1、1Heavy Metal Accumulation Characteristics of 3 Pioneer Plants in Wasteland of Coalmine Tailing in MinAbstract: Accumulation characteristics on 7 heavy metals of 3 indigenous pioneer plants (Ageratum conyzoides, Comnyza canadensis, Miscanthus floridulus) (2) the absorption and accumulation ability to
2、 the Ni, Cd, Cu, Pb, Zn, Mn and Cr of soil heavy metal among 3 indigenous pioneer plants Heavy Metal; Indigenous Pioneer Plants; Accumulation Characteristics Great wealth has been brought to human by the exploitation in mines. To eliminate the negative environmental effect in mining areas and speed
3、up soil reclamation, some staged theoretical and application results for soil reclamation and 3ecological reconstruction had been achieved in Chinas mining areas in the past two decades (Lengyi Li et al, 2004; Zhenqi Hu, 2009; Haichun Wang, 2009). However, soil reclamation in mining areas is a broad
4、, comprehensive and systematic project. Since the 21st century, a soil reclamation technology, which integrates the new advanced and mature environmental and biological technologies of all disciplines and is committed to the ecosystem health and environmental security in mining areas and restoring r
5、econstruction goal, has been increasingly emphasized with a gradual step in China (Deliang Liu et al, 2011). Phytoremediation is an environment-friendly and low-cost soil reclamation technology in mining areas. Based on previous researches, by taking Mingshan coal mine of Meizhou of Guangdong Provin
6、ce as research object, the heavy metal contents in the rhizosphere soil of 3 indigenous pioneer plants and the heavy metal accumulation characteristics of these plants were studied in this paper for finding and seeking heavy metal patience plants appropriate for local climate and soil conditions. Al
7、so, it is expected this study can provide a basis for the governance of polluted soil and ecological restoration in wasteland of coalmine tailing in Mingshan. 1 Materials and Methods 41.1 General Situation of the Investigated Area Mingshan coal mine (N23232456, W1151811656) is located in Mei County
8、of Guangdong province, and its average altitude is 550 m. It is in subtropical humid monsoon climate zone. In this area, the average annual temperature is 20.621.4; the average temperature in July is 28.328.6; the average temperature in January is 11.111.3; the average annual rainfall reaches 1483.4
9、1798.4mm and over 75% of the rainfall is concentrated in April-September; the frost-free period is 309 days. According to investigations (Fulin Liao et al, 2006), there have been 64 species of plants natural growing in the wasteland of coalmine tailing in Mingshan. According to the on-site investiga
10、tions in November-December 2010, some relatively stable monotypic patches and small colonies have grown in the wasteland of coalmine tailing in Mingshan, such as Ageratum conyzoides, Comnyza Canadensis, Miscanthus floridulus, Crotalaris mucronata and Artemisia argyi. Therefore, in selecting plants f
11、or the vegetation ecological restoration and governance in wastelands, top priority can be given to the indigenous pioneer plants successfully colonized in coal mine wasteland. 51.2 Sample Collection Samples were collected from the wasteland of coalmine tailing in Mingshan. Now, the north-to-south s
12、lopes and the east slope of this wasteland of coalmine tailing have leaned to be 45 and 60 respectively, and the west slope is gentle. Also, it is closer to a big ditch, and has been already abandoned for 1-5a. It is surrounded by low mountains, on which soil is red. In November 2010, considering th
13、e actual topography, coal gangues different accumulation years and hydrological condition in this wasteland, samples were collected according to distances by laying sampling line (centered on waste piles) along groundwater flow direction, and also sampling points (sample point 1, sampling points 2,
14、sample point 3, sample point 4, and sample point 5) were set on the 10m, 50 m, 100 m, 200 m, and 500m lengths of the sampling line respectively. Then, centered on each sampling points, pioneer species within 1m2 and the rhizosphere soil of 030 cm around these plants in the coal tailing were collecte
15、d; although the sample points 1 and 4 had no plants to grow, their soil of 030 cm were also collected. 1.3 Laboratory Analysis 1.3.1 Pre-processing of Samples 6Soil was dried in indoor air, and then grinded with an agate mortar after stones, plant roots and litters were removed, and then sieved with
16、 a 100-mesh (0.15mm) net, and then used for testing the heavy metal contents of soil. Plants were divided into three parts (i.e. root, stem and leaves), and then eluted with deionized water for three times, and then dried and ashing at 480 for 4h, and then used for testing the heavy metal contents.
