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BACKGROUND: The quality of soil is directly related to human health and the safety of agricultural products, which has important references for agricultural planting and land planning. As an important vegetable basket base in Chengdu, Tangchang Town has developed agricultural planting, but the recent soil quality in the region is still unclear. OBJECTIVES: In order to accurately understand the current content of nutrient and heavy metal elemental characteristics and soil quality grade of topsoil in the Tangchang agricultural planting area. METHODS: According to 1 ∶ 50000 soil quality geochemical survey, 810 topsoil samples were collected. The contents of N, P, K, As, Cd, Hg, Pb, Cr, Ni, Cu, Zn, Se and pH in these soil samples were determined by X-ray fluorescence spectrometry, inductively coupled plasma - mass spectrometry, atomic fluorescence spectrometry, element analyzer and ion selective electrode method. The element geochemical characteristics and soil nutrient grade, soil environmental quality grade and comprehensive soil geochemical grade were then evaluated. RESULTS: (1) Compared with the general topsoil in China, Zn and Pb in the topsoil of the study area are slightly enriched, Se is relatively enriched, N, P, Cd and Hg are strongly enriched. The topsoil is generally weakly acidic. (2) The comprehensive grade of soil nutrients is rich in second grade, accounting for 88. 0% of the area, and the soil fertility is rich. The proportion of the first grade soil area in the environmental quality grade of the eight heavy metal elements in the soil is more than 96. 0%, and the comprehensive environmental quality grade is dominated by first grade clean type, accounting for 98. 06%. The comprehensive quality of soil is mainly grade one, accounting for 85. 85%. (3) The area of selenium-rich soil in the region is 2. 49km², accounting for 3. 7%, sporadically distributed in the central study area. Copper-rich soil area is 63. 13km2, accounting for 94. 0%, and zinc-rich soil area is 63. 31km2, accounting for 94. 17%. CONCLUSIONS: In summary, the nutrients of topsoil in Tangchang Town are rich, the soil environment is clean and the comprehensive quality of the soil is high. [ABSTRACT FROM AUTHOR]

BACKGROUND: The determination of iodine in geochemical samples by inductively coupled plasma-mass spectrometry (ICP-MS) is treated mainly by closed sample melting, mixed acid solution, alkali fusion and semi-melting method. However, due to the complex existent morphology of iodine in soil and sediment samples, including periodate, iodate and iodide ions, and the first ionization energy of iodine being high as a halogen group element, there are problems such as incomplete dissolution, strong memory effect and poor precision during sample processing and measurement. OBJECTIVES: To improve the determination of iodine in geochemical samples by ICP-MS.METHODS: The samples were treated by sodium carbonate-zinc oxide semi-melting method, extracted with boiling water-ethanol, and separated by 732 cation exchange resin. Following this, iodine in the solution was determined by ICP-MS using an internal standard method. RESULTS: The optimized detection limit of iodine was 0.045μg/g, the lower limit of detection was 0.15μg/g. The precision (RSD, n=12) and the accuracy (△logC) of the method were ≤5.93% and ≤0.01, respectively, which satisfied the analysis standards of geochemical survey sample. CONCLUSIONS: This method meets the requirements of sample analysis for geochemical investigation, and can be used for the analysis of iodine in large quantities of soil and sediment samples. [ABSTRACT FROM AUTHOR]

BACKGROUND: Multi-target geochemical mapping is one of the most important basic regional tasks in multi-target regional geochemical surveys. In order to better reflect changes in the geochemical background, analytical methods are required to have higher accuracy and precision, and lower detection limits. Elements B, Ge, Br, Mo, Sn, I, and W in geochemical survey samples are mainly prepared and determined by smelting ore individually or in groups. The analysis procedure is long and involves 6 methods. OBJECTIVES: In order to integrate 6 supporting analysis methods, optimize analysis conditions, and improve the accuracy and precision of the method. METHODS: The mixed reagent of sodium peroxide and sodium hydroxide was used for alkali fusion. Citric acid was added to the solution. Cation exchange resin was used for static exchange for 2-3 hours to remove a large amount of cations in the solution and reduce matrix interference. B, Ge, Br, Mo, Sn, I, and W were determined using inductively coupled plasma mass spectrometry. RESULTS: The detection limits of B, Ge, Br, Mo, Sn, I, and W were 0.66, 0.096, 0.78, 0.11, 0.15, 0.29, and 0.27μg/g, respectively. Relative standard deviation (RSD, n=12) was between 2.1% and 7.5%, which were all less than 10%. CONCLUSIONS: The method is simple, rapid and low-cost, and its precision and accuracy meet the requirements of 《Specification of multi-purpose regional geochemical survey (1∶250000) 》(DZ/T 0258—2014). It can quickly and accurately determine B, Ge, Br, Mo, Sn, I, W in geochemical survey samples in a thick coverage area. [ABSTRACT FROM AUTHOR]

