Low-Calcium Cave Dripwaters in a High CO2 Environment: Formation and Development of Corrosion Cups in Postojna Cave, Slovenia

Speleothems have proven to be one of the most reliable terrestrial archives for palaeoclimate research. However, due to the complexity of karst systems, long-term monitoring and high-resolution analyses of the cave atmosphere and water geochemistry have become essential to better constrain the factors that control calcite growth and how geochemical palaeoclimate proxies are encoded into speleothems. While calcite precipitation incorporates the palaeoclimate signals into the speleothem fabric, certain conditions in caves can favour dissolution, which may form hiatuses or even destroy these signals. In extreme cases, in-cave dissolution by dripwater can form cup-shaped features (i.e., corrosion cups), which were the main focus of this study. The study site in Postojna Cave, Slovenia was investigated through cave climate monitoring and drip and cup water sampling, which took place during 2017–2021. We found that the cups are fed by low-calcium drips as the consequence of the thin rock overburden above the cave. Due to the specific configuration of the airflow pathways, the study site accumulates high levels of CO2 (>10,000 ppm), which shifts low-calcium dripwater into undersaturation. This causes dissolution on the rock surfaces and speleothems on the cave floor. The results of this study have broader significance in addressing the suitability of cave environments and speleothems used in paleoclimate research.

Clonal variation in coppiced and uncoppiced growth, root-sprout stem formation, and biomass partitioning in Salix interior on two highly disturbed site types

Salix interior Rowlee (INT), a wide-ranging North American willow from the small taxonomic group Salix sect. Longifoliae, is notable for its ability to form multi-stemmed vegetative stem colonies arising via root sprouts (RS) from a shallow horizontal root network. This study quantifies biomass production for both 1-yr-old coppiced plants and the original 4-yr-old plants, as well as for the RS stems associated with each ortet (original mother plant) using eight selected genotypes established on two distinct site types. Significantly greater coppiced and uncoppiced ortet stem dry mass was recorded on the coarse-textured, shale rock overburden (SO); possibly due to significantly greater fertility, compared to adjacent gravel outwash deposits (GD), which had greater RS stem mass. Significant clonal differences, as well as site type × clone interactions, were found for ortet stem dry mass, especially on SO sites, When expressed as a fraction of total stem dry mass produced on 2 m × 2 m biomass plots, the RS component represented a significant 57% of total stem dry mass per plot on GD sites. The use of colony-forming willows such as INT minimizes the need for periodic replanting, providing a cost advantage over conventional short-rotation, coppice-based woody biomass plantations using species that do not have the ability to reproduce via root sprouting.

The global iron industry and the Anthropocene

Iron ore is the most mined metal and the second most mined mineral in the world. The mining of iron ore and the processing of iron and steel increased sharply during the 20th century and peaked at the beginning of the 21st century. Associated processes along the iron ore cycle (mining, processing, recycling, weathering) such as the massive displacement of rock, the emission of waste and pollutants, or the weathering of products resulted in long-term environmental and stratigraphic changes. Key findings link the iron ore industry to 170 gigatons of rock overburden, a global share of CO2 with 7.6%, mercury with 7.4%, and a variety of other metals, pollutants, and residues. These global changes led to physical, chemical, biological, magnetic, and sequential markers, which are used for the justification of the Anthropocene. The potential markers vary significantly regarding their persistence and measurability, but key findings are summarised as TMPs (Technogenic Magnetic Particles), SCPs (Spheroidal Carbonaceous fly ash Particles), POPs (Persistent Organic Particles), heavy metals (vanadium, mercury, etc.), as well as steel input and steel corrosion residues.

