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This study aims to evaluate the pollution characteristics of rice cultivated in Hainan Island and assess the health risks to humans through consuming rice. Results indicate that except lead (Pb), the mean contents of other heavy metals in rice are all within the standard limits. According to the spatial distribution and pollution indices of heavy metals, rice is severely polluted with Pb and the contaminated areas are mainly distributed in the west and northeast regions of Hainan Island. Analyses on the non-carcinogenic risks indicate that the target hazard quotients (THQs) of individual heavy metals are significantly different in the study area, and the THQs of chromium (Cr) and arsenic (As) are above 1, implying that people consuming the local rice are susceptible to health risks caused by Cr or As, which is significantly different form the results of single pollution indices of Cr, As, and Pb. This result is mainly related to the original concentrations and reference oral dose for ingesting (RfDing) of Cr, As, and Pb. As for the assessment of carcinogenic risk, it demonstrates that Cr and As may have adverse effects on inhabitants consuming local rice. [ABSTRACT FROM AUTHOR]

Toxic elements, such as Cd and Pb are of primary concern for soil quality and food security owing to their high toxicity and potential for bioaccumulation. Knowledge of the spatial variability of Cd and Pb in soil–rice systems across the landscape and identification of their driving factors are prerequisites for developing appropriate management strategies to remediate or regulate these hazardous contaminants. Considering the role of rice (Oryza sativa) as a dietary staple in China, this study aimed to examine the distribution patterns and drivers of Cd and Pb in tropical soil–rice systems across Hainan Island. To achieve this goal, 229 pairs of representative paddy soil and rice samples combined with a set of environmental covariates at the island scale were systematically analyzed. Arithmetic mean values (AMs) of Cd and Pb in rice were 0.080 and 0.199 mg kg−1, and exceeded the standard limits by 27.1% and 22.7%, respectively. We found that the AMs of Cd and Pb concentrations in paddy soil were 0.294 and 43.0 mg kg−1. Additionally, Cd in 29.26% of soil samples and Pb in 11.35% of soil samples exceeded the risk screening value for toxic elements. The enrichment factor generally showed that soil Cd and Pb on Hainan Island were both moderately enriched. Results obtained from both Spearman's correlation and stepwise regression analyses suggest that the concentrations of soil Cd and Pb are significantly influenced by the soil Na and Fe concentrations. Specifically, an increment of 1 g kg−1 in soil Na caused a rise of soil Cd and Pb by 57.1 mg kg−1 and 34.4 mg kg−1, respectively, while an increase of 1 g kg−1 in soil Fe resulted in a rise by 25.0 mg kg−1 and 14.5 mg kg−1. Similarly for rice grains, an increment of 1 g kg−1 in soil Ca resulted in a rise of rice Pb by 30.8 mg kg−1, whereas an increase of 1 g kg−1 in soil Mg led to a decrease in rice Pb by 14.8 mg kg−1. However, no significant correlation between soil Se and rice Cd concentrations was found. Furthermore, the result of geographically weighted regression revealed that the impacts of soil Na, Ca, Fe, and Mg on rice Cd were more significant in the western region, whereas the effects of soil Na and Fe on rice Pb were stronger in the northeastern region. This study provides new insights for the identification of factors influencing the distribution and accumulation of Cd and Pb in tropical island agroecosystems. [Display omitted] • Effects of environmental factors on Cd and Pb in island agroecosystem were analyzed. • Hainan Island, China had relatively high soil concentrations of Cd and Pb. • Na and Fe concentrations significantly affected soil Cd and Pb across the island. • Data suggest Hainan residents may be exposed to high levels of Cd/Pb in local rice. • Effects of soil properties on Cd and Pb in rice grains showed regional differences. [ABSTRACT FROM AUTHOR]

Selenium (Se) and zinc (Zn) are essential microelements for humans with crucial biological functions. In this study, we determined Se and Zn concentrations in soils and rice grains on Hainan Island and investigated how their spatial distributions are related to soil mineral elements, topography, and vegetation coverage. Overall, the concentrations of Se and Zn in soils were higher than the background values for Chinese soil; the Se concentrations in rice grains were higher than the threshold value for Se deficiency in grains, but Zn concentrations were lower than the proposed critical concentration. Both Spearman's correlation and stepwise regression analysis showed that the concentrations of soil Fe and Ca significantly affected soil Se and Zn: a difference of 1 g kg−1 in soil Fe changed soil Se by 2.820 μg kg−1 and soil Zn by 0.785 mg kg−1, respectively, while a difference of 1 g kg−1 in soil Ca changed soil Se by 3.249 μg kg−1 and soil Zn by 0.356 mg kg−1, respectively. For rice grains, Se and Zn concentrations decreased with increasing elevation; every 100 m increase in elevation could decrease Se by 0.022 mg kg−1 and Zn by 0.912 mg kg−1. Moreover, the impact of Fe and Ca on soil Zn was relatively strong in the northeast region, while the influence of elevation on rice grain Se was more significant in the central region. The findings contribute to a better understanding of factors driving the distribution of Se and Zn in soils and crops. Image 10175 • Effect of soil chemistry, topography and vegetation on soil–rice Se/Zn was studied. • Hainan rice grains were relatively high in Se but low in Zn. • Soil mineral composition had a significant impact on Se and Zn contents in soils. • Soil-Fe difference of 1 g kg−1 changed soil Se by 2.820 μg kg−1 and Zn by 0.785 mg kg−1. • Se and Zn contents in rice grains decreased with increasing elevation. [ABSTRACT FROM AUTHOR]