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Sulfurization, acid-sulfate soils and active layer monitoring at the semiarid Seymour Island, Antarctica
Geoderma Regional ( IF 4.1 ) Pub Date : 2020-07-03 , DOI: 10.1016/j.geodrs.2020.e00305
Davi Feital Gjorup , Carlos Ernesto G.R. Schaefer , Felipe Nogueira Bello Simas , Marcio Rocha Francelino , Roberto Ferreira Machado Michel , James G. Bockheim

Soils and permafrost occurrence and behavior at the Weddell Sea zone, located in the key zone of climatic transition between Maritime Antarctica and Continental Antarctica, remain little studied. We studied the main chemical, physical and mineralogical properties of representative soil profiles of the northern part of Seymour Island, discussing soil formation processes and the active-layer thermal and water regimes of a representative site. Soil sampling and installation of the monitoring site was carried out in the northern part of Seymour Island. Permafrost was generally detected within the first 100 cm of depth, except at coastal areas, although typical periglacial features (cryoturbation), vegetation growth and organic matter accumulation were negligible or absent. Well-drained soils showed low Electric Conductivity (EC), indicating leaching of salts, whereas near-permafrost layers showed higher values of EC. Salt content and EC increased at lower altitudes. Two major groups of soils were identified: (i) Acid Sulfate Soils (ASS); and (ii) Weakly Developed Alkaline Soils (WDAS). Acid Sulfate Soils develop under the influence of sulfide-containing material under oxidizing conditions, and are the most developed and weathered in the area, presenting significant morphological, mineralogical and chemical traits, such as low pH values, sulfuric B horizons, and the presence of secondary minerals indicating sulfurization process, such as jarosite and low crystallinity iron oxide. Weakly Developed Alkaline Soils develop under low chemical and mineralogical transformation, where physical weathering is a key process. These soils present high pH and high content of primary minerals in the clay fraction, mainly K-feldspars and plagioclase. The active-layer thermal regime is typical of periglacial environments, with seasonal temperature variations of soil around 0 °C, with prevailing negative temperatures. Regional climate was comparable with Continental Antarctica, whereas the pedoclimate (active layer thickness, soil water content) showed closer affinity with Maritime Antarctica. Some soil forming processes are driven by pedoclimate, and favored by the unfrozen and free-drainage conditions during the summer season; however, the main factor influencing soil development is parent material. The main soil formation processes are sulfurization, cryoclasty and halomorphism, since the semiarid dry climate does not favor cryoturbation and organic matter accumulation.



中文翻译:

南极半干旱西摩岛的硫化,酸性硫酸盐土壤和活性层监测

位于海洋南极洲和南极大陆之间气候过渡关键区域的韦德尔海地区的土壤和多年冻土的发生和行为,仍然很少研究。我们研究了西摩岛北部代表性土壤剖面的主要化学,物理和矿物学性质,讨论了代表性地点的土壤形成过程以及活性层的水热状况。在西摩岛北部进行了土壤采样和监测地点的安装。永久冻土通常在前100 cm的深度内检测到,但沿海地区除外,尽管典型的冰缘特征(冰冻扰动),植被生长和有机质积累可忽略不计。排水良好的土壤显示出低电导率(EC),表示盐分浸出,而近多年冻土层表现出较高的EC值。较低海拔下的盐含量和EC升高。确定了两大类土壤:(i)酸性硫酸盐土壤(ASS);(ii)弱碱土(WDAS)。酸性硫酸盐土壤是在氧化条件下在含硫化物的影响下发展的,是该地区最发达,风化最严重的土壤,具有明显的形态,矿物学和化学特性,例如低pH值,B族硫酸盐水平以及指示硫化过程的次生矿物,如黄铁矿和低结晶度的氧化铁。碱土开发较弱土壤的化学和矿物学转化率较低,而物理风化是关键过程。这些土壤在粘土级分中主要是钾长石和斜长石具有较高的pH值和较高的主要矿物质含量。活跃层的热态是冰缘环境的典型特征,土壤的季节性温度在0°C左右变化,主要是负温度。区域气候与南极洲大陆相当,而pedoclimate(活性层厚度,土壤含水量)显示出与南极海洋的亲近力。一些土壤的形成过程是受人为气候影响的,而夏季则不受冻结和自由排水的影响。但是,影响土壤发育的主要因素是母体物质。土壤的主要形成过程是硫化,冻裂和半同质性,因为半干旱的干燥气候不利于冷冻扰动和有机物质的积累。

更新日期:2020-07-03
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