Method for ecological risk assessment of heavy metal in river basin sediment based on toxicity effect

A method for ecological risk assessment of heavy metals in river basin sediment based on toxicity effect, the method comprises the following steps:

• (1) screening the main aquatic species of the assessed river basin environment according to the breadth and quantity of biodistribution;
• (2) sampling sediments within the assessed basin area, determining the types of heavy metals to be detected and numbering them:
• when there are n kinds of heavy metals to be detected, these heavy metals are numbered 1, 2, . . . , n−1, n, wherein 1≤n≤45;
• (3) measuring the concentration of the ith heavy metal of each sediment sample one by one, and calculating the average concentration c0−1i of the ith heavy metal, and calculating the pollution coefficient cfi of the ith heavy metal one by one according to the formula cfi=(c0−1i)/(cni), wherein, cni is the reference value of the ith heavy metal content in uncontaminated sediments;
• (4) collecting the release coefficient csi of the ith heavy metal;
• (5) collecting the chronic toxicity data of the ith heavy metal on aquatic species selected in step (1), performing curve fitting on the collected data, and selecting the curve regression equation with the highest goodness of fit, so as to obtain the best equation for the sensitivity of the ith heavy metal;
• (6) drawing a fitting curve (SSD) according to the best fitting equation obtained in step (5), and setting the y value of this equation, that is, the cumulative probability to 0.05, and then calculating the corresponding x value, which is the toxic concentration HCsi of the ith heavy metal that protects 95% of aquatic organisms;
• (7) repeating steps (4) to (6) n times to obtain the release coefficient csi and toxic concentration HCsi of each heavy metal determined in step (2), and integrating and normalizing the release coefficient csi and toxic concentration HCsi of each heavy metal to obtain the toxicity coefficient Si of the ith heavy metal;
• (8) calculating the toxicity response coefficient Tri of the ith heavy metal according to the formula Tri=Si*(5/BPI)X one by one, where BPI is the biological yield index of the water body evaluated and the value of x is 1, ½ or 0;
• (9) calculating the ecological risk index Eri of the ith heavy metal according to the formula Eri=Tri*cfi one by one, and the resulting Erl is used to evaluate the ecological risk of a single metal to the river basin:
• when Eri<30, the ecological hazard of the ith heavy metal to the assessed river basin is slight, when 30<Eri<60, the ecological hazard of the ith heavy metal to the assessed river basin is medium, when 60<Eri<120, the ecological hazard of the ith heavy metal to the assessed river basin is strong, when 120<Eri<240, the ecological hazard of the ith heavy metal to the assessed river basin is very strong, when Eri>240, the ecological hazard of the ith heavy metal to the assessed river basin is extremely strong.