Combined effects of nitrogen addition and organic matter manipulation on soil respiration in a Chinese pine forest

The response of soil respiration (Rs) to nitrogen (N) addition is one of the uncertainties in modelling ecosystem carbon (C). We reported on a long-term nitrogen (N) addition experiment using urea (CO(NH₂)₂) fertilizer in which Rs was continuously measured after N addition during the growing season in a Chinese pine forest. Four levels of N addition, i.e. no added N (N0: 0 g N m⁻² year⁻¹), low-N (N1: 5 g N m⁻² year⁻¹), medium-N (N2: 10 g N m⁻² year⁻¹), and high-N (N3: 15 g N m⁻² year⁻¹), and three organic matter treatments, i.e. both aboveground litter and belowground root removal (LRE), only aboveground litter removal (LE), and intact soil (CK), were examined. The Rs was measured continuously for 3 days following each N addition application and was measured approximately 3–5 times during the rest of each month from July to October 2012. N addition inhibited microbial heterotrophic respiration by suppressing soil microbial biomass, but stimulated root respiration and CO₂ release from litter decomposition by increasing either root biomass or microbial biomass. When litter and/or root were removed, the “priming” effect of N addition on the Rs disappeared more quickly than intact soil. This is likely to provide a point of view for why Rs varies so much in response to exogenous N and also has implications for future determination of sampling interval of Rs measurement.

     

CaO2及H2O2类Fenton降解土壤石油烃污染

采用H_2O_2/Fe(Ⅲ)/柠檬酸类Fenton体系和CaO_2/Fe(Ⅲ)/柠檬酸类Fenton体系修复土壤石油污染,考察了氧化剂种类、氧化剂投加量、 Fe(Ⅲ)浓度和柠檬酸浓度对柴油降解效果的影响,并进一步研究比较了CaO_2/Fe(Ⅲ)/柠檬酸和H_2O_2/Fe(Ⅲ)/柠檬酸2种修复方式对土壤原著微生物群落变化及豌豆植株生长所带来的生态毒性效应。单因素实验结果表明:在其他条件相同的情况下,CaO_2类Fenton降解柴油效果优于H_2O_2类Fenton降解效果;柴油降解率随着氧化剂投加量、Fe(Ⅲ)和柠檬酸浓度的增大呈现先增后降的趋势。当CaO_2浓度为166.67 mmol·L~(-1)、Fe(Ⅲ)浓度为27.78 mmol·L~(-1)、柠檬酸浓度为27.78 mmol·L~(-1)时,反应24 h后,土壤中柴油降解率达到44.14%。生态毒性实验表明:CaO_2类Fenton处理后土壤微生物群落的丰富度和多样性指数均有所提高,H_2O_2类Fenton处理后均有所降低,2种处理方式均在不同程度上改变了土壤微生物群落的优势菌门构成;CaO_2及H_2O_2类Fenton处理均抑制了豌豆植株的生长,发芽率、植株干重、株高、叶绿素含量等测试指标均下降,其中H_2O_2类Fenton处理的抑制效果更为明显。进一步分析可知,CaO_2类Fenton处理技术比H_2O_2类Fenton处理技术更适用于石油污染土壤修复。     

响应面法优化石油降解菌性能的研究

从延长油田石油污染土壤中筛选出4株能以原油为唯一碳源生长的细菌单菌株,鉴定其优势菌株YC-2为枯草芽孢杆菌;利用响应面法进行实验设计,选定培养温度、pH值、氮磷比以及盐度为影响因素,对原油含量为0.5%的培养基进行YC-2菌株降解工艺优化,得到了原油降解率与4种因素之间的非线性回归方程,确定了降解原油的最优工艺条件:培养温度28℃;pH值6.5,氮磷比5.2:1,盐度0.45%。在最优条件下,预测降解率为53.9%,实验验证值为52.5%,结果显示,建立的模型具有较高的精度。     

