铅污染水稻的冠层高光谱特征研究

本研究通过铅污染土壤中的水稻盆钵栽培试验,考察了水稻对土壤重金属铅的吸收以及铅对水稻生长的胁迫,并借助地面高光谱辐射仪器获取多个生育期（苗期、分蘖前期、分蘖盛期、拔节期和孕穗期）的水稻冠层高光谱反射数据。在进行光谱测量的同时测定了水稻植株体内的铅含量与冠层叶片叶绿素含量。分析结果表明:铅污染胁迫下水稻冠层叶片叶绿素含量与叶绿素a、b组成变化明显,可见光区间520nm～560nm和630nm～690nm处是铅污染水稻对冠层反射高光谱敏感的特征波段。通过模拟高光谱分辨率遥感传感器MODIS的相应波段（第4通道:545nm～564nm、第1通道附近:620nm～670nm）以及考虑叶绿素的荧光特征（760nm）,本研究分别选择敏感波段中的552nm,672nm与760nm构造了复合归一化污染指数CNDPI（Compos-ite Normalized Difference Pollution Index）,分析发现CNDPI能够明显地区分不同铅污染水平的水稻。在分蘖前期采用适当的冠层光谱反射率形式（敏感波段、CNDPI）可以实现水稻铅污染的遥感监测。

Canopy Hyperspectral Characteristics of Paddy Plants Contaminated by Lead

Increased heavy metal concentrations in cropland soil cause stress on many crops and decline crops′ quality.The objective of this article is to try a new method to monitoring heavy metal pollution in cropland like remote sensing,which can be applied to estimate Pb pollution on paddy plant. Experiment that paddy plants were cultivated in the potted soils manually contaminated by Pb was settled down to investigate the stress caused by Pb absorbed by paddy plants.In the developmental stages of seeding,early tillering,full tillering,jointing and booting,hyperspectral reflectance measurements on paddy plant canopy were done by a hyperspectral radiometer.Meanwhile,we got Pb concentrations in parts of paddy plant,and canopy leaves′ chlorophyll content.Quantitive relationship between Pb concentration in parts of paddy plant,canopy leaves′ chlorophyll content and canopy reflectance was studied.Results showed that chlorophyll content of canopy leaves and composition of chlorophyll,chlorophyll a and b vary obviously under Pb stress.The difference of canopy reflectance at the sensitive bands of 520nm～560nm and 630nm～690nm is most significant,and it differs from the three Pb treatments on rice from each other.Therefore,these spectral regions are validated as sensitive bands to Pb pollution on paddy plants.According to the first（620nm～670nm） and forth channel（545nm～564nm） of MODIS and sensitive band（760nm） in the near infrared region,552nm,672nm and 760nm were selected to construct composite normalized difference pollution index（CNDPI）.CNDPI discriminates all the three Pb contamination levels of paddy plants.At the early tillering stage,the canopy hyperspectral reflectance and CNDPI distinguish Pb pollution condition commendably.Therefore,monitoring Pb pollution on paddy plants with remote sensing data of raw canopy reflectance and CNDPI at the early tillering stage is a potential solution and new reference for heavy metal pollution condition monitoring technology.