Changes in TcpA gene frequency explain 2,4,6-trichlorophenol degradation in mesocosms

Soils are often polluted by chlorophenols in timber production areas in the northern hemisphere. The tcpA gene encodes the first step of 2,4,6-trichlorophenol (246-TCP) degradation. We tested tcpA gene frequency in three natural pristine soils with different 246-TCP degradation capacity. Gene tcpA frequency increased more in spiked than non-spiked 10-L pails containing coniferous humus soil with high degradation capacity, in contrast to soils where degradation was slower. As the soil in each mesocosm originated from a spatially separate field plot, changes in tcpA gene frequency affected 246-TCP degradation over a range of soil origins. This indicates that the abundance of and changes in tcpA gene frequency could be utilized in estimating the efficacy of natural attenuation and biostimulation treatments in controlled conditions.     

The electron density distribution in pyridinium and bipyridylium compounds and its relevance to their adsorption by expanding lattice clays

Abstract

Charge distributions in 1, 1'‐ethylene‐2, 2'‐bipyridylium (diquat), 1,1'‐dimethyl‐4,4'‐bipyridylium (paraquat) and 1‐methylpyridinium organocations were calculated by a Complete Neglect of Differential Overlap semi‐empirical quantum mechanical procedure. The data show that the positive charges in the organocations are distributed around the molecules and are greatest in the positions ortho and para to the heterocyclic nitrogen atoms. Earlier interpretations of the mechanisms of adsorption of paraquat and diquat by soils and clays assumed that the charges were located in the heterocyclic nitrogen atoms. Here some consideration is given to the influence of the charge delocalizations on the processes of adsorption by montmorillonite and vermiculite clay preparations.     

Natural Products: Seasonal Variation in Trichome Counts and Contents in Lycopersicum hirsutum f. glabratum

Abstract

Wild tomato leaves possess a pest-resistance mechanism in their glandular trichomes and the exudates they produce. Type IV and VI glandular trichomes on the leaves of five wild tomato accessions of Lycopersicum hirsutum f. glabratum (PI 126449, PI 134417, PI 134418, PI 251304, and LA 407) grown under greenhouse conditions were counted. Major chemical compounds from glandular leaf trichomes of the accessions tested were extracted, purified, and quantified at different periods during the growing seasons by gas chromatography (GC) and mass spectrometry (GC/MS). The toxicity of two methylketones (2-undecanone and 2-tridecanone), the major constituents of the accessions tested, to adults of the sweetpotato whitefly, Bemisia tabaci (Gennadius) and fourth instar larvae of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), was determined using no-choice bioassays. 2-undecanone caused 80% mortality of the fourth instar larvae of the CPB at the highest concentration tested (100 mg 2-undecanone mL^{? 1} of acetone) while 2-tridecanone caused 72% mortality of whiteflies at 20 mg 2-tridecanone mL^{? 1} of 65% ethanol. The concentration of 2-undecanone and 2-tridecanone on the leaves of each of the five accessions of L. hirsutum f. glabratum and the mass spectra of 2-undecanone and 2-tridecanone are presented. Overall, the concentration of 2-undecanone on the leaves was significantly higher than 2-tridecanone. Concentration of the two methylketones varied among accessions and sampling season. Plants produced the highest concentration of 2-undecanone during the month of August. On average, each plant of accession PI 251304 provided 354 g fresh leaves (averaging about 52,353 cm² exposed leaf surface area) and produced 32.5 and 8.7 mg of 2-undecanone and 2-tridecanone, respectively. L. hirsutum f. glabratum accessions may become a valuable source of natural products, which could minimize reliance on synthetic pesticides.     

Impact of different public E&P policies on natural gas reserves and production in Pakistan

Low wellhead domestic gas prices over the past few years have led to the beginning of a shortage in natural gas reserves and production in Pakistan. Gas demand steadily rises in all sectors for being an economical fuel as compare to substitutes. In the view of foregoing consumption trend, the demand for gas is expected to grow with a higher pace during the 2010s. On the contrary, indigenous gas reserves are running out and cannot keep up with the demand. This paper examines the extent of upstream activities in different petroleum policy regimes. The wellhead price for indigenous gas is compared with the prices of alternatives (for example, gas import prices). In order to put the problem in perspective, the relationship between wellhead gas price and cumulative gas reserves in Pakistan are analyzed and we find that the looming gas shortage can be ameliorated in the short-run and eliminated in the long-run through incentivized wellhead price. To put it briefly, the idea is mooted to first take advantage of huge domestic reserves to ensure competitive consumer prices for gas. The findings are applicable to several other economies with under-developed natural resources.     

Risk assessment of xenoestrogens in a typical domestic sewage-holding lake in China

Release of domestic sewage leads to accumulation of xenoestrogens in holding waters, especially in closed or semi-enclosed waters such as lakes. In the study, the occurrence, distribution, estrogenic activity and risk of eight xenoestreogens were evaluated in Lake Donghu, China. Nonylphenol (NP), octylphenol (OP), and bisphenol A (BPA) were identified as the main xenoestrogens ranging from tens of ng L⁻¹ (in the surface water) or ng g⁻¹ dw (in the suspended particles and sediment) to tens of μg L⁻¹ or μg g⁻¹ dw. The sum of 17β-estradiol equivalents (∑EEQs) ranged from 0.32 to 45.02 ng L⁻¹ in the surface water, 0.53 to 71.86 ng g⁻¹ dw in the suspended particles, and 0.09 to 24.73 ng g⁻¹ dw in the sediment. Diethylstilbestrol (DES) was determined as the main contributor to ∑EEQs followed by NP. The risk assessment showed a higher risk in the surface water than in the suspended particles and sediment in such domestic sewage-holding lake.     

