Soil Se Research Articles

Geochemical Characteristics and Source Apportionment of Soil Elements in an Urban-rural Integration Area: A Case Study in the Qinglong Area of Tianfu New District

The Qinglong Area of Tianfu New District in China is the connection area of Chengdu city, Sichuan Province, which dominantly supports the primary agricultural products for the metropolis. The soil quality, therefore, has been deteriorating in recent decades due to the intensive planting and industrial pollution. Thus, the evaluation of soil quality and the identification of the pollution sources are significant for sustainable soil planting and regulation. To this end, 395 soil samples were collected, and the parameters of pH, soil organic matter (SOM), total potassium (TK), available potassium (AK), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), total phosphorus (TP), available phosphorus (AP), Se, B, V, Zn, Mn, Mo, Ni, Co, As, Cd, Cr, Cu, Hg, and Pb were analyzed. The results revealed that TN, Se, Hg, and TP were obviously higher than the background value of the Chengdu Economic Zone, and the Cr, Mn, pH, and TK were depleted. The combination of correlation statistics, geostatistics, and positive matrix factorization (PMF) source analysis revealed that heavy metal enrichments were mainly affected by four sources, namely natural sources (32%)>industrial sources (30%)>agricultural sources (25%)>traffic sources (14%). Likewise, the source apportionments were verified regarding topography, industrial boundary, farmer density, and traffic flow. It was estimated that Mo, Co, Ni, and V were affected by slope; the enrichment of Hg and As was the result of agricultural activities; Cd, Mn, Cr, and Zn were affected by industrial waste diffusion; and Pb, Zn, Cu, Cd, and Hg were related to transportation. To a certain extent, agricultural fertilization and pesticide application have partially controlled soil fertility and pollution (Hg and As).

Characteristics of Se in water-soil-plant system and threshold of soil Se in seleniferous areas in Enshi, China

Se-enrichment characteristics in water-soil-plant system and dietary Se status of local residents in seleniferous areas were investigated. Results showed that Se in well water might mainly derived from Se-enriched shales and coals, and Se mobility in seleniferous soils was relatively low with less than 6.7% bioavailable forms in high-Se areas. Soil Se with irrigation, precipitation and fertilization sources contributed more to soil Se than Se-enriched shales and coals in low-Se areas, resulting in slightly higher mobility of Se in low-Se soils. Se concentration in edible parts of main crops ranged from 0.005 mg kg−1 to 4.17 mg kg−1, and cereal plants had a higher Se-enrichment ability than tuber plants. The probable dietary Se intake (PDI) in high-Se areas was decreased to 959.3 μg d−1 in recent years, which might be attributed to tap water as drinking water in recent year rather than well water-dependent and changes in dietary structure, but still far above the permissible value of 400 μg d−1. Reducing cereal-derived dietary Se intake is an important strategy to better Se nutrition status in high-Se areas. After synthesis considerations on soil Se bioavailability and PDI of Se, the soil total Se of 4 mg kg−1 and the soil available Se content of 0.32 mg kg−1 were proposed to be the reference threshold values of soil Se excess in high-Se areas in Enshi, respectively.

Long-term vegetable production significantly reduces the selenium adsorption in two typical plastic shed soils

Long-term vegetable production in plastic shed soil (PSS) and related soil management strategies stimulate the changes of soil properties and the mobilization of selenium (Se), causing risks to environmental soil quality and human health. Nevertheless, whether the greenhouse management (defined by the years of greenhouse vegetable production) and the greenhouse type have a synergistic effect on Se mobility in PSSs subjected to long-term vegetable production is still unclear. This study investigated the joint effects of greenhouse management and the properties of PSS on Se adsorption and desorption in soils collected from solar greenhouses (SG) and round arch plastic greenhouses (PG), which has been continuously cultivated respectively for 20 and 30 years in Tongshan County, Jiangsu Province, East China. Herein, we carried out a field survey coupled with batch experiments to investigate the adsorption and desorption behavior of Se in the SG and PG soils with different years of vegetable production. Results showed that greenhouse management had differentiated effects on soil properties and Se mobility in the two typical PSSs. Compared to the open field soils, long-term vegetable production generally increased soil nutrients (i.e., total P (TP), available P (AvP)), OM and Se desorption in the SG soil, while it significantly decreased Se adsorption in both typical PSSs. The soil pH had a downward trend with the increase of the years of vegetable production. The longer years of greenhouse vegetable production, the less Se adsorption capacity occurred in PSSs with annual decrease rates of 0.48 and 0.24 mg kg−1 yr−1 for the SG and PG soil, respectively, at 1.0 mg L−1 Se addition. Conversely, the ratio of Se desorption of the SG soils increased with longer vegetable production. The results of partial least squares regression (PLSR) explained the differences in Se adsorption and desorption between the SG and PG soil due to the changes in soil properties caused by the greenhouse management and greenhouse type. The fewer Se application is therefore recommended in the SG soils than in the PG soils after long-term greenhouse vegetable production.

