典型抗生素在土壤-水-蔬菜系统中迁移分布的研究

通过施用畜禽废物和抗生素污染进行芥菜盆栽试验,从而研究典型抗生素(QNs、SAs和TCs)在土壤.水一蔬菜系统的迁移分布规律.研究结果表明:蔬菜、渗漏水、土壤中均检测到多类抗生素,抗生素在不同介质中的含量与施加抗生素的种类及其含量等因素有关.盆栽后,土壤中抗生素残留量为:QNsTCsSAs,施加猪粪总体上不会造成土壤抗生素污染(ENF除外);只施用畜禽废物的土壤渗漏水中抗生素含量较低(<40.77 μg·L-1),而添加抗生素污染的土壤渗漏水中抗生素含量明显升高(<2.28 mg·L-1),施加猪粪会造成渗漏水抗生素污染;SMT、ENF、OTC、TC这四种药物在盆栽芥菜中均被检出,其中OTC检出率最高,而SMZ则未检出,施加猪粪会造成芥菜抗生素污染.     

生物炭对污染物的土壤环境行为影响研究进展

近年来,生物炭已成为农业、生态修复和环境保护领域的研究热点。一般认为,生物炭具有改善土壤质量、增加土壤碳汇、减少大气CO2浓度以及修复污染环境等功能。大量的生物炭施用到土壤后会改变土壤性质,影响重金属和有机污染物在土壤中的环境行为以及它们在环境中的归趋。本文就生物炭对土壤中重金属的吸附-解吸、在土壤中的形态转化、在土壤-植物系统中迁移行为、对有机污染物的吸附挥发及生物有效性进行了概述;在此基础上,扼要分析了当前生物炭应用存在的环境风险等问题,并从生物炭在土壤中的迁移转化及其归趋、生物炭的长期环境效应以及生物炭应用方向等方面进行了展望。     

土壤微孔对有机物吸附/解吸的影响及其表征

土壤吸附是影响环境中有机化合物迁移、降解及生物有效性的重要过程,而微孔的存在是影响有机化合物慢吸附过程的重要因素之一,土壤孔隙结构(pore structure)及土壤微孔的研究对于理解发生在土壤中的吸附/解吸过程十分必要.综述了近年来土壤微孔对有机化合物吸附解吸行为影响的研究态势,包括土壤的孔隙结构及微孔的存在形式、微孔吸附有机化合物的吸附动力学和可能机理、土壤中微孔表征的技术方法、孔隙大小分布的计算以及对未来的研究展望,以期对土壤有机污染生物修复的深入研究提供理论依据.     

土壤和沉积物中黑碳的环境行为及效应研究进展

土壤和沉积物是全球黑碳排放的主要归宿,土壤和沉积物中黑碳具有复杂的环境行为和环境效应。分析了黑碳的概念,指出应以环境意义为出发点去理解黑碳概念的丰富内涵;描述了黑碳形成过程及其对黑碳理化性质的影响,以及基于此的黑碳分类;总结了黑碳来源辨析的若干种常用方法;讨论了黑碳在土壤/沉积物与其他环境介质之间的迁移循环过程,以及在土壤和沉积物内部的迁移行为;探讨了土壤和沉积物中黑碳的降解行为与稳定性,及其与地-气碳氮温室气体通量、土壤稳定碳库的关系,以及在土壤碳循环模型中的作用;综述了土壤和沉积物中黑碳对有机物、重金属和营养盐的吸附行为及主要机制;提出了今后研究的主要方向,以供相关研究者参考。     

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.     

水溶性有机质对土壤中镉吸附行为的影响

水溶性有机质 (DOM)是陆地生态系统和水生生态系统中的一种很活跃的组分 .本文以赤红壤、水稻土和褐土作为供试土壤 ,研究了来源于稻秆和底泥的DOM对土壤中Cd吸附行为的影响 .DOM对土壤中Cd的吸附行为具有明显的抑制作用 .这种抑制作用与土壤类型和DOM种类有关 .在 3种供试土壤中 ,无论添加稻秆DOM还是底泥DOM ,都会使Cd的最大吸附容量和吸附率明显降低 ,其下降幅度为17 3%～ 93 9%.在添加同一种DOM的前提下 ,DOM对Cd吸附的抑制作用均为 :赤红壤 >水稻土 >褐土 .如果不添加DOM ,则土壤对Cd的最大吸附容量主要取决于土壤固相的吸附特性 ,添加DOM后土壤对Cd的最大吸附容量则主要取决于液相中的DOM .由此推断 ,传统的看法 ,通过施用有机肥来固定土壤中的Cd并达到治理重金属污染土壤的观点值得商榷 .     

