澧阳平原古水稻土铁形态演变特征

采用野外采样与室内分析的方法,研究了澧阳平原杉龙岗遗址埋藏古水稻土与现代耕作水稻土铁形态、含量变化及剖面演变特征,探讨了土壤铁形态变化与成土过程的关系。结果表明:澧阳平原现代耕作水稻土与埋藏古水稻土铁形态及含量分别为:全铁31.61~35.10 g/kg和33.97~46.88 g/kg,游离铁8.88~13.92 g/kg和11.10~20.36 g/kg,无定型铁2.52~4.06 g/kg和2.64~3.35 g/kg,结晶态铁5.06~11.40 g/kg和8.46~17.43 g/kg。澧阳平原水稻土各形态铁含量除无定型铁外,其他形态铁含量总趋势为埋藏古水稻土现代耕作水稻土,且古水稻土各形态铁分异明显。现代耕作水稻土全铁、游离铁、结晶铁含量均呈现随深度加深而增加趋势,而无定型铁则相反,且各形态铁含量波动性较小;埋藏古水稻土全铁含量随土层增深而增加,无定型铁含量呈现微幅增加趋势,但游离铁和结晶铁含量变化有异,PA剖面减少,PC剖面增加,埋藏古水稻土中各形态铁含量变化趋势多样。澧阳平原古水稻土的铁有明显的淋溶淀积特征,不同形态铁在各土层变异较大,埋藏古水稻土铁富集明显。

Evolution of Iron Forms in Ancient Paddy Soils in Liyang Plain

The field sampling and laboratory analysis were conducted to study the content changes of iron Forms and their profile variations in current paddy soils and ancient paddy soils at Sanlonggang village of Liyang plain. The relationship between the changes of iron forms and soil forming process was analyzed. The results showed that the contents of different iron forms in current and ancient paddy soils in Liyang plain are: total iron was by 31.61-35.10 g/kg and 33.97-46.88 g/kg; free iron 8.88-13.92g/kg and 11.10-20.36g/kg; amorphous iron 2.52-4.06g/kg and 2.64-3.35g/kg; Crystal iron5.06-11.40g/kg and 8.46-17.43g/kg, respectively. Apart from amorphous iron, the iron concentration changed dramatically with the trend of ancient paddy soils > current paddy soils in Liyang plain soils, and the obvious variation of the different form Fe was observed in ancient paddy soils. The content of total iron, free iron, crystal iron increase with increasing depth, but the opposite trend of amorphous iron was found, while a little difference of content was recorded in the different Fe forms in the current paddy soils. The content of total Fe heightened, and the light increase trend of content was observed in amorphous iron with increasing soil depth, but the content variety of free iron, crystal iron was instability, the decrease trend was noted, inverse change in PC in the ancient paddy soils. The change mode of the different Fe forms was diversiform the ancient paddy soils And the characterized by the content of iron forms trend is that volatility were reduced in modern farming paddy soil. The characteristics of elevation and deposition were examined obviously, and the greater distribution variation of different form Fe was observed and the the relative enrichment of Fe characterized obviously in the ancient paddy soil at Sanlonggang village.