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101.
Population Ecology - 相似文献
102.
《Chronobiology international》2013,30(2):405-422
Five field experiments were conducted in 1998 and 1999 in Minnesota to examine the influence of time of day efficacy of glyphosate [N-(phosphonomethyl)glycine] and glufosinate [2-amino-4-(hydroxymethyl-phosphinyl)butanoic acid] applications on the control of annual weeds. Each experiment was designed to be a randomized complete block with four replications using plot sizes of 3×9 m. Glyphosate and glufosinate were applied at rates of 0.421 kg ae/ha and 0.292 kg ai/ha, respectively, with and without an additional adjuvant that consisted of 20% nonionic surfactant and 80% ammonium sulfate. All treatments were applied with water at 94 L/ha. Times of day for the application of herbicide were 06:00h, 09:00h, 12:00h, 15:00h, 18:00h, 21:00h, and 24:00h. Efficacy was evaluated 14 d after application by visual ratings. At 14 d, a circadian response to each herbicide was found, with greatest annual weed control observed with an application occurring between 09:00h and 18:00h and significantly less weed control observed with an application at 06:00h, 21:00h, or 24:00h. The addition of an adjuvant to both herbicides increased overall efficacy, but did not overcome the rhythmic time of day effect. Results of the multiple regression analysis showed that after environmental temperature, time of day was the second most important predictor of percent weed kill. Thus, circadian timing of herbicide application significantly influenced weed control with both glyphosate and glufosinate. 相似文献
103.
Hair is often used as an index of environmental and industrial exposure to different metals. The interpretation of metal levels
in hair is difficult because of the risk of external contamination. The aim of this study was to define the degree of external
contamination of hair exposed in vitro to mercury vapor. Specimens of hair were exposed to concentration: 0.026, 0.21, and
2.7 mg Hg/m3 for 2–28 d. Mercury levels in hair increased during 28 d of exposure 2, 3 and 13, times, respectively, when compared to initial
values. Mercury levels in hair exposed to the first and second (but not third) concentration of mercury vapor attained a steady
state on the 21st d of exposure. The contamination of hair with mercury could not be removed by washing with water, solvent,
and detergent.
Hair may be used as an index of internal uptake of mercury provided that it was not externally exposed to mercury vapor. In
cases of occupational exposure to mercury vapor, hair could become a useful tool for monitoring exposures. 相似文献
104.
Sixty surface sediment samples from the intertidal zone of Yantai Sishili Bay (YSB) have been analyzed for arsenic (As) and mercury (Hg) to evaluate their contamination levels and potential ecological risks. Concentrations of As and Hg ranged from 7.01–23.56 and 0.00–0.01 μg g?1 in the dry season; during the wet season, the corresponding data were 1.44–6.17 and 0.00–0.02 μg g?1. The geoaccumulation index (Igeo) and potential ecological risk index (Eri) were used to conduct a pollution assessment. The results demonstrated that the intertidal zone of YSB has good sediment quality and that As and Hg are not likely to cause negative environmental impacts in the region. 相似文献
105.
The purpose of this study was to investigate the seasonal variations of mercury levels and human health risk in vegetables that were collected from farmland, home garden, and plastic greenhouse in summer and winter 2016 in Arid Oasis (Shihezi city), Xinjiang, Northwest China. The results showed that the levels of mercury in fresh vegetables were lower in winter (0.003–0.025 mg·kg?1) than in summer (0.001–0.035 mg·kg?1). Single factor pollution (P) in vegetables indicated that all vegetables were polluted in diverse levels. The exceeding rate in different vegetables was 0.00% to 88.89% in summer and 0.00% to 100% in winter compared with limits of pollutants in vegetables. The value of bio-concentration factor (BCF) revealed that the mercury absorption capacity of 10 species vegetables decreased in the following order: pea seedling > spinage > caraway > lettuces > pakchoi > celery > crowndaisy chrysanthemum > chives > spinach > shallot. The daily intake (DI) and target hazard quotient (THQ) of mercury for children (2–12 years), young adults (18–45 years), and quinquagenarian (>45 years) indicated that non-carcinogenic values were below the threshold values except one sampling sit from farmland around the industrial parks. Furthermore, the THQ of open field in summer was higher than plastic greenhouse in winter. Under the same pollution level, children had more non-carcinogenic risk than young adults and quinquagenarian. 相似文献
106.
