Spatiotemporal variability

时空变异
  • 文章类型: Journal Article
    该研究表征了2020年12月至2021年11月之间温室气体(GHG)通量(CO2,CH4和N2O)的时空变化及其在印度喜马拉雅山麓亚热带湿地中的调节驱动因素。五个不同的栖息地(沼泽森林的M1草皮表面,M2-沼泽森林的平原表面,M3-带有小草的沼泽表面,M4-沼泽土地,拥有密集的大型植物,和具有稀疏植物的M5沼泽土地)进行了研究。我们进行了温室气体通量的原位测量,小气候(AT,ST,和SMC(v/v)),和土壤特性(pH,EC,N,P,K,和SOC)在所有栖息地类型中重复三次。在整个栖息地,CO2,CH4和N2O通量的范围分别为125至536mgm-2h-1,0.32至28.4mgm-2h-1和0.16至3.14mgm-2h-1。生境(M3和M5)表现出比其他生境更高的GHG通量。CH4通量遵循夏季>秋季>春季>冬季的层次结构。然而,CO2和N2O通量跟随夏季>春季>秋季>冬季。CO2通量主要受ST和SOC控制。然而,CH4和N2O通量主要受生境中ST和SMC(v/v)调节。在N2O通量的情况下,土壤P和EC在整个生境中也起着至关重要的作用。AT是控制整个栖息地所有温室气体通量的通用驱动器。结果强调,亚热带喜马拉雅湿地的长期温室气体通量监测对于准确预测近期的温室气体通量及其随气候变化而变化的性质已成为当务之急。
    The study characterized the temporal and spatial variability in greenhouse gas (GHG) fluxes (CO2, CH4, and N2O) between December 2020 and November 2021 and their regulating drivers in the subtropical wetland of the Indian Himalayan foothill. Five distinct habitats (M1-sloppy surface at swamp forest, M2-plain surface at swamp forest, M3-swamp surface with small grasses, M4-marshy land with dense macrophytes, and M5-marshy land with sparse macrophytes) were studied. We conducted in situ measurements of GHG fluxes, microclimate (AT, ST, and SMC(v/v)), and soil properties (pH, EC, N, P, K, and SOC) in triplicates in all the habitat types. Across the habitats, CO2, CH4, and N2O fluxes ranged from 125 to 536 mg m-2 h-1, 0.32 to 28.4 mg m-2 h-1, and 0.16 to 3.14 mg m-2 h-1, respectively. The habitats (M3 and M5) exhibited higher GHG fluxes than the others. The CH4 flux followed the summer > autumn > spring > winter hierarchy. However, CO2 and N2O fluxes followed the summer > spring > autumn > winter. CO2 fluxes were primarily governed by ST and SOC. However, CH4 and N2O fluxes were mainly regulated by ST and SMC(v/v) across the habitats. In the case of N2O fluxes, soil P and EC also played a crucial role across the habitats. AT was a universal driver controlling all GHG fluxes across the habitats. The results emphasize that long-term GHG flux monitoring in sub-tropical Himalayan Wetlands has become imperative to accurately predict the near-future GHG fluxes and their changing nature with the ongoing climate change.
