天然水体中硫化物主要以H_2S及HS~-形式存在(在pH值低于12时,S~(2-)实际上可以忽略)。利用测得的总硫化物浓度,根据不同的pH值可求算出H_2S的浓度。H_2S是一种毒性大的物质,H_2S含量较高的水体,鱼类及水生动物则不复存在。地面水中及渔业用水体硫化物最高允许浓度为“不检出”。目前,硫化物的浓度大于4ppm时可以用容量法 The sulfide in natural water is mainly in the form of H 2 S and HS ~ - (S ~ (2-) can be neglected in practice when the pH is lower than 12). Using the measured total sulfide concentration, H 2 S concentrations can be calculated from different pH values. H 2 S is a toxic substance, and water bodies with high H 2 S content, fish and aquatic animals no longer exist. The maximum allowable concentration of sulfide in surface water and fishing water is “not detected”. At present, the capacity method can be used when the sulfide concentration is more than 4 ppm