大兴安岭中段森林土壤的黑碳含量及其在不同粒级中的分布

土壤黑碳由于具有生物化学惰性被视为土壤稳定碳库的主要成分.本文量化了大兴安岭中段森林土壤黑碳,分析了黑碳在各粒级内的分布,并探讨了黑碳的稳定机制及其在土壤碳库中的重要性.结果表明: 土壤黑碳表聚现象明显,表层黑碳占总剖面(64 cm)的68.7%,随着土层加深黑碳含量显著降低,但黑碳占有机碳的比例却呈现上升趋势.气候条件影响大兴安岭地区土壤黑碳的分布,相对寒冷和湿润的气候条件提高了土壤固持黑碳的潜力;土壤黑碳在各粒级内所占比例表现为黏粒>粉粒>细砂>粗砂,尽管黏粒中黑碳含量最高,并随土层深度增加而升高,但黏粒中黑碳占有机碳的比例却无明显变化,黑碳/有机碳的升高主要源于细砂与粉粒中黑碳的增加;黑碳的生物化学惰性是表层黑碳的主要稳定机制,而深层的黑碳除了其自身抗性外,黏粒矿物的化学保护发挥着重要作用;黑碳不仅作为稳定碳库的主要成分,在颗粒有机碳组分中仍占相当大的比例,因此黑碳的存在提高了土壤稳定性碳储量与碳汇能力.     

土壤活性有机碳

土壤活性有机碳是土壤中活跃的化学组分,能显著影响土壤化学物质的溶解、吸附、解吸、吸收、迁移乃至生物毒性等行为,近年来土壤活性有机碳已成为土壤、环境和生态科学领域所关注的焦点和研究的热点。本文从土壤活性有机碳的来源、组成、含量、影响因素以及环境意义等方面做了简要的论述。一般认为,土壤活性有机碳来源于植物凋落物的分解、根系分泌物、土壤有机质的水解、土壤微生物本身及其代谢产物,因为来源的不同土壤活性有机碳含量也不同;影响土壤活性有机碳的因素有很多,研究表明,土壤活性有机碳随季节和湿度的变化呈现十分强烈的变异趋势;土地利用方式改变对土壤活性有机碳的影响在不同的研究中有不同的结果;土地管理措施如耕作、施有机肥和化肥、改变土壤pH值等对土壤活性有机碳也有很大的影响。土壤活性有机碳的生态环境效应主要表现在它对调节土壤养分流有很大影响,与土壤内在的生产力高度相关;它作为重金属的有机配体,对土壤溶液中的微量重金属的可移动性和迁移过程以及金属复合物的形成过程有着重要作用;它的存在影响农药在土壤中的截留、增加农药的水溶性,并影响农药在土壤中的运动;它对温室气体的排放、水体富营养化、岩石圈溶蚀都有很重要的作用。同时指出了未来的研究方向。     

不同功能区城市林业土壤黑碳含量及来源——以南京市为例

由于城市化过程中人为活动的影响,城市林业土壤的性质发生了很大变化。城市林业土壤黑碳由于来源的多样性和受到人为活动的影响,其分布表现出独特的特征。以南京市为对象,调查分析了不同功能区城市林业土壤黑碳的含量及可能来源。结果表明:不同功能区城市林业土壤黑碳含量差异很大,其变幅为0.77-21.27g/kg。道路绿化带土壤黑碳含量显著高于其它功能区,居民区含量最低。黑碳在土壤表层中含量均高于表下层,黑碳富集于土壤表层。道路绿化带表层土壤黑碳含量与有机碳含量的比值(BC/SOC)为0.55,土壤黑碳的碳同位素比值(δ¹³C_PDB)为-27.04‰,与其它功能区差异显著,城市交通污染对土壤黑碳积累产生强烈影响。     