Geographical distribution of trace elements (selenium, zinc, iron, copper) and case fatality rate of COVID-19: a national analysis across conterminous USA.

Severe outcome particularly death is the largest burden of COVID-19. Clinical observations showed preliminary data that deficiency in certain trace elements, essential for the normal activity of immune system, may be associated with worse COVID-19 outcome. Relevant study of environmental epidemiology has yet to be explored. We investigated the geographical association between concentrations of Se, Zn, Fe and Cu in surface soils and case fatality rate of COVID-19 in USA. Two sets of database, including epidemiological data of COVID-19 (including case fatality rate, from the University of John Hopkinson) and geochemical concentration data of Se, Zn, Fe and Cu in surface soils (from the National Geochemical Survey), were mapped according to geographical location at the county level across conterminous USA. Characteristics of population, socio-demographics and residential environment by county were also collected. Seven cross-sectional sampling dates, with a 4-week interval between adjacent dates, constructed an observational investigation over 24 weeks from October 8, 2020, to March 25, 2021. Multivariable fractional (logit) outcome regression analyses were used to assess the association with adjustment for potential confounding factors. In USA counties with the lowest concentration of Zn, the case fatality rate of COVID-19 was the highest, after adjustment for other influencing factors. Associations of Se, Fe and Cu with case fatality rate of COVID-19 were either inconsistent over time or disappeared after adjustment for Zn. Our large study provides epidemiological evidence suggesting an association of Zn with COVID-19 severity, suggesting Zn deficiency should be avoided.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10653-022-01204-0.

Understanding the translocation and bioaccumulation of cadmium in the Enshi seleniferous area, China: Possible impact by the interaction of Se and Cd

Selenium (Se) plays an indispensable role in minimizing cadmium (Cd) hazards for organisms. However, their potential interactions and co-exposure risk in the naturally Se–Cd enriched paddy field ecosystem are poorly understood. In this study, rice plants with rhizosphere soils sampled from the Enshi seleniferous region, China, were investigated to resolve this confusion. Here, translocation and bioaccumulation of Cd showed some abnormal patterns in the system of soil-rice plants. Roots had the highest bioaccumulation factors of Cd (range: 0.30–57.69; mean: 11.86 ± 14.32), and the biomass of Cd in grains (range: 1.44–127.70 μg, mean: 36.55 ± 36.20 μg) only accounted for ∼10% of the total Cd in whole plants (range: 14.67–1363.20 μg, mean: 381.25 ± 387.57 μg). The elevated soil Cd did not result in the increase of Cd concentrations in rice grains (r2 = 0.03, p > 0.05). Most interestingly, the opposite distribution between Se and Cd in rice grains was found (r2 = 0.24, p < 0.01), which is contrary to the positive correlation for Se and Cd in soil (r2 = 0.46, p < 0.01). It is speculated that higher Se (0.85–11.46 μg/g), higher Se/Cd molar ratios (mean: 5.42 ≫1; range: 1.50–12.87), and higher proportions of reductive Se species (IV, 0) of the Enshi acidic soil may have the stronger capacity of favoring the occurrence of Se binding to Cd ions by forming Cd–Se complexes (Se2− + Cd2+ =CdSe) under reduction conditions during flooding, and hence change the Cd translocation from soil to roots. Furthermore, the negative correlation (r2 = 0.25, p < 0.05) between the Cd translocation factor (TFwhole grains/root) and the roots Se indicates that Cd translocation from the roots to rice grains was suppressed, possibly by the interaction of Se and Cd. This study inevitably poses a challenge for the traditional risk assessment of Cd and Se in the soils-crops-consumers continuum, especially in the seleniferous area.

