Effect of root exudates of intercropping Vicia faba and Arabis alpina on accumulation and sub-cellular distribution of lead and cadmium.

A field experiment in which a hyperaccumulator (Arabis alpina) was intercropped with winter crop (Vicia faba), was conducted to understand effect of the root exudates on the content and accumulated amounts, sub-cellular distribution of Cd and Pb of the intercropped plants during the ripening period of V. faba (120 d after sowing). The results showed that contents of soluble sugars exuded from the roots of intercropped A. alpina were 67.6% less than that of the monocropped plant, whereas contents of free amino acids was 57.9% greater. The total contents of organic acids exuded from roots of intercropped A. alpina and V. faba were 578.8% and 37.8% greater than that of monocropped plants, respectively. The contents of tartaric acid and malic acid exuded by roots of intercropped A. alpina were greater 31.9 times and 15.9 times than those of monocropped A. alpina, respectively. The contents and accumulated amounts of Cd and Pb in intercropped A. alpina were greater than those of monocropped A. alpina. The contents of Pb bound to organic matter in cell walls, cytoplasm and organelles of intercropped plants were greater than those of monocropped plants. These results demonstrate that increases in accumulated amounts of Pb and Cd caused by intercropping were closely related to migration of Cd and Pb in plants mediated by the composition and content of the root exudates.

Adsorption properties and mechanism research of phosphorus with different molecular structures from aqueous solutions by La-modified biochar.

In order to explore the adsorption characteristics of phosphorus from molecules with different molecular structures and varying number of phosphate groups on metal-modified biochar, walnut shell biochar was modified with LaCl3 to prepare lanthanum-loaded biochar (BC-La). Adsorption of four polar components, namely phytic acid (IHP), adenosine-5'-disodium triphosphate (5-ATP), hydroxyethylidene diphosphonic acid (HEDP), and sodium pyrophosphate (PP), was studied. The adsorption properties and mechanism of phosphorus sorption by BC-La were analyzed by SEM-EDS and FTIR for the different structures. The results showed that the maximum adsorption capacity of BC-La for IHP, 5-ATP, HEDP, and PP was 85.85, 9.04, 15.80, and 14.45 mg/g, respectively. The adsorption capacity was positively correlated with the polarity of organic phosphorus. The adsorption behavior conformed to the quasi second-order kinetic fitting equation, and the increase of temperature was conducive to the removal of all four phosphorus pollutants. BC-La adsorbs IHP and HEDP mainly through electrostatic attraction. The adsorption of 5-ATP and PP is dominated by complexation. The La-modified biochar has broad prospects in water remediation, which can provide a theoretical basis for removal of different forms of phosphorus pollutants and prevention and control of water eutrophication.