seasonality

季节性
  • 文章类型: Journal Article
    肠道菌群在调节能量代谢中起着至关重要的作用,促进营养吸收,并支持免疫功能,从而帮助宿主适应季节性饮食变化。这里,我们比较了野灰鼻猴在冬季(10月至12月)和春季(1月至3月)的肠道微生物组组成,以了解季节性营养素摄入模式的差异.鼻鼻猴是前肠发酵罐,消耗难以消化的碳水化合物和地衣。为了检查灰金丝猴的消化适应性,我们在冬季和春季收集了14份新鲜粪便样本进行DNA分析。基于16SrRNA测序,宏基因组测序,和功能宏基因组分析,我们确定了Firmicutes,放线菌,Verrucomicrobia,和拟杆菌在冬季和春季构成肠道微生物群中的关键细菌群,并负责降解纤维素。此外,从冬季到春季的膳食组成转变伴随着肠道微生物组成的变化,展示对不同食物来源和可用性的适应性反应。在冬天,发现链球菌属的细菌种类较高。在功能层面,这些细菌参与果糖和甘露糖代谢和半乳糖代谢相关途径,促进糖原的分解,淀粉,和水果中的纤维,种子,成熟的叶子在春天,普雷沃氏菌属和乳杆菌属的细菌种类越来越多,帮助消化富含蛋白质的芽。合并,这些发现揭示了肠道微生物群如何适应这种极度濒危物种不同季节能量平衡和营养摄入的波动。此外,我们还在两个样本中鉴定了假单胞菌;肠道内潜在病原体的存在可能对其他部队成员构成风险.我们的发现强调了保护计划的必要性,该计划的重点是保护植被并采取措施防止这种极度濒危物种的疾病传播。
    The gut microbiota plays a crucial role in regulating energy metabolism, facilitating nutrient absorption, and supporting immune function, thereby assisting the host in adapting to seasonal dietary changes. Here, we compare the gut microbiome composition of wild gray snub-nosed monkeys during winter (from October to December) and spring (from January to March) to understand differences in seasonal nutrient intake patterns. Snub-nosed monkeys are foregut fermenters and consume difficult-to-digest carbohydrates and lichen. To examine the digestive adaptations of gray snub-nosed monkeys, we collected 14 fresh fecal samples for DNA analysis during the winter and spring. Based on 16S rRNA sequencing, metagenomic sequencing, and functional metagenomic analyses, we identified that Firmicutes, Actinobacteria, Verrucomicrobia, and Bacteroidetes constitute a keystone bacterial group in the gut microbiota during winter and spring and are responsible for degrading cellulose. Moreover, the transition in dietary composition from winter to spring was accompanied by changes in gut microbiota composition, demonstrating adaptive responses to varying food sources and availability. In winter, the bacterial species of the genera Streptococcus were found in higher abundance. At the functional level, these bacteria are involved in fructose and mannose metabolism and galactose metabolism c-related pathways, which facilitate the breakdown of glycogen, starch, and fiber found in fruits, seeds, and mature leaves. During spring, there was an increased abundance of bacteria species from the Prevotella and Lactobacillus genera, which aid the digestion of protein-rich buds. Combined, these findings reveal how the gut microbiota adjusts to fluctuations in energy balance and nutrient intake across different seasons in this critically endangered species. Moreover, we also identified Pseudomonas in two samples; the presence of potential pathogens within the gut could pose a risk to other troop members. Our findings highlight the necessity of a conservation plan that focuses on protecting vegetation and implementing measures to prevent disease transmission for this critically endangered species.
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  • 文章类型: Journal Article
    背景:埃塞俄比亚政府制定了多部门霍乱消除计划(NCP),旨在降低霍乱发病率和病死率(CFR)。为了更好地了解和监控这个计划的进展,需要对国家霍乱流行病学进行全面审查.
