Riverbed Sediment Project

Innovation and Application of Technologies for Investigating Heavy Metal Contamination in Sediments

1. Project Overview

　　In recent years, an increasing number of heavy metals have been employed in modern industry. Owing to the challenges of monitoring and the inadequacies of environmental protection legislation, the discharge of heavy-metal‑containing wastewater by enterprises has been rising annually. Consequently, many rivers and lakes are experiencing severe heavy‑metal contamination that far exceeds regulatory limits, drawing close attention from government authorities. The Shandong Provincial Government has consistently prioritized pollution prevention and control in key river basins; based on a preliminary survey of provincially monitored waterways, nine river segments were identified in December 2015 as the first batch for remediation.

　　China National Chemical Corporation Shandong Institute seized market opportunities by innovatively applying its traditional geological exploration expertise to the assessment of riverbed sediments. Through systematic experimentation and refinement, it has developed a comprehensive technical framework encompassing surveying and mapping, geophysical prospecting, hydro‑engineering and environmental investigations, sampling, laboratory analysis, remediation and restoration, and pollution source tracing. Among the first batch of nine rivers in Shandong Province undergoing heavy‑metal contamination remediation, the Institute leveraged this unique, proprietary technical system to successively win contracts and undertake sediment‑heavy‑metal contamination assessment projects for eight of them. Six of the resulting assessment reports for these eight rivers scored above 90 points, earning high praise as outstanding documents. Verification through dredging operations conducted by implementing contractors confirmed an accuracy rate exceeding 85%, garnering unanimous acclaim from environmental authorities, remediation contractors, and expert reviewers. This work provides a robust scientific basis for subsequently determining, in a well‑informed manner, the machinery and operating parameters for dredging, the appropriate dredging depth, and the most effective methods for treating and disposing of contaminated sediments.

2. Project Outcomes

　　According to the assessment by the China Petroleum and Chemical Industry Federation, this achievement has marked a major breakthrough in the remediation of heavy-metal contamination in sediment. It can be widely applied to the treatment of heavy-metal pollution in sediments across various water bodies, including rivers, lakes, coastal mudflats, and seepage pits, and its overall performance has reached an internationally leading level.

　　1) For the first time, traditional geological exploration methods were applied to the assessment of heavy metal contamination in bottom sediments, resulting in a comprehensive exploration methodology comprising six components: topographic mapping, spatial distribution surveys, hydrogeological and environmental investigations, pollution characterization, grain-size analysis and speciation studies, and source‑tracing. This approach has filled a critical gap in China’s capacity for investigating heavy metal contamination in bottom sediments.

　　2) Innovatively applied geophysical methods, such as high-density electrical resistivity tomography and differential electrical sounding, to investigate the distribution of riverbed sediments, characterize the subsurface stratigraphy of the river channel, and delineate the spatial extent of sediment deposits, thereby overcoming key technical challenges in sediment‑distribution mapping.

　　3) By establishing first- and second-order stratified cross‑sections for investigation, the spatial and vertical distribution of pollutants can be elucidated in detail; the particle-size distribution patterns of sediment within heavy‑metal‑contaminated riverbeds—whether composed of clay, sand, or a mixture of both—have been revealed, laying the groundwork for selecting appropriate remediation technologies; when integrated with source‑tracing studies, this approach enables identification of the primary sources of heavy‑metal contamination in surface waters and their underlying sediments.

3. Application and Promotion Status

　　The exploration‑technology framework has been successfully promoted and applied in sediment‑remediation projects targeting heavy‑metal contamination in riverbeds across several regions, including the Yantai area of Shandong Province (Huanglei River, Shuidao East River, Luojiatun River), the Rizhao area (Shu River), and the Weifang area (Yuh River, Hanting section), as well as in seepage pits and ditches in Dacheng County, Langfang, Hebei. Notably, remediation work on the Shu River in Rizhao and the Xinxue River in Zaozhuang is currently underway, guided by the findings of the preliminary investigations. Meanwhile, the restoration projects for the Jiehe, Huanglei River, Shuidao East River, and Luojiatun River in the Yantai region, along with the B‑section of the Yuh River in the Weifang region, have been completed, yielding excellent results and recreating an ecological landscape characterized by unobstructed waterways, clear waters, lush banks, and thriving fish.