TROPICAL GEOGRAPHY ›› 2019, Vol. 39 ›› Issue (3): 347-356.doi: 10.13284/j.cnki.rddl.003132

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Accumulation and Migration of Heavy Metals in Mangrove Sediments and Plants in the Nanshan Town, Xuwen

Luo Songying, Liang Yiqiong, Chen Bishan, Lin Mengting, Liang Jiaxin and Qiu Jinkun   

  1. ( Department of Geography, Lingnan Normal University, Zhanjiang 524048, China )
  • Received:2018-12-13 Revised:2019-04-18 Online:2019-05-05 Published:2019-05-05

Abstract:

In the present study, we investigated the distribution, accumulation, and migration of heavy metals in mangrove sediments and plants in Nanshan Town of Xuwen County. The mangrove sediments and different parts of mangrove plants (roots, stems, and leaves) were collected, and their heavy metal contents were determined and analyzed using enrichment factors, bioaccumulation factors, transfer coefficients, and correlation analysis. The results showed that: 1) The heavy metal content in the sediments of mangrove wetland exhibited the order Cr>Zn>Ni>Cu>Pb>As>Hg>Cd, with a moderate degree of variation. Except Ni, the other seven heavy metals did not exceed the national first-class standard, and except Pb, the other seven heavy metals exceeded the background value of soil environment in Guangdong Province, indicating the existence of a certain accumulation effect in the process of heavy metal deposition in the study area. 2) The Enrichment Factors of As, Cu, Zn, Hg, Ni, and Cr in the sediments were greater than 1.5, indicating a potential effect of slight human activities. The Enrichment Factors of Ni were greater than 5 at each station. Combined with the background of the study area, it reflected that the Ni content was affected by both natural and human inputs. 3) The heavy metals were mainly concentrated in the roots of Avicennia marina, but were relatively uniform in the roots, stem, and leaves of Rhizophora sty losa. The contents of heavy metals in different parts of A. marina were much higher than those in the corresponding parts of R. sty losa, indicating that the heavy metal adsorption capacity of A. marina was stronger than R. sty losa. Hg was concentrated in the leaves of plants, and the correlation between Hg and other heavy metals was not obvious, indicating that they had different sources. It was speculated that Hg mainly enters the plants through leaves, mostly from transportation pollution through atmospheric deposition. 4) Different mangrove plants exhibit different enrichment abilities for different heavy metals. The enrichment ability for different heavy metals followed the order Cd>As>Cu>Zn>Hg>Pb>Ni>Cr in A. marina and Cd>Cu>Hg>Zn>Pb>As>Ni>Cr in R. sty losa. Both A. marina and R. sty losa had strong transport capacities for Hg. Rhizophora sty losa has a strong ability to enrich and transport Cd, whereas A. marina has a strong ability to enrich Cd, but a weak ability to transport Cd, indicating that there is no direct relationship between the accumulation and transport capacity of heavy metals in mangrove plants.

Key words: sediment, enrichment, Transfer Coefficient, heavy metals, mangrove plants, Nanshan Town of Xuwen County