Geochemical characteristics and ecological effects of Se and Zn in topsoil in Western Fuling of Chongqing

A large area of soil in China is deficient in selenium (Se) and zinc (Zn)，meanwhile, Se and Zn are essential trace elements for human body, so it is of great significance to find Se and Zn rich soil to cultivate crops. Based on the data of Se and Zn in topsoil, crops and root soil obtained from 1:50000 land quality geochemical survey, this paper taking the western area of Fuling in Chongqing as the research area, studies the content and spatial distribution characteristics of Se and Zn in soil and crops, and analyzes the enrichment law of Se and Zn in agricultural crops. The results show that the average values of Se and Zn in the topsoil of the study area are 0.265mg/kg and 77.56mg/kg respectively. There are some differences in the contents of Se and Zn in different geological backgrounds, soil parent materials and soil types. The high value areas of Se and Zn are mainly distributed in the exposed areas of Triassic carbonate; in the study area, the average contents of Se and Zn in maize seeds are 0.029mg/kg and 20.752mg/kg respectively, and the enrichment rates are 96% and 82% respectively. The average contents of Se and Zn in rice seeds are 0.032mg/kg and 11.463mg/kg respectively, and the enrichment rates are 13.3% and 5% respectively. The bioaccumulation coefficients of Se and Zn in maize are higher than that in rice, and the availability of Se and Zn elements in maize root soil is higher.The results can provide geochemical basis for developing characteristic land resources, functional agriculture and promoting rural revitalization in Fuling District.

Selenium bioconcentration in Canadian oat (Avena sativa) from soils treated with nanoscale elemental selenium

Development of selenium (Se)-enriched agricultural products can increase human daily dietary Se intake in Se-deficient areas. Canadian oat (Avena sativa L. cv. Saddle) is one of the common cereal grains in the world. Previous studies have shown that Se accumulation in oat can be significantly affected by soil Se, but few have dealt with different chemical forms of Se, including emerging nanoscale elemental Se particles (SeNPs). Because SeNPs have unique chemical and physical properties in comparing with bulk elemental Se, this laboratory study determined the effects of soil SeNP treatments of 0, 1, 5, and 10 mg/kg on Se bioconcentration in oat grain, compared with bulk elemental Se or selenate (Na2SeO4). The results showed that the soil SeNP treatments significantly increased Se concentrations in oat grain with an increase in the treatment level from 1 to 10 mg/kg (P &lt; 0.05). The distribution of Se accumulated in oat tissues followed a descending order of root and grain &gt; husk &gt; stem and leaf. While the grain yield was reduced with the higher soil selenate treatments of 5–10 mg/kg, the soil SeNP treatment of 1–10 mg/kg significantly enhanced the oat grain yield, compared with the control. Concentrations of Se in oat grains in the soil SeNP treatments were approximately 7–20-fold higher than were the concentrations of those in the soil bulk elemental Se treatments, but were about 7–26% of the concentrations in oat grains in the soil selenate treatments. This study demonstrated that nanoscale elemental Se particles could be used for development of soil Se-amended fertilisers for Se-biofortified oat.

Accumulation of zinc, iron and selenium in wheat as affected by phosphorus supply in salinised condition

Biofortification of zinc (Zn), iron (Fe) and selenium (Se) in crops could be affected by environmental factors such as soil salinity and phosphorus supply levels, as well as by the genotypic effect. Two pot experiments were conducted with one examined the effects of P supply and salinity on plant growth and Zn, Fe and Se uptake in wheat, and the other examined genotypic differences in Zn, Fe and Se accumulation among 20 wheat genotypes. The results of the first pot study showed significant interactive effects between P supply and salinity on Zn, Fe and Se accumulation. Increasing salinity at the same P supply level increased shoot Zn concentrations, but significantly decreased total shoot Zn amount owing to decreased aboveground biomass. An increased accumulation of total shoot Fe and Se in P-added treatments, relative to the no-P treatments, was mainly due to increased aboveground biomass. The results of the second pot study showed substantial genotypic variations in Zn, Fe and Se accumulation; principal component analysis (PCA) suggested that agronomic traits and nutrient accumulation were controlled by independent genetic mechanisms. These results indicated that the amount of P supply is a key factor regulating biomass and accumulation of Zn, Fe and Se in certain saline soils; the sizable genotypic difference in Zn, Fe and Se accumulation observed in salinised conditions has provided potential scope for genetic improvement by breeding strategies.

