NaOH预处理对秸秆与蓝藻混合厌氧发酵产沼气的影响

以稻秸和蓝藻为原料,在实验室自制小型发酵装置内进行混合物料厌氧发酵实验,研究不同质量分数NaOH预处理对秸秆与蓝藻混合厌氧发酵产沼气的影响。结果表明,经过NaOH预处理后,稻秸组分被破坏,产气量较对照组有明显增加,发酵时间缩短。扫描电镜观察显示,经碱性预处理过的稻草秸秆孔隙度增大,机械组织暴露,酶解的有效比表面积增大,酶解速率加快。NaOH质量分数为6%的处理组产气效果最好,总产气量比对照组高出248%,且甲烷平均含量达到58.89%,预处理效果最为理想。     

芦苇秸秆厌氧发酵影响因素正交实验及产气潜力研究

以芦苇秸秆为发酵原料,采用正交实验法,在湿式和干式批次发酵条件下,考察了预处理方式、发酵浓度和接种量对芦苇厌氧发酵沼气产量的影响。结果表明,以Na OH预处理、接种量30%、TS浓度12%的处理发酵情况最好,在第3天即出现产气高峰,最高日产气量达2.1 L,总产气量达42.8 L。芦苇的总TS和总VS产气率分别达285.7 L·kg-1TS、402.8 L·kg-1VS,具有较高的产气潜力。根据正交实验方差分析结果,芦苇厌氧发酵的影响因素的影响程度是预处理方式发酵浓度接种量,确定芦苇厌氧发酵的最佳工艺条件为:Na OH预处理、接种量100%、发酵浓度TS 12%。     

污泥与香蕉秸秆混合厌氧发酵特性

为提高污泥、香蕉秸秆厌氧发酵的甲烷产率,采用批式实验,研究污泥与香蕉秸秆厌氧发酵及其协同特性。实验结果表明:污泥和香蕉秸秆实验组分别会出现氨抑制、酸抑制现象,影响厌氧发酵的进行,一段时间后都可以自行解除抑制恢复产气。热碱污泥、碱浴秸秆实验组均可以解除抑制作用,甲烷产率较预处理前分别提高43%、176%。混合物质发酵实验组的甲烷产率较热碱污泥、碱浴秸秆实验组分别提高了110%、30%,较污泥和香蕉秸秆实验组分别提高了200%、259%。说明污泥和香蕉秸秆混合厌氧发酵,可以提高甲烷产率。     

预处理方法对水葫芦厌氧发酵产沼气的影响

水葫芦可作为厌氧发酵产沼气的原料。研究发现,水葫芦自身的生物特性会制约其产气潜力的发挥,而发酵前预处理有助于解决这一问题。以采自昆明滇池的新鲜水葫芦为研究对象,分别采用物理法(切分法、压榨法),化学法(酸处理法、碱处理法和金属离子处理法)和生物法(酶处理法)对其进行预处理,以预处理后的水葫芦为原料进行发酵产沼气实验。结果表明,金属离子处理的原料产气效果最佳,在中温35℃,进样浓度7.4%(TS)时,其原料TS产气率、平均甲烷浓度和原料容积产气率分别为744.55 m3/t、59.32%和0.144 m3/(m3·d),与切分处理原料相比提高了88%、13%和87%。其余处理方法也在不同程度上优化了水葫芦的产气效果。因此,以预处理的方式来提高水葫芦的生物利用率和产气效率是可行的。     

NaOH预处理对杂交狼尾草厌氧发酵产沼气的影响

研究了Na OH预处理对杂交狼尾草厌氧消化制沼气的影响。采用质量分数分别为0%、2%、4%、6%和8%的Na OH溶液对杂交狼尾草进行碱预处理,在中温(35℃)、TS质量分数6%、接种率20%及初始p H为7.0条件下,进行厌氧发酵实验。对比了处理前后原料木质纤维素含量,探讨了不同浓度预处理对发酵过程沼气产量、甲烷浓度、p H以及产气速率的影响。结果表明,Na OH预处理有助于提高杂交狼尾草厌氧发酵的产气量和产气速率,其中4%Na OH预处理为较优条件。经4%Na OH溶液常温浸润24 h后,杂交狼尾草木质素降解率最大,比未处理实验组提高了31.2%;厌氧发酵总产气量比未处理实验组提高了31.6%。     

