红树林湿地沉积物中AVS-SEM与重金属分布特征——以珠江口淇澳岛为例

Distributions of AVS-SEM and heavy metals in mangrove sediments:A case study at Qi'ao island in the Pearl River estuary

红树林湿地沉积物的独特理化性质使其能够大量富集河口重金属,为了研究珠江口湿地沉积物中AVS-SEM与重金属的分布特征及影响因素,采用重铬酸钾氧化-还原容量法、并联氮载气冷法酸溶硫化物分析法、等离子体发射光谱法及X射线荧光光谱法等分析了淇澳岛红树林不同生境下沉积物柱状样的基本理化性质、酸可挥发性硫化物(AVS)、同步浸提金属(SEM)含量及重金属总量.结果表明,AVS含量的垂向变化范围为0.53～50.47μmol·g-1,且不同采样点AVS垂向分布差别较大.相关性分析表明,AVS可能是Cd和Pb的主要结合相,AVS与pH、有机质、细粉砂、中粉砂含量呈正相关关系,与氧化还原电位Eh、粘粒含量呈负相关关系.沉积物中酸提重金属总量(∑SEM)范围为1.613～5.301mg·kg-1.不同生境下不同深度的∑SEM分布表明,5#互花米草样地0～15cm层、2#老鼠簕样地15～35cm层可能具有较大的潜在生态风险,而秋茄样地沉积物中的∑SEM潜在生态风险最小.沉积物中不同重金属总量大小顺序为:Zn>Cr>Cu>Pb>Ni>Cd,其中,Cd含量低于海洋沉积物Ⅰ类标准,而Zn、Cr、Cu、Pb含量均超过Ⅰ类标准,但尚未超过Ⅱ类标准.沉积物表层(0～5cm)重金属总量在不同生境下的大小顺序为:2#老鼠簕>1#无瓣海桑>7#芦苇>5#互花米草>4#光滩>6#无瓣海桑>3#秋茄.相关性分析表明,Ni、Cu、Zn、Pb、Cr在沉积物中具有相似的行为及来源,而Cd可能存在其它来源.

The physical and chemical characteristics of Mangrove wetland sediments are unique in their ability to enrich a large amount of heavy metals.Sediment core samples under different habitats were collected from the mangrove wetland on Qi＇ao Island in the Pearl River estuary and the basic physical and chemical properties,including acid volatile sulfide （AVS）,simultaneously extracted metals （SEM） and total heavy metals,were analyzed.The AVS contents in the vertical direction varied greatly,ranging from 0.53 to 50.47μmol·g-1.Correlation analysis suggested that AVS was the main phase of both Cd and Pb.AVS was positively correlated with pH,organic matter,fine silt,silt,while negatively correlated with Eh and clay.The total concentration of acid extracted metals in sediments （ΣSEM） ranged from 1.613 to 5.301 mg·kg-1.The contents and distribution of ΣSEM at different depths showed that 5# Spartina alterniflora （0～15 cm）,2# Acanthus ilicifolius （15～35 cm） might have greater potential ecological risks,but 3# Kandelia candel might have the lowest risk.The total contents of heavy metals in the sediment were in the order of Zn Cr Cu Pb Ni Cd.The Cd content was below the ClassⅠ marine sediment quality standard,while Zn,Cr,Cu,Pb contents exceeded ClassⅠ but were below ClassⅡ.The total contents of heavy metals in the surface sediments（0～5 cm） under different vegetation were in the order of 2# Acanthus ilicifolius 1# Sonntratia apetala 7# Phragmites communic 5# Spartina alterniflora 4# Tidal flat 6# Sonntratia apetala 3# Kandelia candel.Correlation analyses showed that Ni,Cu,Zn,Pb,Cr in the sediment had similar behavior and sources except Cd.