Changes of copper speciation in maize rhizosphere soil

Chemical forms of copper in the rhizosphere and bulk soil of maize were investigated using rhizobox cultivation and sequential extraction techniques. The copper accumulations were also determined. The results demonstrated that there were continuous changes in copper fractionation within the maize rhizosphere. Initially, the amount of exchangeable copper increased before dropping below the initial level after 40 days or so. Carbonate associated copper followed a similar trend of change, but with a slower pace than the exchangeable copper. The increase in carbonate associated copper only become evident after 30 days, with the net loss occurring after 60 days. There were also initial increases in oxide bound copper as well as decreases in the organic matter associated copper, both followed by a turnover after 40-50 days. The accumulation of copper in the maize plant was found to be biomass dependent. The amount of accumulated copper absorbed in the plant material exceeded the initial quantity of the exchangeable copper in the soil, revealing a transformation from less bioavailable to more bioavailable fractions. During cultivation, decreases in redox potential and increases in pH, dissolved organic carbon (DOC), and microbial activity in the maize rhizosphere were observed. The change in copper speciation may result from root-induced changes in DOC, redox potential, and microbial activity in the rhizosphere.     

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.     

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.     

AFLP analysis as biomarker of exposure to organic and inorganic genotoxic substances in plants

In recent years several plant species have been in use as bioindicators and several tests have been developed to evaluate the toxicity of environmental pollutants in vegetal organisms. In the present paper Arabidopsis thaliana (L.) Heynh. (ecotype Wassilewskija) was used as bioindicators of two genotoxic substances: potassium dichromate and dihydrophenanthrene. Inhibition of seed germination was observed with both pollutants. AFLP analysis (i) indicated that both substances are genotoxic, (ii) showed that dihydrophenanthrene induces DNA changes in different target sequences than potassium dichromate, (iii) quantified the genotoxic effect using cluster analysis by comparing DNA from treated plants with that of control plants. On the basis of these considerations we suggest that AFLP method is a powerful tool for measuring qualitative and quantitative genotoxic activity due to environmental pollutants. AFLP method can be applied to a wide range of bioindicator organisms and may become a universal methodology to identify target genes for specific genotoxic agents. This could open up possibilities for designing specifically targeted assays and new approaches to risk assessment.     

Geochemical evidences of the anthropogenic alteration of trace metal composition of the sediments of Chiricahueto marsh (SE Gulf of California)

Seven sediment cores (60-80 cm) were collected at Chiricahueto marsh, a salt marsh influenced by agrochemical, domestic and industrial effluents. The concentrations of Ag, Al, Cd, Co, Cu, Fe, Li, Mn, Pb, V and Zn were studied in the solid phase at each 1-cm section. The profiles of Ag, Cd, Cu, Mn, Ni, Pb and Zn showed a slight recent pollution in the site with enrichment and anthropogenic factors higher than unity; and correlation analysis indicated a direct association with organic carbon. Al, Co, Cr, Fe, Li, and V concentration profiles displayed a negative correlation with organic C and positive with mud content and no consistent enrichment at surface. Based on the principal component analysis and correlation analysis, two principal groups of metals were identified. The first group includes Al, Co, Cr, Fe and Li, that are derived predominantly from the weathering of parent materials in the local bedrock; and the second group include most of the metals, which were relatively enriched at surficial sediments, that are produced mainly by anthropogenic activities such as agriculture (Cd, Cu and Zn), sewage effluents (Ag, Cd, Cu, Ni, Pb and Zn) and in lesser extent atmospheric deposition (Cd and Pb).     

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.     

Zingiberene and curcumene in wild tomato

Composition of ginger oil prepared from fresh ginger rhizomes, Zingiber officinale Roscoe (Zingiberaceae) was determined by gas chromatography (GC) and GC-mass spectrometric techniques. The main sesquiterpene hydrocarbons identified were alpha-zingiberene (27-30%), alpha-curcumene (8-9%), beta-sesquiphellandrene (4.8%). and bisabolene (3.2%). The function of zingiberene and curcumene as insecticides, repellents, and insect feeding deterrents has been previously reported. Other plant species having similar constituents might be found. Leaves of six wild tomato accessions of Lycopersicon hirsutum f. glabratum (Mull); three accessions of L. hirsutum f. typicum (Humb & Bonpl.); two accessions of L. pennellii Corr. (D'Arcy); one accession of L. pimpinellifolium; and one commercial tomato L. esculentumm cv. Fabulous were analyzed. Analysis of L. hirsutum f. typicum (Solanaceae) accessions indicated the presence of zingiberene, curcumene, and other lipophilic secondary metabolites in the leaves of two accessions (PI-127826 and PI-127827). An average three month old wild tomato plant of accessions PI-127826 and PI-127827 provided 1.93 and 1.30 kg fresh leaves (averaging about 38,307 and 28,130 cm2 exposed leaf surface area, respectively) and produced 19.3 and 10.1 g of zingiberene and curcumene (PI-127826) and 17.2 and 1.8 g of zingiberene and curcumene (PI-127827), respectively. Leaf extracts of the wild tomato L. hirsutum f. typicum (accessions PI-127826 and PI-127827) can be used as a biorational source of zingiberene and curcumene.     

Fate and assessment of persistent organic pollutants in water and sediment from Minjiang River Estuary,Southeast China

Persistent organochlorine compounds were analyzed in surface water, porewater and surficial sediment samples from Minjiang River Estuary, which is the first large river in Fujian Province, Southeast of China. The total concentrations of 18 organochlorine pesticides were 214.4-1819, 4541-13,699 ng/l, 28.79-52.07 ng/g in surface water, porewater and sediments (dry weight) respectively, and those of 21 polychlorinated biphenyls (PCBs) in the three phases were: 203.9-2473, 3192-10,855 ng/l, 15.14-57.93 ng/g respectively. The results showed that the concentrations of these selected organochlorine pesticides and PCBs in porewater were higher than those in surface water. It may be due to the fact that these organic hydrophobic pollutants tend to stay in the sediments, and then re-suspend from the sedimentary phase to the upper water. We have analyzed the distribution characteristics of individual organochlorine pesticide components and PCBs, and found that alpha-HCH, DDE, Heptachlor, Endosulfan II, Methoxychlor were the most common organochlorine pesticides contaminants. Considering the groups of HCHs (HCHs=alpha-HCH+beta-HCH+gamma-HCH+delta-HCH) and DDTs (DDTs=DDT+DDD+DDE), the predominance of beta-HCH, DDE in all water, porewater and sediment samples was clearly observed. This observation suggested that beta-HCH was resistant to biodegradation and the DDTs had been transformed to its metabolites, DDE and DDD, of which DDE that was more un-degradable. The PCB congeners containing 3-6 chlorines had the great preponderance in the three phase. These results were compared with those present in other estuaries and harbors. A risk assessment was evaluated for the persistent organic pollutants in the Minjiang River Estuary.