Study On Aquatic Sediment Quality Criteria For Heavy Metals

Metals and organic chemicals have contaminated most of rivers and lakes in the last 50 years. Due to their widespread release and persistent nature, metals such as cadmium, copper, mercury, nickel, lead and zinc are commonly elevated in aquatic sediments. These metals can poison benthic organisms that ingest particles of contaminated sediments. In addition, they can be released into overlying and pore waters to affect nonbenthic organisms. Thus, sediment toxicity concerns have historically focus of aquatic environmental protection and assessment activities in the world. The current water quality assessment guideline laid down by United Nations Environment Program (UNEP), United Nations Educational, Scientific and Cultural Organization (UNESCO) and World Health Organization (WHO) emphasizes the momentous significance of sediment quality. Many countries or regions including America, Canada, Australia and Hong Kong already derived sediment quality criteria for metals (SQC/metal) in 1990s.In China, no systematic and thorough researches have been carried out to develop sediment quality criteria for metals. The potential biological effects of freshwater and marine sediments are poorly understood to date. In this research, we used equilibrium partitioning approach to derive such criteria, which are compared with and revised by the site-specific metal/biological data. The main contents and results of our paper are as following:1. We clarified the concept of sediment quality criteria and sum up the international research developments in this area.2. Base on research work of foreign scholars, we provided a general model for developing SQC/metal. The model included many new parameters that can reflect both chemical composition and characteristics of sediment (e.g., pH, surface site density, surface acidity contents) from different regions and bioavailability of metals.3. We discussed how to ascertain some parameters in the model, such as Kp (partitioning coefficient for metals between sediment and water column), WQC (water quality criteria) and AVS (acid volatile sulfide). We also determined the AVS contents in some aquatic sediments in China and researched on the influences of AVS on bioavailability of metals in sediment.4. Using metal spiked sediment samples of the Yangtze River and the Yellow River, we determined toxicity of the samples to 3 kinds of representative aquatic organisms (including Vibrio qinghaiensis sp. Q-67, Chlorella valgaris and Daphnia magna) and worked out two criteria or assessment values of metals in sediments. The lower value, represented the concentration below which adverse effects were expected...