BACKGROUND: From 1986 to 2007, different grades of trace gold certified reference materials (background grade, anomaly grade, medium grade and high grade) and mineral gold certified reference materials (mineralization grade, cutoff grade and concentrate grade) had been developed by IGGE and used for regional geochemical survey, mineral exploration and evaluation, mining and smelting. With the increase of the service life period and the consumption of recent years, most of the gold certified reference materials has been used up or almost used up. New gold standard materials need to be developed urgently. OBJECTIVES: To develop a new gold certified reference material and compare it with the original gold certified reference material. METHODS: The trace gold certified reference materials in 7 levels and mineral gold certified reference materials in 3 levels were prepared in strict accordance with relevant specifications. The collected candidates were sampled from different types of deposits and different matrices. The collected candidates were prepared through coarse crushing, drying, composite configuration, fine crushing, sieving, blending and other steps. After the particle size inspection, the cumulative content of the sample with a particle size of 0.74μm reached more than 99%, which met the requirements of the specifications. 25 bottle samples of each grade were randomly selected. Homogeneity testing was carried out by ICP-MS, FAAS and GFAAS.RESULTS: The relative standard deviation (RSD) was less than 10%, and the F values of the variance test were less than the one-tailed critical value F0.05（24,25） of 1.98, indicating that the sample uniformity was good. During the one-year investigation period, no significant changes in statistical significance were found in the fixed value components, which proved that the stability of the sample was good. Five highly experienced and skilled laboratories in geology gold samples testing in CHN were invited to evaluate the gold certified reference materials by classically reliable analytical methods. The original data conformed to the normal distribution after statistical inspection and the suspicious values were eliminated. The arithmetic mean was used as the standard value, and the uncertainty was evaluated in detail, in accordance with the latest specifications. The certified value of the copied standard material was accurate and reliable, and the uncertainty was reasonable. It was approved as a national first-level standard material in 2019. Compared with the original batch, the certified values of the two batches were basically the same, and the standard deviation of the fixed value data showed a shrinking trend, which met the requirements for copying standard materials. CONCLUSIONS: This series of gold standard materials has a wide content range, and meets the value comparison and analysis monitoring of different content levels. Moreover, it has good applicability, and meets the needs of geological and mineral research, regional geochemical investigation, gold mine exploration and evaluation. [ABSTRACT FROM AUTHOR]

BACKGROUND: As one of the main foods in my country, the food safety of rice has been paid more and more attention to. It is of great practical significance to carry out accurate analysis and testing of the chemical components in rice. Comprehensive investigations of natural resources, agricultural products and food safety evaluation all require accurate testing of the elemental composition of biological samples. Therefore, the market demand for biological matrix reference materials has increased significantly, and the demand for rice reference materials is particularly prominent. At present, the demand for rice composition analysis reference materials has exceeded demand. OBJECTIVES: To develop the nee certified reference materials ( GBWl 001 0a) and compare with the data characteristics of GBW10010. METHODS: In strict accordance with the ' General Principles and Statistical Principles for the Valuation of Reference Materials' ( JJF 1343-2012) and 'Development of Reference Materials for Geological Analysis' ( JJF 1646-2017) and other relevant specifications, the GBW10010a rice composition analysis reference material was developed. Re - research (research) system work includes key links such as sample collection, processing and preparation, uniformity inspection, stability inspection, multi - laboratory collaborative value testing and uncertainty evaluation. RESULTS: GBWl 001 0a has a total of 54 main trace elements, including Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Gd, Ge, Hg, Ho, K, La, Li, Ho, Mg, Mn, Mo, N, Na, Nb, Nd, Ni, P, Pb, Pr, Rb, S, Sb, Sc, Se, Si, Sm, Sr, Tb, Th, Tl, Tm, U, V, Y, Yb, Zn; of which 39 elements give certified value and uncertainties, including Ag, Al, As, B, Ba, Ca, Cd, Ce, Co, Cs, Cu, Dy, Er, Fe, Hg, K, Li, Mg, Mn, Mo, N, Na, Nd, Ni, P, Pb, Pr, Rb, S, Sb, Se, Si, Sm, Sr, Tb, Tl, Y, Yb, Zn. 15 elements provide reference values, including Be, Bi, Cr, Eu, Gd, Ge, Ho, Ho, La, Nb, Sc, Th, Tm, U, V. CONCLUSIONS: The rice reference materials prepared in this re - research ( research ) have vanous components, accurate and reliable measurement values, and meet the requirements of national first - level reference materials. Compared with the original GBW10010, the total number of certified value elements has increased by 7 items, and the new certified value elements Ag and Nb ( Nb gives reference values), and the uncertainty range of each element is somewhat different. The reduction indicates the technological advancement of the geological analysis test method and the improvement of the certified value level. In addition, the content of heavy metal elements in GBW10010a decreased significantly, reflecting the improvement of farmland ecological environment to a certain extent. The designated elements of this reference material cover most of the main and trace elements with biological effects, and are suitable for the calibration of analytical instruments and analytical methods in the agricultural ecological environment geochemical survey and evaluation, biological sample testing, agricultural product quality and food safety evaluation sample testing Evaluation and analysis of quality monitoring and other fields. [ABSTRACT FROM AUTHOR]

