不同利用方式下吴江市耕地土壤环境质量变化

土地利用方式的不同影响着土壤环境质量的变化。文章采用了2003年江苏省吴江市耕地质量监测中资料,分析了6种不同土地利用方式下的土壤养分及Pb、Cr、Hg、As、Cd等5种重金属元素全量的变化,并采用土壤质量综合指数(SQI)法计算不同利用下的土壤环境质量指数。结果表明:近20多年来,吴江市土地利用方式发生了明显的变化,这种变化对本土壤养分和重金属含量产生了十分明显的影响。在稻田、林地、桑园、菜地、果园、旱地六种吴江常见的土地利用方式中,稻田土壤环境质量综合指数显著高于其他利用下,而其他五种利用方式下土壤质量的差别不明显。可见稻田不仅是一种太湖地区传统的利用方式,更是保持环境质量相对最佳的土地利用方式。     

Lead content of plants and soils from three abandoned smelter areas in and near Socorro,New Mexico

Two primary lead smelters and one secondary lead smelter have been active in the Socorro, New Mexico (USA) area in the last 110 years: the Billing smelter from 1883 to 1894, the Cuba Road smelter from 1881 to 1900, and Cal West from 1979 to 1984. Samples of plants and surface soil under each plant from all three sites were analysed for lead. The plants consisted of sparse grasses, cacti, creosote bush, snakeweed, mesquite and fourwing saltbush. Lead levels in the plants increased (2-440 g g^–1) as the lead in the alkaline soils (25-10000 ng g^–1) increased. However, the BAC (biological absorption coefficient), which is the ratio of lead content in the plant to the lead content in the soil, a measure of relative accumulation, decreased by one to two orders of magnitude, except for grasses and snakeweed. At background lead levels, there was little difference between lead in rootsversus foliage. At high lead levels, there was higher lead in roots versus foliage at the Billing and Cuba Road sites. The reverse was noted at Cal West. Because this is a recent operation, the higher lead in foliage may be due to foliar uptake. Plant growth at all sites appeared healthy.     

Estimating the area affected by phosphorus runoff in an Everglades wetland: a comparison of universal kriging and Bayesian kriging

Phosphorus-enriched agriculture runoff is believed to be the leading cause of ecosystem changes of Everglades wetlands. To study this effect, it is necessary to estimate the area of the affected region. In this study, Bayesian kriging and universal kriging were used to estimate the area by analysing the data collected by Reddy et al. (1991). The background level of the soil's total phosphorus concentration is usedto determine whether the region is affected by the agriculture runoff, through an indicator function. The area of the affected region was represented by the integration of the indicator function over the entire wetland. The expected value of the affected area was calculated using the results derived from Bayesian and universal kriging. The outcome indicates that universal kriging is sensitive to specification of thecovariance model. It was observed that universal kriging and Bayesian kriging yield comparable results, if the specified covariance structures are of similar nature.     

土壤理化特性对稻田CH4排放的影响

为了研究土壤理化特性对稻田CH4 排放的影响 ,室外盆栽试验于 2 0 0 0年水稻生长季在南京农业大学实施 ,1 8个供试水稻土分别取自江苏宜兴、江宁、六合、仪征及宝应等地 .所有供试土壤的季节性CH4 平均排放通量为 6 42± 2 70mg·(m2 ·h) - 1,最低和最高值分别为 1 96mg·(m2 ·h) - 1和 1 1 0 6mg·(m2 ·h) - 1,两者相差约 5 6倍 .单相关分析结果表明 :影响CH4 排放的主要土壤参数为质地、氮素状况及铜含量 .CH4 排放与土壤砂粒含量呈正相关 (r =0 5 2 8,p =0 0 2 4) ,与粘粒含量呈负相关 (r =-0 484,p =0 0 42 ) .氮素含量高的土壤CH4 排放较低 ,CH4 排放与土壤全氮、速效氮和铵态氮含量的线性相关系数分别为 -0 449(p =0 0 62 )、-0 61 1 (p =0 0 0 7)和 -0 649(p =0 0 0 4) .土壤铜含量直接影响CH4 的排放 ,CH4 排放与有效态铜和全铜含量的线性相关系数分别为 -0 5 94(p =0 0 0 9)和 -0 5 47(p =0 0 1 9) .本研究并未观测到CH4 排放与土壤有机碳含量有相关关系 ,这与前人报道的实验室培养测定结果及稻田CH4 排放随土壤有机质含量提高而增加的假设完全不同 .逐步回归分析表明 ,不同土壤间CH4 排放的变异性有 75 5 %可由土壤有效态铜含量、镁 (全量 )含量及有效铁含量与全量铁之     

Effect of application of ammonium thiosulphate on production and emission of methane in a tropical rice soil

