The impact of hydrothermal alteration on the physiochemical characteristics of reservoir rocks: the case of the Los Humeros geothermal field (Mexico)

Hydrothermal alteration is a common process in active geothermal systems and can significantly change the physiochemical properties of rocks. To improve reservoir assessment and modeling of high-temperature geothermal resources linked to active volcanic settings, a detailed understanding of the reservoir is needed. The Los Humeros Volcanic Complex, hosting the third largest exploited geothermal field in Mexico, represents a natural laboratory to investigate the impact of hydrothermal processes on the rock properties through andesitic reservoir cores and outcropping analogs. Complementary petrographic and chemical analyses were used to characterize the intensities and facies of hydrothermal alteration. The alteration varies from argillic and propylitic facies characterized by no significant changes of the REE budget indicating an inert behavior to silicic facies and skarn instead showing highly variable REE contents. Unaltered outcrop samples predominantly feature low matrix permeabilities ( 1.67 W m−1 K−1; > 0.91 10–6 m2 s−1), but a significant loss of magnetic susceptibility (10–3–10–6 SI). In particular, this latter characteristic appears to be a suitable indicator during geophysical survey for the identification of hydrothermalized domains and possible pathways for fluids. The lack of clear trends between alteration facies, alteration intensity, and chemical indices in the studied samples is interpreted as the response to multiple and/or repeated hydrothermal events. Finally, the proposed integrated field-based approach shows the capability to unravel the complexity of geothermal reservoir rocks in active volcanic settings

Asian and Saharan dust from a chemical/mineralogical point of view: differences and similarities from bulk and single particle measurements

This paper combines a review on the importance of dust composition with respect to numerous atmospheric impacts with field measurements performed in African and Central Asian dust. In the review part, the most important dust components and their relevance for certain processes are outlined. Typical compositions from bulk measurements for African and Asian dust are presented. Generally the local variation in composition can be higher than the differences between Asian and African dust and their according specific sources. While similar general results are available from individual particle analyses, these investigations add important information on mixing state and homogeneity of composition. Atmospheric aging of mineral dust is observed globally, depending on transport distances from the sources and transport environment. As an illustration, comparative field measurements of African and Asian dust deposition are presented

Supplementary information to 'Radiogenic heat production of crystalline rocks in the Gonghe Basin Complex (Northeastern Qinghai-Tibet plateau, China)'

The Gonghe Basin Complex (GBC), is a pull-apart basin located in the Northeastern Qinghai-Tibet plateau (Qinghai, China) displaying various geothermal features such as elevated geothermal gradients and hot springs, whose origin has not been conclusively determined so far. The adjacent mountain ranges and the basement are comprised of granitoidic rock, which, at sufficient depth and temperature, are suitable for deep enhanced geothermal systems. This study aims to investigate if the radiogenic heat production of these plutonic rocks is the heat source for the surface geothermal features. Therefore, 30 newly sampled Triassic, Silurian, Ordovician and Devonian intrusive rocks were extracted from outcrops in the surroundings and within the GBC, of which one sample was retrieved from exploration well DR2 at c. 1800 m. Samples were geochemically discriminated using the results of XRF measurements and radiogenic heat productions were subsequently calculated. Additionally, analysis of 341 intrusive, 105 extrusive, 155 sedimentary and 76 metamorphic rocks of the Qinling-Qilianshan-Kunlunshan were comprised from literature and compared to the data sampled in the GBC. As evidenced in the presented research, the radiogenic heat production measured in the GBC are within the highest calculated for the Qinling-Qilianshan-Kunlunshan. Although, radiogenic heat production rates in the GBC only range from 5 µW m^-3 in two-mica granites and syenogranites. Nonetheless, average heat productions analyzed do not evidence large intrusions of HHP (high heat producing) granitoids as source of the geothermal features in the GBC pull-apart basin

Impacts of low emission zones in Germany on air pollution levels

Since 2008 low emission zones (LEZ) have been introduced in many German cities to improve air quality and to protect human health. In order to assess the effectiveness of LEZ, both descriptive and statistical analyses have been conducted based on concentrations of air pollutants (PM10, PM2.5, NO, NO2, and NOx) from relevant monitoring stations in Germany from year 2002 to 2012. The results indicate that the introduction of LEZ has brought positive effects on reducing air pollutant concentrations. But the potential of further reduction by additional LEZ in Germany without further development of this measure seems to be small

Analyse der Wirksamkeit von Umweltzonen hinsichtlich Feinstaub- und Stickstoffoxidkonzentrationen

In vielen deutschen Staedten wurden seit dem Jahr 2008 Umweltzonen als Massnahme des Verkehrsmanagements zur Verbesserung der Luftqualitaet und zum Schutz der Gesundheit der Bevoelkerung eingefuehrt. Der Beitrag analysiert die Effektivitaet von Umweltzonen anhand von statistischen Untersuchungen von Daten zur Schadstoffkonzentration von Luftmessstationen in Deutschland aus den Jahren 2002 bis 2012. Die Ergebnisse zeigen, dass die PM10-Konzentration an Stationen in Umweltzonen um durchschnittlich circa 2 Microgramm pro Kubikmeter staerker zurueckgegangen ist als an vergleichbaren Stationen ausserhalb von Umweltzonen. Die Anzahl an Tagen mit Grenzwertueberschreitungen ging gegenueber vergleichbaren Stationen ausserhalb von Umweltzonen um im Mittel neun zusaetzliche Tage zurueck. Leicht positive Effekte der Umweltzonen auf einem niedrigeren Signifikanzniveau konnten ebenfalls fuer die Stickoxidkonzentrationen beobachtet werden. Aussagen zur Wirkung auf die PM2,5-Konzentration konnten wegen Mangel an Daten nicht getroffen werden. Es kann festgestellt werden, dass die Einfuehrung von Umweltzonen sich positiv auf die Luftqualitaet ausgewirkt hat, insbesondere durch die Veraenderungen in der Fahrzeugflotte gilt dies auch fuer Bereiche ohne Umweltzone. Das Verbesserungspotenzial fuer weitere Umweltzonen ohne Weiterentwicklung dieser Massnahme erscheint jedoch gering