汕头红树林湿地沉积物多环芳烃垂直分布特征

采集了汕头国际湿地核心区红树林表层沉积物上层(0～10 cm)和下层(10～20cm)样品,用超声溶剂萃取和GC-MS法分析了沉积物中的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)、有机碳、黑碳和粒径的组成.结果显示,沉积物上、下层均以4环PAHs的含量最高,不同环数PAHs表现为中环数含量较高,低环和高环含量较低;上层∑PAHs含量明显大于下层,同时沉积物上层∑PAHs含量、有机碳和黑碳及粘粒、粉砂的质量分数均高于下层;pH没有变化.相关性分析显示,沉积物上、下层中的有机碳与∑PAHs含量无相关关系,黑碳、PAHs含量和粉砂表现为两两显著相关,表明沉积物中粉砂是影响PAHs在沉积物中行为和归宿的重要因素,而黑碳是形成分层效应的根本影响因素.     

中国森林土壤碳储量与土壤碳过程研究进展

森林是陆地生态系统的主体,是陆地上最大的碳储库和碳吸收汇。国内外研究表明,土壤亚系统在调节森林生态系统碳循环和减缓全球气候变化中起着重要作用。但是,由于森林类型的多样性、结构的复杂性以及森林对干扰和变化环境响应的时空动态变化,至今对森林土壤碳储量和变率的科学估算,以及土壤关键碳过程及其稳定性维持机制的认识还十分有限。综述了近十几年来我国森林土壤碳储量和土壤碳过程的研究工作,主要包括不同森林类型土壤碳储量、土壤碳化学稳定性、土壤呼吸及其组分、土壤呼吸影响机制、气候变化与土地利用对土壤碳过程的影响等;评述了土壤碳过程相关科学问题的研究进展,讨论了尚未解决的主要问题,并分析了未来土壤碳研究的发展趋势,以期为促进我国森林土壤碳循环研究,科学评价森林土壤碳固持潜力及其稳定性维持机制和有效实施森林生态系统管理提供科学参考。     

农田作物同化碳输入与周转的生物地球化学过程

作物同化碳在“大气-植物-土壤”系统中流通的生物地球化学过程,显著影响全球陆地生态系统碳循环过程。作物同化碳是土壤有机碳的重要来源,与根际环境及作物生长发育有密切联系,但由于其复杂性和多变性,作物生长期内同化碳在土壤中的分配、转化与稳定的机理尚不十分清楚。因此,综述了作物同化碳向土壤碳库输入及其对土壤有机碳库的贡献,在土壤碳库中的分配与转化特征,在土壤中流通的微生物机制以及同化碳在土壤-微生物系统分配、稳定的微观机制。探讨同化碳在地上部-根际-土壤系统中的分配及调节机制,土壤界面同化碳流动过程与土壤微生物多样性形成的关系;提出了在不同生态系统尺度上加强作物同化碳在土壤-作物系统中分配过程的定量研究对于明确陆地生态碳循环过程的重要意义;指出了研究作物同化碳向土壤碳库迁移、分配定量过程与机制的重要性,以及应用显微镜成像技术与同位素示踪技术相结合的纳米二次离子质谱技术、和微生物分子与群落生态相偶联的技术是未来研究作物同化碳生物地球化学特性的有效手段。     

土壤碳库构成研究进展

土壤碳库是陆地生态系统中最大的碳库。土壤碳库的构成影响其累积和分解,并直接影响全球陆地生态系统碳平衡,同时也影响土壤质量变化。弄清土壤碳库的组分及构成,是进一步研究土壤碳库变化机制的关键。综述了土壤碳库的组分和构成,对有机碳库进行不稳定性有机碳库和稳定有机碳库归类,描述各类碳库的性质,并对各类碳库的分析测定方法进行了评述。提出在土壤碳构成中增加黑碳和煤炭(碳)以完善土壤有机碳构成框架。在未来研究中,应加强土壤无机碳及湿地土壤和新开发新复垦的重构土壤碳库构成及变化,各类碳库化学构成,交叉重叠的定量关系,碳库之间的转化及在土壤中的迁移,黑碳对土壤碳库稳定性及土壤质量的影响,煤开采扰动区煤炭(碳)对土壤质量的影响及环境效应等科学问题的研究。     

