Relative molar mass distributions of chromophoric colloidal organic matter in coastal seawater determined by Flow Field-Flow Fractionation with UV absorbance and fluorescence detection

A new method for the characterization of chromophoric colloidal organic matter in seawater has been applied to samples from the Baltic Sea, Kattegatt and Skagerrak seas. Size fractionation of the sample by Flow Field-Flow Fractionation and measurement of the fluorescent and UV absorbing properties of the individual size fractions result in a relative molar mass distribution (RMM) of the optical properties. The RMM distributions have been used to estimate number and weight average relative molar masses, and polydispersity indices. At least two sources of coloured organic matter were identified from the ratio of fluorescence to UV: the Baltic surface water and the Skagerrak deep water. The dominating processes were mixing and dilution, but processes such as photo bleaching of fluorescence are also believed to be important. The RMM distribution derived from UV detection (1150–1300 Dalton) increased with increasing salinity while that derived for fluorescence (1500–1250 Dalton) decreased with increasing salinity. The specific UV absorbance taken as a proxy of the aromaticity of the chromophoric organic material showed decreasing trend with both increasing salinity and increasing UV derived weight average relative molar mass. Increasing polydispersity of the colloidal material was also observed as a function of salinity.     

度量泥炭腐殖化度的一种简便方法:泥炭灰度

介绍了一种度量泥炭腐殖化程度简便易得的指标——灰度。通过将同一剖面灰度测量结果与传统的腐殖化度测量结果进行对比，发现二者的变化具有较强的相关性，说明导致二者变化的因素大致相同。泥炭赋色物质鉴定的实验表明腐殖质含量变化是引起灰度在剖面上变化的原因，从而进一步论证了用灰度值作为泥炭腐殖化程度指标的可行性。     

A study of the serpentinisation in the Vempalle dolomitic limestones near Pulivendala,Cuddapah District

The calcite-dolomite ratio of the Vempalle dolomitic limestones, serpentinised dolomitic limestones, and serpentines from the mineralised zone of the asbestos is determined by infrared spectroscopy. The ratio varies between 2 and 5·4 in the dolomitic limestones, between 1 and 1·5 in the serpentinised dolomitic limestones and it is taken as zero in the serpentines as both calcite and dolomite bands are absent in their infrared absorption spectra. The release of calcite during the serpentinisation is identified, which confirms the formation of serpentine.     

Continuous fluorescence assessment of organic matter variability on the Bournbrook River,Birmingham, UK

Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high‐temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short‐term variations in chemical and ecological function. The authors report a 2‐week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub‐daily variations in both organic matter concentration and characteristics. In particular, after relatively high‐magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic‐like and tryptophan‐like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation < 2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation > 2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic‐like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer‐derived ‘old’ organic matter at low‐rainfall amounts and a mixed signal at high‐precipitation amounts where ‘event’ surface runoff‐derived organic matter dominate during storm sewer and combined sewer overflow routed DOM. Copyright © 2009 John Wiley & Sons, Ltd.     

红透山黄铁矿的红外光谱研究

为了深入研究黄铁矿物理性质的实际成因意义,利用NICOLET 380型,分辨率＞0.9 cm-1傅立叶变换红外光谱仪,对红透山地区不同中段的黄铁矿样品进行测量,在400~4 000 cm-1范围内分别得出红外光透射光谱图。运用朗伯比尔定律计算出各中段样品的吸光度。结果表明：红透山黄铁矿(FeS2)中存在不同程度的类质同象取代,该区域黄铁矿导电类型为n型。认为此种类质同象与黄铁矿形成部位具有相关性。吸光度比值与样品所在深度负相关。     

长江下游湖泊水体中有色可溶性物质的生物光学模式

通过2001年7月至2002年12月对长江下游的太湖、巢湖、龙感湖水体中有色可溶性物质的光吸收及荧光特性的研究发现:在对S值进行测定时,所测得的S值为0·0046nm-1(SD=0·0015,n=284),与文献中的0·014nm-1相差较大,可能是由于高浓度的DOC受到激发后在蓝光波段释放较强荧光的缘故;荧光强度与水体中DOC含量之间的关系较难确定,DOC与350nm光吸收(a(350nm))之间呈现较强的线性关系,其相关值达到0·673(n=284);荧光强度与a(350nm)之间线性关系相对较弱,其相关值为0·497(n=214);从上面的结果可以看出,用荧光的方法直接测定DOC含量的可信度相对较低,而直接利用光吸收测定的可信度较高。     

Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River (California,USA)

