地学前缘 ›› 2021, Vol. 28 ›› Issue (5): 79-89.DOI: 10.13745/j.esf.sf.2021.2.9

• 地下水污染成因机理 • 上一篇    下一篇

压力对淤泥中C-N-S-Fe-H2O体系的影响

彭子琪(), 马腾*(), 刘妍君, 陈娟, 邱文凯, 刘锐   

  1. 中国地质大学(武汉) 环境学院, 湖北 武汉, 430074
  • 收稿日期:2020-04-10 修回日期:2020-08-20 出版日期:2021-09-25 发布日期:2021-10-29
  • 通讯作者: 马腾
  • 作者简介:彭子琪(1997—),女,硕士研究生,水文地质学专业,主要从事低渗透介质水岩相互作用的研究工作。E-mail: pengziqi@cug.edu.cn
  • 基金资助:
    国家自然科学基金项目“淤泥演化为黏土隔水层过程中的水岩相互作用”(41630318)

Effect of pressure on C-N-S-Fe-H2O system in sil

PENG Ziqi(), MA Teng*(), LIU Yanjun, CHEN Juan, QIU Wenkai, LIU Rui   

  1. School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan 430074, China
  • Received:2020-04-10 Revised:2020-08-20 Online:2021-09-25 Published:2021-10-29
  • Contact: MA Teng

摘要:

C、N、S、Fe是地下水中控制氧化-还原反应的主要元素,淤泥是黏土的演化初期,淤泥演化为黏土过程中会影响含水层水量水质,可能会造成地下水污染;其中的水岩相互作用可以概化为C-N-S-Fe-H2O体系的相互作用。淤泥演化过程的实质是淤泥在压力的作用下孔隙度不断变小,逐渐固结成岩;淤泥内部不断发生生物地球化学反应,C-N-S-Fe-H2O体系驱动各种物质的形态结构不断发生改变,其中加压速率和加压模式会影响淤泥里的C、N、S、Fe重要组分固液相的转化。本研究运用自主研发设计的增压装置,探究在3种加压速率(0.04 MPa/12 h、0.04 MPa/24 h、0.04 MPa/36 h)和加压模式(0.040.02 MPa/12 h、0.04 MPa/12 h、0.040.06 MPa/12 h)的情况下,固体介质中C、N、S、Fe向孔隙水释放的规律。结果表明:(1)匀速加压速率越慢,加压初期溶解性有机碳(DOC)、 SO 4 2 -释放速率越快, NO 3 -和Fe2+浓度变化增大;DOC、 SO 4 2 - NO 3 -、Fe2+释放总量越多。(2)不同的加压模式,加速加压(0.040.06 MPa/12 h)下 NO 3 -、Fe2+的浓度波动较大;DOC、 NO 3 - SO 4 2 -和Fe2+的总释放量为加速加压(0.040.06 MPa/12 h)大于匀速加压(0.04 MPa/12 h)。(3)加压过程中,DOC和 SO 4 2 -呈显著正相关,改变加压速率会改变DOC, NO 3 - SO 4 2 -和Fe2+的相关性。本研究表明改变加压速率和加压模式会对DOC、 NO 3 - SO 4 2 -和Fe2+的释放速率、释放总量和C、N、S、Fe的转化造成影响,其本质为氧化-还原反应和水岩相互作用的强弱发生了变化;本研究为地质演化过程中压力导致的主要元素变化提供了新的认识,认识到了隔水层会影响含水层的水质和水量,为原生劣质地下水的成因和地下水污染防治提供了新思路。

关键词: 压力, 加压速率, 加压模式, 淤泥, C-N-S-Fe-H2O, 孔隙水

Abstract:

Carbon, N, S and Fe are the main elements controlling the redox reactions in groundwater. Silt is the initial form of clay, and its transformation into clay can affect the quantity and quality of groundwater aquifers. Groundwater pollution may happen during the transformation process, where the water-rock interaction can be generalized as the C-N-S-Fe-H2O interaction system. The essence of silt evolution is porosity reduction under pressure and gradual consolidation into rocks. Biogeochemical reactions take place in silt while the C-N-S-Fe-H2O interaction system drives constant changes in the substance forms. Pressurization rates and modes can affect the transformation of important components, such as C, N, S and Fe, between solid and liquid phase in silt. This experiment studies the release of C, N, S and Fe to pore water under three pressurization rates (0.04 MPa per 12 h, 24 h, 36 h) and three pressurization modes (decelerating, from 0.04 to 0.02 MPa/12 h; uniform, 0.04 MPa/12 h; accelerating, from 0.04 to 0.06 MPa/12 h), using self-developed pressurization device. The results show: (1) Slower uniform pressurization rate corresponds to faster DOC, SO 4 2 - release rate, more NO 3 -, Fe2+concentration change, and more DOC, SO 4 2 -, NO 3 -, Fe2+release. (2) NO 3 -, Fe2+ concentration fluctuation increases under accelerating pressurization, and the total DOC, SO 4 2 -, NO 3 -, Fe2+ release is greater during accelerating pressurization versus uniform pressurization. (3) During pressurization, DOC and SO 4 2 - concentrations are positively correlated, and pressurization rate change can change the DOC, NO 3 -, SO 4 2 -, Fe2+ correlations. It shows that changing the pressurization rates and modes can affect DOC, SO 4 2 -, NO 3 -, Fe2+ release rate/quantity as well as C, N, S, Fe transformation, that is, essentially changing the magnitudes of redox reaction and water-rock interaction. This experiment provides a new understanding of the main elemental changes caused by pressure in the process of geological evolution, and demonstrates the aquitards can affect water quality/quantity in aquifer. This study provides new insights into the cause of naturally inferior groundwater and prevention of groundwater pollution.

Key words: pressure, pressurization rate, pressurization mode, silt, C-N-S-Fe-H2O, pore water

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