砂质土壤不同粒径颗粒中有机碳、养分和重金属状况

用分散、筛分和悬浮相结合的物理方法，研究了砂质土壤中养分和重金属在不同粒径有机、无机颗粒中的分布。研究表明，砂质土壤中Cd、Co、Cr、Cu、Ni、Pb、Zn和Mn在颗粒状有机质（POM）有明显的富集，富集程度以Cu和Zn最为明显。粒径较小（0．05～1mm）的POM组分中重金属的平均富集高于粒径较大（〉1mm）的POM组分。POM中重金属的富集因土壤重金属污染水平和重金属类型而异，并与土壤重金属的积累呈正相关。分析数据表明，土壤POM中重金属的积累不完全是植物分解残留的结果，土壤POM对重金属有强吸持能力可能是POM中重金属富集的主要原因之一。     

砂质土壤不同粒径颗粒中有机碳、养分和重金属状况

用分散、筛分和悬浮相结合的物理方法,研究了砂质土壤中养分和重金属在不同粒径有机、无机颗粒中的分布。研究表明,砂质土壤中Cd、Co、Cr、Cu、Ni、Pb、Zn和Mn在颗粒状有机质(POM)有明显的富集,富集程度以Cu和Zn最为明显。粒径较小(0.05~1 mm)的POM组分中重金属的平均富集高于粒径较大(>1 mm)的POM组分。POM中重金属的富集因土壤重金属污染水平和重金属类型而异,并与土壤重金属的积累呈正相关。分析数据表明,土壤POM中重金属的积累不完全是植物分解残留的结果,土壤POM对重金属有强吸持能力可能是POM中重金属富集的主要原因之一。     

Bacterial community structure in soil microaggregates and on particulate organic matter fractions located outside or inside soil macroaggregates

Soil aggregates and particulate organic matter (POM) are thought to represent distinct soil microhabitats for microbial communities. This study investigated whether organo-mineral (0–20, 20–50 and 50–200 μm) and POM (two sizes: >200 and <200 μm) soil fractions represent distinct microbial habitats. Microbial habitats were characterised by the amount and quality of organic matter, the genetic structure of the bacterial community, and their location outside or inside macroaggregates (>200 μm). The denaturing gradient gel electrophoresis (DGGE) profiles revealed that bacterial communities structure of organo-mineral soil fractions were significantly different in comparison to the unfractionated soil. Conversely, there were little differences in C concentrations, C:N ratios and no differences in DGGE profiles between organo-mineral fractions. Bacterial communities between soil fractions located inside or outside macroaggregates were not significantly different. However, the bacterial communities on POM fractions were significantly different in comparison to organo-mineral soil fractions and unfractionated soil, and also between the 2 sizes of POM. Thus in the studied soil, only POM fractions represented distinct microhabitats for bacterial community, which likely vary with the state of decomposition of the POM.     

不同季节海鞘滤水率的测定

在桑沟湾用模拟现场流水法对滤食性附着生物玻璃海鞘和柄海鞘的滤水率进行了测定。结果表明，同一品种海鞘，在不同季节其滤水率随着水温的变化而变化。在实验水温范围内，以５月份水温在１７℃左右时海鞘滤水率最大，栖海鞘为３．１９ｌ／ｈ·ｉｎｄ（ｃｈｌ－ａ）和４．５３１／ｈ·ｉｎｄ（ＰＯＭ），玻璃海鞘为０．７３１／ｈ·ｉｎｄ（ｃｈｌ－ａ）和０．７６１／ｈ·ｉｎｄ（ＰＯＭ）．１１月和９月水温在７℃和２５℃左右时其滤水率均降低至１７℃时的１／３～１／５左右。由此反映出这两种海鞘的生理现象和生活规律及与环境因子的关系。     

连续5年施用氮肥和羊粪的内蒙古羊草（Leymus chinensis） 草原土壤颗粒状有机质特征

 【目的】颗粒状土壤有机质（particulate organic matter,POM）是土壤有机质比较活跃的成分,受施肥、耕作及管理等多种因素的影响,本文研究连续5年施用氮肥和羊粪对内蒙古草原围栏封育的表层土壤颗粒状有机质的含量及其化学结构的影响。【方法】采用物理分组法获得游离态颗粒状有机质（FPOM）和包被态颗粒状有机质（OPOM）,并用13C核磁共振法测定其化学结构。【结果】施用氮肥的土壤pH值降低了0.25～0.78个单位,微生物量碳降低了13%～27%,POM含量没有明显变化;而施用羊粪的土壤pH提高了0.47～0.59个单位,微生物量碳提高了19%,POM大幅度提高,特别是FPOM最多提高了96%。OPOM的化学结构几乎不受施肥的影响,但FPOM的化学结构在一定程度上受到施肥特别是羊粪的影响,烷基碳增多,而羰基碳减少。【结论】长期施肥特别是有机肥料,不仅引起草原土壤颗粒状有机质含量的变化,还导致其化学结构的改变,FPOM组分变化更加明显。     

土壤颗粒态有机质中铜和铅的结合特征

为了解土壤颗粒态有机质(POM)中重金属的富集机理,采用化学试剂选择提取方法,把POM中铜和铅分为可交换态、络合态、有机质紧结合态和矿质态等4种形态.结果表明,与细土(＜0.05 mm)相比,POM中铜和铅的有机质紧结合态、可交换态和络合态比例较高;可交换态重金属比例随POM粒径减小而下降,络合态重金属比例却随POM粒径减小而增加.污染土壤中分离获得的POM有较高比例有机质紧结合态铜和铅,而人为添加的铜和铅在POM中主要向络合态和交换态转化.研究认为,污染土壤中有机质紧结合态重金属大多可能是经植物吸收进入土壤后分解残留所致;而POM中络合态和交换态重金属主要通过有机质与土壤重金属的交换和络合作用而富集.     

Long-Term Effect of Nitrogen and Tillage Management on Soil Carbon Pools in the Semiarid Northern Great Plains

No-tillage and manure application effect on soil organic carbon (SOC) and total nitrogen (N) concentrations were studied under a 27-year-old 4-year rotation consisting corn (Zea mays L.)-soybean (Glycine max L.)-wheat (Triticum aestivum L.)-field pea (Pisum sativum L.). Under each crop, four applied N treatments were control, annual urea-N applications at the rate of 45 and 89 kg N ha^?1, and composted beef cattle feedlot manure-N at the rate 179 kg N ha^?1 applied once every four year. For each fertilizer treatment, no-till (NT) and conventional till (CT) were compared for basic soil properties, SOC, and total N within 0–15 cm soil. Manure application significantly reduced soil bulk density and increased SOC and total N over urea-N. Particulate organic matter, mineralizable N, and permanganate-oxidizable C fractions significantly related with SOC. Long-term manure additions and no-tillage had potential to improve soil compaction and maintain SOC over chemical fertilizer N and CT.