Metal and metalloid bioaccumulation in three centipedes (Chilopoda)

Three centipede species (Clinopodes flavidus, Cryptops anomalans and Eupolybothrus transsylvanicus) were used as bioindicators of trace metal and metalloid pollution in Belgrade, Serbia. The concentrations of 13 elements (the metals Mn, Co, Ni, Cu, Zn, Rb, Sr, Cd, Tl, Pb and U and metalloids As, Se) in whole animals and soil were measured by inductively coupled plasma mass spectrometry (ICP-MS). Differences in the concentrations of some elements in the analyzed species were observed, both in response to the sites and between species. In most cases, the trace element concentrations were higher in centipedes from a polluted site (an industrial area near a busy street with heavy traffic) but C. anomalans and E. transsylvanicus had higher Mn concentrations at an unpolluted site (a deciduous woodland on Mt. Avala). C. flavidus was a good bioindicator for detecting differences between Zn, Se and Cd. C. flavidus and C. anomalans were more efficient in accumulating Zn than E. transsylvanicus. It appears that C. anomalans poorly accumulated Cd, unlike C. flavidus and E. transsylvanicus, which accumulated Cd according to the high bioaccumulation factor (BAF) values. We conclude that the centipedes C. flavidus, C. anomalans and E. transsylvanicus can be used as suitable bioindicators of trace element exposure. Their ability to accumulate trace elements was different and depends on their physiology and lifestyle as well as the route of exposure.

Characteristics of Se in Water-Soil-Plant System and Threshold of Soil Se Excess in Seleniferous Areas in Enshi, China

Characteristics of Se in Water-Soil-Plant System and Threshold of Soil Se Excess in Seleniferous Areas in Enshi, China

Selenium application methods and rates for biofortification of common bean and their residual effects on Mombaça grass

Context Agronomic biofortification is recognised as being an important strategy to increase selenium (Se) contents in food crops. The effectiveness of agronomic biofortification may differ depending on the methods of how Se is applied in agricultural systems. Aims This study aimed to evaluate different Se application methods (involving Se addition in the soil via Se-enriched fertilisers and foliar Se application) and rates for biofortification of common bean and to assess residual effects of soil Se additions for biofortification of Mombaça grass grown after the common bean. Methods Both experiments were carried out in a greenhouse. In the first cultivation (common bean), Se (as sodium selenate) was added at 0.0, 0.2, 0.4, 0.6, and 0.8 mg/dm3 using six different methods, as follows: Se-enriched monoammonium phosphate, Se-enriched urea, Se-foliar application, Se-enriched monoammonium phosphate + Se-enriched urea, Se-enriched monoammonium phosphate + Se-foliar application, and Se-enriched urea + Se-foliar application. To evaluate the residual effects of soil Se additions, Mombaça grass plants were grown after the common bean (second cultivation) without additional Se supply. Key results Agronomic biofortification effectiveness varied among methods, with higher Se contents in common bean grains being found when Se-enriched urea, Se-foliar application, and the combination of both methods were applied. Conclusions Selenium addition methods via soil using fertilisers as carriers to add Se, including Se-enriched monoammonium phosphate, showed a potential of residual effects on succeeding crops since these methods were efficient for increasing Se contents in Mombaça grass shoots.

Lead and other elements-based pollution in soil, crops and water near a lead-acid battery recycling factory in Bangladesh

