Exceedance of air quality standards resulting from pyro-metallurgical production of copper: a case study, Bor (Eastern Serbia)

This study represents air quality data of SO₂ and As concentrations around the mining–metallurgical complex Bor (Serbia) from 1994 to 2008. Daily and annual SO₂ concentrations greatly exceed current air quality standards in the studied area. The “hot spot” with the highest SO₂ and As annual concentrations during 15 years was the urban-industrial area (the town core). Daily SO₂ concentrations and meteorological parameters during the period from 2005 to 2008 were statistically analysed to develop suitable prediction equations for daily SO₂ concentrations. Anode copper production is an important but not the only factor that has influence on SO₂ concentrations. By stepwise multiple linear regression analysis, it was determined that daily SO₂ concentrations are most influenced by maximum wind gust, relative humidity and air temperature at all the measuring sites. The prediction equations of daily SO₂ concentrations represent a good model with regression coefficients from 0.854 to 0.926 at all the measuring sites. Correlation analysis showed that eastern and western winds increase SO₂ concentrations, thus increasing the health risk of the inhabitants in the study area.     

Aram Chaos and its constraints on the surface heat flux of Mars

The surface heat flux of a planet is an important parameter to characterize its internal activity and to determine its thermal evolution. Here we report on a new method to constrain the surface heat flux of Mars during the Hesperian. For this, we explore the consequences for the martian surface heat flux from a recently presented new hypothesis for the formation of Aram Chaos (Zegers, T.E., Oosthoek, J.H.P., Rossi, A.P., Blom, J.K., Schumacher, S. [2010]. Earth Planet. Sci. Lett. 297, 496-504. doi:10.1016/j.epsl.2010.06.049.). In this hypothesis the chaotic terrain is thought to have formed by melting of a buried ice sheet. The slow sedimentation and burial of the ice sheet led to an increased thermal insulation of the ice and subsequently to a temperature increase high enough to trigger melting and the formation of the subsurface lake. As these processes highly depend on the thermal properties of the subsurface and especially on the surface heat flux, it is possible to constrain the latter by using numerical simulations. Based on the hypothesis for the formation of Aram Chaos, we conducted an extensive parameter study to determine the parameter settings leading to sufficient melting of the buried ice sheet. We find that the surface heat flux in the Aram Chaos region during the Hesperian was most likely between 20 and 45 mW m⁻² with a possible maximum value of up to 60 mW m⁻².     

Formation of pseudotachylitic breccias in the central uplifts of very large impact structures: Scaling the melt formation

Abstract– The processes leading to formation of sometimes massive occurrences of pseudotachylitic breccia (PTB) in impact structures have been strongly debated for decades. Variably an origin of these pseudotachylite (friction melt)‐like breccias by (1) shearing (friction melting); (2) so‐called shock compression melting (with or without a shear component) immediately after shock propagation through the target; (3) decompression melting related to rapid uplift of crustal material due to central uplift formation; (4) combinations of these processes; or (5) intrusion of allochthonous impact melt from a coherent melt body has been advocated. Our investigations of these enigmatic breccias involve detailed multidisciplinary analysis of millimeter‐ to meter‐sized occurrences from the type location, the Vredefort Dome. This complex Archean to early Proterozoic terrane constitutes the central uplift of the originally >250 km diameter Vredefort impact structure in South Africa. Previously, results of microstructural and microchemical investigations have indicated that formation of very small veinlets involved local melting, likely during the early shock compression phase. However, for larger veins and networks it was so far not possible to isolate a specific melt‐forming mechanism. Macroscopic to microscopic evidence for friction melting is very limited, and so far chemical results have not directly supported PTB generation by intrusion of impact melt. On the other hand, evidence for filling of dilational sites with melt is abundant. Herein, we present a new approach to the mysterium of PTB formation based on volumetric melt breccia calculations. The foundation for this is the detailed analysis of a 1.5 × 3 × 0.04 m polished granite slab from a dimension‐stone quarry in the core of the Vredefort Dome. This slab contains a 37.5 dm³ breccia zone. The pure melt volume in 0.1 m³ PTB‐bearing granitic target rock outside of the several‐decimeter‐wide breccia zone in the granite slab was estimated at 5.2 dm³. This amount can be divided into 4.6 dm³ melt (88%), for which we have evidenced a limited material transport (at maximum, ≈20 cm) and 0.6 dm³ melt (12%) with, at most, grain‐scale material transport, which we consider in situ formed shock melt. The breccia zone itself contains about 10 dm³ of matrix (melt). Assuming melt exchange over 20 cm at the slab surface, between breccia zone and surrounding melt‐bearing host rock volume, the outer melt volume is calculated to contain the same amount of melt as contained by the massive breccia zone. Meso‐ and microscopic observations indicate melt transport is more prominent from larger into smaller melt occurrences. Thus, melt of the breccia zone could have provided the melt fill for all the small‐scale PTB veins in the surrounding target rock. Extrapolating this melt capacity calculation for 1 m³ PTB‐bearing host rock shows that a host rock volume of this dimension is able to take up some 52 dm³ melt. Scaling up 1000‐fold to the outcrop scale reveals that exchange between a host rock volume of 2 m radius around a 37 m³ breccia zone could involve some 10 m³ melt. These results demonstrate that large melt volumes (i.e., large breccia zones) can be derived, in principle, from local reservoirs. However, strong decompression would have to apply in order to exchange these considerable melt volumes, which would only be realistic during the decompression phase of impact cratering upon central uplift formation, or locally where compressive regimes acted during the subsequent down‐ and outward collapse of the central uplift.     

