# Usage of Si, P, Se, and Ca Decrease Arsenic Concentration/Toxicity in Rice, a Review
### Calcium (Ca) and As  
Ca is not only a necessary nutrient for plants [138], but it plays significant roles as in preventing leakage of solutes from the cytoplasm and regulating enzymatic and hormonal activity in plants [139,140]. Multiple kinds of research have also demonstrated that Ca\({}^{2+}\) increases the amplification of cell walls and that sufficient levels of Ca\({}^{2+}\) in the external environment are required to maintain cell membrane selection and integrity [138]. Ca is involved in metabolic processes of absorption of other nutrients and challenges other positively charged ions like Mg\({}^{2+}\), K\({}^{+}\), Na\({}^{+}\); therefore, excessive use of these positively charged ions reduces Ca uptake by plants [141]. Studies have shown that high levels of Ca\({}^{2+}\) can change the increase and removal of sodium (Na) in plant roots, which are subjected to the stress of NaCl [139]. In addition, roots with high levels of Ca\({}^{2+}\) often retain their concentration of K\({}^{+}\), while roots with low Ca\({}^{2+}\)often cannot [142,143]. Ca participates in signalling various physiological and biochemical processes as a secondary messenger that mediates some cell and plant growth perspectives and responds to the different stresses [144,145]. Because in stress signalling, Ca\({}^{2+}\) is ubiquitous, it can be an essential node for cross-route discussion. Most of the stresses gain concentrations of cytosolic free Ca [146,147]. Four leading calcium-bound proteins families are known in plants: including calcium-dependent protein kinases (CDPK), calmodulin, calmodulin-like proteins, and calcineurin-like proteins B [148,149]. Recently, multitude studies have demonstrated which exogenous Ca reduces stresses in the environment, including the stress of toxic metals, by reducing metal uptake [138,150] and some studies have shown that the use of calcium peroxide (CaO\({}_{2}\)) helps reduce arsenic toxicity and mobility in soil and eliminates arsenic from water [151,152]. Nevertheless, data are limited about the effects of CaO\({}_{2}\) on arsenic accumulation and toxicity in crops grown in As-contaminated soils. Various studies have shown that CaO\({}_{2}\) can effectively reduce arsenic uptake by plants by reducing As mobility in the soil, but the mechanism of applying CaO\({}_{2}\) on the dynamics of As in flooded soil and arsenic uptake through rice is as yet unknown [153,154]. Nevertheless, creating aerobic conditions by water management like drainage is an excellent way to decrease As accumulation in rice grains. However, drainage operations are complex in some locations with a long rainy season and poorly drained soils. In this regard, oxygen-releasing compounds (ORC) can be an alternative to maintain aerobic conditions even in paddy soils [155,156]. CaO\({}_{2}\) is an ORC and added to water generates hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) and oxygen (O\({}_{2}\)). Due to the, chemical properties of CaO\({}_{2}\) it has been used as an oxidant to increase organic pollutant degradation like glyphosate, toluene, and polycyclic aromatic hydrocarbons in polluted