Lead (Pb) pollution in the environment predominantly occurs through anthropogenic activities, which pose significant threats to human health and that of biota. In this study, Pb and other elements were investigated in different soils (n = 52), crops (n = 24) and water (n = 13) around a lead-acid battery (LAB) recycling workshop in southwestern Bangladesh. Most of the elements’ concentrations (except Se and Ag) in soil were lower than the background concentrations. However, excessive concentrations of Pb were found in both surface (966 ± 2414 mg kg−1 at 0–15 cm) and subsurface (230 ± 490 mg kg−1 at 15–30 cm) soil. Although no definitive pattern or direction in elemental concentration in soil was observed, relatively higher concentrations of most elements were detected at the southeast part of the factory. The LAB factory, brick kiln, agricultural and geogenic activities might be the sources of these elements in soil. Extremely high amounts of Cr, As, Cd, and Pb were found in the food crops around the area. In particular, the Pb concentrations were 114 ± 155 and 665 ± 588 mg kg −1 dry weight in rice grain and straw, respectively, which reflected the emissions of Pb from the LAB recycling workshop. Moreover, 40% and 100% of the groundwater samples exceeded, respectively, the WHO provisional guideline values for As (0.01 mg L−1) and Pb (0.05 mg L−1). Consequently, a high level of Pb contamination in the soil was observed while assessing different soil pollution indices. Human health risk assessment indicated severe carcinogenic (from Pb, As, and Cr intake) and non-carcinogenic (from Pb, As, Co, Cr, Ni and Sb intake) health risks are associated with rice and groundwater consumption. It is concluded that all LAB recycling workshops should be better managed to prevent Pb pollution from seeping into the environment.

Selenium in Wheat from Farming to Food.

Selenium (Se) plays an important role in human health. Approximately 80% of the world's population does not consume enough Se recommended by the World Health Organization. Wheat is an important staple food and Se source for most people in the world. This review summarizes literature about Se from 1936 to 2020 to investigate Se in wheat farming soil, wheat, and its derived foods. Se fortification and the recommended Se level in wheat were also discussed. Results showed that Se contents in wheat farming soil, grain, and its derived foods around the world were 3.8-552 μg kg-1 (mean of 220.99 μg kg-1), 0-8270 μg kg-1 (mean of 347.30 μg kg-1), and 15-2372 μg kg-1 (mean of 211.86 μg kg-1), respectively. Adopting suitable agronomic measures could effectively realize Se fortification in wheat. The contents in grain, flour, and its derived foods could be improved from 93.94 to 1181.92 μg kg-1, from 73.06 to 1007.75 μg kg-1, and from 86.90 to 587.61 μg kg-1 on average after leaf Se fertilizer application in the field. There was a significant positive correlation between the Se content in farming soil and grain, and it was extremely the same between the foliar Se fertilizer concentration rate and the grain Se increased rate. The recommended Se fortification level in cultivation of wheat in China, India, and Spain was 18.53-23.96, 2.65-3.37, and 3.93-9.88 g hm-2, respectively. Milling processing and food type could greatly affect the Se content of wheat-derived food and should be considered seriously to meet people's Se requirement by wheat.

Circulation of Selenium in the Environment

Abstract In order to function properly, every living organism must have favourable conditions for its operation, i.e. it must be systematically supplied with the necessary nutrients. On the example of selenium (Se), it can be seen how important is the right balance between providing the right amount of it, without exceeding the level above which it is toxic. The amount of Se in soil is closely correlated with its content in the parent rock; therefore, it differs depending on the soil type and may change even in a small area. Considerable dispersion of the element in the soils of Poland is related to their formation, mainly from dump materials of various glaciations. The problem of maintaining the balance between deficiency and excess of Se in the diet of humans and animals is related primarily to the uneven distribution of this element in nature. In this paper, on the basis of scientific literature, the current issues related to the deficiency and excess of Se in the soil and its possible sources are presented. The relationship between the content in the soil and the supply of Se in plants, animals and humans was also shown. The aim of this study was to summarise the state of knowledge on the complexity of Se occurrence in the environment and its importance in the soil-plant-animals-human system.

Selenium alleviates toxicity in Amaranthus hypochondriacus by modulating the synthesis of thiol compounds and the subcellular distribution of cadmium

As a beneficial element, Selenium (Se) reduces toxic cadmium (Cd) absorption in many crops, but the effects of Se on Cd hyperaccumulator plants are unclear. This study examined the effects of Se on Amaranthus hypochondriacus (K472). The results showed that Se increased antioxidant enzyme activities, reduced Cd concentrations and toxicity, restored cell viability, and enhanced photosynthesis; these effects increased the biomass of roots, stems, and leaves by 59.87%, 53.85%, 44.19%, respectively, and these values exceeded the biomass of roots and stems in untreated control plants by 56.69% and 15.37%, respectively. Moreover, Se promoted PC synthesis, stably chelated Cd in the form of PC3 and PC4 and transported PC-Cd to vacuoles. Furthermore, Se protected organelles and reduced Cd migration by increasing Cd levels in cell walls and vacuoles. Interestingly, although the Cd content in K472 was decreased, Se maintained the total extracted Cd concentrations and its remediation efficiency by improving biomass and increased tolerance to Cd by approximately 5 times. The experimental results provide novel insights and methods for mitigating toxicity, promoting growth, and broadening the engineering application scope of K472; these results also provide a theoretical basis for further application of Se in soil with high Cd concentrations.

