Chronic kidney disease (CKD) is a global public health problem, and cardiovascular disease is the most common cause of death in patients with CKD. The incidence and prevalence of cardiovascular events during the early stages of CKD increases significantly with a decline in renal function. More than 50% of dialysis patients die from cardiovascular disease, including coronary heart disease, heart failure, arrhythmia, and sudden cardiac death. Therefore, developing effective methods to control risk factors and improve prognosis is the primary focus during the diagnosis and treatment of CKD. For example, the SPRINT study demonstrated that CKD drugs are effective in reducing cardiovascular and cerebrovascular events by controlling blood pressure. Uncontrolled blood pressure not only increases the risk of these events but also accelerates the progression of CKD. A co-crystal complex of sacubitril, which is a neprilysin inhibitor, and valsartan, which is an angiotensin receptor blockade, has the potential to be widely used against CKD. Sacubitril inhibits neprilysin, which further reduces the degradation of natriuretic peptides and enhances the beneficial effects of the natriuretic peptide system. In contrast, valsartan alone can block the angiotensin II-1 (AT1) receptor and therefore inhibit the renin–angiotensin–aldosterone system. These two components can act synergistically to relax blood vessels, prevent and reverse cardiovascular remodeling, and promote natriuresis. Recent studies have repeatedly confirmed that the first and so far the only angiotensin receptor–neprilysin inhibitor (ARNI) sacubitril/valsartan can reduce blood pressure more effectively than renin–angiotensin system inhibitors and improve the prognosis of heart failure in patients with CKD. Here, we propose clinical recommendations based on an expert consensus to guide ARNI-based therapeutics and reduce the occurrence of cardiovascular events in patients with CKD.
In the context of climate change, the input of acid substances into rivers, caused by human activities in the process of industrial and agricultural development, has significantly disrupted river systems and has had a profound impact on the carbon cycle. The hydrochemical composition and which main sources of the Lianjiang River (LR), a subtropical karst river in northern Guangdong Province, South China, were analyzed in January 2018. The objective was to explicate the influence on the deficit proportion of CO2 consumption, resulting from carbonate chemical weathering (CCW), driven by nitric acid (HNO3) and sulfuric acid (H2SO4), which is affected by exogenous acids from the industrial regions in north of the Nanling Mountains and the Pearl River Delta. The response of the riverine carbonate system to exogenous acid-related weathering was also discussed. HCO3− and Ca2+, respectively, accounted for 84.97% of the total anions and 78.71% of the total cations in the surface runoff of the LR, which was characterized as typical karst water. CCW was the most important material source of river dissolved loads in the LR, followed by human activities and silicate chemical weathering (SCW). Dissolved inorganic carbon (DIC), derived from CCW induced by carbonic acid (H2CO3), had the largest contribution to the total amount of DIC in the LR (76.79%), and those from CCW induced by anthropogenic acids (HNO3 and H2SO4) and SCW contributed 13.56% and 9.64% to the total DIC, respectively. The deficit proportion of CO2 consumption associated with CCW resulting from sulfuric acid and nitric acid (13.56%), was slightly lower than that of the Guizhou Plateau in rainy and pre-rainy seasons (15.67% and 14.17%, respectively). The deficit percentage of CO2 uptake associated with CCW induced by sulfuric acid and nitric acid, accounted for 38.44% of the total CO2 consumption related to natural CCW and 18.84% of the anthropogenic acids from external areas. DIC derived from CCW induced by human activities, had a significant positive correlation with the total alkalinity, SIc and pCO2 in river water, indicating that the carbonate system of the LR was also driven by exogenous acids, with the exception of carbonic acid. More attention should be paid to the effects of human activities on the chemical weathering and riverine carbonate system in the karst drainage basin.
Epikarst is connected with a “binary” geological structure, and the hydrogeochemical processes are complex. Nutrients play an important role in the restoration of the surface ecosystem in the desertification area, which is prone to loss and leakage, and the transport and transformation of nitrogen is crucial to the growth and development of plants in the ecosystem and the safety of drinking water for the residents. In this study, we reviewed nitrogen research in the past 20 years in the “Web of Science (WOS)” and “China National Knowledge Infrastructure (CNKI)”, and we reviewed nitrogen research in the following areas. From the results of the systematic review, (1) We found that nitrogen-related research literature has been growing over time, and the growth has been faster in the past five years, mainly in the fields of agriculture, public health, and environmental science; (2) In karst water systems, researchers are mostly concerned with the sources of nitrate, distribution characteristics, and pollution of karst water, and the dual isotope techniques of δ15N and δ18O are used to identify these; (3) In karst water systems, surface water bodies and underground rivers are the main objects of study, relatively few studies have been conducted on karst springs, and NO3−-N, NO2−-N, and NH4+-N are the main forms of nitrogen presence. The study of nitrogen in karst water systems ignores the unique subsurface leakage problem of karst areas, and the study of the relationship between nitrogen and nutrient leakage in karst water systems should be strengthened for karst desertification management and ecological restoration. This review may provide some insights for researchers working in related fields.