A highly selective colorimetric and long‐wavelength fluorescent probe for the detection of Hg2+
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Jing Xu Zuokai Wang Caiyun Liu Zhenghe Xu Ning Wang Xin Cong Baocun Zhu 《Luminescence》2018,33(6):1122-1127
Currently, the fluorescent probe is an important method for detecting heavy metal ions, especially mercury ion (Hg2+), which is harmful to the health of humans and the environment due to its toxicity and extensive use. In this paper, we designed and synthesized a colorimetric and long‐wavelength fluorescent probe Hg‐P with high sensitivity and excellent selectivity, which could detect Hg2+ by the changes of visual color, fluorescence and absorption spectroscopy. With the addition of Hg2+ to probe Hg‐P solution, its color changed from yellow to pink, and showed a 171 nm red‐shifted absorption spectrum. Probe Hg‐P was used in real water and soil solution samples to detect Hg2+, and the result is satisfactory. Therefore, this new probe shows great value and application in detecting Hg2+ in the environment. 相似文献
107.
Nicholas V.C. Ralston Laura J. Raymond 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(11):2405-2416
Background
Methylmercury (CH3Hg+) toxicity is characterized by challenging conundrums: 1) “selenium (Se)-protective” effects, 2) undefined biochemical mechanism/s of toxicity, 3) brain-specific oxidative damage, 4) fetal vulnerability, and 5) its latency effect. The “protective effects of Se” against CH3Hg+ toxicity were first recognized >50?years ago, but awareness of Se's vital functions in the brain has transformed understanding of CH3Hg+ biochemical mechanisms. Mercury's affinity for Se is ~1 million times greater than its affinity for sulfur, revealing it as the primary target of CH3Hg+ toxicity.Scope of review
This focused review examined research literature regarding distinctive characteristics of CH3Hg+ toxicity to identify Se-dependent aspects of its biochemical mechanisms and effects.Conclusions
Research indicates that CH3Hg+ irreversibly inhibits the selenoenzymes that normally prevent/reverse oxidative damage in the brain. Unless supplemental Se is provided, consequences increase as CH3Hg+ approaches/exceeds equimolar stoichiometries with Se, thus forming HgSe and inducing a conditioned Se deficiency. As the biochemical target of CH3Hg+ toxicity, Se-physiology provides perspectives on the brain specificity of its oxidative damage, accentuated fetal vulnerability, and latency. This review reconsiders the concept that Se is a “tonic” that protects against CH3Hg+ toxicity and recognizes Se's role as Hg's molecular “target”. As the most potent intracellular nucleophile, the selenoenzyme inhibition paradigm has broad implications in toxicology, including resolution of conundrums of CH3Hg+ toxicity.General significance
Mercury-dependent sequestration of selenium and the irreversible inhibition of selenoenzymes, especially those required to prevent and reverse oxidative damage in the brain, are primarily responsible for the characteristic effects of mercury toxicity. 相似文献108.
汞是一种人体非必需且有毒的重金属元素,全球性的汞污染因对人类健康具有损害而备受社会关注。自然界中的汞绝大部分会通过江河径流和雨雪尘土的沉降而进入水生生态系统,每年进入水生生态系统的汞至少有10 000吨。水生昆虫作为重要的消费者生物存在于水生生态食物网中,是其重要的组成部分,在水生生态系统的物质循环中扮演着重要角色。本文介绍了近年来水生昆虫与汞之间的相关研究,重点总结了水生昆虫对汞的吸收和富集程度,分析了水生昆虫在汞的水-陆转移中的作用。研究数据表明,水生昆虫对汞的吸收程度与环境因素有关,并通过不同的途径转移到陆地生态系统中,对陆地生态系统上层食物链的生物存在一定的威胁,同时也需注意在对水生昆虫进行开发利用的同时,考虑汞是否超标的因素。 相似文献
109.
110.
汞对小麦种子活力和萌发代谢的影响 总被引:9,自引:1,他引:8
研究Hg^2+对小麦种子活力、幼苗生长、呼吸及淀粉酶、脂肪酶和转氨酶活力的影响。结果表明,Hg^2+能抑制种子萌发过程中淀粉酶、脂肪酶和转氨酶活性,抑制幼苗生长和呼吸代谢,降低种子活力,但浓度低时,在萌发初期有短暂促进作用。 相似文献