Impact of carbon,oxygen and sulfur content of microscale zerovalent iron particles on its reactivity towards chlorinated aliphatic hydrocarbons

Zerovalent iron (ZVI) abiotically degrades several chlorinated aliphatic hydrocarbons (CAHs) via reductive dechlorination, which offers perspectives for in situ groundwater remediation applications. The difference in reactivity between ZVI particles is often linked with their specific surface area. However, other parameters may influence the reactivity as well. Earlier, we reported for a set of microscale zerovalent iron (mZVI) particles the disappearance kinetic of different CAHs which were collected under consistent experimental conditions. In the present study, these kinetic data were correlated with the carbon, oxygen and sulfur content of mZVI particles. It was confirmed that not only the specific surface area affects the disappearance kinetic of CAHs, but also the chemical composition of the mZVI particles. The chemical composition, in addition, influences CAHs removal mechanism inducing sorption onto mZVI particles instead of dechlorination. Generally, high disappearance kinetic of CAHs was observed for particles containing less oxygen. A high carbon content, on the other hand, induced nonreactive sorption of the contaminants on the mZVI particles. To obtain efficient remediation of CAHs by mZVI particles, this study suggested that the carbon and oxygen content should not exceed 0.5% and 1% respectively. Finally, the efficiency of the mZVI particles may be improved to some extent by enriching them with sulfur. However, the impact of sulfur content on the reactivity of mZVI particles is less pronounced than that of the carbon and oxygen content.     

SO2 inhalation causes synaptic injury in rat hippocampus via its derivatives in vivo

SO₂ remains a common air pollutant, almost half of the world’s population uses coal and biomass fuels for domestic energy. Limited evidence suggests that exposure to SO₂ may be associated with neurotoxicity and increased risk of hospitalization and mortality of many brain disorders. However, our understanding of the mechanisms by which SO₂ causes harmful insults on neurons remains elusive. To explore the molecular mechanism of SO₂-induced neurotoxic effects in hippocampal neurons, we evaluated the synaptic plasticity in rat hippocampus after exposure to SO₂ at various concentrations (3.5 and 7 mg m⁻³, 6 h d⁻¹, for 90 d) in vivo, and in primary cultured hippocampal neurons (DIV7 and DIV14) after the treatment of SO₂ derivatives in vitro. The results showed that SYP, PSD-95, NR-2B, p-ERK1/2 and p-CREB were consistently inhibited by SO₂/SO₂ derivatives in more mature hippocampal neurons in vivo and in vitro, while the effects were opposite in young hippocampal neurons. Our results indicated that in young neurons, SO₂ exposure produced neuronal insult is similar to ischemic injury; while in more mature neurons, SO₂ exposure induced synaptic dysfunctions might participate in cognitive impairment. The results implied that SO₂ inhalation could cause different neuronal injury during brain development, and suggested that the molecular mechanisms might be involved in the changes of synaptic plasticity.     

天然和CPB改性沸石对Hg^2＋的吸附特征

通过静态实验研究溴代十六烷基吡啶（CPB）改性沸石和天然沸石对废水中Hg^2＋的吸附特性,探讨了吸附动力学、吸附平衡和吸附热力学机制。研究表明：Langmuir方程能较好地描述2种沸石对Hg^2＋的吸附,CPB改性沸石对Hg^2＋的吸附率得到显著提高。实验条件下,改性沸石对Hg^2＋的吸附率从67．5％提高到98．9％,吸附容量从0．521mg／g提高到3．07mg／g。利用准一级动力学方程、假二级动力学方程、颗粒内扩散模型和Elovich方程分别对动力学过程进行拟合,发现2种沸石对Hg^2＋的吸附均满足假二级动力学方程,且离子的颗粒内扩散对整个吸附过程有影响。动力学拟合、D-R方程拟合和热力学研究综合表明：2种沸石对Hg^2＋的吸附既存在化学吸附又存在物理吸附,吸附吉布斯自由能变（△G^0）、焓变（△H^0）、熵变（△S^0）均小于0,反应为自发的放热反应,低温有利于吸附的进行。     

SO2在碳钢初期大气腐蚀中的作用

通过自建的模拟大气腐蚀系统,借助金相显微镜、扫描电镜(SEM/EDX)、X-射线衍射(XRD)和x-射线光电子能谱(XPS),研究了SO2对碳钢初期大气腐蚀行为的影响,并进一步用原子力显微镜从更微观的角度观察了在SO2环境中初期阶段腐蚀形貌变化.研究结果表明:在SO2污染大气环境中,随SO2浓度的升高碳钢腐蚀加快.在体积分数为5×10(-6)SO2的大气环境中,碳钢和耐候钢表面腐蚀主要以条状物生长,随着SO2浓度的升高,腐蚀产物的形貌发生改变,在体积分数为5×10(-5)SO2的大气环境中,条状锈和胞状锈同时生长.在锈层中S元素以FeSO4·4H2O的形式存在,腐蚀产物中还有γ-FeOOH.SO2在初期阶段加速了碳钢的腐蚀,降低了碳钢的耐蚀性.