Characterization studies of a semi‐automated separation method for analysis of non‐ortho substituted polychlorinated biphenyl (PCB) congeners in environmental samples

Non‐ortho substituted polychlorinated biphenyl (PCB) congeners can account for the majority of the dioxin‐like toxicity in environmental samples, yet analysis for these congeners is difficult because other PCB congeners co‐elute with them in most Chromatographic methods. An automated method was developed which incorporates a porous graphitic carbon (PGC) column which is commercially available. Non‐ortho substituted congeners were successfully separated from interfering PCB congeners. Recoveries of non‐ortho substituted congeners were consistently reproducible (CV < 9%) when chicken eggs were fortified with individual congeners.     

Environmental fate of pesticides used in Australian viticulture IV. Aqueous stability of dithianon

Dithianon formulations are unstable in slightly basic aqueous solutions (pH 9, 20°C, t _½ = 5.6 h) but relatively stable in neutral or acidic solution (pH 4,20°C, t _½ = 6443 h). To ensure the efficacy of this fungicide it is important to prepare the spray mix fresh with neutral or slightly acidic water. Dithianon is unstable towards natural sunlight in the solid and aqueous phase, with half‐lives of approximately 68 and 42 days, respectively. Thermal hydrolysis does not seem to be the preferred degradation pathway when aqueous solutions are heated by the South Australian summer sun. The major aqueous phase photodegradation product has been identified as 2,3‐dihydro‐1,4‐dithiaanthraquinone. These results strongly suggest that should dithianon be accidentally released into basic Australian waters then it is likely to be rapidly chemically hydrolysed and pose little long term environmental threat. However, dithianon is only slowly chemically and photo‐lytically hydrolysed in neutral and acidic waters, and in this case accidentally release may pose a significant short term environmental threat.     

An arsenic-contaminated field trial to assess the uptake and translocation of arsenic by genotypes of rice

Compared to other cereals, rice has particular strong As accumulation. Therefore, it is very important to understand As uptake and translocation among different genotypes. A field study in Chenzhou city, Hunan province of China, was employed to evaluate the effect of arsenic-contaminated soil on uptake and distribution in 34 genotypes of rice (including unpolished rice, husk, shoot, and root). The soil As concentrations ranged from 52.49 to 83.86 mg kg^?1, with mean As concentration 64.44 mg kg^?1. The mean As concentrations in rice plant tissues were different among the 34 rice genotypes. The highest As concentrations were accumulated in rice root (196.27–385.98 mg kg^?1 dry weight), while the lowest was in unpolished rice (0.31–0.52 mg kg^?1 dry weight). The distribution of As in rice tissue and paddy soil are as follows root ? soil > shoot > husk > unpolished rice. The ranges of concentrations of inorganic As in all of unpolished rice were from 0.26 to 0.52 mg kg^?1 dry weight. In particular, the percentage of inorganic As in the total As was more than 67 %, indicating that the inorganic As was the predominant species in unpolished rice. The daily dietary intakes of inorganic As in unpolished rice ranged from 0.10 to 0.21 mg for an adult, and from 0.075 to 0.15 mg for a child. Comparison with tolerable daily intakes established by FAO/WHO, inorganic As in most of unpolished rice samples exceeded the recommended intake values. The 34 genotypes of rice were classified into four clusters using a criteria value of rescaled distance between 5 and 10. Among the 34 genotypes, the genotypes II you 416 (II416) with the lowest enrichment of As and the lowest daily dietary intakes of inorganic As could be selected as the main cultivar in As-contaminated field.     

Leaching of metals in buried industrial sludge,spiked with cadmium,chromium and lead. Results of a trial

Sludge resulting from industrial waste water treatment at the industrial area of Patras, Greece, was spiked with cadmium, chromium and lead and entrenched in 4 experimental trenches. Soil from the unsaturated zone and sludge from the trenches were sampled at successive time points over a period of 14 months to monitor the movement of metals. Results showed that 94% of cadmium and 80% of lead but only 32% of chromium migrated from the sludge just 14 months after the entrenchment.

