Studies on the sources of benzo[a]pyrene in grain and aboveground tissues of rice plants.

Rice plant pot experiments designed to identify benzo[a]pyrene (B[a]P) sources in plant tissues were conducted in an air-quality controlled greenhouse built to prevent contamination from B[a]P air pollution. Results from quartz sand cultures with control and 50, 100 and 500 microgkg(-1) of B[a]P treatments were compared with those from outdoor field experiments, in which rice plants were exposed to polluted air in the urban area of Shenyang, China. When B[a]P was strictly controlled in both air and quartz sand culture medium, the background values of B[a]P in rice plant tissues were uniformly very low. There was no significant difference of B[a]P contents of rice grain between control and treatments of B[a]P in controlled air quality trials. This indicated that the source of B[a]P in the rice grains is not from any B[a]P in the root culture media. The B[a]P content of rice grain, husk, and stem with leaf sampled from outdoor field was up to 7.33-, 9.21- and 27.10-fold higher than corresponding tissues from air-quality controlled conditions. This indicated that polluted air is the main source of B[a]P in aboveground tissues. Therefore control of B[a]P pollution in ambient air is of prime importance for improving the quality of cereal crops.

Quantifying effects of soil heterogeneity on groundwater pollution at four sites in USA.

Four sites located in the north-eastern region of the United States of America have been chosen to investigate the impacts of soil heterogeneity in the transport of solutes (bromide and chloride) through the vadose zone (the zone in the soil that lies below the root zone and above the permanent saturated groundwater). A recently proposed mathematical model based on the cumulative beta distribution has been deployed to compare and contrast the regions' heterogeneity from multiple sample percolation experiments. Significant differences in patterns of solute leaching were observed even over a small spatial scale, indicating that traditional sampling methods for solute transport, for example the gravity pan or suction lysimeters, or more recent inventions such as the multiple sample percolation systems may not be effective in estimating solute fluxes in soils when a significant degree of soil heterogeneity is present. Consequently, ignoring soil heterogeneity in solute transport studies will likely result in under- or overprediction of leached fluxes and potentially lead to serious pollution of soils and/or groundwater. The cumulative beta distribution technique is found to be a versatile and simple technique of gaining valuable information regarding soil heterogeneity effects on solute transport. It is also an excellent tool for guiding future decisions of experimental designs particularly in regard to the number of samples within one site and the number of sampling locations between sites required to obtain a representative estimate of field solute or drainage flux.

Spatial and temporal distribution of solute leaching in heterogeneous soils: analysis and application to multisampler lysimeter data.

Accurate assessment of the fate of salts, nutrients, and pollutants in natural, heterogeneous soils requires a proper quantification of both spatial and temporal solute spreading during solute movement. The number of experiments with multisampler devices that measure solute leaching as a function of space and time is increasing. The breakthrough curve (BTC) can characterize the temporal aspect of solute leaching, and recently the spatial solute distribution curve (SSDC) was introduced to describe the spatial solute distribution. We combined and extended both concepts to develop a tool for the comprehensive analysis of the full spatio-temporal behavior of solute leaching. The sampling locations are ranked in order of descending amount of total leaching (defined as the cumulative leaching from an individual compartment at the end of the experiment), thus collapsing both spatial axes of the sampling plane into one. The leaching process can then be described by a curved surface that is a function of the single spatial coordinate and time. This leaching surface is scaled to integrate to unity, and termed S can efficiently represent data from multisampler solute transport experiments or simulation results from multidimensional solute transport models. The mathematical relationships between the scaled leaching surface S, the BTC, and the SSDC are established. Any desired characteristic of the leaching process can be derived from S. The analysis was applied to a chloride leaching experiment on a lysimeter with 300 drainage compartments of 25 cm2 each. The sandy soil monolith in the lysimeter exhibited fingered flow in the water-repellent top layer. The observed S demonstrated the absence of a sharp separation between fingers and dry areas, owing to diverging flow in the wettable soil below the fingers. Times-to-peak, maximum solute fluxes, and total leaching varied more in high-leaching than in low-leaching compartments. This suggests a stochastic-convective transport process in the high-flow streamtubes, while convection dispersion is predominant in the low-flow areas. S can be viewed as a bivariate probability density function. Its marginal distributions are the BTC of all sampling locations combined, and the SSDC of cumulative solute leaching at the end of the experiment. The observed S cannot be represented by assuming complete independence between its marginal distributions, indicating that S contains information about the leaching process that cannot be derived from the combination of the BTC and the SSDC.