Groups in dissolved organic matter (DOM) emit fluorescence information at characteristic wavelengths when irradiated by excitation waves, which can reveal the geochemical behavior of dissolved organic matter in the environment and its sources, but there are few relevant studies in cave groundwater systems. In order to investigate the relationship between drip hydrochemistry characteristics and DOM in cave systems after subsurface leakage, in this study, from the perspective of dissolved organic matter in the karst cave water system, the groundwater in the dry season of Daxiao Cave was selected as the research object. Five drip points and one water pool (DX-1, DX-2, DX-3, DX-4, DX-5, and DX-C) in Daxiao Cave were monitored and consecutively sampled for four months. The parallel factor analysis method (PARAFAC), three-dimensional (3D) fluorescence parameters, and excitation-emission matrix fluorescence spectroscopy (EEM), combined with the hydrochemistry characteristics of the drip water and correlation analysis, were used to analyze the 3D fluorescence spectral characteristics of the DOM of the drip water of Daxiao Cave and their influencing factors. The results show that (1) the hydrochemistry type of the drip water in Daxiao Cave was within the Ca–Mg–HCO3 type, and Ca2+, Mg2+, and HCO3− were the dominant ions in Daxiao Cave; (2) the fluorescence fractions of drip water in dry season caves were dominated by C1 (humus-like), C2 (tryptophan-like), and C3 (tyrosine-like), and the fluorescence fractions of drip water DOM were controlled by protein fluorophores; (3) the DOM in the drip water of Daxiao Cave in the dry season was controlled in part by subsurface leakage and was largely the result of microbial degradation; and (4) the DOM of the drip water may be influenced by the chemical composition of the water, but the exact process is not clear.
The Dabanghe River Basin, in the west of Guizhou Plateau, consists of numerous prominent geological structural features, such as the Shuicheng–Wangmo, Yadu–Ziyun, and Yongningzhen Faults, the Huangguoshu Waterfall, and the Guanjiao Knickpoint. The topographic conditions and structural systems are highly complex, making this a suitable area to study neotectonics. However, research on the geomorphology of the region is lacking. Combined with geomorphic parameters, quantitative exploration of tectonic geomorphic and tectonic activity in the Dabanghe River Basin is of great significance to reveal the formation of the Huangguoshu Waterfall, the development of landforms in western Guizhou, and the regularity of uplift of Guizhou Plateau. Therefore, based on a Digital Elevation Model, GIS software extracted and calculated six geomorphic parameters of the basin: Hypsometric Integral, Asymmetry Factor, Basin Shape Ratio, Stream-Gradient, and Valley Floor Width–Valley Height Ratio (VF) indexes. The tectonic geomorphic characteristics of the Dabanghe River Basin were analyzed, combined with the tectonic activity level classification method, and the Index of Relative Active Tectonics (IAT) of each sub-catchment was calculated. The geomorphic parameters of the basin were found to indicate its geomorphic characteristics well. The tectonic activity in the study area midstream is the most active, and the geomorphic evolution of some upstream and downstream reaches is affected by lithology, topography, and structure. The tectonic geomorphology of the basin is significantly affected by the fault system. Under the control of the Yadu–Ziyun Fault, the tectonic activity in the basin gradually weakens from west to east, and the differential tectonic activity (strong in the mid-reach and eastwards decrease) is consistent with observed seismic intensity. It is confirmed that our research results are consistent with the regional geological background and geomorphic characteristics through field geological survey. Therefore, this study confirms that the use of tectonic geomorphic parameters to classify active tectonics can be an important method to evaluate the stability of the crust in the region and further extends the application of geomorphic parameters in tectonics.
Exploring the hydrogeochemistry of cave drip water and its response to precipitation events in karst rocky desertification regions is of great significance to the paleoenvironment reconstruction of the karst desertification process using speleothem. We selected three perennial drip sites in the Shijiangjun Cave, located in Guizhou Province, Southwest China, and carried outhigh-frequency monitoring and sampling during two rainfalls from 22 to 25 May 2016. The major hydrogeochemical parameters of drip water and their relationships with karst desertification were analyzed. The results show that the hydrogeochemistry of the drip water in the Shijiangjun Cave, characterized by HCO3-Ca·Mg, was dominated by the dissolution of calcareous dolomite. The three drip sites were classified into the delayed response type (W1) and the rapid response type (W2 and W3) based on the response speed of the drip water indicators to precipitation, which were highly influenced by the piston effect and precipitation dilution, respectively. Furthermore, the response sensitivity of the drip water indicators to precipitation was constrained by the desertification degree in the rainy season, specifically, the faster response appeared in the higher desertification degree area. It is essential to select appropriate drip sites and establish an applicable indicator system for the evolutional history reconstruction of karst desertification using speleothems.
Carbon and nitrogen are among the most important biogenic elements in terrestrial ecosystems, and carbon and nitrogen stable isotopes (δ13C and δ15N) are often used to indicate the sources of carbon and nitrogen elements and turnover processes, and the study of C and N isotopes coupling can provide more precise indications. To this end, this study was conducted to investigate the effects of different land use types on soil organic carbon (SOC), soil organic nitrogen (SON) and the coupling relationship of C-N isotopes, as well as to reveal the seasonal variation characteristics of soil C and N. The results showed that SOC and SON contents of forest land were significantly higher than those of agricultural land and grassland. The soil C/N was significantly higher in the dry season than in the rainy season (p < 0.01), indicating that the decomposition rate of soil organic matter (SOM) was faster in the rainy season, which was not conducive to the accumulation of soil C. Soil δ13C and δ15N coupling showed seasonal characteristics: soil δ13C and δ15N did not have a good linear relationship in the rainy season, but showed a significant positive correlation in the dry season (r2 = 0.75, p < 0.05), indicating that there are differences in the soil C-N isotope fractionation coupling under the influence of climatic factors. This study provides a reference for regional land resource management as well as carbon and nitrogen cycle studies in karst areas.
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