Feasibility of using Vis-NIR spectroscopy and PXRF spectrometry to estimate regional soil cadmium concentration

Conventionally,soil cadmium(Cd)measurements in the laboratory are expensive and timeconsuming,involving complex processes of sample preparation and chemical analysis.This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance(Vis-NIR)spectroscopy and portable X-ray fluorescence spectrometry(PXRF)to estimate regional soil Cd concentration in a time-and cost-savingmanner.The sensor data of Vis-NIR and PXRF,and Cd concentrations of 128 surface soils from Yunnan Province,China,were measured.Outer-product analysis(OPA)was used for synthesizing the sensor data and Granger-Ramanathan averaging(GRA)was applied to fuse the model results.Artificial neural network(ANN)models were built using Vis-NIR data,PXRF data,and OPA data,respectively.Results showed that:(1)ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation;(2)Fusion methods of both OPA and GRA had higher predictive power(R^(2))=0.89,ratios of performance to interquartile range(RPIQ)=4.14,and lower root mean squared error(RMSE)=0.06,in ANN model based on OPA fusion;R^(2)=0.88,RMSE=0.06,and RPIQ=3.53 in GRA model)than those based on either Vis-NIR data or PXRF data.In conclusion,there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.

Intercropping of Sonchus asper and Vicia faba affects plant cadmium accumulation and root responses

The cadmium(Cd)pollution of farmland soil is serious in the world.The present study investigated the effects of intercropping Vicia faba and the hyperaccumulator Sonchus asper on the Cd accumulation and root responses(morphology and secreted organic acids)of plants grown on soil from a mining area in Yunnan Province,China,under different Cd stress levels(0,50,100,and 200 mg kg-1).Intercropping increased the biomass of both S.asper and V.faba,as well as the Cd accumulation and Cd transfer coefficient from roots to shoots of S.asper,but decreased those of V.faba in the 200 mg kg-1Cd treatment.The Cd concentrations in roots,shoots,and grains from intercropped V.faba plants were positively correlated(P<0.05)with the N,N-diethyl phenylacetamide-extractable Cd content in soil.In the 50 mg kg-1Cd treatment,intercropping decreased citric and malic acids in root secretions of S.asper.Intercropped V.faba secreted more citric,oxalic,acetic,and malic acid compared with S.asper.Intercropping also increased root length and root surface area of both S.asper and V.faba.At 50 mg kg-1Cd,root length for S.asper was higher than that at 0 mg kg-1Cd,whereas V.faba roots had significantly decreased length and mean diameter.Intercropping of S.asper and V.faba is suggested as an in situ phytoremediation strategy of Cd-contaminated soils and may improve the food quality of V.faba.