Effects of sulfur dioxide pollution on the translocation and accumulation of heavy metals in soybean grain.

BACKGROUND: Open-top chambers were used to study the impact of simultaneous exposure to atmospheric SO(2) pollution and heavy metal contamination in soils on the metal contents and productivity of soybean plant. METHODS: Plants were exposed at ambient levels as control SO(2) (1.2 ppb), low SO(2) (97 ppb), and high SO(2) (490 ppb) over the whole growing season while simultaneously being exposed to either Cd (0.5 mg kg(-1)), Pb (250 mg kg(-1)), Cu (100 mg kg(-1)), or Zn (150 mg kg(-1)) in soil. RESULTS: This experimental study covering the whole growth season has shown that SO(2) has a synergistic effect in enhancing the heavy metal contents in aboveground tissues of soybean plant, and the effects of high SO(2) treatment were found to be highly significant, showing increases of 42% and 29% for Cu and Cd content of grain, respectively. CONCLUSION: The research findings are of practical significance in the environmental control for the combined pollution of air and soil to ensure the quality of agricultural products and therefore benefits for human health.

Biological toxicity of lanthanide elements on algae.

The biological toxicity of lanthanides on marine monocellular algae was investigated. The specific objective of this research was to establish the relationship between the abundance in the seawater of lanthanides and their biological toxicities on marine monocellular algae. The results showed that all single lanthanides had similar toxic effects on Skeletonema costatum. High concentrations of lanthanides (29.04+/-0.61 micromol L(-1)) resulted in 50% reduction in growth of algae compared to the controls (0 micromol L(-1)) after 96 h (96 h-EC50). The biological toxicity of 13 lanthanides on marine monocellular algae was unrelated with the abundance of different lanthanide elements in nature, and the "Harkins rule" was not appropriate for the lanthanides. A mixed solution that contained equivalent concentrations of each lanthanide element had the same inhibition effect on algae cells as each individual lanthanide element at the same total concentration. This phenomenon is unique compared to the groups of other elements in the periodic table. Hence, we speculate that the monocellular organisms might not be able to sufficiently differentiate between the almost chemically identical lanthanide elements.

Distribution and migration of nitrobenzene in water following a simulated spill.

Releases of nitrobenzene into the aquatic environment pose a threat to human health and aquatic resources, and have attracted much attention world-wide. In order to find out the distribution and migration patterns of pooled nitrobenzene underwater in different conditions, laboratory column experiments were designed to simulate stagnant water, flowing water and rainfall disturbance events. The results showed that in stagnant water there was a slow diffusion of the nitrobenzene from the pool leading to higher concentrations of the chemical deeper in the water column. In flowing water, the removal of the substance was rapid and water concentrations were much lower and more uniform throughout the column. The disturbance event brought a substantial quantity of nitrobenzene into the water column which then dissipated according to the flow regime. Analysis of the data showed that distribution pattern of nitrobenzene in the stagnant water column followed a logarithmic equation C(NB) = a ln(t) + b, and in disturbed flowing water, the distribution pattern of nitrobenzene followed a negative exponential regression equation C(NB) = Ne(-Mt). These conclusions have practical significance in developing remediation technologies for water polluted by nitrobenzene.

Effects of aging and freeze-thawing on extractability of pyrene in soil.