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  • 文章类型: Journal Article
    尽管许多研究讨论了欧洲空气质量的影响,非常有限的研究集中在城市大气中PM10中环境微量元素(TE)的详细现象学上。这项研究汇编了来自7个国家的55个地点(瑞士,西班牙,法国,希腊,意大利,葡萄牙,英国),旨在阐明欧洲城市PM10中20个TE的现象学。监测点包括城市背景(UB,n=26),流量(TR,n=10),工业(IN,n=5),郊区背景(SUB,n=7),和农村背景(RB,n=7)类型。抽样活动使用标准化协议进行,以确保数据可比性。在每个国家,使用高容量空气采样器在固定时间内收集PM10样品。分析包括TEs的时空分布,以及每个站点的TE之间的关系。结果表明,20个TEs的年平均值为90±65ng/m3,TR和IN位点的浓度最高(分别为130±66和131±80ng/m3)。TEs浓度的季节性变化,受排放源和气象学的影响,显示所有监测点之间存在显著差异(p<0.05)。TE浓度的估算突出了非致癌和致癌金属之间的不同比率,锌(40±49纳克/立方米),钛(21±29ng/m3),和铜(23±35纳克/立方米)占优势的非致癌TEs,而Cr(5±7ng/m3),Ni(2±6ng/m3)在致癌者中突出。不同地点和不同季节的TE之间的相关性,与排放源和气象条件的差异一致。这项研究为泛欧城市氛围中的TEs提供了有价值的见解,为未来的环境保护政策提供全面的数据集。
    Although many studies have discussed the impact of Europe\'s air quality, very limited research focused on the detailed phenomenology of ambient trace elements (TEs) in PM10 in urban atmosphere. This study compiled long-term (2013-2022) measurements of speciation of ambient urban PM10 from 55 sites of 7 countries (Switzerland, Spain, France, Greece, Italy, Portugal, UK), aiming to elucidate the phenomenology of 20 TEs in PM10 in urban Europe. The monitoring sites comprised urban background (UB, n = 26), traffic (TR, n = 10), industrial (IN, n = 5), suburban background (SUB, n = 7), and rural background (RB, n = 7) types. The sampling campaigns were conducted using standardized protocols to ensure data comparability. In each country, PM10 samples were collected over a fixed period using high-volume air samplers. The analysis encompassed the spatio-temporal distribution of TEs, and relationships between TEs at each site. Results indicated an annual average for the sum of 20 TEs of 90 ± 65 ng/m3, with TR and IN sites exhibiting the highest concentrations (130 ± 66 and 131 ± 80 ng/m3, respectively). Seasonal variability in TEs concentrations, influenced by emission sources and meteorology, revealed significant differences (p < 0.05) across all monitoring sites. Estimation of TE concentrations highlighted distinct ratios between non-carcinogenic and carcinogenic metals, with Zn (40 ± 49 ng/m3), Ti (21 ± 29 ng/m3), and Cu (23 ± 35 ng/m3) dominating non-carcinogenic TEs, while Cr (5 ± 7 ng/m3), and Ni (2 ± 6 ng/m3) were prominent among carcinogenic ones. Correlations between TEs across diverse locations and seasons varied, in agreement with differences in emission sources and meteorological conditions. This study provides valuable insights into TEs in pan-European urban atmosphere, contributing to a comprehensive dataset for future environmental protection policies.
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  • 文章类型: Journal Article
    城市化,农业,气候变化影响湖泊水质和水葫芦生长。本研究考察了湖泊地表水温度的时空变化,浊度,塔纳湖的叶绿素a(Chl-a)及其与水葫芦生物量的关系。MODIS陆地/湖泊地表水温度(LSWT),前哨2MSI图像,并使用了原位水质数据。验证结果表明,MODISLSWT与现场实测水温(R=0.90)有很强的正相关关系。原位浊度和归一化差异浊度指数(NDTI)(R=0.92),和原位Chl-a和归一化差异叶绿素指数(NDCI)(R=0.84)。整个湖泊的LSWT趋势各不相同,随着东北地区趋势的增加,西北,西南地区和西部地区的下降趋势,南方,和中部地区(2001-2022年)。雨前空间平均LSWT趋势显著下降(0.01℃/年),多雨(0.02℃/年),雨季和雨季后(0.01℃/年),而旱季(0.00℃/年)无显着增加(2001-2022年,P<0.05)。各季节空间平均浊度显著下降,除了雨季前(2016-2022年)。同样,雨前和雨季空间平均Chl-a显著下降,而在旱季和雨季后(2016-2022年),它表现出不显著的增加趋势。水葫芦生物量与LSWT(R=0.18)呈正相关,而与浊度(R=-0.33)和Chl-a(R=-0.35)呈负相关。在LSWT中观察到高时空变异性,浊度,Chl-a,随着整体下降趋势。研究结果提出了综合管理策略,以平衡水葫芦的根除及其在水净化中的作用。这些结果对于决策支持系统和制定可持续水资源管理战略计划至关重要,环境保护,和污染预防。
    Urbanization, agriculture, and climate change affect water quality and water hyacinth growth in lakes. This study examines the spatiotemporal variability of lake surface water temperature, turbidity, and chlorophyll-a (Chl-a) and their association with water hyacinth biomass in Lake Tana. MODIS Land/ Lake surface water temperature (LSWT), Sentinel 2 MSI Imagery, and in-situ water quality data were used. Validation results revealed strong positive correlations between MODIS LSWT and on-site measured water temperature (R = 0.90), in-situ turbidity and normalized difference turbidity index (NDTI) (R = 0.92), and in-situ Chl-a and normalized difference chlorophyll index (NDCI) (R = 0.84). LSWT trends varied