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The same cumulative carbon emission reduction target can correspond to multiple emission reduction pathways. This study explores how different coal power transition pathways with the same cumulative emissions reductions impact the transition costs, by assessing the dynamic transition processes for coal plants adopting multiple mitigation technologies concurrently or sequentially, such as flexibility operation, biomass and coal co-firing, carbon capture and storage, and compulsory retirement. We develop a plant-level dynamic optimization model and apply it to China's 4200+ coal plants. We find that under deep decarbonization, the majority of Chinese coal plants retrofit with multiple technologies to reduce emissions and retire naturally at lower costs while contributing to grid stability. Optimizing the pathway can potentially save over 700 billion U.S. Dollars for achieving the same target or increase cumulative emissions reduction from 30% to 50% at no additional cost. This analysis can help inform a cost-effective coal phase-out under China's carbon neutrality., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Dissolved carbon in groundwater plays an important role in carbon cycling and ecological function maintenance, and its concentration level affects the migration and transformation of pollutants in groundwater. To understand the spatiotemporal variation characteristics of dissolved carbon and its driving factors in shallow groundwater around plateau lakes, variations in the concentrations of dissolved organic carbon （DOC）, inorganic carbon （DIC）, and total carbon （DTC） and their driving factors in shallow groundwater （ n = 404） around eight plateau lakes were analyzed. The results indicated that the average values of ρ （DOC）, ρ （DIC）, and ρ （DTC） in shallow groundwater around plateau lakes were 8.23, 49.01, and 57.84 mg·L -1 , respectively, with the ρ （DOC） in 79.0% of shallow groundwater samples exceeding 5 mg·L -1 . There were no significant differences in the DOC, DIC, and DTC concentrations between rainy and dry seasons, whereas the change in dissolved carbon concentrations in shallow groundwater were strongly affected by the intensity of agricultural intensification and the depth of groundwater table； the DOC, DIC, and DTC concentrations in shallow groundwater from facility agricultural regions （SFAR）, cropland fallow agricultural regions （CFAR）, and intensive agricultural regions with deeper groundwater tables （DIAR） were significantly reduced by 25.8% - 56.6%, 14.0% - 32.9%, and 16.6% - 36.7%, respectively, compared with those in intensive agricultural regions with shallower groundwater tables （SIAR）. Additionally, the dissolved carbon concentrations in shallow groundwater from DIAR were significantly lower than those of SFAR and CFAR. RDA revealed that physicochemical factors in water and soil significantly explained the changes in the dissolved carbon concentrations. Moreover, the dissolved carbon concentrations in shallow groundwater around Yilong Lake were significantly higher than those of other lakes, whereas that of Chenghai Lake was significantly lower than that of other lakes. Our study highlights that agricultural intensification intensity and groundwater table depth jointly drove the variations in dissolved carbon concentrations in shallow groundwater around plateau lakes. The study results are expected to provide a scientific basis for understanding the carbon cycle in plateau lake areas with underground runoff flowing into lakes and evaluating the attenuation of pollutants by dissolved carbon in shallow groundwater.

Nucleic acid modifications play important roles in biological activities and disease occurrences, and have been considered as cancer biomarkers. Due to the relatively low amount of nucleic acid modifications in biological samples, it is necessary to develop sensitive and reliable qualitative and quantitative methods to reveal the content of any modifications. In this review, the key processes affecting the qualitative and quantitative analyses are discussed, such as sample digestion, nucleoside extraction, chemical labeling, chromatographic separation, mass spectrometry detection, and data processing. The improvement of the detection sensitivity and specificity of analytical methods based on mass spectrometry makes it possible to study low-abundance modifications and their biological functions. Some typical nucleic acid modifications and their potential as biomarkers are displayed, and efforts to improve diagnostic accuracy are discussed. Future perspectives are raised for this research field.

Elucidating the main sources and transformation process of nitrate for the prevention and control of groundwater nitrogen pollution and the development and utilization of groundwater resources has great significance. To explore the current situation and source of nitrate pollution in shallow groundwater around the Dianchi Lake, 73 shallow groundwater samples were collected in the rainy season in 2020(October) and dry season in 2021(April). Using the hydrochemistry and nitrogen and oxygen isotopes( δ 15 N-NO 3 - and δ 18 O-NO 3 - ), the spatial distribution, source, and transformation process of nitrate in shallow groundwater were identified. The contribution of nitrogen from different sources to nitrate in shallow groundwater was quantitatively evaluated using the isotope mixing model(SIAR). The results showed that in nearly 40.5% of sampling points in the shallow groundwater in the dry season, ρ (NO 3 - -N) exceeded the 20 mg·L -1 specified in the Class Ⅲ water quality standard for groundwater(GB/T 14848), and in more than 47.2% of sampling points in the rainy season, ρ (NO 3 - -N) exceeded 20 mg·L -1 . The analysis results of nitrogen and oxygen isotopes and SIAR model showed that soil organic nitrogen, chemical fertilizer nitrogen, and manure and sewage nitrogen were the main sources of nitrate in shallow groundwater; these nitrogen sources contributed 13.9%, 11.8%, and 66.5% to nitrate in shallow groundwater in the dry season and 33.7%, 31.1%, and 25.9% in the rainy season, respectively. However, the contribution rate of atmospheric nitrogen deposition was only 8.5%, which contributed little to the source of nitrate in shallow groundwater in the study area. Nitrification was the leading process of nitrate transformation in shallow groundwater in the dry season, denitrification was the dominant process in the rainy season, and denitrification was more noticeable in the rainy season than that in the dry season.