武夷菌素对土壤微生物群落及抗生素抗性基因的影响

抗生素抗性基因(antibiotic resistance genes, ARGs)作为一种新型环境污染物近年来受到广泛关注。目前关于抗生素的环境污染研究主要集中于医疗和养殖业,对植物保护领域的农用抗生素环境污染研究很少。武夷菌素是一种环保、高效、广谱的农用抗生素,在农业生产中得到了广泛应用,对农作物真菌性病害具有良好的防治效果。本研究分别选取了未使用武夷菌素和使用武夷菌素的蔬菜大棚中的土壤,通过高通量测序分析了土壤中微生物群落结构,发现两份土壤中主要的微生物群落种类没有发生明显改变,但是优势菌群的丰度有显著差异。通过荧光定量PCR技术,对18个典型的抗生素抗性基因进行了检测,发现aadA、aac(3)-Ⅱ、strA、strB、aacA4、tetX、sulI和intI1 8个基因在两份土壤中的绝对含量和丰度均有显著差异,表明武夷菌素对土壤中微生物的群落结构及抗生素抗性基因的绝对含量和丰度均会造成一定影响。本研究为评估武夷菌素的环境安全性及合理正确使用武夷菌素提供了理论依据,也为其它农用抗生素的相关研究提供了借鉴。     

土壤胶体磷活化迁移的影响因素及分析技术

胶体在土壤磷素迁移中起重要作用.土壤胶体磷活化迁移对土壤磷库的变化和周围水环境质量产生影响.本文介绍了土壤胶体磷研究的相关进展,探讨了土壤理化性质、施肥、降雨、土壤改良剂等因素对胶体磷在土壤赋存迁移中的影响,分析了流场分离、电镜能谱、同步辐射X光近边吸收结构光谱和核磁共振等技术在胶体磷研究中的应用,以及降低胶体磷流失的方法,以期为胶体磷在土壤中赋存变化和迁移机制的研究提供重要信息.
     

溶液pH值及模拟酸雨对两种磺酰脲类除草剂在土壤中行为的影响

采用平衡振荡法和土柱淋洗法,研究了溶液pH及模拟酸雨对土壤中苄嘧磺隆和甲磺隆行为的影响.结果表明,Freundlich方程能较好地描述苄嘧磺隆和甲磺隆的吸附等温线,水-土壤系统pH升高能明显地降低这两种除草剂在土壤中的吸附,促进其在土壤中的迁移,且吸附常数(K_f)与土壤有机质含量、粘土含量呈正相关,而与土壤pH呈负相关.pH值高的模拟酸雨对除草剂在土壤中淋溶贡献较大,且淋溶量随雨量的增大而增大.除草剂在土壤中的淋溶与土壤性质密切相关,有机质含量和粘粒含量较高的土壤对除草剂的持留能力较强.     

溶解性有机质对土壤中有机污染物环境行为的影响

土壤中溶解性有机质(DOM)是生物活性和物理化学反应活性都很活跃的有机组分,主要通过疏水吸附、分配、氢键、电荷转移、共价键、范德华力等多种作用与有机污染物结合,提高溶液中有机污染物的溶解度,改变土壤中有机污染物的吸附-解吸、迁移-转化等环境行为．DOM对有机污染物的吸附-解吸、迁移-转化过程的影响有双重性：一方面,DOM与有机污染物在土壤表面的共吸附可增加土壤对有机污染物的吸附容量,促进有机污染物在土壤中的吸持;另一方面,DOM对有机污染物的增溶作用,有利于土壤中有机污染物的解吸,提高移动性．作为光敏剂,DOM能提高土壤中有机物的光解反应速率．在一定条件下,DOM也可影响土壤中有机污染物的水解过程．DOM对土壤中有机污染物环境行为的影响与DOM和有机污染物的性质及其相互作用的介质条件密切相关．     