二甲基硅油的环境行为与生态效应研究进展

二甲基硅油(polydimethylsiloxane,PDMS)广泛应用于工业产品、医药保健品和个人护理品中.PDMS在污水处理过程中几乎不被生物降解,主要随剩余污泥排放进入环境,仅有少量PDMS吸附在悬浮固体或污泥颗粒表面随污水排放进入水体和沉积物中.现有研究表明,PDMS在沉积物中较难迁移和降解;而在不同类型土壤中均可以降解.PDMS对水生态系统风险较低,对底栖生物的急性毒性也不明显;在土壤环境中,PDMS及其降解产物对土壤微生物、土壤动物及农作物的生长和活动没有显著的影响.根据目前为数不多的研究,PDMS及其降解产物在各种环境中的生态毒性都较小,但随着PDMS产量和使用量的快速增长,其在环境中的含量呈快速上升趋势,有必要进一步明确PDMS对环境的潜在威胁.     

二甲基硅油的环境行为与生态效应研究进展

二甲基硅油(polydimethylsiloxane, PDMS)广泛应用于工业产品、医药保健品和个人护理品中.PDMS在污水处理过程中几乎不被生物降解,主要随剩余污泥排放进入环境,仅有少量PDMS吸附在悬浮固体或污泥颗粒表面随污水排放进入水体和沉积物中.现有研究表明,PDMS在沉积物中较难迁移和降解;而在不同类型土壤中均可以降解.PDMS对水生态系统风险较低,对底栖生物的急性毒性也不明显;在土壤环境中,PDMS及其降解产物对土壤微生物、土壤动物及农作物的生长和活动没有显著的影响.根据目前为数不多的研究,PDMS及其降解产物在各种环境中的生态毒性都较小,但随着PDMS产量和使用量的快速增长,其在环境中的含量呈快速上升趋势,有必要进一步明确PDMS对环境的潜在威胁.     

石墨烯的环境行为及其对环境中污染物迁移归趋的影响

石墨烯是当前研究最热的碳纳米材料,具有独特的理化特性,在各领域具有广阔的应用前景.随着其生产和使用量的不断增大,石墨烯不可避免地会进入到环境中,从而给生态环境和人类健康带来风险.深入理解石墨烯在环境中的行为和归趋,探讨石墨烯对污染物环境行为的影响,对于科学客观评价石墨烯的环境风险具有十分重要的意义.本文对石墨烯的环境行为及其对污染物迁移归趋的影响进行了综述,主要介绍了石墨烯在水环境中的胶体特性和稳定性,以及在多孔介质中的迁移,重点探讨了石墨烯与重金属和有机物之间的相互作用,并从吸附机理、石墨烯与土壤组分之间的相互作用、石墨烯对污染物在环境中迁移及生物有效性的影响、石墨烯的定量方法等方面对该研究领域的前景和重点进行了展望,以期为该领域的深入研究提供借鉴并拓展新的思路.     

Polycyclic Aromatic Hydrocarbons (PAHs) in Soil and Sediment from Industrial,Residential, and Agricultural Areas in Central South Africa: An Initial Assessment

Polycyclic aromatic hydrocarbons (PAHs) are of global concern due to their ubiquitous presence, toxicity, and carcinogenicity. No data on PAHs in soils from South Africa have been published, even though it has the largest economy and industrial base in Africa. During this initial assessment, the levels of PAHs were determined in soils and sediments collected from central South Africa, specifically targeting industrial, residential, and agricultural areas. Analysis was performed by gas chromatography/mass spectrometry (GC/MS). The total concentration of PAHs (Σt-PAH) ranged between 44 and 39,000 ng/g, dw and the concentration of carcinogenic PAHs (Σc-PAH) ranged between 19 and 19,000 ng/g, dw. Pyrogenic processes were the most likely sources, with minimal petrogenic contributions. PAH levels were in the same range as levels reported from other countries, and the majority of the sites did not exceed Canadian environmental quality guidelines. Based on assumptions for dermal contact and ingestion of PAH-contaminated soil, we provisionally calculated only a small increase in cancer risk, but additional PAH inhalation could add considerably to this risk. Our data indicates a need for more analysis in industrial and residential areas, and should include air.     

