| Cadmium is a heavy metal of the highest contamination rate in Chinese herbal medicines, especially roots or rhizomes medicine herbs. The dried rhizome of Ligusticum chuanxiong Hort is used as medicine. In recent years, the situation of cadmium exceeded in Ligusticum chuanxiong Hort is not optimistic, and the cadmium mainly comes from accumulation to the soil during planting with high background of. cadmium. Therefore, starting from the source, repairing cadmium contaminated soil, to further explore the effective cultivation technique of low cadmium content in Ligusticum chuanxiong Hort is the main purpose of the study.Based on the foundation of earlier study, we have consulted a lot of literature and records.and referred fertilizers that comply with state regulations, composed a new type of soil conditioner,that is KH2PO4-NaOH buffer solution.It can be used as functional fertilizer irrigating in the growth period of Ligusticum chuanxiong Hort. Through a large number of field trials, we have respectively studied the effects of KH2PO4-NaOH buffer solution on the remediation of cadmium contaminated soil of Ligusticum chuanxiong Hort and the effectiveness of reducing cadmium in Ligusticum chuanxiong Hot.Moreover, the quality of Ligusticum chuanxiong Hort which were be improved by KH2PO4-NaOH buffer solution, was detected to determine whether Safe and effective or not. On the other hand, we first attempted to Study on the accumulation regularity of cadmium in different tissues of Ligusticum chuanxiong Hort.We have drawn the following main findings by analyzing the correlative data:(1)After KH2PO4-NaOH buffer remediation, the pH value of acid plating soil was increased significantly, the pH level of each group in the order as: PH3>PH2>PH1>PHCK (black group); the percentage of available-state cadmium was reduced, the percentage of potential available-state and unavailable-state cadmium was increased in soil. Compared with the blank group, the percentage of ion-state cadmium was reduced to 4.99%?9.09%?4.02% respectively, and mainly transformed to the oxidation-state?Organic-state.(2)Cadmium content of Ligusticum chuanxiong Hort, collected in harvesting time after KH2PO4-NaOH buffer application, was 1.42 mg/kg (PHCK),0.74 mg/kg (PH1),0.98 mg/kg (PH2) and0.67 mg/kg (PH3), respectively. In the growth cycle of Ligusticum chuanxiong Hort, the effects of KH2PO4-NaOH buffer on ion-state cadmium is slower than pH value about 2 months, and compared with the group of PH1?PH2, the group of PH3could stably maintain high soil pH and low cadmium content for 4 months, until harvest.(3)Groups with KH2PO4-NaOH application is similar to the blank group and standard medicine of Ligusticum chuanxiong Hort respectively (similarity value>0.90). Otherwise, the ferulic acid content was much higher than the control group, groups with KH2PO4-NaOH application was improved by 13.04%?2.06%? 14.36% respectively.(4)The content of cadmium in all 3 batches of Ligusticum chuanxiong Hort exceeded 0.3 mg/kg, the national standard. And the content of cadmium detected in various locations was obviously different.The content of cadmium in cortex was 1.70, 1.25,3.37 times higher than those in other tissues respectively.Here are conducts that we summarize according to the above-mentioned results:Under field conditions, KH2PO4-NaOH buffer solution have a certain repair function on the cadmium contaminated soil. Based on this, by increasing acid soil pH and reducing the percentage of active-state Cd in soil, KH2PO4-NaOH buffer have the function of reducing cadmium content in Ligusticum chuanxiong Hort. The effect of KH2PO4-NaOH solution with pH value of 7.4 on cadmium content in Ligusticum chuanxiong Hort is more effective and steady. Simultaneously, KH2PO4-NaOH buffer remediation did not have an adverse impact on the overall quality of Ligusticum chuanxiong Hort. Otherwise we discovered that the cortex of Ligusticum chuanxiong Hort had super enrichment for cadmium, and is the main part of the accumulation for cadmium. |
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