Net Accumulation Research Articles

Sargassum beaching on mangrove sediments shifts microbial and crab metabolisms and enhances blue carbon storage

AbstractBenthic metabolism and net carbon accumulation in mangroves sediments strongly depend on the quantity and quality of organic matter (OM) supplied, including material brought by coastal waters such as the macroalgae Sargassum spp. Mesocosms were used to assess the effect of eutrophication by Sargassum on mangrove sediments. The concentration of fatty acids (FAs), organic carbon and its carbon isotopic signature, and the sediments–air CO2 fluxes were used to follow the evolution of sedimentary OM in surface and subsurface sediments for 60 d. Sargassum beaching shifted microbial and crab metabolism, leading to a preferential degradation of the labile fraction of OM from both Sargassum (δ13C = −17.7‰ and high concentration of essential FAs) and mangrove leaves (δ13C: −28.9‰ and high concentrations of 18:2ω6 and 18:3ω3). Fatty acids composition of crabs hepatopancreas revealed they preferentially fed on Sargassum and these invertebrates also increased the particulate OM tidal export. In addition, microbial activity at the sediment surface was enhanced, as revealed by strong production of branched FAs and higher CO2 fluxes in mesocosms containing Sargassum. However, Sargassum beaching also increased the transfer and preservation of more refractory OM from mangrove leaves found in higher quantity in subsurface sediments (6–8 cm) after 60 d. Inputs of macroalgae induced a negative priming effect and enhanced the preservation of blue carbon in the sediments. This negative priming effect was enhanced by crab activities. These biotic interactions that include microbial communities apparently make mangrove efficient in storing carbon in a context of growing eutrophication of the tropical ocean.

The Impact of Short-Term Drought on the Photosynthetic Characteristics and Yield of Peanuts Grown in Saline Alkali Soil

Peanuts grown in saline alkali soil are also subjected to drought stress caused by water scarcity. Therefore, we used HY25 (peanut variety) as an experimental material to investigate the effects of drought on the height of peanut main stems, length of the first lateral branch, leaf area per plant, SPAD value, net photosynthetic rate, and accumulation and distribution of photosynthetic products in saline alkali soil. The results showed that the combined stress of short-term drought and salt significantly reduced the main stem height, first lateral branch length, single plant leaf area, SPAD value, net photosynthetic rate (Pn), intercellular carbon dioxide concentration (Ci), and dry matter accumulation of peanuts, including a decrease in single plant pod yield, 100-pod weight, 100-kernel weight, and peanut yield. And the impact of drought stress on peanut yield varies at different growth stages. For example, under drought stress alone, the sensitive period is the 40th day after planting (40D) > 60th day after planting (60D) > 30th day after planting (30D). Short-term drought has the greatest impact on peanut yield at 40D, while in contrast, resuming watering after drought at 30D results in a slight but not significant increase in peanut yield in comparison with the control. Under the combined stress of drought and salt, the sensitive period of peanuts was 40D > 30D > 60D, and the single pod weight of peanuts was significantly reduced by 15.26% to 57.60% from the flowering stage to the pod stage under drought treatment compared to salt treatment, indicating a significant interaction between drought and salt stress, reducing the single leaf area and net photosynthetic rate of peanut leaves, ultimately leading to a decrease in peanut yield. Therefore, when planting peanuts in saline alkali soil, drought should be avoided, especially early drought, in order to prevent the combined effects of drought and salt stress from harming peanut yield.

Keynes and the Long Run — to ‘Live Wisely and Agreeably and Well’

ABSTRACT This paper revisits Keynes’s essay titled ‘The economic possibilities for our grandchildren’, featuring Keynes both as a growth theorist and a moral and social philosopher of capitalism. We discuss the three broader trends identified by Keynes that he expected would come to characterize the socio-economic evolution of advanced countries under capitalism: first, continued technological progress and capital accumulation as the main drivers of exponential growth in economic possibilities; second, a gradual general rebalancing of life choices away from work; and third, a change in the code of morals in societies approaching an envisioned stationary state of zero net capital accumulation in which mankind has solved its economic problem and enjoys a lifestyle predominantly framed by leisure rather than disutility-yielding work. We assess actual outcomes by 2024 and attempt to peek into the future economic possibilities for this generation’s grandchildren.

