Extracellular polymeric substances (EPS) from cyanobacterial mats: characterisation and isolation method optimisation

Extracellular polymeric substances (EPS) play an important role in bacterial mat formation and sediment stabilisation of coastal zones. The analysis of these secretion products on a molecular level is a prerequisite to understand their formation mechanisms and ecological function in microbial consortia. The present study focuses on the optimisation of EPS isolation and characterisation from cohesive cyanobacterial mats. Extracted EPS were analysed for quantity, content of total organic carbon and nitrogen, and bulk contents of neutral sugars, uronic acids, and proteins. These criteria are strongly influenced by the extraction conditions applied and therefore, the effects of different extraction media (NaCl or artificial seawater), addition of EDTA, centrifugal force, and purification via repeated ethanol precipitation on extraction success were determined. From this an optimised extraction procedure for EPS resulted. When using fresh mat samples, the yield of EPS amounted to 3.3 ± 0.8 mg g⁻¹ mat (dw). The isolated EPS were composed of nearly equal amounts of proteins and uronic acids (12.7 ± 1.5 and 11.8 ± 1.1%, respectively) and the bulk content of neutral sugars was 30.5 ± 2.6%. High contents of TOC and TN indicated relatively pure EPS and only a low contribution of inorganic compounds. Furthermore, low contents of 2-keto-3-deoxyoctonate and the small protein/polysaccharide-ratio in the EPS extracted by our method, signified low contaminations by intracellular polymers and hence a low rupture of cells. Our method provides an useful tool to evaluate further investigations of the composition, characteristics and properties of EPS on a sound basis.     

Urban Air Quality Assessment Model: UAQAM

The Urban Air Quality Assessment Model (UAQAM) calculates urban concentrations caused by city emissions themselves, the so-called city background concentration. Three versions of the model for describing the dispersion were studied: Box, Gifford Hanna (GH) and a combined form of these two (Box–GH model). Regional background emissions contributing to the urban background concentration were accounted for by using measurements and calculations from a dispersion model on the continental scale. The results of the three UAQAM versions for a number of European cities were compared to measurements of SO₂ and NO _X . The Box–GH model shows better results when compared to the Box model and slightly better results in comparison to the GH model. The Box–GH model has been taken as a starting point for the assessment of urban air quality with UAQAM.     

The production of uneven access to land and water in peri-urban spaces: de facto privatisation in greater Accra

ABSTRACT

Peri-urban spaces are frontiers of privatisation where inequalities in access to land and water evolve. In this article, we analyse a particular mode of land and water privatisation in peri-urban spaces of the Greater Accra Metropolitan Area (GAMA), Ghana. We illustrate that in the domain of land, traditional authorities tend to act as private owners rather than custodians of customary land, while in the domain of water, multiple private water providers have emerged next to the official water utility. A combined reading and analysis of these processes as forms of de facto privatisation contributes to understanding the similarities in the control over and access to land and water in peri-urban spaces. We show that in the de facto privatised control context of the peri-urban GAMA, access gained to land and water has to be actively maintained. Both gaining and maintaining access exhibit socio-economic inequalities and this is particularly so in the case of maintaining access. The article is a call for a better connection between land and water studies in order to deepen understanding of the processes at play in peri-urban spaces.     

Place attachment and place identity in natives and non-natives

Place attachment is an affective bond that people establish with specific areas where they prefer to remain and where they feel comfortable and safe. Place identity, however, has been defined as a component of personal identity, a process by which, through interaction with places, people describe themselves in terms of belonging to a specific place. Most research has observed positive correlations between these variables in populations that have maintained ongoing interactions over long periods of time. This work presents two studies in which we compare place attachment to place identity in samples differentiated according to birthplace and length of residence, and the magnitude of these bonds to different places. The results of the first study revealed differences between intensity of attachment and identity depending on place of origin and place assessed. The second study found that identity and attachment tend to coincide in natives, while individuals from other places give higher scores for attachment than for identity. Results from the two studies have enabled us to consider that place attachment develops before place identity, at least in the case of the non-natives. Both studies reveal that bonds are stronger with the city than with the neighbourhood, but that attachment and identity with the island are stronger than either of them.