    方法:从埃塞俄比亚公共卫生研究所和世界卫生组织数据库中提取了过去20年霍乱/急性水样腹泻(AWD)病例的报告数据。描述性统计,进行了Pearsonχ2和逻辑回归分析。
    结果:从2001年1月到2023年11月,共215205例霍乱/AWD病例,2355例死亡,累积CFR为1.10%(95%置信区间[CI],1.092-1.095),平均年发病率为8.9/100000(95%CI,6.5-11.3).在过去的二十年中,发现了两次霍乱流行的主要爆发,2006-2010年的平均发作率(AR)为20.57/100000,2016-2020年为14.83/100000。疫情的再次爆发发生在2021-2023年(平均AR,8.63/100000)。2015-2023年,54.0%(53990/99945)的病例年龄为15-44岁。国家霍乱CFR(3.13%[95%CI:2.1-4.5])是2022年最高的。2015-2023年累积霍乱CFR在各地区不同:BenishangulGumuz(6.07%),Gambela(1.89%),Sidama(1.42%),南方民族,国籍,和人民(1.34%),奥罗米亚(1.10%),和阿姆哈拉(1.09%)。老年人(≥45岁)的霍乱/AWD患者,严重脱水,雨季高峰(6月至8月),门诊患者的死亡风险较高。
    结论:霍乱一直是埃塞俄比亚的一个公共卫生问题,病例死亡人数仍高于全球目标。需要改善病例管理,特别是在门诊患者和老年人群中。疫情准备工作应在典型的雨季之前进行。重大投资对于在医疗保健环境和社区层面推进霍乱监测系统至关重要。应进一步调查每个地区霍乱死亡的潜在因素,以指导适当的干预措施,以在2028年前实现NCP目标。
    BACKGROUND: The Ethiopian government has developed the multisectoral cholera elimination plan (NCP) with an aim of reducing cholera incidence and case fatality rate (CFR). To better understand and monitor the progress of this plan, a comprehensive review of national cholera epidemiology is needed.
    METHODS: Reported data on cholera/acute watery diarrhea (AWD) cases in the past 20 years were extracted from the Ethiopian Public Health Institute and World Health Organization databases. Descriptive statistics, Pearson χ2, and logistic regression analyses were conducted.
    RESULTS: From January 2001 to November 2023, a total of 215 205 cholera/AWD cases, 2355 deaths with a cumulative CFR of 1.10% (95% confidence interval [CI], 1.092-1.095), and a mean annual incidence rate of 8.9/100 000 (95% CI, 6.5-11.3) were reported. Two major upsurges of cholera epidemics were found in the last two decades with mean attack rate (AR) of 20.57/100 000 in 2006-2010 and 14.83/100 000 in 2016-2020. Another resurgence of outbreaks occured in 2021-2023 (mean AR, 8.63/100 000). In 2015-2023, 54.0% (53 990/99 945) of cases were aged 15-44 years. National cholera CFR (3.13% [95% CI: 2.1-4.5]) was the highest in 2022. The 2015-2023 cumulative cholera CFR was different across regions: Benishangul Gumuz (6.07%), Gambela (1.89%), Sidama (1.42%), Southern Nation, Nationalities, and Peoples\' (1.34%), Oromia (1.10%), and Amhara (1.09%). Cholera/AWD patients in older adults (≥45 years), severe dehydration, peak rainy season (June-August), and outpatients were associated with higher risk of death.
    CONCLUSIONS: Cholera has been a public health problem in Ethiopia with case fatalities still above the global target. Case management needs to be improved particularly in outpatients and older populations. Outbreak preparedness should be rolled out well in advance of the typical rainy seasons. Significant investments are essential to advance the cholera surveillance system at healthcare setting and community level. Underlying factors of cholera deaths per areas should be further investigated to guide appropriate interventions to meet the NCP target by 2028.
