CHEMICAL COMPOSITION OF SOFTWATER FLORIDA LAKES AND THEIR SENSITIVITY TO ACID PRECIPITATION1

ABSTRACT: Based on alkalinity data for 596 lakes, 31 percent of Florida's 7300 lakes have < 100 μeq/l alkalinity and are sensitive to acid depostion. More than two-thirds of the lakes in 12 northern Florida counties fit this criterion. Increasing aluminum and decreasing nutrient and chlorophyll a concentrations were observed with decressing pH in a survery of 20 softwater lakes. Maximum measured aluminum values (100-150 μg/L) are below levels asociated with fish toxicity. Factor analysis showed that lake chemistry was related to three principal factors, representing three major processes: watershed weathering, acidification, and nutrient inputs. An acidification index defined as the difference between excess SO₄^2- and excess (Ca²⁺+Mg²⁺) accounted for 74 percent of the variance in lake pH. Comparison of historical (late 1950a) and present data for pH, alkalinity, and excess SO₄^2- indicated loss of alkalinity (>25 μeq/L) and increase in excess SO₄^2- (16-34 μeq/L) in several softwater lakes.     

ATMOSPHERIC CONTRIBUTIONS TO FOREST NUTRIENT CYCLING1

The atmosphere is a significant source of plant nutrients that partially replenishes losses due to timber harvesting. The relative importance of wet and dry deposition depends upon the specific nutrient and site. Nitrogen in bulk precipitation (wetfall and dryfall) is equivalent to at least 70 percent of the nitrogen incorporated annually in above-ground woody tissues of some temperate hardwood forests. Atmospheric sources of calcium and potassium supply between 20 and 40 percent of the nutrients sequestered in woody increments. Annual nutrient inputs in bulk precipitation can exceed removals associated with sawiog harvest over a rotation period. Atmospheric inputs of nitrogen are only slightly less than hydrologic losses immediately after timber harvesting. The deposition of nutrients is highly variable in both time and space; interpretations of nutrient inputs and forest management impacts require quantification of inputs for a variety of ecosystems over long periods of time.     

In situ monitoring of atmospheric nitrous acid based on multi-pumping flow system and liquid waveguide capillary cell

In the last four decades, various techniques including spectroscopic, wet chemical and mass spectrometric methods, have been developed and applied for the detection of ambient nitrous acid (HONO). We developed a HONO detection system based on long path photometry which consists of three independent modules i.e., sampling module, fluid propulsion module and detection module. In the propulsion module, solenoid pumps are applied. With solenoid pumps the pulsed flow can be computer controlled both in terms of pump stroke volume and pulse frequency, which enables the attainment of a very stable flow rate. In the detection module, a customized Liquid Waveguide Capillary Cell (LWCC) is used. The customized LWCC pre-sets the optical fiber in-coupling with the liquid wave guide, providing the option of fast startup and easy maintenance of the absorption photometry. In summer 2014, our system was deployed in a comprehensive campaign at a rural site in the North China Plain. More than one month of high quality HONO data spanning from the limit of detection to 5 ppb were collected. Intercomparison of our system with another established system from Forschungszentrum Juelich is presented and discussed. In conclusion, our instrument achieved a detection limit of 10 pptV within 2 min and a measurement uncertainty of 7%, which is well suited for investigation of the HONO budget from urban to rural conditions in China.     

湛江东海岛海雾雾水化学特征的对比分析

利用2010年和2011年在广东省湛江市东海岛海雾外场观测试验中获得的雾水样本和雾滴谱资料,对南海沿岸海雾化学特性进行研究.结果表明:2010年雾水的p H和电导率(EC)平均值分别为5.20和1884μS·cm-1,2011年的p H和EC平均值分别为3.34和505μS·cm-1.2011年雾水酸性变强的原因主要考虑到酸性物质比重增加.海洋源离子Cl-和Na+的离子浓度很高;SO_2-4和NO-3具有同源性,人为污染的贡献明显.2010和2011年总离子浓度(TIC)的平均值分别为38260μeq·L~(-1)和5600μeq·L~(-1),而实际大气中离子负荷量相差不大,主要是由于2011年观测地点海拔高度的升高会降低湍流因子的影响,减少粒径较大雾滴的沉降,从而促使液态水含量增加,在大气中污染物质浓度变化不大的情况下,离子浓度下降.     