湖南主要类型稻田土壤固定态铵含量及其影响因素

通过野外调查取样和室内培养试验 ,应用Silva和Bremner方法 ,研究了湖南省主要类型稻田土壤的固定态铵含量及其影响因素 .结果表明 ,该省主要类型稻田土壤固定态铵含量为 141～ 35 3mg·kg-1,平均为 2 72± 6 7mg·kg-1,占土壤全N的 11.2 % ,高于湖南省以北各地区土壤和本地区地带性土壤———红壤的固定态铵含量 .其含量的顺序为河沙泥 >紫泥田 >潮沙泥 >黄泥田 >红黄泥 .在土壤剖面中 ,固定态铵含量随剖面深度的变化有 4种情况 :在 1m深度范围内随深度增加而增加 ;随深度增加而减少 ;随深度增加而无明显变化 ;土壤剖面中某一土层固定态铵含量明显增加或减少 .土壤固定态铵含量占土壤全N百分比随深度增加而恒增大 .土壤对NH+ 4的固定作用在 30℃下最强 ,高于 2 0℃和 40℃ ;长期淹水有利于潮沙泥、紫泥田和河沙泥对NH+ 4的固定作用 ,但干湿交替有利于黄泥田对NH+ 4的固定作用 .相关分析表明 ,土壤固定态铵含量仅与 <0 .0 1mm粘粒含量呈P0 .0 5水平的显著正相关 ,与有机质、全N、有机N和 <0 .0 0 1mm粘粒含量的相关性均不显著     

Impacts of Environmental Colloids on the Transport of 17 β-estradiol in Intact Soil Cores

Estrogens such as 17-β estradiol (E2) are endocrine-disrupting compounds and can affect the reproductive systems of aquatic organisms. Therefore, it is important to understand the mechanisms of their transport in the environment. E2 and its daughter product estrone (E1) are both strongly adsorbed by soil organic matter and have relatively short half-lives. Reduced contact time with soil makes transport of E2 and E1 in soil more likely. In this study, intact soil cores from three soils representing a range of particle size distribution, structure, and organic matter content were used to compare the transport of E2 with and without the presence of colloidal material fractionated from soil or swine manure. In chemical transport experiments conducted with undisturbed soil columns, E2 and E1 were measured both in solution and attached to suspended solids in column effluent. During the transport experiments, colloids carrying E2 passed through all soils, with the exception of the sandy soil. The presence of colloids decreased the first detection time of E2 in the aqueous phase, was correlated with greater peak E2 concentrations in the effluent of both loamy and clayey soils, but not through the sandy soil, and increased mass fractions of the E2 that was transported.     

Influence of soil texture, moisture, and surface cracks on the performance of a root-feeding flea beetle, Longitarsus bethae (Coleoptera: Chrysomelidae), a biological control agent for Lantana camara (Verbenaceae)

Laboratory studies were conducted to determine the influence of soil texture, moisture and surface cracks on adult preference and survival of the root-feeding flea beetle, Longitarsus bethae Savini and Escalona (Coleoptera: Chrysomelidae), a natural enemy of the weed, Lantana camara L. (Verbenaceae). Adult feeding, oviposition preference, and survival of the immature stages of L. bethae were examined at four soil textures (clayey, silty loam, sandy loam, and sandy soil), three soil moisture levels (low, moderate, and high), and two soil surface conditions (with or without surface cracks). Both soil texture and moisture had no influence on leaf feeding and colonization by adult L. bethae. Soil texture had a significant influence on oviposition, with adults preferring to lay on clayey and sandy soils to silty or sandy loam soils. However, survival to adulthood was significantly higher in clayey soils than in other soil textures. There was a tendency for females to deposit more eggs at greater depth in both clayey and sandy soils than in other soil textures. Although oviposition preference and depth of oviposition were not influenced by soil moisture, survival in moderately moist soils was significantly higher than in other moisture levels. Development of immature stages in high soil moisture levels was significantly slower than in other soil moisture levels. There were no variations in the body size of beetles that emerged from different soil textures and moisture levels. Females laid almost three times more eggs on cracked than on noncracked soils. It is predicted that clayey and moderately moist soils will favor the survival of L. bethae, and under these conditions, damage to the roots is likely to be high. This information will aid in the selection of suitable release sites where L. bethae would be most likely to become established.     