Determination of Polycyclic Aromatic Hydrocarbons and Trace Metals in New Orleans Soils and Sediments

Soil and sediment samples from New Orleans have been collected and analyzed for contamination by 16 polycyclic aromatic hydrocarbons (PAHs) and 8 trace metals. Total PAH contents were found to vary from 40 μ g/kg to 40,000 μ g/kg, and concentrations of total metals varied in the range of 80 mg/kg and 7600 mg/kg. Source analysis of PAHs using diagnostic concentration ratios such as phenanthrene/anthracene and fluoranthene/ pyrene indicated that PAHs found at elevated concentrations in New Orleans soils and sediments were of pyrolytic origins. Spearman rank bivariate correlation analysis revealed significant correlations between soil PAHs and metals (r = 0.80, p < 0.0001) and between sediment PAHs and metals (r = 0.62, p < 0.05), suggesting common pollution sources for the two groups of environmental pollutants. Strong correlations were also found between Pb and Zn in soils (r = 0.93, p < 0.0001) as well as in sediments (r = 0.65, p < 0.05).     

Diffuse PAH contamination of surface soils: environmental occurrence,bioavailability, and microbial degradation

The purpose of this review is to recognize the scientific and environmental importance of diffuse pollution with polycyclic aromatic hydrocarbons (PAHs). Diffuse PAH pollution of surface soil is characterized by large area extents, low PAH concentrations, and the lack of point sources. Urban and pristine topsoils receive a continuous input of pyrogenic PAHs, which induces a microbial potential for PAH degradation. The significance of this potential in relation to black carbon particles, PAH bioaccessibility, microbial PAH degradation, and the fate of diffuse PAHs in soil is discussed. Finally, the state-of-the-art methods for future investigations of the microbial degradation of diffuse PAH pollution are reviewed.     

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by soil particles: influence on biodegradability and biotoxicity

Summary Polycyclic aromatic hydrocarbon (PAH) biodegradation was investigated in contaminated soils from two different industrial sites under simulated land treatment conditions. Soil samples from a former impregnation plant (soil A) showed high degradation rates of PAHs by the autochthonous microorganisms, whereas PAHs in material of a closed-down coking plant (soil B) were not degraded even after inoculation with bacteria known to effectively degrade PAHs. As rapid PAH biodegradation in soil B was observed after PAHs were extracted and restored into the extracted soil material, the kind of PAH binding in soil B appears to completely prevent biodegradation. Sorption of PAHs onto extracted material of soil B follows a two-phase process (fast and slow); the latter is discussed in terms of migration of PAHs into soil organic matter, representing less accessible sites within the soil matrix. Such sorbed PAHs are suggested to be non-bioavailable and thus non-biodegradable. By eluting soil B with water, no biotoxicity, assayed as inhibition of bioluminescence, was detected in the aqueous phase. When treating soil A analogously, a distinct toxicity was observed, which was reduced relative to the amount of activated carbon added to the soil material. The data suggest that sorption of organic pollutants onto soil organic matter significantly affects biodegradability as well as biotoxicity.     

An Integrated Case Study for Evaluating the Impacts of an Oil Refinery Effluent on Aquatic Biota in the Delaware River: Advanced Chemical Fingerprinting of PAHs

