Macrobenthic community in the Douro estuary: relations with trace metals and natural sediment characteristics

The relationship between macrobenthic community structure and natural characteristics of sediment and trace metal contamination were studied in the lower Douro estuary (Portugal, NW, Iberian Peninsula), using an innovative threefold approach (SQG, Sediment Quality Guidelines), metal normalization to Fe, and macrobenthic community structure. This study allowed detection of a clear signature of anthropogenic contamination, in terms of Zn, Cu, Pb, and Cr in the north bank of the estuary, which experiences high urban pressure. Using the SQG approach, metal concentrations above ERM (effects range-median) were observed only at one sampling station, but several stations had levels above ERL (effects range-low). The macrobenthic community had a low diversity, with only 19 species found in the entire estuarine area, dominated by opportunistic species. The granulometric distribution of the sediments (estimated from the combination of organic matter, Fe and Al) seemed to be the major structuring factor for the communities, establishing the natural macrobenthic distribution pattern. The metals (Zn, Cu, Pb, and Cr) seemed to act as a disturbing factor over the natural distribution, with deleterious consequences for the macrobenthic communities.     

Understanding the effectiveness of precursor reductions in lowering 8-hr ozone concentrations

Analyses of ambient measured ozone data were used in conjunction with the application of photochemical modeling to determine the technical feasibility of attaining the federal 8-hr ozone standard in central California. Various combinations of volatile organic compound (VOC) and oxides of nitrogen (NOx) emission reductions were effective in lowering modeled peak 1-hr ozone concentrations. However, VOC emissions reductions were found to have only a modest impact on modeled peak 8-hr ozone concentrations. NOx emission reductions generally lowered 8-hr ozone concentrations, but their effectiveness was partially or, in some cases, wholly offset by the increase in the number of NO cycles and, hence, in the ozone produced per NO. As a result, substantial NOx emission reductions--70 to 90%--were required to reduce peak 8-hr ozone concentrations to the level of the standard throughout the modeling domain. These modeling results provide a possible physical explanation for recent analyses that have reported more prominent trends in peak 1-hr ozone levels than in peak 8-hr ozone concentrations or in occurrences of mid-level (60-90 parts per billion by volume) ozone concentrations. The findings also have serious implications for the feasibility of attaining the 8-hr ozone standard in central California. Further efforts are needed to clarify the applicability of the modeling results to the full set of days with ozone levels exceeding the 8-hr ozone standard, as well as their applicability to other geographical areas.     

Sorption of As(V) ions by akaganéite-type nanocrystals

A priority pollution problem, the removal of arsenate oxyanions from dilute aqueous solutions by sorption onto synthetic akaganéite (beta-FeO(OH)) was the aim of the present study. This is an innovative inorganic adsorbent material prepared in the laboratory, following a new method of preparation. The effect of akaganéite and arsenate concentration, the contact time, temperature, solution pH value, and ionic strength variation on the treatment process was mainly investigated during this study. Typical adsorption isotherms were determined, which were found to fit sufficiently the typical Langmuir equation. The mechanism of sorption was examined by electrokinetic, X-ray diffraction, Fourier transmission infrared and scanning electron microscopy measurements. Promising results were obtained, due to the favourite characteristics of the adsorbent applied.     

Antimony bioavailability in mine soils

Five British former mining and smelting sites were investigated and found to have levels of total Sb of up to 700 mg kg(-1), indicating high levels of contamination which could be potentially harmful. However, this level of Sb was found to be biologically unavailable over a wide range of pH values, indicating that Sb is relatively unreactive and immobile in the surface layers of the soil, remaining where it is deposited rather than leaching into lower horizons and contaminating ground water. Sb, sparingly soluble in water, was unavailable to the bacterial biosensors tested. The bioluminescence responses were correlated to levels of co-contaminants such as arsenic and copper, rather than to Sb concentrations. This suggests that soil contamination by Sb due to mining and smelting operations is not a severe risk to the environment or human health provided that it is present as immobile species and contaminated sites are not used for purposes which increase the threat of exposure to identified receptors. Co-contaminants such as arsenic and copper are more bioavailable and may therefore be seen as a more significant risk.     