The effects of soil freezing and thawing on the extractability by dichloromethane of pyrene from two Chinese soils are investigated. The soils were collected from the Northeast region of China where heavy pollution of soils by Polycyclic Aromatic Hydrocarbons (PAH) is common. Two soils were considered: a burozem obtained from the Shenfu irrigated region in Liaoning province and a phaeozem collected from the Hailun area in Haerbin province. The soils were collected from areas free from PAH pollution. Pyrene was aged in sterilized soil, and autoclaved deionized water was then added to adjust the soil to different moisture levels. The combined dichloromethane extractions of pyrene in soils at various periods showed that the quantity of pyrene extracted with dichloromethane could be divided into two stages: the initially rapid period and a longer, slower period. The frequency of freeze-thawing cycles had different and contradictory effects on pyrene extractability between the two soil types. Soil moisture also was found to have different and opposite effects on pyrene extractability. Freeze-thawing cycles had great influence on pyrene extractability both in aged and unaged soils. The changes in unaged soil were more significant than those in 1-year aged soil and attributed to changes in the soil organic matter. Our research shows that the effect of freezing and thawing on pyrene extraction is complicated due to the differences in physical and chemical properties of soils as well as the aging process.

Optimization of laccase production from Trametes versicolor by solid fermentation.

The regulation of culture conditions, especially the optimization of substrate constituents, is crucial for laccase production by solid fermentation. To develop an inexpensive optimized substrate formulation to produce high-activity laccase, a uniform design formulation experiment was devised. The solid fermentation of Trametes versicolor was performed with natural aeration, natural substrate pH (about 6.5), environmental humidity of 60% and two different temperature stages (at 37 degrees C for 3 days, and then at 30 degrees C for the next 17 days). From the experiment, a regression equation for laccase activity, in the form of a second-degree polynomial model, was constructed using multivariate regression analysis and solved with unconstrained optimization programming. The optimized substrate formulation for laccase production was then calculated. Tween 80 was found to have a negative effect on laccase production in solid fermentation; the optimized solid substrate formulation was 10.8% glucose, 27.7% wheat bran, 9.0% (NH4)2SO4, and 52.5% water. In a scaled-up verification of solid fermentation at a 10 kg scale, laccase activity from T. versicolor in the optimized substrate formulation reached 110.9 IU/g of dry mass.

Trace metal concentrations in edible tissue of snapper, flathead, lobster, and abalone from coastal waters of Victoria, Australia.

The concentrations of heavy metals in the edible tissue of commonly fished species of the Victorian coast of Australia are reported. The metals studied were As, Cd, Cu, Hg, Pb, Se, and Zn and the fish species examined were snapper (Pagruss auratus), flathead (Platycephalus bassenssis and Neoplatycephalus richardsoni), lobster (Jasus edwardsii), and abalone (Haliotis rubra). None of the fish species studied had average concentrations exceeding the maximum levels specified for As, Cd, Hg, and Pb by the Food Standards Australia and New Zealand Food Standards code. Additionally, the concentrations of Cu, Se, and Zn were close to or below the median values generally expected in these species. Essential trace elements Se and Zn were found to be well regulated by all fish species. Although also essential, Cu was not so well regulated, especially in abalone. Nonessential metals As, Cd, and Hg are not regulated in the studied fish and their concentrations in the fish tissue are dependent on size and fishing zone. Metal concentrations were not largely affected by sex. Surprisingly, the concentrations of metals in fish in Port Phillip Bay, a zone, which includes the major cities of Melbourne and Geelong and is known to have high concentrations of metals in the water and sediment, were not consistently higher than those in other less-populated fishing zones.

Pectinase production by solid fermentation from Aspergillus niger by a new prescription experiment.

