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 SO₂ pollution and heavy metal contamination in soils on the metal contents and productivity of soybean plant.     

Growth and elemental accumulation by canola on soil amended with coal fly ash

To explore the agronomic potential of an Australian coal fly ash, we conducted two glasshouse experiments in which we measured chlorophyll fluorescence, CO2 assimilation (A), transpiration, stomatal conductance, biomass accumulation, seed yield, and elemental uptake for canola (Brassica napus) grown on soil amended with an alkaline fly ash. In Experiment 1, application of up to 25 Mg/ha of fly ash increased A and plant weight early in the season before flowering and seed yield by up to 21%. However, at larger rates of ash application A, plant growth, chlorophyll concentration, and yield were all reduced. Increases in early vigor and seed yield were associated with enhanced uptake of phosphorus (P) by the plants treated with fly ash. Fly ash application did not influence accumulation of B, Cu, Mo, or Zn in the stems at any stage of plant growth or in the seed at harvest, except Mo concentration, which was elevated in the seed. Accumulation of these elements was mostly in the leaves, where concentrations of Cu and Mo increased with any amount of ash applied while that of B occurred only with ash applied at 625 Mg/ha. In Experiment 2, fly ash applied at 500 Mg/ha and mixed into the whole 30 cm soil core was detrimental to growth and yield of canola, compared with restricting mixing to 5 or 15 cm depth. In contrast, application of ash at 250 Mg/ha with increasing depth of mixing increased A and seed yield. We concluded that fly ash applied at not more than 25 Mg/ha and mixed into the top 10 to 15 cm of soil is sufficient to obtain yield benefits.     

Effects of Water Withdrawal From Ice‐Covered Lakes on Oxygen,Temperature, and Fish1

Abstract: In northern regions, large volumes of water are needed for activities such as winter road construction. Such withdrawals, particularly from small lakes, can reduce oxygen concentrations and water levels, potentially affecting aquatic organisms. Withdrawal limits have been developed by regulatory agencies, but are largely theoretical. Water withdrawal thresholds were tested in two small lakes by removing 10% and 20% of their respective under‐ice volumes and comparing oxygen parameters, temperature, over‐wintering habitat, and northern pike (Esox lucius) abundance to reference conditions. Because of a milder winter, oxygen parameters were elevated in reference lakes in the period following withdrawal compared to the prewithdrawal period. The 10% withdrawal resulted in a ?0.2 m shift in the oxygen concentration profile at 4 mg/l in that lake, but had no effect on total volume‐weighted oxygen, or volume of over‐wintering habitat. In contrast, the 20% withdrawal caused 0.7 m reduction in the oxygen concentration profile at 4 mg/l compared to the previous year, a 26% decline in the volume‐weighted oxygen concentration, and a 23% reduction in the volume of over‐wintering habitat compared to prewithdrawal conditions. Water temperatures were slightly (≤ 10%) colder in the upper strata in the year following the withdrawal in both withdrawal and reference lakes. Northern pike abundance was not impacted by water withdrawals in either of the lakes. The results of this study show that the effects of water withdrawal on the parameters investigated reflected the characteristics of the lakes, and would therefore be expected to vary from lake to lake. Policy development to mitigate impacts must therefore reflect the site‐specific nature of water withdrawal.     

Transformations of nitrogen at the interface between the topsoil and an impervious clay subsoil

Much work has been done on gaseous emissions and leaching of nitrogenous compounds from whole soil profiles and also from soil surface measurements which are assumed to be mainly due to topsoil activity. In soils with an impervious clay subsoil, the boundary between the topsoil and subsoil may provide an interface for microbial activity, including N transformations. In this study, we investigated movement and transformations of two reactive N species (nitrate and urea) at the subsoil interface using a series of replicate, intact soil blocks, under two contrasting watering regimes. We measured fluxes in both liquid and gaseous phases and demonstrated that nitrate reaching the subsoil interface does not necessarily leach into water systems, but may denitrify immediately and could, therefore, add to atmospheric pollution through N₂O production. On the other hand, ammonium reaching the subsoil interface either directly, or after mineralization, appears to be more mobile than expected and has the potential to pollute watercourses.     

