PCDD/F-contamination in a hexachlorocyclohexane waste site in Rio de Janeiro,Brazil

In the 1950s, a production plant of hexachlorocyclohexane (HCH) was established in Brazil with the main purpose of producing chemicals for vectors control. This factory was closed down in 1955 and around 300 tons of production residues were left behind in the open air. In 1995, the area was treated with lime to eliminate the HCH contamination. Soil sample gave a PCDD/F concentration of 13 900 ng I-TEQ/kg whereas samples from the neighborhood ranged from 0.19 to 2.08 ng I-TEQ/kg. PCDD/F levels in cow's milk samples varied from 4.1 to 6.5 pg I-TEQ/g of milk fat. High concentration in soil collected from the site suggests that treatment and recovery shall be made. Further dioxin monitoring is needed to better estimate the risk posed to local population through food consumption and soil usage.     

Residual gasoline saturation in unsaturated soil with and without organic matter

The goal of this study was to investigate the influence of one variable, natural organic matter, on residual gasoline saturation in sandy soils. Capillary pressure-saturation (P_c−S) relationships (air-gasoline) were determined for three physically-similar sandy soils, with different organic carbon contents (0.086%, 0.89% and 1.65%) and residual gasoline saturations were compared. Two initial moisture conditions, residual water saturation and air-dry, were evaluated. One soil type was packed to two different bulk densities. Visualization of the soils using cryo-scanning electron microscopy was performed to aid in better understanding the role of the organic matter in the soil. The results showed that soils with higher organic contents had higher residual gasoline saturations when starting with an initially air-dry soil. Increasing the bulk density of the same air-dried soil resulted in an increase in residual gasoline saturation. In the presence of a residual water saturation, however, residual gasoline saturations were virtually identical for the three soils and independent of bulk density; approximately 5–10 times lower than in soil that was initially air-dry. The presence of the residual water effectively coated the surface of the soil thereby reducing or eliminating gasoline/soil interactions. Some residual water may also be occupying very small pore spaces, making these locations inaccessible to the gasoline.     

Responses of three grass species to creosote during phytoremediation

Phytoremediation of creosote-contaminated soil was monitored in the presence of Tall fescue, Kentucky blue grass, or Wild rye. For all three grass species, plant growth promoting rhizobacteria (PGPR) were evaluated for plant growth promotion and protection of plants from contaminant toxicity. A number of parameters were monitored including plant tissue water content, root growth, plant chlorophyll content and the chlorophyll a/b ratio. The observed physiological data indicate that some plants mitigated the toxic effects of contaminants. In addition, in agreement with our previous experiments reported in the accompanying paper (Huang, X.-D., El-Alawi, Y., Penrose, D.M., Glick, B.R., Greenberg, B.M., 2004. A multi-process phytoremediation system for removal of polycyclic aromatic hydrocarbons from contaminated soil. Environ. Poll. doi: 10.1016/j.envpol.2003.09.031), PGPR were able to greatly enhance phytoremediation. PGPR accelerated plant growth, especially roots, in heavily contaminated soils, diminishing the toxic effects of contaminants to plants. Thus, the increased root biomass in PGPR-treated plants led to more effective remediation.     

Assessment of interfacial mass transfer in water-unsaturated soils during vapor extraction

This paper presents results of a numerical investigation of soil vapor extraction (SVE) systems at the laboratory scale. The SVE technique is used to remove volatile chlorinated hydrocarbons (VCHC) from the water-unsaturated soil zone. The developed numerical model solves equations of flow, transport and interfacial mass transfer regarding an isothermal n-component and three-phase system. The mathematical model is based on a simple pore network and phase distribution model and designed to be scaled by a characteristic length. All mathematical expressions are structured into VCHC specific and VCHC non-specific parameters. Furthermore, indicators are introduced that help to separate thermodynamic equilibrium from thermodynamic non-equilibrium domains and to determine the controlling physical parameters. For numerical solution, the system of partial differential equations is discretized by a finite volume method and an implicit Euler time stepping scheme. Computational effort is reduced notably through techniques that enable spatial and temporal adaptivity, through a standard multigrid method as well as through a problem-oriented sparse-matrix storage concept. Computations are carried out in two dimensions regarding the laboratory experiment of Fischer et al. [Water Resour. Res. 32 (12) 1996 3413]. By varying the characteristic length scale of the pore network and phase distribution model, it is shown that the experimental gas phase concentrations cannot be explained only by the volatility and diffusivity of the VCHC. The computational results suggest a sorption process whose significance grows with the aqueous activity of the less or non-polar organic compounds.     

