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The coastal zone is sensitive to sea–land interaction, making it an ideal place to study the transgression–regression process in Quaternary coastal areas. Based on the stratigraphic and lithologic characteristics of two Quaternary drill cores (DZ01 and DZ02) in the coastal zone of Quanzhou Bay, Fujian Province, a stratigraphic chronological framework was established by using AMS-14C and OSL dating methods. Combined with the statistical analysis results of geochemical element content of indicating facies in modern sediments in Quanzhou Bay, the geochemical element ratios, foraminifers, and ostracods' environmental indicators were used to identify transgressive strata since the Late Pleistocene. The transgression–regression processes since the MIS 3 in Quanzhou Bay were analyzed by comparing it with the regional borehole data. The results show that the Sr/Ba and Mn/Fe values vary significantly in the marine sediments at different water depths in Quanzhou Bay, making them suitable as indicator elements in the marine and sea–land transitional sediments in the Quanzhou Bay coast, with the limit values of Sr/Ba

An ecological security pattern is an essential natural solution for promoting the coordinated and sustainable development of urban growth and the ecological environment within a given region. This study aims to develop a comprehensive ecological security pattern (ESP) for the Jinjiang watershed by integrating multiple ecological service functions: ecological regulation, eco-product provisions, and human settlement services. Using a well-established methodology of "source identification—resistance surface construction—ecological corridor extraction", we identified 322 ecological source areas and delineated 321 ecological corridors spanning 1941.67 km, with key corridors connecting ecological regulation sources and ordinary corridors primarily linking eco-product provisions and human settlement sources. Our results show that the northern hilly regions are significant for ecological regulation, Anxi County is key for eco-product provisions, and human settlement services are scattered across urban areas and river valleys. This integration enhances regional ecological sustainability and provides a model for similar coastal regions globally. Our findings offer scientific guidance for balancing urban growth with ecological preservation, contributing to sustainable development worldwide. [ABSTRACT FROM AUTHOR]

While climate change significantly influences nitrogen cycling and its related microbial diversity, the effects of warming on nitrate reduction processes and their related microbial communities and functional gene abundances in mangrove sediments are not fully understood. In this study, mangrove sediment slurry was incubated under six controlled temperatures for 28 days to simulate warming trends. Following the incubation, rates of denitrification (DNF), anaerobic ammonium oxidation (ANA), and nitrate decomposition reduction to ammonium (DNRA), and net nitrous oxide (N2O) production, functional gene abundances, and the structure of functional microbial taxa were investigated using a 15N tracer method, high-throughput sequencing, and qPCR methods. DNF's optimal temperature was 25 °C, but ANA's ranged from 25 to 35 °C. The DNRA rates; nosZ, nirS, and nrfA gene abundances; nosZ/(nirK + nirS) ratios; and, in particular, net N2O production in the mangrove sediment significantly increased with increasing temperature. Furthermore, DNRA's contributions to nitrate reduction increased from 26.70% at 10 °C to 44.42% at 40 °C, suggesting that the DNRA process transforms more nitrate to ammonia and retains more nitrogen within mangrove sediments than the other processes do. Meanwhile, microbial taxa changed significantly in relation to DNRA, indicating that DNRA is enhanced as temperature increases. Also, temperature explained most of the variance in the dominant bacterial communities (68.3%), nitrate reduction functional genes (91.8%), and process rates (79.9%). Thus, warming promotes nitrogen conservation in mangrove sediments but stimulates N2O emissions, which in turn exacerbates global warming. [ABSTRACT FROM AUTHOR]

Rivers are an important source of water in humid regions, but their availability is greatly limited by water chemistry. In order to accurately identify the changes in river water chemical composition, the compositional analysis method (CoDA) is proposed from the perspective of compositional data analysis theory, which considers the geochemical riverine system as a whole and detects the compositional changes of the entire watershed. The basic data analysis is carried out by traditional analysis methods, and the results show that the hydrochemical characteristics of different sections of the basin have significant features. The water chemistry of Dongxi River is of the HCO3− Ca type. The water of the Xixi River shows a gradual evolution from the HCO3-Ca type and high SO42− content in the upper reaches to the Cl-Ca type in the lower reaches. The hydrochemistry of river water in the watershed is mainly affected by rock weathering leaching (PC1) and agricultural and domestic pollutant discharge (PC2), with a contribution rate of 48.4% and 19.7%, respectively. Rock weathering, mining, and agricultural pollution are the main factors affecting the chemical composition of river water in different regions. The spatial composition of a single sample at different scales is monitored by the Mahalanobis distance approach in an iterative manner to minimize the influence of a single anomaly on the composition center. The results show that the main reasons for the change in river water chemical composition along the Xixi River are attributed to mine pollution, domestic pollution, and tea plantation and that along the Dongxi River is caused by domestic pollution. The hydrochemical composition changes after the confluence of the Xixi River and Dongxi River are mainly affected by human activities and seawater in urban areas. This research could provide new perspectives and methods for detecting the influences of human and natural factors on the hydrochemistry of river water in humid regions worldwide. [ABSTRACT FROM AUTHOR]

To investigate the influence of the Hutuo River (North China) ecological water replenishment project on the hydrogeochemical processes of groundwater, 64 groundwater samples collected at different time intervals after four replenishment events, and four samples from the Middle Route of the South-to-North Water Diversion Project water, were analyzed for water chemistry. Hydrogeochemical methods such as the Piper diagram, chloride-alkalinity index, and ion correlation were employed to analyze the characteristics of groundwater chemical evolution through replenishment. The results demonstrated that the hydrochemical types of groundwater in the study area underwent significant changes during continuous replenishment in the Hutuo River region. During the initial replenishment period (October 2019), the dominant hydrochemical type of groundwater in the study area was Mg-Na-HCO3-SO4, whereas the dominant type in the Middle Route of the South-to-North Water Diversion Project water was Ca-Na-SO4-HCO3. As the replenishment continued, the hydrochemical types of groundwater in the study area evolved into Ca-Na-Mg-HCO3-SO4, Na-Ca-Mg-HCO3-SO4, and Ca-Na-Mg-SO4-HCO3. The groundwater experienced a dissolution of calcite, gypsum, nitratine, carbonate rocks, and gypsum, accompanied by dilution effects, resulting in reduced ion exchange as replenishment progressed. The input of the high quality Middle Route of South-to-North Water Diversion Project water effectively promoted groundwater quality improvement, leading to an overall decrease or stabilization of components other than Ca2+ in the groundwater. Water quality was assessed using the entropy water quality index, with indicators including Na+, SO42−, Cl−, pH, total dissolved solids, NO3−-N, NO2−-N, F−, Al, As, and Zn. The evaluation results showed that, except for one medium-quality water sample, the water quality of the other samples was suitable for drinking and domestic purposes during the early replenishment period. The Middle Route of the South-to-North Water Diversion Project exhibited excellent quality (Rank 1), and as replenishment progressed, all water samples demonstrated good quality by October 2020, with a gradual improvement. [ABSTRACT FROM AUTHOR]