BACKGROUNDFloodplain sediment, which is an important sampling media for geochemical mapping, can represent the average distribution of elements in the basins and has universal applicability. At present, there is no floodplain sediment reference material in the world. The development of similar standards in foreign countries focuses on the environment, and there are fewer fixed components. The same standards for soil and river sediments in China are limited by different work needs, and the development aims are different. Most of the standard substances are insufficient.

To develop 7 national first-level reference materials for floodplain sediments in the Yangtze River, Gan River, Han River, Huaihe River, Yellow River, Haihe River and Heilongjiang River (GBW07385-GBW07391). CANDIDATES CHARACTERISTICS:Sample GSS-29 is the floodplain sediment of the Yangtze River. It is grayish yellow and contains high contents of silty. GSS-30 is the floodplain sediment of the Gan River, which is sub clay with relatively fine particle size. GSS-31 is the floodplain sediment of the Han River, which is gray-black, fine-grained and contains relatively high contents of organic matter. GSS-32 is the floodplain sediment of the Huaihe River, which is grey-black, fine-grained and clay-like. GSS-33 is the floodplain sediment of the Yellow River, which is black clay with relatively fine grain size and relatively high contents of organic matter. GSS-34 is the floodplain sediment of the Haihe River, which is sub clay with a relatively fine grain size and high content of clay formed in block. GSS-35 is the floodplain sediment of the Heilongjiang River, which is black and loose, with a relatively fine grain size and high content of clay where some are formed in block.

METHODSA series of reference materials was tested using X-ray Fluorescence Spectrometry to measure 26 components. The RSD of the main components was less than 1%, the RSD of minor elements was 2% and the RSD of trace components was less than 7%. The F value of the variance test was less than the list threshold F_0.05(24,25)=1.96, indicating that all seven materials were homogeneous. No significant statistical changes were found in the 24 elements and compounds tested within 23 months, indicating that the stability of these materials were stable. Thirteen laboratories have participated in this inter-laboratory program, and have adopted various reliable analytical methods based on different principles to set the values.

RESULTSA total of 511 characteristic components, including 73 elements and compounds, have been tested. In addition to the CO₂ values of GBW07386 and GBW07388 that cannot be assigned, the remaining 494 characteristic components are given the certified value and uncertainty, and 15 characteristic components are given information value. The trace elements in GSS-29 have the mostly high background contents. The trace elements in GSS-30 have medium background values, and the contents of W, Sn and Mo are relatively high. The contents of Cd and Mo in GSS-31 are relatively high. The trace elements in GSS-32 have low background contents, and the contents of Cd, Hg, Mo, N, S and P are lower than the background level. The content of Hg in GSS-33 is very low. The trace elements in GSS-34 have the mostly medium and high background levels, and the contents of F, Cl and Br are relatively high. The organic matter content of GSS-35 is relatively high.

CONCLUSIONSThe seven reference materials for floodplain sediments have been certified by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ) in 2017. This series of floodplain sediment certified reference materials (GBW07385-GBW07391) represents the background values of the elements of each corresponding drainage area. It can be used for monitoring the quality of geochemical sample analysis or the quality of sample analysis in other fields, such as environment and agriculture.