BACKGROUND: The abundances and variation characteristics of silver, boron and tin reflect the regional metallogenic conditions and indicate the existence of deposits or mineralization. Silver, boron and tin in carbonate minerals are elements that must be determined in exploration geochemistry and multi - objective geochemistry. The analytical method was one of the essential methods in the matching analysis scheme of geochemical elements. Because carbonate minerals are different from common rocks, soils and water - based sediments, these minerals are mainly limestone, dolomite and other rock samples with relatively high calcium and magnesium elements, and the technical difficulty in determining silver, boron and tin in these samples is that the high content of calcium and magnesium matrix will seriously disturb the elements with low contents to be measured, and the sample is easily contaminated due to carbon dioxide during the spectrum recording process. OBJECTIVES: To solve the problems of rapid and accurate determination of silver, boron and tin in carbonate minerals. METHODS: In view of the particularity of carbonate minerals, an analytical method for the simultaneous determination of silver, boron and tin in carbonate minerals by alternating current - arc optoelectronic direct reading - optical spectrometry (AC - ARC - OES) was established. RESULTS: By using I 0% hydrochloric acid to digest the sample, the interference of matrix elements, calcium and magnesium, was eliminated. Germanium was used as the internal standard element for quantitative analysis, which eliminated the influence of external factors, such as the change of arc excitation conditions and matrix composition of the sample. The silver element and the long wave germanium element were used to form the analysis line pair, and the boron and tin element and the short wave germanium element were used to form the analysis line pair with good sensitivity. Twelve national geochemical reference materials, such as natural carbonate rock and synthetic limestone, were selected as the standard series. The matrix components were similar to those of the samples. The method of off - line subtraction was used to correct the background. The detection limits of the method for silver, boron and tin were 0. 008 µg/ g, 0. 4 9 µg/ g and 0. 18 µg/ g, respectively. The precision of the method was larger than 10% for silver, and that of other elements was better than 10%. The accuracy of the method was verified by the national level geochemical reference materials, and the logarithm difference between the average value and the certified value of the reference materials was less than or equal to ± 0. 05. CONCLUSIONS: This method was used to solve the problem of rapid determination of silver, boron and tin in carbonate minerals. It is simple and fast, and suitable for the determination of a large numbers of samples. All of the technical indices of the method meet the requirements of multi - objective regional geochemical survey specifications. [ABSTRACT FROM AUTHOR]

BACKGROUND: Selenium is an important, essential element of life. The development of selenium-enriched agricultural products is a safe and effective way to increase the level of human selenium intake in China. The evaluation and utilization planning of selenium-enriched land resources are important aspects of land quality geochemical surveys, to serve the development of characteristic agricultural products and to overcome poverty. OBJECTIVES: To improve the methodology for selenium-enriched land assessment and to develop more effective and safe land-use planning methods.METHODS: The research results on selenium content in soil and crops, the origin of soil selenium, the soil selenium occurrence and its bioavailability factors, the soil-crop system selenium absorption and transport, and the interaction between selenium and heavy metal cadmium were reviewed in this article.RESULTS: The geochemical background of selenium in top soils in China was 0.2 mg/kg, significantly lower than the average in world soils(0.4 mg/kg). Generally, the soils had a low selenium level, and it was believed that the use of 0.40 mg/kg selenium as a selenium-enriched soil standard had a strong scientific basis. Selenium in soils was mostly from a geological setting, however, in some cases anthropogenic activities may be an important source of soil selenium. The genetic mechanism of selenium-enriched soils can be categorized as high geological background, weathering accumulation and anthropogenic input as well as a multi-factor combination. The association of selenium with cadmium and other heavy metals was pervasive because of similar geochemical behavior and geological origin. The species and bio-availability of selenium in soils were mainly controlled by its source and soil physic-chemical properties such as pH, Eh, and contents of organic matter, iron oxides and aluminum oxides. In turn, these factors affect the availability of selenium-enriched land and became the theoretical basis and considerations for formulating local standards for selenium-enriched soil. The accumulation ability of selenium varied greatly between crop cultivars. Selection native crop types with higher selenium accumulation ability and low accumulation with Cd as well as other toxic metals was of practical meaning. Some existing selenium-enriched agricultural product standards did not fully consider the purpose of human selenium supplementation, and there were problems such as poor coordination between standards. It was urgent to strengthen the formulation of selenium-enriched agricultural product standards.CONCLUSIONS: Selenium-enriched land suitability assessment, local selenium-enriched soil standard establishment and selenium-enriched crop plantation planning should consider the concentration of selenium and heavy metals in soils, their source and genesis, bio-availability and influencing factors, transport and accumulation in soil-crop system, the synergistic or antagonistic effects between selenium and other chemicals such as cadmium, as well as plantation suitability of crop cultivars under local climate, soil conditions and landscape. According to the availability of selenium-enriched land resources, classification, zoning, scientific planning and reasonable planting management are carried out. In order to meet the needs of investigation and evaluation of selenium-enriched land resources, availability analysis, and research on the health effects of selenium-enriched agricultural products, it is recommended to strengthen the research and application of extraction, separation, analysis, and determination methods for soil and crop selenium content and species. [ABSTRACT FROM AUTHOR]

