Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Interactions between lakes and groundwater are of increasing concern for freshwater environmental management but are often poorly characterized. Groundwater inflow to lakes, even at low rates, has proven to be a key in both lake nutrient balances and in determining lake vulnerability to pollution. Although difficult to measure using standard hydrometric methods, significant insight into groundwater–lake interactions has been acquired by studies applying geochemical tracers. However, the use of simple steady‐state, well‐mixed models, and the lack of characterization of lake spatiotemporal variability remain important sources of uncertainty, preventing the characterization of the entire lake hydrological cycle, particularly during ice‐covered periods. In this study, a small groundwater‐connected lake was monitored to determine the annual dynamics of the natural tracers, water stable isotopes and radon‐222, through the implementation of a comprehensive sampling strategy. A multilayer mass balance model was found outperform a well‐mixed, one‐layer model in terms of quantifying groundwater fluxes and their temporal evolution, as well as characterizing vertical differences. Water stable isotopes and radon‐222 were found to provide complementary information on the lake water budget. Radon‐222 has a short response time, and highlights rapid and transient increases in groundwater inflow, but requires a thorough characterization of groundwater radon‐222 activity. Water stable isotopes follow the hydrological cycle of the lake closely and highlight periods when the lake budget is dominated by evaporation versus groundwater inflow, but continuous monitoring of local meteorological parameters is required. Careful compilation of tracer evolution throughout the water column and over the entire year is also very informative. The developed models, which are suitable for detailed, site‐specific studies, allow the quantification of groundwater inflow and internal dynamics during both ice‐free and ice‐covered periods, providing an improved tool for understanding the annual water cycle of lakes.     

Experimental study on settling velocity of soil particles in dredged slurry

Studying sedimentation and consolidation of dredged slurry has significant implications to the design of storage yard and subsequent ground improvement. In this study, settling velocity of soil particles in dredged slurry during sedimentation and consolidation processes was investigated using an improved multilayer extraction sampling (MES) method. A series of sedimentation column tests were performed on dredged slurry with three different initial water contents. Distributions of volume of soil particles and density of dredged slurry were first obtained by the MES method, settling velocity of soil particles was then calculated by volume flux function approach. It was found that the density and velocity inflection points can be used to distinguish the settling zone and the consolidation zone. The experimental results reveal that the velocity of soil particles was quite low and monotonically decreased with sedimentation height at low initial water content throughout the whole test period, whereas it was increased at 0–1 hours and almost remained constant at 1–7 hours in the settling zone at high initial water content. The effects of initial water content on sedimentation and consolidation mode of dredged slurry and the settling velocity of soil particles were discussed. The relationship between settling velocity of soil particles and particle diameter was also studied. It is indicated that the measured velocity of soil particles was much lower than that calculated by the Stokes equation, and it was related to 0.4881–0.5906 order of particle diameter at 0–1 hours and 0.1117–0.1825 order of particle diameter at 1–7 hours for the test slurries.     

A multilayer study of pCO2 in the surface waters of the Yellow and South China Seas in spring and the sea-air carbon dioxide flux

A multilayer study of pCO₂ for the Yellow and South China Seas in the surface waters was conducted based on data from four cruises sponsored by the China SOLAS Project in 2005 and 2006, including data for the surface microlayer (SML), subsurface layer (SSL) and surface layer (SL). The carbon fluxes across the air-sea interface were calculated. The results showed that the pCO₂ values in the surface waters of the study area decreased in the following order: pCO_{2 SML} > pCO_{2 SSL} > pCO_{2 SL}. The highest values were found in March for all SML, SSL and SL, followed by those in April, and the lowest were in May. The pCO₂ values had a significant positive correlation with temperature or salinity. While there was no relationship between pCO₂ and longitude, there was a significant negative correlation between it and latitude, i.e., ‘high latitude low pCO₂’. By using four calculation models, the carbon dioxide fluxes ( ) in spring in the Yellow and South China Seas, which were found to act as a ‘sink’ of atmospheric CO₂, were preliminarily estimated on the basis of the pCO₂ data in the SML to be −7.00×10⁶t C and −22.35×10⁶t C, respectively. It is suggested that the calculated on the basis of pCO₂ data in the SML is more reliable than that calculated on the basis of those in the SL.     

大型垃圾处理设施周边居民污染感知影响因素及空间特征

近年来,随着中国大城市的快速发展,城市内部的大型垃圾处理设施与居住空间相交叠,影响居民生活品质.论文以北京市最大的垃圾处理中心——阿苏卫为研究对象,基于2019年8-10月获取的问卷数据,构建表征居民污染感知与污染源的空间距离、居民属性和居民主观认知3类因素关系的多层线性模型,以探索大城市邻避设施周边居民污染感知的影响...     

