Identification of metal toxicity in sewage sludge leachate

Sewage sludge is a source of organic matter and nutrients with the potential for being used as a fertilizer. However, metals in sewage sludge might accumulate in soil after repeated sludge applications, and metal concentrations might reach concentrations that are toxic to microorganisms, soil organisms and/or plants. This toxicity might change with time due to kinetic factors or abiotic factors such as freezing, drying or rainfall. The objective of this study was to determine toxicity of sewage sludge leachate from a lysimeter with 50 cm of sludge applied. Attempts were also made to identify the cause of toxicity of the sludge leachate by toxicity identification and evaluation (TIE) techniques. Sludge leachate was collected monthly during 1 experimental year (August 2001 to August 2002). Metal concentrations were analysed, and the toxicity was determined with Daphnia magna (48-h immobility). The effect of EDTA or sodium thiosulphate addition, filtration through a CM-resin or a Millex-resin on toxicity was also tested. The results showed that toxicity of the sludge leachate apparently varied during the year, and that filtration through the CM-resin reduced most of the toxicity followed by the addition of EDTA. None of the other treatments reduced the toxicity of the sludge leachate. This indicated that one or more metals were responsible for the observed toxicity. Further calculations of toxic units (TU) suggested that Zn contributed most to the toxicity. Results also indicated that Ca concentrations in the sludge leachate reduced the toxicity of Zn.     

Evaluation of seasonal variation and the optimization of reducing sugar extraction from Ulva prolifera biomass using thermochemical method

Environmental Science and Pollution Research - Green macroalgae comprise significant amount of structural carbohydrates for their conversion to liquid biofuels. However, it generally relies on...     

Temporal and spatial infection dynamics indicate recognition events in the early hours of a dinoflagellate/coral symbiosis

The obligate symbiotic relationship between dinoflagellates, Symbiodinium spp. and reef building corals is re-established each host generation. The solitary coral Fungia scutaria Lamarck 1801 harbors a single algal strain, Symbiodinium ITS2 type C1f (homologous strain) during adulthood. Previous studies have shown that distinct algal ITS2 types in clade C correlate with F. scutaria—Symbiodinium specificity during the onset of symbiosis in the larval stage. The present study examined the early specificity events in the onset of symbiosis between F. scutaria larvae and Symbiodinium spp., by looking at the temporal and spatial infection dynamics of larvae challenged with different symbiont types. The results show that specificity at the onset of symbiosis was mediated by recognition events during the initial symbiont—host physical contact before phagocytosis, and by subsequent cellular events after the symbionts were incorporated into host cells. Moreover, homologous and heterologous Symbiodinium sp. strains did not exhibit the same pattern of localization within larvae. When larvae were infected with homologous symbionts (C1f), ~70% of the total acquired algae were found in the equatorial area of the larvae, between the oral and aboral ends, 21 h after inoculation. In contrast, no spatial difference in algal localization was observed in larvae infected with heterologous symbionts. This result provides evidence of functional differences among gastrodermal cells, during development of the larvae. The cells in the larval equator function as nutritive phagocytes, and also appear to function as a region of enhanced symbiont acquisition in F. scutaria.     

The influence of nectar secretion rates on the responses of bumblebees (Bombus spp.) to previously visited flowers

Bumblebees can avoid recently depleted flowers by responding to repellent scent-marks deposited on flower corollas by previous visitors. It has previously been suggested that avoidance of visited flowers for a fixed period would be a poor strategy, since different plant species vary greatly in the rate at which they replenish floral rewards. In this study, we examined the duration of flower repellency after an initial bumblebee visit, using wild bumblebees (Bombus lapidarius, B. pascuorum and B. terrestris) foraging on four different plant species (Lotus corniculatus, Melilotus officinalis, Phacelia tanacetifolia and Symphytum officinale). We constructed a model to predict flower visitation following an initial visit, based on the nectar secretion pattern of the different plant species, the insect visitation rate per flower, and the search and handling times of bumblebees foraging on the plant species in question. The model predicts an optimal duration of flower avoidance which maximises the rate of reward acquisition for all bees. However, this optimum may be open to cheating. For two plant species, the evolutionary stable strategy (ESS) is a shorter duration of flower avoidance than the optimum. We found the duration of flower avoidance was markedly different among flower species and was inversely related to nectar secretion rates. The predicted ESSs for each plant species were close to those observed, suggesting that the key parameters influencing bumblebee behaviour are those included in the model. We discuss how bees may alter the duration of their response to repellent scents, and other factors that affect flower re-visitation.     

