Journal of Environmental Monitoring最新文献

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly known for their toxicity. Although there has been substantial work on the atmospheric degradation of PAH, little is known about how the presence of atmospheric droplets (e.g., a fog cloud) affects the fate of PAH. In order to assess the processing of PAH and their corresponding oxidation products during a fog event, two field-sampling campaigns in Fresno, CA and Davis, CA were conducted. The simultaneous evaluation of concentrations of the PAH and oxygenated polycyclic aromatic compounds (OPAC) in the gas phase, particulate matter and fog water droplets before, during and after fog allows for the characterization of transformative and transport processes in a fog cloud. By tracking the ratio of OPAC to PAH in the individual atmospheric phases, two major polycyclic aromatic compounds-processing pathways can be identified: (i) the dissolution of OPAC from particulate matter and (ii) the uptake and oxidation of PAH in the fog water droplets. Wet deposition steadily decreases the pollutant concentration in the fog cloud droplets during a fog event; however, uptake and concentration via evaporative water loss upon the dissipation of a fog cloud cause an increase in the atmospheric pollutant concentration.

The size dependent colloidal behavior of aqueous dispersions of carboxylated multiwall carbon nanotubes (c-MWCNTs) is presented. The presence of carboxylic groups provided electrostatic stabilization in water, where the size affected agglomeration. While aspect ratio did not show any definite correlation, the hydrophobicity indices (HI), zeta potential and aggregation kinetics showed dependence on the length of the c-MWCNTs where the shorter c-MWCNTs showed significantly lower HI values, smaller particle aggregates, higher zeta potential values and higher critical coagulation concentrations (ccc) in the presence of electrolytes. Although the diameter of the short c-MWCNTs did not appear to influence their aggregation behavior, the longer c-MWCNTs showed a dependence on diameter where stability decreased with increasing CNT diameter.

Mining and ore excavation can cause the acidification and heavy metal pollution of downstream water systems. It can be difficult to assess the load contributions from individual mining areas, which is commonly required for environmental impact assessments. In the current study, we quantified the net impact of the unmonitored mining activities in the Zaamar Goldfield (Mongolia) on heavy metal transport in the downstream Tuul River-Selenga River-Lake Baikal water systems. We also noted that the Zaamar site shares the conditions of limited monitoring with many rapidly developing regions of the world. The heavy metal concentrations and flow data were obtained from historical measurement campaigns, long-term monitoring, and a novel field campaign. The results indicate that natural mass flows of heavy metals in dissolved form increased by an order of magnitude because of mining. Prevailing alkaline conditions in the vicinity of Zaamar can limit the dissolution, maintaining the on-site concentrations below health-risk based guideline values. However, suspended river concentrations are much higher than the dissolved concentrations. The placer gold mining at the Zaamar site has increased the total riverine mass flows of Al, As, Cu, Fe, Mn, Pb and Zn by 44.300, 30.1, 65.7, 47.800, 1.480, 76.0 and 65.0 tonnes per year respectively. We suggest that local to regional transformation and enrichment processes in combination with suspended sediment transport from numerous existing upstream mining areas contribute to high concentrations of dissolved heavy metals in downstream parts of the Selenga River, including its delta area at Lake Baikal. Furthermore, single hydrological events can increase the suspended load concentrations by at least one order of magnitude. Overall, the Selenga River Basin, which drains into Lake Baikal, should be recognised as one of the world's most impacted areas with regard to heavy metal loads, and it contributes to 1% and 3% of the world flux of dissolved Fe and Pb, respectively.

Apparatus is designed and tested to determine metals in situ in seawater. Voltammetry with a vibrating gold microwire electrode (VGME) is combined with a battery powered potentiostat and a processor board and is tested for in situ monitoring of copper (Cu) in coastal waters. The VGME was combined with solid state reference and counter electrodes to make a single vibrating probe which was rated up to a depth of 40 m. The measuring mode for Cu was square-wave anodic stripping voltammetry whilst dissolved oxygen (DO) was monitored by a linear sweep scan in a negative potential direction. The working electrode was reactivated between measurements using a suitable potential sequence. The novelties of this work are the field-testing of apparatus incorporating a VGME for copper monitoring, which eliminates the need for pumping and reagents, but has sufficient sensitivity for low ambient levels of copper, and the use of a novel potential sequence to stabilise the response over a long time period. The apparatus has a measuring time of about 6 weeks and a measuring frequency of 12 h(-1). Measurement is reagent-free and power use is low as no pump is required. Experiments are carried out to test the stability of response of the system at various temperatures and its robustness with respect to long-term copper monitoring. Preliminary data were obtained during autonomous deployment over several weeks on a buoy in the Irish Sea. Vertical movement of the buoy caused individual measurements to have a variability of about 15%. It was found that longer term variability of the electrode could be minimised by normalisation of the Cu response over that of DO as the response was related to diffusion through the electrode surface which was similarly affected. The detected fraction of Cu (labile Cu) amounted to 1.5-4 nM during different deployments at a total Cu concentration of ∼10 nM. The same ratio was found by voltammetry in samples taken to the laboratory. The new apparatus has demonstrated that metals in coastal waters can be monitored at trace level, much facilitating the monitoring of outfalls and local water contamination. Because of its sensitivity the apparatus would be of use in estuarine as well as coastal waters, with the aim of monitoring intermittent variability in the copper concentration.