Butterfly species vary in sex‐specific sodium accumulation from larval diets

Abstract Sodium is essential for animals, and its heterogeneous distribution can cause a range of phenomena, from sodium‐seeking behaviours to impacting their performance. Although sodium content in soils and plants is relatively well documented, data for higher trophic levels are limited. Knowledge of the variation in sodium in lower trophic levels could have implications for understanding the behaviour and physiology of species at higher levels. We investigated the variation in tissue sodium concentration between males and females of four butterfly species. Puddling behaviour of Lepidoptera suggests sodium needs of males are generally greater than females, thus, we predicted males would accumulate more sodium than females on a given diet. Larvae were reared on plants (for Battus philenor, Chlosyne lacinia and Danaus plexippus) and an artificial diet (for Pieris rapae) under Low Na (no added sodium) and High Na (sodium added) conditions. Among species and sexes, we quantified and compared adult absolute tissue sodium concentrations and bioconcentration factors, which indicate net sodium accumulation or excretion relative to individuals' diets. On average, individuals on low‐sodium diets had higher bioconcentration values across all species. Male butterflies accumulated significantly higher sodium concentrations than females in two sodium treatments for B. philenor, and P. rapae and only in the High Na treatment for C. lacinia. However, in D. plexippus, individuals accumulate sodium in the High Na treatment, but males and females responded in the same way. Our study revealed sex‐ and species‐specific patterns of butterfly sodium accumulation, which could be linked to variations in behaviour and/or performance. Differences in sodium content across species have implications for variation in predation and trophic‐level interactions, an interesting avenue for future ecological and evolutionary research.

Model-driven design and validation of glucose supply control in a tubular photobioreactor operated under oxygen-balanced mixotrophy

Scaling up bioprocesses remains challenging due to the partially unpredictable and suboptimal behavior of microbes during scale transition. Mathematical modelling serves as a valuable tool in navigating these challenges. In this study, we developed and validated a kinetic model based on the tank-in-series approach for a novel bioprocess known as oxygen-balanced mixotrophy with the microalga Galdieria sulphuraria. This model aims to facilitate the design of an effective glucose feeding control strategy tailored for two-phase tubular photobioreactors (TPBRs). The residence time distribution of our reference reactor was investigated by means of a tracer experiment. Qualitative analysis of the results indicated that our system was optimally represented by simulations with a 100 stirred-tank reactors (STRs).The controlled variable, oxygen concentration in the gas phase, showed a downward trend in simulations with simplified conditions: fixed oxygen production and balanced glucose supply. The decrease was caused by dominant net heterotrophic activity and accumulation of CO2 in the gas phase. Different configurations of a proportional-integral-derivative (PID) controller were designed by means of the ultimate gain method and compared under these simplified conditions. The most effective PID controller was implemented and refined in simulations with outdoor weather conditions. The model was validated successfully by simulating over time in a lab-scale STR the spatial fluctuations happening in a TPBR. The empirical oxygen consumption and production were faster and steeper than in the model, probably due to inaccuracies in parameter estimation or biomass adaptation.

Nutrient accumulations in high-saline bottom waters in the eutrophic East China Sea inner shelf

Despite decades of mitigation efforts, eutrophication-induced algal blooms and hypoxia have not significantly decreased globally, possibly due to the legacy effects of eutrophication. The legacy effect has been more explored in inland waters and enclosed estuaries than in open coastal waters. Here, we reanalyzed cruise data from the East China Sea inner shelf to explore the effect of eutrophication on nutrient accumulations in high-saline bottom waters. Our dataset showed elevated nitrate (12.75 ± 6.51 μmol L−1) and phosphate (0.85 ± 0.26 μmol L−1) in high-salinity (salinity>34, temperature < 23 °C) bottom waters during the summer of 2006 to 2013. They were higher than those typically observed in the Taiwan Warm Current Bottom Water by approximately 5.45 ± 6.51, and 0.29 ± 0.26 μmol L−1, respectively. Significant correlations of nitrate with apparent oxygen utilization (AOU) and elevated AOU suggested that organic matter decomposition contributed to increased nitrate in bottom waters under eutrophication conditions. Based on an end-member mixing estimation, we found that the organic matter decomposition accounted for 28% to 37% of the nutrient concentrations in the bottom waters, with a standard deviation of 20%. Results from our mass-balance model indicated that 40–74% of regenerated nutrients are flushed out of the model box set within 95% equilibrium time due to the advection of offshore waters, assuming a residence time of 46.0 to 13.9 days. Based on cruise results in June and August 2009, the net accumulation rates of nitrate, phosphate, and AOU in the Taiwan Warm Current Bottom Water were estimated to be 0.046, 0.0036, and 0.44 μmol L−1 d−1, respectively. Such nutrient accumulations in the water column and the residual nutrients in sediment are crucial legacy nutrients, potentially triggering algal blooms. Conversely, the flushing effect suggests a significant transport of nutrients and other chemical elements to the offshore and open ocean.

