1. Introduction

Desertification is one of the major environmental disasters in the world [1, 2]. Desertification not only leads to the loss of agriculture and threat to the human survival but also can increase the aerosol concentration, degrade the atmospheric quality, and then lead to some negative impacts on the environment and human health [1, 3, 4]. In general, land desertification is

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

accompanied by the degradation of vegetation [5] and accelerated by the climate anomalies and drought. Some researchers studied the reason of vegetation degradation and its restoration techniques under the various environmental stresses, for example, the drought [6], the high temperature [7, 8], the wind blowing [9], the sand burial [10, 11], the sand flowing [12, 13], the dust deposition on plant leaf [14], and so on.

that the negative charge is gained when the diameter is smaller than 250 μm and positive charge is gained if the diameter is larger than 500 μm [38, 39], which have been proven by Forward et al. [40]. Of course, the critical particle size for the charged polarity of sand maybe varies with the incoming wind velocity, the height from the sand surface, and the grain size, as

Sand Electrification Possibly Affects the Plant Physiology in Desertification Land

http://dx.doi.org/10.5772/intechopen.74976

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It should be specially pointed out that the above researches only obtained the average charge on particles. Due to the limitations of experimental techniques, the experimental devices, and other objective factors, we cannot precisely obtain the quantitative relationship between the charge on single particle and the particle size, the incoming wind speed, the temperature, the humidity, and so on. However, these results have played a positive role in promoting the understanding of the electrification phenomenon of wind-blown sand and enlighten scholars

On the mechanism of contact electrification of sand, the highly accredited conjecture is the contact electrification and the polarization-inducing process [25, 41]. For the contact electrification mechanism, which contains the static contact and the friction, an asymmetric transfer of tiny charged ion or substance is the primary source of it. In addition, it just concerns what these metastatic substances are and why and how many are transferred. But the polarization-inducing process is more intuitive. This mechanism suggests that the particle is polarized by the environmental electric field and the excess charges are repelled to the two sides of the particle. When the moving particle contact with each other, charges with opposite polarity cancel out and then will charge itself after separation. This theory firstly explained the reason of the thunderstorm. Considering that the natural sand is wrapped by a water film [42, 43], some researchers also believed that it also worked in the electrification of wind-blown sand [41]. However, there is still a lack of physical model which is formed by the fusion of those two physical processes. In here, I

Xie et al. [44] proposed a contact electrification model of glass sphere, which can precisely predict the effect of particle size and the impact velocity on the electric quantity. So here, we directly used it to express the contribution of ion transfer to the contact electrification process. Of course, you can replace it with other suitable models, which have more precision. The

where r is the charge density and PD is the probability of any position on the particle surface as a donor; the reference suggests that it is 0.5. Aið Þ i ¼ 1; 2 is the contact area in the collision

δ2

max <sup>¼</sup> <sup>r</sup><sup>1</sup>

=R<sup>1</sup> � �A<sup>2</sup> <sup>¼</sup> <sup>2</sup>π<sup>r</sup>

Q<sup>1</sup> ¼ rPDð Þ 1 � PD ð Þ A2 � A1 (1)

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

� �

=r<sup>1</sup>

r2 <sup>1</sup> � <sup>2</sup>Rδ<sup>2</sup> max <sup>q</sup>

5 4 M K v2 r � �<sup>0</sup>:<sup>4</sup>

2 <sup>1</sup> 1 �

R<sup>1</sup> þ r<sup>1</sup>

well as its size distribution [25].

on its physical mechanism.

want to introduce a simple coupling model for it.

2.1. Contact electrification from ion transfer

model can be expressed as follows:

<sup>A</sup><sup>1</sup> <sup>¼</sup> <sup>2</sup>πR<sup>2</sup>

process, which can be expressed as follows:

δ1

<sup>1</sup> 1 �

max <sup>¼</sup> <sup>R</sup><sup>1</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

5 4 M K v2 r � �<sup>0</sup>:<sup>4</sup>

R2 <sup>1</sup> � <sup>2</sup>Rδ<sup>1</sup> max <sup>q</sup>

R<sup>1</sup> þ r<sup>1</sup>

In addition, some scholars also discussed the influence of various electric fields on the biological system [15]. Murr firstly discussed the physiological influence on plant growth of the electric field environment, and the author found that sufficiently high electric fields have a definite effect on plant growth and the growth response. Andersen and Vad [16] investigated the growth of Serratia marcescens and Escherichia coli at various filed strengths. Some researchers also considered the effect of environmental electric field on the seed germination, plant growth, respiration, and tolerance [17–22].

On the other hand, the soil grain and the sand particles incompactly distribute on the surface of desertification land, which can be driven by the strong wind and eventually formed the windblown sand flowing. Some particles will deposition on the earth, but others can enter into the air with the turbulent process and even develop to the dusty weather [23, 24]. A lot of experiments show that the moving sand is charged, which induced a strong electric field in the air [25–27]. As mentioned above, some experimental results have shown that with the increasing of the applied electric field, the electrostatic field has some negative or positive influence on the plant physiological processes. The wind-blown sand electric field must also work on the similar process.

However, there is no any related report published on the effect of wind-blown sand electric field on the plant physiological processes. In view of this situation, this chapter firstly introduced the research status of sand electrification phenomenon and then proposed some physical models to analyze the effect of environmental electric field on the physiological processes of plants, for example, the root-water absorption process, the water transport processes in the stem, the permeability of cell membranes, etc. Through these discussions, we want to furtherly demonstrate the influence of sand flow on plant growth.
