This is a post-peer-review, pre-copyedit version of the figures of an article published in Environmental geochemistry and health (Ed. Springer). The final authenticated version is available online at: DOI 10.1007/s10653-018-0224-7 4500 CO2flux (mg m-2 h-1) Control a Steel slag 3000 Biochar Steel slag+biochar 1500 a a a ab 0 b b c c bb bb 1 8 15 22 29 36 43 50 57 64 71 78 85 92 CO2 flux (mg m-2 h-1) 4500 b 3000 a a a b ab a a 1500 b ab ab ab a a a b b b a a b ab a b ab a b b b b ab ab b bb 0 b b 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 Days after transplantation Fig. 1 30 CH4 flux (mg m-2 h-1) Control a Steel slag 20 Biochar Steel slag+biochar 10 aa a a ab a 0 bb b b b ab b ab ab b 1 8 15 22 29 36 43 50 57 64 71 78 85 92 CH4 flux (mg m-2 h-1) 60 b 40 a 20 b b b a ab a a b a b ab ba 0 b b b b b b b b ba ab b b 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 Days after transplantation Fig. 2 600 Control N2Oflux (μg m-2 h-1) a Steel slag 400 Biochar Steel slag+biochar 200 a a a a 0 ab b b b 1 8 15 22 29 36 43 50 57 64 71 78 85 92 600 N2O flux (μg m-2 h-1) b 400 a 200 aa a a b 0 bb ab b b b 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 Days after transplantation Fig. 3 12 Control Biochar Steel slag Steel slag+biochar a a a a a a a a a a a 8 b a a a a a Soil pH c b b b b b b c c b c b ab b b b c b c b ab ab ab b d c c c d c d c b c d d d d d b 4 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 12 b a a a a a a a a a a a a Soil pH 8 a a a aa b b b b bc b b ab c b c c c b c b c ab c c cb b c c b c c b ab d d d d d c d d d d d b d d d d 4 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 Days after transplantation 1.5 Soil salinity (mS cm ) a c -1 a a a a a a b a a 1.0 a a a a a a b a a a a ab a ab a a ab b b a a b b b a b c 0.5 b b b c ab ab b c b b bc 0.0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 1.5 Soil salinity (mS cm ) -1 a a a d 1.0 a a a a a a b a a a a a a a a a a a a a a a b b a a b b a a ab a 0.5 c ab a a b b b b b c b b b b b c b 0.0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 40 e Soil temperature (℃) 30 a a ab ab ab ab aa a b b 20 ab bcb b 10 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 40 Soil temperature (℃) f 30 aa a a b b bb aa a ab ab a b b ab a b b c b bb b 20 bb 10 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 150 a Soil water content (%) a g a a a a a a a a 100 a a a a a a a b b a b a b b a b c b b c b b b b b b a c b c b c c b b d b d c b 50 d c d c d b 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 150 Soil water content (%) h a 100 a aa a a a a a a a a a a a bb ab a ab a a aa a aa a a a b b a b b b c c b b b c b b b b c b 50 c c d c b ab b b c d c b d bc b c 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 Days after transplantation Fig. 4 Loading -0.9 -0.6 -0.3 0 0.3 0.6 0.9 (a) 4 0.5 Water content Biochar 2 0.25 Root 2 (10.3%) Control Steel slag + Score Temperature Salinity biochar Loading 0 0 CH emission Steel slag CO2 emission 4 -2 -0.25 N2O emission pH -4 -0.5 -6 -4 -2 0 2 4 6 Score Root 1 (80%) Loading -0.5 -0.25 0 0.25 0.5 (b) 2 0.6 Biochar pH 1 Steel slag + 0.3 Root (18.4%) biochar Loading Control CO2 emission Salinity Score 0 0 N2O emission Temperature CH4 emission -1 Water content -0.3 Steel slag -2 -0.6 -4 -2 0 2 4 Score Root 1 (80.4%) Fig. 5