In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu.
Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. wangdan213@mails.ucas.ac.cn.|University of Chinese Academy of Sciences, 19 A Yuquan Road, Beijing 100039, China. wangdan213@mails.ucas.ac.cn.
Dan
D
Wang
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. gongmengdan14@mails.ucas.ac.cn.|University of Chinese Academy of Sciences, 19 A Yuquan Road, Beijing 100039, China. gongmengdan14@mails.ucas.ac.cn.
Mengdan
M
Gong
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. 15051895212@163.com.|School of Chemical Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Road, Nanjing 210094, China. 15051895212@163.com.
Yangyang
Y
Li
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, 1 Xikang Road, Nanjing 210098, China. hhuxulv@126.com.
Lv
L
Xu
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. yuyan19881116@163.com.|University of Chinese Academy of Sciences, 19 A Yuquan Road, Beijing 100039, China. yuyan19881116@163.com.
Yan
Y
Wang
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. rjing@niglas.ac.cn.|University of Chinese Academy of Sciences, 19 A Yuquan Road, Beijing 100039, China. rjing@niglas.ac.cn.
Rui
R
Jing
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. smding@niglas.ac.cn.
Shiming
S
Ding
International Network for Environment and Health, School of Geography and Archaeology, National University of Ireland, Galway, University Road, Galway H91 CF50, Ireland. Zhang@nuigalway.ie.
Chaosheng
C
Zhang
D002681:China; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000032:analysis*; D060106:Lakes / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000032:analysis*
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical
diffusive gradient in thin films; high resolution; in-situ; metals; relative mobility; sediment