海南岛人工与天然红树林重金属污染、富集与转运能力比较

以海南岛东寨港、清澜港与三亚河3个红树林自然保护区为研究区，综合比较了人工与天然红树林6种重金属（Cd、As、Cu、Cr、Pb和Zn）的地累积指数、潜在生态危害指数、生物富集系数与转运系数的差异。结果表明：1）研究区红树林沉积物中，Cd呈现强度—极强度污染，As为中度—强度污染，Cr属中度污染，Zn为轻度污染，Cu与Pb表现为无至轻度污染；从区域空间看，Cd污染表现为：东寨港（强度—极强度）＞清澜港（强度）＞三亚河（无污染），As污染表现为：清澜港（中度—强度）＞东寨港（中度—强度）＞三亚河（中度）；Cr污染表现为：东寨港（中度）＞清澜港（轻度）＞三亚河（无污染）。2）东寨港人工无瓣海桑、天然白骨壤、人工与天然桐花树、人工与天然海莲，清澜港的天然桐花树Cd的值（单一重金属潜在生态危害系数）属较强潜在生态风险，东寨港与清澜港的天然正红树林、清澜港的人工无瓣海桑、天然杯萼海桑和天然海莲Cd的值属中等潜在生态风险，其余红树植物6种参评元素的值与RI值（多重金属总潜在生态风险指数）均属轻微级；综合而言，Cd、As、Pb和Cr似乎更易引发海莲、桐花树与无瓣海桑的健康风险问题。3）人工与天然红树植物各器官对6种参评重金属的富集系数大体表现为：根＞枝＞叶；红树植物植株平均富集系数总趋势为：三亚河人工红树林＞三亚河天然红树林＞清澜港天然红树林＞东寨港天然红树林＞清澜港人工红树林＞东寨港人工红树林。4）人工与天然红树林的重金属转运系数都显示出：叶—枝＞枝—根＞叶—根；植株平均转运系数总趋势：三亚河人工红树林＞三亚河天然红树林＞东寨港天然红树林＞东寨港人工红树林＞清澜港天然红树林＞清澜港人工红树林。5）红树植物与林下沉积物重金属含量之间具有强的正相关关系，这表明控制沉积物重金属含量和减少外源重金属污染是维护红树林湿地生态系统健康重要而有效的环节。6）同一地区同种红树植物在吸附重金属能力上人工林略强于天然林，这可能与人工红树林的营林环境、人为扰动存在一定关联。

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

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.