Dissolved organic matter (DOM) concentration and composition in riverine and stream systems are known to vary with hydrological and productivity cycles over the annual and interannual time scales. Rivers are commonly perceived as homogeneous with respect to DOM concentration and composition, particularly under steady flow conditions over short time periods. However, few studies have evaluated the impact of short term variability (<1 day) on DOM dynamics. This study examined whether diurnal processes measurably altered DOM concentration and composition in the hypereutrophic San Joaquin River (California) during a relatively quiescent period. We evaluated the efficacy of using optical in situ measurements to reveal changes in DOM which may not be evident from bulk dissolved organic carbon (DOC) measurement alone. The in situ optical measurements described in this study clearly showed for the first time diurnal variations in DOM measurements, which have previously been related to both composition and concentration, even though diurnal changes were not well reflected in bulk DOC concentrations. An apparent asynchronous trend of DOM absorbance and chlorophyll‐a in comparison to chromophoric dissolved organic matter (CDOM) fluorescence and spectral slope S_290–350 suggests that no one specific CDOM spectrophotometric measurement explains absolutely DOM diurnal variation in this system; the measurement of multiple optical parameters is therefore recommended. The observed diurnal changes in DOM composition, measured by in situ optical instrumentation likely reflect both photochemical and biologically‐mediated processes. The results of this study highlight that short‐term variability in DOM composition may complicate trends for studies aiming to distinguish different DOM sources in riverine systems and emphasizes the importance of sampling specific study sites to be compared at the same time of day. The utilization of in situ optical technology allows short‐term variability in DOM dynamics to be monitored and serves to increase our understanding of its processing and fundamental role in the aquatic environment. Copyright © 2007 John Wiley & Sons, Ltd.     

Spectrophotometric determination of dissolved organic carbon in some South Island streams and rivers (note)

Absorbance at 360 nm and dissolved organic carbon (DOC) concentration were measured on 47 filtered water samples collected from streams and rivers of the west coast of South Island, New Zealand. The regression equation (DOC (g m^‐3) = 59.6 Abs_{1 cm} + 1.9) calculated from the data, reliably predicted DOC concentration within the range 1.6–43.2 gm^‐3. This relationship is similar to that found fsr some Venezuelan and south‐eastern United Stales waters indicating that it may have widespread utility for estimating DOC concentrations in soft waters where DOC is dominated by humic substances     

The diel cycle of carbonyl sulfide in marine surface waters: Field study results and a simple model

The concentrations of atmospheric and dissolved carbonyl sulfide (COS) were measured during a Lagrangian study aboard the R/V Meteor in the northeast Atlantic Ocean, April/May 1992, and during a campaign on the research platform Nordsee in the German Bight (southeastern North Sea), September 1992. The arithmetic means and standard deviations of the COS saturation ratios were 1.27 ± 0.58 (northeast Atlantic) and 3.23 ± 0.73 (German Bight). Sea surface COS showed a pronounced diel cycle with highest concentrations in the late afternoon and a mean concentration amplitude of about 2. To account for this diel cycle, we analyze our results using a simple empirical model, which includes a zeroth order photoproduction constant, sea surface UV light intensity, and terms for hydrolysis removal and air-sea exchange. Fitted and observed COS concentrations agreed to within11 % (northeast Atlantic) and 14% (German Bight). The in situ COS photoproduction constants were (0.030 ± 0.008) fmol L^–1 s^–1 W^–1 m² in the northeast Atlantic (n = 8) and (0.17 ± 0.07) fmol L^–1 s^–1 W^–1 m² in the German Bight (n = 10). After normalization to the cloud cover corrected UV irradiance at 40 latitude, we obtained sea surface COS production rates of (0.034 ± 0.017) nmol L^–1 d^–1 in the northeast Atlantic and (1.62 ± 0.62) nmol L^–1 d^–1 in the German Bight. Currently available in situ photoproduction rates show a high degree of correlation with the UV absorbance (r ² = 0.98, n = 4) and fluorescence (r ² = 0.85, n = 4) of chromophoric dissolved organic matter (CDOM). The regional differences between the COS productivity in the northeast Atlantic Ocean and the German Bight is attributed to the distribution pattern of CDOM optical properties.     

苏丹黑B染色处理细胞技术在快速检测微藻油脂含量中的应用

探讨了采用苏丹黑B染料染色处理微藻细胞技术估测微藻油脂含量的可行性.结果表明,微藻细胞经苏丹黑B染色处理后在645 nm光波长处有最大吸收峰值A645,微藻油脂含量与经苏丹黑B染色处理后微藻细胞的吸光值A645呈明显的相关性.建立了考察的7种微藻油脂含量与吸光值A645的线性回归方程,线性关系显著（p〈0.01）.基于藻湿重,微藻油脂含量的线性范围为1.79~39.63 mg/g,估算的相对偏差〈10%.因而,采用苏丹黑B染色处理微藻细胞技术适宜用来检测微藻的油脂含量.