Understanding arsenic-ulexite interactions in evaporite environments: Evidence from XRPD, micro-XRF, micro-FT-IR, and XPS studies.

World-class borate deposits often form from As-rich waters, this study addresses the understudied association of arsenic (As) species with evaporite borates, focusing on the Puna region's borate deposits (Central Andes of Argentina). The research aims to characterize the association between borate minerals and high As concentrations in brines and thermal waters. To achieve this, five borate samples were collected from the Olaroz salt flat nucleus and thermal springs, alongside associated water samples. Comprehensive analytical techniques, including ICP-MS, ICP-OES, synchrotron-based micro-XRF, XRPD, Rietveld analysis, micro-FT-IR, and XPS, were employed to determine bulk and surface chemical compositions, mineral identification, and solid speciation of As and boron. The study reveals that under oxidizing conditions and in absence of organic matter, aqueous arsenic species interact with ulexite through a stepwise process involving charge neutralization, cationic bridge formation, and surface complex formation with polyborate and As(V) oxyanions. However, in environments associated with microbial mats or organic-rich sediments, the dissolved As(V) is reduced to As(III), which forms complexes with functional groups of organic matter. The coexistence of As(III) and As(V) in specific layers suggests potential remediation strategies targeting organic matter for the removal of the more toxic As(III) in similar geological settings.

The role of efflorescent salts associated with sulfide-rich mine wastes in the short-term cycling of arsenic: Insights from XRD, XAS, and µ-XRF studies.

The evaporation of As-rich leachates generated by the weathering of sulfide-rich mine wastes accumulated in abandoned tailing dams of the La Concordia mine, triggers the widespread precipitation of saline crusts and efflorescences. Because these salts are highly soluble, they may release high concentrations of arsenic after rainfall events. Thus, the goal of this work is to assess the solid speciation of As in these efflorescences, which may help to understand the short-term cycling of As in the site. The results reveal that As is present only as As(V), while its capacity to be retained in the salts highly depends on their mineralogical composition. Hydrous sulfates, such as gypsum and epsomite show a very low capacity to scavenge As, while copiapite retains the highest concentrations of this element. The spectroscopic evidences suggest that in this mineral, As(V) is included within the lattice, substituting sulfate in the tetrahedral sites. Because copiapite is highly soluble, it may be considered as one of the most important transient reservoirs of As in the site that can release high concentrations of this hazardous pollutant during the occasional rainfall events produced during the wet season.

Synchrotron XAS study on the As transformations during the weathering of sulfide-rich mine wastes.

This paper describes the weathering processes that occurred across two tailing dumps in the Concordia mine (Puna of Argentina) with the purpose of evaluating the formation of secondary As-bearing minerals due to arsenopyrite alteration. After 30 years of exposure, the gradual oxidation of the wastes produced a number of secondary mineral phases containing As in different chemical arrangements. Synchrotron-based X-ray absorption spectroscopy was used to determine both, As and Fe solid speciation and to identify the formed As-bearing minerals. The results reveal that in the first stages of oxidation, As released from arsenopyrite is adsorbed/substituted in the jarosite structure partially inhibiting its dissolution. When pH values in the system slightly increase As-jarosite transforms into schwertmannite, where the released As could be re-adsorbed or co-precipitated. When the available adsorption sites become oversaturated with As, the precipitation of amorphous ferric arsenates may occur. The latter, likely constitute the more labile As fractions in the sediments and are therefore the main phases contributing As to the nearby environments. These amorphous and labile phases are more abundant in the uppermost layers of the profiles, where oxidation has taken place for a more prolonged time-lapse. The described transformations are enhanced by the acidic pH, the absence of minerals attenuating the acidity and the high sulfate and As concentrations in pore water.

Mineralogical control on arsenic release during sediment-water interaction in abandoned mine wastes from the Argentina Puna.

