Comprehensive assessment of regional selenium resources in soils based on the analytic hierarchy process: Assessment system construction and case demonstration

Topsoil selenium (Se) under Se-rich farming in China: Current status, cropping impacts and ecological risk assessment

Selenium (Se), as an essential microelement, can be supplied through Se-biofortified food from Se-rich soils and associated farming practices for human health, while it can also cause eco-risks if overapplied. In this study, a multi-scale spatiotemporal meta-analysis was conducted to guide sustainable Se-rich farming in China by combining a long-term survey with a reviewed database. The weighted mean concentration, spatial distribution of soil Se, nationwide topsoil Se variation from cropping impacts and its bioavailability-based ecological risks were assessed and quantified. The results showed that the weighted mean content (0.3 mg kg-1) of China was slightly higher than that of previous nationwide topsoil Se surveys, as more Se-rich areas were found in recent high-density sampling surveys. Cropping has overall reduced Se content by 9.5% from farmland across China and deprived more with the increase in farming rotation driven by geo-climatic conditions. Long-term cropping removed Se from Se-rich areas but accumulated it in Se-deficient areas. Additionally, the bioavailable Se content of topsoil in China ranged from 0 to 332 μg kg-1, and the bioavailability-based eco-risks indicated that high eco-risks only existed in overfertilized and extremely high-Se soils, such as in Enshi, Ziyang and some coalfield areas. This work provides evidence for the development of sustainable Se-rich farming with proper utilization of soil Se resources, simultaneously protecting the soil eco-environment.

Geochemical relationship and profile distribution of Selenium and Cadmium in typical Selenium-enriched areas in Enshi

Selenium (Se) is an essential nutrient element for humans, and Se-enriched products are gaining popularity due to their health benefits. However, Enshi, a region in China naturally rich in Se, a high background value of cadmium (Cd) is discovered, which severely impacts local Se-enriched agriculture. Therefore, it is crucial to explore the geochemical relationship between Se and Cd. In this study, we analyzed soil profiles and parent rocks of different geological ages from Enshi to investigate the accumulation and distribution of Se and Cd. The ratio of redox sensitive elements and the multivariate statistical analysis, along with XRD and XPS analysis, were utilized to investigate the correlated relationship between Se and Cd and the underlying geochemical mechanisms. The results showed that average Se and Cd contents in rocks were 1.67 and 0.32 mg/kg. Se and Cd levels reached highest at Permian in rocks of different geological ages, which may be related to the Permian Dongwu movement near the study area. The highest migration rate of Cd and Se from rock to soil was 12 and 1.5 times. The soil Se and Cd fractions were mostly in bound states, with the largest fraction of Se being organic-bound at an average of 45.9%. The reducible and the residue state accounted for the largest proportion in the Cd fractions, with an average of 40.6% and 25.6%. Redox-sensitive element ratios indicate a reducing forming environment of deep sediments in the Permian strata. Furthermore, the correlation and PCA analysis revealed highly significant positive correlations between Se, Cd, V and Cr, suggesting that the sources of Se and Cd were closely related to volcanic and biological activities. In conclusion, a strong geochemical relationship was observed between Se and Cd. And as a result, metal pollution must be closely monitored during the production of Se-enriched agriculture in Se-enriched regions.

Quantitative prediction of potential areas likely to yield Se-rich and Cd-low rice using fuzzy weights-of-evidence method

The research of high-quality agricultural products rich in selenium and low in cadmium (Se-rich and Cd-low, respectively) is related directly to the value of agricultural products and people's food safety. Now it is still challenging to carry out development planning for Se-rich rice. By fuzzy weights-of-evidence method, the geochemical soil survey data of Se and Cd from 27,833 surface soil samples and 804 rice samples was used to predict the probability of areas, in Hubei Province, China, that will likely yield (a) Se-rich and Cd-low rice, (b) Se-rich and Cd-normal rice and (c) Se-rich and Cd-high rice. The areas predicted to likely yield Se-rich and Cd-high rice, Se-rich and Cd-normal rice, and high quality (i.e., Se-rich and Cd-low) rice cover 6542.3 km2 (5.9 %), 35,845.9 km2 (32.6 %), 12,379.7 km2 (11.3 %), respectively, of the surveyed region. According to the predictive distribution probability mapping of Se and Cd, this paper gives preliminary suggestions on the use of endogenous and exogenous Se, and Cd-reduction measures in planting Se-rich rice in different regions of Hubei Province. This study provides a new perspective for rational rice planting of Se-rich agricultural products, and it lays a foundation for the effective implementation of a geochemical soil investigation engineering project, which is of great significance for improving the economic value of Se-rich agricultural products and sustainable utilization of Se land resources.

