复合改良剂对华南酸化Cd污染稻田修复效果的评估OA

This study aimed to establish a comprehensive evaluation system for assessing the remediation effects of combined amendments on typical acidified Cd-contaminated paddy fields in South China.Using early rice cultivar'Ruanhuayou 6100'and late rice cultivar'Yexiangyou 9'as test materials,a field experiment was conducted with nine combined amendment treatments:Biochar+organic fertilizer(D1),biochar+sepiolite(D2),biochar+bentonite(D3),biochar+alkaline residue(D4),organic fertilizer+sepiolite(D5),organic fertilizer+bentonite(D6),organic fertilizer+alkaline residue(D7),sepiolite+alkaline residue(D8),and bentonite+alkaline residue(D9).A control(CK)with no amendment application was established.The mass ratio of the two amendment materials in each treatment was 1∶1,and the total application rate of amendments was the same for each plot,equivalent to 4 500 kg/hm2.Cd content of rice grain,soil pH,organic matter,alkali-hydrolyzable nitrogen,available phosphorus,available potassium,and available Cd content were measured.The indicators and their weights in the evaluation index system for Cd-contaminated paddy field were adjusted based on the remediation effects aimed at soil quality improvement and rice safe production,and the performance of different combination of amendments was comprehensively assessed along with economic cost analysis.The results showed that:1)The early rice yield under all nine combined amendment treatments was 26.84％-61.72％higher than that of CK(P＜0.05),and the Cd content in early brown rice was 40.23％-67.89％lower than that of CK.The brown rice Cd content in early rice all was lower than the national food safety standard in all treatments.For late rice,brown rice Cd content in 7 treatments(excluding D5 and D8)fell below the national food safety standard.Organic fertilizer-containing treatments(D,and D5-D7)exhibited smaller yield fluctuations,and their early and late rice yields were significantly higher than those of other treatments.Biochar-containing treatments(D1-D4)had low brown rice Cd content in late rice,with a mean value of 0.16 mg/kg,among which D2(biochar+sepiolite)exhibited the best Cd reduction effect.2)All amendment treatments significantly increased soil pH in both seasons.Soil organic matter content in early rice was 1.06％-11.55％higher than that of CK(P＜0.05),and soil available Cd content was in early-season 14.67％-37.04％lower than that in late-season(P＜0.05),while alkali-hydrolyzable nitrogen,available phosphorus,and cation exchange capacity in paddy soil of early-and late-season showed no significant differences compared with CK.Alkaline residue-containing treatments(D4,D7-D9)achieved higher soil pH values than biochar-containing treatments(0.02 higher in early season and 0.03 higher in late season)and organic fertilizer-containing treatments(0.02 higher in early season and 0.03 higher in late season).Biochar-containing treatments(D1-D4)performed better than other treatments in enhancing soil organic matter accumulation and reducing soil available Cd content.The soil organic matter content in early and late rice under biochar-containing treatments was 1.79 and 1.92 g/kg higher than that under alkaline residue-containing treatments,and 0.22 and 0.84 g/kg higher than that under organic fertilizer-containing treatments,respectively.The maximum reduction in soil available Cd content in early rice under biochar-containing treatments reached 32.85％,and it remained 13.46％lower than CK by the end of the late rice season.Comprehensive evaluation showed that,except for D5 and D8,the Cd content in brown rice of early and late rice under the seven combined amendment treatments was below the national food safety standard.Treatments containing organic fertilizer and alkaline residue showed relatively high annual output-to-input ratios.From the perspective of multi-objective synergy and sustained remediation capacity,biochar-containing treatments(D1-D4)achieved higher scores,with D2(biochar+sepiolite)demonstrating the best comprehensive performance in both early and late rice,and demonstrating more sustained remediation effects.In conclusion,under the conditions of this experiment,based on the multi-objective synergistic evaluation of soil environment,agricultural product safety,and cost,the combined application of biochar and sepiolite at a mass ratio of 1∶1(D2)was identified as the optimal combined amendment.