across the lake, with increasing trends in the northeastern, northwestern, and southwestern regions and decreasing trends in the western, southern, and central areas (2001-2022). The spatial average LSWT trend decreased significantly in pre-rainy (0.01 ℃/year), rainy (0.02 ℃/year), and post-rainy seasons (0.01℃/year) but increased non-significantly in the dry season (0.00 ℃/year) (2001-2022, P < 0.05). Spatial average turbidity decreased significantly in all seasons, except in the pre-rainy season (2016-2022). Likewise, spatial average Chl-a decreased significantly in pre-rainy and rainy seasons, whereas it showed a non-significant increasing trend in the dry and post-rainy seasons (2016-2022). Water hyacinth biomass was positively correlated with LSWT (R = 0.18) but negatively with turbidity (R = -0.33) and Chl-a (R = -0.35). High spatiotemporal variability was observed in LSWT, turbidity, and Chl-a, along with overall decreasing trends. The findings suggest integrated management strategies to balance water hyacinth eradication and its role in water purification. The results will be vital in decision support systems and preparing strategic plans for sustainable water resource management, environmental protection, and pollution prevention.
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  • 文章类型: Journal Article
    颞叶癫痫(TLE)是主要的成人局灶性癫痫综合征,以功能失调的内在脑动力学为特征。然而,这些患者癫痫发作的确切机制仍然难以捉摸.我们的研究包括116例TLE患者,而51例健康对照。采用微观状态分析,我们评估了TLE患者和健康对照者之间的大脑动态差异,以及耐药性癫痫(DRE)和药物敏感性癫痫(DSE)患者之间。我们基于微观状态构建了动态功能连接网络,并量化了它们的时空变异性。利用这些大脑网络特征,我们开发了机器学习模型来区分TLE患者和健康对照,以及DRE和DSE患者之间。与健康对照相比,TLE患者的时间动力学表现出明显的加速度,以及大脑网络的高度同步和不稳定。此外,DRE患者在微状态B的某些部分表现出明显较低的空间变异性,E和F动态功能连接网络,与DSE患者相比,DRE患者微状态E和G动态功能连接网络某些部分的时间变异性明显更高。基于这些时空度量的机器学习模型有效地将TLE患者与健康对照区分开,并将DRE与DSE患者区分开。在TLE患者中观察到的加速的微状态动力学和破坏的微状态序列反映了高度不稳定的内在脑动力学,潜在的潜在异常放电。此外,DRE患者大脑网络中高度同步和不稳定活动的存在意味着稳定的癫痫网络的建立,导致对抗癫痫药物的反应性差。基于时空度量的模型表现出稳健的预测性能,准确区分TLE患者与健康对照和DRE患者与DSE患者。
    Temporal lobe epilepsy (TLE) stands as the predominant adult focal epilepsy syndrome, characterized by dysfunctional intrinsic brain dynamics. However, the precise mechanisms underlying seizures in these patients remain elusive. Our study encompassed 116 TLE patients compared with 51 healthy controls. Employing microstate analysis, we assessed brain dynamic disparities between TLE patients and healthy controls, as well as between drug-resistant epilepsy (DRE) and drug-sensitive epilepsy (DSE) patients. We constructed dynamic functional connectivity networks based on microstates and quantified their spatial and temporal variability. Utilizing these brain network features, we developed machine learning models to discriminate between TLE patients and healthy controls, and between DRE and DSE patients. Temporal dynamics in TLE patients exhibited significant acceleration compared to healthy controls, along with heightened synchronization and instability in brain networks. Moreover, DRE patients displayed notably lower spatial variability in certain parts of microstate B, E and F dynamic functional connectivity networks, while temporal variability in certain parts of microstate E and G dynamic functional connectivity networks was markedly higher in DRE patients compared to DSE patients. The machine learning model based on these spatiotemporal metrics effectively differentiated TLE patients from healthy controls and discerned DRE from DSE patients. The accelerated microstate dynamics and disrupted microstate sequences observed in TLE patients mirror highly unstable intrinsic brain dynamics, potentially underlying abnormal discharges. Additionally, the presence of highly synchronized and unstable activities in brain networks of DRE patients signifies the establishment of stable epileptogenic networks, contributing to the poor responsiveness to antiseizure medications. The model based on spatiotemporal metrics demonstrated robust predictive performance, accurately distinguishing both TLE patients from healthy controls and DRE patients from DSE patients.