River Ecosystem Health Assessment Using a Combination Weighting Method: A Case Study of Beijing Section of Yongding River in China

(1) Background: River health assessment provides the foundation for sustainable river development and management. However, existing assessments have no uniform standards and methods. (2) Methods: The combination weighting method was proposed, drawing on the advantages of subjective and objective weighting methods. To comprehensively investigate the river health level, an index system based on 16 indices selected from river morphology, river water environment, riparian condition, and social services level was established. The method and framework were applied to the Beijing section of Yongding River in China. (3) Results: The comprehensive weights of river morphology, river water environment, riparian condition, and social services are 0.1614, 0.3170, 0.4459, and 0.0757, respectively. The river health comprehensive index of Yongding River is 3.805; the percentages of excellent, healthy, sub-healthy, unhealthy, and sick river segments are 0%, 11%, 69%, 20%, and 0%, respectively. (4) Conclusions: The results indicate that Yongding River is in a sub-healthy state, and the riparian condition is the key factor that affects the river ecosystem health. Health level exhibited a remarkable spatial variation, mainly influenced by anthropogenic activities, and effective measures are needed to minimize the impact in fragile ecological areas.

A multi-criteria GIS-based model for wind farm site selection with the least impact on environmental pollution using the OWA-ANP method

Wind energy is considered one of the most efficient and cost-effective ways to generate electricity, since it has a low environmental impact. So, it is essential to identify the best places to build wind farms that have the lowest impact on human health and the highest performance. In order to determine the appropriate locations for the construction of wind power plants, in the study first, the interpolation maps of the most important parameters for the construction of wind power plants were created. Then, using the analytic network process (ANP) method due to higher accuracy than other weighting methods (the two-by-two comparison of external and internal data), the weight of each criterion was determined by establishing the external and internal relationships between the criteria and sub-criteria. In this study, since the objective was to prepare land suitability maps with different levels of risk in order to further manage the area, the OWA method was used to prepare land suitability maps. Based on the results of the ANP method for weighing each parameter, wind speed and protected areas were the most and least important parameters to build the power plant. According to the results of the OWA method, 0.78 and 0.1% of the area were suitable for building power plants at high and low risk levels, respectively. The study also found that the number of wind turbines that can be built in the region at both high and low risk levels was 422 and 75, respectively. Using the buffer function, the number of turbines for the construction of high-risk power plants was reduced to 284 by using the appropriate distance from residential areas. The ANP and OWA methods were used to prepare several maps for the evaluation of land suitability with different levels of risk, one of which could be used for the construction of a power plant.

The interaction between selenium and cadmium in the soil-rice-human continuum in an area with high geological background of selenium and cadmium

Natural selenium (Se)-rich areas in China are generally characterized by high geological background of cadmium (Cd). However, the interaction between Se and Cd in the soil-rice-human continuum in such areas remains elusive. The concentrations, bioaccessibilities, and biomarkers of Se and Cd in a typical Se-Cd rich area were determined through chemical analysis, in vitro digestion model and cross-sectional study, respectively. The results showed that the molar ratio of available Se/Cd in the soil was averaged at 0.55 and soil Se did not reduce Cd accumulation and transportation in rice. Se bioaccessibility increased from the gastric phase to the intestinal phase, but the opposite was the case for Cd bioaccessibility. Moreover, bioaccessible concentration of Cd was positively correlated to corresponding total concentration in rice but negatively associated with the logarithm of molar ratio of Se/Cd. The risk of Cd-induced nephrotoxicity for the exposure group was not higher than the reference group, which could be ascribed to the mitigative effect of Se. Males and elders were at higher risk of Cd-induced injury owing to higher urinary Cd (U-Cd) and β2-microglobulin (U-β2-MG), and lower urinary Se (U-Se). Our results suggested that Cd-induced health risk should be assessed from a soil-rice-human perspective and the interaction between Se and Cd should be taken into account.

