Changes in soil fertility parameters and the environmental effects in a rapidly developing region of China

An extensive knowledge of the temporal variability of soil fertility parameters and how this variation affects the environment is imperative to a wide range of disciplines within agricultural science for optimal crop production and ecosystem preservation. This paper examines the temporal variability of soil pH, organic matter (OM), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), available phosphorus (P_Av), and available potassium (K_Av) on Cambosols (Entisols) (n = 179) and Anthrosols (Inceptisols) (n = 95) in Zhangjiagang County, China from 1980 to 2004. Nutrient input was monitored from 1983 to 2004. Annual N fertilizer rates were significantly different during three periods (1983–1989, 1989–1999, 1999–2004), where annual rates increased significantly after 1989 and then decreased after 1999. Annual P fertilizer rates were significantly different during two periods (1983–1993, 1993–2004) where annual rates increased after 1993. No change was found in K fertilizer rates. Soil pH marginally increased by 0.14 units in Cambosols, but significantly decreased by 1.02 units in Anthrosols. OM, CEC, and TN increased in both soil orders an average of 2.15 g kg^?1, 1.6 cmol kg^?1, and 0.21 g kg^?1, respectively. TP decreased in Anthrosols by 70 mg kg^?1, P_Av increased in Cambosols by 4.83 mg kg^?1, and K_Av decreased in Cambosols by 15 mg kg^?1. Fertilizer input rates are causing nutrient imbalances, contributing to acidification in Anthrosols, and decreasing C/N ratios. Nutrient loading of N and deficiency of K is also a potential problem in the area. Efforts should be made to readjust soil nutrient inputs to reach an optimal, sustainable level.     

Uncertainty assessment of mapping mercury contaminated soils of a rapidly industrializing city in the Yangtze River Delta of China using sequential indicator co-simulation

Accurate characterization of heavy-metal contaminated areas and quantification of the uncertainties inherent in spatial prediction are crucial for risk assessment, soil remediation, and effective management recommendations. Topsoil samples (0–15 cm) (n = 547) were collected from the Zhangjiagang suburbs of China. The sequential indicator co-simulation (SIcS) method was applied for incorporating the soft data derived from soil organic matter (SOM) to simulate Hg concentrations, map Hg contaminated areas, and evaluate the associated uncertainties. High variability of Hg concentrations was observed in the study area. Total Hg concentrations varied from 0.004 to 1.510 mg kg⁻¹ and the coefficient of variation (CV) accounts for 70%. Distribution patterns of Hg were identified as higher Hg concentrations occurred mainly at the southern part of the study area and relatively lower concentrations were found in north. The Hg contaminated areas, identified using the Chinese Environmental Quality Standard for Soils critical values through SIcS, were limited and distributed in the south where the SOM concentration is high, soil pH is low, and paddy soils are the dominant soil types. The spatial correlations between Hg and SOM can be preserved by co-simulation and the realizations generated by SIcS represent the possible spatial patterns of Hg concentrations without a smoothing effect. Once the Hg concentration critical limit is given, SIcS can be used to map Hg contaminated areas and quantitatively assess the uncertainties inherent in the spatial prediction by setting a given critical probability and calculating the joint probability of the obtained areas.     

氧化与还原条件下水稻土重金属形态特征的对比

还原状态下的水稻土被风干处理后氧化还原等性质发生明显变化,对重金属的形态特征产生影响,进而影响对作物有效性的评价.利用BCR连续萃取法研究了张家港市南部不同pH水稻土在还原和氧化条件下Cu、Pb、Ni和Cd的形态变化状况.结果显示,氧化还原对重金属形态分配具有显著影响,而pH对Ni在还原状态下的形态分配有显著影响,对Cu、Pb和Cd形态分布影响不显著.样品经风干氧化处理后,氧化物结合态重金属均表现为不同程度的降低;Cu残渣态比例增加25%,氧化物结合态和有机结合态比例有所降低;Pb有机结合态比例增加33%,残渣态减少33%,酸可提取态和氧化物结合态变化不大;Ni受氧化还原条件影响更为强烈,表现为酸可提取态所占比例降低超过25%,氧化物结合态亦明显降低,残渣态提高超过60%;对Cd的影响主要表现为有机结合态所占比例降低约15%,残渣态提高约35%,酸可提取态和氧化物结合态变化不明显.氧化状态下的重金属形态并不是重金属在田间的真实状况,可能高估了Pb,低估Cu、Ni和Cd重金属在土壤中的危害性.