Ô nhiễm nước là sự thay đổi theo chiều xấu đi các tính chất vật lý – hoá học – sinh học của nước, với sự xuất hiện các chất lạ ở thể lỏng, rắn làm cho nguồn nước trở nên độc hại với con người và sinh vật. Làm giảm độ đa dạng sinh vật trong nước. Xét về tốc độ lan truyền và quy mô ảnh hưởng thì ô nhiễm nước là vấn đề đáng lo ngại hơn ô nhiễm đất. | Laboratory Methods of Analysis 151 TABLE 10-2 Typical hatch QC samples. Batch QC Sample Description Purpose Measures Method or preparation blank Contains no sample material but is treated like a sample in every other way. Monitors any contamination to which the analytical batch may have been exposed during analysis. An acceptable result is below the level specified in the QAPP or the QAPjP. Contamination Laboratory control sample LCSJ A sample that contains the analyte s of interest in known amounts. Used to monitor the success of the analysis in recovering the analyte s of interest from a familiar sample matrix. _ Found value Recovery . X 100 Expected value Accuracy of the laboratory s performance of the method Method spike A method blank that has had a known amount of the analyte s of interest added to it. Used to monitor method accuracy when an LCS in not available. Accuracy of the laboratory s performance of the method Method duplicate MD A second portion of a field sample taken for analysis. When the result is compared to the original result from the filed sample a measure of precision can be developed rhe most common measure is relative percent difference RPD . IField sample result - MO resultl HPD Ji x 1 Average of field sample and MD results Precision Matrix spike MS A second portion of a field sample to which a known amount of the analyte s of interest has been added. Used to monitor the ability of the analytical method to recover the analyte s of interest from that particular field sample matrix. Accuracy of the laboratory s performance with that type of sample Matrix spike duplicate MSD A third portion of the same field sample to which the same amount of the analytes of interest has been added. When the result is compared to the result from the MS a measure of precision can be developed. MS MSD results usually are reported as relative percent of difference. See MD. Precision Surrogates Compounds similar to the analyte s of interest but that are known not
