云南省凤眼莲入侵现状及其引种得失分析

大规模外来种的引入是生物多样性下降主要原因之一,外来种的入侵已经引起了一系列的生态、经济、社会问题。从云南省凤眼莲入侵的现状,分析了入侵植物风眼莲引种的得失。对于风眼莲的控制及其治理主要有物理、化学以及生物方法,认为目前对风眼莲等入侵生物应采取综合治理的方法。同时引进植物外来种时,要对引进种的行为特性进行调查研究,注意其安全性。     

Mass Balances of Mercury and Nitrogen in Burned and Unburned Forested Watersheds at Acadia National Park, Maine, USA

Precipitation and streamwater samples were collected from 16 November 1999 to 17 November 2000 in two watersheds at Acadia National Park, Maine, and analyzed for mercury (Hg) and dissolved inorganic nitrogen (DIN, nitrate plus ammonium). Cadillac Brook watershed burned in a 1947 fire that destroyed vegetation and soil organic matter. We hypothesized that Hg deposition would be higher at Hadlock Brook (the reference watershed, 10.2 μg/m²/year) than Cadillac (9.4 μg/m²/year) because of the greater scavenging efficiency of the softwood vegetation in Hadlock. We also hypothesized the Hg and DIN export from Cadillac Brook would be lower than Hadlock Brook because of elemental volatilization during the fire, along with subsequently lower rates of atmospheric deposition in a watershed with abundant bare soil and bedrock, and regenerating vegetation. Consistent with these hypotheses, Hg export was lower from Cadillac Brook watershed (0.4 μg/m²/year) than from Hadlock Brook watershed (1.3 μg/m²/year). DIN export from Cadillac Brook (11.5 eq/ha/year) was lower than Hadlock Brook (92.5 eq/ha/year). These data show that ∼50 years following a wildfire there was lower atmospheric deposition due to changes in forest species composition, lower soil pools, and greater ecosystem retention for both Hg and DIN.     

金融科技与企业绿色转型——影响特征、作用机制与空间溢出效应识别

数字经济时代下的金融科技,是金融服务实体经济高质量发展的新业态新模式。本文基于中国上市企业2011—2021年数据集,对金融科技和企业绿色转型之间的影响和机制进行实证检验。实证结果发现,金融科技能够有效赋能企业绿色转型。特别地,金融科技对于高科技企业、非国有企业和重污染企业的绿色转型驱动力更为突出。机制识别检验发现,金融科技能够缓解财务困境、平滑企业风险与增强绿色创新活力,这些都有助于企业绿色转型实践的深度开展。进一步研究发现,金融科技具有强烈的地理扩散溢出效应,并形成较为显著的“本地—外地”金融科技协同效果,对企业绿色转型产生了可叠加的积极影响。本项研究能够为理解金融科技发展,促进实体经济绿色转型提供新的思路借鉴。     

铀和铅对枯草杆菌毒性的研究

采用3种方法研究了铀和铅对枯草杆菌的毒性:(1)试纸法测抑菌圈的直径;(2)血球计数板测细菌菌数;(3)高倍显微镜下观察细菌形态和密度的变化.实验考察铀和铅的质量浓度为1～2 000 mg/L.结果表明:铀和铅对枯草杆菌的生长繁殖有显著影响;铀和铅对枯草杆菌的最大无作用剂量均小于1 mg/L;铀对枯草杆菌的致死质量浓度为500 mg/L,铅对枯草杆菌的致死质量浓度为 1 000 mg/L.同时,对以上3种方法进行了比较,确定了其各自的应用范围,为重金属对微生物毒性研究方法的选择提供了参考.     

碳市场对能源结构低碳转型的影响及作用路径

选取中国2000～2018年30个省市的面板数据,构建了能源消费结构低碳化指数,基于多期双重差分、三重差分等方法实证检验碳交易政策与能源消费结构低碳转型之间的关系及异质性影响,并进一步利用多重中介效应模型探讨碳交易政策推动地区能源消费结构低碳转型的作用路径.结果表明:碳交易政策可以显著提升地区能源消费结构低碳化水平且作用效果逐年增强.从作用路径看,“四大效应”激励作用彰显,作用效果由大到小依次为结构优化效应、行为驱动效应、生态创新效应和环保支出效应;从异质性影响看,GDP增速较慢地区的政策实施加快了能源消费结构低碳转型,影响明显高于GDP增速较快地区;碳交易政策对东部地区的正向推动效应显著,对中西部地区无明显促进作用.     

垃圾按量收费政策效应的实证研究

垃圾按量收费是管制城市垃圾的最直接的环境经济政策。它根据垃圾排放量向居民征收（不同的）费用。从而实现有效率的资源配置。本文通过对城市居民的问卷调查．采用描述性统计分析、方差分析、回归分析等方法。对垃圾按量收费的政策效应进行实证研究。以期为中国垃圾按量收费政策的制定和实施提供借鉴。我们的研究旨在解决两个问题：一是测度垃圾按量收费政策的总体效应;二是考察垃圾按量收费政策对不同居民的效应差异。结果表明。从总体上看．超过半数的居民认为垃圾按量收费更合理,但多数人还是更喜欢每月固定收费;从对不同居民的具体分析看,中高收入者倾向认为垃圾按量收费更合理,年长者更喜欢每月固定收费。实行垃圾按量收费后．年轻者更可能减少倒垃圾的量．但也更可能偷偷倒垃圾。     