Response of dissolved inorganic carbon dynamics to simulated tidal hydrological processes in coastal wetlands

To clarify the impacts of tidal hydrological process shifts caused by sea level rise on the blue carbon cycle, a typical coastal wetland in Jiaozhou Bay was selected for this study. The soils of Suaeda salsa (SS) and Phragmites australis (PA) wetlands were collected to simulate the effects of three types of tidal hydrological processes (Neap tide group, NT; Middle tide group, MT; Spring tide group, ST) on the soil-water dissolved inorganic carbon (DIC) dynamic. The results showed that the concentration of water dissolved inorganic carbon (WDIC) increased rapidly (115% higher) at early stage (days 0–4) under the influence of the tidal hydrological processes. Significant differences were found in WDIC concentration during different tidal hydrological processes (P < 0.05), which were expressed as MT (52.7 ± 13.3 mg L−1) > ST (52.5 ± 12.9 mg L−1) > NT (48.4 ± 10.1 mg L−1). After experiencing the tidal hydrological processes, the soil DIC content showed a net accumulation (55.1 ± 1.29 mg L−1vs. 46.7 ± 1.76 mg L−1, P < 0.001), whereas the soil inorganic carbon (SIC) decreased (2.73 ± 1.64 mg L−1vs. 4.61 ± 1.71 mg L−1), which may be attributed to the dissolution of SIC caused by the uptake of CO2 to form DIC. The accumulation of soil DIC was directly related to the SIC (λ = 1.03, P < 0.01), and indirectly related to soil nutrients (SOC substrate, λ = −0.003) and microbes (microbial biomass, λ = −0.10), and was mainly dominated by abiotic processes (abiotic: 58.1 ± 1.8% to 82.7 ± 2.46% vs. biotic: 17.4 ± 2.46% to 41.9 ± 1.76%). The increase of tidal frequency generally inhibited the accumulation of soil DIC content and promoted the output of WDIC. However, the response of soil DIC in different wetland types to tidal frequency was divergent, which was mainly regulated by the trade-off between soil nutrients and SIC content. Taken together, tidal hydrological processes and their frequency changes reshaped DIC dynamics, promoted the dissolution of SIC and the potential uptake of CO2. These findings enhance the comprehension of the inorganic carbon cycle within coastal wetlands, particularly amidst the backdrop of climate change and the rising sea levels.

Estimation of net accumulation and removal of fluorescent dissolved organic matter in different Baltic Sea water masses

This study aimed to detect non-conservative processes that affect the distribution of fluorescent dissolved organic matter (FDOM) in the Baltic Sea. An extensive data set comprised of 408 FDOM data, optical and physical profiles, and the development of a water masses balance model allowed us to ascertain the sources of mixing anomalies. These were seen as second-order deviations in the FDOM distribution as a function of salinity in three layers: surface water, Baltic Sea Winter Water, and deep water. The difference between modeled and measured FDOM values at three different excitation/emission wavelengths allowed to show the strength of non-conservative processes, such as photochemical and microbial decomposition (negative residual values) or extracellular release of dissolved organic matter from phytoplankton, heterotrophic uptake and release from anoxic sediments (positive residual values). Humic-like FDOM fractions displayed positive residuals in all seasons for intermediate and deep layers and negative residuals in surface waters. Largest accumulation rates of humic-like fractions were reached in the Gulf of Gdańsk during summer in intermediate and deep layers, while the greatest removal in surface waters was observed during spring in the Bornholm and Gotland Basins and during summer in the Gulf of Gdańsk, probably due to photodegradation. Positive residuals of the protein-like fraction were observed at the surface in summer and autumn in the Gulf of Gdańsk, probably linked to the abundance of phytoplankton and also due to the low molecular weight by-products of photodegradation of humic-like components. Spatial transects revealed an increase in humic-like residuals with depth and a strong correlation with apparent oxygen utilization, increasing with higher fluorescence and exhibiting an asymptotic trend. A relationship was found between the protein-like fractions and phytoplankton biomass proxies. A generalized concept for FDOM cycling in the Baltic Sea was proposed, highlighting photobleaching as the dominant non-linear process determining the efficiency of humic-like FDOM removal. The protein-like component was found to be more efficiently taken up by aerobic prokaryotes at the surface. Microbial utilization and reworking of organic matter, release from sediments, and a decade-long stagnation of bottom water masses, all contribute to the observed accumulation of FDOM in mesohaline deep waters below the permanent pycnocline in the Baltic Sea.

