An assessment of land-based climate and carbon reversibility in the Australian Community Climate and Earth System Simulator

Future levels of climate change depend not only on carbon emissions but also on carbon uptake by the land and the ocean. Here we are using the Earth system model (ESM1) version of the Australian Community Climate and Earth System Simulator (ACCESS) to explore the potential and impact of removing carbon dioxide (CO₂) from the atmosphere through the climate and carbon cycle reversibility experiment. This experiment builds on the standard Coupled Model Intercomparison Project (CMIP) experiment, increasing CO₂ at 1% per year until 4xCO₂ is reached. The atmospheric CO₂ levels are then decreased at the same rate which brings the CO₂ back to pre-industrial levels. We then continue to run the model with constant CO₂ for another 350 years. Our analysis focuses on the response of the land carbon cycle. We find that carbon stores are largely reversible at the global scale over the timescale of changing CO₂. However, carbon stores continue to decrease after CO₂ returns to its initial value, and the land loses another 40 Pg of carbon (PgC) with the largest change in the tropics. It takes about 300 years beyond the period of changing CO₂ for the carbon stores to recover. Interestingly, we saw strong regional variations in the strength of the land response to changing CO₂. Australia showed the largest increase/decrease in biomass carbon (about 40%) and the largest variability in productivity, which was strongly correlated with rainfall. This highlights the importance of assessing the regional response to understanding the processes underlying the response and the sensitivity of these processes within each model. This understanding will benefit future multi-model analyses of this reversibility experiment. It also illustrates more generally the potential to use Earth system model experiments as part of the evaluation of proposed applications of carbon dioxide removal (CDR) technologies. As such, we recommend that these types of modelling experiments be included when mitigation policies are developed.

     

Predatory spider mimics acquire colony-specific cuticular hydrocarbons from their ant model prey

The integrity of social insect colonies is maintained by members recognising and responding to the chemical cues present on the cuticle of any intruder. Nevertheless, myrmecophiles use chemical mimicry to gain access to these nests, and their mimetic signals may be acquired through biosynthesis or through contact with the hosts or their nest material. The cuticular hydrocarbon profile of the myrmecophilous salticid spider Cosmophasis bitaeniata closely resembles that of its host ant Oecophylla smaragdina. Here, we show that the chemical resemblance of the spider does not arise through physical contact with the adult ants, but instead the spider acquires the cuticular hydrocarbons by eating the ant larvae. More significantly, we show that the variation in the cuticular hydrocarbon profiles of the spider depends upon the colony of origin of the ant larvae prey, rather than the parentage of the spider.     

Estimating the Recreational-Use Value for Hiking in Bellenden Ker National Park, Australia

The recreational-use value of hiking in the Bellenden Ker National Park, Australia has been estimated using a zonal travel cost model. Multiple destination visitors have been accounted for by converting visitors’ own ordinal ranking of the various sites visited to numerical weights, using an expected-value approach. The value of hiking and camping in this national park was found to be $AUS 250,825 per year, or $AUS 144,45 per visitor per year, which is similar to findings from other studies valuing recreational benefits. The management of the park can use these estimates when considering the introduction of a system of user pays fees. In addition, they might be important when decisions need to be made about the allocation of resources for maintenance or upgrade of tracks and facilities.     

Effect of chelating agents and solubility of cadmium complexes on uptake from soil by Brassica juncea

Brassica juncea, or Indian mustard, was grown in soil artificially contaminated with either a soluble salt, CdCl(2), at 186mg Cdkg(-1), or alternately an insoluble, basic salt, CdCO(3), at 90mg Cdkg(-1). These experiments study the range of Cd uptake by Indian mustard from conditions of very high Cd concentration in a soluble form to the other extreme with an insoluble Cd salt. After plants were established, four different chelating agents were applied. Chelating agents increased plant uptake of Cd from the CdCl(2) soil but did not significantly increase plant uptake of Cd from the CdCO(3) contaminated soil. Addition of ethylenediaminetetraacetic acid (EDTA) increased the plant concentration of Cd by almost 10-fold in soils contaminated with CdCl(2), with a concentration of 1283mg Cdkg(-1) in the dried EDTA-treated plants over a concentration of 131mg Cdkg(-1) in plants without added chelate. However, EDTA increased the aqueous solubility of Cd by 36 times over the soil matrix without added chelator, and thereby, increased the possibility of leaching. Other chelators used in both experiments were ethylenebis(oxyethylenenitrilo)tetraacetic acid, trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid, and diethylenetriaminepentaacetic acid (DTPA) increasing Cd in plants to 1240, 962, and 437mg Cdkg(-1), respectively. The other chelating agents increased the solubility of Cd in the leachate but not to the extent of EDTA. Comparing all chelating agents studied, DTPA increased plant uptake in terms of Cd in dried plant concentration most relative to the solubility of complexed Cd in runoff water.     