BACKGROUND: Traditional Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) determination of trace elements such as silver and cadmium in geochemical samples is seriously affected by the matrix effect and multiple polyatomic ions, making it difficult to measure these elements accurately. OBJECTIVES:To compare the results of ICP-MS standard mode (STD) and kinetic energy discrimination mode (KED), and determine the valid determination modes of each element. METHODS: The samples were digested by HNO3-HF-HClO4, and the residue was dissolved in aqua regia. Under the KED mode, the isotopes with less interference were selected as the determination isotopes. Rh was used as the internal standard element to correct the signal drift, and the sample solution was diluted by 1000. Under these conditions, the matrix effect was minimized. RESULTS: The productivity of matrix elements such as Zr and Nb oxides was reduced, and the interference of oxides on Ag and Cd was minimized under the KED mode. The KED mode improved the signal-to-noise ratio and reduced the detection limits of this method with Ag and Cd, detection limits of 0.004mg/kg and 0.005mg/kg, respectively. The detection limits of the other 12 elements were also lower than those of 76 element analysis schemes in a multi-objective geochemical survey. The accuracy of determination of trace elements was significantly better than that of the STD mode. CONCLUSIONS: The method has been verified by the first-class national reference material and the analytical results are in good agreement with the certified values. The method provides high-quality data for exploration geochemistry. [ABSTRACT FROM AUTHOR]

BACKGROUND: ith the rapid development of China's coastal economy, the intensity of human activity is increasing. The disturbance and damage to the marine ecosystem are becoming increasingly serious. In order to understand the water quality of the coastal waters of Haizhou Bay, the survey of surface seawater quality in Haizhou Bay was carried out in April and September, 2016. Hydrochemistry factors including temperature, salinity, pH, SS, DO, CODMn, NO2--N, NO3--N, NH4+-N, PO43--P, Cu, Pb, Zn, Cd and oils were surveyed. OBJECTIVES: To explore the spatial and temporal distribution characteristics and pollution level in the coastal waters of Haizhou Bay. METHODS: The indexes were analyzed by Spectrophotometry and Inductively Coupled Plasma-Mass Spectrometry. Based on the single factor method, evaluation mode of eutrophication and organic pollution index, the water quality has been evaluated. RESULTS:The average value of CODMn in the surface seawater of the study sea area was 1.34mg/L in April and 1.22mg/L in September. The average value of petroleum in April was 0.031mg/L, and that in September was 0.034mg/L. The average value of active phosphate was 0.013mg/L in April and 0.012mg/L in September. The average value of dissolved inorganic nitrogen in April was 0.34mg/L and in September was 0.16mg/L. The concentrations of CODMn, petroleum, active phosphate and dissolved inorganic nitrogen showed the decreasing trend from the southwest to the northeast. Moreover, the overall concentration of inorganic nitrogen was higher, which was the main pollutant in the sea area. CONCLUSIONS: According to the eutrophication evaluation model and the results of organic pollution index calculation, this study demonstrates that the overall nutrient level of surface water quality in the coastal waters of Haizhou Bay is relatively high, and it reaches the potential eutrophication level of nitrogen limitation. The degree of organic pollution belongs to GradeII, indicating the level of pollution in the water. [ABSTRACT FROM AUTHOR]