Prediction of net primary productivity in the middle-to-high latitudes of Eurasia based on snow and soil temperature

Net primary productivity (NPP) is the net accumulation of organic matter by vegetation through photosynthesis and serves as a key indicator for exploring vegetation responses to climate change. Considering the remote and local impacts of soil heat capacities on vegetation growth through pathways of atmospheric circulation and land–atmosphere interaction, this paper develops a statistical prediction model for NPP from April to June (AMJ) across the middle-to-high latitudes of Eurasia. The model introduces two physically meaningful predictors: the snow water equivalent (SWE) from February to March (FM) over central Europe and the FM local soil temperature (ST). The positive phase of FM SWE triggers anomalous eastward-propagating Rossby waves, leading to an anomalous low-pressure system and cooling in the middle-to-high latitudes of Eurasia. This effect persists into spring through snow feedback to the atmosphere and affects subsequent NPP changes. The ST is closely related to the AMJ temperature and precipitation. With positive ST anomalies, the AMJ temperature and precipitation exhibit an east–west dipole anomaly distribution in this region. The single-factor prediction scheme using ST as the predictor is much better than using SWE as the predictor. Independent validation results from 2009 to 2014 demonstrate that the ST scheme alone has good predictive performance for the spatial distribution and interannual variability of NPP. The predictive skills of the multi-factor prediction schemes can be improved by about 13 % if the ST predictor is included. The findings confirm that local ST is a predictor that must be included for NPP prediction.摘要净初级生产力 (NPP) 是植被通过光合作用积累机物质的净效益, 是探索植被对气候变化响应的关键指标. 考虑到陆面热力异常通过陆气相互作用和大尺度环流对植被生长的影响, 本文研制了欧亚中高纬地区4–6月NPP预测模型. 该模型引入了两个具有明确物理意义的预测因子: 欧洲中部2–3月的雪水当量 (SWE) 和2–3月局地土壤温度 (ST). SWE的正异常会触发异常东传的Rossby波, 导致下游出现位势高度负异常并引起降温. 通过雪和温度的正反馈, 这种异常低温持续到春季并使得NPP下降. ST与随后季节的温度和降水密切相关, 当ST出现正异常时, 该地区的4–6月温度和降水呈现出东西向偶极子异常分布.对比各方案的预测效果发现, ST比SWE有更好的预测能力. 2009–2014年独立后报结果显示, ST方案对NPP的空间分布和年际变率都有很好的预测效果. 交叉检验的结果显示, 多因子方案中引入ST后能提高模型13 %的预测技巧.

Missing phosphorus legacy of the Anthropocene: Quantifying residual phosphorus in the biosphere.

A defining feature of the Anthropocene is the distortion of the biosphere phosphorus (P) cycle. A relatively sudden acceleration of input fluxes without a concomitant increase in output fluxes has led to net accumulation of P in the terrestrial-aquatic continuum. Over the past century, P has been mined from geological deposits to produce crop fertilizers. When P inputs are not fully removed with harvest of crop biomass, the remaining P accumulates in soils. This residual P is a uniquely anthropogenic pool of P, and its management is critical for agronomic and environmental sustainability. Managing residual P first requires its quantification-but measuring residual P is challenging. In this review, we synthesize approaches to quantifying residual P, with emphasis on advantages, disadvantages, and complementarity. Common approaches to estimate residual P are mass balances, long-term experiments, soil test P trends and chronosequences, with varying suitability or even limitations to distinct spatiotemporal scales. We demonstrate that individual quantification approaches are (i) constrained, (ii) often complementary, and (iii) may be feasible at only certain time-space scales. While some of these challenges are inherent to the quantification approach, in many cases there are surmountable challenges that can be addressed by unifying existing P pool and flux datasets, standardizing and synchronizing data collection on pools and fluxes, and quantifying uncertainty. Though defined as a magnitude, the distribution and speciation of residual P is relatively less understood but shapes its utilization and environmental impacts. The form of residual P will vary by agroecosystem context due to edaphoclimatic-specific transformation of the accumulated P, which has implications for management (e.g., crop usage) and future policies (e.g., lag times in P loading from non-point sources). Quantifying the uncertainty in measuring residual P holds value beyond scientific understanding, as it supports prioritization of monitoring and management resources and inform policy.

