Abstract

Soil contamination by arsenic (As) is an important environmental issue globally. Intercropping of hyperaccumulators with main crop is typically applied for remediation of As-contaminated soil. Most hyperaccumulators are wild plants with small biomass and slow growth rates. Thus, remediation is slow. Here, we propose an effective intercropping system for remediation of As-contaminated paddy soil. Four treatments—intercropping with water spinach (Ipomoea aquatica Forsk) (T1), water celery (Oenanthe javanica (Blume) DC.) (T2), or Guangdong white arrowhead (Sagittaria sagittifolia L. var) (T3), with rice (Oryza sativa L.) monoculture (control, CK)—were used. Compared with the CK, grain yield per plant of rice under T1 and T2 increased by 58.13% and 10.48%, respectively, but decreased by 46.90% in T3. As concentration, bioaccumulation factor, and translocation factor in brown rice were significantly lower in the intercropping treatments than in CK. As removal by water spinach was 7.04 and 1.47 times that by water celery and arrowhead, respectively. The pH of paddy soil was significantly higher in all treatments than in CK, and iron plaque on rice roots under T1 and T2 decreased significantly but increased significantly under T3 compared with that of CK. Rice intercropped with water spinach had the best remediation effect.

Novelty Statement: We believe that the following highlights of this manuscript will make it interesting to general readers of this journal.

First, in recent years, many articles about intercropping system for the remediation of soil heavy metal pollution focus on dry land, and few studies have focused on paddy soil. The present study was on arsenic-contaminated paddy soil remediation.

Second, water spinach, water celery, and arrowhead have great potential for phytoremediation. Studies have shown that these three aquatic vegetables play a role in the removal of certain pollutants, such as heavy metals. Moreover, when intercropped with rice, they can effectively increase rice yield and reduce rice diseases and insect pests. However, studies on remediation of arsenic-contaminated soil by intercropping aquatic vegetables and rice have not been reported. We propose here a rice-aquatic vegetables (water spinach, water celery and arrowhead) intercropping pattern for remediation of arsenic in soil.

Third, according to the arsenic concentration and removal rate, we used a bioaccumulation factor, translocation factor, and arsenic removal per unit area of plants for the quantitative evaluation of the remediation effects of the intercropping systems. We found that the intercropping of rice and water spinach could be used to remediate arsenic-contaminated soil. Moreover, the extraction contents of arsenic using intercropping with water spinach was higher than that achieved in a previous study that applied intercropping with the arsenic hyperaccumulator Pteris vittata over the same growth time. This study provides a reference for realizing both remediation and increased production in arsenic-contaminated soil and for promoting sustainable development of agriculture.

摘要

全球砷污染土壤是一个重要的环境问题。超级作物与主要农作物间作通常用于修复砷污染的土壤。大多数超蓄积物是野生生物，生物量少，生长速度慢。因此，补救是缓慢的。在这里，我们提出了一种有效的套种系统来修复被As污染的稻田土壤。四种处理方法：将水菠菜（Ipomoea aquatica Forsk）（T1），水芹菜（Oenanthe javanica（Blume）DC。）（T2）或广东白箭头（Sagittaria sagittifolia L. var）（T3）套种，再加水稻（Oryza）苜蓿L.）单培养（对照，CK）—使用。与CK相比，T1和T2下水稻单株籽粒产量分别增加58.13％和10.48％，而T3下减少46.90％。间作中糙米的浓度，生物积累因子和转运因子均显着低于CK。菠菜的水分去除率分别是芹菜和箭头去除率的7.04倍和1.47倍。与CK相比，所有处理的稻田pH值均显着高于CK，T1和T2下水稻根部的铁斑明显减少，而T3下水稻根部的铁斑明显增加。间作水菠菜对水稻的修复效果最好。

新颖性声明：我们认为，该手稿的以下重点内容将使该杂志的普通读者感兴趣。

首先，近年来，有关用于修复土壤重金属污染的间作系统的许多文章都集中在旱地上，很少有研究集中在稻田上。本研究是关于砷污染的稻田土壤的修复。

其次，水菠菜，水芹菜和箭头具有很大的植物修复潜力。研究表明，这三种水生蔬菜在去除某些污染物（例如重金属）方面发挥着作用。而且，当与稻作间作时，它们可以有效地提高稻米产量，减少稻米病虫害。然而，关于通过套种水生蔬菜和水稻来修复砷污染土壤的研究尚未见报道。我们在此提出一种水稻水生蔬菜（菠菜，芹菜和箭头）间作模式，以修复土壤中的砷。

第三，根据砷的浓度和去除率，我们使用生物累积因子，转运因子和单位面积植物的砷去除量对间作系统的修复效果进行定量评估。我们发现水稻和菠菜间作可以用来修复砷污染的土壤。此外，水菠菜与间作套种对砷的提取含量高于以前的研究，该研究在相同的生长时间内与砷超富集者凤尾蕨进行间作。该研究为实现砷污染土壤的修复和增产并促进农业的可持续发展提供了参考。