Improper environmental sampling design bias assessments of coastal contamination

Pollution of coastal areas play an important role in anthropocentric issues. Thus, several analytical tools were developed and optimized in recent years aiming to improve the acquisition of good quality chemical data. Despite these efforts, assessments of the environmental occurrence of hazardous chemicals in coastal regions are often biased by poorly planned sampling campaigns. In coastal zones, the influence of local contamination sources and environmental factors (such as coastal currents, tides, estuarine discharges, depth and luminosity) should be carefully considered before establishing a sampling grid. Moreover, the wrong selection of the environmental matrix to be analyzed, especially by multiresidue methods which include analytes with different physicochemical properties, has also been an important source of bias in many published papers. This critical review provides an overview of the key-factors to be considered during the planning and execution of sampling campaigns seeking to identify and quantify contaminants in environmental samples obtained in coastal areas. Further, a discussion on a more suitable and cost-effective sampling design, based in recent advances, is also presented.     

Detection of environmental polyorganosiloxanes (silicones) by silicon-29 NMR spectroscopy

The utility of ²⁹Si NMR spectroscopy has been demonstrated on sediment-like materials in the quantitative and qualitative determination of polyorganosiloxanes (silicones) in selected environmental samples. This technique is highly selective for polydimethylsiloxanes (PDMS) and is non-destructive to the sample. Also, specific identification of polyorganosiloxanes in sediment is possible, in contrast to previous methods which provided only quantitative information while consuming the sample. The detection limit for a 9 h experiment is approximately 45 ppm.     

Comparison of GC-ECD,GC-MS and GC-AED for the determination of polychlorinated biphenyls in highly contaminated marine sediments

Summary Electron capture detection (ECD), low- and highresolution mass spectrometry (LR- and HRMS), and atomic emission detection (AED) were compared for the gas chromatographic (GC) detection of polychlorinated biphenyls (PCBs) present in highly contaminated marine sediments. With ECD, LRMS, and even HRMS, detection was seriously disturbed by the complex matrix of the sediments, whereas AED in the chlorine-selective mode provided excellent PCB profiles without interferences. In addition, GC-AED provided congener independent responses, which enabled accurate quantitation of all PCBs based on a single calibration curve. However, because GC-AED was less sensitive than the other techniques studied, preparation of relatively large amounts of sample (10–20 g dry sediment) was required for most analyses.     

Methylation of tin(II) by methyl iodide in porewater

The methylation of tin(II) chloride by methyl iodide in porewater and formation of monomethyltin as the only methyltin product are described. A factorial experiment tested the effects of concentrations of tin(II), methyl iodide, and oxygen on monomethyltin yields. The experiments gave 0.18 to 12.8 % yield. Analysis of variance (ANOVA) calculations showed that all three variables were significant at the 95 % level. Comparison of yields in aqueous 23 g kg^?1 sodium chloride solutions to those in porewater and to those containing fulvic acid, salicylic acid, and EDTA showed that only fulvic acid significantly reduced yields. Reasons for this observation are discussed and the findings in the model system are related to methylation of tin compounds in sediments.     

Determination of lead in sediments and sewage sludge by on-line hydride-generation axial-view inductively-coupled plasma optical-emission spectrometry using slurry sampling

Among the “traditional” hydride-forming elements, lead is probably the most difficult, and its determination in this form has rarely been reported in the literature. In this paper a simple and rapid method, axial-view inductively-coupled plasma optical-emission spectrometry using on-line hydride generation (HG–ICP–OES) from samples prepared as slurry, is proposed for determination of lead in environmental samples. The samples (20–50 mg, particle size ≤120 μm) were treated with 1 mL aqua regia in a 40-kHz ultrasonic bath for 60 min. The slurry was diluted to a final volume of 50 mL with a 10% m/v solution of (NH₄)₂S₂O₈. The concentrations of NaBH₄, tartaric acid, and (NH₄)₂S₂O₈, used for on-line plumbane generation were optimized by means of a complete factorial analysis applied to an aqueous standard solution and to the slurry of a sediment certified reference material (CRM). External calibration against aqueous standards in the concentration range 10–100 μg L⁻¹ was used for analysis of six CRM—three marine sediments, one river sediment, and two sewage sludges. Analysis of the filtered slurry showed that Pb was only partially extracted into the liquid phase. Several major concomitants tested did not affect the Pb signal. The detection limit (3s, n = 10) for 20 mg sample in a final volume of 50 mL was 5.0 μg g⁻¹. Tin was the only other hydride-forming analyte that could be determined satisfactorily with Pb; for tin the detection limit was 1.0 μg g⁻¹. The values obtained for Pb and Sn were not significantly different from the certified concentrations, according to the t-test at the 95% confidence level. Nine river sediments collected locally were also analyzed and the concentrations were in agreement with results obtained after total digestion.     

A study of arsenic contamination by graphite furnace atomic absorption spectrometry in the Lami estuary in Fiji

The Suva–Lami coastal environment in Fiji is submitted to intense heavy metal input from land-based industrial activities. Therefore, continuous environmental monitoring is required in order to develop and implement environmental management programs for the Suva Lagoon. Current ongoing research includes investigation and monitoring of the short and long-term variation of several heavy metals in the sediments of Suva and Lami coastal environments based on the observations from past similar studies. This study, for the first time, reports the incidence of high arsenic (As) contamination in the sediments of the Lami estuary. The short term variations in the concentrations of As in Lami estuary were in the range of 1.0–334.0 mg kg⁻¹ (dry weight), which ascended gradually over a period of one year. A literature survey showed that this is the highest As contaminated site as compared to other studied sites in Fiji. The results indicate that immediate corrective waste management measures have to be practiced by the industrial community to lessen the impact of toxic metal loading in these vital areas of community life.     