The sulfide-rich residues of La Concordia mine, Argentina Puna, are accumulated in tailing dams that remained exposed to the weathering agents for almost 30years. In such period of time, a complex sequence of redox and dissolution/precipitation reactions occurred, leading to the gradual oxidation of the wastes and the formation of weathering profiles. The sources of arsenic in the wastes were analyzed by XRD and SEM/EDS analysis while a standardized sequential extraction procedure was followed to define solid As associations. In addition, the release of As during sediment-water interaction was analyzed in a period of 10months. The results indicate that primary As-bearing minerals are arsenian pyrite and polymetallic sulfides. As-jarosite and scarce arsenates are the only secondary As-bearing minerals identified by XRD and SEM/EDS. However, the rapid release (i.e., <1h) of arsenic from suspensions of the studied sediments in water, seems to be associated to the dissolution of highly soluble (hydrous)sulfates, as it was determined in samples of the efflorescences that cover the entire site. Contributions from the more abundant As-jarosite are also expected in longer periods of sediment-water interaction, due to its low rate of dissolution in acid and oxic conditions. Finally, near 30% of As remains adsorbed onto Fe (hydr)oxides thus representing a hazardous reservoir with the potential of mobilizing As into porewaters and streamwaters if the acidic and oxidizing conditions that predominate in the region are altered.

Mechanisms of fluoride release in sediments of Argentina's central region.

We analyze the sources and mechanisms that control the release of fluoride from sediments collected from two types of aquatic reservoirs in the central region of Argentina: 1) mountainous rivers draining crystalline rocks from the Sierras Pampeanas ranges, and 2) shallow aquifers in loessic sediments. The assessment was performed on the basis of experimental work and the study of chemical and mineralogical characteristics of sediments in contact with F-rich waters of the studied region. The chemical and mineralogical compositions of sediments were analyzed by ICP/OES, DRX, and SEM-EDS. Batch experiments were conducted to evaluate the kinetics of fluoride release under variable pH and ionic composition of the solution. The enhanced release of fluoride at more acidic pH, the inhibition of release in Ca-rich solutions and the positive significant linear trends between Ca(2+) and fluoride concentrations suggest that the dissolution of a Ca/F-bearing phase (like fluorapatite) strongly controls the dynamics of fluoride in the early stages of water-sediment interaction, particularly under acidic conditions. Calculations revealed that the dissolution of an amount of FAp equivalent to that estimated in the studied sediments may widely account for the values measured in the leaching experiments at pH6, whatever the dominant cation in the solution. Under such conditions, dissolution of FAp (present as coatings onto glass surfaces or as detritic grains) is likely the major primary source of fluorine in the studied sediments. Contribution from biotite may be also considered as a source in fluvial sediments. When adequate surfaces are present the released anions may partially be scavenged from the solution by adsorption at acidic pH. Increasing alkalinity in the aquatic reservoirs may then release the adsorbed fluoride through desorption or through competition with other anionic species. Comparing both mechanisms, dissolution predominates at lower pH while desorption is the main contribution under alkaline conditions.

Surface properties of sediments from two Argentinean reservoirs and the rate of phosphate release.

This article reports the surface properties (electrophoretic mobility, surface charge and specific surface area (SSA)), and phosphate release rates of sediments from two Argentinean reservoirs. Even though sediments are a heterogeneous mixture of minerals with different charging behavior, electrophoresis reveals that all sediment particles are negatively charged in the pH range 3-9. Iron and aluminum oxides, which usually carry a net positive charge at low pH, seem to be forming aggregates with negatively charged minerals and/or carrying a net negative charge due to the presence of organic matter. The phosphate release rate increased by increasing pH and temperature, and depended linearly on the SSA of the sediments. These data, together with the high activation energy of the process, indicate that the rate-controlling process is a chemical reaction occurring at the solid-water interface, and not a diffusion process. The rate-controlling step seems to be the breaking of bonds between phosphate and surface groups, breaking that should be preceded by one or more deprotonation steps at the surface and favored by electrostatic repulsion between the negative charge surface and the phosphate anion.

Nephrological indications in combined liver-kidney transplantation.