Characterizing Spatial and Temporal Trends in Net Sediment Accumulation in Seagrass Meadows

Seagrass meadows are known as hot spots for carbon accumulation, but there is limited field data on the variability of sediment accumulation across time and space. We developed a method to assess spatial and temporal heterogeneity in net sediment accumulation in seagrass meadows using small, inexpensive samplers, allowing for over 200 unique measurements across multiple transects within our study site. Using this method, we assessed sediment accumulation across seagrass meadow edges, and in varying weather conditions. We found the greatest accumulation of sediment 5 m outside of seagrass meadow edges, with sediment accumulation rates averaging just under 100 g m−2 day−1, though rates were highly variable. Carbon accumulation from settled sediment was generally greater outside of seagrass meadow edges than within the bed, especially at sites undergoing recent expansion. Measurements made during tropical storms showed both scouring of sediment away from sites, and increased accumulation, depending on site properties as well as individual tropical storm characteristics. In the storm that had a measurable storm surge, scouring of sediment was a more dominant mechanism, whereas deposition dominated in the storm that had high winds but no associated storm surge. Our data demonstrate the necessity of including measurements that characterize both spatial and meteorological variability to develop a more holistic understanding of the movement of sediment and particulate organic carbon associated with seagrass meadows, especially as meadow area becomes increasingly fragmented with human activity and global change.

A Whole Plant Analysis of Chloride and Sodium Exclusion Using a Range of Grapevine Rootstock Genotypes

Background and Aims. Salt exclusion is an important attribute for wine grapes since many countries have limits to the concentration of sodium (Na+) and/or chloride (Cl−) tolerated in wine. The aim was to investigate whole plant capacity for Na+ and Cl‾ exclusion and the within-plant partitioning of accumulated ions to better understand these important salt tolerance traits. Methods and Results. Rooted cuttings of 140 Ruggeri and K51-40 (good and poor shoot Cl− excluders, respectively) and five hybrids from a cross between the two genotypes were used. When challenged with salinity, 140 Ruggeri limited the accumulation of Cl− and Na+ in the stem, petioles, and laminae and had a significantly lower whole plant concentration of Cl− and Na+ when compared to K51-40. The latter indicates that 140 Ruggeri accumulates less Cl− and Na+ than K51-40 by a lower uptake or a potentially greater efflux by roots, or both. While K51-40 accumulated significantly more Na+, it was able to retrieve it from the xylem; store it in the roots, stem, and petiole; and keep the lamina concentration comparable to that of 140 Ruggeri. Petioles of all genotypes appeared to play a role in limiting Cl− accumulation in laminae and particularly for K51-40, to limit Na+ accumulation in laminae. Conclusions. The grapevine capacity for Cl− and Na+ exclusion can be defined primarily as the lower net accumulation on a whole plant basis, reflecting the difference between the uptake and any efflux that may occur. Lower root to shoot transport is a key factor in shoot Cl− and Na+ exclusion. Petiole accumulation assists in limiting the Cl− and Na+ accumulation in the laminae. Significance of the Study. The study addressed the knowledge gap by examining Cl− and Na+ exclusion on a whole plant basis, highlighting a range of within-plant mechanisms that act in limiting the accumulation of both ions in the laminae.

