Detecting Sulfuric and Nitric Acid Rain Stresses on Quercus glauca through Hyperspectral Responses.

Shanqian Wang,Xiuying Zhang,Yuandan Ma,Xiaomin Zhang,Min Cheng,Lei Liu,Xinhui Li

doi:10.3390/s18030830

Abstract

Acid rain, which has become one of the most severe global environmental issues, is detrimental to plant growth. However, effective methods for monitoring plant responses to acid rain stress are currently lacking. The hyperspectral technique provides a cost-effective and nondestructive way to diagnose acid rain stresses. Taking a widely distributed species (Quercus glauca) in Southern China as an example, this study aims to monitor the hyperspectral responses of Q. glauca to simulated sulfuric acid rain (SAR) and nitric acid rain (NAR). A total of 15 periods of leaf hyperspectral data under four pH levels of SAR and NAR were obtained during the experiment. The results showed that hyperspectral information could be used to distinguish plant responses under acid rain stress. An index (green peak area index, GPAI) was proposed to indicate acid rain stresses, based on the significantly variations in the region of 500–660 nm. Light acid rain (pH 4.5 SAR and NAR) promoted Q. glauca growth relative to the control groups (pH 5.6 SAR and NAR); moderate acid rain (pH 3.0 SAR) firstly promoted and then inhibited plant growth, while pH 3.0 NAR showed mild inhibitory effects during the experiment; and heavy acid rain (pH 2.0) significantly inhibited plant growth. Compared with NAR, SAR induced more serious damages to Q. glauca. These results could help monitor acid rain stress on plants on a regional scale using remote sensing techniques.

Highlights

Acid rain, or acid deposition, has become one of the most serious environmental problems around the world
The results showed that acid rain could significantly influence the spectral information near the green peak (500–660 nm) in the visible region, and green peak area index (GPAI) could track well the responses of Q. glauca under sulfuric acid rain (SAR) and nitric acid rain (NAR) treatments
Under light SAR stress, GPAI difference relative to pH 5.6 SAR treatment increased with increasing experimental days, suggesting pH 4.5 SAR has a positive effect on Q. glauca; the moderate

Summary

Introduction

Acid deposition, has become one of the most serious environmental problems around the world. Along with Europe and North America, China has become the third region severely polluted by acid rain. Sulfur dioxide (SO2 ) and nitrogen oxides (NOX ), mainly emitted from the combustion of fossil fuel and traffic emissions, are the precursors of acid rain [1,2]. In Europe and North America, acid rain is dominated by nitric type because of the huge oil consumption by automobiles, while sulfuric acid rain dominates in China due to the use of coal as the main energy source [4]. In recent years acid rain in China has gradually transformed from sulfuric type to the mixed sulfuric and nitric type, and the areas affected by acid rain have extended from the south to the north with the rapid economic growth and industrialization [5,6]

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Discussion

Conclusion