The Spatial Distribution Characteristics of the Cultivated Land Quality in the Diluvial Fan Terrain of the Arid Region: A Case Study of Jimsar County, Xinjiang, China

Environmental constraints are not only important aspects that affect the cultivated land quality but also necessary factors that shall be considered when evaluating the cultivated land quality scientifically. Moreover, identifying the quality condition of cultivated land accurately is the premise for guaranteeing food security. Based on the case study of diluvial fan terrain in Jimsar County, Xinjiang in the arid region of Northwest China, this study utilizes a geographic information system spatial analysis and a multifactor comprehensive evaluation method and constructs a comprehensive evaluation index system for cultivated land quality on account of three dimensions, namely soil properties, farming conditions, and natural environmental conditions. To reduce the Modifiable Areal Unit Problem (MAUP) effect and improve the accuracy of the quality evaluation results of cultivated land, this study compares the spatial interpolation methods of Inverse Distance Weighted Matrix (IDW), Ordinary Kriging (OK), and Spline Functions (Spline) based on different cultivated land evaluation units. Through the assessment on the comparison results, we finally adopted large-scale cultivated land as the quality evaluation unit of cultivated land and Ordinary Kriging (OK) as the spatial interpolation method. The results indicated that the average grade of the quality index of cultivated land in the diluvial fan terrain of Jimsar County is 6.66 at the middle or lower level; the quality of cultivated land and natural environment conditions reduce with the rise of elevation of the diluvial fan terrain, indicating a vertical zonality differentiation rule; the farming conditions keep sliding from the middle part of diluvial fan terrain to the edge of the diluvial fan terrain and the piedmont slope. The major factors affecting the quality of the cultivated land include the soil capacity, soil pH, soil organic matter, the quantity of straw returning to the field, source of irrigation water, water delivery method, part of the diluvial fan, groundwater level depth, and geomorphic type. Therefore, the measures to improve the quality of the cultivated land are put forward, mainly including improving the soil, carrying out land consolidation projects, and developing highly efficient water-saving irrigation agriculture. This study provides favorable references and directions for the sustainable utilization and quality improvement of cultivated land resources in arid regions.

A Comprehensive Forecasting–Optimization Analysis Framework for Environmental-Oriented Power System Management—A Case Study of Harbin City, China

In this study, a comprehensive research framework coupled with electric power demand forecasting, a regional electric system planning model, and post-optimization analysis is proposed for electric power system management. For dealing with multiple forms of uncertainties and dynamics concerning energy utilization, capacity expansions, and environmental protection, the inexact two-stage stochastic robust programming optimization model was developed. The novel programming method, which integrates interval parameter programming (IPP), stochastic robust optimization (SRO), and two-stage stochastic programming (TSP), was applied to electric power system planning and management in Harbin, China. Furthermore, the Gray-Markov approach was employed for effective electricity consumption prediction, and the forecasted results can be described as interval values with corresponding occurrence probability, aiming to produce viable input parameters of the optimization model. Ten scenarios were analyzed with different emissions reduction levels and electricity power structure adjustment modes, and the technique for order of preference by similarity to ideal solution (TOPSIS) was selected to identify the most influential factors of planning decisions by selecting the optimal scheme. The results indicate that a diversified power structure that dominates by thermal power and is mainly supplemented by biomass power should be formed to ensure regional sustainable development and electricity power supply security in Harbin. In addition, power structure adjustment is more effective than the pollutants emission control for electricity power system management. The results are insightful for supporting supply-side energy reform, generating an electricity generation scheme, adjusting energy structures, and formulating energy consumption of local policies.

GIS Multi-Criteria Analysis by Ordered Weighted Averaging (OWA): Toward an Integrated Citrus Management Strategy

This study proposes a site location assessment model for citrus cropland using multi-criteria evaluation (MCE) and the combination of a set of factors for suitability mapping and delineating the suitable areas for citrus production in Ramsar, Iran. It defines an incorporated method for the suitability mapping of the most appropriate sites for citrus cultivars with an emphasis on the multi-criteria decision analysis (MCDA) process. The combination of geographic information system (GIS) and a modified version of the analytic hierarchy process (AHP) based on the ordered weighted averaging (OWA) technique is also emphasized. The OWA is based on two principles, namely: the weights of relative criterion significance and the order weights. Therefore, the participatory technique was employed to outline the set of standards and the important criterion. The results derived from the GIS–OWA technique indicate that the cultivation of citrus is feasible only in limited areas, which make up 6.7% of the total area near the Caspian Sea. This investigation has shown that the GIS–OWA model can be integrated into MCDA to select the optimal site for citrus production. The present research highlights how multi-criteria in GIS can play a considerable role in decision making for evaluating the suitability of selected sites for citrus production.