Introduction
Materials and methods
Preparing soil samples and amendments
Characterization of soil and amendments
Pot experiment
Leachate sampling
Phytoavailability
Statistical analyses
Results and discussion
Physical and chemical properties of original soil and amendments
Name of samples | pH | Cd (mg/kg) | Cu (mg/kg) | Pb (mg/kg) | Zn (mg/kg) | T-P (mg/kg) | T-N (%) | OM (%) | K (mg/kg) | CEC (meq/100 g) | SSA (m2/g) | Texture |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Original soil | 6.69 | 1.00 | 55 | 74.4 | 291 | 607 | 0.04 | 0.59 | ND | 7.60 | ND | Loamy sand |
RHB | 7.86 | 0.09 | 18 | 0.50 | 48 | 48,714 | 3.30 | 48.76 | 2701 | 20.00 | 7.36 | ND |
MLB | 8.89 | 0.39 | 5 | 0.50 | 38 | 1379 | 0.54 | 21.00 | 2520 | 22.00 | 12.20 | ND |
RM | 10.73 | ND | 15 | 48.00 | 131 | 280 | 0.01 | 0.50 | 48 | 45.24 | 44.13 | ND |
SS | 11.83 | ND | 18 | 18.00 | 442 | 4983 | 0.01 | 0.89 | 169 | 25.22 | 17.86 | ND |
XRF, XRD, and SEM analysis results
Effect of treatments on pH
Soil pH under different treatments | RHB (%) | MLB (%) | RM (%) | SS (%) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
0.5 | 1 | 2 | 0.5 | 1 | 2 | 0.5 | 1 | 2 | 0.5 | 1 | 2 | |
Control (%) | ||||||||||||
0 | 0.6*** | 0.5*** | 0.5*** | 0.7*** | 0.5*** | 0.3*** | 0.3*** | 0.3*** | 0.1*** | 0.5*** | 0.6*** | 0.5*** |
RHB (%) | ||||||||||||
0.5 | 1 | 0.8*** | 0.8*** | 0.4** | 0.4** | 0.2*** | *** | 0.1*** | *** | 0.2** | 0.2*** | 0.2*** |
1 | 1 | 0.9*** | 0.4*** | 0.2*** | 0.2 | *** | – | *** | 0.1*** | 0.1* | 0.1* | |
2 | 1 | 0.4*** | 0.2*** | 0.2 | *** | – | *** | 0.1*** | 0.1** | – | ||
MLB (%) | ||||||||||||
0.5 | 1 | 0.5*** | 0.4*** | 0.1*** | 0.2*** | 0.1*** | 0.3*** | 0.4*** | 0.3*** | |||
1 | 1 | 0.8*** | 0.2* | 0.2*** | 0.3*** | 0.3 | 0.3*** | 0.3*** | ||||
2 | 1 | *** | – | 0.2*** | 0.1*** | 0.2** | – | |||||
RM (%) | ||||||||||||
0.5 | 1 | 0.6*** | 0.3*** | 0.3*** | 0.4 | 0.3*** | ||||||
1 | 1 | 0.2*** | 0.6*** | 0.3*** | 0.6* | |||||||
2 | 1 | 0.20*** | 0.3*** | 0.3*** | ||||||||
SS (%) | ||||||||||||
0.5 | 1 | 0.8*** | 0.8*** | |||||||||
1 | 1 | 0.8*** | ||||||||||
2 | 1 |
Critical load of heavy metals (%) under different treatments | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Heavy metals at different parts | Control | RHB 1 | RHB 2 | RHB 3 | MLB 1 | MLB 2 | MLB 3 | RM 1 | RM 2 | RM 3 | SS 1 | SS 2 | SS 3 |
Soil | |||||||||||||
Cd | 20 | 56 | 63 | 71 | 48 | 63 | 72 | 53 | 59 | 71 | 41 | 46 | 56 |
Cu | 65 | 69 | 72 | 74 | 72 | 73 | 76 | 69 | 72 | 75 | 64 | 67 | 69 |
Pb | 77 | 94 | 95 | 96 | 94 | 95 | 97 | 94 | 95 | 96 | 95 | 96 | 97 |
Zn | 66 | 76 | 79 | 81 | 76 | 77 | 81 | 76 | 77 | 79 | 69 | 71 | 71 |
Arial part of plant | |||||||||||||
Cd | 80 | 44 | 37 | 29 | 52 | 37 | 28 | 47 | 41 | 56 | 59 | 54 | 45 |
Cu | 12 | 11 | 11 | 9 | 10 | 9 | 8 | 11 | 10 | 9 | 9 | 9 | 7 |
Pb | 15 | 2 | 2 | 1 | 2 | 1 | 1 | 2 | 2 | 1 | 1 | 1 | 1 |
Zn | 15 | 11 | 9 | 8 | 11 | 11 | 9 | 23 | 24 | 31 | 17 | 16 | 19 |
Roots | |||||||||||||
Cd | – | – | – | – | – | – | – | – | – | – | – | – | – |
Cu | 23 | 20 | 17 | 17 | 18 | 18 | 16 | 20 | 18 | 16 | 27 | 24 | 24 |
Pb | 8 | 4 | 3 | 3 | 4 | 4 | 2 | 5 | 3 | 3 | 4 | 3 | 2 |
Zn | 19 | 13 | 12 | 11 | 13 | 12 | 10 | 14 | 13 | 12 | 14 | 13 | 10 |
Leachate | |||||||||||||
Cd | 0.20 | 0.03 | 0.02 | 0 | 0.05 | 0.01 | 0 | 0.10 | 0.06 | 0.01 | 0.04 | 0.02 | 0.00 |
Cu | 0.03 | 0.01 | 0.00 | 0.03 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.004 | 0.01 | 0.01 | 0.002 |
Pb | 0.10 | 0.03 | 0.02 | 0.02 | 0.04 | 0.03 | 0.01 | 0.02 | 0.02 | 0.01 | 0.01 | 0.01 | 0.00 |
Zn | 0.05 | 0.01 | 0.01 | 0.00 | 0.01 | 0.01 | 0.01 | 0.01 | 0.005 | 0.004 | 0.01 | 0.01 | 0.01 |
Effect of various treatments on metal leaching
Phytoavailability of metals
Simple steady-state mass balance model and related input data
Chemical speciation of metals
Comparison of effectiveness of different treatments
Treatments | Leaching | Phytoavailability | ||||||
---|---|---|---|---|---|---|---|---|
Cd | Cu | Pb | Zn | Cd | Cu | Pb | Zn | |
RHB (%) | ||||||||
0.5 | x | o | x | x | o | x | x | x |
1 | x | o | x | o | o | x | o | x |
2 | o | x | o | x | o | o | o | o |
MLB (%) | ||||||||
0.5 | x | x | o | x | x | x | x | x |
1 | x | o | o | x | o | o | x | x |
2 | o | x | o | x | o | o | o | o |
RM (%) | ||||||||
0.5 | o | o | o | x | o | x | x | o |
1 | o | o | o | o | o | x | x | o |
2 | x | x | o | x | o | o | x | o |
SS (%) | ||||||||
0.5 | x | o | o | o | o | x | o | x |
1 | o | o | o | o | x | o | o | x |
2 | x | x | o | x | o | o | o | o |