三种有机物料组成性质及其对土壤Cd形态与水稻Cd含量的影响

为探讨有机物料对土壤Cd形态和水稻Cd含量的影响,于2017年5月至2017年9月在温室大棚进行水稻盆栽试验,在不同外源Cd浓度处理下,通过分析对照组(CK)及施加猪粪堆肥(PM)、腐殖土(HM)、污泥堆肥(CS)对水稻Cd含量的影响,探究有机物料活性组分差异与水稻Cd含量的关联性。结果表明:三种有机物料含氧官能团含量和极性大小顺序均为HMCSPM。施加三种有机物料都有利于缓解土壤Cd污染对水稻的生长毒害作用。外源Cd浓度为2 mg·kg~(-1)时,施用PM、HM和CS后的水稻籽粒Cd浓度较对照分别降低17.24%、32.41%和17.93%。且施用HM后,水稻籽粒Cd最高浓度为0.19 mg·kg~(-1),满足《食品安全国家标准食品中污染物限量》(GB 2762—2017)要求。而在外源Cd浓度达到10 mg·kg~(-1)时,仅施加PM可使水稻籽粒Cd浓度降低,但仍不能达到食品安全标准要求。水稻籽粒Cd含量与土壤可交换态Cd及铁锰氧化物结合态Cd含量呈显著正相关关系,与水稻根Cd含量呈极显著正相关,含氧官能团丰富、极性大的HM降低土壤可交换态镉含量效果最好。有机物料主要通过改变土壤Cd赋存形态,降低水稻根系对土壤Cd的吸收富集,抑制Cd向籽粒转运,进而影响Cd在水稻体内含量。

Composition and properties of three organic materials and their effects on soil Cd speciation and Cd content in rice

A pot experiment was conducted in a greenhouse from May 2017 to September 2017 to investigate the effects of organic materials on cadmium (Cd) fractionation in soil and Cd content in rice grains. For this experiment, bulk soil with a Cd content of 0.11 mg·kg^-1 and soils with Cd contents artificially adjusted to 2.12 and 10.12 mg·kg^-1 were supplemented with 2.5 g C·kg^-1(based on C content of the materials) of pig manure (PM), sludge compost (CS), and humus soil (HM), respectively. The Cd content in rice grains and the fractionation of Cd in soils were compared, and the effects of these organic materials were analyzed with respect to their properties. The main results were as follows:The polarities and contents of oxygen-containing functional groups in the organic material followed the order HM > CS > PM. The application of the three organic materials helped alleviate the toxic effect of soil Cd on rice growth. PM, HM, and CS reduced the Cd content in rice grains by 17.24%, 32.41%, and 17.93%, respectively at a soil Cd concentration of 2.12 mg·kg^-1. The maximum Cd content in rice grains was 0.19 mg·kg^-1 after HM application, which met the criteria of China National Food Safety Standard (GB 2762-2017). However, when the soil Cd concentration reached to 10 mg·kg^-1, only PM showed any Cd accumulation reduction effect in rice grains; at this concentration, the requirement of the food safety standard could not be met even with PM application. Significant positive correlations existed between the Cd content in rice grains and the contents of soil exchangeable Cd, Cd bound by Fe-Mn oxides, and Cd content in rice roots. This suggested that organic materials worked mainly by altering the soil Cd fractionation and by inhibiting soil Cd uptake by rice roots and its transfer to the grains. The organic substance that was rich in oxygen-containing functional groups and had high polarity showed better results in terms of the reduction in Cd accumulation in rice grains.