In isolated liver transplantation pretransplant renal failure is a major mortality risk, there are no guidelines at the moment to establish the indications for a combined liver-kidney transplantation (LKT). In irreversible chronic renal failure (CRF) not on dialysis, nephrological evaluation is required to assess the need for a simultaneous kidney transplantation. There are no experiences about the functional contribution of native kidneys post-LKT. Herein we have reported the case of two patients who underwent LKT in 2004 due to CRF, not yet on dialysis. At the moment of LKT, the first patient (polycystic kidney disease) had a glomerular filtration rate (GFR) = 29 mL/min, and the second recipient (vascular nephropathy and diabetes), a GFR = 33 mL/min. In both cases we did not observe delayed graft function. At discharge the serum creatinine was 1.1 and 1.0 mg/dL, respectively, which was maintained during follow-up. In both cases renal scintigraphy with Tc-99 DMSA was performed to evaluate the functional contributions of transplanted versus native kidneys. In the first case scintigraphy at 9 months after LKT demonstrated an 81% contribution from the transplanted kidney, 9% from the right and 10% from the left native kidneys. In the second case, at 3 months after LKT, the functional contributions were 76%, 10%, and 14%, respectively. The transplanted kidney nephron mass may avoid the need for hemodialysis in the early posttransplant period; in the midterm it may help to maintain residual renal function. As in other combined transplant programs (heart-kidney, kidney-pancreas) with irreversible CRF, a GFR < or = 30 to 35 mL/min may be an indication for LKT, but we need more experience.

Molecular adsorbent recirculating system (MARS) application in liver failure: clinical and hemodepurative results in 22 patients.

PURPOSE: Acute liver failure (ALF) and acute on chronic liver failure (ACLF) still show a poor prognosis. MARS was used in 22 patients with ALF or ACLF to prolong patient survival for liver function recovery or as a bridge to transplantation. DESIGN: Evaluation of depurative efficiency, biocompatibility, hemodynamics, encephalopathy (HE) and clinical outcome. PROCEDURES: During 71 five-hour sessions we evaluated (0', 60', 120', 180', 240', 300'): bilirubin, ammonia, cholic acid (CCA), chenodeoxycholic acid (CCDCA), leukocytes, platelets, hemoglobin and mean arterial pressure (MAP). Serum creatinine, electrolytes, cardiac output, cardiac index (bioimpedence) and HE (West Haven Criteria score) were evaluated at 0' and 300'. STATISTICAL METHODS AND OUTCOME MEASURES: Student's t-test for pre- vs. end-session values was used. For bilirubin and ammonia the correlation test was made between pre- and end-session values and between pre-session values and removal rates (RRS). MAIN FINDINGS: Survival was 90.9% at 7 days, 40.9% at 30 days. Pre- vs. end-session: bilirubin from 37.2 +/- 12.5 mg/dL to 24.9 +/- 8.9 mg/dL (p < 0.01), ammonia from 88.0 +/- 60.4 micromol/L to 43.6 +/- 32.9 micromol/L (p < 0.01), CCA from 42.8 +/- 21.0 micromol/L 18.2 +/- 9.8 micromol/L (p < 0.01), CCDCA from 26.3 +/- 6.3 micromol/L to 15.7+/-7.6 micromol/L (p<0.01). The correlation test between pre-session values of bilirubin and ammonia vs. RR S was respectively 0.32 (p = 0.01) and 0.30 (p = 0.04). Leukocytes, platelets and hemoglobin remained stable. MAP increased from 82.0 +/- 12.0 mmHg to 87.0 +/- 13.0 mmHg (p < 0.05), West Haven Criteria score decreased from 2.7 +/- 0.7 to 0.7 +/- 0.7 (p < 0.001). CONCLUSION: MARS treatment led in all patients to an improvement of clinical, hemodynamic and neurological conditions, with significant reduction in the hepatic toxins blood level. Treatment biocompatibility and tolerance were satisfactory.

PDGF-AB release during and after haemodialysis procedure.

