Frontier of Environmental Science June 2014, Volume 3, Issue 2, PP.13-22
Effects of Application of Iron Ore tailing in Soil on the Content and Allocation of Some Nutrient Elements in Gardenia jasminoides Ellis Rui Li, Lanfang Yang*, Haibo Li, Mengxue Wan School of Resource and Environmental Science, Hubei University, Wuhan 430062, China
Abstract In order to develop the resource utilization of iron ore tailing and the land reclamation and vegetation restoration on the mine, a pot experiment of mixing different rate of iron tailing sands with soil to plant gardenia (Gardenia jasminoides Ellis) was conducted, in which the contents of N, P, K and Fe in yellow leaves, green leaves, stems and roots of gardenia were analyzed. The results showed that mixing iron ore tailing with soil (red limestone soil) had a significant effect on the nutrient content and the allocation of nutrient uptake in each part of gardenia. The order of nitrogen content in gardenia was green leaf>root>stem>yellow leaf and the nitrogen uptake of gardenia in aerial parts accounted for 51%~68% of the total nitrogen uptake. When the mixing rate was 10%~40%, the nitrogen uptake of gardenia in aerial parts was significantly higher than the control, among which 30% mixing rate was the highest. The order of phosphorus content in gardenia was green leaf>stem>root>yellow leaf and the phosphorus uptake of gardenia in aerial parts accounted for 64%~80% of the total phosphorus uptake. Comparing with the control, mixing iron ore tailing increased the rate of phosphorus uptake in aerial parts when the rate is 20%~30%. The potassium content in each part was also increased by mixing iron ore tailing with soil. The order of potassium content was green leaf>root>stem and the amount of potassium absorbed by aerial parts of gardenia took up 51%~63%. When mixing rate was higher than 50%, the amount of potassium uptake of aerial parts was notably lower than the control. Mixing iron ore tailing at the rate of 30% made the rate of the amount of potassium uptake highest and significantly higher than the control and other samples. When experimental soil was mixed with 20%~50% iron ore tailing sands, the iron content and the proportion of Fe uptake in aerial parts rise. The order of iron content was root>yellow leaf>green leaf>stem. The Fe uptake in aerial parts only accounted for 9%~25% and the highest appeared when the mixing rate was 30%. In summary, some application rates of iron ore tailing in soil can accelerate the growth of gardenia by translocation of soil nutrients to aerial and tender parts, therefore, according to the nutrient contents and the allocation of nutrient uptakes in gardenia, the suitable application rate of iron ore tailing in soil ranges from 20% to 50% and the most suitable rate is around 30%. Keywords: Application of Iron Ore tailing in Soil; Gardenia (Gardenia jasminoides Ellis); Nutrient Content; Nutrient Uptake
1 INTRODUCTION Iron ore tailings are the remained rock mineral debris after the useful metals such as iron are elected from the raw iron ore which goes through the beneficiation process of crushing, screening, grinding, grading, and then re-election, flotation or cyanide while mining (Chen Hu et al. 2012). They are usually stacked in the tailings pond of a mine. But piling up tailings not only takes up a lot of arable land, but also consumes the human, financial and material resources to establish and maintain the tailings pond. What’s worse, it poses security risks. The tragedy due to tailing pond breach that costs the fortune or even the lives of the people in mining areas is reported occasionally. For instance, a significantly severe dam breach accident occurred in Shanxi Province Linfen city Xiangfen county new tower Mines Ltd. resulted in 277 deaths, four missing, and three injuries, the direct economic losses of which reached 9619 million RMB (Zhang Zhaoguo. 2009). Tailings storage mismanagement will damage the local - 13 http://www.ivypub.org/fes
ecological environment and lead to pollution of soil, sediment, surface and groundwater too. Studies on the fishes in the lake polluted by iron ore tailings suggested that the contaminated water damaged fish DNA and reduced the level of VA (Yayne et al, 1998). Up till now, the most common methods of utilizing iron ore tailing as resource are recycling element, making it the backfill material for backfilling mining or the raw material for cement production, producing floor or building bricks, being the filler in road construction and so on (Huang Yonggang. 2013). However, some of the utilization methods require large amount of investment funds and construction of the plant, some need long-distance transportation and some demand high techniques. Because of that, the applications are by large restricted. Meanwhile, the damages brought about by iron mining to vegetation, soil and topography is really serious. During the process of mine land and vegetation restoration, large quantities of covering soil are needed. Borrowing that large amount of soil causes not only the increase of transportation costs but also the destruction of landscape ecological environment in the soil borrowing area. Based on above reasons, exploring the iron ore tailing in soil contributes to not only the reduction of the amount of iron ore tailings piling up and the borrowing soil for land reclamation and vegetation restoration but also the promotion of land reclamation and vegetation restoration on the mine. Moreover, it reduces the security risks on tailings reservoir and the costs of mine production. Given the benefits, developing such application has important ecological, social and economic significance. In this study, a pot experiment of mixing different rate of iron tailing sands with soil to plant gardenia (Gardenia jasminoides Ellis) was carried out in order to understand effects of application of iron ore tailing in soil on the content and allocation of some nutrient elements in this plant and then provide a scientific basis for the application of iron ore tailing in soil, mining land reclamation and vegetation restoration.
