, and could be beneficial in nonsense mutations but needs further investigation.

Water/rock interactions, chemical weathering and erosion, and supergene enrichment in the Tapira and Catalão I alkaline‑carbonatite complexes, Brazil

Alkaline‑carbonatite complexes from the Alto Parnaíba Igneous Province (APIP) host important supergene concentrations of Nb, REE, P, and Ti. To quantify water/rock interaction and the interplay of chemical weathering and erosion that results in supergene enrichment, the chemistry of solutions draining the Tapira and Catalão I complexes were studied and the transfer of elements within and out of the weathering profiles quantified. Ca2+ and HCO3− are the main ions in surface water samples draining both watersheds, with an average annual flux of 49 t/km2/a of dissolved load. Total dissolved loads are highest during the summer (wet) months. The annual fluxes of Cl−, PO43− and NO3− yield negative values, suggesting significant input of these species from rainwater. The fluvial transport of dissolved elements due to silicate weathering, carbonate dissolution and rainfall input is ~26, 3 and 19 t/km2/a at Tapira and 29, 3 and 18 t/km2/a at Catalão I. Chemical weathering rates of alkaline rocks are ~4 m/Ma at Tapira and ~5 m/Ma at Catalão I. Constitutive mass balance suggests an eroded rock column of 84 m at Tapira and 39 m at Catalão I, with long-term erosion rates of 1.3 and 0.9 m/Ma, respectively. In contrast, long-term weathering rates were 3.0 m/Ma at Tapira and 2.4 m/Ma at Catalão I. Internal collapse of saprolites due to mass loss creates internal basins with an overburden of soils, locally transported material and lake sediments. Carbonate congruent dissolution, silicate incongruent dissolution and hydrolysis, and phosphate and oxide (pyrochlore) dissolution-reprecipitation are the main water/rock interactions in the Tapira and Catalão I alkaline‑carbonatite complexes that promote the enrichment of primary and secondary minerals and produce supergene P, Ti, Nb and REE deposits in the isalteritic saprolites; Ti is residually enriched in the alloteritic saprolite at Tapira.

Study on the Effectiveness of Simultaneous Recovery and Concentration of 1-Ethyl-3-methylimidazolium Chloride Ionic Liquid by Electrodialysis with Heterogeneous Ion-Exchange Membranes.

Due to the extensive range of ionic liquids (ILs) used in industry, an efficient recovery method is needed. In this study, the effectiveness of a simultaneous concentration and recovery method was investigated for 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), an IL that was recovered using electrodialysis (ED). The optimal operational parameters for electrodialytic recovery were determined empirically. The variables that were investigated included the concentration of IL, applied voltage, linear flow velocity and the diluate-to-concentrate volume ratio. The recovery of [Emim]Cl, the concentration degree, the [Emim]Cl flux across membranes, the current efficiency, as well as the energy consumption were determined. The results of the experiments confirmed that [Emim]Cl concentration and recovery can be achieved using ED. The highest ED efficiency was obtained when a 2 V electric potential per one membrane pair was applied, using a 2 cm/s linear flow velocity, and by adjusting to 0.2 M IL in the feed solution. By using ED, a 2.35-fold concentration of [Emim]Cl with a recovery of 90.4% could be achieved when the diluate-to-concentrate volume ratio was 2. On the other hand, a 3.35-fold concentration of [Emim]Cl with a recovery of 81.7% could be obtained when the diluate-to-concentrate volume ratio was increased to 5.