Behaviour of forchlorfenuron residues in grape,soil and water

Persistence of forchlorfenuron residues in grape berries at harvest following its dip application as single or split doses to grape berry clusters and periodic dissipation of forchlorfenuron residues in grape berries following foliar spray application were studied. Periodic dissipation of forchlorfenuron residues following its fortification in soil and water were also studied. Splitting the dip application concentration of forchlorfenuron to grape berries reduced its residues in the berries at harvest, which persisted for more than 65 days from all treatments. In case of foliar application, however, the residues of forchlorfenuron in/on the grape berries persisted for 15-20 days only from three treatment concentrations of 2, 3 and 4 ml/l and dissipated with half-lives of 3.4-4.5 days. The residues of forchlorfenuron dissipated faster in soils maintained at field capacity moisture condition than in air dry soils. There was wide variation in its residue persistence in soil (DT50 = 15.1-121.3 days) depending on soil type and moisture condition. Forchlorfenuron residues persisted for more than 30 days in water and its dissipation was fastest at a water salinity level of 3.85 mmho/ cm although the rate of dissipation was not significantly affected by the change in salinity level from <0.04 to 5.90 mmho/cm.     

Multivariate statistical study of heavy metal enrichment in sediments of the Pearl River Estuary

The concentrations and chemical partitioning of heavy metals in the sediment cores of the Pearl River Estuary were studied. Based on Pearson correlation coefficients and principal component analysis results, Al was selected as the concentration normalizer for Pb, while Fe was used as the normalizing element for Co, Cu, Ni and Zn. In each profile, sections with metal concentrations exceeding the upper 95% prediction interval of the linear regression model were regarded as metal enrichment layers. The heavy metal accumulation mainly occurred at sites in the western shallow water areas and east channel, which reflected the hydraulic conditions and influence from riparian anthropogenic activities. Heavy metals in the enrichment sections were evaluated by a sequential extraction method for possible chemical forms in sediments. Since the residual, Fe/Mn oxides and organic/sulfide fractions were dominant geochemical phases in the enriched sections, the bioavailability of heavy metals in sediments was generally low. The 206Pb/207Pb ratios in the metal-enriched sediment sections also revealed the influence of anthropogenic sources. The spatial distribution of cumulative heavy metals in the sediments suggested that the Zn and Cu mainly originated from point sources, while the Pb probably came from non-point sources in the estuary.     

Source identification of atlanta aerosol by positive matrix factorization

Data characterizing daily integrated particulate matter (PM) samples collected at the Jefferson Street monitoring site in Atlanta, GA, were analyzed through the application of a bilinear positive matrix factorization (PMF) model. A total of 662 samples and 26 variables were used for fine particle (particles < or = 2.5 microm in aerodynamic diameter) samples (PM2.5), and 685 samples and 15 variables were used for coarse particle (particles between 2.5 and 10 microm in aerodynamic diameter) samples (PM10-2.5). Measured PM mass concentrations and compositional data were used as independent variables. To obtain the quantitative contributions for each source, the factors were normalized using PMF-apportioned mass concentrations. For fine particle data, eight sources were identified: SO4(2-) -rich secondary aerosol (56%), motor vehicle (22%), wood smoke (11%), NO(3-) -rich secondary aerosol (7%), mixed source of cement kiln and organic carbon (OC) (2%), airborne soil (1%), metal recycling facility (0.5%), and mixed source of bus station and metal processing (0.3%). The SO4(2-) -rich and NO(3-) -rich secondary aerosols were associated with NH(4+). The SO4(2-) -rich secondary aerosols also included OC. For the coarse particle data, five sources contributed to the observed mass: airborne soil (60%), NO(3-)-rich secondary aerosol (16%), SO4(2-) -rich secondary aerosol (12%), cement kiln (11%), and metal recycling facility (1%). Conditional probability functions were computed using surface wind data and identified mass contributions from each source. The results of this analysis agreed well with the locations of known local point sources.     

