Abstract
Over the past century, the impacts of human activities on the natural environment have continued to increase. Historic evolution of the environment under anthropogenic influences is an important reference for sustainable social development. Based on the geochemical analyses of a short sediment core of 49 cm from Lake Balkhash, the largest lake in Central Asia, potential factors historically influencing geochemical variation were revealed, and influences of human activity on regional environmental change were reconstructed over the past 150 years. The results showed that the dominant factor inducing changes in potentially toxic elements (V, Cr, Co, Ni, Zn, Cu, Cd, and Pb) is the physical weathering of the terrestrial materials. The variation in Ca content was influenced by the formation of authigenic carbonate. Since 1930, potentially toxic elements (Cr, Co, Ni, Zn, Cu, Cd, and Pb) in the lake sediments have obviously been affected by human activities, but the impact of human activities has not exceeded that of natural terrestrial weathering. In particular, the enrichment factors (EFs) for Cd and Pb reached 1.5. The average ecological risks of Cd were higher than the criterion of 30, suggesting a moderate risk to the local ecosystem in recent years. Total risk indices indicated moderate potential ecological risk for the lake ecology. The results will provide support for the environmental protection and better management practices of the Lake Balkhash watershed.
Highlights
As element composition in lake sediments is generally derived from weathered rock, eroded soil, and anthropogenic inputs, it has been widely used to study environmental change for the reconstruction of human impacts [1,2,3,4]
This paper focused on the scientific hypothesis of whether the potentially toxic elements in the sediments of Lake Balkhash are enriched by human activities over time, and different from those in the adjacent area under the background of significant enhancement of human activities
The sedimentation rate was determined to be 3.4 mm a−1, which is consistent with the results reported for the northern part of Lake Balkhash by Endo et al [40]
Summary
As element composition in lake sediments is generally derived from weathered rock, eroded soil, and anthropogenic inputs, it has been widely used to study environmental change for the reconstruction of human impacts [1,2,3,4]. Further study of the geochemistry of elements in lake sediments is needed to better understand the evolution of the physical geographical environment under the influence of human activities [8,9]. The environmental responses of Lake Balkhash to the increasing human activity in the region are not yet well understood. Previous studies on the sediments of Bosten Lake [20], Ebinur Lake [21], and Chaiowpu Lake [22] have indicated what influence human activities have had on other arid regions of China adjacent to Lake Balkhash with similar natural conditions; spatial differences in the response to global change still need to be explored
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