Long‐term successive biochar application increases plant lignin and microbial necromass accumulation but decreases their contributions to soil organic carbon in rice–wheat cropping system

AbstractBiochar application is widely recognized as an effective approach for increasing soil organic carbon (SOC) and mitigating climate change in agroecosystems. However, the effects of biochar application on net accumulations and relative contributions of different SOC sources remain unclear. Here, we explored the effects of biochar application on plant‐derived (PDC) and microbial necromass C (MNC) in a 10‐year experimental rice–wheat rotation field receiving four different intensities of biochar application (0, 2.25, 11.5, and 22.5 t ha−1 for each crop season), using phospholipid fatty acids (PLFAs), lignin phenols and amino sugars as biomarkers of microbial biomass, PDC and MNC, respectively. Our results showed that biochar application increased SOC content and stock by 32.6%–203% and 26.4%–145%, respectively. Higher biochar application (11.5 and 22.5 t ha−1) increased soil pH, total nitrogen (TN), total phosphorus (TP), SOC/TN, and root biomass. In addition, higher biochar application enhanced bacterial, fungal, and total microbial biomass. Plant lignin phenols and MNC contents significantly increased, whereas their contributions to SOC significantly decreased with the increase in biochar application rates due to the disproportionate increase in PDC and MNC, and SOC. Fungal necromass had a greater contribution to SOC than bacterial necromass. The fungal/bacterial necromass decreased from 2.56 to 2.26 with increasing biochar application rates, because of the higher abundances of bacteria than that of fungi as indicated by PLFAs under higher biochar application rates. Random forest analyses revealed that pH, TP, and SOC/TN were the main factors controlling plant lignin and MNC accumulation. Structural equation modeling revealed that biochar application increased lignin phenols by stimulating root biomass, whereas enhanced MNC accumulation was primarily from increased microbial biomass and lignin phenols. Overall, our findings suggest that biochar application increases the accumulation of the two SOC sources but decreases their contributions to SOC in paddy soils.

Brain-inspired computing with fluidic iontronic nanochannels

The brain's remarkable and efficient information processing capability is driving research into brain-inspired (neuromorphic) computing paradigms. Artificial aqueous ion channels are emerging as an exciting platform for neuromorphic computing, representing a departure from conventional solid-state devices by directly mimicking the brain's fluidic ion transport. Supported by a quantitative theoretical model, we present easy-to-fabricate tapered microchannels that embed a conducting network of fluidic nanochannels between a colloidal structure. Due to transient salt concentration polarization, our devices are volatile memristors (memory resistors) that are remarkably stable. The voltage-driven net salt flux and accumulation, that underpin the concentration polarization, surprisingly combine into a diffusionlike quadratic dependence of the memory retention time on the channel length, allowing channel design for a specific timescale. We implement our device as a synaptic element for neuromorphic reservoir computing. Individual channels distinguish various time series, that together represent (handwritten) numbers, for subsequent in silico classification with a simple readout function. Our results represent a significant step toward realizing the promise of fluidic ion channels as a platform to emulate the rich aqueous dynamics of the brain.

Assessment of contamination dispersion in a porous aquifer environment using explicit and implicit methods in the MODFLOW–MODPATH model

This study presents a meticulously edited article that assesses the uncertainty associated with contamination dispersion in a porous aquifer environment. The article employs a conceptual model incorporating finite difference flow modeling and particle tracking methods grounded in particle movement theory within groundwater flow. The groundwater flow model utilizes an automatic calibration technique, PES, and independent verification, to minimize statistical discrepancies in the optimized parameters. The statistical summary of the model output reveals the average pollution concentration in the study area, specifically the landfill aquifer in northern Iran. The results indicate that the initial contamination value at the boundaries is zero, whereas 91,802 units are discharged into the sea. Moreover, approximately 3,317,290,003 pollution units have been extracted from pumping wells along the contamination plume over 10 years. Furthermore, the drainage network releases 1,778,680,001 pollution units, resulting in a net outflow of 5,082,740,007 units from the same drainage network. Additionally, 9,912,180,003 units were discharged from the leaky boundaries. It should be noted that these statistics can be reversed depending on the specified period. The difference between the input and output pollution values in the study area indicates a net accumulation of 8192 units. To analyze the sensitivity of contamination dispersion in the porous aquifer environment and the variations in coastal drainage patterns obtained from the finite difference simulation, the explicit and implicit methods, as well as the random walk particle tracking method, were investigated in a portion of the basin area using the South Side Implicit method. One of the main objectives of this sensitivity analysis is to evaluate the results of the uncalibrated qualitative model and examine the particle dispersion in the adjacent area of the contaminated landfill region to assess the error of the proposed model by developing a limited test. The calculated error or computational difference between the explicit and implicit methods and the applet model is considered negligible. For example, the calculated error between the explicit and backward methods and the applet model ranges from 0.086 to 0.372 units for a concentration interval of 0.512 units and 0.680 units for a time interval 0.537. Therefore, the computational differences are not significant. Furthermore, based on theoretical sensitivity analysis of contamination dispersion, the laboratory model demonstrates that the flow direction in this modeling is from west to east, as expected.

