中文摘要：

对黄土高原古土壤和上海市城市土壤磁性特征进行比较，研究和区分土壤磁性的多元成因。结果表明，黄土高原古土壤磁化率（χlf）平均值为108×10-8 m3 kg-1；频率磁化率（χ fd %）平均值为11.4%，且χlf与χ fd %呈极显著正相关性，表明风化成土作用形成超细顺磁颗粒（SP）是其磁性增强的主要原因。χlf与游离态铁（Fed）、铁游离度（Fed/Fet）和黏粒含量相关性达极显著水平，也说明古土壤磁性增强与风化成土作用有关。上海城市土壤χlf异常增强，变化范围为127～1 959×10-8 m3 kg-1，χ fd %〈2.0%，表明其不含SP，磁性增强并非由于风化成土作用，应与人为污染有关。非滞后剩磁（χarm）、非滞后剩磁/饱和等温剩磁（χarm/SIRM）、非滞后剩磁/磁化率（χarm /χlf）和饱和等温剩磁/磁化率（SIRM/χlf）等参数及组合的研究表明，城市土壤磁性矿物占主导的是多畴（MD）和稳定单畴（SSD）颗粒；而古土壤磁性矿物中占主导的是SP颗粒。软等温剩磁（SOFT）、硬等温剩磁（HIRM）、软磁百分含量（SOFT%）、硬磁百分含量（HARD%）、IRM300 mT/SIRM（F300 mT）等磁性参数的研究表明，城市土壤矫顽力低，软磁组分高，以铁磁性矿物为主导；黄土高原古土壤也以铁磁性矿物为主导，但HARD%通常高于城市土壤。用磁学参数及组合，能较有效分辨土壤磁性的风化成土作用成因或人为污染成因。

英文摘要：

To study multiple origins of magnetic minerals in soils, comparison was made between paeosols in the Loess Plateau, China and urban soils in Shanghai in magnetic properties. Results show the mean values of magnetic susceptibility （χlf） and frequency-dependent magnetic susceptibility （χ fd %） of the paleosols in the Loess Plateau are 108×10-8 m3 kg-1 and 11.4%, respectively; and the two are positively and significantly correlated （p≤0.01）, suggesting that the magnetism enhancement in the soils is mainly attributed to the formation of pedogenic superparamagnetism （SP） grains. Significant positive correlations of χlf with free iron （Fed）, free iron degree （Fed/Fet） and clay content also suggest that the magnetism enhancement in the soils is closely related to pedogenesis. Magnetism of the urban soils in Shanghai is unusually enhanced, with χlf ranging from 127 to 1 959×10-8 m3 kg-1, and χ fd % being mostly 〈2.0%, indicating little SP grains formed, which suggests that the magnetic enhancement of the urban soils is not caused by pedogenesis but by anthropogenic activities. The study of magnetic parameters of their combinations, such as anhysteretic remanent magnetization（χarm）, anhysteretic remanent magnetization/saturated isothermal remanent magnetization （χarm/SIRM）,χarm/χlf and SIRM/χlf, reveals that the urban soils are dominated by multidomain （MD） and stable-single-domain （SSD） grains; while the paleosols in the Loess Plateau by superparamagnetism （SP） grains. The magnetic parameters of soft isothermal remanent magnetization （SOFT）, hard isothermal remanent magnetization （HIRM）, SOFT percentage （SOFT%）, HIRM percentage （HARD%） and IRM300 mT/SIRM （F300 mT） indicate that the urban soils are dominated by ferrimagnetic minerals, with low coercivity and high magnetic soft fraction and the paloesols in the Loess Plateau are also dominated by ferrimagnetic minerals, which are, however, higher in HARD%. The magnetic parameters and their comb