title: Vertical distribution of acid-volatile sulfide and simultaneously extracted metals in mangrove sediments from the Jiulong River Estuary, Fujian, China.
abstract: BACKGROUND
  Acid-volatile sulfide (AVS) is operationally defined as sulfides in sediment, which are soluble in cold acid, and is reported as the most active part of the total sulfur in aquatic sediments. It is a key partitioning phase controlling the activities of divalent cationic heavy metals in sediment.
  
  
  METHODS
  In order to examine this in mangrove environments, six sites were selected along the Jiulong River Estuary in Fujian, China, which had previously been reported to be polluted by heavy metals. Sediments were sampled from 0-60 cm depth at each site, and the spatial distribution of AVS and SEM (simultaneously extracted metals: copper, cadmium, zinc, and lead) were determined.
  
  
  CONCLUSIONS
  The results indicate that the AVS concentrations had a spatial variation, ranging from 0.24 to 16.10 pmol g(-1) sediment dry weight. The AVS concentration in the surface layer is lower than that of the deeper sediment, with peak values in the 15-30 cm horizon. There was no correlation between the AVS value and organic matter content or total dissolved salts, but a significant positive correlation of AVS with surface sediment (0-5 cm) moisture content was found. This indicates that water logged sediments tend to have a high AVS value. The amount of SEM was within the range of 0.33-2.80 micromol g(-1) sediment dry weight and decreased with sediment depth.
  
  
  CONCLUSIONS
  There was a marked variation in AVS and SEM among different sites studied. AVS concentrations were generally lower in the surface sediments, while SEM concentrations slightly decreased with the depth. Higher concentrations of SEM found in the upper layers of the sediments confirm the earlier suggestions that this study area may suffer from increasing heavy metal pollution.
  
  
  CONCLUSIONS
  When monitoring environmental impacts by using AVS, the micro and large-scale spatial variation as well as vertical distribution need to be estimated to avoid misleading results. Both AVS and SEM concentrations in different sediment layers should be taken into account in assessing the potential impact of heavy metals on the biotic environment,
authors.affiliation: School of Life Science, Xiamen University, Xiamen, Fujian 361005, China.
authors.forename: Jingchun
authors.initials: J
authors.lastname: Liu
authors.forename: Chongling
authors.initials: C
authors.lastname: Yan
authors.forename: Mark R
authors.initials: MR
authors.lastname: Macnair
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
mesh_terms: D032407:Avicennia; D002681:China; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D019216:Metals, Heavy / Q000032:analysis*; D043982:Rhizophoraceae; D045483:Rivers; D013440:Sulfides / Q000032:analysis*; D014835:Volatilization; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D019216:Metals, Heavy; D013440:Sulfides; D014874:Water Pollutants, Chemical