Agbenin John O
Faculty of Agriculture, Ahmadu Bello University, PMB 1044, Zaria, Nigeria.
Sci Total Environ. 2002 Dec 2;300(1-3):189-99. doi: 10.1016/s0048-9697(02)00231-0.
Growing concern about heavy metal contamination of agricultural lands under long-term application of inorganic fertilizers and organic wastes makes periodic risk assessment of heavy metal accumulation in arable lands imperative. As a part of a much larger study to systematically document the status of heavy metals in savanna soils this study investigated the distribution and dynamics of Cr and Ni in a savanna soil after 50 years of continuous cultivation and application of inorganic fertilizers and organic manures. The cultivated fields were fertilized with inorganic fertilizers (NPK), farmyard manure (FYM), FYM+NPK for 50 years and a control plot under continuous cultivation for 50 years but did not receive either FYM or NPK. Two uncultivated or natural sites were sampled as reference conditions for assessing the dynamics of Cr and Ni induced by cultivation and management practices. The distribution of Cr and Ni in the soil profiles exhibited eluvial-illuvial patterns. Sand and clay fractions explained between 62 and 90% of the variance in Cr and Ni concentration and distribution in the soil profiles. Mean Cr concentrations ranged from 17 to 59 mg kg(-1), while Ni varied from <1 mg kg(-1) in the topsoil to 16 mg kg(-1) in the subsoil. Mass balance calculations showed a loss of 10% Cr and 17% Ni in the FYM field, and approximately 4% Cr and 11% Ni in the NPK field compared to the natural site after 50 years of cultivation. The control and FYM + NPK field had, however, a positive balance of Cr and Ni. In general, it was concluded that existing soil management practices in this region are unlikely to lead to Cr and Ni build-up probably because of low rates of application of inorganic fertilizers, farmyard manure and other organic wastes to the soils.
长期施用无机肥料和有机废弃物导致农田重金属污染问题日益受到关注，因此定期对耕地重金属积累进行风险评估势在必行。作为一项更大规模研究的一部分，该研究旨在系统记录稀树草原土壤中重金属的状况，调查了连续种植50年并施用无机肥料和有机肥料后，稀树草原土壤中铬（Cr）和镍（Ni）的分布及动态变化。耕地分别施用无机肥料（NPK）、农家肥（FYM）、FYM + NPK达50年，还有一块连续耕种50年但未施用FYM或NPK的对照地块。选取两个未开垦或天然场地作为参考条件，以评估种植和管理措施对Cr和Ni动态变化的影响。Cr和Ni在土壤剖面中的分布呈现淋溶淀积模式。砂粒和黏粒部分解释了土壤剖面中Cr和Ni浓度及分布62%至90%的变异。Cr平均浓度范围为17至59 mg kg⁻¹，而Ni浓度从表层土壤中小于1 mg kg⁻¹到下层土壤中16 mg kg⁻¹不等。质量平衡计算表明，与天然场地相比，经过50年耕种后，FYM地块中Cr损失了10%，Ni损失了17%；NPK地块中Cr损失了约4%，Ni损失了11%。然而，对照地块和FYM + NPK地块中Cr和Ni呈现正平衡。总体而言，得出的结论是，该地区现有的土壤管理措施不太可能导致Cr和Ni积累，这可能是因为向土壤中施用无机肥料、农家肥和其他有机废弃物的量较低。
