Boron contamination and its risk management in terrestrial and aquatic environmental settings.

Boron (B) is released to terrestrial and aquatic environments through both natural and anthropogenic sources. This review describes the current knowledge on B contamination in soil and aquatic environments in relation to its geogenic and anthropogenic sources, biogeochemistry, environmental and human health impacts, remediation approaches, and regulatory practices. The common naturally occurring sources of B include borosilicate minerals, volcanic eruptions, geothermal and groundwater streams, and marine water. Boron is extensively used to manufacture fiberglass, thermal-resistant borosilicate glass and porcelain, cleaning detergents, vitreous enamels, weedicides, fertilizers, and B-based steel for nuclear shields. Anthropogenic sources of B released into the environment include wastewater for irrigation, B fertilizer application, and waste from mining and processing industries. Boron is an essential element for plant nutrition and is taken up mainly as boric acid molecules. Although B deficiency in agricultural soils has been observed, B toxicity can inhibit plant growth in soils under arid and semiarid regions. High B intake by humans can be detrimental to the stomach, liver, kidneys and brain, and eventually results in death. Amelioration of soils and water sources enriched with B can be achieved by immobilization, leaching, adsorption, phytoremediation, reverse osmosis, and nanofiltration. The development of cost-effective technologies for B removal from B-rich irrigation water including electrodialysis and electrocoagulation techniques is likely to help control the predominant anthropogenic input of B to the soil. Future research initiatives for the sustainable remediation of B contamination using advanced technologies in soil and water environments are also recommended.

Effect of Se-Enriched Irrigation Water on the Biomass Production and Elemental Composition of Green Bean, Cabbage, Potato and Tomato.

Additional Selenium (Se) intake may be recommended in areas of Se deficiency to prevent various human diseases. One possibility for this is biofortification. In this experiment, the effect of irrigation water containing 100 and 500 µg L-1 Se, in the form of Na2SeO4, on green bean, cabbage, potato and tomato was investigated in a greenhouse pot experiment with sand, silty sand and silt soils. The chlorophyll content index was usually improved by Se and was significantly higher in potato in sand and silty sand and in tomato in silty sand and silt soils. The Se content of edible plant parts increased 63-fold in the 100 µg L-1 Se treatment and almost 400-fold in the 500 µg L-1 Se treatment, averaged over the four species and the three soils. Irrigation water with a Se content of 100 µg L-1 may be suitable for the production of functional food in the case of green beans, potatoes and tomatoes. However, due to its greater Se accumulation, cabbage should only be irrigated with a lower Se concentration. The use of Se-enriched irrigation water might be a suitable method for Se biofortification without a significant reduction in plant biomass production and without a remarkable modification of other macro- and microelement contents.

Effect of the Boron Concentration in Irrigation Water on the Elemental Composition of Edible Parts of Tomato, Green Bean, Potato, and Cabbage Grown on Soils With Different Textures.

The most important environmental source of boron (B) contamination is irrigation water. The data on the effect of B on the elemental composition in the edible parts of vegetables are scarce. A greenhouse pot experiment investigated the effect of irrigation water containing 0.1 and 0.5 mg/L B on the biomass, elemental (e.g., B, Mg, K, Fe, Cu, and Zn) composition, and photosynthetic parameters of tomato (Solanum lycopersicum), green bean (Phaseolus vulgaris), potato (Solanum tuberosum), and cabbage (Brassica oleracea) plants grown on 10 kg of sand, silty sand, or silty soil. The biomass of the edible part was unaffected by B treatment. The soil type determined the effect of B irrigation on the elemental composition of vegetables. The B content increased by 19% in tomatoes grown on silty soil. The 0.1 mg/L B treatment facilitated tomato fruit ripening on all soils, and the 0.5 mg/L B treatment doubled its chlorophyll content index (CCI) on silty soil. The 0.5 mg/L B treatment negatively affected the nutritional value of green beans on all soils, decreasing the Fe and K contents by an average of 83 and 34%, respectively. The elemental composition of potato was unaffected by the treatments, but the CCI of potato leaves increased in the 0.5 mg/L B treatment by 26%. The B content was increased by 39% in cabbages grown on light-textured soils. In conclusion, B concentration of up to 0.5 mg/L in irrigation water had no significant beneficial or adverse effect on the investigated vegetables, but 0.1 mg/L B treatment could shorten tomato fruit maturation time on B-poor soils. The B levels in vegetables remained suitable for human consumption.