The role of natural zeolite and of two types of modified zeolite (with ammonium and with calcium ions) in reducing the accumulation of ions of heavy metals in roots and leaves of Hieracium piloselloides grown on tailing ponds was investigated. The variation of the content of zeolite (5% w/w and 10% w/w) is another parameter that significantly and positively affects the accumulation of the metal ions in Hieracium piloselloides. The results showed that zeolite used as an amendment in the soil in tailing ponds significantly reduces the accumulation of heavy metal ions in Hieracium piloselloides. The highest concentrations of heavy metals were accumulated in plants grown on soil without zeolite, being followed by the plants grown on the substrate with natural zeolite. Moreover, the translocation factors of heavy metal ions uptake in roots and leaves grown on substrates with modified zeolites are lower than those calculated for the organs grown on the substrate amended with natural zeolite. This behaviour has demonstrated the positive effect of those changes of zeolite amendments in the potential phytoremediation practice.

A total of 55 samples including soil, sediment, plants (cypress, reed and seepweed) and aquatic species were collected at locations around hexabromocyclododecane (HBCD) manufacturing facilities in Laizhou Bay area, East China. HBCD was determined at concentrations ranging between 0.88 and 6901 ng g(-1) dry weight (dw), 2.93-1029 ng g(-1) dw, 8.88-160241 ng g(-1) dw, and 7.09-815 ng g(-1) lipid weight (lw), respectively. Significant negative correlations (r(2) = 0.54, p = 0.006) were observed between HBCD concentrations in soils and the distance from the manufacturing facility, and the concentrations became constant when the distance was >4 km. The calculation results on the bioaccumulation factors (BAFs) suggested that HBCD may be accumulated in plants. Tissue-specific bioaccumulation of HBCD diastereoisomers was found in aquatic species. For example, in crabs the highest concentrations of HBCD (815 ng g(-1) lw for female and 446 ng g(-1) lw for male) were observed in the gill. Besides the gill, α-HBCD was more preferentially accumulated in the spermary and ovary, while β- and γ-HBCD were more accumulated in the muscle. A similar distribution was also observed in roe and muscle of goby fish.

Understanding the cause of effluent toxicity is an important requirement for its prevention, remediation and return to compliance. One component of the strategy entails identification and fingerprinting of additives or components in additives that may be the cause of the toxicity episodes. A number of additives used in pulp and papermaking are polymeric compounds that are suspect in effluent toxicity. Their analysis and detection is difficult as they are not amenable to analysis by normal techniques applicable to mill effluents such as gas chromatography. Py-GC/MS is a powerful analytical technique that can be used to fingerprint these additives. The presence of the additives is confirmed by fingerprint pyrograms of the additives (or components in the formulations of the additives) in conjunction with mass spectrometry. The technique has been used to fingerprint and quantify polymeric additives associated with mill effluent toxicity episodes.

Previous studies indicated that Environmentally Persistent Free Radicals (EPFRs) are formed in the post-flame, cool zone of combustion. They result from the chemisorption of gas-phase products of incomplete combustion (particularly hydroxyl- and chlorine-substituted aromatics) on Cu(II)O, Fe(III)(2)O(3), and Ni(II)O domains of particulate matter (fly ash or soot particles). This study reports our detailed laboratory investigation on the lifetime of EPFRs on Zn(II)O/silica surface. Similarly, as in the case of other transition metals, chemisorption of the adsorbate on the Zn(II)O surface and subsequent transfer of electron from the adsorbate to the metal forms a surface-bound EPFR and a reduced metal ion center. The EPFRs are stabilized by their interaction with the metal oxide domain surface. The half-lives of EPFRs formed on Zn(II)O domains were the longest observed among the transition metal oxides studied and ranged from 3 to 73 days. These half-lives were an order of magnitude longer than those formed on nickel and iron oxides, and were 2 orders of magnitude longer compared to the EPFRs on copper oxide which have half-lives only on the order of hours. The longest-lived radicals on Zn(II)O correspond to the persistency in ambient air particles of almost a year. The half-life of EPFRs was found to correlate with the standard reduction potential of the associated metal.

Two sediment cores were collected from Hailing Bay located in a typical mariculture zone of Guangdong Province, South China, and analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of the sum of 27 PAHs ranged from 62 to 1200 ng g(-1) dry wt, and sediment in the study area was considered to be moderately polluted by PAHs. Source diagnostics based on PAH composition and principal component analysis suggested that PAHs in the study area were mainly derived from petroleum combustion, with discharge of PAHs from fishing boats as an important source. Ecological risk assessment results indicate that PAHs in sediment of the present study currently have minimal adverse effect on the mariculture environment. Comparison of sedimentary inventory of PAHs in the fish harbor of the study area with those in the Pearl River Estuary and the coastal Bohai Bay indicate that the sediment has become an important reservoir of PAHs.