Use of Mössbauer spectroscopy to determine the effect of salinity on the speciation of triorganotins in Anacostia River sediments

The speciation of several tributyltin and triphenyltin compounds under varying salinity conditions (0, 20, 40 and 60%) was studied by Mössbauer spectroscopy in both anaerobic and aerobic Anacostia River sediments. The Mössbauer spectral parameters of the spiked sediments indicated that changes in the salinity did not affect the speciation of the tin compounds in either aerobic or anaerobic sediments.     

Determination of lead in Yellow River using ammonium molybdate as a molecular probe by resonance light scattering technique

A novel method for the determination of trace lead in Yellow River using ammonium molybdate (AM) as a molecular probe based on resonance light scattering (RLS) has been developed. In the presence of KHC₈H₄O₄-NaOH buffer solution, Pb²⁺ can react with AM to form an association, which results in the significant enhancement of RLS intensity and the appearance of the corresponding RLS characteristics. The enhanced RLS intensity is directly proportional to the concentration of Pb²⁺ in the range of 0.01-1.0 μg mL⁻¹. The detection limit can achieve 1.89 ng mL⁻¹. Moreover, the characteristics of RLS spectra of the complexes, the optimum conditions and the influencing factors have been investigated. The method has high selectivity and sensitivity, and was applied to the determination of Pb²⁺ in Yellow River with satisfactory results, which was in agreement with that of atomic absorbance spectrometry (AAS).     

Natural and anthropogenic variations in the Po river waters (northern Italy): insights from a multi-isotope approach

Po is the main Italian river and the δ¹⁸O and δ²H of its water reveal a similarity between the current meteoric fingerprint and that of the past represented by groundwater. As concerns the hydrochemisty, the Ca–HCO₃ facies remained constant over the last 50 year, and only nitrate significantly increased from less than 1?mg/L to more than 10?mg/L in the 1980s, and then attenuated to a value of 9?mg/L. Coherently, δ¹³C_DIC and δ³⁴S_SO4 are compatible with the weathering of the lithologies outcropping in the basin, while extremely variable δ¹⁵N_NO3 indicates contribution from pollutants released by urban, agricultural and zootechnical activities. This suggests that although the origin of the main constituents of the Po river water is geogenic, anthropogenic contributions are locally significant. Noteworthy, the associated aquifers have the same nitrogen isotopic signature of the Po river, but are characterized by significantly higher NO^– ₃ concentration. This implies that aquifers’ pollution is not ascribed to inflow of current river water, and that the attenuation of the nitrogen load recorded in the river is not occurring in the aquifers, due to their longer water residence time and delayed recovery from anthropogenic contamination.     

Determination of trace metals in the River Ye?il?rmak sediments in Tokat, Turkey using sequential extraction procedure

Sequential extraction procedure (acid extractable, reducible, oxidizable, and residual) proposed by BCR was applied for the determination of trace metals in the River Yesilirmak sediments, Tokat, Turkey. The determination of trace metals in sediment samples was performed by flame atomic absorption spectrometry. The proposed method showed satisfactory recovery, detection limits and standard deviation for trace metals determination in sediment samples. Generally, most of the elements were found in the oxidizable and residual fractions. The total concentrations of trace metals analyzed were found to be (mg/kg) Cu: 37.9, Mn: 392.2, Zn: 126.2, Fe: 3726, and Pb: 29.6, respectively. Results obtained are in agreement with data reported in the literature.     

Redox Speciation of Vanadium in Estuarine Waters Using Improved Methodology Based on Anion Exchange Chromatography Coupled to HR ICP-MS System

An improved methodology was developed for V redox speciation in estuarine waters using a hyphenated technique consisting of ion chromatograph (IC) with an anion exchange column and a high-resolution inductively coupled plasma mass spectrometer (HR ICP-MS). This approach enables the direct determination of V(V), whereas reduced species (mainly V(IV)) are calculated by subtracting V(V) concentrations from the measured total V concentration. Based on the “on-column” V(V) chelation mechanism by EDTA, with the eluent composed of 40 mmol L⁻¹ ammonium bicarbonate, 40 mmol L⁻¹ ammonium sulphate, 8 mmol L⁻¹ ethylenediaminetetraacetic acid and 3% acetonitrile, the method was successfully used for analyses of V redox speciation in samples taken in the vertical salinity gradient of the highly stratified Krka River estuary. Due to the matrix effects causing different sensitivities, a standard addition method was used for V(V) quantification purposes. The limit of detection (LOD) was also found to be matrix related: 101.68 ng L⁻¹ in the seawater and 30.56 µg L⁻¹ in the freshwater. Performed stability tests showed that V redox speciation is preserved at least 7 days in un-treated samples, possibly due to the stabilization of V-reduced species with natural organic matter (NOM). The dominant V form in the analysed samples was V(V) with the reduced V(IV) accounting for up to 26% of the total dissolved pool. The concentration of V(IV) was found to correlate negatively with the oxygen concentration. Significant removal of dissolved V was detected in oxygen depleted zones possibly related to the particle scavenging.     

