Tourmaline and biochar for the remediation of acid soil polluted with heavy metals

Considering the tourmaline as a novel remediation material, the effects of tourmaline on wheat chlorophyll, heavy metal mobility and bioavailability in soil and wheat, and soil enzyme activities were compared to those of biochar which is a widely studied amendment for heavy metals. When 2% dose of 325- and 16,000- mesh of tourmaline and 2% dose of biochar were added in acid soil, wheat weight and chlorophyll most obviously increased by 16,000- mesh tourmaline and biochar, respectively. Cd concentration in wheat shoots was reduced most obviously to 35.6% by 16,000- mesh of tourmaline; Cu concentration in wheat roots was reduced most efficiently to 40.9% by biochar. Additionally, available Cd and Cu in soil added biochar decreased 18.8 and 18.6%, while in soil added tourmaline decreased from 4.95 to 12.9% and from 8.94 to 10.5% with particle size decreasing, respectively. Moreover, tourmaline and biochar both increased soil urease and invertase activities. Biochar made soil urease and invertase activities increased by 187.5 and 67.9%, respectively, while tourmaline made soil urease and invertase activities increased by 137.5% and 37.2%, respectively. Therefore, tourmaline and biochar both amend the acidic soil contaminated with heavy metals. However, biochar amendment is better than tourmaline for the acidic soil.