Speciation of Cr and its leachability in coal by-products from spanish coal combustion plants

This study evaluates the behaviour of total Cr and Cr (VI) during coal combustion in two Spanish power stations. The content and distribution of Cr in the feed coal and combustion wastes was determined and the Cr contents were normalized using enrichment factor indexes. The speciation of Cr in the fly ash fractions from the different hoppers of the electrostatic precipitators was established and the possibility that the Cr (VI) might lixiviate when ashes are disposed of at landfill sites was assessed. Differences in the distribution and behavior of Cr in the two power stations were observed. According to European directive 1999/31/CEE, soluble Cr(VI) in the fly ashes studied would be unlikely to pose an environmental or health risk when the ash is disposed of.     

Determination of contaminant levels and remediation efficacy in groundwater at a former in situ recovery uranium mine

There has been increasing interest in uranium mining in the United States via in situ recovery techniques. One of the main environmental concerns with in situ uranium mining is the potential for spreading groundwater contamination. There is a dearth of detailed analysis and information regarding the outcome of in situ uranium mine remediation to ascertain the environmental impacts. Regulatory measurements performed at a Wyoming in situ uranium mine were collected and analysed to ascertain the efficacy of remediation and potential long term environmental impact. Based on the measurements, groundwater sweeping followed by reverse osmosis (RO) treatment proved to be a highly efficient method of remediation. However, injection of a reductant in the form of H(2)S after groundwater sweeping and RO did not further reduce the aqueous concentration of U, Mn, or Fe. Low concentrations of target species at monitoring wells outside the mined area appear to indicate that in the long term, natural attenuation is likely to play a major role at reductively immobilizing residual (after remediation) concentrations of U(VI) thus preventing it from moving outside the mined area. Our analysis indicates the need for additional monitoring wells and sampling in conjunction with long term monitoring to better understand the impacts of the different remediation techniques.     

Monitoring the species of arsenic, chromium and nickel in milled coal, bottom ash and fly ash from a pulverized coal-fired power plant in western Canada

The concentration of As, Cr and Ni and their speciation (As3+;5+, Cr3+;6+ and Ni0;2+) in milled coal, bottom ash and ash collected by electrostatic precipitator (ESP) from a coal fired-power plant in western Canada were determined using HGAAS, ICP-AES and XANES. The chemical fractionation of these elements was also determined by a sequential leaching procedure, using deionized water, NH4OAC and HCI as extracting agents. The leachate was analyzed by ICP-AES. Arsenic in the milled coal is mostly associated with organic matter, and 67% of this arsenic is removed by ammonium acetate. This element is totally removed from milled coal after extraction with HCI. Arsenic occurs in both the As3+ and the As5+ oxidation states in the milled coal, while virtually all (>90%) of the arsenic in bottom ash and fly ash appears to be in the less toxic arsenate (As5+) form. Both Ni and Cr in the milled coal are extracted by HCI, indicating that water can mobilize Ni and Cr in an acidic environment. The chromium is leached by water from fly ash as a result of the high pH of the water, which is induced during the leaching. Ammonium acetate removes Ni from bottom ash through an ion exchange process. Chromium in milled coal is present entirely as Cr3+, which is an essential human trace nutrient. The Cr speciation in bottom ash is a more accentuated version of the milled coal and consists mostly of the Cr3+ species. Chromium in fly ash is mostly Cr3+, with significant contamination by stainless-steel from the installation itself.     

Tracing sources of coal combustion using stable sulfur isotope ratios in epilithic mosses and coals from China

In China, coal combustion is the most important source of atmospheric sulfur pollution. Moss sulfur isotopic signatures have been believed to hold source-specific information that can serve as a fingerprint to identify atmospheric sulfur sources. In cities where only local coals were combusted, we observed a good correspondence of average sulfur isotope ratios in urban mosses (Haplocladium microphyllum) to the values of local coals (δ(coals) = 1.455δ(mosses)- 3.945, R(2) = 0.975, p = 0.01). But if different types of coals were combusted, we did not know whether moss sulfur isotope ratios can indicate mixed coals. To confirm this, using a mixing model we estimated the ratios of imported coal to local coals at cities where both coals were used. We found that the estimated ratios at large cities (>1 million people) where both coals were used were similar to the reported ratios in their respective provinces. For small cities (<0.5 million people) in Jiangxi Province and other provinces, the estimated ratios were higher than the reported ratios because the relatively cheaper local coals were less used in all the small cities except in cities where local coal deposits were found nearby. The comparison results showed that moss sulfur isotope is a useful tool for indicating coal-derived sulfur even in cities where mixed coals were combusted.     

