Use of portable X-ray fluorescence spectroscopy and geostatistics for health risk assessment

Risk Identification of Heavy Metals in Agricultural Soils from a Typically High Cd Geological Background Area in Upper Reaches of the Yangtze River

This study adopted two risk assessment models to estimate the potential risk of heavy metals (HMs) in agricultural soils from a high Cd geological background area. Results were as follows: HMs posed an extremely high potential ecological risk (PER) (PER = 2051 > 1200) ascribed to Cd contribution. The overall non-carcinogenic risk (HI) of HMs for children (HI > 1) was unacceptable. Contributions of HMs to HI generally decreased in the order of Cr > As > Pb > Cd > Ni > Cu > Zn. The total carcinogenic risk (TCR) value for adults (2.1 × 10^-4) and children (2.2 × 10^-4) surpassed the reference value (1.0 × 10^-4), indicating that the risks were unacceptable. Contributions of HMs to TCR generally decreased in the order of Cr ≈ Ni > Cd > As > Pb. These results suggested that risk control policies should not only consider the potential ecological risk of Cd but also take into consideration of the carcinogenic and non-carcinogenic risk of Cr and Ni in a typically high Cd geological background area.

Identification of heavy metal pollutants and their sources in farmland: an integrated approach of risk assessment and X-ray fluorescence spectrometry

Investigation and assessment of farmland pollution require an efficient method to identify heavy metal (HM) pollutants and their sources. In this study, heavy metals (HMs) in farmland were determined efficiently using high-precision X-ray fluorescence (HDXRF) spectrometer. The potential ecological risk and health risk of HMs in farmland near eight villages of Wushan County in China were quantified using an integrated method of concentration-oriented risk assessment (CORA) and source-oriented risk assessment (SORA). The CORA results showed that Cd in farmland near the villages of Liuping (LP) and Jianping (JP) posed a "very high" potential ecological risk, which is mainly ascribed to soil Cd (single potential ecological risk index ([Formula: see text]) of Cd in villages LP and JP, [Formula: see text] = 2307 and 568 > 320). A "moderate" potential ecological risk was present in other six villages. The overall non-carcinogenic risk (hazard index (HI) = 1.2 > 1) of HMs for children in village LP was unacceptable. The contributions of HMs decrease in the order of Cr > As > Cd > Pb > Ni > Cu > Zn. The total carcinogenic risk (TCR = 2.1 × 10^-4 > 1.0 × 10^-4) of HMs in village LP was unacceptable, with HMs contributions decreasing in the order of Cr > Ni > Cd > As > Pb. Furthermore, three source profiles were assigned by the positive matrix factorization: F1: agricultural activity; F2: geological anomaly originating from HMs-rich rocks; F3: the natural geological background. According to the results of SORA, F2 was the highest contributor to PER in village LP, up to 64.4%. Meanwhile, the contributions of three factors to HI in village LP were 19.0% (F1), 53.6% (F2), and 27.4% (F3), respectively. It is worth noting that TCR (1.2 × 10^-4) from F2 surpassed the threshold of 1.0 × 10^-4, with an unacceptable carcinogenic risk level. As mentioned above, the HM pollutants (i.e., Cd and Cr) and their main sources (i.e., F2) in this area should be considered. These results show that an integrated approach combining risk assessments with the determination of HM concentration and identification of HM source is effective in identifying HM pollutants and sources and provides a good methodological reference for effective prevention and control of HM pollution in farmland.

Spatial distribution of heavy metals in soils of the flood plain of the Seversky Donets River (Russia) based on geostatistical methods

Soil contamination by heavy metals (HM) is a worldwide problem for human health. To reduce risk to human health from exposure to toxic chemicals associated with soil contamination, it is necessary to monitor and assess HM concentrations in the soil for places where the concentration exceeds the acceptable levels. Spatial patterning is a necessary tool for assessment of the exposure risk of HM contamination. Soil sampling (n = 65) was carried out in technogenically polluted soils located at Rostov oblast to study the content and spatial distribution of four HM (Cu, Zn, Pb, and Cr) in the surface layer (0-20 cm) of the impact zone of former Lake Atamanskoe (floodplain of the Seversky Donets River valley, Rostov region) with an area of 3.91 km². Extremely high values of HM concentrations were found with the maximum values of 702 mg/kg, 72,886 mg/kg, 2300 mg/kg, 259 mg/kg for Cu, Zn, Pb, and Cr, respectively. Inverse distance-weighted (IDW) interpolation was used to prepare 3D monoelement images of HM. Lognormal kriging and indicator kriging techniques were applied to create elemental spatial distribution maps and HM probability maps. The results showed that the total content of Cu, Zn, Pb, and Cr was moderately spatially dependent (nugget-to-sill ratio ranged from 31 to 38%), whereas the contamination index Zc formed strong spatial dependence patterns (nugget-to-sill ratio ranged from 0 to 21.4%). The obtained results of this study could serve as a guide to the authorities in identifying those areas which need remediation. Moreover, this study provides a tool for assessing the hygienic situation in the vicinity of Kamensk-Shakhtinsky (Rostov region) for decision making that can help to minimize the environmental risk of technogenic soil contamination of HM.

Spatial Distribution of As and Cd in Co-contaminated Soils Within the Rice Root Microzone

Soil samples were collected from the As and Cd co-contaminated demonstration area to analyze the spatial distributions of As and Cd in soils within the rice root microzone using the treatment of soil cubes (50 mm × 50 mm × 50 mm). The results indicated that there was no significant difference in the spatial distributions of total As or Cd in the microzone with the percentage of root weight, horizontal distances (HD), and vertical depths (VD). Interestingly, available As or Cd increased with the increasing HD, and both of them showed a significant difference (p < 0.05) between < 75 mm and ≥ 120 mm. The availability of As or Cd increased from the center to the edge of the rice root microzone. Moreover, the risk assessment code (RAC) showed that the site with a high potential risk of As or Cd was located on the edge of the rice root microzone. This phenomenon implied that cultivating paddy rice in the low potential risk microzone might have a low accumulative risk.

Spatial Variability of Soil Properties and Portable X-Ray Fluorescence-quantified Elements of typical Golf Courses Soils

Understanding and quantitative delineation of Portable X-Ray Fluorescence (PXRF) -quantified elements and soil properties spatial variability are important for healthy turf development for golf courses. In this study, PXRF-quantified elements and soil properties (except soil acidity and alkalinity (pH), electric conductivity (EC), and textures) of 200 soil samples were measured by PXRF analyzer at different golf courses in Lubbock, Amarillo, and Midland in Texas, and Hobbs in New Mexico. Furthermore, principal component analysis (PCA), empirical bayesian kriging (EBK) and the ordinary least square model (OLSM) were used in the study. Two kinds of components were extracted and interpreted by PCA, the results showed Zn, Ti, Fe, Rb, V, Mn and Zr were associated with the component 1, while Sr was associated with the component 2, the preliminary classification of PXRF-quantified elements was formed by PCA. The EBK approach was used to evaluate the spatial patterns of PXRF-quantified elements and soil properties. The OLSM model quantitatively related pH to EC, silt texture and the PXRF-quantified K, Ca and Sr. The integration of PCA, EBK and OLSM revealed quantitative links between soil pedogenesis and causes, spatial variability and couple relationships of PXRF-quantified elements and soil properties over golf courses.