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  • 文章类型: Journal Article
    虽然住宅环境的恢复性好处是众所周知的,居民的身体活动对他们在不同定居点的恢复性感知的影响尚不清楚。本研究旨在利用哈尔滨三个居民点的调查数据,调查居民身体活动和季节对恢复性知觉的中介和调节作用。中国,涉及2023年6月进行的基线调查,并在2023年7月至12月间隔30天进行问卷调查(534次访谈)。居民的恢复性感知和身体活动水平在秋季最高,沉降质量具有季节性调节作用,体力活动具有中介作用。
    While the restorative benefits of residential environments are known, the influence of residents\' physical activity on their perceptions of restorativeness in different settlements is unclear. This study aimed to investigate the mediating and moderating roles of residents\' physical activities and seasons on restorative perceptions using survey data from three settlements in Harbin, China, involving a baseline survey conducted in June 2023 and questionnaires administered at 30-day intervals from July to December 2023 (534 interviews). Residents\' restorative perceptions and physical activity levels were highest in autumn, with settlement quality having a seasonal moderating effect and physical activity having a mediating effect.
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  • 文章类型: Journal Article
    城市河流暴露于废水中越来越多的有机微污染物,对生态和公共卫生造成危害。一次性调查可以捕获污染概况的快照,但无法揭示时空异质性的全部规模。在本研究中,41种微污染物(非甾体抗炎药(NSAID),抗高血压药,抗癫痫药,抗糖尿病药,抗生素,碘化造影剂(ICM),缓蚀剂,农药)在多瑙河布达佩斯都市区的上游和下游每两周进行一次监测(总共336个样品)。ICMs,检测到苯并三唑和安乃近降解产物的最高浓度经常超过100ng/L其他药物的中值浓度范围为<1至26ng/L,而农药通常低于10ng/L微污染物浓度的变化主要是时间变化,表现出两种不同的模式:(1)与河流流量负相关,观察到缓蚀剂和卡马西平(r=-0.505至-0.665)或(2)与水温成反比,主要观察ICM,抗高血压药和抗生素,r=-0.654至-0.904)。校正河流流量后,温度依赖性也很高。在大都市地区之后,药品的相对增长率为2-134%,部分原因是根据零售数据和代谢率计算得出的排放估计值。5种ICM(碘帕醇100种,碘克沙醇96种,泛影酸盐22种,碘海醇21种,碘海醇13%)和两种NSAIDs(布洛芬和双氯芬酸(31.5%和23%的样品)的浓度超过了预测的无环境影响浓度,对藻类(HQ=1.2-6)和鱼类(HQ=1.4-1.9)构成风险,分别。结果表明,基于风险的监测和风险管理工作应侧重于ICM,NSAIDs和工业化学品,考虑到在寒冷时期和低流量期间的采样提供了最坏情况的估计。
    Urban rivers are exposed to an increasing load of organic micropollutants from wastewater effluent posing an ecological as well as public health hazard. One-off surveys can capture a snapshot of the pollution profile but fail to reveal the full scale of spatial and temporal heterogeneity. In the present study, 41 micropollutants (non-steroid anti-inflammatory drugs (NSAID), antihypertensives, antiepileptic, antidiabetic, antibiotics, iodinated contrast media (ICM), corrosion inhibitors, pesticides) were monitored every two weeks for one-year upstream and downstream of the Budapest metropolitan area in Danube River (336 samples total). ICMs, benzotriazoles and metamizole degradation products were detected in highest concentration regularly exceeding 100 ng/L. Median concentration of other pharmaceuticals ranged from <1 to 26 ng/L, while pesticides were typically below 10 ng/L. Variability of micropollutant concentration was primarily temporal, exhibiting two different patterns: (1) inverse correlation to river discharge, observed for corrosion inhibitors and carbamazepine (r = -0.505 to -0.665) or (2) inverse correlation to water temperature, observed primarily for ICMs, antihypertensives and antibiotics, r = -0.654 to -0.904). Temperature dependence was also significant after correcting for river discharge. Relative increase of pharmaceuticals was 2-134% after the metropolitan area, partially explained by emission estimates calculated from retail data and metabolization rates. The concentration of five ICMs (iopamidol in 100, iodixanol in 96, diatrizoate in 22, iomeprol in 21 and iohexol 13% of the samples) and two NSAIDs (ibuprofen and diclofenac (in 31.5 and 23% of the samples) exceeded the predicted no environmental effect concentration, posing a risk to algae (HQ = 1.2-6) and fish (HQ = 1.4-1.9), respectively. Results suggest that risk-based monitoring and risk management efforts should focus on ICMs, NSAIDs and industrial chemicals, taking into account that sampling in cold periods and during low flow provides the worst-case estimates.