Estimating erosion in a riverine watershed bayou liberty-tchefuncta river in louisiana

GOAL, SCOPE, BACKGROUND: Sheet erosion from agricultural, forest and urban lands may increase stream sediment loads as well as transport other pollutants that adversely affect water quality, reduce agricultural and forest production, and increase infrastructure maintenance costs. This study uses spatial analysis techniques and a numerical modeling approach to predict areas with the greatest sheet erosion potential given different soils disturbance scenarios. METHODS: A Geographic Information System (GIS) and the Universal Soil Loss Equation (USLE) were used to estimate sheet erosion from 0.64 ha parcels of land within the watershed. The Soil Survey of St. Tammany Parish, Louisiana was digitized, required soil attributes entered into the GIS database, and slope factors determined for each 80 x 80 meter parcel in the watershed. The GIS/USLE model used series-specific erosion K factors, a rainfall factor of 89, and a GIS database of scenario-driven cropping and erosion control practice factors to estimate potential soil loss due to sheet erosion. RESULTS AND DISCUSSION: A general trend of increased potential sheet erosion occurred for all land use categories (urban, agriculture/grasslands, forests) as soil disturbance increases from cropping, logging and construction activities. Modeling indicated that rapidly growing urban areas have the greatest potential for sheet erosion. Evergreen and mixed forests (production forest) had lower sheet erosion potentials; with deciduous forests (mostly riparian) having the least sheet erosion potential. Erosion estimates from construction activities may be overestimated because of the value chosen for the erosion control practice factor. CONCLUSIONS: This study illustrates the ease with which GIS can be integrated with the Universal Soil Loss Equation to identify areas with high sheet erosion potential for large scale management and policy decision making. RECOMMENDATIONS: The GIS/USLE modeling approach used in this study offers a quick and inexpensive tool for estimating sheet erosion within watersheds using publicly available information. This method can quickly identify discrete locations with relatively precise spatial boundaries (approximately 80 meter resolution) that have a high sheet erosion potential as well as areas where management interventions might be appropriate to prevent or ameliorate erosion.     

Fine structure and X-ray microanalysis of a red macrophyte cultured under cadmium stress

Thalli of the red alga Audouinella saviana were exposed to 600 microM Cd2+ (LC50), 1000 microM Cd2+ and 1500 microM Cd2+ (final concentrations) for 5, 10 and 15 days (each dose) by adding cadmium nitrate to the culture medium. Untreated thalli were set in triplicate as controls for each experiment. Ultrastructural modifications due to cadmium ad/absorption were observed by TEM/SEM electron microscopy. SEM-EDS X-ray microanalysis, definining the accumulation sites, was performed on cryoprepared samples. TEM studies showed striking changes in the plasmalemma of treated algae, which became irregular and convoluted. Electron-transparent exocytic vesicles, possibly related to cell wall polysaccharide synthesis, were observed. The appearance of ribosomes and Golgi bodies, not significantly present in the cytoplasms of untreated cells, suggested enhanced protein and carbohydrate biosynthesis. The cell walls lost their initial grooves and became smooth and thick. More or less electron-dense vesicular systems were formed. Electron-dense sphaeroids occurred in the plasmalemma-cell wall interface, in the cell wall itself and in nearby vesicular membrane systems. Many small vacuoles containing large metal complexes were formed. Complexes were then sequestered into a large vacuole. SEM observations demonstrated that the cell wall and the membrane systems were the most involved in the defense responses. EDS-X-ray microanalysis confirmed the presence of cadmium in these compartments. Chloroplasts, where no Cd2+ signal was detected, were the least affected organelles, showing only a partial disorganization after lengthy exposure to high Cd2+ concentrations.     

浙江省近岸海域一次特大面积赤潮的剖析

通过对发生在浙江省近岸海域一次特大面积赤潮的剖析，阐述了赤潮造成的危害，探索了赤潮爆发的原因，最后还对如何防落赤潮提出了对策措施。     

Unidirectional gas flow in soil porosity resulting from barometric pressure cycles

During numerical simulation of air flow in the vadose zone, it was noticed that a small sinusoidal pressure would cause a gradual one-way migration of the pore gas. This was found to be a physical phenomenon, not a numerical artifact of the finite element simulation. The one-way migration occurs because the atmospheric pressure, and hence the air density, is slightly greater when air is flowing into the ground than when air is flowing out of the ground. A simple analytic theory of the phenomenon is presented, together with analytic calculations using actual barometric pressure data. In soil of one Darcy permeability, the one-way migration is of the order of a few tenths of a meter per year for either plane flow from ground surface or for radial flow from an open borehole. The migration is sufficiently small that it will have no practical consequences in most circumstances; however, investigators who conduct detailed numerical modeling should recognize that this phenomenon is not a numerical artifact in an apparently linear system.     

硼泥浸提实验研究

硼泥为工业废渣之一，对环境的危害极大。在对某地硼泥进行矿物分析、化学分析和浸提实验的基础上，系统研究了硼泥中元素的释放规律和Ｂ在土壤中的迁移转化及对作物的危害。结果发现硼泥对环境的危害主要是其淋溶水中的Ｂ、Ｎａ含量及ｐＨ值过高造成的。     

Survey of dioxin sources in the Baltic Region (extended summary)

The present paper summarises the results of the project: 'Survey of Anthropogenic Sources of Dioxins and Furans in the Baltic Region'. As a part of the project, inventories have been carried out in Estonia, Latvia, Lithuania and Poland by applying the toolkit for quantification of dioxin and furan releases developed by UNEP Chemicals. The main route of direct releases to the environment is emission to air. Total emission to air from Poland was estimated at 490 (88-1,300) g I-TEQ/year, whereas the emissions from Estonia, Latvia and Lithuania were estimated as being 14 (2.4-54), 23 (2.6-63) and 17 (2.6-38) g I-TEQ, respectively. In general, the uncertainty on the estimates is very high, and recommendations regarding further development of the inventories have been made, and measures for reducing the releases have been provided.