Sorption of organic contaminants by biopolymers: role of polarity, structure and domain spatial arrangement

Sorption behavior of hydrophobic organic contaminants (HOCs) (i.e., pyrene, phenanthrene and naphthalene) by native and chemically modified biopolymers (lignin, chitin and cellulose) was examined. Lignins (native and treated) showed nonlinear sorption for all compounds studied, emphasizing their glassy character. Chitins and celluloses had linear isotherms for phenanthrene and naphthalene, illustrating the dominance of partitioning, while pyrene yielded nonlinear isotherms. Sorption capacity (K(oc)) of HOCs was negatively correlated with the polarity [(O+N)/C] of the biopolymers. Aromatic and alkyl+aromatic C percentages, rather than alkyl C content, demonstrated a better correlation with K(oc) values, indicating the importance of aromatic structures for HOC affinity. Hydrophobicity (K(ow))-normalized K(oc) values decreased sharply with increasing percentage of O-alkyl C versus total aliphatic C (O-alkyl C/total aliphatic C) or with polar C/(alkyl+aromatic C) ratio of the biopolymers until their values reached 80% and 4, respectively, illustrating the effect of surrounding polar groups on reducing affinity for HOCs. Overall, the results of this study highlight the role of spatial arrangement of domains within biopolymers in sorption of HOCs, and point to sorbent properties, such as functionality, polarity and structure, jointly regulating the sorption of HOCs in biopolymers.     

Desorption of arsenic from drinking water distribution system solids

Previous work has shown that arsenic can accumulate in drinking water distribution system (DWDS) solids (Lytle et~al., 2004) when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary objective of this work was to examine the impact of pH and orthophosphate on the chemical release (i.e. desorption) of arsenic from nine DWDS solids collected from utilities located in the Midwest. Arsenic release comparisons were based on the examination of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168~hours. Results showed that arsenic was released from solids and suggested that arsenic release was a result of desorption rather than dissolution. Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in the test range of 7 to 9). Finally, orthophosphate (3 and 5 mg PO₄/L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting in elevated levels at the consumer's tap.     

Airborne molds and mycotoxins associated with handling of corn silage and oilseed cakes in agricultural environment

In agricultural areas, the contamination of feedstuffs with molds and mycotoxins presents major environmental and health concerns. During cattle feeding, fungi and mycotoxins were monitored in corn silage, oilseed cakes and bioaerosols collected in Normandy. Most of the corn silages were found to be contaminated by deoxynivalenol (mean concentration: 1883 μg kg^?1) while a few of oilseed cakes were contaminated by alternariol, fumonisin B₁ or gliotoxin. In ambient bioaerosols, the values for fungi per cubic meter of air varied from 4.3 × 10² to 6.2 × 10⁵ cfu m^?3. Seasonal variations were observed with some species like Aspergillus fumigatus which significantly decreased between the 2 seasons (P = 0.0186) while the Penicillium roqueforti group significantly increased during the second season (P = 0.0156). In the personal bioaerosols, the values for fungi per cubic meter of air varied from 3.3 10³ to 1.7 10⁶ cfu m^?3 and the number of A. fumigatus spores significantly decreased between the 2 seasons (P = 0.0488). Gliotoxin, an immunosuppressive mycotoxin, was quantified in 3 personal filters at 3.73 μg m^?3, 1.09 μg m^?3 and 2.97 μg m^?3.     

Social learning in a policy-mandated collaboration: community wildfire protection planning in the eastern United States

Policies such as the US Healthy Forests Restoration Act (HFRA) mandate collaboration in planning to create benefits such as social learning and shared understanding among partners. However, some question the ability of top-down policy to foster successful local collaboration. Through in-depth interviews and document analysis, this paper investigates social learning and transformative learning in three case studies of Community Wildfire Protection Planning (CWPP), a policy-mandated collaboration under HFRA. Not all CWPP groups engaged in social learning. Those that did learned most about organisational priorities and values through communicative learning. Few participants gained new skills or knowledge through instrumental learning. CWPP groups had to commit to learning, but the design of the collaborative-mandate influenced the type of learning that was most likely to occur. This research suggests a potential role for top-down policy in setting the structural context for learning at the local level, but also confirms the importance of collaborative context and process in fostering social learning.