The Effect of Some Soil Amendments (Manure and Biochar) on the Bioaccumulation Capacity of Hexavalent Chromium by Two Species of (Salicornia Persica) and (Salicornia Perspolitana) From Contaminated Soil

: Heavy metals are among the most dangerous contaminants in the environment. Application of organic compounds and plant species with the ability to accumulate and stabilize 14 heavy metal in their organs is the best option for remediation of these elements in the soil. 15 Therefore, this study aimed to investigate the effects of manure and biochar on the accumulation 16 of heavy metals by Salicornia species. Two species of Salicornia ,including S. persica and S. 17 perspolitana, were cultivated outdoor in experimental pots. The effects of experimental 18 treatments ,including hexavalent chromium concentrations, manure ,and biochar on the two 19 studied species, were investigated. The results indicated a significant effect (P <0.05) of biochar 20 on the accumulation of heavy metals by two species , S. persica and S. perspolitana , so that 21 chromium concentrations in the roots and shoots were 258 and 5.41 mg/kg, respectively. Also, 22 chromium accumulations under manure treatments in the roots and shoots were 334.34 and 9.79 23 mg/kg, respectively. Plant dry weight and height for both species in manure treatment were 24 higher than control and biochar treatments. S. persica showed higher growth than S. perspolitana species. The content of photosynthetic pigments in both S.persica and S. perspolitana species under biochar treatment was higher than control and manure treatments. In general, one can 27 conclude that the accumulation of chromium in S. perspolitana was higher than in S. persica ,and 28 the application of biochar and manure amendments could stabilize chromium in soil and reduce 29 chromium accumulation in both S. persica and S. perspolitana species. 30


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Increased agricultural activities , as well as industrialization in recent decades, have significantly 33 resulted in the accumulation of various contaminants in the environment, especially in soil and 34 water. These contaminants enter into the environment through mining operations, discharge of 35 industrial effluents, pesticide-based agriculture, fertilizers, etc. , and are challenging and 36 problematic due to harmful effects on soil biological systems (Edao 2017). Removal of heavy 37 metals from soil could be a severe issue as heavy metals are special contaminants, which in 38 many cases, could remain in the soil for hundreds (even thousands) of years. Several methods 39 have been documented for removing heavy metals from contaminated soils. Despite being 40 efficient, conventional technologies are costly, time-consuming , and environmentally 41 destructive. Phytoremediation is defined as applying of various plants to reduce the chromium from soil and stated that Eucalyptus camaldeulensis had the highest capability to 73 uptake these contaminants from the soil. Salicornia, a halophyte and salt-tolerant plant, serves as 74 a suitable plant for phytoremediation of heavy metals due to its characteristic roots and the 75 ability to stabilize metals (Van Oosten et al. 2015). 76 Several studies have been carried out on the phytoremediation ability of Salicornia plant species 77 for removal of heavy metals other than chromium, but for the first time, we aimed to investigate    of 2 mm were considered as a germinated seed , and all the germinated seeds were counted on a 127 daily basis. Because no germination was observed from the 14th to the 16th day, the counting 128 was stopped on the 16th day. Also, the length of root and stem , as well as the length of seedling 129 (the sum of root length and stem length) was measured on the 16th day by an mm-sized ruler.

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Germination percentage, germination rate, seedling length, seed vigor index , and allometric 131 index were calculated based on the equations 2-1 to 2-5, respectively (Saberi et al. 2010          Applying of hexavalent chromium caused a significant reduction in chlorophyll contents. There

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The results concerning the effect of the studied treatments on the accumulation of metals in 424 Table 8 showed that the value of TF for heavy metals was lower than 1 in all treatments. 425 Therefore, both S. persica and S. perspolitana would serve as suitable species for 426 phytostabilization.
427 Table 8. Mean values of TF, BCF and BAC related to total chromium in S. persica and S.  Seed germination was the same as the control at a cadmium concentration of 5 mg/l, although the 452 stem length reduced by about 17% and the root length increased by about 22% compared to the 453 control treatment, but decreases in seed germination and seedling length was significant at a 454 concentration of 10 mg/l. Also, a cadmium concentration of 40 mg/l led to the death of most 455 alfalfa seedlings. Authors have reported delayed seedling emergence as a sign of cadmium 456 toxicity. Therefore, the results of the mentioned studies are consistent with the findings of this 457 investigation so that a decrease in the traits related to seed germination rate was observed with 458 increasing the concentration of heavy metals in both S. persica and S. perspolitana. 459 Heavy metals cause serious damage to the cell by inducing a lack of active oxygen production.

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Also, in a study, it was found that the Vigna radiata did not tolerate chromium concentrations 465 higher than 50 mg/l (Murtaza et al. 2018). In the present study, the results regarding the seedling 466 growth showed a similar trend, so that stem length also decreased with decreasing root length in 467 both S. persica and S. perspolitana species, which may be due to reduced nutrients. Therefore, 468 the present study confirmed that seed germination and seedling growth are affected by different    accumulation of heavy metals in the roots than that of the shoot to the complexation of these 543 metals with sulfhydryl groups, which prevented the transfer of these metals to the shoot. This 544 prevents the transfer of heavy metals to the food chain. Although the transfer of chromium from 545 the plant roots to the shoots is minimal, the transfer of chromium within the plant tissue depends 546 on its chemical form. The decreased chromium transport to plant shoots may be due to the 547 conversion of hexavalent to trivalent chromium within plants due to the tendency of trivalent 548 chromium to attach to cell walls. As shown in table 7, trivalent chromium has a higher tendency 549 to be absorbed into the plant than hexavalent form, which may indicate the ability of Salicornia 550 to convert hexavalent chromium to trivalent form in its tissues. In terms of growth, the plant 551 needs to absorb trivalent chromium.  The addition of manure to the soil also resulted in decreased uptake of chromium compared to 561 soil without amendment. By increasing the cation exchange capacity of the soil, manure's 562 application can be effective in reducing the availability of heavy metals in soil and plants. 563 Containing a large amount of humus, manure's addition to the soil can alter the availability of  The results of the present study showed that total phenolic content and photosynthetic pigments 573 significantly decreased as a result of heavy metal toxicity. This decrease was greater in S. 574 perspolitana than in S. persica and probably due to the higher accumulation of the metal in S.   The results of phytoremediation in the present study showed that S. persica and S. perspolitana 606 were able to absorb heavy metals from the soil with higher uptake of metals in the roots than 607 shoots for both species. Considering that the TF index was lower than 1 for all treatments, one 608 can conclude that S. persica and S. perspolitana were not suitable for phytoextraction of metal 609 chromium. Also, the BCF factor for metal chromium was higher than 1, indicating that both S.