Fate of Mycobacterium avium subsp. paratuberculosis after application of contaminated dairy cattle manure to agricultural soils

Details regarding the fate of Mycobacterium avium subsp. paratuberculosis (basonym, Mycobacterium paratuberculosis) after manure application on grassland are unknown. To evaluate this, intact soil columns were collected in plastic pipes (lysimeters) and placed under controlled conditions to test the effect of a loamy or sandy soil composition and the amount of rainfall on the fate of M. paratuberculosis applied to the soil surface with manure slurry. The experiment was organized as a randomized design with two factors and three replicates. M. paratuberculosis-contaminated manure was spread on the top of the 90-cm soil columns. After weekly simulated rainfall applications, water drainage samples (leachates) were collected from the base of each lysimeter and cultured for M. paratuberculosis using Bactec MGIT ParaTB medium and supplements. Grass was harvested, quantified, and tested from each lysimeter soil surface. The identity of all probable M. paratuberculosis isolates was confirmed by PCR for IS900 and F57 genetic elements. There was a lag time of 2 months after each treatment before M. paratuberculosis was found in leachates. The greatest proportions of M. paratuberculosis-positive leachates were from sandy-soil lysimeters in the manure-treated group receiving the equivalent of 1,000 mm annual rainfall. Under the higher rainfall regimen (2,000 mm/year), M. paratuberculosis was detected more often from lysimeters with loamy soil than sandy soil. Among all lysimeters, M. paratuberculosis was detected more often in grass clippings than in lysimeter leachates. At the end of the trial, lysimeters were disassembled and soil cultured at different depths, and we found that M. paratuberculosis was recovered only from the uppermost levels of the soil columns in the treated group. Factors associated with M. paratuberculosis presence in leachates were soil type and soil pH (P < 0.05). For M. paratuberculosis presence in grass clippings, only manure application showed a significant association (P < 0.05). From these findings we conclude that this pathogen tends to move slowly through soils (faster through sandy soil) and tends to remain on grass and in the upper layers of pasture soil, representing a clear infection hazard for grazing livestock and a potential for the contamination of runoff after heavy rains.     

Abundance of Antibiotic Resistance Genes in Bacteriophage following Soil Fertilization with Dairy Manure or Municipal Biosolids,and Evidence for Potential Transduction

Animal manures and municipal biosolids recycled onto crop production land carry antibiotic-resistant bacteria that can influence the antibiotic resistome of agricultural soils, but little is known about the contribution of bacteriophage to the dissemination of antibiotic resistance genes (ARGs) in this context. In this work, we quantified a set of ARGs in the bacterial and bacteriophage fractions of agricultural soil by quantitative PCR. All tested ARGs were present in both the bacterial and phage fractions. We demonstrate that fertilization of soil with dairy manure or human biosolids increases ARG abundance in the bacterial fraction but not the bacteriophage fraction and further show that pretreatment of dairy manure can impact ARG abundance in the bacterial fraction. Finally, we show that purified bacteriophage can confer increased antibiotic resistance to soil bacteria when combined with selective pressure. The results indicate that soilborne bacteriophage represents a substantial reservoir of antibiotic resistance and that bacteriophage could play a significant role in the horizontal transfer of resistance genes in the context of an agricultural soil microbiome. Overall, our work reinforces the advisability of composting or digesting fecal material prior to field application and suggests that application of some antibiotics at subclinical concentrations can promote bacteriophage-mediated horizontal transfer of ARGs in agricultural soil microbiomes.     

Hexavalent Chromium Reduction in Soils Contaminated with Chromated Copper Arsenate Preservative

The toxicity and mobility of chromium in the environment greatly depends upon its speciation. The reduction of hexavalent chromium to trivalent chromium in a soil environment was examined by spiking three soil types (sandy, clayey, and organic soils) with a common wood preservative solution known as chromated copper arsenate (CCA). Chromium in the CCA preservative solution exists in the hexavalent form. The total and hexavalent chromium concentrations (mg/kg) were measured over a period of 11 months. Leachable chromium concentrations (mg/L) were assessed using the synthetic precipitation leaching procedure (SPLP). The degree and rate of hexavalent chromium reduction were similar for the sand and clayey soil, but much greater for the organic soil. Most of the chromium reduction occurred within the first month of the experiment. At the end of the experiment, approximately 50% of the hexavalent chromium was converted to the trivalent form in the sand and clayey soils. Hexavalent chromium concentrations were below detection in the organic soil at the end of the experiment. Nearly all of the chromium observed in the SPLP leachates was in the form of hexavalent chromium. Chromium leaching was thus greatest in the sand and clay soils where the hexavalent chromium persisted. The results indicate that hexavalent chromium in soils can persist for considerable time periods, in particular in soils with low organic matter content.