2 MATERIALS AND METHODS 2.1 Materials The ore tailings in this experiment are collected from Wuhan Iron and Steel Group Mineral Company Jinshandian tailings. After tailings dry naturally, sieve them by 2 mm sieve for the following use. The composition of iron ore tailings are >2 mm, 2~1 mm, 1~0.2 mm and<0.2 mm which accounted for 2.3%, 12.3%, 69.2% and 16.2% respectively. The soil in this experiment is collected from the covering soil on the slope of this tailings dam. Soil type is lime soil types, red limestone soil sub-categories. After taken back and removing stones and plant residues, soil was sieved through 5 mm sieve for following use. Soil organic matter content was 1.8 g kg-1. Nitrogen, phosphorus and potassium contents were 15.4, 3.6, 103.0 mg kg-1. CEC (cation exchange capacity) was 29.1 cmol (+) kg-1and soil pH was 7.92 (soil and water ratio of 2.5:1). Soil texture is clay loam. The plant used in this experiment was Gardenia jasminoides Ellis, Rubiaceae Gardenia and is a perennial evergreen shrub. Seedlings were purchased from Wuhan Nanhu flowers market.
2.2 Pot Experiment Nine different addition ratios (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%) of iron ore tailings were set up in the experiment. Each ratio was repeated three times in three pots and every pot contained 3 kilograms mixed soil. Soil and tailings were weighed according to their proportion in each pot and then were mixed. After the base fertilizer was added, the mixture of soil, tailings and fertilizer was put into each pot. Then each Gardenia seedling was planted in each pot. Each kilo of base fertilizer is fertilized with N, P, K, 100, 50, 63 mg kg-1 respectively. A solution formulated with ammonium sulfate and potassium dihydrogen phosphate, containing N, P, K, respectively 20, 10, 12.6 mg mL-1 was added 15mL per pot while mixing the soil. Plantation of seedlings was on October 9, 2011. The plants were managed till November 20, 2013 and then harvested for sample preparation.
2.3 Sample Preparation Gardenia seedlings were pulled out of whole on November 20, 2013. Harvested plant samples were divided into root, stem and leaves and then carefully rinsed with tap water followed by deionized water. After the adhering water dried, the samples were cut into small pieces less than 0.5cm and folded in paper bags. The samples were dried at 70â&#x201E;&#x192; to constant weight in an air-blower-driven drying closet. After cooling in the dryer and being weighed, the tissues were - 14 http://www.ivypub.org/fes
pulverized and stored in plastic bottles for analysis.
2.4 Chemical Analysis Determination of nitrogen, phosphorus, potassium and iron content in samples: Plant samples were digested in sulfuric acid-hydrogen peroxide, and thereby, nitrogen content was determined by indophenol blue spectrophotometry; phosphorus content was determined by molybdenum-antimony anti-spectrophotometric method; potassium content was determined by flame photometry; iron content was determined by phenanthroline spectrophotometry. The basic physical and chemical properties of soil were determined by conventional methods, namely organic matter by potassium dichromate method with external heating, available nitrogen by diffusion method, available phosphorus by molybdenum blue method, Available potassium by flame photometry, CEC by ammonium acetate, pH by potentiometry.