BACKGROUND: During haemodialysis blood membrane contact causes the release of the content of platelet alpha-granules, which contain platelet-derived growth factor (PDGF). In view of its possible role in accelerated atherosclerotic processes, we evaluated the intra- and post-dialytic changes in PDGF-AB serum levels during haemodialysis sessions performed using a cellulosic membrane. METHODS: Using the ELISA method, PDGF-AB, platelet factor-4 (PF4) and beta-thromboglobulin (beta-TG) levels were determined in peripheral blood, as well as in arterial and venous haemodialyser lines, in 10 patients each of whom underwent five consecutive dialysis sessions with a CU membrane. Blood samples were taken at 0, 15, 30, 60, 120, 180 and 240 min during dialysis and at 1, 4 and 20 h after the end of the session. In the same group of patients the levels of the same molecules were also determined after a heparin bolus injection of 4500 IU, blood samples were taken at 0, 15 and 30 min after injection of the bolus. RESULTS: PDGF-AB serum levels increased, remained consistently high during the haemodialysis session (in particular +134+/-20% after 30 min, P<0.001, and +140+/-5% after 240 min, P<0.001) and returned to basal values only after 20 h following the end of the session. PF4 and beta-TG showed a similar trend to PDGF. The heparin bolus injection caused only a small increase (+15+/-5% at 30 min) in PDGF-AB serum levels. CONCLUSIONS: PDGF-AB is released during dialysis mainly as consequence of the blood-membrane contact and it returns only slowly to basal values.

Mismatch-specific anti-HLA antibody production following aorta transplants.

In this study, we have investigated the nature and magnitude of the immunological response after implantation of human aortic segments. Five recipients of aortic segment replacement were studied for anti-HLA antibody production (specificity and Ig class), CD3, CD4, and CD8 T cell subpopulation dynamics, and aortic wall thickness. Mismatch-specific IgG antibodies to HLA class I and HLA class II antigens were first detected 1-3 months after implantation and persisted in high concentrations for at least 1 year. Computer tomography scanning showed a progressive thickness of the aortic wall. Also the absolute number of CD3, CD4, and CD8 positive lymphocytes increased progressively after implantation. In conclusion, as was observed earlier for heart valve allografts, human implanted aortic segments induce a strong anti-HLA antibody response in recipients. We speculate that these antibodies have the potential to harm the implant, for example, by having an impact on luminal narrowing.

The presence of posttransplant HLA-specific IgG antibodies detected by enzyme-linked immunosorbent assay correlates with specific rejection pathologies.

Posttransplant monitoring of anti-HLA antibodies with routine techniques gives unsatisfactory results due to a variety of technical limitations. We investigated how a new alternative technique correlates with posttransplant clinical events. A total of 313 nonselected serum samples from 136 patients were screened by an ELISA utilizing captured soluble HLA class I antigens. We observed the absence of anti-HLA antibody production in acute rejection cases responding to standard antirejection therapy. On the other hand, we showed a clear presence of these antibodies in acute rejection episodes not responding to standard therapy (P<0.0001) and in chronic rejection (P<0.001). We conclude that routine posttransplant monitoring by ELISA offers early risk assessment that is crucial for proper immunosuppression and for antirejection therapy choice.

Antineutrophil cytoplasmic antibodies in inflammatory bowel disease: diagnostic tool or research procedure?.

Antineutrophil cytoplasmic antibodies, initially detected in the sera of patients with Wegener's granulomatosis and other forms of systemic vasculitides, have also been observed in patients with inflammatory bowel disease, with a higher prevalence in ulcerative colitis. In this study, we investigated the prevalence of these antibodies in the sera of 42 patients with ulcerative colitis and 48 patients with Crohn's disease, and the possible correlations with disease activity and extent, extraintestinal complications, and therapy. Antineutrophil cytoplasmic antibodies were found in 30 out of the 42 patients with ulcerative colitis (71.4%); only 16 out of the 48 patients (33.3%) with Crohn's disease were positive (p < 0.001), and the prevalent pattern was perinuclear. No correlations with disease activity and extent, extraintestinal complications, or surgical or medical treatment were found. Our data indicate that in the case of inflammatory bowel disease, the search for antineutrophil cytoplasmic antibodies still remains a research procedure and cannot be used for clinical diagnosis.