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  • 文章类型: Journal Article
    BacilleCalmette-Guerin(BCG)疫苗是先天免疫记忆(也称为训练免疫)的公认诱导剂,在异源二次刺激时导致细胞因子产生增加。已知固有免疫反应受季节影响,但是季节是否会影响受过训练的免疫力的诱导尚不清楚。探讨季节对卡介苗诱导的天然免疫记忆的影响,我们在冬季或春季为健康志愿者接种卡介苗。三个月后,我们测量了离体细胞因子对异源刺激的反应,分析了免疫细胞的基因表达和表观遗传特征,并将这些与疫苗接种前的基线进行比较。在不同的细菌和真菌刺激刺激下,冬季BCG疫苗可诱导外周血单核细胞(PBMC)产生的促炎细胞因子增加。与春季接种卡介苗相比。相比之下,与春季卡介苗接种相比,冬季卡介苗接种导致PBMC中IFNγ释放较低。此外,在异源刺激下,冬季接种疫苗的人的NK细胞具有更大的促炎细胞因子和IFNγ生产能力。3个月后,BCG对单核细胞的转录组仅有较小的影响。相比之下,我们确定了疫苗接种诱导的单核细胞和NK细胞的季节依赖性表观遗传变化,部分解释了冬季卡介苗接种组较高的免疫细胞反应性。这些结果表明,冬季接种卡介苗更容易通过激活和重新编程免疫细胞来诱导强大的训练免疫反应。特别是NK细胞。(荷兰临床试验登记号NL58219.091.16)。
    The Bacille Calmette-Guerin (BCG) vaccine is a well-established inducer of innate immune memory (also termed trained immunity), causing increased cytokine production upon heterologous secondary stimulation. Innate immune responses are known to be influenced by season, but whether seasons impact induction of trained immunity is not known. To explore the influence of season on innate immune memory induced by the BCG vaccine, we vaccinated healthy volunteers with BCG either during winter or spring. Three months later, we measured the ex vivo cytokine responses against heterologous stimuli, analyzed gene expressions and epigenetic signatures of the immune cells, and compared these with the baseline before vaccination. BCG vaccination during winter induced a stronger increase in the production of pro-inflammatory cytokines by peripheral blood mononuclear cells (PBMCs) upon stimulation with different bacterial and fungal stimuli, compared to BCG vaccination in spring. In contrast, winter BCG vaccination resulted in lower IFNγ release in PBMCs compared to spring BCG vaccination. Furthermore, NK cells of the winter-vaccinated people had a greater pro-inflammatory cytokine and IFNγ production capacity upon heterologous stimulation. BCG had only minor effects on the transcriptome of monocytes 3 months later. In contrast, we identified season-dependent epigenetic changes in monocytes and NK cells induced by vaccination, partly explaining the higher immune cell reactivity in the winter BCG vaccination group. These results suggest that BCG vaccination during winter is more prone to induce a robust trained immunity response by activating and reprogramming the immune cells, especially NK cells. (Dutch clinical trial registry no. NL58219.091.16).
