镉胁迫下红树林沉积物中水溶性有机物的变化

Effects of Cd on Dissolved Organic Matters in Mangrove Sediments

在温室条件下采用根箱法，研究了在不同浓度镉（Cd，0～50mg kg^-1）胁迫下红树植物秋茄幼苗生长的土壤中水溶性有机碳（DOC）和水溶性有机氮（DON）的浓度变化，研究表明，秋茄沉积物中DOC和DON含量随Cd胁迫浓度的增加出现不同程度先降后升再降的趋势，DOC含量在土壤Cd处理浓度为10mg kg^-1和30mg kg^-1时分别达到谷值（0．134mg g^-1）和峰值（0．190mg g^-1），除了R5层（30mg kg^-1 Cd处理时DOC含量高于对照组），其他土层的对照组DOC含量均高于Cd处理组的DOC含量，DON含量在土壤Cd处理浓度为5mg kg^-1和20mg kg^-1时分别达到谷值（0．075mg g^-1和0．081mg g^-1），在10mg kg^-1和30mg kg^-1时分别达到峰值（0．117mg g^-1和0．138mg g^-1），这表明沉积物中的DOC和DON在低浓度的Cd胁迫下可与Cd相互作用，降低Cd的有效性，反映秋茄对低浓度的Cd有一定的抵抗能力，高浓度的Cd胁迫可能刺激秋茄根系分泌和改变土壤微环境，与非根际层土壤相比，根际层的DOC和DON含量较高。

Soil-culture medium was used to investigate the effects of cadmium on dissolved organic carbon （DOC） and nitrogen （DON） in mangrove sediments. The seedlings of Kandelia candel （L.） Druce were cultured in greenhouse supplied with a se- ries of cadmium concentrations （0-50 mg kg^-1） from the beginning of May to the end of December in 2004. After harvest, the contents of DOC and DON in mangrove sediments were measured. The results showed that the content of DOC decreased first at lower Cd levels, which might be regarded as a self-protecting function of plants. After they reached the lowest value （0. 134 mg g^-l ） at cadmium concentration of 10 mg kg^-1 , the content of DOC increased, reaching the peak value （0. 190 mg g^-1 ） at cadmium concentration of 30 mg kg - 1. The content of DON had two lowest values （0. 075 mg g^-1 and 0. 081 mg g^-l ）, when the cadmium concentrations were 5 mg kg^-1 and 20 mg kg^-1. And it reached the peak values, 0. 117 mg g^-1 and 0. 138 mg g^-l, when cadmium concentrations were 10 mg kg^-1 and 30 mg kg^-1 , respectively. These results indicated that DOC and DON in mangrove sediments could be combined with cadmium at its lower concentration. Higher concentration of cadmium might induce more root secretion and metabolizable production from mangrove, and result in the increase of DOC and DON. Compared with non-rhizosphere soil, both contents of DOC and DON in rhizosphere were higher than those in any other soil layers, indicating that relatively high DOC and DON contents presented in rhizosphere soil. Fig 3, Tab 2, Ref 18