Climate Change & Agroecology Division, Department of Agricultural Environment, National Academy of Agricultural Science, RDA, 150 Suin-ro, Kwonsun-gu, Suwon 441-707, Republic of Korea.
J Environ Sci (China). 2010;22(1):98-105. doi: 10.1016/s1001-0742(09)60080-2.
This study investigated the influence of Indian mustard (Brassica juncea) root exudation on soil solution properties (pH, dissolved organic carbon (DOC), metal solubility) in the rhizosphere using a rhizobox. Measurement was conducted following the cultivation of Indian mustard in the rhizobox filled four different types of heavy metal contaminated soils (two alkaline soils and two acidic soils). The growth of Indian mustard resulted in a significant increase (by 0.6 pH units) in rhizosphere soil solution pH of acidic soils and only a slight increase (< 0.1 pH units) in alkaline soils. Furthermore, the DOC concentration increased by 17-156 mg/L in the rhizosphere regardless of soil type and the extent of contamination, demonstrating the exudation of DOC from root. Ion chromatographic determination showed a marked increase in the total dissolved organic acids (OAs) in rhizosphere. While root exudates were observed in all soils, the amount of DOC and OAs in soil solution varied considerably amongst different soils, resulting in significant changes to soil solution metals in the rhizosphere. For example, the soil solution Cd, Cu, Pb, and Zn concentrations increased in the rhizosphere of alkaline soils compared to bulk soil following plant cultivation. In contrast, the soluble concentrations of Cd, Pb, and Zn in acidic soils decreased in rhizosphere soil when compared to bulk soils. Besides the influence of pH and DOC on metal solubility, the increase of heavy metal concentration having high stability constant such as Cu and Pb resulted in a release of Cd and Zn from solid phase to liquid phase.
本研究采用根盒法研究了芥菜（Brassica juncea）根系分泌物对根际土壤溶液性质（pH 值、溶解有机碳（DOC）、金属溶解度）的影响。在根盒中种植芥菜后，对四种不同重金属污染土壤（两种碱性土壤和两种酸性土壤）进行了测量。芥菜的生长导致酸性土壤根际土壤溶液 pH 值显著增加（增加 0.6 个单位），而碱性土壤仅略有增加（<0.1 pH 单位）。此外，DOC 浓度无论土壤类型和污染程度如何，都增加了 17-156mg/L，表明根从 DOC 中分泌出来。离子色谱测定表明，根际总溶解有机酸（OAs）显著增加。虽然在所有土壤中都观察到根分泌物，但土壤溶液中 DOC 和 OAs 的量在不同土壤之间差异很大，导致根际土壤溶液中金属发生显著变化。例如，与对照土壤相比，芥菜在碱性土壤中的根际土壤溶液中 Cd、Cu、Pb 和 Zn 浓度增加。相比之下，与对照土壤相比，在酸性土壤中，Cd、Pb 和 Zn 的可溶性浓度在根际土壤中降低。除了 pH 值和 DOC 对金属溶解度的影响外，高稳定性常数（如 Cu 和 Pb）的重金属浓度的增加导致 Cd 和 Zn 从固相释放到液相。
