Acumulación de Ag, Cu y Ni en sedimentos en una cuenca semiárida como sub-producto de la mina de oro El Triunfo, Baja California Sur, México

The dispersal of Ag, Cu, and Ni in mine wastes (tailings and ash) was studied from the source of an abandoned gold mine at El Triunfo (Baja California Sur, Mexico) to the adjacent coast of the Pacific Ocean. The highest contamination levels of the studied elements were measured in one sample of the tailings (Ag: 247 mg kg-1; Cu: 1660 mg kg-1; Ni: 111 mg kg-1). Horizontal and vertical distributions of these elements were obtained from the analysis of surface sediments, tailings, a test pit, a sediment core, and dunes. The background levels of these elements were estimated from independent methods. Then, these regional background level calculations were used to determine the normalised enrichment factors (NEFs). Relatively high NEF values (averages of Ag, Cu, and Ni were 24.0, 3.0, and 1.4, respectively) indicated that the area close to the mine waste zone (up to about 18 km from the source area) was moderately to severely polluted. Moderate to null pollution (average NEFs of Ag, Cu, and Ni were 7, 2 and 1, respectively) was interpreted for the area at about 18-49 km from the mine waste zone. Vertical distributions of the elements in sediments of the overbank, the test pit in the mine zone, and the sediment core (at the discharge of the main arroyo Hondo–Las Gallinas–El Carrizal), also revealed enrichment of Ag, Cu, and Ni relative to the surface sediments. This study indicated that historic and contemporary contamination continues to impact the fluvial environment.Se estudió la dispersión de Ag, Cu, y Ni, en desechos mineros (jales y cenizas) desde su origen en la mina de oro abandonada de El Triunfo (Baja California Sur, México) hasta su desembocadura en la costa adyacente al Océano Pacífico. Los mayores niveles de la contaminación de los elementos estudiados se presentan en los jales (Ag: 247 mg kg-1; Cu: 1660 mg kg-1; Ni: 111 mg kg-1). Se obtuvieron distribuciones horizontales y verticales de estos elementos a partir de los análisis de sedimentos superficiales, de deterun jale, de un pozo de ensayo, de un testigo y en las dunas adyacentes a la desembocadura del arroyo. Los niveles de fondo fueron calculados considerando varios métodos independientes. Luego, con estos cálculos de niveles de fondo se determinaron los Factores de Enriquecimiento Normalizados (NEFs). Los valores relativamente altos de NEF (promedios de Ag, Cu and Ni de 24.0, 3.0 y 1.4, respectivamente) indicaron que el área situada cerca de la zona minera (aproximadamente 18 km de los desechos mineros abandonados) se encuentra de moderada a severamente contaminada. Una contaminación moderada a nula (NEFs promedio de Ag, Cu y Ni: 7, 2 y 1, respectivamente) fue determinada en el área comprendida entre los 18 y los 49 km medidos desde el distrito minero. Las distribuciones verticales de los elementos en los sedimentos de los jales y el pozo de ensayo en la zona minera, así como en el testigo analizado en la desembocadura del arroyo principal (Arroyo Hondo – Las Gallinas – El Carrizal), muestran mayor enriquecimiento de Ag, Cu y Ni, que los sedimentos superficiales adyacentes. Este estudio indica que la contaminación histórica y contemporánea está impactando el ambiente fluvial

Estimation of Admission D-dimer Cut-off Value to Predict Venous Thrombotic Events in Hospitalized COVID-19 Patients: Analysis of the SEMI-COVID-19 Registry

Background: Venous thrombotic events (VTE) are frequent in COVID-19, and elevated plasma D-dimer (pDd) and dyspnea are common in both entities. Objective: To determine the admission pDd cut-off value associated with in-hospital VTE in patients with COVID-19. Methods: Multicenter, retrospective study analyzing the at-admission pDd cut-off value to predict VTE and anticoagulation intensity along hospitalization due to COVID-19. Results: Among 9386 patients, 2.2% had VTE: 1.6% pulmonary embolism (PE), 0.4% deep vein thrombosis (DVT), and 0.2% both. Those with VTE had a higher prevalence of tachypnea (42.9% vs. 31.1%; p = 0.0005), basal O2 saturation <93% (45.4% vs. 33.1%; p = 0.0003), higher at admission pDd (median [IQR]: 1.4 [0.6–5.5] vs. 0.6 [0.4–1.2] µg/ml; p < 0.0001) and platelet count (median [IQR]: 208 [158–289] vs. 189 [148–245] platelets × 109/L; p = 0.0013). A pDd cut-off of 1.1 µg/ml showed specificity 72%, sensitivity 49%, positive predictive value (PPV) 4%, and negative predictive value (NPV) 99% for in-hospital VTE. A cut-off value of 4.7 µg/ml showed specificity of 95%, sensitivity of 27%, PPV of 9%, and NPV of 98%. Overall mortality was proportional to pDd value, with the lowest incidence for each pDd category depending on anticoagulation intensity: 26.3% for those with pDd >1.0 µg/ml treated with prophylactic dose (p < 0.0001), 28.8% for pDd for patients with pDd >2.0 µg/ml treated with intermediate dose (p = 0.0001), and 31.3% for those with pDd >3.0 µg/ml and full anticoagulation (p = 0.0183). Conclusions: In hospitalized patients with COVID-19, a pDd value greater than 3.0 µg/ml can be considered to screen VTE and to consider full-dose anticoagulation. © 2021, Society of General Internal Medicine