Observation of the nighttime nitrate radical in Hefei, China

Observation of nighttime nitrate radical (NO3) was performed by using long path differential optical absorption spectroscopy (LP-DOAS), on the outskirts of Hefei, China. The time series of NO3 and supporting parameters were simultaneously measured for a week (31 May-7 June 2006). The results indicated that the average concentration of NO3 was 15.6 pptv with an average lifetimes of 96 s, whereas, NO3 production rates varied from 8×105/(cm3·s)to 2.98×107/（cm3·s）. Furthermore, the calculated N2O5 concentration averaged at 380 pptv. Analysis of data indicated that direct sinks were probably dominating the NO3 loss process during this campaign. Finally, the results were compared with other campaigns in the boundary layer.     

浸渍活性炭脱除含硫气体研究进展

介绍了浸渍活性炭脱除含硫气体机理的研究进展,归纳了炭表面化学环境,金属离子及水对转化途径和反应机理的影响,对进气组成和温度、压力、空速等操作条件对脱硫效率的影响进行了讨论,举例说明了浸溃活性炭脱硫应用情况,分析了浸渍活性炭失活原因,对再生方法进行了简要总结。     

水质转化的现代科学与技术：兼谈环境水化学实验室的科研方向

本文综述了当前环境水化学的发展趋势及其中苦干部分的研究动态与方向，例如：化学形态分布、酸化与风化、表面络合、沉积物质量评价、生态毒理、水陆交错带、水处理中的絮凝、膜分离、化学氧化、生物氧化和水质模式。离作者的若干观点及对环境水化学实验室近期研究方向的一些看法。     

Antioxidant alteration ofGlycine max (Fabaceae) defensive chemistry: Analogy to herbivory elicitation

Summary The water-soluble antioxidant, L-ascorbic acid (vitamin C), proved elicitory to alterable anti-herbivory inGlycine max againstTrichoplusia ni larvae. Elicitation by vitamin C was influenced especially by dose, time after elicitation and space in the plant. Results allow an analogy between antioxidant and herbivory elicitation. Elicitation apparently involves a sulfhydryl-protein-dependent redox mechanism which can be significantly affected by antioxidants. Findings would also support a proposed common redox-based mechanism, involving the plasma membrane, for communication between plant and animal cells and their environments.     

大气污染化学研究概况

本文综述了大气污染化学研究在国内外的发展概况,对大气污染物的表征研究和大气污染的化学过程与模式的研究,作了详细的阐述,特别对大气颗粒物的表征与来源的识别、大气光化学反应、自由基反应及其它活性物种的反应在近年的发展作了全面的总结,介绍了当今全球性大气污染的一些重大环境问题,如酸雨、臭氧层破坏、温室效应等有关大气化学研究的情况,回顾了大气污染化学对中国经济与科学发展中的重要作用。     

Chemistry of preen gland secretions of passerines: different pathways to same goal? why?

Summary. Passeriformes is the largest order of birds and includes one third of the bird species of the world, living in very diverse habitats. We investigated the chemistry of preen gland secretions of some groups of passerines from temperate regions found in diverse microhabitats. Some of the common components were mixtures of homologous monoesters made up of long chain acids and alcohols. Individual species had characteristic distribution of esters and was unique to a given species, although there were some individual variations. We compared the composition of acids and alcohols that formed same molecular weight esters in different species and we found that the combination of acids and alcohols to arrive at same molecular compositions varied distinctly between species. To compare compositions of over all acids and alcohols that formed the esters, the representative samples of secretions from the individual species were transesterfied the produce methyl esters and alcohols. We found that there were distinct differences in number of acids and alcohols that produced the combination of homologous mixtures of esters. Also they differed both qualitatively and quantitatively. There were also seasonal differences in the secretion components. Thus though the intact mixtures of esters in individual species had some similarities, they were very complex mixtures and differed characteristically for individual species. Here we discuss possible causes for evolution of these variations. We suggest that the evolution in variation of preen gland secretion is probably due to selective pressures caused by ectosymbionts such as feather-mites and feather-chewing lice that live on feathers and probably feed on the secretions and surrounding environments