摘要
负载铁生物炭(FeBC)已证实对溶液体系和雄黄矿高砷(As)尾渣中的无机As具有极为显著的吸附钝化效能,但其对土壤-水稻系统中As的溶出特性和生物有效性的影响尚为空白.为此,本研究系统探析了FeBC处理对水稻根际As溶出特性、根表铁膜As持留-释放模式转化和As向水稻体内各器官转运积累的影响与发生机制.结果表明,FeBC处理条件下的水稻根际pH普遍高于对照(CK),而氧化还原电位(Eh)则低于CK;FeBC处理所导致的根际Eh下降几乎同步使根际孔隙水As、Fe浓度自分蘖期后均随FeBC比例的增加而升高,且孔隙水As、Fe浓度具有显著正相关性(p<0.01).成熟期内根表铁膜Fe、As含量均随FeBC比例的增加而升高,这一点可由微区X射线荧光(μ-XRF)所显示的2%FeBC处理中水稻根系表面Fe、As浓度均显著高于CK得到印证,而这一特点导致FeBC处理下的白根和糙米As含量显著升高(p<0.05).以上结果表明,FeBC能有效提高水稻根表铁膜形成量及其对As的持留,但超过特定阈值的铁膜浓度(20~25 mg·g^(-1))对As的大量富集却可成为根系对As的吸收源,促进As向根系内的转运,并导致稻米As积累量升高.由此可见,含Fe钝化剂对水稻根际As生物有效性的影响具有可变性,其应用风险和产生机制值得引起高度关注.
It has be confirmed that Fe-impregnated biochar（FeBC） can exert very significant sorption and immobilization effects towards inorganic arsenic（As） in both aqueous solution and realgar mine tailings with high As level.However,its effect on As solubility and bioavailability in soil-rice system is yet to identify.Therefore,a systematic study was carried out to investigate the impact of FeBC on As solubility in rice rhizosphere,As sequestration and release from iron plaque and As accumulation in different rice tissues.Based on the results,pH values of the FeBC-amended rice rhizosphere were generally higher than those of control（CK）,while the redox potential（Eh） values in FeBC treatments were consistently lower than CK.With lower Ehat higher FeBC ratio,dissolved As and Fe concentrations in rhizosphere pore water increased after tillering stage,and a significant positive correlation（p0.01） was recorded between pore water As and Fe.During harvesting stage,As and Fe concentrations in the iron plaque were both enhanced in a FeBCdependent manner,which was in agreement with the remarkably higher root surface As and Fe levels in the 2% FeBC treatment than CK as demonstrated by micro-X ray fluorescence（μ-XRF）.Along with this enhancement,increased As accumulation in white root and brown rice（p0.05） were recorded simultaneously.According to the above results,despite the enhanced formation of iron plaque and As sequestration with FeBC,root uptake and further transport of As into grains can be accelerated by elevated Fe level in iron plaque（20~25 mg·g-1） which could serve as an apparent source of As.Therefore,it is highlighted that the effect of Fe-containing amendments towards soil As is variable and their application risks and the underlying mechanisms deserve particular concerns and warrant further study.
出处
《环境科学学报》
CAS
CSCD
北大核心
2017年第8期3158-3168,共11页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No.41301339)
湖南省地理学重点学科项目
湖南省自然科学基金项目(No.2017JJ2180)
霍英东教育基金会高等院校青年教师基金(No.151029)
湖南省高校科技创新团队支持计划项目(2104)
湖南省教育厅优秀青年项目(No.17B157)~~
关键词
负载铁生物炭
水稻
砷
根表铁膜
根系泌氧
Fe-impregnated biochar
rice
arsenic
iron plaque on root surface
radial oxygen loss
