复合污染背景下陆地棉对土壤镉的耐受和富集特征

EXPERIMENTS ON GOSSYPIUM HIRSUTUM L'S TOLERANCE AND ACCUMULATION CHARACTERISTICS OF CADMIUM IN MULTIPLE-CONTAMINATED SOIL

采用田间调查采样与可控盆栽试验的方法，研究了我国大面积种植的非食源性经济作物——陆地棉在土壤复合污染条件下对重金属镉（Cd）的耐受与富集特征．结果表明：陆地棉对石灰性壤质土壤中Cd具有显著的忍耐性，即当土壤中Cd质量分数础达到20．258mg·kg-1时，陆地棉生长发育才趋向缓慢或病态；陆地棉对：E壤中Cd具有显著的富集性，其各组织对Cd富集系数（biological concentration factor，BCF）由大到小的序列为：叶片、茎秆、根系、果壳、籽粒、纤维，其中茎秆、根系、果壳大小相当；在污灌区土壤中w（Cd）未超标的情况下，通过陆地棉萃取可使棉田表土层（O～20cm）中w（Cd）每年降低0．0013～0．0020mg·kg-1；陆地棉各组织对土壤中Cd的BCF（Y）值随土壤中w（Cd）（X）的增加呈现指数递减，其拟合关系式为：Y=Yo＋a·e-b＋x，即当w（Cd）由0．258mg·kg-1增加到约1．00mg·kg-1时，BCF值急剧递减；当w（Cd）由1．00mg·kg-1继续增加时，BCF值则趋于平缓的低值区问，表明这时陆地棉对土壤Cd污染只具有忍耐性，其吸附机能可能已经退化．

With soil samples of Cd contaminated farm and outdoor pots, to investigate Gossypium hirsutum L. Cd tolerance and accumulation in multiple contaminated soils. Data indicate that cotton tolerates Cd in calcareous soil markedly, cotton growth did not slow down or show obvious pathology until soil Cd concentration increased to 20. 258 mg-kg-1. Cotton crop showed significant Cd accumulation from soil, with a bioconcentration factor （BCF） in the following descending order： leaf, stem, root, boll, seed, fibers, with stem, root, boll showing similar BCF values. With Cd concentration below that in sewage-irrigated soils, cotton extraction can decrease Cd concentration by 0. 001 3 to 0. 002 0 mg.kg-1（0 to 20 cm） per year in topsoil. Cotton Cd BCF decreases exponentially with increasing soil Cd concentration： Y=Yo＋a·e-b·x. Increasing soil Cd concentration to 〉1.00 mg-kg-1, cotton BCF values for Cd remained low. Therefore at such higher Cd values, cotton was only tolerant to Cd-contaminated soil, Cd adsorption mechanism is overcome.