影响或控制土壤形成（方向和强度）的环境因素。包括自然成土因素和人为成土因素。前者包括气候、生物、母质、地形、水文和时间（年龄）；后者指人类的耕垦、施肥和灌溉等活动。
本文讨论了影响北京土壤元素背景值的成土因素，主要有成土母质、生物气候、地貌、时间和人为因素。
The factors of soil formation affecting soil background contents of elements in Beijing area are mainly discussed in this paper.
根据自然成土因素和在人为作用影响下的土壤熟化程度，将该小流域的黄绵土进一步划分为四种土壤类型。
According to the natural factors of soil formation and the development, degree of soil, under the influence of human production activity, the Huangmian soils were devided into four types.
分析结果表明，影响土壤元素背景值的主要因素，在平原地区是地貌条件，在山区是成土母质。
The results showed that the principal factors affecting the metal background contents were landforms for plain area and soil parent material for mountain area.
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