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  • 文章类型: Journal Article
    背景:疟疾是世界上最致命和最具挑战性的寄生虫病,由疟原虫寄生虫引起的,通过受感染的雌性蚊子的叮咬传播给人类。由于其地理位置,孟加拉国是最容易传播疟疾的地区。在本文中,我们考虑了向量-宿主模型的动力学,并观察了随机行为。本研究详细阐述了季节性变化,并计算了疾病爆发的概率。
    方法:我们提出了疟疾疾病传播模型,并开发了其相应的连续时间马尔可夫链(CTMC)表示。提出的矢量宿主模型说明了疟疾传播模型以及敏感性分析。描述了具有CTMC曲线的确定性模型,以显示真实场景中的随机性。按顺序,我们将这些研究扩展到包含季节性变化的时变随机向量-宿主模型。进行相平面分析以探索该疾病的特征,检查各个隔室之间的相互作用,并评估关键参数的影响。为相应的向量-宿主模型开发了分支过程近似,以计算爆发概率。为了观察分析研究,完成了许多数值结果。
    结果:季节性和接触模式影响疾病爆发的动态。数值说明提供了疾病爆发的概率取决于受感染的宿主或媒介。此外,周期性传播率对爆发概率有很大影响。导出基本再现数(R0),这是研究传染病模型动力学行为的主要依据。
    结论:季节变化显著影响疟疾传播,疾病爆发的可能性受时间和初始感染个体数量的影响。此外,当种群规模足够大且基本繁殖数小于1时,分支过程近似适用。在未来,这种分析可以帮助决策者了解各种参数的影响及其在载体-宿主模型中的随机行为,以防止此类疾病爆发。
    BACKGROUND: Malaria is the world\'s most fatal and challenging parasitic disease, caused by the Plasmodium parasite, which is transmitted to humans by the bites of infected female mosquitoes. Bangladesh is the most vulnerable region to spread malaria because of its geographic position. In this paper, we have considered the dynamics of vector-host models and observed the stochastic behavior. This study elaborates on the seasonal variability and calculates the probability of disease outbreaks.
    METHODS: We present a model for malaria disease transmission and develop its corresponding continuous-time Markov chain (CTMC) representation. The proposed vector-host models illustrate the malaria transmission model along with sensitivity analysis. The deterministic model with CTMC curves is depicted to show the randomness in real scenarios. Sequentially, we expand these studies to a time-varying stochastic vector-host model that incorporates seasonal variability. Phase plane analysis is conducted to explore the characteristics of the disease, examine interactions among various compartments, and evaluate the impact of key parameters. The branching process approximation is developed for the corresponding vector-host model to calculate the probability outbreak. Numerous numerical results are accomplished to observe the analytical investigation.
    RESULTS: Seasonality and contact patterns affect the dynamics of disease outbreaks. The numerical illustration provides that the probability of a disease outbreak depends on the infected host or vector. Additionally, periodic transmission rates have a great influence on the probability outbreak. The basic reproduction number (R0) is derived, which is the main justification for studying the dynamical behavior of epidemic models.
    CONCLUSIONS: Seasonal variability significantly impacts malaria transmission, and the probability of disease outbreaks is influenced by time and the initial number of infected individuals. Moreover, the branching process approximation is applicable when the population size is large enough and the basic reproduction number is less than 1. In the future, such analysis can help decision-makers understand the impact of various parameters and their stochastic behavior in the vector-host model to prevent such types of disease outbreaks.