蓝藻与污泥混合厌氧发酵产沼气的初步研究

为了实现太湖蓝藻打捞后的快速处置，对厌氧颗粒污泥、消化污泥、剩余污泥与蓝藻混合厌氧发酵产沼气进行了研究。结果表明，蓝藻与污泥混合可以有效促进沼气发酵。在蓝藻与厌氧颗粒污泥物料比为6∶1时，产气效果最佳，沼气产率为73 mL/g VS，平均甲烷含量为69%，最大产气速率为138 mL/d，累计产甲烷量为50 mL CH₄/g干物质，分别是蓝藻与消化污泥、剩余污泥混合发酵时的1.5倍和2.3倍。厌氧颗粒污泥、消化污泥、剩余污泥与蓝藻混合，其VS降解率为11.40%～13.73 %，COD减少了27.97%～46.38%。厌氧发酵对蓝藻藻毒素的含量有较大影响，分别从356、366和244 μg/L降低到检测限5 μg/L 以下。     

小麦秸秆预处理对厌氧消化性能的影响研究

针对小麦秸秆厌氧消化水解限速步骤,研究了酸、碱和污泥发酵消化液(以下简称消化液)预处理对小麦秸秆厌氧消化性能的影响。结果表明,酸和消化液预处理可以加速小麦秸秆水解酸化,在厌氧发酵第4天时产气中测得甲烷,早于对照和碱预处理。与对照相比,酸、消化液和碱预处理后小麦秸秆和污泥共消化体系的产气量可分别提高13.7%、12.0%和9.2%,产甲烷量可分别提高7.4%、9.5%和5.2%,但碱预处理会延滞厌氧消化产甲烷阶段。厚壁菌门(Firmicutes)是厌氧消化反应器中最主要的菌门,主要包括己酸菌属(Caproiciproducen s)、乙醇生孢产氢菌属(Hydrogenispora)、瘤胃梭菌属(Ruminiclostridium)、罗伊氏乳杆菌属(Lactobacillus)和Ruminiclostridium_1属等,其中己酸菌属和乙醇生孢产氢菌属可以作为小麦秸秆和污泥共消化的监测指标,在厌氧消化前期反应器中微生物主要为己酸菌属,而后期主要为乙醇生孢产氢菌属。     

碱液预处理玉米秸秆的条件优化及添加剂的选择

利用稀NaOH溶液预处理玉米秸秆,以去除木质素,减少半纤维素、纤维素的损失为目的,采用响应曲面法对预处理条件进行优化,得到的最佳预处理条件为:NaOH溶液浓度0.77%(w/w),预处理时间16 h,温度45.6℃。并且,进一步研究了不同添加剂(聚乙二醇、吐温-80和尿素)与NaOH溶液协同作用下秸秆中木质素的去除效果,结果表明尿素与NaOH的混合溶液对木质素去除效果最显著。秸秆在45.6℃,0.77%NaOH和0.2%尿素混合溶液中浸泡16 h后,纤维素回收率为86.33%,半纤维素回收率为69.89%,木质素去除率为64.93%;与原秸秆相比,纤维素含量提高了31.70%,半纤维素含量提高了6.62%,木质素含量减少了46.48%。     

城市生活垃圾和污水处理厂剩余污泥混合发酵的原料配比优化研究

以城市生活垃圾和污水处理厂的剩余污泥为混合原料,研究了混合原料的不同配比对厌氧发酵过程及产气的影响。结果表明:城市生活垃圾与剩余污泥以挥发性固体(VS)质量比为2∶1混合后,厌氧发酵效果最好,累计产气量最高,达到8 721mL,发酵后的总固体(TS)、VS、COD去除率分别达43.65%、35.98%、47.88%;各实验组在发酵过程中的pH、氨氮浓度和碱度均在合理范围内,未对厌氧发酵反应造成影响;以适当配比的城市生活垃圾和剩余污泥为混合原料,进行中温联合厌氧发酵是可行的,联合厌氧发酵可以弥补单一原料的缺陷,在一定程度上改善厌氧发酵效果。     

汽爆秸秆高温固态发酵沼气的研究

沼气液态深层发酵及秸秆的物理、化学和生物预处理方式存在效率低、污染重等问题。为了解决这些问题，对蒸汽爆破预处理方式以及固态发酵在玉米秸秆沼气化中的应用进行了研究。秸秆经过蒸汽爆破预处理后，在50℃的高温条件下进行固态发酵沼气，甲烷产量达到138.2 mL/g TS。通过单因素实验优化，确定最佳发酵条件为：固液比1∶7，初始pH值7.5，接种量35%，NH₄HCO₃添加量0.04 g/g干汽爆秸秆，纤维素酶用量30 IU/g干汽爆秸秆，发酵温度50℃。在上述实验条件下，汽爆秸秆的甲烷产量提高至153.0 mL/g TS，是未汽爆秸秆的2.9倍。发酵后秸秆纤维素和半纤维素的降解率分别为59.86%和67.22%。因此，蒸汽爆破预处理有助于提高秸秆的产气量和降解率。高温固态发酵不仅可以缩短发酵延迟期，提高产气效率，而且发酵结束后不会产生大量废液，对环境友好。     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

