贵州喀斯特地区不同土地利用方式土壤CO_2体积分数变化及影响因素

为了解不同土地利用方式对土壤剖面CO2体积分数的影响,采用气相色谱法对贵州喀斯特地区土壤不同深度空气CO2体积分数进行观测。结果表明：不同土地利用对土壤平均CO2体积分数影响较大,其次序为：次生林（0.35%±0.06%）〉草地（0.34%±0.05%）〉人工林（0.27%±0.03%）〉农田（0.16%±0.03%）。次生林、草地与农田之间土壤CO2体积分数差异性显著,而人工林与农田之间无显著性差异。不同土地利用方式土壤剖面CO2体积分数的时空变化特征比较一致：从春季到夏季逐渐增加而从秋季到冬季又逐渐降低,与该区域的温度和降雨量变化趋势一致。同时随着土壤剖面深度增加CO2体积分数逐渐增大,但在土层12 cm处有突然降低现象（农田除外）。不同土地利用方式土壤空气CO2体积分数变化与大气、土壤温度密切相关（r=0.602~0.886,P〈0.05）,土壤温度升高会导致土壤CO2体积分数上升。土壤湿度虽然也在一定程度上影响了剖面CO2体积分数,但相关性分析表明二者之间并不显著（r=0.105~0.393,P〉0.05）,说明在贵州喀斯特地区,土壤温度对土壤空气CO2体积分数的影响大于土壤湿度。     

硅肥等量施用对土壤镉生物有效性和水稻吸收镉的影响

为研究硅（Si）肥等量施用对水稻不同生育期吸收镉（Cd）和土壤Cd生物有效性的影响,采用5种不同种类的Si肥（SiO₂用量为225 kg ·hm^-2）开展田间小区试验.结果表明,随着水稻生育期的延长,水稻根系和茎叶的Cd含量增加;施用Si肥,不同生育期水稻根系、茎叶和籽粒Cd含量平均分别降低14.9%、28.2%和12.2%;硅钙镁铁肥（SiCaMgFe）和水溶Si肥（SiW）处理,籽粒Cd含量分别比对照处理降低21.1%（P<0.05）和21.2%（P<0.05）;水稻根表铁膜中Cd含量（DCB-Cd）随着水稻生育期延长而增加,施用Si肥,水稻不同生育期DCB-Cd含量有高有低,DCB-Cd是根系Cd含量的15.8%~42.8%;与对照相比,施用Si肥水稻成熟期土壤可交换态Cd （Exc-Cd）含量平均降低36.4%,其它形态的含量平均增加12.5%~48.2%.水稻全生育期根系Cd与Si呈极显著负相关,与DCB-Cd呈极显著正相关,DCB-Cd与土壤有效态Cd和有效态Si呈极显著负相关,土壤Exc-Cd与Carb-Cd呈极显著负相关,土壤有效态Cd与pH值呈显著负相关.施用相同Si肥用量,SiCaMgFe和SiW处理降低水稻Cd含量的效果好;施用Si肥通过提高土壤pH值和土壤有效Si含量、降低土壤有效态Cd和Exc-Cd含量,促进Exc-Cd向Carb-Cd转移,减少根表铁膜对Cd的吸附,从而减少水稻对土壤Cd的吸收.     

基于物种敏感度分布的不同岩溶地下河中多环芳烃分布特征及生态风险评价

为明确重庆青木关和老龙洞地下河流域地下水中多环芳烃(PAHs)的含量及其污染水平,全年共采集两流域地下河水样品84个,利用气相色谱质谱联用系统(GC-MS)分别测定了地下水中的16种PAHs含量,分析了PAHs在两条地下河流域中的空间分布特征,并应用物种敏感度分布法(species sensitivity distribution, SSD)评价了单体PAH生态风险和联合生态风险,分别应用浓度加和模型和效应加和模型计算了两条地下河流域水中单体PAH潜在影响比例(potential affected fractions, PAFs)及∑PAHs潜在累积影响比例(msPAF)。结果表明,青木关地下河水中∑PAHs浓度为73.8~480 ng/L,均值为224 ng/L,老龙洞地下河中∑PAHs浓度变化较大,为81.5~15 200 ng/L,均值为1 648 ng/L。应用效应加和模型计算出青木关地下河中∑PAH₈的msPAF_RA范围为0.145 9%~2.745 3%,均值为1.369 2%;老龙洞流域msPAF_RA范围为1.001 1%~2.866 5%,均值为1.774 7%,整体高于青木关地下河流域。单体PAH的PAFs在两条地下河流域均呈现Bap>Ant>Pyr>Fla>Flu>Ace>Phe>Nap的趋势,并且小于5%。两条地下河流域水体PAHs含量及生态风险均呈现入口大于出口的趋势,且生态风险的分布特征表明青木关和老龙洞地下河流域水生生态风险主要受BaP的影响,所以应避免工业及生活污水直接排入地下河以及直接饮食地下河水和生物。     

