便携式蔬菜叶片重金属镉含量无损检测仪设计与试验

Design and Experiment of Portable Non-destructive Tester for Heavy Metal Cadmium Content in Vegetable Leaves

针对蔬菜叶片重金属镉检测传统方法存在的检测仪器体积大、检测成本高和具有破坏性等问题,提出一种基于可见光近红外波段光谱蔬菜叶片重金属镉检测方法,并设计了一款无需预处理、检测速度快、体积小且便于携带的重金属镉检测仪,能够适用于移动式的现场检测。配置4个重金属镉胁迫梯度(0、1、3、5 mg/L)营养液,培育各镉胁迫的生菜样本,通过高光谱成像系统采集叶片反射光谱数据,利用主成分分析法(Principal component analysis,PCA)筛选出3个特征波长(550、680、800 nm),采用偏最小二乘回归法(Partial least squares regression,PLSR)搭建重金属镉检测模型,该模型测试集相关系数R_(p)为0.9149,测试集均方根误差为0.5271 mg/kg。使用自制的仪器做标定试验,选择A/D采集电压做参考,用标定数据进行建模,模型训练集相关系数R_(c)为0.8581,训练集均方根误差为0.4975 mg/kg,测试集相关系数R_(p)为0.8432,测试集均方根误差为0.5526 mg/kg,模型预测效果较好。最后对便携式重金属镉无损检测仪检测精度进行验证,选取与建模无关的30组镉胁迫生菜叶片实时检测,与标准理化值对比,均方根误差为0.32 mg/kg,绝对测量误差为-0.69~0.66 mg/kg,平均绝对误差为0.26 mg/kg,结果表明检测仪能够实现生菜叶片镉含量的实时无损检测。

Aiming at the problems of large size,high cost and destructive detection of the traditional method of heavy metal cadmium detection in vegetable leaves,a method for detecting heavy metal cadmium in vegetable leaves based on visible lightnear-infrared spectroscopy was proposed,and a method was built without pretreatment.The heavy metal cadmium detection instrument with fast detection speed,small size and easy to carry can be suitable for mobile on-site detection.Nutrient solution of four heavy metal cadmium stress gradients(0 mg/L,1 mg/L,3 mg/L and 5 mg/L)was configured,lettuce samples were cultivated under each cadmium stress,and leaf reflectance data was collected through a hyperspectral imaging system.Three characteristic bands(550 nm,680 nm and 800 nm)were selected by using principal component analysis(PCA),and a heavy metal cadmium detection model was built by using partial least squares regression(PLSR).The correlation coefficient R_(P) of test set was 0.9149,and the root mean square error of test set was 0.5271 mg/kg.The designed detection instrument for heavy metal cadmium in vegetable leaves included:light source part,signal processing part,display part,power supply part and control part.The size of the instrument was 50 mm×70 mm×60 mm.Using self-made instrument for calibration experiment,selecting A/D acquisition voltage as reference,calibration data were used for modeling,model training set correlation coefficient R_(c) was 0.8581,training set root mean square error was 0.4975 mg/kg,test set correlation coefficient R_(p) was 0.8432,root mean square error of the test set was 0.5526 mg/kg,and the model prediction performance was better.Finally,the detection accuracy of the portable heavy metal cadmium nondestructive testing instrument was verified.Totally 30 groups of cadmium-stressed lettuce leaves were selected for real-time detection,which were not related to the modeling.Compared with the standard physical and chemical values,the root mean square error was 0.32 mg/kg,and the absolute measurement error was-0.69~0.66 mg/kg,the average absolute error was 0.26 mg/kg.The results showed that the instrument can realize real-time non-destructive detection of cadmium content in lettuce leaves.