Accelerated carbonate dissolution caused by anthropogenic acidification — contrast of watershed soils to lake sediments in Taihu Region, China

• Published in: Environmental science and pollution research international Vol. 29; no. 55; pp. 83733 - 83745
• Main Authors: Tao, Yu, Binyang, Jia, Rui, Wang, Yixiang, Deng, Xiaoke, Zhuo, Zhonghua, Cheng, Chengda, He
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2022; Springer Nature B.V
• Subjects: Acid deposition; Acidic soils; Acidification; Algae; Algal blooms; Anthropogenic factors; Aquatic ecosystems; Aquatic environment; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Buffers (chemistry); Calcium; Carbonates; Deposition; Dissolution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Eutrophication; Fertilization; Human influences; Lake sediments; Lakes; Land use; Magnesium; pH effects; Pollutant deposition; Research Article; Sedimentation; Sedimentation & deposition; Sediments; Soil chemistry; Soil investigations; Soil pH; Soil surfaces; Soils; Topsoil; Upstream; Vegetables; Waste Water Technology; Water chemistry; Water Management; Water Pollution Control; Watersheds; Wetlands; Wheat; Acidification; Carbonates; Taihu Watershed; Ecosystem; Soil and sediment
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-022-21741-6

Although Taihu watershed is an “acid-insensitive” region, anthropogenic acidification has greatly changed the water chemistry in Taihu Lake. However, how soil carbonates responded to the long-term human-induced acidification received less attention. In this work, we investigated soil carbonate concentrations from different land uses in the upstream of the lake and sediment carbonate profiles in the lake, to explore the linkage of carbonates dissolution in the land and sedimentation in the lake. The result showed that the wheat-rice surface soil, the most acidification-impacted by fertilization and acid deposition, had significantly lower pH than vegetable and wetland soils ( p  < 0.05). Meanwhile, the carbonate concentration in wetland soils, only impacted by acid deposition, was significantly higher than that in wheat-rice and vegetable soils ( p  < 0.05). The pH profile of fertilized soils, with an increasing trend from the surface to bottom, further indicated the acidifying effect of fertilization. Although the average soil pH across all land uses was 6.6 in the upstream of the lake, remaining carbonate buffering system, the significant carbonate decrease especially in surface soils evidenced the definite carbonate dissolution by acidification, which is cumulative and irreversible. Contrary to the topsoils, the sediment carbonate concentration presented an increasing trend from the depth of 15 cm (denoting around the early 1980s) to the surface, indicating that lake sediment is a major sink of carbonate Ca and Mg from the watershed, particular under an alkaline lake environment caused by frequent algae blooms in the past decades. In addition, Ca/Mg ratio in the sediment, having higher values in a higher pH environment, was quite different from the watershed soil pattern, suggesting different biogeochemical processes Ca and Mg underwent during their transportation and sedimentation. The effects of acidification-altered re-distribution of carbonate Ca and Mg and Ca/Mg ratio in the terrestrial and aquatic environments deserve wider considerations of ecosystem consequence.