Research On The Biological Toxicity Of Heavy Metals In The Standard Limits Of Drinking Water

The national hygiene standard use a single heavy metal threshold to limit the amount of heavy metals,but drinking water often exist a variety of different heavy metals at the same time.In order to understand the changes of biotoxicity and the influence on the safety of drinking water,we study the biological toxicity and influencing factors of heavy metal coexistence.In the study the acute toxicity algae infrared test used is a new toxicity test technique.The reproducibility and reproducibility of the test technique and evaluation method are related to the application and popularization.we selected five heavy metals including Cr???,Pb???,Hg???,Cd???,and Mn???to prepare sample solutions with a single heavy metal and various mixed heavy meta,Aiming at the shortcomings of the "one index method" in the original test evaluation method,the "three index method" was put forward,and the algae infrared test technology and evaluation method were improved by experiment of distilled water toxicity test and heavy metal toxicity test.The effects of single heavy metal solution and multi-element method were evaluated by using improved algae infrared test technique and three-index method.The toxicity of heavy metal coexisting solution,the safety of drinking water in the coexistence of heavy metals,and the relationship between the methods,species,quantity,total concentration and biooxicity of heavy metals coexisting.The main results are as follows:?1?Three-index method can control false results recurrence rate in 20%,In testing the toxicity of coexistence of four kinds of heavy metal(0.066⁰.156 mg·L^-1)in aqueous solution,average recurrence rates?%?/occurrence rate?%?of evaluation results by all the evaluation methods was 100/100 whereas the result of previous method by one algae's temperature was 67/100.During the toxicity testing of single heavy metal,the average recurrence rates?%?/occurrence rate?%?by the three-index method was 100/100 whereas the results of previous method were 0/0,0/13.4,and 81.2/100.The improved algae infrared test technology has high sensitivity and good stability.The three-index method can control the quality of the test results.The experimental method can guarantee the quality of the test data.?2?When the concentration of heavy metals coexist was more than 0.11 mg·L^-1,the percentages of cumulative response were 70% and 93%;The average response ratios of binary to quinary coexistence combination were 50%,80%,100% and 100%;the combinations which contained Cr???was 87.5%,those contained Pb???or Hg???was 58.3% and those contained Cd???or Mn???was 54.3%.The total concentration of heavy metals and the number of heavy metal elements were positively correlated to the toxicity of the algae.When the total concentration is 0.11 mg / L^-1 and heavy metals coexist element number larger than 3,the toxicity of heavy metals on algae increased significantly.Cr???could increase toxicity when heavy metal ions coexistence.?3?The occurrence rate of reproducibility and repeatability of no response result of five kinds heavy metal were 100%,in 26 kinds of coexistence combination,there were 19 kinds which had responses.The percentage of responding combination was 73.1%.Drinking water with five single heavy metal in index concentration is safe,but it has great risk with quaternion and quinary coexistence combination.When heavy metals coexist,it has a greater chance of producing biological toxicity and the percentage of responding combination was 73.1%.