134 Percutaneous Absorption of Chlormethine Gel in Human Skin: In Vitro Permeation Testing

The synthetic DNA-alkylating agent chlormethine (CL, or mechlorethamine) is commercially available as 0.016% CL gel purposely developed and indicated to treat mycosis fungoides cutaneous T-cell lymphoma, with a positive benefit/risk ratio. This study evaluated the permeation of CL from gel formulation via in-vitro permeation testing (IVPT) using ex vivo human skin (dermatomed and epidermal membrane) mounted on flow-through cells. Healthy barrier-competent skin, harvested from elective abdominal surgeries, was either dermatomed to a thickness of 500μm (real skin ∼2000μm) or separated into epidermal membranes. Skin samples were mounted on to flow-through diffusion cells designed to mimic physiological/anatomical skin in situ. CL gel was applied to the surface at 10mg/cm2 and receptor solution samples were automatically collected every 2h postdose for 24h. Liquid chromatography-tandem mass spectrometry was used to quantify mean cumulative CL (ng/cm2), CL flux rates (ng/cm2/h) and residual CL from skin surface (ng). In dermatomed skin (1 donor; 7 replicates) and epidermal membrane (3 donors; 7 replicates), CL in receptor solution rose from 2h postdose to plateau at ∼8–10h. Mean cumulative CL that permeated through dermatomed skin and epidermal membrane were 40ng/cm2 (2.5% of applied dose) and 73ng/cm2 (4.6% of applied dose), respectively after 24h. Mean CL flux through dermatomed skin and epidermal membranes was 5.2ng/cm2/h peaking at ∼4h and 10.8ng/cm2/h peaking at ∼2h, respectively. Mean residual CL from the skin surface of epidermal membranes at 24h was 21ng (1.3% of applied dose). No residual CL was detectable from the dermatomed skin surface. This IVPT demonstrates CL 0.016% gel permeation profiles were similar for dermatomed skin and epidermal membrane. However, CL gel appeared to deliver more CL with a higher CL flux in epidermal membrane than dermatomed skin, suggesting that minimal CL levels pass through epidermal tissue and reach dermal tissue.

Intricacies of GABAA Receptor Function: The Critical Role of the β3 Subunit in Norm and Pathology

Neuronal intracellular chloride ([Cl−]i) is a key determinant in γ-aminobutyric acid type A (GABA)ergic signaling. γ-Aminobutyric acid type A receptors (GABAARs) mediate both inhibitory and excitatory neurotransmission, as the passive fluxes of Cl− and HCO3− via pores can be reversed by changes in the transmembrane concentration gradient of Cl−. The cation–chloride co-transporters (CCCs) are the primary systems for maintaining [Cl−]i homeostasis. However, despite extensive electrophysiological data obtained in vitro that are supported by a wide range of molecular biological studies on the expression patterns and properties of CCCs, the presence of ontogenetic changes in [Cl−]i—along with the consequent shift in GABA reversal potential—remain a subject of debate. Recent studies showed that the β3 subunit possesses properties of the P-type ATPase that participates in the ATP-consuming movement of Cl− via the receptor. Moreover, row studies have demonstrated that the β3 subunit is a key player in GABAAR performance and in the appearance of serious neurological disorders. In this review, we discuss the properties and driving forces of CCCs and Cl−, HCO3−ATPase in the maintenance of [Cl−]i homeostasis after changes in upcoming GABAAR function. Moreover, we discuss the contribution of the β3 subunit in the manifestation of epilepsy, autism, and other syndromes.

The anion exchanger PAT-1 (Slc26a6) does not participate in oxalate or chloride transport by mouse large intestine.

The membrane-bound transport proteins responsible for oxalate secretion across the large intestine remain unidentified. The apical chloride/bicarbonate (Cl-/HCO3-) exchanger encoded by Slc26a6, known as PAT-1 (putative anion transporter 1), is a potential candidate. In the small intestine, PAT-1 makes a major contribution to oxalate secretion but whether this role extends into the large intestine has not been directly tested. Using the PAT-1 knockout (KO) mouse, we compared the unidirectional absorptive ([Formula: see text]) and secretory ([Formula: see text]) flux of oxalate and Cl- across cecum, proximal colon, and distal colon from wild-type (WT) and KO mice in vitro. We also utilized the non-specific inhibitor DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid) to confirm a role for PAT-1 in WT large intestine and (in KO tissues) highlight any other apical anion exchangers involved. Under symmetrical, short-circuit conditions the cecum and proximal colon did not transport oxalate on a net basis, whereas the distal colon supported net secretion. We found no evidence for the participation of PAT-1, or indeed any other DIDS-sensitive transport mechanism, in oxalate or Cl- by the large intestine. Most unexpectedly, mucosal DIDS concurrently stimulated [Formula: see text] and [Formula: see text] by 25-68% across each segment without impacting net transport. For the colon, these changes were directly proportional to increased transepithelial conductance suggesting this response was the result of bidirectional paracellular flux. In conclusion, PAT-1 does not contribute to oxalate or Cl- transport by the large intestine, and we urge caution when using DIDS with mouse colonic epithelium.