2.5 Data Processing All data was calculated the mean and standard deviation and plotted using Excel 2003. Equation analysis and multiple comparisons were performed using SPSS version 11.00 software. LSD method was applied in multiple comparisons and the significant level was 0.05.
3 RESULTS AND ANALYSIS 3.1 Effects of Application of Iron Ore tailing in Soil on Nitrogen Content of Gardenia jasminoides Ellis Table 1 indicated that mixing iron ore tailing sands with experimental soil had a significant impact on the nutrient content in different parts of Gardenia jasminoides Ellis. When the nitrogen content in green leaf was analyzed, the treatment of mixing rate of 10%, 40%, 50% showed no significant difference with the control. The rest mixing rate reduced the nitrogen content in green leaves. As for yellow leaf, 40% and 60% mixing rate increased the nitrogen content in them. While the mixing rate was 70%, the treatment was notably lower than the control. And the rest showed no significant difference. Nitrogen content in stem changed a little when mixing rate was 10% and 40%. A marked increase of nitrogen content was also observed in stem at the mixing rate of 60%. The exact opposite phenomenon happened at the rest mixing rate. And nitrogen in root increased remarkably at the rate of 60% and had little difference with the control at 40%. The rest were all significantly lower than the control. At the same mixing rate, the order of nitrogen content in different parts of Gardenia jasminoides Ellis was green leaf> root > stem >yellow leaf. The nitrogen content in green leaf was 2.0~2.9 times that of the yellow leaf, 1.4~2.3 times that of the stem and 1.1~1.6 times that of the root. TABLE.1. NITROGEN CONTENT OF GARDENIA JASMINOIDES ELLIS AT DIFFERENT TAILING MIXING RATE (mg g-1) Mixing rate/% 0 10 20 30 40 50 60 70 80
Green leaf 16.07±0.13a 15.86±0.65a 12.71±0.38b 15.16±0.14c 16.21±0.71a 15.90±0.12a 15.03±0.10c 12.52±0.10bd 12.05±0.30d
Yellow leaf 5.60±0.17ab 5.61±0.25ab 5.74±0.07a 5.40±0.25bd 7.36±0.06c 5.87±0.09a 7.48±0.20c 5.28±0.20d 5.61±0.04a
Stem 8.48±0.21ab 8.11±0.29b 6.69±0.08c 7.12±0.11d 8.56±0.31a 6.97±0.18bc 10.56±0.29d 5.81±0.18e 5.81±0.35e
Root 12.25±0.15a 10.66±0.17b 10.34±0.11b 9.53±0.21c 12.08±0.45a 11.13±0.34d 12.90±0.21e 11.38±0.17d 9.47±0.16c
According to Figure 1, mixing iron ore tailings also had an impact on the allocation of nitrogen uptake in Gardenia jasminoides Ellis. N uptake was represented by the product of biomass and nitrogen. The nitrogen uptake of Gardenia jasminoids Ellis in aerial parts accounted for 51%~68% of the total nitrogen uptake. When the mixing rate was 10%~40%, the nitrogen uptake of Gardenia jasminoids Ellis in aerial parts was significantly higher than the - 15 http://www.ivypub.org/fes
Ratio of N uptake in aerial paits/%
control. There was little difference between the experiment group and the control at the rate of 50% and 60%. While the rate was 70% and 80%, the N uptake of experiment group was much lower. 70
c
65 60
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FIGURE.1. EFFECTS OF IRON TAILINGS ON THE ALLOCATION OF NITROGEN UPTAKE ON GARDENIA JASMINOIDES ELLIS.