Temporal characterisation of river waters in urban and semi-urban areas using physico-chemical parameters and chemometric methods

Three sampling campaigns were carried out in rivers located at two hydrographic basins affected by urban and semi-urban areas around the Metropolitan area of A Coruña (ca. 500,000 inhabitants, NW-Spain) to study local and temporal variations of 21 physicochemical parameters (pH, conductivity, Cl⁻, SO₄²⁻, SiO₂, Ca²⁺, Mg²⁺, Na⁺, K⁺, hardness, NO₃⁻, NO₂⁻, NH₄⁺, COD, PO₄³⁻, Zn²⁺, Cu²⁺, Mn²⁺, Pb²⁺, alkalinity and acidity) in 23 sampling points. The temporal evolution of the water quality was assessed by matrix augmentation principal components analysis (MA-PCA) and parallel factor analysis (PARAFAC). Moreover, classical principal components analysis (PCA) (one per sampling campaign) was applied with exploratory and comparison purposes. The first factor of the different studies comprised variables associated to the mineral content and it differentiated the samples according to their hydrographic basins. The second factor was mainly associated to organic matter, from domestic wastes and decomposition of natural debris. The temporal evolution of the water quality was mostly related to seasonal increments of the physicochemical parameters defining the decomposition of the organic matter.The three models applied (PCA, MA-PCA and PARAFAC) led to similar conclusions, nonetheless, MA-PCA excelled, since the refolding of scores provided more straightforward and convenient overview of sample time and geographical variations than individual PCA and it is more flexible and adaptable to environmental studies than PARAFAC.     

Simultaneous determination of mercury and organic carbon in sediment and soils using a direct mercury analyzer based on thermal decomposition–atomic absorption spectrophotometry

The purpose of this work was to study the feasibility of using a direct mercury analyzer (DMA) to simultaneously determine mercury (Hg) and organic matter content in sediment and soils. Organic carbon was estimated by re-weighing the sample boats post analysis to obtain loss-on-ignition (LOI) data. The DMA-LOI results were statistically similar (p < 0.05) to the conventional muffle furnace approach. A regression equation was developed to convert DMA-LOI data to total organic carbon (TOC), which varied between 0.2% and 13.0%. Thus, mercury analyzers based on combustion can provide accurate estimates of organic carbon content in non-calcareous sediment and soils; however, weight gain from moisture (post-analysis), measurement uncertainty, and sample representativeness should all be taken into account. Sediment cores from seasonal wetland and open water areas from six oxbow lakes in the Mississippi River alluvial flood plain were analyzed. Wetland sediments generally had higher levels of Hg than open water areas owing to a greater fraction of fine particles and higher levels of organic matter. Annual loading of Hg in open water areas was estimated at 4.3, 13.4, 19.2, 20.7, 129, and 135 ng cm⁻² yr⁻¹ for Beasley, Roundaway, Hampton, Washington, Wolf and Sky Lakes, respectively. Generally, the interval with the highest Hg flux was dated to the 1960s and 1970s.     

A Monitoring System for Selective Determination of Alkylphenol Ethoxylates by the Adsorptive Stripping‐Indirect Tensammetric Technique

A new monitoring system for the adsorptive stripping‐indirect tensammetric technique has been developed. The system responded selectively to alkylphenol ethoxylates having 5–14 oxyethylene subunits (APE) (being a fraction of nonionic surfactants). It consists of 20 ppm of Mannoxol OT and 20 ppb of tetrabutylammonium bromide (TBAB). In the presence of APE a tensammetric peak of the monitoring mixture is growing. A calibration plot has a slightly sigmoidal shape; the dynamic response range is from 0.5 to 2.0 μg and the detection limit is 0.075 μg. APE determination is highly tolerant to alcohol ethoxylates (AE) having a C18 hydrophobic part, however, the tolerance of AE having a C12 hydrophobic part is small (the APE signal is only three times higher than that of AE having a C12 hydrophobic part). An analytical response to a mixture consisting different nonionic surfactants (NS) is approximately additive. The developed monitoring system was applied to the determination of an APE fraction in 14 river water samples. NS were separated from the water matrix by liquid‐liquid extraction with chloroform. The recovery of Triton X‐100 spike was 102% and the precision 6.5%.     

聚合硅酸硫酸铁和聚合硫酸铁处理黄河水的效果及其絮体特性研究

采用聚合硅酸硫酸铁(PFSS)和聚合硫酸铁(PFS)两种无机高分子混凝剂处理黄河水,考察了两种混凝剂对浊度和UV254的去除效果,并结合混凝过程中絮体zeta电位的变化,分析了两种混凝剂的混凝机理.通过激光粒度仪在线观察混凝过程中絮体的生长情况,发现PFSS比PFS生成的絮体生长速度快,尺寸大.对形成的絮体施加不同强度的剪切力,通过观察絮体粒径的变化来比较絮体的强度,发现PFSS生成的絮体强度较大.研究了在不同剪切强度和不同剪切时间下絮体的破碎程度和絮体的恢复能力(分别以破碎因子Bf和恢复因子Rf表示),发现在强剪切力和长剪切时间下Bf和Rf均较大;在相同条件下PFSS生成絮体的Bf较小而PFS生成絮体的Rf较大,这表明前者的抗剪切能力较强,而后者具有更强的再生能力.     

Regional ozone pollution and key controlling factors of photochemical ozone production in Pearl River Delta during summer time

An intensive field campaign including measurements from the environmental monitoring network and from two super sites took place in the Pearl River Delta region in summer 2006.Using routinely measured O3 and NOx concentrations,the spatial and temporal variation of O3 and of the total oxidant concentrations was characterized.According to the spatial variability of NO2/NO,the two super sites were found to be representative of polluted urban and downwind suburban conditions.In addition,both sites were located ...