Fifty years of firn evolution on Grigoriev ice cap, Tien Shan, Kyrgyzstan

Abstract. Grigoriev ice cap, located in the Tien Shan mountains of Kyrgyzstan, has a rich history of firn and ice core drilling starting as early as 1962. Here we extend the exceptional record and describe an 18 m firn core, drilled in February 2018 on the summit of Grigoriev ice cap, at 4600 m a.s.l. The core has been analyzed for firn stratigraphy, major ions, black carbon, water stable isotope ratios and total β activity. We find that the core covers 46±3 years and overlaps by 2 to 3 decades with legacy cores. A good agreement is found in major ion concentrations for the overlapping period. Concentrations of black carbon and major ions are reduced since the early 2000s, indicating the onset of meltwater runoff. Nevertheless, general concentration trends of these species are consistent with observations and Central Asian ice core records, since emissions were highest during periods when melt influence was negligible. The record of water stable isotopes does not reflect the strong increase of air temperatures during the last decades, implying that water stable isotope ratios ceased to be proxies of temperature variations at this site. Apart from runoff evidence, however, the firn's thermal regime appears remarkably unchanged. Firn temperatures in 2018 were the highest on record (∼-1.6 °C at ∼17 m depth). However, temperatures in 2023 are again similar to the early 2000s at ∼-2.5 °C. Furthermore, we find little change in net accumulation since the 1980s. We hypothesize (i) that firn temperatures are stabilized by the removal of latent heat through lateral meltwater runoff, and (ii) that mass loss by runoff is compensated by an increase in accumulation. Data from a nearby weather station support the latter hypothesis.

Litterfall-Associated Carbon Deposition and Vertical Profiles of Soil Organic Carbon in Different Land-Use Systems

Litterfall is one of the major inputs for soil nutrients. Understanding the connection of litterfall and soil organic carbon (SOC) as the part of ecological processes is a key step towards carbon sequestration as a climate change mitigation strategy. Yet, it remains inadequate to support by empirical pieces of evidence particularly in tropical ecosystems. In this study, litter traps were used to monitor the monthly organic carbon deposition over a year through litterfall, and soil samples were collected vertically up to 30 cm depth to define the SOC depth distribution in three different land use types located at Wondo Genet district, southern Ethiopia. The results were interpreted by deploying both the carbon stratification ratio (CSR) and carbon flow balance ratio (CFBR) as ecological indicators. The results revealed that both the annual litterfall amount and associated organic carbon input in plantation forest (958.4 ± 112 g·m−2·yr−1; 391.4 ± 112 g·C·m−2·yr−1) were higher than those in the homegarden (183.5.4 ± 26 g·m−2·yr−1; 67.4 ± 10 g·C·m−2·yr−1), conceivably due to few litter contributors (trees) present in the homegarden. The CSR of the homegarden (1.3 ± 0.01) was found between the ratio obtained for crop (1.2 ± 0.01) and plantation forest (1.4 ± 0.01), indicating that it is definitely a combination of pure plantation forest and crop system. The CFBR was higher in plantation forest (3.4 yr−1) than in soil of homegarden (0.77 yr−1), implying the net accumulation of soil carbon over time in the latter system. Hence, homegardens could be considered as a system of climate-smart practice with multiple-biogeochemistry pathways, which simultaneously address the social-absolute needs. Given the current tendency of transforming homegarden agroforestry to monoculture types owing to economical drivers, such indicators can dictate of making rational decisions related to land use planning and soil fertility management.

Demystifying the modulation effects of the graphene transport layers on the interlayer charge transfer mechanism and broadband optical properties of MoS2/graphene/WSe2 Van der Waals heterojunctions

