Infrasound detection of approaching lahars

Infrasound may be used to detect the approach of hazardous volcanic mudflows, known as lahars, tens of minutes before their flow fronts arrive. We have analyzed signals from more than 20 secondary lahars caused by precipitation events at Fuego Volcano during Guatemala's rainy season in May through October of 2022. We are able to quantify the capabilities of infrasound monitoring through comparison with seismic data, time lapse camera imagery, and high-resolution video of a well-recorded event on August 17. We determine that infrasound sensors, deployed adjacent to the lahar path and in small-aperture (10 s of meters) arrays, are particularly sensitive to remote detection of lahars, including small-sized events, at distances of at least 5 km. At Fuego Volcano these detections could be used to provide timely alerts of up to 30 min before lahars arrive at a downstream monitoring site, such as in the frequently impacted Ceniza drainage. We propose that continuous infrasound monitoring, from locations adjacent to a drainage, may complement seismic monitoring and serve as a valuable tool to help identify approaching hazards. On the other hand, infrasound arrays located a kilometer or more from the lahar path can be effectively used to track a lahar's progression.

[Physical and chemical characterization of industrial nixtamalized corn flour for human consumption in Central America]

The objective of this study was the characterization of industrial nixtamalized maize flour for human consumption and which are marketed in Central America for some selected physical and chemical properties which may contribute to food composition information and help nutrition and micronutrient fortification programs. A total of 12 brands purchased in triplicate were obtained from supermarkets in Guatemala, El Salvador and Honduras. These samples were kept under refrigeration until analyzed. The physical parameters measured and results were the following: particle size with most samples having a high percentage of particles greater than 60 mesh, pH (5.4-7.5), water absorption index (WAI) (3.4-4.0 g gel/g sample), water soluble index (WSI) (4.8-7.8 g/100 g) and flour density (0.410-0.547 g/ml). The differences were statistically significant for all parameters measured, except for WAI. The chemical characteristics included, moisture, protein, fat, ash and dietetic fiber. Differences between flour samples were statistically significant except for fat content. Protein content was low, ranging between 6.7-8.1 g/100 g and total dietary fiber varied between 7.7-12.0 g/100 g. The samples were analyzed for phytic acid with a variation from 632 to 903 mg/100 g, with statistical significant differences. The samples were also analyzed for total and soluble (pH 7.5) iron, phosphorus, calcium, potassium, zinc, copper, manganese, and magnesium. The difference in the iron and calcium content between flour samples were statistically significant. The physical and chemical variability found between flour samples of nixtamalized maize was relatively high and it is recommended to establish quality standards through raw material and process standardization for greater effectiveness of nutrition programs and activities on micronutrient fortification which may be pursued in the future.