树叶烟尘中的有机碳和元素碳

为了探讨不同燃烧条件下树叶烟尘中有机碳(OC)、元素碳(EC)及8种碳组分(OC1~OC4、POC、EC1~EC3)的质量分数及分布,利用自制的燃烧采样装置,对10种绿叶进行了阴、明燃两种条件的燃烧,并用热/光碳分析仪对产生的烟尘进行了测定.结果表明,10种绿叶阴燃烟尘中的OC、EC质量分数均值分别为48.9%和4.5%,焦炭char-EC(定义为EC1-POC)的质量分数均值为4.4%.该条件下绿叶燃烧的烟尘(PM)、OC及EC的排放因子均值分别为102.4、50.0和4.7 g·kg-1,烟尘中OC/EC、OC1/OC2及焦炭和炭灰的比值char-EC/soot-EC(定义为EC1-POC/EC2+EC3)的均值分别为11.5、1.9和48.1.明燃条件下,10种绿叶烟尘中OC、EC及char-EC的质量分数均值分别为44.9%、10.9%和10.7%,PM、OC及EC的排放因子均值分别为59.2、26.6和6.0 g·kg-1.10种绿叶明燃烟尘中上述三特征比值的均值分别为4.8、1.1和133.0.树叶阴燃烟尘中OC1质量分数及OC1/OC2值均显著高于明燃,而明燃烟尘中的char-EC质量分数及char-EC/soot-EC显著大于阴燃.树叶烟尘中OC、EC的组成在不同树种及燃烧条件间均体现出一些差异,同时也明显区别于其他生物质烟尘.     

生物质炭对Cd污染土壤团聚体酶活性的影响

为探究生物质炭对Cd污染土壤团聚体酶活性的影响,采用盆栽试验,向模拟Cd污染土壤中添加生物质炭并测定水稻根际土壤团聚体碳循环酶与氧化还原酶活性.结果表明:Cd污染土壤团聚体酶活性对添加量为2.5％的生物质炭响应明显,氧化还原酶活性指数值介于0.522～0.792之间.在2.5mg/kg的外源Cd条件下,2.5％的生物质...     

Variation in some chemical parameters and organic matter in soils regenerated by the addition of municipal solid waste

The organic fraction of a municipal solid waste was added in different doses to an eroded soil formed of loam and with no vegetal cover. After three years, the changes in macronutrient content and the chemical-structural composition of its organic matter were studied. The addition of the organic fraction from a municipal solid waste had a positive effect on soil regeneration, the treated soils being covered with spontaneous vegetation from 1 yr onwards. An increase in electrical conductivity and a fall in pH were noted in the treated soils as were increases in macronutrients, particularly N and available P and the different carbon fractions. Optical density measurements of the organic matter extracted with sodium pyrophosphate showed that the treated soils contained an organic matter with less condensed compounds and with a greater tendency to evolve than the control. A pyrolysis-gas chromatography study of the organic matter extracted with pyrophosphate showed large quantities of benzene both in the treated soils and control; pyrrole was also relatively abundant, although this fragment decreased as the dose rose. Xylenes and pyridine were present in greater quantities in the control and furfural in the treated soils. Three years after addition to the soil, the organic matter had a higher proportion of fragments derived from aromatic compounds and a smaller proportion derived from hydrocarbons. Similarity indices showed that, although the added and newly formed organic matter 3 yr after addition continued to differ from that of the original soil and to be more mineralizable, the transformations it has undergone made it more similar to the original organic matter of the soil than it was at the moment of being added.     

