title: Hypolimnetic phosphorus and nitrogen dynamics in a small, eutrophic lake with a seasonally anoxic hypolimnion

authors: Özkundakci, Deniz

subjects: eutrophication

abstract: In situ estimates of sediment nutrient flux are necessary to understand seasonal variations in internal loading in lakes. We investigated the sources and sinks of nutrients in the hypolimnion of a small (0.33 km²), relatively shallow (18 m max. depth), eutrophic lake (Lake Okaro, New Zealand) in order to determine changes in sediment nutrient fluxes resulting from a whole lake sediment capping trial using a modified zeolite phosphorus inactivation agent (Z2G1). Sediment nutrient fluxes in the hypolimnion were estimated as the residual term in a nutrient budget model that accounted for mineralisation of organic nutrients, nutrient uptake by phytoplankton and mixing, nitrification, adsorption/desorption and diffusion of dissolved nutrients at the thermocline. Of the total hypolimnetic phosphate and ammonium fluxes during one period of seasonal stratification (2007–08), up to 60 and 50%, respectively, were derived from the bottom sediments, 18 and 24% were due to mineralisation of organic species, 36 and 28% were due to phytoplankton uptake and 9 and 6% were from diffusion across the thermocline. Adsorption/desorption of phosphate to suspended solids and nitrification were of minor (<8%) importance to the total fluxes. Any reduction in sediment nutrient release by Z2G1 was small compared with both the total sediment nutrient flux and the sum of other hypolimnetic fluxes. Uneven sediment coverage of Z2G1 may have been responsible for the limited effect of the sediment capping layer formed by Z2G1.

text: Hypolimnetic phosphorus and nitrogen dynamics in a small, eutrophic lake with a seasonally anoxic hypolimnion In situ estimates of sediment nutrient flux are necessary to understand seasonal variations in internal loading in lakes. We investigated the sources and sinks of nutrients in the hypolimnion of a small (0.33 km²), relatively shallow (18 m max. depth), eutrophic lake (Lake Okaro, New Zealand) in order to determine changes in sediment nutrient fluxes resulting from a whole lake sediment capping trial using a modified zeolite phosphorus inactivation agent (Z2G1). Sediment nutrient fluxes in the hypolimnion were estimated as the residual term in a nutrient budget model that accounted for mineralisation of organic nutrients, nutrient uptake by phytoplankton and mixing, nitrification, adsorption/desorption and diffusion of dissolved nutrients at the thermocline. Of the total hypolimnetic phosphate and ammonium fluxes during one period of seasonal stratification (2007–08), up to 60 and 50%, respectively, were derived from the bottom sediments, 18 and 24% were due to mineralisation of organic species, 36 and 28% were due to phytoplankton uptake and 9 and 6% were from diffusion across the thermocline. Adsorption/desorption of phosphate to suspended solids and nitrification were of minor (<8%) importance to the total fluxes. Any reduction in sediment nutrient release by Z2G1 was small compared with both the total sediment nutrient flux and the sum of other hypolimnetic fluxes. Uneven sediment coverage of Z2G1 may have been responsible for the limited effect of the sediment capping layer formed by Z2G1.

year: 2011

title: An electron-deficient triosmium cluster containing the thianthrene ligand: Synthesis, structure and reactivity of [Os₃(CO)₉(μ3-η2-C₁₂H₇S₂)(μ-H)]

authors: Raha, Arun K.

subjects: triosmium cluster

abstract: Reaction of [Os₃(CO)₁₀(CH₃CN)₂] with thianthrene at 80 °C leads to the nonacarbonyl dihydride compound [Os₃(CO)₉(μ-3,4-η²-C₁₂H₆S₂)(μ-H)₂] (1) and the 46-electron monohydride compound [Os₃(CO)₉(μ₃-η²-C₁₂H₇S₂)(μ-H)] (2). Compound 2 reacts reversibly with CO to give the CO adduct [Os₃(CO)₁₀(μ-η²-C₁₂H₇S₂)(μ-H)] (3) whereas with PPh₃ it gives the addition product [Os₃(CO)₉)(PPh₃)(μ-η²-C₁₂H₇S₂)(μ-H)] (4) as well as the substitution product 1,2-[Os₃(CO)₁₀ ((PPh₃)₂] (5) Compound 2 represents a unique example of an electron-deficient triosmium cluster in which the thianthrene ring is bound to cluster by coordination of the sulfur lone pair and a three-center-two-electron bond with the C(2) carbon which bridges the same edge of the triangle as the hydride. Electrochemical and DFT studies which elucidate the electronic properties of 2 are reported.