增压溶样－冷原子荧光法测定煤样中的汞

采用增压溶样器加７：３：５的ＨＮＯ３－Ｈ２ＳＯ４－ＨＣｌＯ４混合酸处理煤样．用冷原子荧光法测定煤样中的总汞含量。该法的加标回收率为９２．７～１１２．５％,结果令人满意。     

Ecotoxicological assessment of acid mine drainage: electrophysiological changes in earthworm (Aporrectodea caliginosa) and aquatic oligochaete (Lumbriculus variegatus)

Ecological health of 15 sites in two mining areas on the West Coast of the South Island, New Zealand, was assessed using a non-invasive electrophysiological technique. The conduction velocity (CV) changes in the medial giant fibres (MGF) of the terrestrial earthworm Aporrectodea caliginosa were measured on days 0, 1, 2, 4, 7, 14, and 21 following exposure to soil and/or sediment from six acid mine drainage (AMD) sites, and aquatic oligochaete Lumbriculus variegatus at 0, 3, 6, and 24 h following exposure to water from 14 AMD sites. The colour of the soil/sediments varied from red-brown to black with pH ranging from 4.46 to 7.37. The colour of AMD water samples varied from clear, black, brown to orange, and the pH ranged from 2.99 to 7.66. The CV decreased progressively in A. caliginosa exposed to most soil and sediment samples from the AMD sites (compared with controls exposed to soil from an organic farm) and this was most evident in measurements taken at 7 days. Based on the CV measurements taken on day 7, sites 3 > 2 > 1 were significantly (P < 0.05) the most toxic to earthworms. The CV of L. variegatus exposed to AMD water sampled from many sites also decreased progressively and this was significantly lower than the controls in the measurements taken at 24 h from sites 3 > 9 > 7 > 11. It is proposed that MGF CV in A. caliginosa and L. variegatus worms can be used as a non-invasive, sensitive, biomarker to monitor the toxicity of AMD sites.     

Native plant restoration combats environmental change: development of carbon and nitrogen sequestration capacity using small cordgrass in European salt marshes

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C g^?1and sediment N content was ca. 1.8 mg N g^?1. The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g^?1) and the lowest in roots (361?±?4 mg C g^?1). S. maritima also concentrated more N in its leaves (31?±?1 mg N g^?1) than in other organs. C stock in the restored marshes was 29.6 t C ha^?1; ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha^?1, with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation.     

工业废水中烟酸、烟酰胺和3-氰基吡啶的HPLC检测

探讨了采用HPLC法检测某烟酰胺生产废水中所含的烟酸、烟酰胺和3-氰基吡啶的方法。结果显示,该方法的检测范围(S/N=3)为0.70~1.18 mg/L,方法的回收率为87%~102%,相对标准偏差为0.9%~3.9%,是一种快速、敏感和可靠的测定方法。     

Determination of total and partially extractable solid-bound element concentrations using collision/reaction cell inductively coupled plasma-mass spectrometry and their significance in environmental studies

Determination of solid-bound element concentrations is an important initial step in environmental studies especially for assessment of contamination level, and of origin, relative mobility, and fate of contaminants. This study revealed that a relatively new collision/reaction cell inductively coupled plasma-mass spectrometry is a potent tool for determining total and partially extractable solid-bound element (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, and Pb) concentrations in a complex matrix solution containing HF and/or HCl. Six different extraction methods commonly used for environmental monitoring studies were tested for their bias and variability using estuarine and marine standard reference materials. Microwave-assisted methods based on concentrated [HNO₃] or [HNO₃?+?HF (4:1)] and [HNO₃?+?HF?+?HCl (10:3:2)] were applied for determining pseudo-total and total element concentrations, respectively. Dilute-acids (1 M HNO₃, 1 M HCl, and 0.5 M HCl) were utilized in single-step partial extraction protocols. Except the 0.5 M HCl cold-extraction method which was performed at room temperature, other partial extraction protocols used microwave-digestion. This study demonstrated that the use of microwave-assisted methods in studies aimed at determining the non-residual, non-specific extractable fractions of elements in solid environmental samples may result in overestimation, and thus needs to be re-examined. We believe that the cold extraction method will play a significant role in future environmental monitoring studies. Nevertheless, results of the cold extraction method not accompanied with total element concentrations have limited value, as the amount of extraction may vary significantly with the nature (origin) of the elements, and with the types of the samples. Therefore, we suggest combining microwave-assisted total digestion and 0.5 M HCl cold-extraction methods as a relatively cost- and time-effective, environmentally sound screening procedure for routine environmental monitoring programs involving a large number of samples from diverse geological and anthropogenic settings.     

Use of the Multispecies Freshwater Biomonitor to assess behavioral changes of Poecilia reticulata (Cyprinodontiformes: Poeciliidae) and Macrobrachium lanchesteri (Decapoda: Palaemonidae) in response to acid mine drainage: laboratory exposure

The behavioral responses of guppy Poecilia reticulata (Poeciliidae) and prawn Macrobrachium lanchesteri (Palaemonidae) individuals exposed to acid mine drainage (AMD) were monitored online in the laboratory with a Multispecies Freshwater Biomonitor? (MFB). These responses were compared to those to reference water acidified to the respective pH values (ACID). Test animals in the juvenile stage were used for both species and were exposed to AMD and ACID for 24 hours. The stress behaviors of both test animals consisted mainly of decreased activity in AMD and increased activity in ACID, indicating that the metals in the AMD played a role as a stress factor in addition to pH. The locomotor activity levels of guppies and prawns for the ACID treatment were higher than the locomotor activity levels for the AMD treatment with increasing pH value. For guppies, significant differences were observed when specimens were exposed to AMD and ACID at pH 5.0 and 6.0; the percentage activities were only 16% and 12%, respectively, for AMD treatment, whereas for ACID treatment, the percentage activities were 35% and 40%, respectively, similar to the value of 36% for the controls. Similar trends were also observed for prawns, for which the percentage activities were only 6% and 4%, respectively, for AMD treatment, whereas for ACID treatment, the percentage activities were 31% and 38%, respectively, compared to 44% in the controls. This study showed that both species are suitable for use as indicators for ecotoxicity testing with the MFB.