Search Results (6)

Determining carbon sources and sinks is crucial for understanding the global carbon cycle; however, the enigma of the ‘missing’ sinks remains unresolved. Recent studies have proposed carbonate weathering as a potential carbon sink, underscoring the need to clarify its mechanisms. Previous investigations of carbonate weathering largely relied on soil profiles, which were limited by the rarity of incipient weathering layers. Therefore, we have little knowledge about carbonate incipient weathering processes. To address this gap, spheroidal weathered dolostones were collected from Neoproterozoic Liangjiehe Formation (Nanhua System) in Guizhou, China. The pristine dolostone exhibits δ¹³C values ranging from −5.26 to −3.35‰ and δ¹⁸O values from −13.79 to −12.83‰. These isotopic signatures suggest that the dolostone formed under the high-latitude, cold climatic conditions that were prevalent during the Nanhua Period. Comprehensive petrographic and geochemical analyses of the spheroidal weathered dolostones revealed two distinct stages of incipient weathering. In Stage I, nickel (Ni) and cobalt (Co) contents decrease. The δ¹³C values fluctuate between −7.61 and −2.52‰, while the δ¹⁸O values range from −12.22 to −8.06‰. These observations indicate a weakly acidic microenvironment. In Stage II, there is an enrichment in manganese (Mn), with the δ¹³C values extending from −16.56 to −12.43‰ and the δ¹⁸O values from −8.46 to −7.03‰. These clues suggest a transition to a neutral microenvironment, with the isotopic compositions of carbon and oxygen in the dolomite influenced by atmospheric carbon dioxide (CO₂) and atmospheric precipitation. This study presents a pioneering investigation into the mineralogical and geochemical variations associated with carbonate incipient weathering processes. The variation in C-O isotopes during carbonate incipient weathering may indicate the re-precipitation of HCO₃⁻, suggesting that the carbon sink contribution of carbonate weathering to the global carbon cycle could be overestimated. Full article

Icing in cut slopes is a serious risk to transportation safety in cold regions. Research on the occurrence process and mechanism of icing is a prerequisite for proposing effective management measures. We took the cut slopes of the K162 section of the Beihei Highway as the research object. We used a combination of field investigation, geological exploration, monitoring, and simulation to study and analyze the power source, occurrence process, and triggering mechanism of icing in cut slopes. The results show that the geologic type of this cut slope is a mudstone–sandstone interaction stratum. Abundant shallow groundwater is the source of water for icing. The excavation of cut slopes extends the effect of negative temperatures on groundwater flow during the winter period. The process of ice formation in cut slopes can be described as follows: As the environmental temperature drops, the surface soil begins to freeze, resulting in a gradual narrowing of the water channel; then, the groundwater flow is blocked, so that the internal pressure begins to rise. When the internal pressure of the pressurized groundwater exceeds the strength of the frozen soil, groundwater overflows from the sandstone layer to the surface, forming icing. The high pore water pressure inside the cut slope is the precursor for the occurrence of icing. The dynamic pressure of the pore water pressure is the main driving force for the formation of icing in cut slopes. The obstruction of the water channel due to ground freezing is the triggering condition for ice formation in cut slopes. Full article

Due to the dual influence of climate change and human activities, the water cycle patterns in the lakesheds of the Yunnan karst plateau are undergoing significant changes, leading to increasingly prominent ecological issues. In the history of Lake Yangzong, an artificial water-diversion channel was excavated, altering the lake basin structure. Human activities have intensified, posing severe challenges to water resource supply and water security in recent decades. To investigate the significant increase in human activities, the temporal and phase changes, and the resulting transformation of the water and carbon cycles in the Lake Yangzong basin, we applied X-ray fluorescence spectroscopy (XRF) to scan elements continuously in a 10.2 m sediment core from this lake. By combining correlation analysis, principal component analysis (PCA), core chronology, and total organic carbon (TOC) content, we reconstructed the historical sequence of geochemical element contents in the Lake Yangzong catchment over the past 13,000 years. The results show that PC1 and PC2 contribute 78.4% and 10.3%, respectively, suggesting that erosion intensity is the main factor influencing the lake sedimentation process. From 13,400 to 680 cal a BP (calibrated years before the present), the sedimentation process in Lake Yangzong was mainly controlled by climatic conditions, with vegetation degradation during cold periods and relatively high erosion intensity in the watershed. During the Yuan dynasty, a province was established by the central government in Yunnan, promoting settlement and attracting a large number of immigrants from other provinces to Yunnan. Human activities in the Lake Yangzong basin began to intensify, surpassing natural changes and becoming the dominant force influencing the sedimentation process. In the Ming and Qing dynasties, the population and cultivated land area in Yunnan further increased, resulting in the significant exacerbation of erosion and soil loss in the watershed due to vegetation destruction. In the year 1388, the Tangchi Canal was excavated, transforming Lake Yangzong to an outflow lake, causing Ca²⁺ to be lost through the Tangchi Canal and preventing the formation of precipitation due to oversaturation. The research results indicate that human activities in the Lake Yangzong area have intensified since the Yuan dynasty, leading to increased erosion intensity. The excavation of the outflow canal transformed Lake Yangzong from an inland lake basin into an outflow state, simultaneously generating a significant transformation in the water and carbon cycling patterns in the watershed. Full article