Effect of different dialysis membranes on platelet function. A tool for biocompatibility evaluation.

Intradialytic coagulative and platelet activation, one of the main consequences of blood-membrane contact, was studied in a group of 5 RDT patients with a comparative evaluation of 3 different dialytic membranes: Cuprophan (CU), Polysulfone (PS) and Cellulose Triacetate (CT). Each patient underwent 5 consecutive dialysis sessions with the above mentioned membranes. Intradialytic platelet activation was studied through a morpho-functional evaluation between the mean platelet volume (MPV) and Serotonin (S), beta-Thromboglobulin (beta-TG) and Platelet Factor 4 (PF4) serum levels. These determinations were made before HD (time 0) and after 30', 120', and 240'. We also checked the intradialytic status of thrombogenesis and fibrinolysis determining aPTT, thrombin time, fibrinogen, antithrombin III (AT III), alpha-2 antiplasmin and plasminogen, at the same time intervals. All membranes tested (CU, PS, CT) caused appreciable intradialytic platelet activation, above all after 15' and at the end of dialysis sessions, more marked for CU than PS or CT. In particular MPV showed a decrease throughout the session (-5% at 30' and -9% at 240') while S, beta TG and PF4 peripheral blood levels showed a significant increase at the same intervals with CU membrane. Lastly coagulative and fibrinolytic parameters showed no significant differences among any of the membranes tested.

Renal transplantation in patients with microscopic polyarteritis and antimyeloperoxidase antibodies: report of three cases.

This paper reports on 3 patients on renal dialysis for crescentic glomerulonephritis associated with microscopic polyarteritis (MPA) and antineutrophil cytoplasmic autoantibodies specific for myeloperoxidase (MPO-ANCAs). They successfully underwent renal transplantation from a cadaver donor 6-63 months after the onset of the disease, despite the persistence of antibodies at high titer. A triple immunosuppressive regimen including steroids, cyclosporin and azathioprine was used. One patient underwent transplantectomy for surgical complications 3 months later, while the serum creatinine was 2.0 mg/dl (178 mu mol/l): the remainder have a well-functioning graft after 21 and 38 months, no clinical sign of disease recurrence, and a MPO titer within the normal range. We conclude that MPA patients can undergo renal transplantation even if ANCAs persist at a high titer in the circulation.

Fibroblast proliferation over dialysis membrane: an experimental model for "tissue" biocompatibility evaluation.

The present study reports on a biological model based on fibroblast proliferation applied to 3 different types of flat-plate dialysis membrane, in order to ascertain whether the artificial materials currently used in hemodialysis cause in vitro cellular proliferation. The study plan we followed involved plate membrane isolation from non-used dialyzers and used dialyzers, observed through scanning electron microscopy (SEM) both before and after testing with human fibroblasts by means of cell culture. Fibroblast growth was assessed by phase contrast light microscopy examination and cytometric DNA content evaluation. Our investigations proved that the artificial materials we considered interact with fibroblast cultures. Noticeable proliferative response was observed both after contact with unused material and on mediation by the protein layer absorbed on the membrane surface at the end of dialysis sessions. In this last case fibroblast proliferative activity appeared higher than that observed with unused membranes, showing that the soluble molecules entrapped in the protein layer appeared able to exert a biological activity even in vitro tests.

Combined treatment in Wegener's granulomatosis with crescentic glomerulonephritis--clinical course and long-term outcome.

