1、1. Amelioration of alkali soil using flue gas desulfurization byproducts: Productivity and environmental quality1.1 Abstract：In this study, flue gas desulfurization (FGD) byproducts are used to ameliorate alkali soil. The average application rates for soils with low exchangeable sodium percentage (E
2、SP), mid ESP, and high ESP are 20.9, 30.6, and 59.3 Mg ha 1, respectively. The experimental results obtained for 3 consecutive years reveal that the emergence ratios and yields of the crops were 1.1-7.6 times and 1.1-13.9 times those of the untreated control, respectively. The concentrations of Cr,
3、Pb, Cd, As, and Hg in the treated soils are far below the background values stipulated by the Environmental Quality Standard for Soils (GB15618-1995). Their concentrations in the seeds of corn and alfalfa grown in the treated soils are far below the tolerance limits regulated by National Food Standa
4、rds of China. The results of this research demonstrate that the amelioration of alkali soils using FGD byproducts is promising.2007 Elsevier Ltd. All rights reserved.1.2 IntroductionWet flue gas desulfurization (FGD) is the dominant technology used in the control of SO2 emissions from coal-fired pow
5、er plants. The major byproduct of the process is CaSO4 or a mixture of CaSO3 and CaSO4 (herein referred to as FGD byproducts). With the rapid development of the energy and power industries in China, the installed capacity of power plants with FGD devices, and therefore the amount of FGD byproduct, i
6、s expected to increase rapidly. By the end of 2005, the installed capacity of power plants in China with FGD devices was about 53 GW, and the annual production of FGD byproducts was about 6.5 million tons. According to the National Development Program of China, the installed capacity of power plants
7、 with FGD devices will be 200 GW by 2010, with an annual production of FGD byproducts of 40 million tons; by 2020,these figures will be 530 GW and 90 million tons. As FGD byproducts contain large amounts of moisture and ash, they can only be used as building gypsum after purification and dehydration
8、; this represents an economic disadvantage compared with natural gypsum produced in China. If the FGD byproducts were to be directly disposed of without any utilization or treatment, a vast area of land would be required. Such an approach would be a waste of valuable land resources and represent a p
9、otential threat of secondary pollution to the environment. Significantly, there are large areas of alkali soil in China.These soils are unsuitable for growing agricultural crops,and some such soils are unable to support any plant growth whatsoever. These barren lands severely limit agriculture produ
10、ction in China and have a negative impact on the ecosystem.According to statistics provided by the Ministry of Land and Resource in China, there are 346000 km2 (34.6 million ha) of alkali soils in the northwest, north, northeast, and coastal areas of China; of these areas, soils with heavy exchangea
11、ble sodium percentage (ESP) make up about 92 000 km2. The amelioration of alkali soils over such an enormous area is one of the greatest challenges facing Chinese agriculture. Gypsum has been known to be an amelioration agent for alkali soil for more than 100 years; however, it has been used only ra
12、rely because of the high cost involved in the exploitation, transportation, and crushing of natural gypsum. Although the main component of FGD byproducts is CaSO4, they also contain about 10% alkali material; however, it is uncertain as to whether FGD byproducts with a pH of 7.710.03 (Xu et al.,2005
13、) are suitable for use in the amelioration of alkali soil. In fact, FGD byproducts have been used as a type of modifier for acid soil in the US and other countries (Chen et al., 2001; Li et al., 2004). Professor Matsumoto of Tokyo University firstly proposed the amelioration of alkali soils using FG
14、D byproducts(Matsumoto, 1998).The amelioration of alkali soil using FGD byproducts would make use of tens of millions of tons of FGD byproducts, thereby boosting the application of FGD technology and the development of the pollution-control industry. In addition, the huge extent of barren alkali soi
15、l ameliorated by the FGD byproducts would then be suitable for growing agricultural crops; this would be of significant bene?t to both agricultural development and improvement to local ecosystems.1.3 Materials and methodsField studies were conducted on alkali soil upon the Tumochuan Plain, Huhhot, I
16、nner Mongolia. There are 2 experimental fields. For the No. 1 experimental fields, the total area is about 2.67 ha; soil ESP ranges from 6.1 to 78.4%; and the soil pH is 8.5e9.77. For the No. 2 experimental fields, the total area is 6.67 ha; soil ESP ranges from 40 to 50%; and the soil pH is 9.4e9.5.The concentrations of the main elements in the FGD byproducts were determined using ICP-AES, while the concentrations of certain heavy metals(Pb, Cd, Cr, Cu, Ni, and Se) were determi
