Institute for Agro-Environmental Sciences, NARO, Kannondai 3-1-3, Tsukuba, Ibaraki, 305-8604, Japan.
Research Center for Advanced Analysis, NARO, Kannondai 3-1-3, Tsukuba, Ibaraki, 305-8604, Japan.
Sci Rep. 2023 Jan 5;13(1):217. doi: 10.1038/s41598-022-27325-1.
Application of organic amendments (OAMs) often enhances arsenic (As) dissolution in paddy soils. Therefore, understanding the properties of OAMs that determine the extent of As dissolution is essential for appropriate soil management. Since As dissolution increases with decrease in soil redox potential caused by microbial respiration, the decomposability of OAMs might be a critical factor controlling As dissolution in amended soils. We hypothesized that contents of acid detergent-soluble organic matter (ADSOM, mainly composed of non-fiber organic matter and hemicellulose) in OAMs can help estimate the potential of OAMs in accelerating As dissolution in soils with added OAMs. Therefore, two contrasting soil types, Andosol and Fluvisol, were mixed with 24 different OAMs and subjected to anaerobic incubation for 14 weeks. Changes in soil Eh and dissolved As contents were monitored throughout the incubation period, and As species in solid phases and ferrous iron (Fe(II)) contents in soils were measured after 2 and 6 weeks of incubation. The higher the ADSOM content in soils with OAMs, the higher the dissolved As contents in soils and the lower the Eh values. Dissolved As also positively correlated with the proportion of As(III) in solid phases and Fe(II) content after 2 and 6 weeks of incubation, indicating that decomposition of ADSOM led to reducing soil conditions, thereby promoting the reduction of As(V) and As-bearing Fe oxides and subsequent As dissolution. The results were consistent between the two types of soils, despite dissolved As content in the Andosol being two orders lower than that in Fluvisol. This is the first study to demonstrate that ADSOM can be a prominent indicator of the potential of OAMs, for promoting As dissolution, when applied to paddy soils.
有机添加物（OAMs）的应用通常会增强稻田土壤中砷（As）的溶解。因此，了解决定 As 溶解程度的 OAMs 的特性对于适当的土壤管理至关重要。由于 As 的溶解随着微生物呼吸引起的土壤氧化还原电位降低而增加，因此 OAMs 的可分解性可能是控制添加 OAMs 的土壤中 As 溶解的关键因素。我们假设 OAMs 中的酸洗涤剂可溶有机物（ADSOM，主要由非纤维有机物和半纤维素组成）含量可以帮助估计 OAMs 在加速添加 OAMs 的土壤中 As 溶解的潜力。因此，将两种对比土壤类型（安山土和冲积土）与 24 种不同的 OAMs 混合，并进行为期 14 周的厌氧培养。在整个培养期间监测土壤 Eh 和溶解 As 含量的变化，并在培养 2 和 6 周后测量固相中的 As 形态和土壤中的亚铁（Fe(II)）含量。OAMs 土壤中的 ADSOM 含量越高，土壤中溶解的 As 含量越高，Eh 值越低。溶解的 As 也与固相中 As(III)的比例和培养 2 和 6 周后的 Fe(II)含量呈正相关，表明 ADSOM 的分解导致土壤条件还原，从而促进 As(V)和含 As 的 Fe 氧化物的还原以及随后的 As 溶解。这两种类型的土壤结果一致，尽管安山土中的溶解 As 含量比冲积土低两个数量级。这是第一项表明 ADSOM 可以成为促进稻田土壤中 As 溶解的 OAMs 潜力的突出指标的研究。