At the end of this time the buried sludge could be considered stabilised, as indicated by the total nitrogen content. Cd content in underlying soil layers at 3 m depth showed an increase in the first 7 months followed by a decrease, afterwards. Soil Pb concentration at 3 and 6 m depth was significantly high, in relation to it's initial concentration 14 months after the entrenchment. Pb and Cd in the soil samples were negatively correlated. It is suggested that lead displaces cadmium in the sediments.     

Multidimensional trade-offs in species responses to disturbance: implications for diversity in a subtropical forest

Species employ diverse strategies to cope with natural disturbance, but the importance of these strategies for maintaining tree species diversity in forests has been debated. Mechanisms that have the potential to promote tree species coexistence in the context of repeated disturbance include life history trade-offs in colonization and competitive ability or in species' ability to survive at low resource conditions and exploit the temporary resource-rich conditions often generated in the wake of disturbance (successional niche). Quantifying these trade-offs requires long-term forest monitoring and modeling. We developed a hierarchical Bayes model to investigate the strategies tree species employ to withstand and recover from hurricane disturbance and the life history trade-offs that may facilitate species coexistence in forests subject to repeated hurricane disturbance. Unlike previous approaches, our model accommodates temporal variation in process error and observations from multiple sources. We parameterized the model using growth and mortality data from four censuses of a 16-ha plot taken every five years (1990-2005), together with damage data collected after two hurricanes and annual seed production data (1992-2005). Species' susceptibilities to hurricane damage as reflected by changes in diameter growth and fecundity immediately following a storm were weak, highly variable, and unpredictable using traditional life history groupings. The lower crowding conditions (e.g., high light) generated in the wake of storms, however, led to greater gains in growth and fecundity for pioneer and secondary-forest species than for shade-tolerant species, in accordance with expectation of life history. We found moderate trade-offs between survival in high crowding conditions, a metric of competitive ability, and long-distance colonization. We also uncovered a strong trade-off between mean species fecundity in low crowding conditions, a metric of recovery potential, and competitive ability. Trade-offs in competitive and colonization ability, in addition to successional niche processes, are likely to contribute to species persistence in these hurricane-impacted forests. The strategies species employ to cope with hurricane damage depend on the degree to which species rely on sprouting, repair of adult damage, changes in demographic rates in response to enhanced resource availability after storms, or long-distance dispersal as recovery mechanisms.     

Projected vegetation changes for the American Southwest: combined dynamic modeling and bioclimatic-envelope approach

This study focuses on potential impacts of 21st century climate change on vegetation in the Southwest United States, based on debiased and interpolated climate projections from 17 global climate models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Among these models a warming trend is universal, but projected changes in precipitation vary in sign and magnitude. Two independent methods are applied: a dynamic global vegetation model to assess changes in plant functional types and bioclimatic envelope modeling to assess changes in individual tree and shrub species and biodiversity. The former approach investigates broad responses of plant functional types to climate change, while considering competition, disturbances, and carbon fertilization, while the latter approach focuses on the response of individual plant species, and net biodiversity, to climate change. The dynamic model simulates a region-wide reduction in vegetation cover during the 21st century, with a partial replacement of evergreen trees with grasses in the mountains of Colorado and Utah, except at the highest elevations, where tree cover increases. Across southern Arizona, central New Mexico, and eastern Colorado, grass cover declines, in some cases abruptly. Due to the prevalent warming trend among all 17 climate models, vegetation cover declines in the 21st century, with the greatest vegetation losses associated with models that project a drying trend. The inclusion of the carbon fertilization effect largely ameliorates the projected vegetation loss. Based on bioclimatic envelope modeling for the 21st century, the number of tree and shrub species that are expected to experience robust declines in range likely outweighs the number of species that are expected to expand in range. Dramatic shifts in plant species richness are projected, with declines in the high-elevation evergreen forests, increases in the eastern New Mexico prairies, and a northward shift of the Sonoran Desert biodiversity maximum.     

