Deciphering centurial anthropogenic pollution processes in large lakes dominated by socio-economic impacts

Qi Lin (1) , Ke Zhang (1) , Enfeng Liu , Pierre Sabatier (2) , Fabien Arnaud (2) , Ji Shen (3)

1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, People's Republic of China
2 EDYTEM - Environnements, Dynamiques et Territoires de Montagne
3 School of Geographic and Oceanographic Sciences

Human activities have greatly increased the influx of pollutants into global freshwater ecosystems.Understanding the pollution patterns at multi-decadal scales, and how the socio-economic developmentand public policy have shaped them, are crucial to assess the current status of environmental quality anddevelop sound strategies for watershed management. This study takes the test case of large Taihu Lake(2,338 km2) in rapidly developing regions of China, to examine the temporal-spatial patterns anddriving factors of centurial trace metal and metalloid contamination. Using comparative sedimentaryrecords, we applied multiple geochemical indices and positive matrix factorization modelling to identifythe anthropogenic versus natural sources and their contributions. Results identified cadmium, antimonyand lead as typical pollutants, with high anthropogenic contribution rates of 58–79 %, 54–62 % and 28–36%, respectively. Contamination histories were asynchronous across the lake, starting from the 1940s(North) to mid-1990s (East), following the gradient of socio-economic stressors of the sub-basins.Specifically, industrial and agricultural inputs through runoff and river networks were main sources ofmetal in the northern and western lake parts, accounting for70 % since the 1980s. In contrast,aquaculture and agriculture related sources (80 %) dominated in Eastern Taihu Lake over the lastdecade. Moreover, atmospheric metal deposition from nearby industrial cities significantly affected thenorthern parts of the lake. The stationary and/or slightly decreased contamination trends, especially after2000 AD, shed light into the effectiveness of recent environmental regulation. Ourfindings suggest,however, that agricultural non-point sources and legacy effects probably delayed reductions in the inputof pollutants. Sustainable management of similar large watersheds worldwide, therefore, would benefitby highlighting the role of multiple anthropogenic sources, legacy contamination and lake-specificresponse

Domaines: Interfaces continentales, environnement; Milieux et Changements globaux; Géochimie; Stratigraphie

Qi Lin, Ke Zhang, Enfeng Liu, Pierre Sabatier, Fabien Arnaud, et al.. Deciphering centurial anthropogenic pollution processes in large lakes dominated by socio-economic impacts. Anthropocene, 2020, 32, pp.100269. ⟨10.1016/j.ancene.2020.100269⟩. ⟨hal-03164392⟩