Arbuscular mycorrhizal fungi reverse selenium stress in Zea mays seedlings by improving plant and soil characteristics

Selenium (Se) is a beneficial trace element for certain animals including humans, while remaining controversial for plants. High Se concentration in soil is toxic to plants especially at seedling stage of the plants. Although, arbuscular mycorrhizal fungi (AMF) are important for plant stress resistance; but the mechanisms by which AMF alleviate Se stress in crop seedlings are unclear. Therefore, we investigated the potential strategies of AMF symbiosis to alleviate Se stress in maize (Zea mays) from plants and soil perspectives. Results showed that Se stress (Se application level > 5 mg kg−1) significantly inhibited leaf area, shoot dry weight, and root dry weight of maize (P < 0.05). In contrast, AM symbiosis significantly improved root morphology, increased nitrogen and phosphorus nutrition, promoted shoot growth, inhibited the transport of Se from soil/roots to shoots, and then diluted the concentration of Se in shoots (32.65–52.80%). In general, the response of maize growth to AMF was mainly observed in shoots rather than roots. In addition, AMF inoculation significantly increased the easily extractable glomalin-related soil protein and organic matter contents and decreased the availability of soil Se to the plant. Principal component analysis showed that AMF promoted growth and nutrition uptake of maize was the most dominant effect of Se stress alleviation, followed by the decrease of soil Se availability, limiting Se transport from soil/roots to shoots. Moreover, the expression of Se uptake-related ion transporter genes (ZmPht2, ZmNIP2;1, and ZmSultr1;3) in maize roots were down-regulated upon AM symbiosis which resultantly inhibited the uptake and transport of Se from soil to maize roots. Thus, AMF could impede Se stress in maize seedlings by improving plant and soil characteristics.

Influence of arbuscular mycorrhizal fungi on selenium uptake by winter wheat depends on the level of selenate spiked in soil

Selenium (Se) deficiency has been a public health concern for years. Arbuscular mycorrhizal fungi (AMF) play an essential role in improving Se uptake in crops, but related mechanisms still remain unclear. To explore the influence of AMF on uptake of Se in winter wheat, a pot experiment was conducted to inoculate wheat with Funneliformis mosseae (F.m) or not under different levels of selenate in soil. The present results indicated that inoculation of F.m significantly (p < 0.05) increased Se concentration in shoots and roots of wheat under low level of selenate (≤5.0 mg kg−1) treatments, while the contrary pattern was recorded under high level of selenate (15 and 20 mg kg−1) treatments. Moreover, inoculation of F.m significantly increased concentration of available Se in soil by 4.68–34.05%. Under selenate ≤5 mg kg−1 treatments, the expression of TaeSultr1;1 and TaeSultr1;3 in roots of mycorrhizal wheat was significantly up-regulated by 3.06–5.53 and 0.63–5.12 times, while reached saturation under selenate >5 mg kg−1 treatments. In addition, partial least squares path modeling (PLS-PM) showed that inoculation of AMF directly affected the expression of sulfate transporter and that both sulfate transporter and soil Se fractions played a significant positive effect on plant Se content. The present study indicated that AMF on Se concentration in winter wheat depends on the level of selenate spiked in soil and added to our understanding of the functions and applications of AMF on crop Se absorption.