多层渗滤介质处理微污染水体的中试研究

对传统的渗滤系统进行改进,采用多层渗滤介质系统,以期增大人工土层对颗粒有机物的接触氧化表面积,同时设置曝气装置保证好氧过程的氧气供应,可以大大提高污水地下处理系统的水力负荷。以北京典型的细砂、中砂、粗砂和砾石为填充材料,处理北京市海淀区上庄水库的污染水体,远优于类似的系统。现场试验结果表明,改进后的系统能创造良好的好氧/厌氧环境,对污染物去除效果良好,COD_Cr、TN、NH⁺₄-N和TP去除率分别达到了48.57%~94.87%、18.49%~70.21%、20.51%~87.50%和5692%~80.65%,出水达到了地表水Ⅲ-Ⅳ类水质标准。多层渗滤介质系统通过微生物的硝化、反硝化作用实现生物脱氮是去除氮的主要途径;土壤的吸附与沉淀作用是去除磷的主要途径。      

陕西省洛川凤栖镇离石黄土下部层位渗透性研究

通过对洛川凤栖镇L₁₂～S₁₅土层8个层位16个实验点的入渗实验,研究了离石黄土下部层位的入渗特征。结果表明,洛川凤栖镇离石黄土下部层位黄土层的渗透系数较大,L₁₂,L₁₃,L₁₄和L₁₅这4个层位的平均值为0.90mm/分;  古土壤层的渗透系数较小,S₁₂,S₁₃,S₁₄和S₁₅的4个层位的平均值为0.35mm/分。L₁₂,L₁₃和L₁₅黄土层含水空间发育较好,利于构成含水层;  S₁₂,S₁₃,S₁₄和S₁₅古土壤层含水空间发育弱,利于构成隔水层。上覆总厚70余米的土层重力作用没有改变洛川离石黄土下部黄土层作为含水层和红色古土壤作为隔水层的基本特性,它们的水理性质仍是受沉积时的气候条件和成壤作用的强弱控制。古土壤层也具有一定的渗透性,这是黄土地下水常常具有多层性的原因,也是造成黄土地下水分散、含水层富水量少的主要原因。离石黄土下部黄土层含水空间发育好和利于构成含水层主要是当时冷干的气候决定的,红色古土壤含水空间发育弱和利于构成隔水层主要是当时温湿的气候决定的。将洛川黄土渗水实验数据用3种入渗公式分别进行拟合得出,常用的通用经验公式和考斯加科夫公式基本适用于描述洛川凤栖镇离石黄土下部层位的入渗规律,通过计算获得的2个经验公式各参数的均值和标准差为水文和农业部门应用黄土入渗经验公式提供了重要参考值。研究还揭示,第四纪环境变化理论研究在黄土水资源开发利用方面有重要应用价值。可以根据黄土与古土壤的成壤强弱判别地下水富集规律和富集层位。成壤强、隔水性好的古土壤层和其上的成壤作用很弱、含水空间发育好的黄土层是很好的地下水含水组合,最利于地下水的富集;  成壤作用弱、隔水性差的古土壤和其上厚度小、受风化成壤作用相对较强的黄土层是较差的含水组合,不利于地下水的富集。     

Surface load dynamic solution of saturated transversely isotropic multilayer half-space

This paper treats the dynamic response of a multilayered transversely isotropic fluid saturated poroelastic half-space under surface time-harmonic traction. The governing system of partial differential equations is uncoupled with the use of a set of physically meaningful and complete potential functions that decompose different body waves in a saturated poroelastic transversely isotropic medium. After expressing the equations in the Hankel-Fourier domain, a proper algebraic factorization is applied to generate reflection and transmission matrices for decomposed waves. All responses including displacements, stresses, and pore fluid pressure for both general patch load and point load are presented in the form of semi-infinite line integrals. The verification of the method is confirmed with the degeneration of the solutions presented here to the existing solutions for dried both homogeneous and multilayered elastic half-spaces as well as poroelastic half-space. Selected numerical results are depicted to investigate the effects of layering and pore pressure on responses of a transversely isotropic poroelastic medium. The load distribution effects are studied by comparison of the patch and point load responses. Also, resonance notion and effective parameters on this phenomenon such as layering system and anisotropy contrast are discussed. Significant influence of materials and layering configuration on number and amplitude of resonances depicted through the numerical evaluation.     

钾铵基聚合物泥浆在大同煤田复杂地层钻进中的应用

煤田地质钻探中,白垩系卵石层、多层采空区及泥岩地层是一大钻进难题。一是上部长孔段砂卵层胶结松散,易垮塌;二是下部泥岩水敏性强,膨胀性大,节理裂隙发育,极易产生缩径、造浆及不同程度的渗漏;三是多层采空区的护壁问题。针对这些问题,在大同煤田复杂地层钻进中,经反复实验选用了钾铵基聚合物低固相泥浆。实践证明,采用钾铵基聚合物低固相泥浆,可有效防止孔内坍塌、掉块、缩径,预防孔内事故,提高钻进效率,降低成本,达到了正常的钻进目的。