Assessment of labile phosphorus fractions and adsorption characteristics in relation to soil properties of West African savanna soils

A large proportion of total P in the soils of the area is unavailable to plants and consequently P is the second most limiting nutrient. The labile and moderately labile phosphorus fractions and adsorption characteristics of surface and subsurface horizons of eleven soil profiles in the derived savanna (DS) and the northern Guinea savanna (NGS) of West Africa were assessed. The labile P fractions are the resin and HCO₃-extractable inorganic (Pi) and organic (Po) P. The moderately labile fractions are the NaOH-extractable portion of soil P in the Hedley sequential procedure. In the DS soils, the resin P, considered the most readily available fraction, varied from 1 to 14 mg kg⁻¹, HCO₃-Pi ranged from 3.3 to 11, and HCO₃-PO was between 4 and 12 mg kg⁻¹ in the surface horizon. In the NGS, the topsoil contained 1.5–3 mg kg⁻¹ of resin P, 5–8 mg kg⁻¹ of HCO₃-Pi, and 7.5–9.7 mg kg⁻¹ of HCO₃-Po. Sodium hydroxide-Po was the largest of the fractions in all the soils studied. It ranged from 23 to 55 mg kg⁻¹ in the topsoil. In general, the labile P levels were higher in soils of the DS than of the NGS and were related to the oxalate-extractable Fe (Fe_ox), and Al (Al_ox) as well as to soil texture. The subsoil of Kasuwan Magani (profile KS 9–21 cm) required 153 mg P kg⁻¹ to maintain 0.2 mg P l⁻¹ in solution (standard P requirement), and Danayamaka (profile DD 7–32 cm) required 145 mg P kg⁻¹. These could translate to 214 and 200 kg P ha⁻¹ if a plow layer of 10 cm is assumed. Because these are within the plow layer, more P fertilizer would be needed for crop production than in the other soils. The standard P requirement and the adsorption maxima were related to Fe_ox and Al_ox, dithionite-Fe (Fe_d), and texture. The increase in labile P content with decreasing Fe_ox and Al_ox could imply that management practices capable of reducing the activities of Fe and Al in solution might improve P availability.     

太湖地区水稻土颗粒中重金属元素的分布及其对环境变化的响应

采用原状土样分离技术，研究了太湖地区几种主要水稻土示同颗粒中重金属元素Pb、Cr、Cd的分布，结果表明这些元素在不同粒径的土壤颗粒中分配迥异，重金属含量在＞0．25mm的粗颗粒和＜0．002mm的细颗粒中较高，且与土壤有机碳有密切的关系；重金属元素主要积累于＞0．25mm的粗颗粒中，Cd的粗颗粒积累比Pb、Cr更强烈，耕层土壤重金属的颗粒分配因土壤种类不同而异，并响应于土壤环境变化，提出以分馏系数表示重金属在土壤颗粒的分配特点。     

Characterization of dissolved organic matter from saline soils by fluorescence spectroscopy

In this paper hydrophilic (HI) and hydrophobic (HO) fractions of dissolved organic matter (DOM) extracted from soils at different degrees of salinisation were characterised by means of fluorescence spectroscopy in the emission, excitation and synchronous-scan modes. Results provided evidence of the different chemical nature of DOM fractions and allowed to distinguish hydrophilic and hydrophobic fractions extracted from the same soil substrate. The strong decrease in fluorescence intensity observed with the increasing salinity of the soils can be utilised to obtain information on the salinity level of different soil substrates by comparison of spectral fluorescence intensities.     

海陆交互带土壤及河流沉积物中镉含量及形态分布特征

镉污染对人类健康构成威胁,研究土壤中镉的空间分布可以用来评估对人类和环境构成的风险.通过分析海陆交互带不同埋深土壤中的重金属镉（Cd）含量及形态,揭示了土壤重金属镉的富集特征及变化规律.结果表明：1广州南沙区地表水中Cd质量浓度均低于0.0001 mg ·L^-1,河流沉积物的理化性质以上横沥水道为界呈现空间差异,重金属Cd主要沉积在上横沥以北,总Cd均值为2.71mg ·kg^-1,上横沥水道及以南河流沉积物总Cd为0.062~0.39mg ·kg^-1,对海洋环境危害小;②土壤剖面Cd含量随土壤埋深增加逐渐减小,埋深0~20、20~50、50~90、90~140和140~200cm等5层剖面Cd含量中值依次为0.51、0.50、0.45、0.42和0.33mg ·kg^-1,且离散程度随埋深增加逐渐减小,pH小于5的土壤中Cd在垂向上的迁移量及迁移深度显著增加;③土壤中残渣态Cd约占40%,随埋深变化趋势基本持平,弱酸提取态Cd占比中值与pH的变化一致,均随剖面埋深的增加而增大;可还原态Cd占比中值与铁、锰含量的变化一致,随剖面埋深的增加而减小.这些结果对城市周边农田土壤Cd污染的区域防治、污染土壤治理修复具有重要的指导意义.