土壤溶解性有机物的动态变化对水溶态铜的影响

Effects of Dynamic Change of Dissolved Organic Matter in Soil on Water-Soluble Copper

目前中国部分地区土壤铜污染严重,耕地点位超标率高达2.1%。重金属毒性及生物有效性由其形态决定,而并非其总量决定。水溶态铜含量活性最高,最容易被植物吸收利用,因而受到广泛关注。秸秆常用于土壤重金属污染原位钝化修复中。秸秆还田后会产生溶解性有机物,这部分周转最快、活性最高的土壤有机质对土壤中水溶态铜含量有重要影响。基于此,本研究选取中国3种地带性土壤(红壤、褐土和黑土),设计添加铜和秸秆的土壤培养试验,温室培养12个月,每4个月取样一次。测定土壤中水溶态铜、溶解性有机碳(DOC)、氮(DON)和溶解性有机物的紫外光谱特性。研究结果表明,(1)红壤、褐土及黑土的秸秆处理中DOC含量较对照显著增加292%—567%,107%—202%,114%—141%。培养后8个月,3种土壤中DON含量较对照显著下降。其中,红壤、褐土及黑土中DON含量下降的幅度分别为88%—90%,47%—93%,62%—88%。在培养的第8—12个月,红壤和褐土的秸秆处理中DON含量较对照分别显著增加28%,22%,说明微生物在激发效应过程中优先利用溶解性有机氮。(2)秸秆处理中溶解性有机物芳香环上取代基种类增加,芳香性增强,分子量增加;随时间推移,3种土壤中溶解性有机物的芳香性及分子量随时间逐渐下降。(3)由于溶解性有机物对铜离子的络合作用,有机物加入后3种土壤中水溶态铜含量较对照显著增加;多元线性逐步回归分析结果表明:在3种土壤中,DOC含量与水溶态铜含量呈显著正相关。该研究表明,相比于溶解性有机物的紫外光谱性质,溶解性有机物的含量对水溶态铜含量的影响更大。

At present,China's soil copper pollution is serious,and the over-standard rate of cultivated land is as high as 2.1%.The toxicity and bioavailability of heavy metals are determined by their chemical forms,but not by their total quantity.Water-soluble copper has the highest activity and is easily absorbed and utilized by plants,which is highly regarded.Straw is often used in in-situ remediation of soil heavy metal pollution.Straw returned to the field will produce dissolved organic matter,the quickest turnover of soil organic matter,the highest activity of soil has an important effect on the content of water-soluble copper in the soil.Based on this,three kinds of zonal soils(red soil,cinnamon soil and black soil)in China were selected in this study,and the soil culture experiment adding with copper and straw were incubated in greenhouse for 12 months.Soil samples were collected every 4 months.The UV spectra of dissolved organic matter,dissolved organic carbon(DOC),nitrogen(DON),and water-soluble copper in soil were determined.The results showed that:(1)Compared with the control,the content of DOC in the rice straw treatment of red soil,cinnamon soil and black soil was significantly increased by 292%‒567%,107%‒202%and 114%‒141%,respectively.After eight months of incubation,the content of DON in the three soils was significantly lower than that of the control.The content of DON in red soil,cinnamon soil and black soil decreased by 88%‒90%,47%‒93%and 62%‒88%,respectively.During the 8‒12 months of incubation,the DON content in the red soil and cinnamon soil was significantly increased by 28%and 22%compared with the control,respectively,indicating that the dissolved organic nitrogen was preferentially used by microorganisms in the process of priming effect.(2)The types of substituents on the aromatic ring of soluble organic compounds increased,and their aromaticity increased and their molecular weight increased during straw treatment;The aromaticity and molecular weight of dissolved organic compounds in the three soils decreased with time.(3)The content of water-soluble copper in the three soils after the addition of rices straw was significantly higher than that of the control,due to the complexing effect of dissolved organic matter on copper ions;The results of multiple linear step-wise regression analysis indicated that there was a significant positive correlation between DOC content and water-soluble copper content in the three soils.This study demonstrated that the content of dissolved organic matter has a greater effect on the content of water-soluble copper than the UV spectrum properties of dissolved organic matter.