A History of Dry Cleaners and Sources of Solvent Releases from Dry Cleaning Equipment

Approximately 25, 000-35, 000 dry cleaning facilities currently operate in the U.S. The release of perchloroethylene and other solvents from these establishments represents a major source of soil and groundwater contamination. The manner in which dry cleaning solvents escape from dry cleaning plants is, for all practical purposes, identical for chlorinated and petroleum hydrocarbon solvents and is related to one of the following events: the catastrophic failure of a component of the dry cleaning system, the improper installation, operation or maintenance of the dry cleaning equipment or a combination of all of these causes. Acceptable customs, codes and regulations can also dictate what is authorized for operation of a dry cleaning facility in a particular community, geographic area during a particular time frame. Environmental litigation dealing with the origin of a solvent release from dry cleaners tends to focus on the design and manufacture of dry cleaning industry machines such as washers, washer extractors, tumblers, solvent filters, water separators, stills and spotting boards. A thorough analysis of the daily operations of dry cleaners often reveals that poor maintenance, failure to follow the manufacturer's instructions and the actions of the operator are the most likely causes of soil and groundwater pollution. In order to forensically evaluate the most probable origins of a solvent release and to examine issues regarding liability, a thorough understanding of the history of dry cleaning and a detailed analysis of the operation and maintenance of the dry cleaning equipment are necessary. The discovery of solvent plumes in the vicinity of dry cleaning plants may suggest that the solvent source is the dry cleaning plant; however, the presence of these plumes does not necessarily indicate that the dry cleaning equipment was defectively designed or manufactured. A thorough review of the type of equipment used over the life of the dry cleaning plant and verifiable solvent mileage records frequently indicates that operators of the plant have disposed of solvent and contaminated solids into the municipal sewer or on ground surfaces.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

Malathion-induced sublethal toxicity on the intestine of cricket frog (Fejervarya limnocharis)

The effect of malathion [diethyl(dimethoxythiophosphorylthio)succinate] at sublethal concentration (0.006 ppm) on intestinal parameters of cricket frog (Fejervarya limnocharis) was studied for 24 hrs to 240 hrs of exposure and remarkable histopathological alterations were observed. The study on intestinal parameters revealed acute pathological conditions in the intestinal wall. The toxic effect became evident as the cytoplasm of the cells disintegrated and the cells became empty and vacuolated. The cell membranes were also ruptured. Degenerative changes of the absorptive surface (villi) of the intestine in the different periods of exposure were pronounced. Severe atrophic nature (necrotic mucosa) of the intestine began from 48 hrs onwards to 96 hrs of exposure.     

Radionuclides in deer and elk from Los Alamos national laboratory and the doses to humans from the ingestion of muscle and bone

Abstract

This paper summarizes radionuclide concentrations (³H, ⁹⁰Sr, ¹³⁷Cs, ²³⁸Pu, ^239,240Pu, ²⁴¹Am, and ^totU) in muscle and bone tissue of mule deer (Odocoileus hemionus) and Rocky Mountain elk (Cervus elaphus) collected from Los Alamos National Laboratory (LANL), Los Alamos, New Mexico, lands from 1991 through 1998. Also, the committed effective dose equivalent (CEDE) and the risk of excess cancer fatalities (RECF) to people who ingest muscle and bone from deer and elk collected from LANL lands were estimated. Most radionuclide concentrations in muscle and bone from individual deer (n = 11) and elk (n = 22) collected from LANL lands were either at less than detectable quantities (where the analytical result was smaller than two counting uncertainties) and/or within upper (95%) level background (BG) concentrations. As a group, most radionuclides in muscle and bone of deer and elk from LANL lands were not significantly higher (p<0.10) than in similar tissues from deer (n = 3) and elk (n = 7) collected from BG locations. Also, elk that had been radio collared and tracked for two years and spent an average time of 50% on LANL lands were not significantly different in most radionuclides from road kill elk that have been collected as part of the environmental surveillance program. Overall, the upper (95%) level net CEDEs (the CEDE plus two sigma for each radioisotope minus background) at the most conservative ingestion rate (50 lbs of muscle and 13 lbs of bone) were as follows: deer muscle = 0.22 mrem y^‐1 (2.2 μSv y^‐1), deer bone = 3.8 mrem y^‐1 (38 μSv y^‐1), elk muscle = 0.12 mrem y^‐1 (1.2 μSv y^‐1), and elk bone = 1.7 mrem y^‐1 (17 μSv y^‐1). All CEDEs were far below the International Commission on Radiological Protection guideline of 100 mrem y^‐1 (1000 μSv y^‐1), and the highest muscle plus bone net CEDE corresponded to a RECF of 2E‐06, which is far below the Environmental Protection Agency upper level guideline of 1E‐04.     