Drastic decline of an extensive eelgrass bed in Nova Scotia due to the activity of the invasive green crab (Carcinus maenas)

In 2001–2002, there were severe declines of eelgrass (Zostera marina) in estuaries along the Nova Scotia coast of the southern Gulf of St. Lawrence. We examined the relationship between the recent invasion of European green crabs (Carcinus maenas) and the eelgrass decline in Benoit Cove in Tracadie Harbour. The abnormally abundant eelgrass wrack consisted mainly of entire shoots, not the usual blades. Three separate methods yielded similar estimates of the rate of shoot removal from the eelgrass beds (direct quadrat counts, “mark–recapture” of tagged shoots in the eelgrass bed, and rate of shoot appearance in the shore wrack). From 14 July to 8 September 2002, the shoot density in the bed fell by about 75 %. Similar rates of decline occurred in crab enclosures (4.4 crabs m^?2) placed in the eelgrass bed. Green crab foraging, involving the tearing of shoots and the digging of large pits, was the reason for the drastic decline of the eelgrass bed in Benoit Cove. It is clear that an invasion of green crabs to a region where they had not previously existed can both destroy eelgrass beds and restrict their recovery.     

Coastal scenic assessment: unlocking the potential for coastal tourism in rural Pakistan via Mediterranean developed techniques

Originally developed within the Mediterranean, a tested coastal management and planning tool was applied outside the region to evaluate its international scope, with particular reference to a less developed country. Seven coastal sites in Pakistan were investigated for their scenic values through a 26 item checklist grouped as physical and human parameters analysed though weighted parameters and fuzzy logic matrices. With respect to a five-class evaluation system, results indicated: Jiwani, Miani Hor and Pasni-Astola Island as extremely attractive natural sites with very high landscape value (classified as Class 1 sites); Mubarak village as an attractive natural site with high landscape value (classified as a Class 2 site); Kaka pir village, Harjana village and Keti Bandar as having little outstanding landscape features or with urban environment and classified as Class 3 sites. Rural and/or urban environmental influences were observed to be critical factors which influenced major human parameters that ultimately affect sites’ scenic classification. However, notwithstanding natural attraction, unless political and social development barriers are tackled in conjunction with recognising areas that possess inherent tourism potential, economic potential is unlikely to be realised.     

POTENTIAL CLIMATE CHANGE IMPACTS ON WATER RESOURCES IN THE GREAT PLAINS1

ABSTRACT: This paper reports on the current assessment of climate impacts on water resources, including aquatic ecosystems, agricultural demands, and water management, in the U.S. Great Plains. Climate change in the region may have profound effects on agricultural users, aquatic ecosystems, and urban and industrial users alike. In the central Great Plains Region, the potential impacts of climate changes include changes in winter snowfall and snow-melt, growing season rainfall amounts and intensities, minimum winter temperature, and summer time average temperature. Specifically, results from general circulation models indicate that both annual average temperatures and total annual precipitation will increase over the region. However, the seasonal patterns are not uniform. The combined effect of these changes in weather patterns and average seasonal climate will affect numerous sectors critical to the economic, social and ecological welfare of this region. Research is needed to better address the current competition among the water needs of agriculture, urban and industrial uses, and natural ecosystems, and then to look at potential changes. These diverse demands on water needs in this region compound the difficulty in managing water use and projecting the impact of climate changes among the various critical sectors in this region.     

Autotrophic and bacterial production: Fractionation of plankton populations by differential filtration of samples from the English channel

The relationship between release of organic substances by phytoplankton and their utilization by heterotrophic bacteria has been measured by means of differential filtration in parallel Steemann Nielsen and Parsons and Strickland incubations. In Southampton Waters (UK), between March and September, the values for bacterial production measured in the above manner varied between 1 and 30%, the total primary production being taken as 100%. Even when low bacterial production occurs during the light period of incubation, a significant increase takes place during the following dark period. Thus, a close correlation between primary algal and the resultant bacterial production can be demonstrated. Quantitative data on bacterial production may be obtained from the conventional productivity experiments by simple double filtration.