One-step separation of Cu, Fe, Zn and Cd and isotope ratio analysis by MC-ICP-MS for geological samples.

Multi-isotope systems have shown great application potential in tracing geological and environmental processes. In order to obtain the isotopic composition of multiple elements of interest, the common protocol is to separate each element from the matrix by independent procedures, which has some limitations, including poor efficiency, being time-consuming, requiring large samples and being unsuitable for rare samples (e.g., meteorite, lunar soil and atmospheric aerosol samples). In this study, we present an integrated and optimized one-step method to separate Cu, Fe, Zn and Cd from complex matrix elements using the AG MP-1M anion exchange resin. By experimentally optimizing the resin volume, eluent concentration and eluent amount, these target elements can be effectively separated from the matrix elements, such as Cu separation from Ti and Co, Zn separation from Fe and Cd, and Cd separation from Sn. The recoveries of Cu, Fe, Zn and Cd were 100.1 ± 0.8% (2SD, n = 3), 99.8 ± 0.7% (2SD, n = 3), 100 ± 0.8% (2SD, n = 3) and 99 ± 1% (2SD, n = 3), respectively. Moreover, the resolution (R) between the elements of interest and interfering elements was in the range of 1.8-28.1. The process blanks of Cu, Fe, Zn and Cd were 1-1.6 ng, 62-70 ng, 2.1-3 ng and 66-74 pg, respectively. The obtained isotope ratios for the standard reference materials agreed well with the published values. Meanwhile, we have reported the Cu, Fe and Zn isotope ratios of six soil and sediment standard reference materials, namely NIST 2711a, GSS-1, GSD-5a, GSD-7a, GSD-12 and GSD-23, for the first time. These new data can be used for the intercalibration and quality control of soils and sediments in other laboratories. The one-step separation of Cu, Fe, Zn and Cd shows obvious economic and efficiency advantages, making it suitable for the simultaneous separation of multiple elements of interest in geological samples.

[Spatial Interpolation Methods and Pollution Assessment of Heavy Metals of Soil in Typical Areas].

It is important to choose the best spatial interpolation method to reflect spatial distribution features and evaluate soil heavy metal pollution. The spatial distribution of arsenic (As) and cadmium (Cd) concentrations in top soil samples from Hubei Province were studied by four frequently-used spatial interpolation methods, including inverse distance weighted (IDW), radial basis function (RBF), local polynomial interpolation (LPI) and ordinary kriging (OK). The interpolation precision and effect of the spatial distribution of the four methods were compared with the results of cross validation and spatial distribution, and the pollution was assessed by the geoaccumulative index (Igeo) and indicator kriging (IK). The results showed that the four interpolation methods had small prediction errors, but that the interpolation effects were quite different. Among them, LPI had the most serious smoothing effect, followed by OK. The IDW and RBF best retained the extreme value information for element concentrations, and interpolation results were more detailed-and so to accurately understand the distribution of soil heavy metals, IDW or RBF methods were recommended. Taking the arithmetic mean of heavy metal concentrations in deep soil of Hubei Province as the background value, the evaluation result of geo-cumulative index pollution allowed exceedance percentages for As and Cd accounted for 5.5% and 99.0% respectively. The soils of the study areas were heavily contaminated with Cd. The pollution evaluation result from IK showed that high probability contaminated areas, with moderate-heavy contamination levels, were mainly located in the central part of the study area. The authors concluded that development of agriculture in the research area should include attention to Cd pollution and that soils there required the effective treatment and restoration of Cd levels.