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  • 文章类型: Journal Article
    由采矿活动和矿井排水引起的地表和地下水的水质演变是全世界严重的公众关注。为探讨矿井排水对硫酸盐演化的影响,使用多同位素(δ34SSO4,δ18OSO4,δD,和δ18Owater)和正矩阵分解(PMF)模型。采矿前,侏罗纪含水层以石膏溶解为主,伴随着阳离子交换和细菌硫酸盐还原,潜水含水层和地表水以碳酸盐溶解为主。由于煤矿开采初期的矿井排水,潜水含水层中硫酸盐的显着增加。然而,与导致黄铁矿氧化造成硫酸盐污染的常见采矿活动相反,该矿区的矿井排水导致地下水流动加速,并增强了潜水和承压含水层之间的水力联系。由改变的地下水流动系统引起的稀释控制了硫酸盐的演变,导致所有含水层和地表水中硫酸盐不同程度的减少。随着侏罗纪含水层的水文地球化学特征向潜水含水层演变,在确定矿井水入侵源时,应考虑这一因素,以避免误判。该研究揭示了矿山排水引起的水文地球化学演化,这可能有利于矿区地下水资源的管理。
    The water quality evolution of surface and groundwater caused by mining activities and mine drainage is a grave public concern worldwide. To explore the effect of mine drainage on sulfate evolution, a multi-aquifer system in a typical coal mine in Northwest China was investigated using multi-isotopes (δ34SSO4, δ18OSO4, δD, and δ18Owater) and Positive Matrix Factorization (PMF) model. Before mining, the Jurassic aquifer was dominated by gypsum dissolution, accompanied by cation exchange and bacterial sulfate reduction, and the phreatic aquifers and surface water were dominated by carbonate dissolution. Significant increase in sulfate in phreatic aquifers due to mine drainage during the early stages of coal mining. However, in contrast to common mining activities that result in sulfate contamination from pyrite oxidation, mine drainage in this mining area resulted in accelerated groundwater flow and enhanced hydraulic connections between the phreatic and confined aquifers. Dilution caused by the altered groundwater flow system controlled the evolution of sulphate, leading to different degrees of sulfate decrease in all aquifers and surface water. As the hydrogeochemical characteristic of Jurassic aquifer evolved toward phreatic aquifer, this factor should be considered to avoid misjudgment in determining the source of mine water intrusion. The study reveals the hydrogeochemical evolution induced by mine drainage, which could benefit to the management of groundwater resources in mining areas.
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  • 文章类型: Journal Article
    揭示大型湖泊流域生态系统服务(ESs)的时空特征及其复杂的相互关系,可以促进各种ESs的科学管理措施的制定。以前的研究较少关注流域单元及其历史动态,生态系统服务(ES)驱动机制尚不清楚。这里,我们集中在湖南省-洞庭湖流域(中国第二大淡水湖)的主要覆盖区域,研究了七个典型ESs的时空特征及其相互作用,确定了生态系统服务束(ESB)的历史空间格局,并揭示了这些ES变化的社会生态驱动机制。结果表明:(1)流域内大部分ESs的空间分布保持稳定。食品生产(FP),产水量(WY),土壤保持(SC)和净初级生产力(NPP)随着时间的推移而提高,而氮保留(NR),栖息地质量(HQ)和户外娱乐(OR)下降;(2)在食物生产和大多数ESs之间观察到权衡,而除食品生产外,所有ESs之间的协同关系。随着时间的推移,粮食产量和水分产量之间的权衡关系显著增加,而水分产量与氮素滞留之间的协同关系显著下降;(3)确定了5个生态系统服务束。而土壤保持区向综合生态调节区的转变主要发生在2000-2020年,导致生态调节服务功能的增强;(4)自然条件如降水、地形和植被,以及国内生产总值(GDP)和人口等社会经济因素,是影响ESs的关键因素。这些驱动因素中的大多数之间的相互作用可以进一步阐明ES变化。我们的结果强调了在ESs的可持续管理中需要基于分水岭的评估和历史动态的观点。
    Uncovering the spatiotemporal features of ecosystem services (ESs) and their intricate interrelations in large lake basins can facilitate the development of scientific management measures for various ESs. Previous studies have focused less on watershed units and their historical dynamics, and the ecosystem service (ES) driving mechanisms remain unclear. Here, we focused on Hunan Province-the main coverage area of the Dongting Lake Basin (China\'s second largest freshwater lake), investigated the spatiotemporal characteristics of seven typical ESs and their interactions, identified the ecosystem service bundle (ESB) historical spatial patterns and revealed the socio-ecological driving