Limnological response to the Laacher See eruption (LSE) in an annually laminated Allerød sediment sequence from the Nahe palaeolake, northern Germany

This paper presents evidence for a limnological response to the Laacher See eruption (LSE) as detected in lake sediments from Nahe, northern Germany. The sediment section of the Allerød period dating to between 13 422 and 12 708 cal. a BP is preserved in annual laminations. Within this section, the LSE was identified as a cryptotephra layer (12 944±44 cal. a BP). Microfacies analysis, continuous high‐resolution geochemical measurements and pollen analyses enabled a high‐resolution reconstruction of environmental change. The older part of the Allerød (c. 13 422 to 12 943 cal. a BP) was characterized by relatively stable sedimentation conditions. Evidence for windier conditions dating to c. 13 160 to 13 080 cal. a BP probably reflects the Gerzensee oscillation. Pronounced changes of the lake sedimentation followed the LSE. Four unusually thick varves with increased amounts of allochthonous material indicate serious disturbance of the local environment immediately after the LSE, related to increased storminess and/or the occurrence of high intensity rainfall events. A pronounced reduction of biogenic silica accumulation for c. 60 years after the LSE could reflect a period of acidification. Indications of a simultaneous lake level increase until c. 60 years after the LSE are in line with the supposed reduced evapotranspiration associated with cooler conditions. About 120 years after the LSE, increased oxygen access at the lake bottom, allochthonous input and Cl fluxes point to an onset of increasingly stronger westerly winds, probably as a long‐term response to the LSE. This supports the idea of a southward shift of the mid‐latitude westerlies wind system within the interval between the LSE and the beginning of the Younger Dryas. The pace of the southwards shift of this wind system decreased from 10 km a−1 in the initial phase (40–120 years after LSE) to 6 km a−1 in the later phase (120–200 years after LSE).

CrossTalk proposal: Apical NKCC1 of choroid plexus epithelial cells works in the net inward flux mode under basal conditions, maintaining intracellular Cl- and cell volume.

CrossTalk proposal: Apical NKCC1 of choroid plexus epithelial cells works in the net inward flux mode under basal conditions, maintaining intracellular Cl- and cell volume.

Physico-chemical characterization and sink mechanism of atmospheric aerosols over South-west India

The properties of the atmospheric aerosols depend on the source region and on the modifications that occur during their transport in the air. We have studied physical and chemical properties of aerosols along with their sink mechanism over two locations in southwest India, an urban site (Pune) and well-established climate observatory at Sinhagad (SINH), which represents rural and high altitude site. The ground-based measurements of aerosols, together with their radiative properties in this study have provided means to understand the observed variability and the impact on the aerosol radiative properties effectively over this region. The annual mean elemental carbon concentration (3.4 µg m− 3) at Pune was observed about three times higher compared to SINH (1.3 µg m− 3), indicating strong emissions of carbon-rich aerosols at the urban location. Aerosol optical properties were derived using the OPAC model which were used to compute the Aerosol radiative forcing (ARF) over both stations calculated using SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model shows pronounced seasonal variations due to changes in aerosol optical depth and single scattering albedo at both locations. The year-round ARF was 4–5 times higher over Pune (31.4 ± 3.5 Wm− 2) compared to SINH (7.2 ± 1.1 Wm− 2). The atmospheric heating rate due to aerosols shows a similar pattern as ARF for these locations. The heating was higher in the wintertime, ~ 0.9–1.6 K day− 1 at Pune, and ~ 0.3–0.6 K day− 1 at SINH. The estimated scavenging ratio was found high for NO3− and Ca.2+. The wet deposition fluxes of Cl−, SO42−, Na+, Mg2+ were observed higher for SINH as compared to Pune, due to the high amount of rain received at SINH.