Matrix solid phase dispersion-assisted BCR sequential extraction method for metal partitioning in surface estuarine sediments

The BCR (the Community Bureau of Reference) of the European Union sequential extraction scheme for metal partitioning in estuarine sediments has been accelerated by using a matrix solid phase dispersion (MSPD) approach. The MSPD assisted BCR procedure consists of passing the extractants proposed by conventional BCR protocol (0.11 M acetic acid, 0.1 M hydroxylammonium chloride and 8.8 M hydrogen peroxide plus 1 M ammonium acetate) through the dispersed sample packaged inside a disposable syringe. Different silica-, magnesium- and aluminium-based materials were tested as dispersing agents and sea sand was found to offer the best performances. Variables for assisting the three stages of the BCR protocol were optimized, and accurate results were obtained when assisting the first and the third stages (exchangeable and oxidizable fractions, respectively). However, lack of accuracy was observed when assisting the second step (reducible fraction) and this result agrees with most of the assisted BCR procedures for which extracting the reducible fraction is the most troublesome stage. The organic matter oxidation (third stage) was successfully assisted by passing hydrogen peroxide at 50 °C through the dispersed sample inside de syringe just before passing ammonium acetate. Therefore, the time-consuming and unsafe conventional organic matter oxidation processes, commonly performed even for microwave/ultrasounds assisted BCR procedures, are totally avoided. Inductively coupled plasma-mass spectrometry (ICP-MS) was used as a selective detector. The target elements were Cd, Co, Cr, Mn, Ni, Sr and Zn (first stage), Cd, Co and Ni (second stage), and Co, Cr, Mn, Ni, Sr and Zn (third stage). Repeatability of the method (n = 7) was good, and RSDs values of 9, 10, 10, 8, 8, 3 and 8% was obtained for Cd, Co, Cr, Mn, Ni, Sr and Zn, respectively (first stage); 10, 9 and 9% for Cd, Co and Ni, respectively (second stage); and 6, 2, 3, 4, 7 and 9% Co, Cr, Mn, Ni, Sr and Zn, respectively (third stage). The procedure was also validated by analysing two certified reference materials (CRM 601 and CRM 701). Good accuracy was obtained for the target elements extracted at the first stage: Cd (4.0 ± 0.1 and 7.3 ± 0.09 μg g⁻¹ in CRM 601 and CRM 701, respectively), Cr (0.36 ± 0.008 and 2.21 ± 0.08 μg g⁻¹ in CRM 601 and CRM 701, respectively), Ni (8.0 ± 0.3 and 15.4 ± 0.3 μg g⁻¹ in CRM 601 and CRM 701, respectively) and Zn (262 ± 3 and 203 ± 3 μg g⁻¹ in CRM 601 and CRM 701, respectively). Also, good accuracy was observed for elements extracted at the third step: Cd (1.8 ± 0.09 and 0.29 ± 0.03 μg g⁻¹ in CRM 601 and CRM 701, respectively), Cr (145 ± 4 μg g⁻¹ in CRM 701), Ni (8.2 ± 0.7 and 15.1 ± 0.5 μg g⁻¹ in CRM 601 and CRM 701, respectively) and Zn (45 ± 0.7 μg g⁻¹ in CRM 701).     

Measurements of arsenite and arsenate contained in mining river waters and leached from contaminated sediments by sequential hydride generation flow injection analysis

In this work, a new analytical method for gasifiable compounds based on sequential hydride generation flow injection analysis (SHGFIA) was applied to water analysis and leaching investigation. For water analysis, it was confirmed that 1 μg L⁻¹ As(III) and As(V) were stable for a few days when EDTA was added in the sample waters. Dissolved As(III) and total arsenic (As(III) + As(V)) were converted to AsH₃ in neutral and acidic medium, respectively, to transfer to a miniature gas scrubber (100 μL in absorber volume). The collected arsenic was successively measured by flow analysis based on molybdenum blue chemistry. With this system, changes in As(III) and As(V) concentrations of water placed with arsenic-contaminated-sediment was monitored in near real time. From these data, kinetic analyses were carried out and kinetic constant was obtained from plot of ln{(C^∞ − C)/C^∞} where C and C^∞ were leached arsenic concentration and its final concentration, respectively. It was found that rate of As(III) leaching was much faster than that of As(V) while As(V) leached more in amount compared to As(III). In this work, it was demonstrated that kinetic investigation is also one of the important application of flow analysis. The SHGFIA system showed excellent performance for leaching analysis of arsenic with discrimination of As(III) and As(V).     

微波消解-超声辅助萃取-ICP-AES测定沉积物中的10种金属元素

采用微波消解-超声辅助萃取体系,仅需用盐酸和硝酸对沉积物样品进行前处理,即可用ICP-AES测定沉积物样品中的10种金属元素.在最优化的实验条件下,测定值与参考值吻合,相对标准偏差均小于5％,加标回收率在92.2％～106％之间.     

Towards a Standard Method for the Measurement of Organic Carbon in Sediments

Abstract

The precisions achieved by two different methods for analysis of organic carbon in soils and sediments were determined and compared. The first method is a rapid dichromate oxidation technique (Walkley-Black) that has long been a standard in soil chemistry. The second is an automated coulometric titration method for which commercial instrumentation is available. The latter method shows relative standard deviations that are six to twenty times smaller than the dichromate oxidation technique. Development of a standardized sediment with a low level of organic carbon is recommended in order to facilitate the evaluation of the precision and accuracy of organic carbon measurement techniques.