The aim of this paper is to identify the trends of changes in atmospheric precipitation percolation under the changing climate conditions of Lithuania (the East Baltic region) based on long-term lysimeter studies. Data from 1987–2022 research (n = 1296) was used to determine trends in precipitation infiltration changes. Two 10-year periods, 1989–1998 and 2011–2020, were selected from the whole observation period (1987–2022) to assess changes in precipitation infiltration due to climate change. The air temperature has increased significantly in November (+3.4 °C) and December (+3.3 °C), with a +2.2 °C increase in the standard climate normal. The distribution of yearly precipitation has changed, with the annual amount decreasing from 686 to 652 mm. Precipitation increased the most in July and August (10.9 and 22.9 mm). In autumn, the amount of precipitation decreased by 7.9–31.1 mm. The number of rainy days did not change during the year, but the frequency of heavy precipitation increased significantly in August. The annual percolation increased by 14.2% over 2011–2020 compared to 1989–1998. Percolation increased by 19.0, 22.3, and 20.1% during the spring, autumn, and winter, respectively, and decreased by 35.0% in summer. The increase in annual percolation is mostly related to the increase in temperature during the cold season: November and December. During these months, the likelihood of early freeze formation, which interrupts gravitational water percolation in soil, is significantly reduced. In the spring, the increase in average air temperatures in March leads to faster melting of the winter snow in a shorter period, which significantly increases percolation processes. In Lithuania, higher percolation in autumn and winter, when part of the agricultural land is not covered by vegetation, may lead to higher leaching of chemical elements. Full article

The storage of wastes from mining and mineral processing plants in the tailing dumps in regions with cold climates has a number of environmental consequences. Interactions of water with tailings in cold climates often lead to the thawing of permafrost soils, formation of technogenic thawing zones, and leakage of drainage waters. In the case of fault zones development in these areas, technogenic solutions are often filtered outside the tailing dump, promoting further development of filtration channels. In order to prevent leakage of solution from tailing dumps over time, it is necessary to determine the thawing zones and prevent the formation of filtration channels. In the case of the formation of a filtration channel, it is necessary to know what rate of rock thawing occurred near the formed filtration channel. In this study, for the tailing dump of a diamond mining factory, we calculated two exothermic effects: (1) due to physical heating of dump rock by filtering industrial water with temperatures from 2 to 15 °C through the rock; and (2) due to the chemical interaction of industrial water with the dam base rock. The amount of energy transferred by the water to the frozen and thawed rock over 10 years was calculated using thermophysical modeling and was 207.8 GJ and 8.39 GJ respectively. The amount of energy that the rock received during the ten-year period due to dissolution of the limestones and equilibration of solutions was calculated using thermodynamic modeling and was 0.37 GJ, which is 4.4% of the average amount of energy, expended on heating the thawed rock (8.39 GJ). Full article

The time of Sartan glaciation in the Baikal–Yenisei Siberia, is comparable with that of MIS 2 and the deglaciation phase MIS 1. Loess loams, aeolian–colluvial sands and sandy loams represent subaerial sediments. There are four subhorizons (sr¹, sr², sr³ and sr⁴) in the Sartan horizon (sr). Sedimentary and soil-forming processes at different stratigraphic levels are considered. Differing soil formation types of cold periods are distinguished. Soils of the interstadial type with the A-C profile are represented only in the Early Sartan section of this paper. The soils of the pleniglacial type are discussed throughout the section. Their initial profile is O-C, TJ-C and W-C. Plant detritus remnants or poor thin humus horizons are preserved in places from the upper horizons. We propose for the first time for the interphasial soil formation type of cold stages to be distinguished. This is represented in the sections by the preserved BCm, BCg, Cm and Cg horizons of 15–20 cm thick. The upper horizons are absent in most sections. According to the surviving fragments, these were organogenous (O, TJ and T) and organomineral (AO and W) horizons. The sedimentation and soil formation features are considered from the perspective reconstruction of the Sartan natural and climatic conditions. Buried Sartan soils often contain cultural layers. Soil formation shows a well-defined periodicity of natural condition stabilization, which allowed ancient populations to adapt actively to various situations. Archaeologists’ interest in fossil soils is based on the ability of soils to “record” information about the natural and climatic conditions of human habitation. Full article