The extensive application of phosphorus fertilizers to croplands and the aggregation of towns and villages around plateau lakes has resulted in the continuous accumulation of phosphorus in the soil profile and the discharge of phosphorus pollutants, which causes phosphorus pollution in shallow groundwater around the lakes. The phosphorus entering the lake with shallow underground runoff in the region around the lake also affects the water quality safety of plateau lakes. The spatiotemporal differences in phosphorus concentrations in 452 shallow groundwater samples and the driving factors were analyzed by monitoring wells in croplands and residential areas around the eight lakes in Yunnan province during the rainy and dry seasons from 2019 to 2021. The results showed that seasonal changes and land use influenced phosphorus concentrations and their composition in shallow groundwater. The concentration of phosphorus in shallow groundwater in the rainy season was higher than that in the dry season, and it was also greater in cropland than that in residential areas. DTP was the dominant form of TP, accounting for 75%-81%, and DIP was the dominant form of DTP, accounting for 74%-80%. Nearly 30% of the samples around the eight lakes had TP concentrations exceeding the surface water Class Ⅲ standard (GB 3838); the exceeded rates of phosphorus in groundwater around the Erhai Lake (52%), Qiluhu Lake (45%), Xingyun Lake (42%), and Dianchi Lake (29%) were far higher than those of Yangzonghai Lake (16%), Fuxianhu Lake (13%), Chenghai Lake (6%), and Yilonghu Lake (5%). The key driving factors of phosphorus concentrations in shallow groundwater were water-soluble phosphorus (WEP), water content (MWC), soil organic matter (SOM), total nitrogen (TN), pH in the soil profile, and pH and groundwater level in the shallow groundwater ( P <0.05). The increases in WEP, SOM, TN, and MWC in the soil and pH in groundwater significantly increased the concentrations of DIP and DTP in shallow groundwater, whereas the decrease in groundwater level significantly reduced the concentrations of DTP and DIP in the groundwater.

Shallow groundwater around plateau lakes is one of the important sources of production and potable water. Shallow groundwater NO 3 - -N pollution driven by factors such as surface nitrogen input load, rainfall, and irrigation is serious and threatens the water quality of plateau lakes. In order to identify the characteristics of nitrogen pollution and its driving factors in shallow groundwater, 463 shallow groundwater samples were collected from wells in farmland and residential areas around eight plateau lakes of Yunnan in the rainy and dry seasons in 2020 and 2021. The results showed that the average values of ρ (TN), ρ (NO 3 - -N), ρ (ON), and ρ (NH 4 + -N) in shallow groundwater were 24.35, 15.15, 8.41, and 0.79 mg·L -1 , respectively. Nearly 32% of the shallow groundwater samples around the eight lakes failed to meet the groundwater Class Ⅲ water quality requirements (GB/T 14848) of 20 mg·L -1 for NO 3 - -N. Among them, the NO 3 - -N concentration in the shallow groundwater around Erhai Lake, Qiluhu Lake, and Dianchi Lake had the highest rate of exceeding the standard, followed by that around Xingyunhu Lake, Yangzonghai Lake, Yilonghu Lake, Fuxianhu Lake, and Chenghai Lake as the smallest. Land use and seasonal changes affected the concentration and composition of various forms of nitrogen in shallow groundwater. The concentration of various forms of nitrogen in shallow groundwater in the farmland area was higher than that in the residential area. The nitrogen concentration in shallow groundwater in farmland was higher than that in residential areas. Except for NH 4 + -N, the concentration of various forms of nitrogen in shallow groundwater in the rainy season was higher than that in the dry season. NO 3 - -N was the main nitrogen form in shallow groundwater; the fraction of TN was 57%-68%, and the fraction of ON was 27%-38%. The EC, DO, ORP, and T in shallow groundwater were the key factors reflecting or affecting the concentration of various forms of nitrogen in shallow groundwater, whereas soil factors had a weak impact on the concentration of various forms of nitrogen in shallow groundwater.

Mitigating greenhouse gas emissions is necessary to reduce the overall negative climate change impacts on crop yields and agricultural production. However, certain mitigation measures may generate unintended consequences to food availability and food access due to both land use competition and economic burden of mitigation. Integrated assessment models (IAM) are generally used to evaluate these policies; however, currently these models may not capture the importance of income and food prices for hunger and overall economic wellbeing. Here, we implement a measure of food security that captures the nutritional and economic aspects as the total expenditures on staple foods divided by income and weighted by total caloric consumption in an IAM, the global change analysis model (GCAM4.0). We then project consumer prices and our measure of food security along the shared socioeconomic pathways. Sustained economic growth underpins increases in caloric consumption and lowering expenditures on staple foods. Strict conservation policies affect food accessibility in a larger number of developing countries, whereas the negative effects of pricing terrestrial emissions are more concentrated on the poor in Sub-Saharan Africa, by substantially replacing their cropland with forests and affecting the production of key staples., Supplementary Information: The online version contains supplementary material available at 10.1007/s10669-022-09860-4., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© Crown 2022.)