2D materials and heterojunctions have extraordinary potential in the field of next-generation integrated photodetectors. Recently, inserting graphene (Gra) into Van der Waals heterojunctions as transport layers has been proven to be an effective method for improving the responsivity and response speed of photodetectors. However, how did the physical mechanisms caused by the insertion (interlayer coupling and electron transfer) regulate its optical properties are unclear. Meanwhile, whether the insertion will modulate the broadband optical properties of the heterojunction should also be carefully verified. In this work, the broadband (1.25–6.50 eV) electronic band structures and exciton properties of MoS2/WSe2 and MoS2/Gra/WSe2 were studied using spectroscopic ellipsometry, meanwhile Raman and PL spectroscopy were used to assist in analysis. We found that graphene insertion not only promote the spontaneous charge transfer from WSe2 to MoS2, but also effectively inject electrons into the MoS2 layer, which benefits the interlayer charge separation and net charge accumulation in MoS2. Moreover, the almost stable CP energies near the band edge represent that graphene insertion does not change the electronic band structures of MoS2/WSe2. Furthermore, due to the increasing effective dielectric screening induced by graphene insertion, the exciton binding energies redshift and the exciton transition energy blueshift consequently.

Cadmium accumulation in soil resulting from application of biogas digestate and wood ash – Mass balance modelling

This study investigates the impact of substituting conventional NPK fertilizer with wood ash and biogas digestates at an agricultural field site in southwest Sweden. A three-year field experiment, comprising a crop rotation cycle of spring wheat, winter wheat, and oats, was conducted. The obtained results were employed to establish a dynamic mass balance model for the A horizon of the soil at the site. The Cd leaching term in the model was estimated using the Stockholm Humic model (SHM), which was recalibrated to accommodate low Cd concentrations by incorporating Cd complexation to thiol sites. The findings indicate that treatments receiving NPK fertilizer and biogas digestates experienced a net Cd loss, whereas treatments with wood ash demonstrated net Cd accumulation, attributed to its higher Cd content. Harvest yields were highest in the NPK treatment, and lower in two of the wood ash treatments, likely due to lower nitrogen additions in the latter. Cd offtake mirrored this trend, with the highest values in the NPK treatments and the lowest in the wood ash treatments, potentially also influenced by a pH difference of 0.2 units during the last year of the experiment. Geochemical modelling showed that Cd leaching is highly dependent on pH and that geochemically active soil Cd in the A horizon may have doubled between 1950 and 2002, due to elevated atmospheric deposition and fertilizer Cd during this period. Despite significant reductions in anthropogenic Cd fluxes since 2002, soil Cd has only decreased by 4%, showing the slow response of the soil pool to flux changes. Attaining a new steady-state after alterations in input fluxes will require hundreds of years. These results carry significance for determining sustainable application rates for recycled nutrient sources and underscore the crucial role of pH-dependent Cd sorption for Cd leaching.

Active recharge biphasic stimulation for the intraoperative monopolar review in deep brain stimulation.

Charge balancing is used in deep brain stimulation (DBS) to avoid net charge accumulation at the tissue-electrode interface that can result in neural damage. Charge balancing paradigms include passive recharge and active recharge. In passive recharge, each cathodic pulse is accompanied by a waiting period before the next stimulation, whereas active recharge uses energy to deliver symmetric anodic and cathodic stimulation pulses sequentially, producing a net zero charge. We sought to determine differences in stimulation induced side effect thresholds between active vs. passive recharge during the intraoperative monopolar review. Sixty-five consecutive patients undergoing DBS from 2021 to 2022 were retrospectively reviewed. Intraoperative monopolar review was performed with both active recharge and passive recharge for all included patients to determine side effect stimulation thresholds. Sixteen patients with 64 total DBS contacts met inclusion criteria for further analysis. Intraoperative monopolar review results were compared with the monopolar review from the first DBS programming visit. The mean intraoperative active recharge stimulation threshold was 4.1 mA, while the mean intraoperative passive recharge stimulation threshold was 3.9 mA, though this difference was not statistically significant on t-test (p = 0.442). Mean stimulation threshold at clinic follow-up was 3.2 mA. In Pearson correlation, intraoperative passive recharge thresholds had stronger correlation with follow-up stimulation thresholds (Pearson r = 0.5281, p < 0.001) than intraoperative active recharge (Pearson r = 0.340, p = 0.018), however the difference between these correlations was not statistically significant on Fisher Z correlation test (p = 0.294). The mean difference between intraoperative passive recharge stimulation threshold and follow-up stimulation threshold was 0.8 mA, while the mean difference between intraoperative active recharge threshold and follow-up threshold was 1.2 mA. This difference was not statistically significant on a t-test (p = 0.134). Both intraoperative active recharge and passive recharge stimulation were well-correlated with the monopolar review at the first programming visit. No statistically significant differences were observed suggesting that either passive or active recharge may be utilized intraoperatively.