The Ordos Plateau in China is covered with up to 300,000 ha of peashrub (Caragana) which is the dominant natural vegetation and ideal for fodder production. To exploit peashrub fodder, it is crucially important to optimize the culture conditions, especially culture substrate to produce pectinase complex. In this study, a new prescription process was developed. The process, based on a uniform experimental design, first optimizes the solid substrate and second, after incubation, applies two different temperature treatments (30 degrees C for the first 30 h and 23 degrees C for the second 42 h) in the fermentation process. A multivariate regression analysis is applied to a number of independent variables (water, wheat bran, rice dextrose, ammonium sulfate, and Tween 80) to develop a predictive model of pectinase activity. A second-degree polynomial model is developed which accounts for an excellent proportion of the explained variation (R(2)=97.7%). Using unconstrained mathematical programming, an optimized substrate prescription for pectinase production is subsequently developed. The mathematical analysis revealed that the optimal formula for pectinase production from Aspergillus niger by solid fermentation under the conditions of natural aeration, natural substrate pH (about 6.5), and environmental humidity of 60% is rice dextrose 8%, wheat bran 24%, ammonium sulfate ((NH(4))(2)SO(4)) 6%, and water 61%. Tween 80 was found to have a negative effect on the production of pectinase in solid substrate. With this substrate prescription, pectinase produced by solid fermentation of A. niger reached 36.3 IU/(gDM). Goats fed on the pectinase complex obtain an incremental increase of 0.47 kg day(-1) during the initial 25 days of feeding, which is a very promising new feeding prospect for the local peashrub. It is concluded that the new formula may be very useful for the sustainable development of arid and semiarid pastures such as those of the Ordos Plateau.

Quantitative microbial risk assessment models for consumption of raw vegetables irrigated with reclaimed water.

Quantitative microbial risk assessment models for estimating the annual risk of enteric virus infection associated with consuming raw vegetables that have been overhead irrigated with nondisinfected secondary treated reclaimed water were constructed. We ran models for several different scenarios of crop type, viral concentration in effluent, and time since last irrigation event. The mean annual risk of infection was always less for cucumber than for broccoli, cabbage, or lettuce. Across the various crops, effluent qualities, and viral decay rates considered, the annual risk of infection ranged from 10(-3) to 10(-1) when reclaimed-water irrigation ceased 1 day before harvest and from 10(-9) to 10(-3) when it ceased 2 weeks before harvest. Two previously published decay coefficients were used to describe the die-off of viruses in the environment. For all combinations of crop type and effluent quality, application of the more aggressive decay coefficient led to annual risks of infection that satisfied the commonly propounded benchmark of < or =10(-4), i.e., one infection or less per 10,000 people per year, providing that 14 days had elapsed since irrigation with reclaimed water. Conversely, this benchmark was not attained for any combination of crop and water quality when this withholding period was 1 day. The lower decay rate conferred markedly less protection, with broccoli and cucumber being the only crops satisfying the 10(-4) standard for all water qualities after a 14-day withholding period. Sensitivity analyses on the models revealed that in nearly all cases, variation in the amount of produce consumed had the most significant effect on the total uncertainty surrounding the estimate of annual infection risk. The models presented cover what would generally be considered to be worst-case scenarios: overhead irrigation and consumption of vegetables raw. Practices such as subsurface, furrow, or drip irrigation and postharvest washing/disinfection and food preparation could substantially lower risks and need to be considered in future models, particularly for developed nations where these extra risk reduction measures are more common.

The consequences of land use change on nutrient exports: a regional scale assessment in south-west Victoria, Australia.

Estimation of nutrient load production based on multi-temporal remotely sensed land use data for the Glenelg-Hopkins region in south-west Victoria, Australia, is discussed. Changes in land use were mapped using archived Landsat data and computerised classification techniques. Land use change has been rapid in recent history with 16% of the region transformed in the last 22 years. Total nitrogen and phosphorus loads were estimated using an export coefficient model. The analysis demonstrates an increase in modelled nitrogen and phosphorus loadings from 1980 to 2002. Whilst such increases were suspected from past anecdotal and ad-hoc evidence, our modelling estimated the magnitude of such increases and thus demonstrated the enormous potential of using remote sensing and GIS for monitoring regional scale environmental processes.

Chemical and physical speciation of arsenic in a small pond receiving gold mine waste effluent.

The chemical and physical speciation of arsenic in a small pond that receives wastewater from a gold mine operation in western Victoria, Australia was studied using differential pulse polarography. By using different sample pretreatments, distinction between the physical states (dissolved or particulate As), between the oxidation states (As(III) or As(V)), and between the degrees of lability (labile or strongly bound) was achieved. The results are interpreted in terms of the physicochemical properties with reference to the use of the pond as a settlement dam for gold mining effluent. The speciation of arsenic was found to vary markedly with the physicochemical properties of the water. A model for the behavior of arsenic in the pond is proposed.