3.2 Effects of Application of Iron Ore tailing in Soil on Phosphorus Content of Gardenia jasminoides Ellis Table 2 showed that mixing iron ore tailing sands with experimental soil had a remarkable impact on the phosphorus content in different parts of Gardenia jasminoides Ellis. In green leaf, except the mixing rate of 30% and 40%, which influenced the phosphorus content in an insignificant way, the rest mixing rate reduced the phosphorus content of Gardenia jasminoides Ellis notably. In yellow leaf, the phosphorus content of Gardenia jasminoides Ellis had no significant difference with the control at the mixing rate of 10%, 20%, and 30%. When the iron ore tailing mixing rate was 40%, 70%, 80%, the phosphorus content in yellow leaf was conspicuously higher. The 50% and 60% mixing rate made the phosphorus content notably lower than the control. As for stem, the mixing rate of 10%, 50%, and 60% significantly reduced the phosphorus content and the mixing rate of 40%, 70% had little difference on the phosphorus content, compared with the control. At the rest mixing rate, the phosphorus content was greatly higher than the control. What was observed in root was that 20%, 30%, and 40% mixing rate did not affected the phosphorus content and 10% and 50% mixing rate lowered the phosphorus content significantly. The rest experiment group was significantly increased. The highest phosphorus content of Gardenia jasminoides Ellis lay in green leaf and the lowest was in yellow leaf, indicating the order of green leaf>stem>root>yellow leaf. The phosphorus content in green leaf was 3.1~4.9 times that of yellow, 1.6~3.5 times that of root, 1.3~2.7 times that of stem. Based on Figure 2, mixing iron ore tailings had a great influence on the allocation of phosphorus uptake in the aerial part and the root of Gardenia jasminoides Ellis too. The phosphorus uptake of Gardenia jasminoids in aerial parts accounted for 64%~80% of the total phosphorus uptake. Comparing with the control, mixing iron ore tailing sands increased the rate of phosphorus uptake in aerial parts when the rate was 20%~30%. While the rate was 10%, 40%, and 50%, there was no significant difference between the two groups. When the rate was 60%~80%, the proportion of phosphorus absorbed by aerial parts was notably lower than the control. TABLE.2. PHOSPHORUS CONTENT OF GARDENIA JASMINOIDES ELLIS AT DIFFERENT TAILING MIXING RATE (mg g-1) Mixing rate/% 0 10 20 30 40 50 60 70 80
Green leaf 1.803±0.022a 1.587±0.010bc 1.668±0.043db 1.853±0.130a 1.837±0.030a 1.570±0.025ce 1.690±0.072de 1.627±0.038be 1.577±0.016bc
Yellow leaf 0.384±0.013a 0.375±0.003a 0.391±0.018ab 0.391±0.016ab 0.420±0.004b 0.321±0.005c 0.345±0.014c 0.423±0.026b 0.499±0.044d - 16 http://www.ivypub.org/fes
Stem 0.891±0.020a 0.632±0.006bd 0.954±0.038c 0.955±0.002c 0.889±0.044a 0.586±0.030b 0.643±0.043d 0.882±0.018a 1.184±0.048e
Root 0.608±0.023a 0.488±0.029b 0.622±0.032a 0.643±0.011ac 0.676±0.010c 0.458±0.003b 0.621±0.014a 0.668±0.021c 0.945±0.028d
Ratio of P untake in aerial parts/%
85 80
b a
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75
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20 30 40 50 60 Percentage of iron ore tailings/%
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FIGURE.2. EFFECTS OF IRON TAILINGS ON THE ALLOCATION OF PHOSPHORUS UPTAKE ON GARDENIA JASMINOIDES ELLIS.
