In order to investigate the relationship between some properties of coal-based humic acids and arsenic availability in soil

and potential utilization and application direction of coal-based humic in the remediation and improvement of arsenic contaminated soil

a pot experiment was conducted to study the effects of four coal-based?humic acids on the content and speciation of arsenic in soil

the growth of pakchoi (Brassica campestris L. ssp.)

and the adsorption and distribution of Arsenic in pakchoi. The results showed that No. 6 and No. 10 coal-based humic acids significantly reduced the contents of exchangeable Arsenic and carbonate bound arsenic

thus the content of available arsenic in soil was reduced significantly

meanwhile

the transfer and accumulation of arsenic from underground part to aboveground part of pakchoi were inhibited. The contents of exchangeable arsenic and available arsenic in soil and the total amount of arsenic in aboveground part of pakchoi in No. 10 coal-based humic acid treatment reduced 49.18%

42.22%

and 15.17% than those in arsenic treatment

respectively. However

No. 9 and No. 11 coal-based humic acids increased the contents of exchangeable arsenic and carbonate bound arsenic

and significantly increased available arsenic in soil

and promoted the arsenic absorption

the transfer of arsenic from underground part to aboveground part of pakchoi. The contents of exchangeable arsenic and available arsenic in soil and the total amount of arsenic in aboveground part of pakchoi in No. 9 and No. 11 coal-based humic acids treatments increased 10.58% and 5.95%

31.11% and 22.22%

20.81% and 17.21% than those in arsenic treatment

respectively. The four coal-based humic acids all promoted the growth of pakchoi

and the promotive effect followed the order of No. 10＞No. 6＞No. 11＞No. 9. In conclusion

No. 6 and No. 10 coal-based humic acids

which had lower E4/E6 values

larger molecular weights

and lower contents of total acid base

had obviously inactivate effect on arsenic in soil

and could be used to control the arsenic absorption of crops and inhibit the transfer of arsenic from underground part to aboveground part of crops in mild arsenic polluted soil

so as to ensure crop safety production. No. 9 and No. 11 coal-based humic acids

which had larger E4/E6 values

lower molecular weights

and larger contents of total acid base

promoted arsenic activity and could be used as activator in moderate and severe arsenic polluted soil to strengthen phytoremediation.