Source quantification and potential risk of mercury, cadmium, arsenic, lead, and chromium in farmland soils of Yellow River Delta

Accumulation of pollutants, especially heavy metals in river delta systems, pose a severe threat to the ecological environment and also hinder sustainable development of deltas. A total of 390 samples were collected from farmlands throughout the Yellow River Delta (YRD), the fastest growing delta in the world, to explore the holistic distribution characteristics and restrictive environmental factors of mercury (Hg), cadmium (Cd), arsenic (As), lead (Pb), and chromium (Cr) in the soil. Results indicated that soils in farmlands at the YRD had relatively low average concentrations of selected elements with non contamination level. This is due to low elemental contents of loess parent materials and less human activities. These elements in soils had distinct spatial distributions and disparities from different categories, which were predominately determined by soil physicochemical properties such as cation exchange capacity, organic matter content, clay fraction and soil acidity. Sodium salt played a vital role in this delta for soil salinization. Agricultural inputs, industrial emissions, and river suspended sediments were the three primary sources of these elements. Of these elements, 65% of Hg came from atmospheric deposition, 66% of Cd was sourced from industrial emissions, 53% of As and 46% of Pb originated from agricultural inputs, and 64% of Cr was rooted from parent materials. Based on these findings, critical strategies including controlling the agrochemical input and removing industrial pollutant emission were proposed for sustainable development of the YRD. (C) 2019 Elsevier Ltd. All rights reserved.