mechanisms of these ES changes. Results showed that: (1) the spatial distribution of most ESs remained stable in the basin. Food production (FP), water yield (WY), soil conservation (SC) and net primary productivity (NPP) improved over time, whereas nitrogen retention (NR), habitat quality (HQ) and outdoor recreation (OR) declined; (2) tradeoffs were observed between food production and most ESs, whereas synergistic relationships between all ESs except food production. The tradeoff relationship between food production and water yield increased significantly over time, while the synergistic relationship between water yield and nitrogen retention decreased significantly; (3) five ecosystem service bundles were identified. And the transformation of soil conservation area into integrated ecological regulation area mainly occurred from 2000 to 2020, resulting in an increase in the function of ecological regulation services; (4) natural conditions such as precipitation, topography and vegetation, as well as socio-economic factors such as Gross Domestic Product (GDP) and population, were key factors affecting ESs. The interactions among most of these drivers can further elucidate the ES changes. Our results emphasize the need for a watershed-based assessment and a historical dynamic perspective in the sustainable management of ESs.
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  • 文章类型: Journal Article
    本研究调查了中国东山湾珊瑚栖息地浮游植物的时空分布,以及影响分布的关键因素,六月期间,August,和2022年12月。东山湾浮游植物丰度表现出相当大的时间变化,2022年6月达到峰值,此后逐渐下降,并在2022年12月达到最低点。在整个季节中,底层浮游植物的丰度始终超过表层。东山湾珊瑚生境浮游植物平均丰度低于非珊瑚生境区。张江的涨落和沿海上升流影响了浮游植物的多样性和群落结构。造成浮游植物群落结构时空变异的关键因素包括养分浓度和海水温度。营养素在影响各种浮游植物群体中起着关键作用。优势硅藻物种,如亚锡和亚锡,与氨氮呈正相关,海水盐度,珊瑚覆盖,以及目前珊瑚物种的数量。在冬天,calanussinicus与有害的藻华物种呈负相关。此外,发现在珊瑚栖息地和周围的公海中,电流,营养素,浮游动物可能在决定浮游植物群落结构的时空变异中起着至关重要的作用。
    This study investigated the spatiotemporal distribution of the phytoplankton in the coral habitat of Dongshan Bay (China), along with critical factors affecting the distribution, during June, August, and December 2022. Phytoplankton abundance in Dongshan Bay exhibited considerably temporal variation, peaking in June 2022, gradually decreasing thereafter, and reaching its lowest point in December 2022. The abundance of bottom-layer phytoplankton consistently exceeded that of the surface layer throughout all seasons. The average phytoplankton abundance in the coral habitat of Dongshan Bay was lower than that in non-coral habitat areas. Fluctuations in the Zhangjiang River and coastal upwelling influenced the diversity and community structure of the phytoplankton. Critical factors causing spatiotemporal variability in phytoplankton community structure included nutrient concentrations and seawater temperature. Nutrients played key roles in influencing various phytoplankton groups. Dominant diatom species, such as Thalassionema nitzschioides and Thalassiosira diporocyclus, were positively correlated with ammonia nitrogen, seawater salinity, coral cover, and the number of coral species present. In winter, Calanus sinicus exhibited a negative correlation with harmful algal bloom species. Additionally, it was found that both in the coral habitat and surrounding open sea, currents, nutrients, and zooplankton may play crucial roles in determining the spatiotemporal variability in the phytoplankton community structure.