Trends and variations of pH and hardness in a typical semi-arid river in a monsoon climate region during 1985–2009

The rapid growth of urbanization and industrialization, along with dramatic climate change, has strongly influenced hydrochemical characteristics in recent decades in China and thus could cause the variation of pH and general total hardness of a river. To explore such variations and their potential influencing factors in a river of the monsoon climate region, we analyzed a long-term monitoring dataset of pH, SO₄ ^2?, NO_x, general total hardness (GH), Mg²⁺, Ca²⁺, and Cl^? in surface water and groundwater in the Luan River basin from 1985 to 2009. The nonparametric Seasonal Kendall trend test was used to test the long-term trends of pH and GH. Relationship between the affecting factors, pH and GH were discussed. Results showed that pH showed a decreasing trend and that GH had an increasing trend in the long-term. Seasonal variation of pH and GH was mainly due to the typical monsoon climate. Results of correlation analysis showed that the unit area usage amounts of chemical fertilizer, NO₃ ^?, and SO₄ ^2? were negatively correlated with pH in groundwater. In addition, mining activity affected GH spatial variation. Acid deposition, drought, and increasing the use of chemical fertilizers would contribute to the acidification trend, and mining activities would affect the spatial variation of GH. Variations of precipitation and runoff in semi-arid monsoon climate areas had significant influences on the pH and GH. Our findings implied that human activities played a critical role in river acidification in the semi-arid monsoon climate region of northern China.     

Combination of biochar amendment and phytoremediation for hydrocarbon removal in petroleum-contaminated soil

Remediation of soils contaminated with petroleum is a challenging task. Four different bioremediation strategies, including natural attenuation, biochar amendment, phytoremediation with ryegrass, and a combination of biochar and ryegrass, were investigated with greenhouse pot experiments over a 90-day period. The results showed that planting ryegrass in soil can significantly improve the removal rate of total petroleum hydrocarbons (TPHs) and the number of microorganisms. Within TPHs, the removal rate of total n-alkanes (45.83 %) was higher than that of polycyclic aromatic hydrocarbons (30.34 %). The amendment of biochar did not result in significant improvement of TPH removal. In contrast, it showed a clear negative impact on the growth of ryegrass and the removal of TPHs by ryegrass. The removal rate of TPHs was significantly lower after the amendment of biochar. The results indicated that planting ryegrass is an effective remediation strategy, while the amendment of biochar may not be suitable for the phytoremediation of soil contaminated with petroleum hydrocarbons.     

应用地累积指数评价鞍山市夏季PM2.5中元素的污染

2014年夏季在鞍山市的6个站点进行了PM2.5的样品采集,对其载带的15种元素进行了检测。通过地累积指数、相关分析和聚类分析等方法分析了鞍山市夏季PM2.5中15种元素的污染来源。结果表明:Ca、Zn、Pb、Ni和Cd这5种元素的质量分数在各站点之间存在较大的差异;地累积指数结果显示,Cd为极强污染程度,可能的来源是钢铁冶炼和刹车及轮胎磨损,Pb和Zn污染程度在强污染以上,Pb可能的主要人为来源是钢铁冶炼和窖炉煤的燃烧,Zn可能主要来自钢铁冶炼和机动车,Cu、Ni、Cr和Ca中到强污染以下;聚类分析将中度污染及以上元素分为Zn-Cd-Pb,Ni-Cu-Cr和Ca 3类,分别指示钢铁冶炼、机动车尾气及刹车、轮胎磨损,建筑尘;相关性分析显示,Cr与Ni、Cu可能来自同一污染源,Zn、Cd和Pb可能来自同一种源。     

