氮肥形态及用量对土壤砷生物有效性的影响研究

Influence of Application Amount and Category of Nitrogen Fertilizer on the Arsenic Bioavailability in Soil

通过盆栽试验,探讨了高砷红壤中施用碳酸氢铵、尿素和硝酸钙3种不同形态氮肥对土壤砷生物有效性及小白菜吸收砷的影响。结果表明:在175、350mg·kg-1两种施氮水平下,不同形态氮肥的施用均显著(P<0.05)促进了小白菜(Brassica chinensis)植株的生长,生物量的增加幅度为104.5%～224.3%;氮肥施用显著增加了土壤中有效态砷含量和植物对砷的吸收(P<0.05),与对照相比,不同形态氮肥处理下土壤有效态砷含量增加了30.5～49.4倍,其中,以施氮量为350mg·kg-1Ca(NO3)2处理增幅最大,NH4HCO3的350mg·kg-1施氮处理的增幅较小;在3种氮肥形态的2种施氮量处理下,植物地上部砷吸收量比对照增加0.75～4.32倍,且以175mg·kg-1NH4HCO3和350mg·kg-1Ca(NO3)2的施氮处理较高,而350mg·kg-1CO(NH2)2和175mg·kg-1Ca(NO3)2施氮处理的植物砷浓度及吸收量均相对较低。随着化学氮肥的施用,发生了土壤残渣态的砷向易溶态等其他形态砷的转化和释放,导致作物吸收砷及相应的环境风险增加。

Through pot experiment,the influence of nitrogen fertilizer application including NH4HCO3, CO（NH2）2 and Ca（NO3）2 on the availability of arsenic in red soils and arsenic uptake by Brassica chinensis was conducted. The results indicated that the plant biomass was significantly improved due to the application of these three kinds of nitrogen fertilizer at 175 mg N·kg^-1, 350 mg N·kg^-1 added level with the increased percentage of 104.5%-224.3% compared to control（CK） without N added. Under different N application treatments, the available arsenic in soils and plant accumulation of arsenic all increased significantly at P〈0.05 significant level. Under different N application treatments, the available amount of arsenic in soils was 30.5-49.4 times more than that of control, and the highest amount appeared in the 350 mg N·kg^-1 Ca（NO3）2 treatment, and the least amount occurred for the 350 mg·kg^-1 NH4HCO3 treatment. The uptake amount through the harvest crop was 0.75-4.32 times that of control. And the relatively high amount appeared in 175 mg N·kg^-1 NH4HCO3 and 350 mg N·kg^-1 Ca（NO3）2 treatments. The least arsenic concentration in plant and arsenic amount obtained from the harvested crop occurred for 350 mg N·kg^-1 CO（NH2）2 treatment and 175 mg N·kg^-1 Ca（NO3）2 treatment. With the application of these three kinds of nitrogen fertilizer, transformation from residual fraction into other four fractions like soluble arsenic and corresponding release of arsenic from soils was observed from this study, indicating the arsenic uptake amount by crops and environmental risk increased.