Albéric Patrick, Vennink Aurélie, Cornu Sophie, Bourennane Hocine, Bruand Ary
Université d'Orléans, CNRS/INSU, Institut des Sciences de la Terre d'Orléans (ISTO), 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France.
Sci Total Environ. 2009 Oct 15;407(21):5719-25. doi: 10.1016/j.scitotenv.2009.07.005. Epub 2009 Aug 6.
While soil water composition has long been recognised as being related to soil type (characteristics of the horizons), the influence of structures resulting from agricultural activities (hedges, ditches, wheel ruts, etc) is still under discussion. This work was undertaken to show that a snapshot of spatial variability of the geochemical characteristics of soil water at the scale of a plot can improve our understanding of soil geochemistry in a farmland setting. We selected a 3 hectare hedged plot located on a hillside, limited by a stream and used as pasture where soils have developed in weathered gneiss. The water depth, electrical conductivity, major ions, temperature, pH, dissolved organic carbon (DOC) content, dissolved oxygen content, fluorescence, alkalinity, Fe(2+), Mn(2+), NO(2)(-), Fe(III) and F(-) contents were measured in 62 auger holes randomly drilled on the site. Four sectors were identified in order to describe the distribution of the main geochemical parameters. Electrical conductivity and some major ions, especially sulphate, had larger concentrations near hedges where oxic conditions prevailed. These features were attributed to the impact of the linear anthropogenic network on the circulation of subsurface soil waters and evapo-transpiration and represent sector I. Dissolved Mn was an indicator of well channelled runoff subsurfaces facilitating the circulation of more highly reducing water (sector III), while DOC probably marked areas drained less well, with a prolonged contact time between soil solutions and organic topsoil horizons (sector II). The presence of dissolved Mn and Fe(II) indicates bottomland anoxic conditions (sector IV). It is concluded that a survey of the chemical composition of soil water may be a direct approach to show the influence of permanent structures on current soil properties and dynamics.
虽然土壤水分组成长期以来一直被认为与土壤类型（土层特征）有关，但农业活动（树篱、沟渠、车辙等）所形成的结构的影响仍在讨论之中。开展这项工作是为了表明，在地块尺度上对土壤水分地球化学特征的空间变异性进行快照，可以增进我们对农田环境中土壤地球化学的理解。我们选择了一个位于山坡上、面积为3公顷、有树篱环绕、受一条溪流限制且用作牧场的地块，这里的土壤是在风化片麻岩中发育形成 的。在该地块上随机钻出的62个螺旋钻孔中，测量了水深、电导率、主要离子、温度、pH值、溶解有机碳（DOC）含量、溶解氧含量、荧光、碱度、Fe(2+)、Mn(2+)、NO(2)(-)、Fe(III)和F(-)的含量。为了描述主要地球化学参数的分布，确定了四个区域。电导率和一些主要离子，尤其是硫酸盐，在有氧条件占主导的树篱附近浓度较高。这些特征归因于线性人为网络对地下土壤水分循环和蒸发蒸腾的影响，代表区域I。溶解态锰是径流良好的地下通道的指标，有利于更多强还原水的循环（区域III）；而DOC可能标志着排水较差的区域，土壤溶液与有机表土层之间的接触时间较长（区域II）。溶解态锰和Fe(II)的存在表明是河漫滩缺氧条件（区域IV）。得出的结论是，对土壤水分化学成分的调查可能是一种直接的方法，用以显示永久性结构对当前土壤性质和动态的影响。
