TROPICAL GEOGRAPHY ›› 2018, Vol. 38 ›› Issue (6): 836-847.doi: 10.13284/j.cnki.rddl.003083

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Comparison of Heavy-metal Pollutions, Accumulation and Transfer Capacity between Artificial and Natural Mangroves in the Hainan Island

QIU Penghua1, WANG Dezhi2, XIE Genzong1, XU Songjun3, CAO Rui1, WANG Junguang1   

  1. [1.College of geography and Environmental Sciences, Hainan Normal University, Haikou 571158, China;2. Faculty of Information Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China;3. College of Geography, South China Normal University, Guangzhou 510631, China]
  • Online:2018-11-30 Published:2018-11-30

Abstract: The Muller indices, potential ecological hazard coefficients, biological accumulating coefficients (BAC) and the biological transfer coefficients (BTC) of 6 heavy metals (Cd, As, Cu, Cr, Pb and Zn) are compared between artificial and natural mangroves in mangrove nature reserves of Dongzhaigang, Qinglangang, and Sanya River, in Hainan Island. The results show that: 1) In the mangrove sediments of the study area, Cd has the higher intensity - extreme intensity pollution, As is moderate-intensity pollution, Cr is basically moderate pollution, Zn is mild pollution, Cu and Pb show no or slight pollution. In spatial distribution, the pollution of Cd is shown as: Dongzhaigang (intensity-extreme intensity) > Qinglangang (intensity) > Sanya River (pollution-free), the pollution of As is as follows: Qinglangang (moderate - intensity) > Dongzhaigang (moderate - intensity) > Sanya River (moderate); and the pollution of Cr is Dongzhaigang (moderate) > Qinglangang (mild) > Sanya River (no pollution). 2) The values (the potential ecological hazard coefficients of a single heavy metal) of Cd in artificial Sonneratiaapetala, natural Avicennia marina, artificial and natural Aegicerascorniculatum, artificial and natural Bruguierasexangula of Dongzhaigang are strong potential ecological risk, while the values of Cd in natural Rhizophoraapiculata Blume of Dongzhaigang and Qinglangang,artificial Sonneratiaapetala and natural Sonneratia alba of Qinglangang belong to medium potential ecological risk. The values of residual mangrove plants and RI values (the total potential ecological risk index of heavy metals) of all mangrove plants are all of slight grade. Generally speaking, it seems that Cd, As, Pb and Cr are more likely to cause health risks of Bruguierasexangula, Sonneratiaapetala and Aegicerascorniculatum. 3) The BAC of 6 heavy metals in artificial and natural mangrove plants show: root > branch > leaf, and the general trend of BAC is the artificial mangrove of Sanya River > the natural mangrove of Sanya River > the natural mangrove of Qinglangang > the natural mangrove of Dongzhaigang > the artificial mangrove of Qinglangang > the artificial mangrove of Dongzhaigang. 4) The BTC of heavy metals in artificial and natural mangrove are leaf-branch > branch-root > leaf-root, and the general trend of BTC is the artificial mangrove of Sanya River > the natural mangrove of Sanya River > the natural mangrove of Dongzhaigang > the artificial mangrove of Dongzhaigang > the natural mangrove of Qinglangang > the artificial mangrove of Qinglangang. 5) There is a significant positive correlation in heavy metal contents between mangrove plants and the sediments under the plants. This indicates that controlling the heavy metal content and exogenous pollution of the sediments is an important and effective way to maintain the health of the mangrove wetland ecosystem. 6) The ability of mangrove plants to accumulate heavy metals in the same area is slightly stronger than that in natural forests. That may be related to the afforestation environment and human disturbance of artificial mangrove forestation.

Key words: natural mangrove, artificial mangrove, heavy metals, accumulation and transfer, Hainan Island