Seismo-acoustic signals associated with degassing explosions recorded at Shishaldin Volcano,Alaska, 2003–2004

In summer 2003, a Chaparral Model 2 microphone was deployed at Shishaldin Volcano, Aleutian Islands, Alaska. The pressure sensor was co-located with a short-period seismometer on the volcano’s north flank at a distance of 6.62 km from the active summit vent. The seismo-acoustic data exhibit a correlation between impulsive acoustic signals (1–2 Pa) and long-period (LP, 1–2 Hz) earthquakes. Since it last erupted in 1999, Shishaldin has been characterized by sustained seismicity consisting of many hundreds to two thousand LP events per day. The activity is accompanied by up to ∼200 m high discrete gas puffs exiting the small summit vent, but no significant eruptive activity has been confirmed. The acoustic waveforms possess similarity throughout the data set (July 2003–November 2004) indicating a repetitive source mechanism. The simplicity of the acoustic waveforms, the impulsive onsets with relatively short (∼10–20 s) gradually decaying codas and the waveform similarities suggest that the acoustic pulses are generated at the fluid–air interface within an open-vent system. SO₂ measurements have revealed a low SO₂ flux, suggesting a hydrothermal system with magmatic gases leaking through. This hypothesis is supported by the steady-state nature of Shishaldin’s volcanic system since 1999. Time delays between the seismic LP and infrasound onsets were acquired from a representative day of seismo-acoustic data. A simple model was used to estimate source depths. The short seismo-acoustic delay times have revealed that the seismic and acoustic sources are co-located at a depth of 240±200 m below the crater rim. This shallow depth is confirmed by resonance of the upper portion of the open conduit, which produces standing waves with f=0.3 Hz in the acoustic waveform codas. The infrasound data has allowed us to relate Shishaldin’s LP earthquakes to degassing explosions, created by gas volume ruptures from a fluid–air interface.     

Biomass estimation using Landsat-TM and -ETM+. Towards a regional model for Southern Africa?

Grazing and fire are major factors influencing the savanna ecosystems of Southern Africa. In both grazing and conservation areas overgrazing is an important reason for degradation of vegetation and soil. Insufficient fire management can cause a change in the species composition and may influence the soil negatively. For adequate planning purposes the knowledge of available biomass is indispensable. High-resolution satellite systems can provide such knowledge on a large scale. Three study areas in Southern Africa contributed to a first survey. Gutu District is situated in Zimbabwe. In its Communal Lands a high population density leads to severe degradation of vegetation and soil. The South African test sites are located in Kruger National Park and Madikwe Game Reserve. Therefore a wide ecological range from highly degraded to slightly disturbed savanna ecosystems is included. Satellite images of both Landsat-5 (TM) and Landsat-7 (ETM+) were applied. After cross-calibration of the two different satellite systems, indices applied to radiance and reflectance showed significant correlations with ground truth data of grass and other foliage biomass. Including new data from Hluhluwe National Park (South Africa) into the regression models improved the results, indicating that a regional model for savanna ecosystems in Southern Africa could be found. This revised version was published online in August 2006 with corrections to the Cover Date.     