Phosphorus runoff from agricultural land and direct fertilizer effects: a review

Phosphorus (P) is one of the most important mineral nutrients in agricultural systems, and along with nitrogen (N), is generally the most limiting nutrient for plant production. Farming systems have intensified greatly over time, and in recent years it has become apparent that the concomitant increase in losses of N and P from agricultural land is having a serious detrimental effect on water quality and the environment. The last two decades have seen a marked increase in research into the issues surrounding diffuse losses of P to surface and ground water. This paper reviews this research, examining the issue of P forms in runoff, and highlighting the exceptions to some generally held assumptions about land use and P transport. In particular the review focuses on P losses associated with recent P fertilizer application, as opposed to organic manures, both on the amounts and the forms of P in runoff water. The effects of the physicochemical characteristics of different forms of P fertilizer are explored, particularly in relation to water solubility. Various means of mitigating the risk of loss of P are discussed. It is argued that the influence of recent fertilizer applications is an under-researched area, yet may offer the most readily applicable opportunity to mitigate P losses by land users. This review highlights and discusses some options that have recently become available that may make a significant contribution to the task of sustainable management of nutrient losses from agriculture.     

Estimation of septic tank setback distances based on transport of E. coli and F-RNA phages

Setback distances between septic tank systems and the shorelines of Lake Okareka, New Zealand were determined from model simulations for a worst-case scenario, using the highest hydraulic conductivity and gradient measured in the field, removal rates of the microbial indicators (Escherichia coli and F-RNA phages) determined from a column experiment, and maximum values of the design criteria for the disposal system, and assuming an absence of an unsaturated zone, a continuous discharge of the raw effluent from a failed or non-complying treatment system (both indicators at concentrations of 1x10(7) counts/100 ml) into the groundwater and no sorption of pathogens in the aquifer. Modelling results suggest that the minimal setback distances were 16 m to satisfy the New Zealand Recreational Water Quality Guidelines for E. coli <126 per 100 ml (Ministry for the Environment, 1999) and 48 m to meet the Drinking-Water Standards for New Zealand 2000 for enteric virus <1 per 100 l (Ministry of Health, 2000). These distances may be applicable for other lakeshores in pumice sand aquifers with groundwater velocities <7 m/day. Findings of laboratory column and batch experiments provided an insight into the microbial attenuation and transport processes in pumice sand aquifers. Bacterial removal was predominately through filtration (87-88%) and partially by die-off (12-13%), while viral removal was by both die-off (45%) and filtration (55%). In addition, microbial die-off in groundwater without aquifer material (i.e., free microbes) was much lower than die-off in groundwater with aquifer material (i.e., sorbed microbes) and contributed only 2-6% to the total removal. This implies that the setback distances estimated from die-off rates for the free microbes, determined in the laboratory without considering aquifer media and other removal processes, which are often reported in the literature, could be larger than necessary.     

Sourcing sediment using multiple tracers in the catchment of Lake Argyle,Northwestern Australia

Control of sedimentation in large reservoirs requires soil conservation at the catchment scale. In large, heterogeneous catchments, soil conservation planning needs to be based on sound information, and set within the framework of a sediment budget to ensure that all of the potentially significant sources and sinks are considered. The major sources of sediment reaching the reservoir, Lake Argyle, in tropical northwestern Australia, have been determined by combining measured sediment fluxes in rivers with spatial tracer-based estimates of proportional contributions from tributaries of the main stream entering the lake, the Ord River. The spatial tracers used are mineral particle magnetics, the strontium isotopic ratio, and the neodymium isotopic ratio. Fallout of ¹³⁷Cs has been used to estimate the proportion of the sediment in Lake Argyle eroded from surface soils by sheet and rill erosion, and, by difference, the proportion eroded from subsurface soils by gully and channel erosion. About 96% of the sediment in the reservoir has come from less than 10% of the catchment, in the area of highly erodible soils formed on Cambrian-age sedimentary rocks. About 80% of the sediment in the reservoir has come from gully and channel erosion. A major catchment revegetation program, designed to slow sedimentation in the reservoir, appears to have had little effect because it did not target gullies, the major source of sediment. Had knowledge of the sediment budget been available before the revegetation program was designed, an entirely different approach would have been taken.     