More than one thousand samples were collected and analyzed to evaluate the potential impact of Motiva's oil refinery effluent on the receiving water, sediment, and biota of the Delaware River. The data collected from these samples were used with advanced chemical fingerprinting of polycyclic aromatic hydrocarbons (PAHs) in Motiva's oil refinery effluent to differentiate Motiva-related PAHs in sediment and biota from other sources. The PAHs released from the refinery between 1999 and 2002 were dominated by petrogenic 4-ring PAHs. Specifically, the refinery signature exhibited relatively high levels of fluoranthenes/pyrenes with two (FP2) and three (FP3) alkyl groups and benz(a)anthracene/chrysenes with two (BC2), three (BC3), and four (BC4) alkyl groups. This PAH signature, attributed to accelerated degradation of low molecular weight PAHs in the Motiva wastewater treatment plant, exhibited little variability over time relative to the background patterns in the Delaware River. This distinctive feature of the Motiva effluent allowed the identification of this source in other samples. Water and sediment samples identified a range of PAH characteristics associated with the Delaware River urban background signature. These characteristics included varying levels of 2- to 3-ring PAHs (likely from weathered automotive fuel, marine fuel, or bilge tank discharges), pyrogenic 4- to 6-ring PAHs (from partially combusted organic material like soot), and perylene (diagenetic product of terrestrial plant decomposition). The Motiva hydrocarbon signature was only evident at moderate to low levels in selected near-field sampling stations for sediment, bivalves, and effluent/nearfield water. PAHs in the river sediments beyond the near-field area were consistently associated with samples containing the Delaware River urban background signature, and exhibited little to no effect from the Refinery.     

多环芳烃类化合物在土壤上的吸附

研究了几种多环芳烃化合物在土壤上的吸附行为．通过一个连续投药－取样试验装置,在没有任何其它有机试剂干扰的情况下,测定了荧蒽与菲在土壤上的吸附量．研究表明,这两种多环芳烃化合物在土壤上的吸附量与土壤有机质含量之间呈显著相关．对多环芳烃化合物的分子结构及理化特性,如辛醇－水分配系数、溶解度等参数与ＬｏｇＫｏｃ关系的研究发现多环芳烃化合物的ＬｏｇＫｏｃ与化合物的水溶性、辛酸－水分配系数以及分子结构中的苯环数线性相关．     

城市土壤碳循环与碳固持研究综述

城市化过程带来的土地利用变化和环境污染是全球变化的重要方面,城市为人们了解人类与自然复合生态系统对全球变化的影响及其对全球变化的响应过程提供一个独特的"天然实验室"。陆地生态系统碳循环是全球变化研究的热点领域之一,然而,人们对城市在全球碳循环中的作用和影响知之甚少,城市土壤碳循环研究处于起步阶段。介绍了城市土壤的主要特性和碳循环特征,指出强烈的人为作用是其最突出的特点;综述了城市土壤碳库、碳通量和碳固持研究方面取得的进展;探讨了城市化过程中土地利用变化、土壤中生物及土壤管护措施、城市小气候、大气污染沉降和土壤污染等对土壤碳循环的影响;提出未来城市碳循环研究需要开展长期系统监测、深化城市土壤碳循环机制研究、创新研究范式和研究方法、并将研究成果与城市景观规划与设计相结合,提升城市土壤碳管理能力。     

Differences in Sediment Organic Matter Composition and PAH Weathering between Non-Vegetated and Recently Vegetated Fuel Oiled Sediments

We examined polycyclic aromatic hydrocarbon (PAH) attenuation in contaminated field sediments after only 2 years of plant growth. We collected sediments from vegetated and non-vegetated areas at the Indiana Harbor Canal (IHC), an industrialized area with historic petroleum contamination of soils and sediments. PAH concentrations, PAH weathering indices, and organic matter composition in sediments colonized by Phragmites, cattails, or willow trees were compared to the same indices for non-vegetated sediments. We hypothesized that bulk sediment and humin fractions with measurable increases in plant organic matter content would show measurable changes to PAH attenuation as indicated by more weathered PAH diagnostic ratios or reduced PAH concentrations. Carbon-normalized PAH concentrations were lower in vegetated bulk sediments but higher in vegetated humin fractions relative to non-vegetated sediment fractions. Total organic carbon content was not indicative of more weathered N₃/P₂ ratios or reduced PAH concentrations in vegetated sediment fractions. More weathered N₃/P₂ ratios were observed with increased modern carbon (plant carbon) content of vegetated sediment fractions. Phragmites sediments contained more modern carbon (plant carbon) and more weathered PAH ratios [C₃-naphthalenes and C₂-phenanthrenes (N₃/P₂)] than willow, cattail, and non-vegetated sediments.