The influence of sea animals on selenium distribution in tundra soils and lake sediments in maritime Antarctica

The biogeochemical behavior of selenium (Se) has been extensively studied in Se-enriched or Se contaminated soils at low and middle latitudes. However, the Se distribution patterns have not been studied in tundra ecosystems of remote Antarctica. Here, the soils/sediments were collected from penguin and seal colonies, their adjacent tundra and lakes, tundra marsh, human-activity areas, normal tundra and the periglacial in maritime Antarctica, and total Se and seven operationally defined Se fractions were analyzed. Overall the regional distribution of Se levels showed high spatial heterogeneity (coefficient of variation, CV = 114%) in tundra soils, with the highest levels in penguin (mean 6.12 ± 2.66 μg g−1) and seal (mean 2.29 ± 1.43 μg g−1) colony soils, and the lowest in normal tundra soils and periglacial sediments (<0.5 μg g−1). The contribution rates of penguins and seals to tundra soil Se levels amounted to 91.7% and 78.0%. The lake sediment Se levels (mean 2.15 ± 0.87 μg g−1) close to penguin colonies were one order of magnitude higher than those (mean 0.49 ± 0.87 μg g−1) around normal tundra. Strong positive correlations (p < 0.01) of Se concentrations between lake sediments and adjacent tundra soils, and lower Se: P (<0.001) and S: P (<1) ratios in the lake sediments close to penguin colonies, indicated the infiltration or leaching of penguin guano as the predominant Se source in lake sediment. The Se species in penguin and seal guano were dominated by SeCys2 (76.6%) and SeMet (73.5%), respectively. The evidence from the predominant proportions of total organic matter-bound Se (Seom, 67%–70% of total Se) in penguin or seal colony soils further supported penguin or seal guano had a great influence on the distribution patterns of Se fractions in the tundra. This study confirmed that sea animal activities transported substantial amount Se from ocean to land, and significantly altered the biogeochemical cycle of Se in maritime Antarctica.

Combining Selenium Biofortification with Vermicompost Growing Media in Lamb’s Lettuce (Valerianella locusta L. Laterr)

Leafy vegetables are a daily part of the human diet all over the world. At the same time, a worldwide problem of Se malnutrition is present in human populations, mostly due to low soil Se contents. As plants represent the main source of this element in the human diet, with Se being an essential trace element for humans and animals, plant foods containing Se can be used as an efficient means of increasing the Se in the human diet, as well as in animal feed (biofortification). At the same time, the production of growing media relies on limited peat reserves. The use of earthworms facilitates the production of composted organic masses mostly consisting of organic waste, called vermicompost. The aim of this study was to investigate the influence of three different growing media (commercial peat media, vermicompost, and a 1:1 mixture) on Se biofortification’s efficacy and yield in lamb’s lettuce. The Se biofortification was performed with sodium selenate (Na2SeO4). It was shown that biofortification increased the Se contents such that a mass of only 48.9 g of fresh leaves contained enough Se for the recommended daily intake in human nutrition (55 µg Se/day), which represents a significant potential for solving Se malnutrition. Furthermore, the use of a 1:1 vermicompost–commercial substrate mixture showed a similar performance to the peat growing medium, contributing to the preservation of peat reserves.

Spatial distribution and environmental impact factors of soil selenium in Hainan Island, China

Selenium is an essential micronutrient for the human body, given its various health benefits. However, Se deficiency is widespread globally, and dietary adjustment is a feasible way to supplement people's Se daily intake. The Multi-purpose Regional Geochemical Survey (NMPRGS) conducted in Hainan Island found an abundance of Se-rich soil. These Se resources have been utilized to grow naturally Se-rich produce. However, insufficient research has been conducted into the spatial distribution and enrichment of soil Se in Hainan Island. This paper analysed the effect of the environmental impact factors (parent rock, precipitation, etc.) on soil Se, using data from the NMPRGS database. The results showed that, in comparison to the baseline value of Chinese soil, the enrichment degree of Se in the topsoil of Hainan Island was higher, but its distribution was uneven. The parent rock, precipitation, soil type, and soil characteristics all affect the concentration and spatial distribution of regional soil Se. Geographically weighted regression showed that Iodine, pH, SOC, and TFe2O3 have a non-stationarity spatial relationship with Se. There was a significant correlation between soil Se and Chemical alteration index (CIA) in granite areas, while CIA was also related to mean annual precipitation (MAP). The concentration enrichment factor values of Se show that the external input of Se in high MAP areas is significantly higher than that in low MAP areas. Based on these results, three important environmental impact factors on soil Se enrichment at the regional scale in Hainan Island were defined: 1) Se-rich rocks; 2) precipitation; 3) SOC. These results can provide guidance for the planning and layout of Se-rich agriculture.