小麦异源细胞质遗传效应的比较研究

本文以稳定的同核异质异核杂种小麦为材料,对小麦属和山羊草属的细胞质遗传效应进行了比较研究,分析了异源细胞质遗传疚的特点,并初步筛选出了一批在小麦雄性不育性应用中以及在小麦核质杂种优势利用中有价值的细胞质材料。     

Behavior of the organophosphorus insecticide fenitrothion in stored faba beans and its biological effects towards experimental animals

Sound whole-seed faba beans were treated with (methyl-¹⁴C) fenitrothion [O, O-dimethyl-O-(3-methyl-4-nitrophenyl) phosphorothioate] at 5 and 10 mg insecticide/kg seeds, a dose normally used in practice. During the 30 weeks of storage period, the penetration and distribution of insecticide residues were studied. The amount of surface residues, internal residues and bound insecticide residues was estimated. Surface residues were found to decrease with the increase in time of storage, whereas internal residues showed a gradual increase with time apparently not dose dependent. Grain-bound residues increased with time and reached to its maximum (14–18%) after 24 weeks of storage. Chromatographic analysis of the internal extracts revealed the presence of the parent compound together with three main metabolites which were found in both free and conjugated form. Feeding mice for 90 days with a diet mixed with total internal fenitrothion residues in stored faba beans led to a reduction in body weight gain, and an appreciable decrease in cholinesterase activity of 32% for plasma and 15% for red blood cells (RBC_S) after two months of experiment. Also, a significant decrease was showed in both total protein and albumin concentration at the end of feeding period (90 days). Liver and kidney function, as well as lipid profile of treated mice significantly increased at the end of feeding period. After a one-month recovery period, all the examined blood parameters returned to about the control values except blood urea and serum triglyceride.     

The effects of ammonium sulphate and urea upon egg hatching and miracidial survival of Schistosoma mansoni

Abstract

The effects of various concentrations of ammonium sulphate and urea on egg hatching and miracidial survival of S. mansoni were tested in order to determine if the use of these fertilizers in the ricelands of the Republic of Cameroon could affect the transmission of schistosomiasis. Results indicate that hatching of eggs and survival of miracidia varied with concentrations of tested chemicals and times of exposure. Exposure of S. mansoni eggs to 0.20%‐1.00% ammonium sulphate or to 0.50%‐4.00% urea reduced their ability to hatch and produce miracidia. A chemical concentration of 1.00% ammonium sulphate or 4.00% urea was found to be sufficient to produce complete inhibition of hatching. High concentrations of both chemicals not only inhibited miracidial emmergence but also may be ovocidal. Results obtained from miracidial survival tests indicated that LC₅, LC₅₀ and LC₉₅ values for ammonium sulphate were 0.07%, 0.80% and 10.61% after 2 hours of exposure; 0.03%, 0.16% and 0.90% after 4 hours of exposure; and 0.30%, 0.20% and 0.40% after 6 hours of exposure respectively. Similar statistical analyses revealed that the LC₅, LC₅₀ and LC₉₅ values for urea were 0.22%, 1.90% and 16.25% after 2 hours of exposure; 0.28%, 0.57% and 1.14% after 4 hours of exposure; and 0.13%, 0.27% and 0.57%” after 6 hours of exposure respectively. Although the two fertilizers exerted some adverse effects on S. mansoni eggs and miracidia at relatively high concentrations, neither of them was found to be of practical value. Ammonium sulphate and urea concentrations effective in killing S. mansoni eggs and miracidia were about one to two orders of magnitude greater than the actual field application rates.     

Investigation of hit-and-run crash occurrence and severity using real-time loop detector data and hierarchical Bayesian binary logit model with random effects

Objective: Most of the extensive research dedicated to identifying the influential factors of hit-and-run (HR) crashes has utilized typical maximum likelihood estimation binary logit models, and none have employed real-time traffic data. To fill this gap, this study focused on investigating factors contributing to HR crashes, as well as the severity levels of HR.

Methods: This study analyzed 4-year crash and real-time loop detector data by employing hierarchical Bayesian models with random effects within a sequential logit structure. In addition to evaluation of the impact of random effects on model fitness and complexity, the prediction capability of the models was examined. Stepwise incremental sensitivity and specificity were calculated and receiver operating characteristic (ROC) curves were utilized to graphically illustrate the predictive performance of the model.

Results: Among the real-time flow variables, the average occupancy and speed from the upstream detector were observed to be positively correlated with HR crash possibility. The average upstream speed and speed difference between upstream and downstream speeds were correlated with the occurrence of severe HR crashes. In addition to real-time factors, other variables found influential for HR and severe HR crashes were length of segment, adverse weather conditions, dark lighting conditions with malfunctioning street lights, driving under the influence of alcohol, width of inner shoulder, and nighttime.

Conclusions: This study suggests the potential traffic conditions of HR and severe HR occurrence, which refer to relatively congested upstream traffic conditions with high upstream speed and significant speed deviations on long segments. The above findings suggest that traffic enforcement should be directed toward mitigating risky driving under the aforementioned traffic conditions. Moreover, enforcement agencies may employ alcohol checkpoints to counter driving under the influence (DUI) at night. With regard to engineering improvements, wider inner shoulders may be constructed to potentially reduce HR cases and street lights should be installed and maintained in working condition to make roads less prone to such crashes.