A pilot study of mercury liberation and capture from coal-fired power plant fly ash

The coal-fired electric utility generation industry has been identified as the largest anthropogenic source of mercury (Hg) emissions in the United States. One of the promising techniques for Hg removal from flue gas is activated carbon injection (ACI). The aim of this project was to liberate Hg bound to fly ash and activated carbon after ACI and provide high-quality coal combustion products for use in construction materials. Both bench- and pilot-scale tests were conducted to liberate Hg using a thermal desorption process. The results indicated that up to 90% of the Hg could be liberated from the fly ash or fly-ash-and-activated-carbon mixture using a pilot-scale apparatus (air slide) at 538 degrees C with a very short retention time (less than 1 min). Scanning electron microscope (SEM) evaluation indicated no significant change in fly ash carbon particle morphology following the thermal treatment. Fly ash particles collected in the baghouse of the pilot-scale apparatus were smaller in size than those collected at the exit of the air slide. A similar trend was observed in carbon particles separated from the fly ash using froth flotation. The results of this study suggest a means for power plants to reduce the level of Hg in coal-combustion products and potentially recycle activated carbon while maintaining the resale value of fly ash. This technology is in the process of being patented.     

Effects of Pollinator Loss on Endemic New Zealand Mistletoes (Loranthaceae)

Abstract: The endemic mistletoes Peraxilla colensoi and P. tetrapetala (Loranthaceae) have declined considerably in New Zealand since 1840, reputedly because of introduced herbivores but coincident with a major decline in native bird densities. We show that at two South Island sites ( Craigieburn and Ohau) there are too few bird pollinators visiting the flowers to allow full fruit set. We studied pollination rates in P. colensoi at Wakefield and P. tetrapetala at Craigieburn over four flowering seasons and P. tetrapetala in one season at Ohau. Supplemental hand pollination increased fruit production 1.25–5.3 times at Craigieburn and Ohau but not at Wakefield. Excluding birds by covering mistletoes with mesh bags decreased fruit set significantly at Wakefield but had little effect at Craigieburn and Ohau. Bellbirds ( Anthornis melanura ) and Tuis (   Prosthemadera novaeseelandiae ) visited flowers significantly more often at Wakefield than at Craigieburn. A lack of pollen tubes in the style, not self-incompatibility or resource shortage, caused the low fruit production in unmanipulated flowers at Craigieburn. Thus, at the two P. tetrapetala sites (Craigieburn and Ohau) fruit set was chronically pollen limited, whereas P. colensoi at Wakefield was not pollen-limited. Data from other Peraxilla sites also suggest pollination failure. Our study suggests that the conservation of Peraxilla species will require maintenance of native bird populations. Tuis and Bellbirds are important pollinators and dispersers of many other New Zealand plants, and the breakdown of such mutualistic relationships may have widespread consequences.     

Worker drift and egg dumping by queens in wild Bombus terrestris colonies

Wild bumblebee colonies are hard to find and often inaccessible, so there have been few studies of the genetic structure of bumblebees within natural colonies, and hence, it is not clear how frequently events such as worker reproduction, worker drift and queen usurpation take place. This study aimed to quantify the occurrence of natal-worker reproduction, worker drift and drifter reproduction within 14 wild colonies of Bombus terrestris in Central Scotland. Four unlinked microsatellites were used to identify patterns of relatedness of the colonies’ adults and broods. In colonies with queens (queenright colonies), worker reproduction accounted for just 0.83 % of males, increasing to 12.11 % in queenless colonies. Four colonies contained a total of six workers which were not daughters of the queen, and were assumed to be drifters, and four male offspring of drifters. Drifting is clearly not common and results in few drifter offspring overall, although drifters produced approximately seven times more offspring per capita than workers that remained in their natal colony. Unexpectedly, two colonies contained clusters of sister workers and juvenile offspring that were not sisters to the rest of the adults or brood found in the colonies, demonstrating probable egg dumping by queens. A third colony contained a queen which was not a sister or daughter to the other bees in the colony. Although usurping of bumblebee colonies by queens in early season is well documented, this appears to be the first record of egg dumping, and it remains unclear whether it is being carried out by old queens or newly mated young queens.     

Towards a contraction and convergence target based on population life expectancies since 1960

This paper explores a finding that emerged in the early phases of a multidisciplinary project applying population health and psychology to issues of social progress and sustainability. Across 180 countries and half a century of data, the levels of carbon emissions per capita that maximise life expectancy fall within a tight band averaging only 6.6 tonnes—considerably less than wealthier countries emit per person. Various tests fail to break down the curves and, although the authors remain cautious, the stability since 1960 offers implications for the carbon budget leading up to 2050. This is the first time these curves have been contextualised against established climate science, with timely implications for international negotiations on sustainability and development.