Sampling methods and errors appearing in the China National Human Biomonitoring Program / 中华流行病学杂志

Objective: To explore the sampling method in China National Human Biomonitoring Program (HBP) and the related errors, so as to calculate and evaluate the study design in sampling. Methods: The sampling method of HBP is of multistage nature. Taking the results of sampling method from Guizhou province as an example, results related to sampling error and variation coefficient were calculated, using the multistage unequal probability sampling error method. Results: The HBP covered 152 monitoring sites in 31 provinces (autonomous regions and municipalities) and with 21 888 residents selected. The replacement rates at various stages were 5.26%, 6.35% and 40.6% respectively. The sampling error in Guizhou province was 3 207 594, and the coefficient of variation was 0.097. Conclusions: According to the multi-stage unequal probability sampling method, the sampling coefficient variability appeared small with high precision, in Guizhou province. However, this method did not consider the weight adjustment of non-sampling errors such as population missing rate and response rate. Methods related to the calculation on multi-stage sampling error among large-scale public health monitoring projects need to be further studied.

Copper and nickel recovery from electroplating sludge by the process of acid-leaching and electro-depositing

In this work, we developed a method which combined the processes of acid-leaching, ammonium jarosite precipitating and electro-depositing to recover copper and nickel from electroplating sludge. Residual sludge from an electroplating plant located in Qingdao was used for acid-leaching, and more than 95% of copper, nickel, zinc, chromium and iron were extracted from the sludge. After acid-leaching, the extracted solution was put into an electrolytic cell for copper recovery by electro-depositing process, and about 95% of copper was recovered under the optimized operation parameters such as cell voltage, pH and electrode material. After copper recovery, the extracted solution was treated with ammonium jarosite precipitating process. About 99% of chromium and iron could be deposited as chromium ferrite in this process. Finally, the left solution was treated with electro-depositing process again for nickel recovery, and about 57% of nickel could be recovered in this process under the condition of pH 5.5 and voltage 5.5 V