裹包青贮提高玉米秸秆厌氧消化效率的实验研究

秸秆是重要的沼气工程原料,秸秆预处理对其后续厌氧消化效率影响巨大。采用田间裹包青贮方法,设计3因素正交实验,考察了秸秆含水率、压缩比和添加剂对玉米秸秆发酵时间和厌氧消化产沼气的影响。结果表明:秸秆经过裹包青贮,发酵总时间(total fermentation time,TFT)减少1~2 d,累积产气量达到总产气量的90%所用时间(TFT90%)减少了40%~50%,消化效率明显提高;秸秆含水率对产气效果有明显影响,随着含水率增加,单位总固体(total solid,TS)累计产气量(cumulative biogas yields per TS,CBYT)和沼气日产率(biogas yields rate average day,BYR)由高到低排序为:35%~40%,40%~45%,30%~35%;秸秆压缩比对产气效果有明显影响,随着压缩比的增加,其对CBY和BYR的效应由高到低排序为:185、143与138 kg/m3;添加剂类型对产气效果亦有明显影响,在不同添加剂处理下,其对CBYT和BYR的效应由高到低排序为:尿素处理>甲酸处理>无添加剂处理;正交实验极差分析表明,对CBYT和BYR的影响排序为:含水率﹥压缩比﹥添加剂,其田间裹包青贮进行厌氧发酵的优化组合为:青贮秸秆含水率为35%~40%,压缩比为185 kg/m3,添加剂为营养型,青贮20 d,CBYT和BYR达到最大,分别为646.57 mL/g和173.25 mL/(d·g)。     

热活化过硫酸钾降解呋虫胺

以新烟碱类杀虫剂呋虫胺为目标污染物,以过硫酸钾为氧化剂,研究不同热活化条件下过硫酸钾对呋虫胺降解率的影响。实验结果表明:呋虫胺的降解率与溶液中过硫酸钾的浓度成正比;随着温度的升高,呋虫胺的降解率也逐渐升高;虽然中性时呋虫胺的降解率稍高于酸性和碱性时的降解率,但pH的变化对呋虫胺的降解率影响不大;Cl-和HCO3-对反应的影响比较复杂,当溶液中的Cl-和HCO3-的浓度低于5 mmol/L时,均促进呋虫胺的降解,而浓度升高时则抑制呋虫胺的降解;通过添加自由基捕获剂发现,该反应体系中同时存在·SO4-和·OH,但起主要作用的是·SO4-。     

酸碱改性对活性焦烧结烟气脱硫性能的影响

选取一定目数范围的活性焦,用3种酸(HCl、H2SO4和HNO3)、3种碱(KOH、NaOH和NH3·H2O)和酸碱两步(HNO3和KOH)对其进行改性处理,对比这几种方法改性的活性焦对烧结烟气的脱硫性能,实验结果表明,20~40目范围的活性焦脱硫性能最好;HCl改性活性焦的脱硫性能基本无变化,HNO3改性后有促进作用但作用不大,H2SO4改性反而降低了活性焦的脱硫活性;KOH和NaOH溶液改性活性焦对其脱硫性能有很大的提升作用,其中KOH改性效果更好,NH3·H2O改性基本无影响;先KOH后HNO3两步改性的活性焦效果最佳,并且能维持一定时间100%的脱硫效率。     

一株铅镉抗性菌株的分离鉴定及其生物学特性

鉴定了从黑龙江扎龙湿地土壤中筛选出的一株抗铅镉的菌株,研究了其生物学特性和部分生理生化指标。利用16SrDNA序列分析鉴定其菌属,并且研究Pb2+、Cd2+、Pb2+/Cd2+、温度、pH、盐以及抗生素对菌株生长的影响。经鉴定,该菌株为阴沟肠杆菌属(Enterobacter cloacae)。该菌株对Pb2+的去除率和吸附率分别达到了70.34%和44.39%,对Cd2+的去除率和吸附率分别达到了40.54%和25.14%。该菌株最适生长温度为25℃,最适生长pH为7.0左右。此菌株对抗生素亚胺培南最敏感。随着盐、Pb2+、Cd2+、Pb2+/Cd2+混合浓度的升高,该菌株生长受到抑制。