text: An electron-deficient triosmium cluster containing the thianthrene ligand: Synthesis, structure and reactivity of [Os₃(CO)₉(μ3-η2-C₁₂H₇S₂)(μ-H)] Reaction of [Os₃(CO)₁₀(CH₃CN)₂] with thianthrene at 80 °C leads to the nonacarbonyl dihydride compound [Os₃(CO)₉(μ-3,4-η²-C₁₂H₆S₂)(μ-H)₂] (1) and the 46-electron monohydride compound [Os₃(CO)₉(μ₃-η²-C₁₂H₇S₂)(μ-H)] (2). Compound 2 reacts reversibly with CO to give the CO adduct [Os₃(CO)₁₀(μ-η²-C₁₂H₇S₂)(μ-H)] (3) whereas with PPh₃ it gives the addition product [Os₃(CO)₉)(PPh₃)(μ-η²-C₁₂H₇S₂)(μ-H)] (4) as well as the substitution product 1,2-[Os₃(CO)₁₀ ((PPh₃)₂] (5) Compound 2 represents a unique example of an electron-deficient triosmium cluster in which the thianthrene ring is bound to cluster by coordination of the sulfur lone pair and a three-center-two-electron bond with the C(2) carbon which bridges the same edge of the triangle as the hydride. Electrochemical and DFT studies which elucidate the electronic properties of 2 are reported.

year: 2008

title: Āta whakarongo: Understanding whānau experiences of audiology early intervention

authors: Dargaville, Cynthia Michelle

subjects: Māori

abstract: For tamariki with hearing loss, early intervention is of critical importance in maximising speech and language, socio-emotional and academic development outcomes. Better hearing outcomes can be achieved by minimising diagnosis delays and initiating intervention treatment as soon as possible. Preliminary data from Waikato District Health Board indicated an equity gap at the point of diagnosis with persisting inequities for tamariki Māori during the delivery of early intervention services. High rates of appointment non-attendance within this group (27% Māori vs. 8% for non-Māori) are a cause for concern when approximately 50% of total appointments are for tamariki Māori. This research seeks to understand the experiences of Māori whānau accessing Waikato’s Audiology Early Intervention Service in order to identify changes the service can make to improve Māori engagement in the future. This study uses qualitative methodologies within a kaupapa Māori framework to investigate the access experiences of Māori whānau of tamariki identified with hearing loss. Interviews with six whānau from Hamilton city and rural Waikato provided rich narratives to inform changes to the Audiology Service to improve the hearing outcomes of tamariki Māori. Whānau shared systems and practical barriers that contributed to challenges with attending appointments including the location, appointment timing, travel and parking. From entering an unwelcoming waiting area, whānau described the added stress experienced to the depth of their emotional response to the hearing loss diagnosis. All shared positive interactions with staff and detailed what could have made their health experience better. After leaning into the kōrero and connecting to the whānau experience, a Manaaki-based pathway is proposed to support Māori ways of being, to ease whānau through the barriers and to combat the alienating experiences of engaging with the health system.

text: Āta whakarongo: Understanding whānau experiences of audiology early intervention For tamariki with hearing loss, early intervention is of critical importance in maximising speech and language, socio-emotional and academic development outcomes. Better hearing outcomes can be achieved by minimising diagnosis delays and initiating intervention treatment as soon as possible. Preliminary data from Waikato District Health Board indicated an equity gap at the point of diagnosis with persisting inequities for tamariki Māori during the delivery of early intervention services. High rates of appointment non-attendance within this group (27% Māori vs. 8% for non-Māori) are a cause for concern when approximately 50% of total appointments are for tamariki Māori. This research seeks to understand the experiences of Māori whānau accessing Waikato’s Audiology Early Intervention Service in order to identify changes the service can make to improve Māori engagement in the future. This study uses qualitative methodologies within a kaupapa Māori framework to investigate the access experiences of Māori whānau of tamariki identified with hearing loss. Interviews with six whānau from Hamilton city and rural Waikato provided rich narratives to inform changes to the Audiology Service to improve the hearing outcomes of tamariki Māori. Whānau shared systems and practical barriers that contributed to challenges with attending appointments including the location, appointment timing, travel and parking. From entering an unwelcoming waiting area, whānau described the added stress experienced to the depth of their emotional response to the hearing loss diagnosis. All shared positive interactions with staff and detailed what could have made their health experience better. After leaning into the kōrero and connecting to the whānau experience, a Manaaki-based pathway is proposed to support Māori ways of being, to ease whānau through the barriers and to combat the alienating experiences of engaging with the health system.

year: 2023