This study reports on 9 patients suffering from Wegener's granulomatosis (WG) with crescentic GN and severe systemic manifestations. On admission the mean serum creatinine was 10.9 +/- 5.1 mg/dl (4-20 mg/dl); 8 patients were oliguric and required dialysis treatment. Renal biopsy showed crescents in all cases, involving 66 to 100% of glomeruli. Patients were treated with a protocol including: a plasma exchange (PE) course; methylprednisolone; cyclophosphamide; and an antithrombotic agent (defibrotide). Clinical picture and renal function progressively improved in all patients within the first 4 weeks of treatment. After 1 month serum creatinine was 2.7 +/- 0.8 mg/dl and dialysis was no longer needed in any patient. Five relapses occurred in 3 patients 12-26 months after the onset of the disease, while they were still receiving immunosuppressive treatment. At follow-up (22 to 112 months: mean 71) all patients were alive with no clinical signs of disease activity. One patient was on regular dialysis while the others had a serum creatinine of 1.2-2.8 mg/dl (mean 1.9). Our results confirm that crescentic GN associated with WG can be successfully treated even when associated with severe clinical picture and suggest that PE can contribute to control the disease without increasing immunosuppression.

Low-dose angiotensin converting enzyme inhibitors: effect on renal function in normo- and hypertensive type 1 diabetic patients.

OBJECTIVES: To investigate the effect of low doses of the angiotensin converting enzyme inhibitor enalapril on renal haemodynamics and albuminuria in normotensive and hypertensive type 1 (insulin-dependent) diabetic patients with incipient or overt nephropathy. METHODS: Twenty-two type 1 (insulin-dependent) diabetic patients with persistent microalbuminuria or macroalbuminuria and normal serum creatinine were studied. Of all patients, 16 males and 6 females, age 45 +/- 13 years, diabetes duration 19 +/- 11 years, insulin dose 38 +/- 11 U/day, 10 were normotensive and 12 were hypertensive. After 3 months of run-in period the patients were assigned to treatment with 5 mg or 10 mg enalapril based on the presence of normotension or hypertension respectively. Before and after 6 months of treatment, renal function was assessed by evaluation of glomerular filtration rate (99m Tc-DTPA), renal plasma flow (131-I iodohippurate), filtration fraction and renal vascular resistance. Mean arterial pressure, albumin excretion rate, urinary urea excretion and glycated haemoglobin were also determined. RESULTS: Administration of enalapril resulted in both groups of patients in a significant fall in mean arterial pressure, albumin excretion rate, glomerular filtration rate, filtration fraction, and renal vascular resistance. Decreasing albumin excretion did not correlate with a drop in systemic blood pressure or filtration fraction. No significant variations were observed in renal plasma flow, in urinary urea excretion or in glycated haemoglobin. CONCLUSIONS: Our results suggest that low doses of enalapril are effective in influencing renal haemodynamics and reducing urinary albumin excretion in both normotensive and hypertensive type 1 (insulin-dependent) diabetic patients with incipient or overt nephropathy. The lowering effect of the angiotensin converting enzyme inhibitor on albuminuria seems to be independent of the action on systemic blood pressure and renal haemodynamic changes.

Plasma exchange treatment in rapidly progressive glomerulonephritis associated with anti-neutrophil cytoplasmic autoantibodies.

This study reports on 12 patients with acute renal failure due to biopsy-proven rapidly progressive glomerulonephritis and signs of systemic disease in whom antineutrophil cytoplasmic autoantibodies (ANCA) were detected by indirect immunofluorescence (IIF) on alcohol-fixed neutrophils and assessed in serial determinations by ELISA. The diagnosis was: Wegener's granulomatosis in nine patients who showed a diffuse cytoplasmic pattern at IIF (c-ANCA), and microscopic polyarteritis in three where a perinuclear pattern (p-ANCA) was seen. All patients underwent a course of plasma exchange - PE - (3-10 sessions per patient) associated with steroids and cyclophosphamide. The ANCA titer dropped steeply during PE in all cases and was followed by disappearance of systemic symptoms and renal function improvement within four weeks. After a follow-up period of 50 +/- 31.2 months all patients were alive without signs of disease activity; ten had stable renal function, with serum creatinine 1.8 +/- 0.7 mg/dl; two had entered regular dialysis treatment after 44 and 82 months. Our results suggest that the rapid removal of ANCA by means of PE can help control disease activity and reduce the risk of death or end-stage renal disease.