Impact of grout curtains on karst groundwater behaviour: an example from the Dinaric karst

Grout curtains are vertical grout walls installed in the ground. In karst terrains, their construction is primarily connected with dams and reservoirs. Their main role is to increase water tightness and to prevent progressive erosion, blocking possible seepage paths along karst fissures and conduits. In this article, changes in the behaviour of the groundwater level (GWL) and the water temperature in nine deep piezometers, which were caused by the construction of a grout curtain at the ?ale Reservoir on the Cetina River (Croatia), were analysed. The total length of the grout curtain is 3966 m. It spreads 120 m below the dam. The most analysed data are from the period after the dam had been built. Only few data and figures concern the comparison between pre‐ and post‐dam periods. The hourly data of the GWL and the water temperature were analysed for the period between 1 September 2008 at 02:00 h to 31 December 2009 at 23:00 h (11 687 h total) in six deep piezometers (marked in the text and figures as 1, 2, 3, 4, 5 and 6). For three piezometers (marked in the text and figures as A, B and C), some discontinuous measurements of the GWL and the water temperature were available for analysis. The construction of the grout curtain made strong, sudden and possibly dangerous changes to the characteristics of the aquifer and the circulation of groundwater in the local area. Special attention is paid to analyses of the behaviour of the hourly GWL data measured in the piezometers pairs (two neighbouring piezometers, one inside and the other outside of the grout curtain). During more than 80% of the analysed period, the GWL was higher in the piezometer inside the grout curtain than the one outside of it. The intensity and range of the dynamics of GWL was higher in piezometer outside the grout curtain than the inside ones. After the construction of the grout curtain, the maximum measured hydrostatic pressure on some parts of the grout curtain was approximately 40 m. It changes quickly in both time and direction. The water temperature was found to be similar in all of the measured piezometers, and it varies between 10.2 and 15.7 °C with an average value of 12.7 °C. Copyright © 2011 John Wiley & Sons, Ltd.     

Influences of forest canopy on snowpack accumulation and isotope ratios

The stable water isotopes, ²H and ¹⁸O, can be useful environmental tracers for quantifying snow contributions to streams and aquifers, but characterizing the isotopic signatures of bulk snowpacks is challenging because they can be highly variable across the catchment landscape. In this study, we investigate one major source of isotopic heterogeneity in snowpacks: the influence of canopy cover. We measured amounts and isotopic compositions of bulk snowpack, throughfall, and open precipitation during seven campaigns in mid-winter 2018 along forest-grassland transects at three different elevations (1196, 1297, and 1434 m above sea level) in a pre-Alpine catchment in Switzerland. Snowpack storages under forest canopies were 67 to 93% less than in adjacent open grasslands. On average, the water isotope ratios were higher in the snowpacks under forest canopy than in open grasslands (by 13.4 ‰ in δ²H and 2.3 ‰ in δ¹⁸O). This isotopic difference mirrored the higher isotope values in throughfall compared with open snowfall (by 13.5 ‰ in δ²H and 2.2 ‰ in δ¹⁸O). Although this may suggest that most of the isotopic differences in snowpacks under forests versus in open grasslands were attributable to canopy interception effects, the temporal evolution of snowpack isotope ratios indicated preferential effluxes of lighter isotopes as energy inputs increased and the snowpack ripened and melted. Understanding these effects of forest canopy on bulk snowpack snow water equivalent and isotopic composition are useful when using isotopes to infer snowmelt processes in landscapes with varying forest cover.     

Intercomparison of Two Box Models of the Chemical Evolution in Biomass-Burning Smoke Plumes

Results from two independently developed biomass-burning smoke plume models are compared. Model results were obtained for the temporal evolution of two nascent smoke plumes originating from significantly different fire environments (an Alaskan boreal forest and an African savanna). The two smoke plume models differed by 1%–10% for [O₃], with similar differences for NO _x and formaldehyde (relative percent differences). Smaller intermodel differences were observed for the African savanna smoke plume as compared to the plume from the Alaskan boreal fire. Mechanistic differences between the models are heightened for the Alaskan smoke plume due to the higher VOC emission ratios as compared to the African savanna fire. The largest deviations result from the differences in oxidative photochemical mechanisms, with a smaller contribution attributable to the calculation of photolysis frequencies. The differences between the two smoke plume models are significantly smaller than the uncertainties of available photokinetic data or field measurements. Model accuracy depends most significantly on having the fullest possible VOC data, a requirement that is constrained by currently available instrumentation.