Continuous measurements of riverine chemical constituents reveal the environmental effect of the 2014–2015 Bárðarbunga eruption in Iceland

The 2014–2015 Bárðarbunga eruption caused one of the most intense and widespread volcanic derived air pollution events in centuries. The volcanic plume was tracked all the way to central Europe. Volcanic gas and aerosol dissolved in precipitation and accumulated as aerosol and snow on land in Iceland. Here we report on the continuous monitoring of discharge and dissolved constituents of a direct runoff river located 85 km from the eruption site during the entire snowmelt period in 2015. Osmotic samplers collected continuous water samples so short-lived flood peaks would not be missed. Comparison between results from this 2015 study and data from 1998 to 2013 from the same river showed that average pH was 0.2 units lower in 2015 and the Cl and SO4 average concentration were 36% and 38% higher than prior to the eruption, respectively. Integrated riverine fluxes of H+ and SO4 were two to three times higher during summer 2015 than in the control years, and the Cl flux was 37% higher. The measured excess H+ flux was however only a small fraction of the calculated excess H+ flux stemming from excess SO4 and Cl fluxes in 2015 which can be explained by ion-exchange in the catchment soil, water-rock interaction consuming protons within the catchment, and by elevated sea spray derived Cl and SO4 due to relatively high wind speed during the 2014–2015 winter. In addition, the small H+ increase in the river water can be the cause of the less than expected excess SO4 riverine flux, normalised to the total measured volcanogenic SO2 and HCl emission fluxes (11 Tg/0.1 Tg), which underscores the slow oxidation of SO2 to SO4 in relatively dry weather conditions and reduced sunlight during winter in Iceland. Despite being sensitive to riverine pH and aluminium changes, freshwater ecosystem was not threatened by the eruption, since it did not cause large pH changes and the dissolved aluminium concentration was always low during the study period. This study provided the means to quantify the integrated chemical fluxes and the impact of volcanic emissions on a riverine system in the vicinity of the eruption site and the implication of increased chemical fluxes of solutes of volcanic origin on the system.

Sources, fate, and flux of geothermal solutes in the Yellowstone and Gardner Rivers, Yellowstone National Park, WY

The total discharge and thermal output from the numerous hydrothermal features in Yellowstone National Park (YNP) can be estimated from the chloride (Cl) flux in the Madison, Yellowstone, Falls, and Snake Rivers. Monitoring the Cl flux in these four major rivers provides a holistic view of the hydrothermal output from YNP and changes in the Cl flux may indicate changes in geothermal or magmatic activity. In this study, the source, fate, and flux of geothermal solutes in the Yellowstone River and Gardner Rivers were determined. Beginning in 2012, the fluxes of geothermal solutes, including Cl, were determined at monitoring sites in the Yellowstone and Gardner Rivers downstream of geothermal inputs within YNP. A method was developed using specific conductance as a surrogate measure for solute concentrations at these monitoring sites. Combining continuous (15-min) specific conductance and discharge data, Cl and other geothermal solute fluxes were determined and approximately 32% of the Cl flux exiting YNP is from the Yellowstone River watershed. Synoptic sampling of river water and discharge measurements were performed during low-flow conditions of September 2014 allowed for the determinations of geothermal solute sources and their downstream fate. Thus, the contribution of geothermal solutes from the various geothermal areas at the downstream monitoring sites was quantified. The thermal features draining into Yellowstone Lake account for 34% of the Cl flux at the Yellowstone River monitoring site which is located approximately 5 km north of YNP. The Gardner River, which captures geothermal water from Mammoth Hot Springs, is responsible for 22% of the Cl at the Yellowstone River monitoring site. Because the Yellowstone River watershed is large and contains numerous thermal areas, knowing the source and fate of geothermal solutes is import baseline information that can be used to identify future changes in thermal activity.

Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Bottom-up Cu deposition in metallized through silicon vias (TSV) depends on a co-adsorbed polyether–Cl− suppressor layer that selectively breaks down within recessed surface features. This work explores Cu deposition when formation of the suppressor blocking layer is limited by the flux of Cl−. This constraint leads to a transition from passive surfaces to active deposition partway down the via sidewall due to coupling between suppressor formation and breakdown as well as surface topography. The impact of Cl− concentration and hydrodynamics on the formation of the suppressor surface phase and its potential-dependent breakdown is examined. The onset of suppression breakdown is related to the local Cl− coverage as determined by the adsorption isotherm or transport limited flux. A two-additive co-adsorption model is presented that correlates the voltammetric potential of suppression breakdown with the depth of the passive-active transition during TSV filling under conditions of transport limited flux and incorporation of Cl−. The utility of potential waveforms to optimize the feature filling process is demonstrated. At higher Cl− concentrations (≥80 μmol/L), sidewall breakdown during Cu deposition occurs near the bottom of the via followed by a shift to bottom-up growth like that seen at higher Cl− concentrations.