The Research And Prediction Of Soil ALP Hormesis Under Cd And Pb

Hormesis is the stress response of organisms to toxic substance,which characterized to be low-dose stimulation and high-dose inhibition.Soil enzyme,one of the components involved in various physiological and biochemical processes in the soil,is an ideal endpoint for the study of hormesis in soil ecosystems.The effects of Cd and Pb on the hormesis of soil enzyme have been attracted extensive attention.However,the previous study focused on their independent action,while the study of the characteristics and predictions of their combined action was insufficient.This study took wetlands as examples,including Chongming Dongtan,Hong-tse Lake and Ili River Valley.A fixed-ratio ray-design was used in this study?1?to investigate the Hormesis of soil ALP activity under different soil utilization patterns by single and combined effects of Cd and/or Pb.?2?to analyse the relationship between characteristic parameters of Hormesis effect and physical and chemistry properties of soil.?3?to predict the mixture Hormesis on the basis of the single effects of Cd and Pb,and to provide theoretical basis for predictions of combined Hormesis effect and assessment of toxicological effects of combined heavy metal pollution.The main findings and conclusions were listed as follow:?1?Under the single effect of Cd,the Hormesis effect of soil ALP activity appeared in 12different soil utilization patterns in three wetlands.The maximum effect concentration?M?was between 0.7 and 4.6 mg/kg,the Zone of Enhanced Biological Performance?ZEBP?was between1.4 and 4.7 mg/kg,and the maximum stimulation rate(y_max)was 6.6 to 23.9%.In contrast,under the single effect of Pb,the Hormesis effect of soil ALP activity appeared in 13 different soil utilization patterns in three wetlands.The M was between 141.4 and 454.6 mg/kg,the ZEBP was between 84.6 and 526.8 mg/kg,and the y_max was 5.5 to 12.8%.It could be seen that the y_max of soil ALP activity induced by Cd is significantly higher than that of Pb.?2?The RDA analysis showed that under the single effect of Cd,the main influencing factors of M and y_maxax were soil contents of 2-63?m and 63-200?m,and the main influencing factors of ZEBP were soil contents of 63-200 and soil TN.In comparison,under the single effect of Pb,the main influencing factor of M was soil EC,but the main influencing factors of ZEBP and y_max were soil contents of 2-63?m and 63-200?m.It can be seen that soil texture?particle size difference?may dominate the variation of Hormesis parameters.?3?Hormesis effects of soil ALP in three wetlands were obsevered when the Cd was mixed with Pb.It could be seen that mixing 35-75%?1.75-3.75 mg/kg?of Cd with 25-65%?125-325mg/kg?of Pb were easy to induce Hormesis effect in soil ALP activity.The y_max of the three wetlands was represented by Hong-tse Lake?9.8-50.3%?>Chongming Dongtan?6.4-13.2%?>Ili River Valley?5.4-7.8%?.Further analysis showed that the change of soil ALP activity during the combined effect of Cd and Pb was dominated by the concentration of Pb in the mixture.?4?It was difficult to predict the Hormesis effect of soil ALP activity under the combined effect of Cd and Pb by the traditional linear model proposed by Belz.In order to predict the mixture Hormesis effect,a binary linear regression model?_p=?×?_A×p+?×?_B×?1-p?+?,was proposed based on an assumption of a linear relationship between the single and combined hormetic responses under Cd and Pb.Further analysis showed that soil TN and soil content of 200-2000?m were important influence factors of model parameters ?,? and ?.