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  • 文章类型: Journal Article
    全面了解砷(As)污染中湖泊的化学回收,需要考虑湖内As的生物地球化学循环以及周围流域发生的过程。本研究采用分水岭质量平衡方法,辅以实验性沉积物孵化,评估受60多年大气采矿排放影响的亚北极分水岭(155平方公里)内As的流动性和运输。这段记录跨越了2017年9月至2019年9月从干旱到高流量的过渡,从而深入了解了水文学和As的湖内生物地球化学循环的相互作用。受污染的湖泊沉积物中As的内部负荷(25-46kgAsyear-1)和陆地来源的贡献(16-56kgAsyr-1)继续对湖泊水质(19-144μgAsL-1)产生负面影响,但是这些负荷的相对重要性随水文条件的变化而季节性和年际变化。潮湿的条件导致陆相水库和上游地区的砷运输增加,较短的湖泊保水时间,并增加了As的下游出口。在干燥期间,湖泊与周围的分水岭断开,导致陆地贡献有限,湖水停留时间更长,由于受污染沉积物的内部负荷的相对影响更大,因此延迟了恢复。这项研究强调,不断变化的水文气候制度将通过湖内和流域运输过程的耦合来改变受砷影响的湖泊的化学回收轨迹。
    A holistic understanding of the chemical recovery of lakes from arsenic (As) pollution requires consideration of within-lake biogeochemical cycling of As and processes occurring in the surrounding catchment. This study used a watershed mass balance approach, complemented by experimental sediment incubations, to assess the mobility and transport of As within a subarctic watershed (155 km2) impacted by more than 60 years of atmospheric mining emissions. The period of record spanned a transition from drought to high streamflow between September 2017 and September 2019, which yielded insights into the interacting effects of hydrology and within-lake biogeochemical cycling of As. Internal loading of As from contaminated lake sediments (25 - 46 kg As year-1) and contributions from terrestrial sources (16 - 56 kg As yr-1) continue to negatively impact lake water quality (19 - 144 μg As L-1), but the relative importance of these loads varies seasonally and inter-annually in response to changing hydrological conditions. Wet conditions resulted in greater transport of As from terrestrial reservoirs and upstream areas, shorter lake water retention time, and increased the downstream export of As. During dry periods, the lake was disconnected from the surrounding watershed resulting in limited terrestrial contributions and longer lake water residence time, which delayed recovery due to the greater relative influence of internal loading from contaminated sediments. This study highlights that changing hydroclimatic regimes will alter trajectories of chemical recovery for arsenic impacted lakes through the coupling of within-lake and watershed transport processes.
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  • 文章类型: Journal Article
    由于对繁殖和躯体的能量投资不同,性二态物种中的雄性和雌性在生理和行为上表现出差异。这意味着男女在一年中的不同时间可能表现出不同的寄生模式。在这项研究中,我们评估了5种寄生虫类型的粪便卵和幼虫的丰度(Strongyles,线虫属。,MarshallagiaMarshalli.,原根菌属。肺虫,和艾美球虫。)与落基山大角羊(Oviscanadensis)的季节和性别有关。我们使用粪便卵数(FEC)作为感染强度的代表。雄性和雌性大角羊之间的寄生虫ECs不同,并且随季节而变化。我们发现,在不同的季节和生殖阶段,雄性和雌性中各种寄生虫的粪便卵数明显波动。在妊娠后期和哺乳期/夏季,粗体体计数显着升高,在男性中尤其明显。在雌性妊娠后期和雄性妊娠期间,线虫的数量最高。Marshallagia计数在雌性妊娠后期和雄性妊娠期间达到顶峰。原根菌属。在哺乳期/夏季和发情期间,雌性和雄性的妊娠后期,肺虫数量最高。艾美耳球虫卵囊计数随季节变化,在车辙期间雄性的计数较高,在冬季和妊娠后期,雌性的计数较高。此外,在奔跑和照料公羊之间观察到Strongyle计数的显着差异,饲养公羊的数量更高。我们讨论了为什么FECs的性别可能不同,并建议跨季节的寄生虫FECs之间的差异可能是由于不同的生命周期和寄生虫本身的耐寒性所致。
    Males and females in sexually dimorphic species show differences in their physiology and behaviour due to differences in energetic investment into reproduction and soma. This means that the two sexes may show different patterns of parasitism at different times of the year. In this study, we evaluate the abundance of fecal eggs and larvae of 5 parasite types (Strongyles, Nematodirus spp., Marshallagia marshalli., Protostrongylus spp. lungworms, and Eimeria spp.) in relation to season and sex in Rocky Mountain bighorn sheep (Ovis canadensis). We use fecal egg counts (FEC) as a proxy for infection intensity. Parasite FECs differed between male and female bighorn sheep and varied with season. We found pronounced fluctuations in fecal egg counts of various parasite species in males and females across different seasons and reproductive stages. Strongyle counts were significantly higher during late gestation and lactation/summer, and particularly pronounced in males. Nematodirus counts were highest during late gestation in females and during the rut in males. Marshallagia counts peaked during late gestation in females and during the rut in males. Protostrongylus spp. lungworm counts were highest during late gestation in females and in males during lactation/summer and the rut. Eimeria oocyst counts varied across seasons, with higher counts in males during the rut and in females during winter and late gestation. Additionally, significant differences in Strongyle counts were observed between coursing and tending rams, with tending rams exhibiting higher counts. We discuss why the sexes might differ in FECs and suggest that differences between FECs of the parasites across seasons may be due to different life cycles and cold tolerance of the parasites themselves.