Nitrogen leaching and acidification during 19 years of NH₄NO₃ additions to a coniferous-forested catchment at Gårdsjön, Sweden (NITREX)

The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-catchment experiment with N addition at Gårdsjön, Sweden, to investigate the risk of N saturation. We have added 41 kg N ha⁻¹ yr⁻¹ as NH₄NO₃ to the ambient 9 kg N ha⁻¹ yr⁻¹ in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO₃ in runoff partially offset the decreasing concentrations of SO₄ and slowed ecosystem recovery from acid deposition. From 1990-2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42-59 g g⁻¹.     

Leaching of seven pesticides currently used in cotton crop in Mato Grosso State—Brazil

This study aimed to evaluate the leaching of pesticides and the applicability of the Attenuation Factor (AF) Model to predict their leaching. The leaching of carbofuran, carbendazim, diuron, metolachlor, α and β endosulfan and chlorpyrifos was studied in an Oxisol using a field experiment lysimeter located in Dom Aquino – Mato Grosso. The samples of percolated water were collected by rain event and analyzed. Chemical and physical soil attributes were determined before pesticide application to the plots. The results showed that carbofuran was the pesticide that presented a higher leaching rate in the studied soil, so was the one representing the highest contamination potential. From the total carbofuran applied in the soil surface, around 6 % leached below 50 cm. The other pesticides showed lower mobility in the studied soil. The calculated values to AF were 7.06E-12 (carbendazim), 5.08E-03 (carbofuran), 3.12E-17 (diuron), 6.66E-345 (α-endosulfan), 1.47E-162 (β-endosulfan), 1.50E-06 (metolachlor), 3.51E-155 (chlorpyrifos). AF Model was useful to classify the pesticides' potential for contamination; however, that model underestimated pesticide leaching.     

Endosulfan in China 2—emissions and residues

Background, aim, and scope  Endosulfan is one of the organochlorine pesticides (OCPs) and also a candidate to be included in a group of new persistent organic pollutants (UNEP 2007). The first national endosulfan usage inventories in China with 1/4° longitude by 1/6° latitude resolution has been reported in an accompanying paper. In the second part of the paper, we compiled the gridded historical emissions and soil residues of endosulfan in China from the usage inventories. Based on the residue/emission data, gridded concentrations of endosulfan in Chinese soil and air have been calculated. These inventories will provide valuable data for the further study of endosulfan. Methods  Emission and residue of endosulfan were calculated from endosulfan usage by using a simplified gridded pesticide emission and residue model—SGPERM, which is an integrated modeling system combining mathematical model, database management system, and geographic information system. By using the emission and residue inventories, annual air and soil concentrations of endosulfan in each cell were determined. Results and discussion  Historical gridded emission and residue inventories of α- and β-endosulfan in agricultural soil in China with 1/4° longitude by 1/6° latitude resolution have been created. Total emissions were around 10,800 t, with α-endosulfan at 7,400 t and β-endosulfan at 3,400 t from 1994 to 2004. The highest residues were 140 t for α-endosulfan and 390 t for β-endosulfan, and the lowest residues were 0.7 t for α-endosulfan and 170 t for β-endosulfan in 2004 in Chinese agricultural soil where endosulfan was applied. Based on the emission and residue inventories, concentrations of α- and β-endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell. We have estimated annual averaged air concentrations and the annual minimum and maximum soil concentrations across China. The real concentrations will be different from season to season. Although our model does not consider the transport of the insecticide in the atmosphere, which could be very important in some areas during some special time, the estimated concentrations of endosulfan in Chinese air and soil derived from the endosulfan emission and residue inventories are in general consistent with the published monitoring data. Conclusions  To our knowledge, this work is the first inventory of this kind for endosulfan published on a national scale. Concentrations of the chemical in Chinese air and agricultural surface soil were calculated for each grid cell. Results show that the estimated concentrations of endosulfan in Chinese air and soil agree reasonably well with the monitoring data in general. Recommendations and perspectives  The gridded endosulfan emission/residue inventories and also the air and soil concentration inventories created in this study will be updated upon availability of new information, including usage and monitoring data. The establishment of these inventories for the OCP is important for both scientific communities and policy makers.