The Absorbing Capacity Of Liquidambar Formosana And The Soil Remodeled Of Heavy Metal Pollution

Nanjing Qixia Mountain Lead-zinc-silver polymetallic deposit is a large lead-zinc-silver mineral deposit with the most reserves in the South China area currently, with an area of 25 km2. This mineral deposit is situated in the well-known Qixia Mountain Scenic Spot in the suburb of Nanjing City and is only 1.5km away from the Yangtze River in the north. The issue about the environmental damage arising from mining operation in the area was very serious in 1980s. By integrating with the existing researches and the current experiment on the atmosphere and soil environment in the area, it is found the As, Pb, Cd and Cr and other important heavy metals' content in the Imperial Garden of Qixia Temper and Taohua Lake near to the exhaust well of tunnels in the mining area is over 10-100 times of that of non-polluted soil, which belongs to the serious heavy metal pollution. How to recover the soil biological system damaged by the waste mine efficiently and solve the serious heavy metal pollution problem has become a severe environmental issue in our country and the whole world.In view of the situations said above, I takes Liquidambar formosana that distributes widely in Qixia mining area and has strong resistance as the research object to conduct the relevant researches based on the large-sized field investigation on Liquidambar formosana colony in Qixia mining area and indoor experiments, with the main research results to be obtained as follows:1.Upon the investigations on plant resources and based on the important values, the main arbor species in Qixia mining area are found as follows, i.e.: Liquidambar formosana, Ailanthus altissima, Kalopanax septemlobus, Pterocarya stenoptera Quercus variabilis and Quercus acutissima. By taking the absorbing coefficient (Kf) as the judging standard to compare the pollution-absorbing capacity of the six trees, a sequence is found as follows, i.e.:Liquidambar formosana, Ailanthus altissima, kalopanax septemlobus, Pterocarya stenoptera, Quercus variabilis and Quercus acutissima.2. Compare the pollution-absorbing capacity of Liquidambar formosana with different ages in the same growing environment in Qixia mining area with the Duncan' SSR and LSD (least significant difference), and the result shows the Liquidambar formosana colony, growing in the environment where the soil is seriously polluted by heavy metals, has a sequence for the absorbing capacity (from big to small) as follows, i.e.:of 30 years old> of 40 years old> of 20 years old> of 50 years old≌of 10 years old≌of 70 years old. Meanwhile, the heavy metal content in the Liquidambar formosana aged between 20～30 years old and 30～40 years old is obviously different from that of Liquidambar formosana with other ages. The pollution-absorbing capacity of the Liquidambar formosana aged between 20～40 years old is the strongest, but the one in other ages is comparatively weak and has no obviously difference.3. By analyzing the annual ring of trees with the WINDENDROTM2005a annual ring analyzer, the historical increment of diameter of a cross-section of the Liquidambar formosana can be obtained. Upon the study on the historical increment data of the Liquidambar formosana of different ages, it is found the cross-section increment of the Liquidambar formosana aged between 20～30 years old and 30～40 years old is the largest. By comparing the heavy metal content in the corresponding annual rings with the historical cross-section increment of the Liquidambar formosana aged 50 years old, it is found the one between the ages of 20～30 years old and 30～40 years old increases quicker.4. By measuring the 7 elements of Cr, Cu, Fe, Mn, Ni, Cu and Zn in the current root soil and the annual ring of 7 Liquidambar formosana of 30 years old and 8 Liquidambar formosana of 40 years old in Imperial Garden of Qixia Temper, it is found the chemical element content in the annual ring and the current root soil meets the logarithm linear associative mode, i.e.: lgC'=algC+b (where "C" is the content of chemical elements in annual ring, " C " is the content of corresponding elements in root soil). In accordance with the "C" (i.e.:the element content in annual ring), the year sequence in which the element content of the Liquidambar formosana evolves in soil environment can be re-modeled.As a result, it is found the Liquidambar formosana aged between 20～40 years old is beneficial to absorb the heavy metal elements in soil in the waste mining area in Qixia Mountain and other areas with the similar conditions, and the manual Liquidambar formosana forest is beneficial to beautify ecological environment.