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  • 文章类型: Journal Article
    地下水坝被认为是防止盐水入侵的最有效措施之一。然而,这可能会导致大量残留的盐水被困在大坝的上游,需要几年到几十年才能清除,这可能会限制沿海地区新鲜地下水的利用。在这项研究中,现场尺度数值模拟被用来研究从典型的分层含水层中去除残余盐水的机制,在两个高渗透层之间存在中间低渗透层(LPL),在季节性海平面波动的影响下。该研究量化并比较了恒定海平面(CSL)和季节性变化海平面(FSL)情景下残留盐水去除(Tre)的时间。建模结果表明,在大多数情况下,与静态海平面情况相比,海平面的季节性波动有助于稀释残留盐水,从而加速残留盐水的去除。然而,考虑季节性海平面变化可能会增加所需的临界大坝高度(实现完全去除残余盐水所需的最小大坝高度)。敏感性分析表明,在CSL或海平面波动较弱的情况下,Tre随着地下坝(Hd)高度的增加而减小;但是,当海平面波动的幅度很大时,Tre随Hd非单调变化。对于CSL和FSL方案,Tre都随着地下坝与海洋之间距离的增加而减小。我们还发现分层模型对Tre有显著影响。CSL和FSL情况下LPL厚度的增加导致Tre和临界大坝高度的减少。随着LPL高度的增加,Tre通常显示出非单调下降的趋势。这些定量分析为复杂情况下地下水坝的设计提供了宝贵的见解。
    Subsurface dams have been recognized as one of the most effective measures for preventing saltwater intrusion. However, it may result in large amounts of residual saltwater being trapped upstream of the dam and take years to decades to remove, which may limit the utilization of fresh groundwater in coastal areas. In this study, field-scale numerical simulations were used to investigate the mechanisms of residual saltwater removal from a typical stratified aquifer, where an intermediate low-permeability layer (LPL) exists between two high-permeability layers, under the effect of seasonal sea level fluctuations. The study quantifies and compares the time of residual saltwater removal (Tre) for constant sea level (CSL) and seasonally varying sea level (FSL) scenarios. The modelling results indicate that, in most cases, seasonal fluctuations in sea level facilitate the dilution of residual saltwater and thus accelerate residual saltwater removal compared to a static sea level scenario. However, accounting for seasonal sea level variations may increase the required critical dam height (the minimum dam height required to achieve complete residual saltwater removal). Sensitivity analyses show that Tre decreases with increasing height of subsurface dam (Hd) under CSL or weaker sea level fluctuation scenarios; however, when the magnitude of sea level fluctuation is large, Tre changes non-monotonically with Hd. Tre decreases with increasing distance between subsurface dam and ocean for both CSL and FSL scenarios. We also found that stratification model had a significant effect on Tre. The increase in LPL thickness for both CSL and FSL scenarios leads to a decrease in Tre and critical dam height. Tre generally shows a non-monotonically decreasing trend as LPL elevation increases. These quantitative analyses provide valuable insights into the design of subsurface dams in complex situations.
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  • 文章类型: Editorial
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