Abstract: Currently, there are many methods for evaluating heavy metal pollution, and most of these methods are based on deterministic approaches rather than uncertainty evaluation methods. Recently, the Blind Number Theory is attracting more and more international attention for the evaluation of heavy metal pollution. This theory is based on an uncertainty point of view. Optimizing geo-accumulation model based on the Blind Number Theory is an uncertainty evaluation method, and it combines the principle of maximum degree of membership and the weighting degree of membership. Application of the Blind Number Theory in the area of pollution evaluation was different from the traditional deterministic pollution assessment method. The Blind Number Theory is suitable for the coexistence and uncertainty complex systems, especially suitable for evaluation of heavy metal contamination. Considering that the pollution assessment system involves many uncertain characteristics of information, the blind number optimization geo-accumulation model was applied to evaluate the heavy metal pollution of the sediments in the different types of lakes from the middle and lower reaches of Yangtze River based on the Blind Number Theory. Three typical heavy metals including Copper (Cu), lead (Pb) and zinc (Zn) were selected as the main indicators for heavy metals contamination evaluation. According to the equality of the spatial distribution from the computed possible value and reliability as well as the rating reliability level, the pollution degree and level were identified, and the influence of the local pollution on overall regional pollution was reduced. The results showed that the spatial distributions of heavy metals from the surface sediments of Xianghu Lake, Poyang Lake, Dongting Lake were not uniform. The heavy metal pollution of the surface sediments from Xiang Lake showed a trend of Pb > Cu > Zn. Pb was a moderate pollution, and Cu was slightly polluted, but Zn was clean. The heavy metal pollution in the sediments of Poyang Lake showed a trend of Cu > Pb > Zn. Cu was a moderate pollution, Pb was a partially moderate pollution, and Zn was a partially heavy pollution. The heavy metal pollution from the sediments of Dongting Lake was Cu ≈ Pb ≈ Zn, at a level of slight pollution. The blind number optimization geo-accumulation model was a feasible method, which was basically the same as the qualitative evaluation results, but more reliable to the determination of the pollution level. Moreover, the optimizing geo-accumulation model based on the Blind Number Theory could make the deficiencies of the traditional deterministic method and it could demonstrate the heavy metal accumulation pollution degree of the sediments in the evaluated regions more authentically and objectively. This method could provide new ideas for the methods of heavy metal pollution evaluation, and it can also provide a more reliable basis for environmental management and decision-making.

Key words: blind theory, index of geo-accumulation, sediment, heavy metal