3.3 Effects of Application of Iron Ore tailing in Soil on Potassium Content of Gardenia jasminoides Ellis Table 3 indicated that mixing iron ore tailing sands with experimental soil had a significant impact on the potassium content in different parts of Gardenia jasminoides Ellis. When we analyzed the potassium content in green leaf, the experiment group of mixing rate of 10%, 40%, and 50% showed no significant difference with the control group. The rest mixing rate increased the potassium content in green leaf remarkably and 30% mixing rate increased the potassium content most. Mixing iron ore tailings at all rates improved the potassium content in yellow leaf to the extent of 24.5%~87.3% higher than the control. In stem, adding the tailings at the rate of 10%, 20%, 50%, 60%, and 80% had little impact on the potassium content. While, at the mixing rate of 30% and 40%, the potassium content was significantly higher than the control and at 70% it was significantly lower. In root, all mixing rates except 10% increased the potassium content compared with the control. At 10% there was little difference between the experiment group and the control group. The highest potassium content of Gardenia jasminoides Ellis lay in green leaf and the lowest was in stem, indicating the order of green leaf>stem>root. In the control group, potassium in yellow leaf was higher than that in root. With the increase of mixing rate in experiment group, the opposite phenomenon was observed. However, the difference was quite little at the mixing rate of 40% and 50%. When it was higher than 60%, the order was again root> yellow leaf. TABLE.3. POTASSIUM CONTENT OF GARDENIA JASMINOIDES ELLIS AT DIFFERENT TAILING MIXING RATE (mg g-1) Mixing rate/% 0 10 20 30 40 50 60 70 80
Green leaf 13.64±1.11ae 15.10±0.42b 14.00±0.41ade 16.63±0.42c 14.93±0.00bd 14.95±0.41b 14.94±0.39b 13.38±0.70a 14.46±0.41be
Yellow leaf 8.05±0.81a 12.29±0.40b 15.07±0.77c 14.33±0.40c 12.24±0.40b 12.64±0.39b 9.54±0.00d 10.02±0.00d 10.40±0.73d
Stem 7.78±0.78ac 8.16±0.41abc 8.67±1.12ab 9.20±0.70b 9.07±0.42b 8.91±0.41ab 8.52±1.01ab 7.11±0.39c 8.71±0.40ab
Root 10.19±0.42a 10.48±0.42a 11.91±0.42b 13.46±0.42c 12.46±0.39bd 12.04±0.66b 12.30±0.00bd 12.07±0.39b 13.01±0.42cd
According to Figure 3, mixing iron ore tailings had a great impact on the allocation of potassium uptake in the aerial part and the root of Gardenia jasminoides Ellis as well. The potassium uptake of Gardenia jasminoids in aerial parts accounted for 51%~63% of the total potassium uptake. Comparing with the control, mixing iron ore tailing sands at the rate of 30% increased the proportion of potassium uptake in aerial parts, which was the highest among the experiment group. While the rate was 10%, 20%, 40%, and 50%, there was no significant difference between the two groups in aerial parts. When the rate was 60%~80%, the proportion of potassium was notably lower than the control. - 17 http://www.ivypub.org/fes
Ratio of K uptake in aerial parts/%
65 ac
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60
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50 0
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20 30 40 50 60 Percentage of iron ore tailings/%
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FIGURE.3. EFFECTS OF IRON TAILINGS ON THE ALLOCATION OF POTASSIUM UPTAKE ON GARDENIA JASMINOIDES ELLIS.
3.4 Effects of Application of Iron Ore tailing in Soil on Iron Content of Gardenia jasminoides Ellis Table 4 suggested that mixing iron ore tailing sands with experimental soil had a significant influence on the iron content of Gardenia jasminoides Ellis. When the iron content in green leaf was analyzed, the iron content of group with mixing rate of 20% and 40% was significantly higher than the control. And the group of 60% mixing rate had much lower iron content. The iron content in green leaf of rest groups were almost the same with the control. As for yellow leaf, 30%, 60%, 70% and 80% mixing rate increased the iron content in them. And the rest showed no significant difference. In stem, all mixing rates lowered the iron content except 30%, which did not influence iron content very much. In root, a marked increase of iron content was also observed in stem at the mixing rate of 10%. And iron content in root had little difference with the control at 80%. The rest were all significantly lower than the control. The highest Fe content of Gardenia jasminoides Ellis lay in root and the lowest was in stem, showing the order of green leaf>stem>root>yellow leaf. The iron content in root was 1.4~2.7 times that of the yellow leaf, 4.0~8.6 times that of the green leaf and 6.3~21.2 times that of the root. TABLE.4. FE CONTENT OF GARDENIA JASMINOIDES ELLIS AT DIFFERENT TAILING MIXING RATE (g g-1) Green leaf 239.62±0.00ac 224.56±0.00ac 297.47±26.00b 245.97±8.79c 279.20±14.09b 247.44±8.67c 188.24±8.26d 250.44±8.43c 223.48±17.03a Ratio of Fe uptake in aerial parts/%
