作为一种有限的自然资源，磷（P）逐渐成为影响全球可持续发展的新挑战。中国农业对全球可持续磷管理意义重大。在中国集约化的农业生产中，通过根际和土壤磷管理来提高磷的利用效率和作物生产力是很有必要的。之前的研究表明，利用LePA模型（legacy phosphorus assessment model）基于土壤磷管理（恒量监控方法）预测中国未来的磷肥需求量会大大降低。本研究利用LePA模型基于根际和土壤磷综合管理预测了在四种减磷情景下我国各县未来的磷肥需求量。四种情景设置分别为：（1）模拟期间磷肥投入量与2012年相同；（2）低磷县先保持2012年的施磷水平，而高磷县先停施磷肥，直至土壤Olsen-P达目标值，然后施磷量均与作物磷带走量相同；（3）低磷县的土壤Olsen-P达目标值后，各县的施磷量每年降低1 – 7 kg ha^-1，然后每年增加0.1 – 9 kg ha^-1至作物磷带走量；（4）低磷县的磷投入量与2012年相同直至土壤Olsen-P含量升高到目标值，而高磷县的磷投入量先每年降低1 – 7 kg ha^-1，再每年增加0.1 – 9 kg ha^-1，然后与作物磷带走量相同。结果表明，情景4分析的我国在2013 – 2080年期间的磷肥需求总量为6.93亿吨，与农民传统施磷量相比降低了57.5%。与基于土壤管理的磷需求量相比，模拟期间我国磷肥总需求量可进一步降低8.0%。我国平均的土壤Olsen-P含量只需维持在17.2 mg kg^-1即可满足作物高产的需求。我们的研究结果为政府出台可持续磷管理的相关政策提供了坚实的基础。

The adsorption of Cu(II) from aqueous solution onto humic acid (HA) which was isolated from cattle manure (CHA), peat (PHA), and leaf litter (LHA) as a function of contact time, pH, ion strength, and initial concentration was studied using the batch method. X-ray absorption spectroscopy (XAS) was used to examine the coordination environment of the Cu(II) adsorbed by HA at a molecular level. Moreover, the chemical compositions of the isolated HA were characterized by elemental analysis and solid-state 13C nuclear magnetic resonance spectroscopy (NMR). The kinetic data showed that the adsorption equilibrium can be achieved within 8 h. The adsorption kinetics followed the pseudo-second-order equation. The adsorption isotherms could be well fitted by the Langmuir model, and the maximum adsorption capacities of Cu(II) on CHA, PHA, and LHA were 229.4, 210.4, and 197.7 mg g–1, respectively. The adsorption of Cu(II) on HA increased with the increase in pH from 2 to 7, and maintained a high level at pH>7. The adsorption of Cu(II) was also strongly influenced by the low ionic strength of 0.01 to 0.2 mol L–1 NaNO3, but was weakly influenced by high ionic strength of 0.4 to 1 mol L–1 NaNO3. The Cu(II) adsorption on HA may be mainly attributed to ion exchange and surface complexation. XAS results revealed that the binding site and oxidation state of Cu adsorbed on HA surface did not change at the initial Cu(II) concentrations of 15 to 40 mg L–1. For all the Cu(II) adsorption samples, each Cu atom was surrounded by 4 O/N atoms at a bond distance of 1.95 Å in the first coordination shell. The presence of the higher Cu coordination shells proved that Cu(II) was adsorbed via an inner-sphere covalent bond onto the HA surface. Among the three HA samples, the adsorption capacity and affinity of CHA for Cu(II) was the greatest, followed by that of PHA and LHA. All the three HA samples exhibited similar types of elemental and functional groups, but different contents of elemental and functional groups. CHA contained larger proportions of methoxyl C, phenolic C and carbonyl C, and smaller proportions of alkyl C and carbohydrate C than PHA and LHA. The structural differences of the three HA samples are responsible for their distinct adsorption capacity and affinity toward Cu(II). These results are important to achieve better understanding of the behavior of Cu(II) in soil and water bodies in the presence of organic materials.