     

The use of bioassays for the risk assessment of toxic leachates: an experimental study

Solid wastes from the oil-shale industry produce leachates containing toxic compounds such as heavy metals and persistent polycyclic aromatic hydrocarbons (PAH). The hazard to the environment represented by waste leachates depends not only on their chemical composition, but also on the mobility and bioavailability of toxic contaminants in soils. We evaluated the applicability of bioassays for toxicity assessment of the bioavailable fraction of heavy metals and PAH in soils, in experiments with samples of four different soil types (Rendzina, Brown pseudopodzolic, Typical brown, Sodpodzolic), the pH of which ranged from 6.2 to 7.2. The toxicity of the bioavailable fraction of the soil contaminants was assessed with the dehydrogenase enzyme activity assay, and with a Toxkit microbiotest with the crustacean, Thamnocephalus platyurus, after treatment of the soil samples with an artificial solution containing chromium (III), lead (II), copper (II), cadmium (II) and pyrene. The test results confirm those of earlier experiments, which characterised the sorption potential of investigated soils for the same compounds. Both tests turned out to be sufficiently sensitive, and hence can be recommended as effective and useful tools for the assessment of the bioavailable fraction of soil contaminants.     

湖南稻田土壤固定态铵含量的季节变化及生物有效性

以湖南省3种固定态铵含量较高的稻田土壤为供试土壤,通过盆栽试验,研究了稻田土壤固定态铵在植稻期间的动态变化及其生物有效性。结果表明,稻田土壤的固定态铵含量处于不断的变化之中,施氮肥和有机肥使土壤固定态铵含量升高,而水稻吸收氮则使土壤固定态铵含量降低,其变化趋势与土壤碱解氮含量变化相似。“新固定的”固定态铵基本对当季水稻全部有效。而“原有的”固定态铵对当季作物和后季作物部分有效,就供试土壤而言,在水稻生育期间,土壤固定态铵的释放量是潮沙泥>紫泥田>河沙泥;就不同水稻而言,早稻生育期间土壤固定态铵的释放量大于晚稻生育期间土壤固定态铵的释放量。     

Nitrogen mineralisation potential in calcareous soils amended with sewage sludge

Mineralisation of organic N is an important consideration when determining the annual amount of sewage sludge to be applied to agricultural soils. The mineralisation of sludge organic N was studied in two different textured soils (clayey and sandy soil) treated with aerobic and anaerobic sludge at two different rates (30 and 50 g sludge kg(-1) soil). The mineralisation of sludge organic N was determined during 20 weeks incubation period by analysis of inorganic N produced by a non-leached procedure. Sludge organic N mineralisation was influenced by soil type, organic N mineralisation being greater in the sandy soil (from 30% to 41%) than in the clayey soil (from 13% to 24%). Mineralisation rates decreased rapidly the first two weeks, followed by a slower decrease with time. Although total mineralisation increased with sludge addition rate, net mineralisation decreased with sludge addition rate, probably due to denitrificaton losses. The aerobically treated sludge gave higher mineralisation rates than the anaerobically treated one. The values of N0 and k for treated soils varied depending on the type of sludge and soil.     

Metal Transport and Bioavailability in Soil Contaminated with CCA-Treated Wood Leachates

A laboratory study was conducted to investigate metal transport and accumulation within soils contaminated with As, Cr, and Cu from CCA-treated wood leachates. New blocks of CCA-treated wood were leached using synthetic rainwater. Soil columns were constructed and filled with three different soils, including a sandy soil, an organic soil and a clay soil. The leachate was applied intermittently until 80 pore volumes were eluted through each column. Metal concentrations (Cu, Cr, and As) were measured in the leachate before passage through the columns as well as in each elutriate fraction collected. Chemical analysis was complemented with toxicity testing using Ceriodaphnia dubia, Selenastrum capricornutum, and MetPLATE?. Following application of 80 pore volumes of leachate, the columns were dissected and the profile of the metal concentrations within each column was determined. A comparison of the arsenic, chromium and copper leaching patterns found arsenic to be the most mobile, with copper the most retained in the soil columns (As < Cr < Cu). Transport patterns of As differed in the three soil types, with observed mobility highest in the sandy soil and lowest in the clay soil. The three metals accumulated in the top layer of soil. Arsenic posed the greatest risk when soil concentrations were compared to risk-based target levels. Although metals were detected in soil elutriates, no toxicity was detected in any of the soil column elutriates using any of the three toxicity assays.