Mixing rate/% 0 10 20 30 40 50 60 70 80
Yellow leaf 704.39±8.16a 727.78±8.32ac 716.55±29.16ac 807.81±8.30bd 709.13±8.44ac 721.32±21.82ac 840.60±38.12b 748.14±21.10cd 788.66±38.55d
30
Root 1711.4±8.9a 1930.8±30.2b 1194.9±8.7c 1193.7±8.8c 1382.2±8.2d 1018.1±8.0e 1325.7±31.2f 1171.8±14.1c 1685.7±17.6a
d c
25 20
Stem 171.83±8.89a 91.30±8.57bd 109.55±8.84bc 187.25±25.30a 103.42±15.16bd 131.48±14.91c 94.66±13.88bd 87.12±8.17bd 84.80±0.00d
c e
a
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15
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b 10 5 0 0
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20 30 40 50 60 Percentage of iron ore tailings/%
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FIGURE.4. EFFECTS OF IRON TAILINGS ON THE ALLOCATION OF FE UPTAKE ON GARDENIA JASMINOIDES ELLIS. - 18 http://www.ivypub.org/fes
According to Figure 4, mixing iron ore tailings had a remarkable effect on the allocation of Fe uptake in the aerial part and the root of Gardenia jasminoides Ellis as well. The proportion of the Fe uptake of Gardenia jasminoids in aerial parts only accounted for 9%~25% of the total Fe uptake. When the mixing rate was 20%~50%, the Fe uptake of Gardenia jasminoids in aerial parts was significantly higher than the control, among which 30% mixing rate was the highest. While the rate was 70%, there was no significant difference between the two groups in aerial parts. When the rate was 10%, 60%, and 80%, the proportion of was notably lower than the control.
4 DISCUSSION With the increasing demand for steel from all industries, the iron ore tailings discharged during mining are rising rapidly. The total iron ore tailings stacking in China are more than 5 billion tons and are growing at the speed of 500 million tons per year (He Yongguang & Wang Xiaolei. 2010). Though there are many techniques of resource utilization of iron ore tailings, such as recycling useful element (Li et al. 2010), used for manufacturing cement and building materials for decoration (Li et al. 2010; Zhao et al. 2014), composing special materials (Giri et al, 2011; Liu et al, 2010; Sakthivel et al, 2010; Yu et al, 2009), backfilling mine (Huang Yonggang. 2013), and constructing road (Li Ronghai et al. 2007) and so on, the efficiency is not very high due to the limitations of costs, marketing, transportation and other aspects. Therefore, the ratio of comprehensive resource utilization of iron ore tailings is less than 10% and only around 7%, which is much lower than that of developed countries. So exploring the resource utilization technology of iron ore tailing sands in China will bring about multiple meaning and value. This study showed that applying iron ore tailing to soil had an impact on the content and allocation of some nutrient elements in Gardenia jasminoides Ellis. Viewing from the content of nitrogen and phosphorus in the plant, there was hardly a regular pattern that could describe the phenomenon observed with the proportional increase of the rate of iron ore tailings. But in terms of nitrogen uptake, the mixing rate of 10%~40% was good for increasing the proportion of the nitrogen uptake of Gardenia jasminoids in aerial parts and the best result was at 30% mixing rate. When mixing rate was higher than 60%, it had the opposite effect. And mixing iron ore tailings at the rate of 20%~30% also increased the proportion of phosphorus uptake in aerial parts. 60% and above mixing rate reduced the proportion too. This showed that adding a certain percentage of iron ore tailings improved the proportion of nitrogen and phosphorus uptake in aerial part. So adding proper rate of iron tailings contributed to the transfer of the absorbed nitrogen and phosphorus to the aerial part, thus doing good to the growth of the aerial part. In terms of potassium content, the treatment of appropriate mixing rate of iron tailings was conducive to increase the content. Judging from all parts of the Gardenia jasminoids, adding the iron ore tailings at the rate of 30%~40% significantly increased the potassium content in all parts of the Gardenia jasminoids. Judging from the proportion of Fe uptake in aerial part, adding the iron ore tailings at the rate of 30% benefited most for the increase of this proportion. When the rate was over 60%, the proportion would decrease. Potassium is an advantageous element that not only benefits plant growth but also enhances plant oxidation resistance. The phenomenon observed above suggests that adding iron tailings not only benefits the plant growth but also improves plant oxidation resistance. Adding the iron ore tailings at the rate of 20%~50% increased the Fe content in green leaf. However, compared with the control, the Fe content in root