17、1.3.2 Testing of Samples 7 heavy metal contents (Cu, Ni, Cd, Pb, Zn, Mn, detailed testing methods are shown in the paper of Yan Wang et al; soil sample was processed with HCl-HNO3-HF-HClO4 mixed acid digestion method; the testing of heavy metals of plants referred to the methods (Xiquan Wang, 2007;
18、Fanggong Sui, 2004), and plant samples were processed with ashing method; the concentrations of 7 heavy metal contents (Cu, Ni, Cd, Pb, Zn, Mn, pH value of soil was tested with glass electrode method (soil: water = 1.0: 2.5) (Liaoyuan Yang et al, 2010). 2 Result and Analysis 72.1 Analysis on 7 Heavy
19、 Metal Contents of Soil Heavy metal contents of the soil in wasteland of coalmine tailing changed greatly (see (figure 1). Cd content was 0.7593.109mg/kg (the average is 2.052 mg/kg); the Cd contents of the soil in two sampling points 4 and 5 were 10 times higher than the secondary soil standard and
20、 3 times higher than the tertiary soil standard (soil environment quality standards, GB 15618-1995). Cd content of the soil in the sampling point 1 was closer to over 9 times of the secondary standard and 2.5 times of the tertiary soil standard; Cd contents of the soil in the sampling points 2 and 3
21、 were low, but also exceeded the secondary standard, suggesting Cd content of the soil in the wasteland of coal tailing was seriously out of standard. Research of Tao Yu et al (2008) shows that pH value of the soil was an important factor of controlling the geochemical behaviors of heavy metal conte
22、nts (e.g. Cd); the increase of ion exchanges between harmful elements such as Cd may be exacerbated by the acidic environment (pH values of 5 sampling points were 2.876.16) of the soil in the wasteland of coalmine tailing in Mingshan, thus resulting in serious ecological risks. Cu content was 39.522
23、 270.308 mg/kg (the average is 91.281mg/kg). The Cu content of the soil in sampling 2 was 8270.308 mg/kg, which was 5 times higher than the standard of the secondary standard farmlands (50 mg/kg); Cu contents of other sampling points were closer to the secondary standard, suggesting Cu pollution exi
24、sted in some extent, but was not serious. In this study, the above result can be also proven by the fluctuating but nonlinear decreasing change of the heavy metal contents of the soil in all sampling points. The main reason for this result can be concluded as follows: the sampling point 4 was locate
25、d in the minus grade of mine terrain and the sampling point 5 was a low-lying pit, and therefore a large amount of leaching liquid and mine drainages were deposited in these places under the condition that coal gangue is naturally leaching, making heavy metal elements separated out of coal gangue, a
26、nd the leaching, transferring and depositing effects of heavy metal elements will make heavy metals of soil constantly accumulated. Therefore, heavy metal contents of the soil in the sampling point 5 were not low. 2.2 Analysis on 7 Heavy Metal Contents of Plants 2.2.1 Miscanthus Floridulus In the te
27、sted 7 heavy metal elements, the average contents of Cu, Ni, Cd, Pb, Zn, Mn, Cd contents in root, stem and leaf of the plant respectively reached 5.075 mg/kg, 2.560 mg/kg and 1.857 mg/kg, 1.5 times of the Cd content of the soil in terms of the average content. Overall, except Mn, heavy metal element
28、s absorbed and accumulated in the root of miscanthus floridulus were the most; heavy metal elements transferred and transported t to the upper parts of miscanthus floridulus were relatively less; heavy metal elements absorbed and accumulated in stem were minimum. Seen from correlation coefficient ma
29、trix of 7 heavy metals in Miscanthus floridulus (table 1), there were a significant negative correlation between Cd and Cr, between Pb and Cu, and between Cu and Ni, but there were a significant positive correlation between Pb and Mn, between Cu and Mn, and between Ni and Mn. Referring to the resear
30、ch of Shucai Zeng et al (2002) 10on the relationship between elements in plant, it is obvious that there were a cooperative effect between Cd and Cr, between Pb and Cu, and between Cu and Ni; Pb, Cu Mn, Zn and Cu contents of the plant were relatively high, but Cd and Cr contents were relatively low
31、(see figure 3). Seen from the heavy metal elements in root, stem and leaf of the plant, most heavy metal contents were absorbed and accumulated in leaf in general. Seen from the correlation coefficient matrix of 7 heavy metals in ageratum conyzoides (see table 2), Pb and Zn were extremely significan
32、tly in a positive correlation; there was a significantly positive correlation between Pb and Cu, between Cu and Zn/Mn, and between Ni and Zn/Mn. Obviously, there was a cooperative effect between heavy metal elements absorptions of ageratum conyzoides, and this is helfful for it to absorb more heavy metal elements
