Effects Of Mining-produced Humates Quality And Application On Restoration Of Mined Land In North Florida

The rate of consumption of mineral resources is continuously increasing with the advancement of science and technology, economic development, industrial expansion, acceleration of urbanization and growth of population. Compared to normal soils, the productivity of mining land significantly lost because various mining techniques produce an assortment of reclaimed sitesand the surface soil piles after they are removed from mined land. In order to increase the productivity of mining land, using humate is one of the most important methods. However, the current research mainly focuses on the effect of humate which usually is produced by special methods on productivity of land.Generally, humate from mining land is produced by different flocculants. Various of studies have revealed that soil properties and texture varied from humates produced by different flocculants. So the reclaiming efficiency is closely related to the source of humate, characterization and extracted methods. The effect on restoration via humates produced by different flocculants need to be explored and validated by experiment. The thesis has taken4humate samples produced by4flocculants from a titanium mining industry in North Florida as research objects, conducted pitch experiments, toxicity tests and greenhouse study. Based on the analysis the effects of leaching and liming on reducing the humates toxicity and changing their chemical properties are evaluated.On one hand, the research provided an evidence in order to select optimical flocculant that was used for producing humate which would have less toxicity to restoration. On the other hand, the results had important theoretical meaning and potential application value for mining land waste and would provide a new way for mining land restoration. The main conclusion of the thesis include:(1)The pitch experiments on mining-produced humate properties indicated that humate organic matter, bulk density and humification presented the characterization of spodic horizon that is high organic matter (～55%) and humification (E4/E61.53～1.84), low bulk density (<0.70). Other properties, such as pH, total elemental content, available nutrient content, and monomeric A1content varied with the type of flocculants used. AP presented low pH and low monomeric A1content (pH3.6and301.7mg kg-1), and PM showed the highest available Ca and Mg content (985.5and199.2mg kg-1).(2)In the toxicity tests, mining-produced humate is potential toxic to plant and the toxicity varied with flocculants. Compared to CH, PM presented low toxicity (RE>0.75), AH presented high toxicity (RE<0.25), and AP and FH presented moderate toxicity (0.25<RE<0.75). Regression analysis shown that the humate pH and monomeric A1content are the major humate properties that have strong relationship with humate toxicity. The pH has a significant positive correlation with toxicity (R2=0.9567,p<0.05), and the relationship between root length and monomeric A1content was a significant negative correlation with toxicity (R2=0.7728, p<0.05).(3)This study about effects of leaching and lime on mining-produced humate chemical properties and toxicity indicated that both methods can significantly rise pH and reduce monomeric A1content. The two factors affected should be responsibility for reducing mining-produced humate toxicity. Also, leaching and liming increased exchangeable Ca2+concentration in humates, which might be another reason that led to reducing toxicity. Both low (1%) and high (4%) lime ratios can significantly increase available nutrients content of huamtes (except for K, Cu and Mn). Meanwhile, they not only can reduce humate toxicity to non-toxicity, but also stimulate lettuce growth (except for AH treated by1%lime ratio). Compared to liming, since leaching reduces available nutrients, it will increase the potential risk of nutrient deficiencies, which to some extension might limit plant growth.(4)In the greenhouse study on simulating mining land field, tailing was non-toxicity but topsoil presented slightly toxic to lettuce. However, no significant difference in loblolly pine growth was seen between control, PM treatment and FH treatment in two mixing ratios. The result suggests that the toxicity occurred in lettuce didn’t show in loblolly pine. Therefore, PM and FH can be applied to the restoration of mined land in North Florida and considering the effective practice, high mixing ratio is most cost-effective.