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  • 文章类型: Journal Article
    气候避难所是物种可以在气候变化中持续存在的区域,几乎没有运动。与气候避难所相关的因素包括高度的空间异质性,因此,当前和未来的最佳气候之间只有很短的距离,以及缓冲时间变化的生物或非生物环境因素。然而,由于人为的环境均质化和环境缓冲的退化,这些类型的气候避难所可能正在减少。为了量化在气候变化下恢复类似避难所的环境条件以增加人口持久性的潜力,我们模拟了人口的能力,以跟踪他们的温度在空间和时间的不同水平的空间和时间的温度变化。为了确定物种性状如何影响恢复异质性的功效,我们探索了一系列物种扩散能力的值,耐热性,和繁殖力。我们发现,物种更有可能在具有较高空间异质性和较低环境随机性的环境中持续存在。当模拟增加先前同质化环境的空间异质性的管理行动时,物种更有可能在气候变化中持续存在,人口规模普遍较高,但温和的温度变化影响不大。对于扩散能力有限的物种,异质性恢复的好处最大。相比之下,分散时间较长但繁殖力较低的物种更有可能从环境随机性的减少中受益,而不是空间异质性的增加。我们的结果表明,除了诸如辅助迁移等保护策略外,将环境恢复到类似避难所的条件还可以在气候变化的影响下促进物种的持久性。走廊,加强保护。
    Climate refugia are areas where species can persist through climate change with little to no movement. Among the factors associated with climate refugia are high spatial heterogeneity, such that there is only a short distance between current and future optimal climates, as well as biotic or abiotic environmental factors that buffer against variability in time. However, these types of climate refugia may be declining due to anthropogenic homogenization of environments and degradation of environmental buffers. To quantify the potential for restoration of refugia-like environmental conditions to increase population persistence under climate change, we simulated a population\'s capacity to track their temperature over space and time given different levels of spatial and temporal variability in temperature. To determine how species traits affected the efficacy of restoring heterogeneity, we explored an array of values for species\' dispersal ability, thermal tolerance, and fecundity. We found that species were more likely to persist in environments with higher spatial heterogeneity and lower environmental stochasticity. When simulating a management action that increased the spatial heterogeneity of a previously homogenized environment, species were more likely to persist through climate change, and population sizes were generally higher, but there was little effect with mild temperature change. The benefits of heterogeneity restoration were greatest for species with limited dispersal ability. In contrast, species with longer dispersal but lower fecundity were more likely to benefit from a reduction in environmental stochasticity than an increase in spatial heterogeneity. Our results suggest that restoring environments to refugia-like conditions could promote species\' persistence under the influence of climate change in addition to conservation strategies such as assisted migration, corridors, and increased protection.
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  • 文章类型: Journal Article
    气候敏感的冰覆盖水库是甲烷(CH4)释放的关键组成部分。然而,在冰雪覆盖期间影响CH4动力学的机制研究甚少。为了研究气泡对CH4动力学的影响,我们在冰层覆盖的水库中进行了密集的野外和孵化实验(冰生长,稳定性,和融化期)在中国东北地区。我们发现,冰(625.9±2419.7nmolL-1)和底层水(1218.9±2678.9nmolL-1)中的平均溶解CH4浓度很高,使它们成为大气CH4源。河流带可见的气泡带(气泡区域)和冰中CH4浓度的垂直分布反映了捕获气泡的分布。气泡区域冰中CH4的平均浓度(1674.8±3926.8nmolL-1)比无气泡区域(53.7±9.2nmolL-1)高2个数量级。此外,大量CH4积聚在冰下的气泡区域。这些发现表明,气泡决定了CH4在冰中的储存和CH4在底层水中的积累。由于CH4气泡的截留和再溶解,冰的生长增加了CH4在冰和下面的水中的储存。然而,冰融化释放出积聚在冰和底层水中的CH4。现场和孵化实验的比较表明,水库的深水环境具有CH4埋藏效应。逐步回归分析表明,沉积物有机质含量较高,中值粒径,孔隙率增加了CH4气泡的产生和释放,在冰上捕获更多的CH4气泡。总的来说,这项研究提高了在冰雪覆盖期间对CH4动力学和CH4排放可预测性的机械理解。
    Climate-sensitive ice-covered reservoirs are critical components of methane (CH4) release. However, the mechanisms that influence CH4 dynamics during ice-covered periods remain poorly studied. To investigate the effects of bubbles on CH4 dynamics, we conducted intensive field and incubation experiments in an ice-covered reservoir (ice growth, stability, and melt period) in Northeast China. We found that the mean dissolved CH4 concentrations in the ice (625.9 ± 2419.7 nmol L-1) and underlying water (1218.9 ± 2678.9 nmol L-1) were high, making them atmosphere CH4 sources. The visible bubble bands (bubble area) in the riverine zone and the vertical profile of the CH4 concentration in the ice reflect the distribution of trapped bubbles. The mean CH4 concentration in the ice of the bubble area (1674.8 ± 3926.8 nmol L-1) was 2 orders of magnitude higher than that of no-bubble area (53.7 ± 9.2 nmol L-1). Moreover, a large amount of CH4 accumulated under the ice in the bubble area. These findings suggest that bubbles determine the CH4 storage in ice and CH4 accumulation in the underlying water. Ice growth increases CH4 storage in ice and the underlying water because of the entrapment and re-dissolution of CH4 bubbles. However, ice melting releases the CH4 accumulated in the ice and underlying water. A comparison of the field and incubation experiments indicated that the deep-water environment of the reservoir had a CH4 burial effect. Stepwise regression analysis revealed that higher sediment organic matter content, median particle size, and porosity increased the production and release of CH4 bubbles, trapping more CH4 bubbles in ice. Overall, this study improves the mechanistic understanding of CH4 dynamics and predictability of CH4 emissions during ice-covered periods.
