Carbon and Nitrogen Stable Isotope Test Results of Carbonized Plant Remains from the Qingqiu Site

They were primarily unearthed from archaeological features dating to the Longshan period, Shang，Zhou, and Han dynasties at the site. A total of 91 samples were collected, including 63 millet samples and 28 wheat samples.The carbonized remains underwent a pretreatment process.

Plant remains were observed under a microscope, and impurities were manually removed. They were then ultrasonically cleaned with deionized water to remove stubborn adhering contaminants. The samples were dried at 50°C for 48 hours and subsequently ground to homogeneity using an agate mortar.Carbon and nitrogen stable isotope analysis was performed using an isotope ratio mass spectrometer.