Removal of biocide pentachlorophenol in water system by the spent mushroom compost of Pleurotus pulmonarius

Pentachlorophenol (PCP) has been widely used as a wood preservative since 1980s. Although it has been banned worldwide, residues of PCP are still commonly found. The spent compost of oyster mushroom Pleurotus pulmonarius (SMC) which was a degraded paddy straw-based substrate, contained 25% chitin. Five percentage of the SMC could remove 89.0 +/- 0.4% of 100 mg PCPl(-1) within 2 days at room temperature predominantly by biodegradation. The maximum removal capacity was 15.5 +/- 1.0 mg g(-1) SMC. The sorption kinetics of PCP by SMC can be described by the Freundlich monolayer model with a theoretical sorption capacity similar to that found for chitin. A PCP-degradative bacterium was isolated from the SMC. Yet, biodegradation was predominantly contributed by the immobilized ligninolytic enzymes secreted by the mushroom to the SMC. Degradation of PCP involves dechlorination, methylation, carboxylation and ring cleavage as verified by GC-MSD and ion chromatography. Thus, the SMC has a potential for treating PCP-contaminated water.     

Use of spent mushroom compost to bioremediate PAH-contaminated samples

Spent mushroom compost (SMC) is a bulky waste byproduct of mushroom industry and produced abundantly. The SMC of Pleurotus pulmonarius immobilized laccase (0.88 mmoles min(-1) g(-1)) and manganese peroxidase (0.58 mmoles min(-1) g(-1)) of which the optimal temperatures were 45 and 75 degrees C, respectively. In laboratory test, complete degradative removal of individual naphthalene, phenanthrene, benzo[a]pyrene and benzo[g,h,i]perylene (200 mg PAH kg(-1) sandy-loam soil) by 5% SMC was obtained in two days under continuous shaking at 80 degrees C. The SMC-treated PAH samples had significantly reduced or removed their toxicities as revealed by the Microtox bioassay. These results were confirmed by gas chromatography-mass spectrometry analysis on the breakdown products. A phthalic derivative which is reported as a degradative product of PAHs by ozonation or ligninolysis was also detected in the SMC-treated samples. The results demonstrate the potential in employing SMC in ex situ bioremediation.     

Plant uptake and translocation of air-borne chlordane and comparison with the soil-to-plant route

In order to assess fully the impact of persistent organic pollutants (POPs) on human health, pollutant exchange at the interface between terrestrial plants, in particular food crops, and other environmental compartments must be thoroughly understood. In this regard, transfers of multicomponent and chiral pollutants are particularly informative. In the present study, zucchini (Cucurbita pepo L.) was planted in containerized, uncontaminated soil under both greenhouse and field conditions and exposed to air-borne chlordane contamination at 14.0 and 0.20 ng/m(3) (average, greenhouses), and 2.2 ng/m(3) (average, field). Chiral gas chromatography interfaced to an ion trap mass spectrometer was used to determine the chiral (trans-chlordane, TC, and cis-chlordane, CC) and achiral (trans-nonachlor, TN) chlordane components in vegetation, air, and soil compartments. The chlordane components of interest were detected in all vegetation tissues examined--root, stem, leaves, and fruits. When compared with the data from a soil-to-plant uptake study, the compositional profile of the chlordane components, i.e. the component fractions of TC, CC, and TN, in plant tissues, showed significantly different patterns between the air-to-plant and soil-to-plant pathways. Changes in the enantiomer fractions of TC and CC in plant tissues relative to the source, i.e. air or soil, although observed, were not markedly different between the two routes. This report provides the first comprehensive comparison between two distinct plant uptake routes for POPs and their subsequent translocation within plant tissues.