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  • 文章类型: Journal Article
    石油开采可能对海洋生态系统造成不利影响,但是它对地表碳酸盐动力学的影响仍然未知。在低空气-海洋ΔpCO2的碳酸盐系统中,如南中国海(SCS),人类活动可能会影响pCO2的分布模式,并可能改变地表的CO2汇或源。本研究调查了两个油田的地表碳酸盐系统,即文昌油田和恩平油田,位于西北SCS(NWSCS)架子上。在恩平油田,尽管由于CaCO3沉淀可能消耗的总碱度(TA),表面pCO2略有增加,强大的生物生产使羽流水成为强大的二氧化碳汇。同样,生物过程主导了文昌油田pCO2的变异性,在其中心区域表现出高价值。在NWSCS中,在两次航行中都观察到了架子水的影响。而且,由于海面温度(SST)降低和CO2放气而引起的pCO2下降超过了通过增强垂直混合而引起的增加,导致pCO2从9月到10月在这个水团内减少。更重要的是,在有井和没有井的剖面沿线的站点,碳酸盐参数没有观察到明显的差异,在这项研究中观察到的参数值落在以前在nSCS货架上报告的范围内,具有相似的控制过程。因此,石油开采对碳酸盐动力学的影响可以忽略不计,油田碳酸盐岩系统的特征主要受羽流水和盆地水混合等自然过程的支配,CaCO3沉淀和SST的变化。提供的数据为检测油田内碳酸盐化学的未来变化建立了至关重要的基线。海面pCO2的快速波动凸显了对更高时空分辨率观测的需求。
    Oil exploitation may pose adverse effects on marine ecosystems, but its impacts on surface carbonate dynamics remain unknown. In a carbonate system with low air-sea ∆pCO2, such as the South China Sea (SCS), human activities may affect the pCO2 distribution patterns and potentially alter CO2 sink or source at the surface. This study investigates the surface carbonate system in two oil fields, namely the Wenchang Oil Feld and Enping Oil Feld, located on the northwestern SCS (NWSCS) shelf. In Enping Oil Field, although there is a slight increase in surface pCO2 due to probable total alkalinity (TA) consumption from CaCO3 precipitation, strong biological production makes the plume water a strong CO2 sink. Similarly, the biological processes dominated the pCO2 variability in Wenchang Oil Feld, exhibiting high values in its central area. In NWSCS, the influence of shelf water was observed during both cruises. And the pCO2 drawdown caused by the decreased sea surface temperature (SST) and CO2 outgassing outweighed their increases via enhanced vertical mixing, leading to a pCO2 drawdown from September to October within this water mass. More importantly, there were no significant disparities observed in carbonate parameters at stations along transects with and without wells, and the observed parameter values in this study fell within the range reported previously on the nSCS shelf with similar controlling processes. Thus the impact of oil exploitation on carbonate dynamics is negligible, and the characteristics of the carbonate system in oil field are primarily governed by natural processes such as the mixing of plume water and basin water, CaCO3 precipitation and the changes in SST. The provided data establish a crucial baseline for detecting future alterations in carbonate chemistry within oil fields, and the rapid fluctuations in sea surface pCO2 highlight the need for higher spatiotemporal resolution observation.
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