and stem did not increase and even decreased with the rising of mixing rate. Meanwhile, the proportion of Fe uptake in aerial part increased, which suggests that adding iron ore tailings benefits the application of iron in green leaf and aerial parts of Gardenia jasminoids Ellis and translocation of Fe to aerial and tender parts. Since high mixing rate did not result in high Fe content in every part, the effectiveness of iron in iron ore tailings were really low and tailings did not jeopardize the growth of the plant. Gardenia jasminoids Ellis is hi iron plant and easily yellows due to iron deficiency. In this experiment, mixing iron ore tailing sands increased of Fe content of Gardenia jasminoids Ellis and improved the proportion of Fe uptake in aerial parts, thus contributing to preventing iron deficiency chrolosis. Study on the application of iron ore tailings in soil is rarely reported. Because the major component of iron ore tailings is sand, the 0.2~2 mm particles accounted for 81.5% in the tailings of this experiment. In southern mining areas of China, the soil texture is heavy clay. If large amount of soil of this kind is borrowed during the process of land reclamation and vegetation restoration, it is not conducive for plant growth and water and fertilizer management. So, studying the application of iron ore tailings in soil helps improve soil sticky and thereby coordinate its physical properties, making it better for plant growth. It can also reduce the costs of transportation and the damage to the - 19 http://www.ivypub.org/fes
landscape of the soil borrowing areas, by reducing the amount of borrowing soil. By utilizing iron ore tailings, the tailings stacked are reduced and the storage capacity of tailing pond is relatively expanded, which benefits the safety production and the sustainable development of the mine. The study indicated that the application of iron ore tailing sands to soil at proper rate helped improve the soil physical properties and regulate soil water and gas situation (Ji Lan et al. 2013). In some recent studies, iron ore tailings were directly used for vegetation restoration and were improved by adding other substances to grow plant. Study of Noyd et al (1996) showed that directly adding compost, mycorrhizal fungi, and fertilizer to iron tailing could promote plant growth and benefit vegetation restoration. Experiment in green house with tailings as substrate showed that the growth of different grasses was affected by mycorrhizal and phosphate and choosing native plants and native mycorrhizae was beneficial for the vegetation restoration on iron tailings areas. After the method of using solid waste as compost to improve the iron ore tailings in iron mine area of Minnesota, USA, the vegetation coverage reached 90%, four years later (Norland and Veith, 1995). Zhang Cuiqing et al (2010) carried out a pot experiment that alfalfa was planted in the iron tailing substrate added with different arbuscular mycorrhizal fungi. The result suggested that mycorrhizal fungi, especially that from copper tailings areas, could increase the enzyme activity in the matrix and promote the growth of alfalfa. The experiment that planting apple in the mining wasteland filled with the mixture of loamy and iron ore tailings demonstrated that plants grown in the filling depth of 1.0m were significantly better those in the filling depth of 0.5m (Guo Suoping et al. 2011). Zhang Jixian et al (1999) applied iron ore tailings and fly ash to red soil. Adding iron ore tailings and fly ash could enhance soil respiration, transferase activity and improve the physical properties and production of Sudangrass, compared withnthe control. Chaturvedi et al (2013) carried out a pot experiment that studied the effects of iron ore tailings on physiological activity of Maidenhair by mixing tailings with soil and determined some metal content. Their study showed that iron ore tailings could prompt the growth and the antioxidant enzymes activity of Maidenhair. The content of some elements in Maidenhair, including iron, increased with the increase of mixing rate of iron ore tailing. Our experiment showed that the iron content in Gardenia jasminoids Ellis did not increase with the increase of mixing rate of iron ore tailings and the performance varied in different parts. The highest iron content in green leaf appeared at 40%, in stem at 30%, in root at 10%, and in yellow leaf at 60%. Although the research methods resembled some studies above, our results were different. The main reason was that the vegetation type and soil type in our experiment were all different from them. Besides, the soil they use was acidic soil while our soil was slightly alkaline. The effectiveness of iron was higher than that of neutral and alkaline soil. Generally, each unit increase in soil reduces the concentration of iron by 1000-flod (Lv Yizhong, Li Baoguo. 