Área de Edafología y Química Agrícola, Facultad de Ciencias - IACYS, Universidad de Extremadura, Badajoz, Spain.
Área de Producción Vegetal, Escuela de Ingenierías Agrarias - IACYS, Universidad de Extremadura, Badajoz, Spain.
Sci Total Environ. 2023 Aug 20;887:164012. doi: 10.1016/j.scitotenv.2023.164012. Epub 2023 May 10.
Arsenic, Cd, and Pb environmental fate is influenced when the traditional permanent flooding rice production systems are replaced by water-saving and soil conservation practices, urging for additional strategies that avoid their bioaccumulation in rice grain. The aim of this two-years field study was to evaluate the effects of fresh and field-aged biochar on As, Cd, and Pb bioaccumulation, and on As speciation, in rice grain produced in different growing environments (flooding versus sprinkler and conventional tillage versus direct seeding). Biochar produced from holm-oak pruning residues (pyrolysis at 550 °C, 48 h), in a single application (28 Mg ha), reduced As bioaccumulation in rice grain in the permanent flooding system to non-quantifiable concentrations (e.g., from 0.178 mg kg to <0.04 mg kg, for inorganic-As, respectively), an effect which remained under field-aging conditions, increasing rice commercial value. When adopting sprinkler irrigation, the undesirable increase in Cd bioaccumulation in rice, relatively to the anaerobic system, was counteracted by biochar application, reducing its bioaccumulation in kernels between 32 and 80 %, allowing a simultaneous control of metals and metalloids bioaccumulation in rice. The bioaccumulation of Pb was also prevented with biochar application, with a reduction in its concentration four- to 13-times, in all the management systems, relatively to the non-amended plots, under fresh biochar effects. However, Pb immobilization decreased with biochar field-aging, indicating that the biochar application may have to be repeated to maintain the same beneficial effect. Therefore, the present study shows that the implementation of sprinkler irrigation with holm-oak biochar could reduce the risk of heavy metals(loids) bioaccumulation in rice grains and, thereby, ensuring food safety aspects, particularly under fresh biochar effects.
砷、镉和铅的环境命运会受到影响，当传统的淹水水稻生产系统被节水和土壤保持实践取代时，这就需要采取额外的策略来避免它们在水稻中的生物累积。本为期两年的田间研究旨在评估新鲜和田间老化生物炭对不同生长环境（淹水与喷灌、常规耕作与免耕）下水稻籽粒中砷、镉和铅的生物累积以及砷形态的影响。由油橄榄修剪残余物（550°C 热解，48 小时）制备的生物炭（单次施用量 28 Mg ha）可将淹水系统中水稻籽粒中砷的生物累积量降低到无法定量的浓度（例如，无机砷分别从 0.178 mg kg降低到<0.04 mg kg），这种效应在田间老化条件下仍然存在，提高了水稻的商业价值。采用喷灌灌溉时，与厌氧系统相比，镉在水稻中的生物累积增加，但生物炭的应用可以抵消这种增加，将其在籽粒中的生物累积减少 32-80%，从而可以同时控制金属和类金属在水稻中的生物累积。生物炭的应用也可以防止 Pb 的生物累积，在所有管理系统中，新鲜生物炭的影响下，其浓度降低了 4-13 倍，与未添加生物炭的对照相比。然而，随着生物炭田间老化，Pb 的固定减少，这表明可能需要重复施用生物炭以保持相同的有益效果。因此，本研究表明，采用油橄榄生物炭进行喷灌可以降低重金属（类金属）在水稻籽粒中的生物累积风险，从而确保食品安全，特别是在新鲜生物炭的影响下。
