不同pH值和离子强度下土壤Zn^(2+)/Cd^(2+)/NH_4^+的运移特征

为探究锌、镉及铵态氮在土壤中的运移特征,该文通过室内土柱混合置换试验,分析了不同pH值和离子强度对锌、镉、铵态氮(Zn2+、Cd2+、NH4+)在土壤中运移的影响;获得了示踪剂Br和Zn2+/Cd2+/NH4+的穿透曲线(breakthrough curves,BTCs),并对试验结果进行了模拟。研究表明:Zn2+/Cd2+/NH4+在土壤中运移时,运移速度:NH4+>Zn2+>Cd2+,pH值越高,Zn2+/Cd2+/NH4+的出流时间越晚,峰值越低;离子强度越大,出流时间越早,峰值越高。描述溶质运移的非平衡两点模型(two-site model,TSM)能够较好地模拟Zn2+/Cd2+/NH4+在土壤中的运移,pH值越高,模拟得到的分配系数Kd值越大(以Zn2+为例,由3.853增大到4.386),f值越小(以Zn2+为例,由0.231减小到0.006),分形系数β值很小且无明显变化规律;离子强度越大,模拟得到的分配系数Kd值越小(以Zn2+为例,由4.023减小到到3.381),f值及分形系数β值均很小且无明显变化规律。该研究对深入了解Zn2+/Cd2+/NH4+在土壤中的运移机理、提出污染土壤修复措施提供科学依据。

Effect of Acupuncture at Acupoints Neiguan(PC 6)and Ximen(PC 4)on the Left Cardiac Function in the Patients with Coronary Heart Disease

Purpose. This study is to investigate the influence of acupuncture at acupoints Neiguan （PC 6） and Ximen （PC 4） on the stroke volume and the flow rate of peak value of left ventricle ejection in the patients with coronary heart disease. Methods. 60 cases of coronary heart disease were divided into acupoint Neiguan （PC 6） group and acupoint Ximen （PC 4） group, and the stroke volume and the flow rate of peak value of left ventricle ejection were detected 3 min after manipulating needles and 20 rain after retaining needles respectively, then were compared with those before acupuncture. Results. 3 min after manipulating needles, the stroke volume and the flow rate of peak value of left ventricle ejection were enhanced in 46 cases, and 20 min after retaining needles, both the stroke volume andthe flow rate of peak value of left ventricle ejection were all enhanced in 34 cases. Conclusion. Puncturing acupoints Neiguan （PC 6） and Ximen （PC 4） could enhance the contractility of left ventricle wall, increase the stroke volume of the heart and improve the myocardial ischemia in the patients with coronary heart disease.