Agricultural sources of atmospheric methane include flooded rice (Oryza sativa L.) paddies. However, certain soil nutrient management and cultural practices offer opportunities to reduce methane emissions. The effect of application of ammonium thiosulphate, a potential source of nitrogen and sulphur and also an inhibitor of nitrification and urease on methane production and emission from flooded alluvial (Typic Haplaquept) rice soil in India, was examined. Methane production and emission from control and urea-amended soil samples were almost identical. Application of ammonium thiosulphate to laboratory-incubated flooded soil (30 and 60 μg N g⁻¹ soil) and flooded rice fields (45.6 and 60 kg N ha⁻¹) effected a distinct inhibition of methane production and emission. Ammonium thiosulphate stimulated the population of sulphate-reducing bacteria (SRB) to a greater extent at 60 μg N g⁻¹ soil than at 30 μg N g⁻¹ soil. In ammonium thiosulphate-applied rice field plots, mean methane efflux decreased by about 38 and 60% at 45.6 and 60 kg N ha⁻¹, respectively, over that of control. Inhibition of methane production by ammonium thiosulphate is, at least in part, due to the stimulation of SRB. Results suggest the mitigation potential of ammonium thiosulphate on methane emission from flooded rice paddies.     

未来气候变化对旱田生态系统N2O释放的潜在影响

反硝化-分解作用模型（DNDC）能较好地拟合贵州省玉米—油菜轮作田、大豆—冬小麦轮作田和休耕地的N2O释放通量及其影响因子季节变化模式，采用DNDC模型定量探讨了未来气温、降雨量和降雨中无机N浓度变化对亚热带旱田生态系统N2O释放的潜在影啊．结果表明，除大亚外，其它作物和休耕地土壤N2O释放通量对气温变化接近于正响应；玉米地、大豆地和体耕地（对应于玉米生长期）土壤N2O释放通量对降雨量的变化也接近于正响应；降雨中无机氮浓度的变化对3块实验田NO2释放通量影响最大．     

Sorption of mercury (II) in Amazon soils from column studies

The sorption of Hg (II) onto four different types of Amazon soils from the A-horizon was investigated by means of column experiments under saturation conditions and controlled metal load. Higher organic matter contents in the soil resulted in higher Hg (II) adsorptions, reaching values as high as 3.8 mg Hg g⁻¹ soil. The amount of mercury adsorbed on a soil column (Q) shows a very poor correlation with soil clay content (r² = 0.2527), indicating that Hg sorption in these topsoil samples is chiefly governed by the organic matter content. Desorption experiments using Negro River (Amazon) waters were conducted using soil saturated with Hg (II) in order to better understand the metal leaching mechanism. The amount of Hg (II) released from soils was around 30% of the total sorbed mercury upon saturation, suggesting that mercury sorption in the soils present in the catchment area of the Negro River basin is not a reversible process.     

Effect of expandable clays and cometabolism on PAH biodegradability

Pyrene and phenanthrene degradation was examined in both single and binary slurry systems for three different natural soils. It was found that the amount of total expandable clays (smectite and vermiculite) was in a good agreement with the achieved rate and extent of biodegradation. For instance, the intrinsic phenanthrene biodegradation rate was 626 microg/L/day for the soil with the largest expandable clay and 3203 microg/L/day for the soil with the least. Similarly, the smallest total pyrene biodegradation (65%) was found for the soil rich in expandable clays, compared to an 82% pyrene reduction in the soil that had the lowest amount. Mass transfer limitation after compound sorption to the clays was more pronounced for the more hydrophobic pyrene. In the presence of phenanthrene, total pyrene biodegradation increased by 2 to 7% due to cometabolism, while the total phenanthrene biodegradation was only enhanced by 0.5 to 5% in the binary system. This research demonstrated that expandable clays might govern the substrate availability to microorganisms and microbial accessibility to substrates. Therefore, the contribution of organic matter and expandable clays to sorption, desorption and biodegradation should be taken equally into account in order to better understand complex bioremediation issues.     

An empirical map of critical loads of acidity for soils in Great Britain

The method used to produce a critical load map of acidity for soils in Great Britain is described. Critical loads were assigned to the dominant soil in each 1 km grid square of the UK national grid. Mineral soils were assigned a critical load based on mineralogy and chemistry, using approaches appropriate to UK conditions. Critical loads for peat soils are based primarily on a maximum acceptable reduction of peat pH, and results from laboratory equilibration studies. The map shows that soils with small critical loads (<0.5 kmol_c ha⁻¹ year⁻¹) i.e. highly sensitive to acidic deposition, dominate in the north and west of Britain; the south and east are dominated by soils with large critical loads, with small areas of more sensitive soils associated with sandy soil-forming materials. A modified critical load map illustrates the potential impact of agricultural liming on soil critical loads.     

pH dependence of copper adsorption in vineyard soils of Geneva

Copper adsorption by vineyard soils of the Geneva canton was evaluated by batch equilibration experiments in a pH range from 4 to 6. The adsorption curves fit significantly to Freundlich function log q = n log C + log K_f, where q is adsorbed Cu concentration on the solid phase and C is solution Cu concentration at the end of the equilibration time. Moreover, we found that Freundlich parameters n and log K_f are moderately correlated to pH, yielding the following equations: log K_f = 0.23 pH + 0.51 (R ² 0.59) and n = –0.12 pH + 1.06 (R ² 0.59). Such equations may be useful to predict Cu mobility for risk assessment studies.