2006). The high effectiveness of iron in soil would definitely result in the high iron content of plant. The levels of nitrogen, phosphorus and potassium within gardeniaâ&#x20AC;&#x2122;s green leaves were higher than its yellow leaves, indicating that nitrogen, phosphorus and potassium are elements of mobility and strong reuse in the body of gardenia, that is to say, nitrogen, phosphorus and potassium in yellow leaves could be transferred to the green parts so they could be reused, however, iron content within gardeniaâ&#x20AC;&#x2122;s yellow leaves were higher level than its green leaves, showing that the mobility and reuse of iron in the body of gardenia were weak, and parts of the aging iron cannot be transferred to other parts of it, therefore, it could not be reused. As the iron content of the various parts of gardenia did not increase with the rising proportion of iron ore tailing in soil, it showed no significant law. Besides, iron content within gardenia roots, in addition to the proportion of iron ore tailing in soil as 10%, was higher than the control, that means, in conditions of other proportion of iron ore tailing in soil, it was lower than the control, which indicated that on this condition of the soil under the experimental conditions, effectiveness of iron in iron ore tailings was low and difficult to be used by gardenia, so that iron in iron ore tailings will not produce toxic effects on the growth of gardenia. The reason why the level of root iron content of iron ore tailing soil was lower than the control would be that treatment of adding iron ore tailing in soil increased soil vent leading to enhancing degree of soil aeration, and the increase of soil aeration would reduce the effectiveness of iron, resulting in iron content in roots was lower than the control. But a certain percentage range of iron ore tailing added in soil was able to promote the absorption of root iron to transfer to the ground and the green parts, which was good for preventing gardenia from iron chlorosis disease, as well as being beneficial to promote the growth of gardenia. The proportion of uptake from nitrogen phosphorus, potassium, iron aboveground was affected by adding the proportion of iron ore tailings in soil, that is, appropriate proportion of iron ore tailings in soil is good for increasing - 20 http://www.ivypub.org/fes
the percentage of absorption of nitrogen, phosphorus, potassium, iron, which indicated the proper application of iron ore tailings in soil was helpful for gardenia nutrient to transfer to the ground, and it is relatively good for the growth of the aerial parts of gardenia, as a result, it is conducive to increase covering plants rapidly. On the whole, taking distribution of content and uptake of nitrogen, phosphorus, potassium and iron into accounts well as the test soil conditions, for the gardenia, the appropriate proportion of iron ore tailings soil application was 20% to 50%, the best ratio was 30%.
5 CONCLUSIONS 1). Mixing iron ore tailing sands with experimental soil had a significant impact on the nitrogen content of Gardenia jasminoids Ellis. The order of nitrogen content of Gardenia jasminoids was green leaf>root>stem>yellow leaf. When the mixing rate was 10%~40%, the proportion of nitrogen uptake in aerial parts was significantly higher than the control. 2). Mixing iron ore tailing sands with experimental soil had a great effect on the phosphorus content of Gardenia jasminoids Ellis. The order of phosphorus content of Gardenia jasminoids was green leaf>stem>root>yellow leaf. When the mixing rate was 20%~30%, the proportion of phosphorus uptake in aerial parts was notably higher than the control. 3). Mixing iron ore tailing sands with experimental soil had a notable influence on the potassium content of Gardenia jasminoids Ellis. The order of potassium content of Gardenia jasminoids was green leaf>root>stem. When the mixing rate was above 50%, the proportion of potassium uptake in aerial parts was remarkably lower than the control. 4). Mixing iron ore tailing sands with experimental soil at the mixing rate of 20%~50% contributed to the increase of Fe content of Gardenia jasminoids Ellis and the improvement of the proportion of Fe uptake in aerial parts. The order of Fe content of Gardenia jasminoids was root>yellow leaf>green leaf >stem. 5). Appropriate application rates of iron ore tailing in soil can accelerate the growth of gardenia by translocation of soil nutrients to aerial and tender parts. Therefore, according to the nutrient contents and the allocation of nutrient uptakes in gardenia, the suitable application rate of iron ore tailing in soil ranges from 20% to 50% and the most suitable rate is around 30%.
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