Comparing seepage and selenium desorption in blasted-rock fills using two reclamation techniques

Geomorphic reclaimed landforms aim to improve groundwater movement and diminish contaminant transport through increased runoff and reduced groundwater infiltration. The objective of this research was to determine if geomorphic reclamation techniques result in improved selenium concentrations of discharge water as compared to conventional reclamation for valley-fills constructed of blasted rock. Comparisons investigated if groundwater and contaminant desorption could be improved by altering valley-fill construction. Three-dimensional finite-element groundwater modelling was performed on two valley-fill geometries and was coupled with laboratory testing of selenium leaching from blasted-rock overburden. Selenium desorption characteristics and distributions were compared. Lower water volumes and shorter contact times with overburden fill resulted in lower masses of selenium desorbed from geomorphic fills as compared to conventional techniques. When results were normalized by varying fill areas and volumes, the geomorphic valley-fill exhibited 23% lower surface infiltration, 27% lower discharge volumes and 39% lower selenium discharge loads as compared to the conventional reclamation. To achieve these advantages in geomorphic reclamation, infiltration must be reduced through both the construction of curvilinear slopes of the fill surface and the creation of a low infiltration-capacity reclaimed stream.

Optimization of the Excavator-and-Dump Truck Complex at Open Pit Mines – the Case Study

The transition to the use of the new equipment requires a revision of previously established dependencies, which constitute the methodological basis for optimization to ensure the highly efficientoperation of technological equipment of the excavator-and-dump truckcomplex that performs all technological processes of overburden. The imperfection of the existing methods of optimization is due to the use, as a rule, of empirical formulas for the obsolete equipment installed to calculatethe performance, so replacing or partially adjusting these dependencies, including methods and tools for determining process parameters, is anurgent task. Therefore, it is important to establish the parameters of each ofthe conjugate technological processes for the development of hard rock and half-rock overburden, which together provide the optimal results of the entire excavator-and-dump truck complex. The article considers the use of excavator-and-dump truck complex optimization as a criterion for the average weighted size of pieces of exploded rock mass, which allows determining the optimal parameters of each of the associated technological processes, their costs, as well as the total costs of the technology as a whole.

UNDERGROUND MUON ENERGY SPECTRA WITH THE MACRO TRD

The MACRO detector was located in the Hall B of the Gran Sasso underground Laboratories under an average rock overburden of 3700 hg/cm2. A TRD composed by three identical modules, covering an horizontal area of 36 m2, was added to the MACRO detector in order to measure the residual energy of muons entering MACRO. This kind of measurement provides a useful tool to study the primary cosmic ray energy spectra and composition, their interactions with the Earth's atmosphere and the propagation of muons inside the rock. The results of the measurement of the energy of single and double muons crossing MACRO will be presented. Our data show that double muons are more energetic than single ones in the rock depth range from 3000 to 6500 hg/cm2. Single muon data confirm the reliability of the models adopted to describe the cosmic ray interactions with the atmosphere and the muon propagation inside the rock.

Construction of a tunnel under thin rock overburden in Middle Marsyangdi Hydroelectric Project, Central Nepal

This paper deals with an application of New Australian Tunnelling Method (NATM) in low cover tunnelling in Lesser Himalaya of Nepal. The length of the tunnel is 365.8 m with a 8.2 m finished diameter. The average thickness of the rock overburden is 16- 18 m with a maximum of 30 m, whereas average side cover is 40 m. Top heading and multiple benching methods were applied for tunnelling work. The rational support design techniques were conceived together with Bieniawski's Support Guideline for each standard support classes. Standard initial support system was designed according to NATM, to provide complete stabilization of excavation. It consisted of a combination of systematic rock bolts and shotcrete. The smooth blasting technique was adopted for the tunnel excavation. The specific charge was 1.39-1.47 kg/m3 A special emphasis was given in the collection of discontinuity data so that the rock mass could be evaluated effectively. Geomechanics classification for rock mass was used for the rock mass evaluation. The rock mass was also back evaluated by using Q and GSI classification on the basis of installed support. After the careful assessment of the data, the rock mass in the tunnel was classified into fair to poor according to RMR and Q and blocky / disturbed to very blocky / fair according to GSI. The rock mass parameters collected during the construction stage agree with the data collected at surface during feasibility and tendering stages. The rock mass classification based on the surface outcrop survey and drillings was a considerable success and found to be very close to the actual condition. The effectiveness of revised support system with steel rib was found to be negligible or minimum for tunnel support. Rock support deformation monitoring in the tunnel was regularly carried out to determine the efficiency and adequacy of the installed support.

Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry

Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus™ has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.