Characterization of total volatile organic compound emissions from paints

Recently, Homeswest in Western Australia and Murdoch University developed a project to construct low allergen houses (LAH) in a newly developed suburb. All potential volatile organic compound (VOC) emission materials used in LAH are required to be measured before the construction of LAH, to ensure they are low VOCs emission materials. To protect people sensitive to exposure to VOCs it is important to evaluate and select low VOCs emitting paints. In this paper, therefore, twelve different paints provided by local manufacturers were selected for analysis to characterize total volatile organic compounds (TVOC) emissions. Emissions of TVOCs from six organic solvent-soluble paints and six water-soluble paints were evaluated using a small test chamber under controlled temperature, relative humidity and air exchange rates. The major volatile organic compounds in these paints were also identified. The time dependence of TVOC emissions from paint products in the chamber was evaluated. TVOC emissions from organic solvent-soluble and water-soluble paints were compared. The influence of air exchange rate on the TVOC concentrations emitted from organic solvent-soluble and water-soluble paints was also investigated. A double-exponential equation was used to evaluate emission characteristics of TVOC from paint products. With this double-exponential model, the physical processes of TVOC emissions can be explained. A variety of emission parameters can be calculated and used to estimate real indoor TVOCs concentrations.     

A comparison of mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) for monitoring chlorinated trace organic contaminants in Hong Kong coastal waters

A comparison of mussels (Perna viridis) and semi-permeable membrane devices (SPMDs) was carried out at five sites, representing a gradient of contaminant concentrations, in Hong Kong coastal waters. Mussels, originally collected from a “clean” location, were deployed along with SPMDs at each site for 30 days. Analyses for chlorinated pesticides and polychlorinated biphenyls (PCBs) indicated that SPMDs have potential as monitoring tools, and to some extent can overcome the problems associated with mussels, such as natural variability, differing age, sex, and physical condition. However, in most cases, SPMDs failed to rank the sites in the same order as mussels in terms of contaminant concentrations. Nonetheless, in localities where mussels cannot survive – as shown at Kwun Tong in the present experiment – SPMDs may be valuable in providing an indication of potentially bio-available lipophilic pollutants.     

Mitochondrial cytochrome b variation in sleeper sharks (Squaliformes: Somniosidae)

Sleeper sharks are a poorly studied group of deep-sea sharks. The subgenus, Somniosus, contains three morphologically similar species: S. microcephalus found in the Arctic and North Atlantic; S. pacificus in the North Pacific; and S. antarcticus in the Southern Ocean. These sharks have been reported mainly in temperate to polar waters and occasionally in subtropical locations. They have not been recorded in tropical waters. This study investigates the relationships among the accepted species of Somniosus through analysis of mitochondrial cytochrome b sequence variation. Seventy-five samples were examined from four sampling locations in the North Pacific, Southern Ocean and North Atlantic. Twenty-one haplotypes were found. A minimum spanning parsimony network separated these haplotypes into two divergent clades, an S. microcephalus and an S. pacificus/antarcticus clade, strongly supporting the distinction of S. microcephalus as a separate species from the Pacific sleeper shark species. Analysis of genetic structure within the S. pacificus/antarcticus clade (analysis of molecular variance, allele frequency comparisons, and a nested clade analysis) showed limited or no differences amongst three populations. Further examination of genetic variation at more variable mtDNA and nuclear markers is needed to examine the species status of S. pacificus and S. antarcticus.