Monitoring the vegetation start of season (SOS) across the island of Ireland using the MERIS global vegetation index

The aim of this study was to develop a methodology, based on satellite remote sensing, to estimate the vegetation Start of Season (SOS) across the whole island of Ireland on an annual basis. This growing body of research is known as Land Surface Phenology (LSP) monitoring. The SOS was estimated for each year from a 7-year time series of 10-day composited, 1.2 km reduced resolution MERIS Global Vegetation Index (MGVI) data from 2003 to 2009, using the time series analysis software, TIMESAT. The selection of a 10-day composite period was guided by in-situ observations of leaf unfolding and cloud cover at representative point locations on the island. The MGVI time series was smoothed and the SOS metric extracted at a point corresponding to 20% of the seasonal MGVI amplitude. The SOS metric was extracted on a per pixel basis and gridded for national scale coverage. There were consistent spatial patterns in the SOS grids which were replicated on an annual basis and were qualitatively linked to variation in landcover. Analysis revealed that three statistically separable groups of CORINE Land Cover (CLC) classes could be derived from differences in the SOS, namely agricultural and forest land cover types, peat bogs, and natural and semi-natural vegetation types. These groups demonstrated that managed vegetation, e.g. pastures has a significantly earlier SOS than in unmanaged vegetation e.g. natural grasslands. There was also interannual spatio-temporal variability in the SOS. Such variability was highlighted in a series of anomaly grids showing variation from the 7-year mean SOS. An initial climate analysis indicated that an anomalously cold winter and spring in 2005/2006, linked to a negative North Atlantic Oscillation index value, delayed the 2006 SOS countrywide, while in other years the SOS anomalies showed more complex variation. A correlation study using air temperature as a climate variable revealed the spatial complexity of the air temperature-SOS relationship across the Republic of Ireland as the timing of maximum correlation varied from November to April depending on location. The SOS was found to occur earlier due to warmer winters in the Southeast while it was later with warmer winters in the Northwest. The inverse pattern emerged in the spatial patterns of the spring correlates. This contrasting pattern would appear to be linked to vegetation management as arable cropping is typically practiced in the southeast while there is mixed agriculture and mostly pastures to the west. Therefore, land use as well as air temperature appears to be an important determinant of national scale patterns in the SOS. The TIMESAT tool formed a crucial component of the estimation of SOS across the country in all seven years as it minimised the negative impact of noise and data dropouts in the MGVI time series by applying a smoothing algorithm. The extracted SOS metric was sensitive to temporal and spatial variation in land surface vegetation seasonality while the spatial patterns in the gridded SOS estimates aligned with those in landcover type. The methodology can be extended for a longer time series of FAPAR as MERIS will be replaced by the ESA Sentinel mission in 2013, while the availability of full resolution (300m) MERIS FAPAR and equivalent sensor products holds the possibility of monitoring finer scale seasonality variation. This study has shown the utility of the SOS metric as an indicator of spatiotemporal variability in vegetation phenology, as well as a correlate of other environmental variables such as air temperature. However, the satellite-based method is not seen as a replacement of ground-based observations, but rather as a complementary approach to studying vegetation phenology at the national scale. In future, the method can be extended to extract other metrics of the seasonal cycle in order to gain a more comprehensive view of seasonal vegetation development.

Longitudinal study of changes in body mass index, anthropometric measures, dietary intake and physical activity in cohorts of school-going Irish adolescents

The prevalence of obesity worldwide has increased dramatically over the last few decades. Poor dietary habits and low levels of exercise in adolescence are often maintained into adulthood where they can impact on the incidence of obesity and chronic diseases. A 3-year longitudinal study of anthropometric, dietary and exercise parameters was carried out annually (2005 - 2007) in 3 Irish secondary schools. Anthropometric measurements were taken in each year and analysed longitudinally. Overweight and obesity were at relatively low levels in these adolescents. Height, weight, BMI, waist and hip circumferences and TST increased significantly over the 3 years. Waist-to-hip ratio (WHR) decreased significantly over time. Boys were significantly taller than girls across the 3 years. A 3-day weighed food diary was used to assess food intake by the adolescents. Analysis of dietary intake data was determined using WISP©. Mean daily energy and nutrient intakes were reported. Mean daily energy and macronutrient intakes were analysed longitudinally. The adolescents’ diet was characterised by relatively high saturated fat intakes and insufficient fruit and vegetable consumption. The dietary pattern did not change significantly over the 3 years. Boys consumed more energy than girls over the study period. A validated questionnaire was used to assess physical activity and sedentary activity levels. Boys were substantially more active and had higher energy expenditure estimates than girls throughout the study. A significant longitudinal decrease in physical activity levels among the adolescents was observed. Both genders spent more than the recommended amount of time (hrs/day) pursing sedentary activities. The dietary pattern in these Irish adolescents is relatively poor. Of additional concern is the overall longitudinal decrease in physical activity levels. Promoting consumption of a balanced diet and increased exercise levels among adolescents will help to reduce future public health care costs due to weight-related diseases.

Toxicity of manufactured nano-ZnO to Lemna minor

The rapid development of nanotechnology has led to a rise in the large-scale production and commercial use of engineered nano-ZnO. Engineered/manufactured nano-ZnO are applied in a broad range of products such as drugs, paints, cosmetics, abrasive agents and insulators. This can result in the unintended exposure of human beings to nano-ZnO and will inevitably result in the release of nano-ZnO in to the environment. Thus, it is necessary to assess the risk of nano-ZnO to the environment. In this thesis the toxicity of nano-ZnO was analysed using the aquatic, primary producer lesser duckweed (Lemna minor), and the mechanism of toxicity was analysed. Both short-term (one week) and long-term (six weeks) toxicity of nano-ZnO (uncoated) were determined. Results show that the toxicity of nano-ZnO added to the aquatic growth medium increases with increasing concentration and that toxicity accumulates with exposure time. A study of nano-ZnO dissolution reveals that the main reason for nano-ZnO toxicity on Lemna minor is the release of Zn ions. Nano-ZnO dissolution is pH dependent, and toxicity matches the release of Zn2+. Functional coating materials are commonly added to nano-ZnO particles to improve specific industrial applications. To test if coating materials contribute to nano-ZnO toxicity on lesser duckweed, the effect of silane coupling agent (KH550) coated nano-ZnO on Lemma minor was investigated. Results show that coating can decrease the release of Zn ions, which reduces toxicity to Lemna minor, in contrast to uncoated particles. Another commonly hypothesized reason for nano-ZnO toxicity is the formation of Reactive Oxygen Species (ROS) on the particles surface. As part of this thesis, the ROS formation induced by nano-ZnO was studied. Results show that nano-ZnO catalyse ROS formation and this can negatively affect duckweed growth. In conclusion, this work has detailed potentially toxic effects of nano-ZnO on Lemna minor. This study has also provides references for future research, and informs regulatory testing for nanoparticle toxicity. Specifically, the outcomes of this study emphasize the importance of exposure time, environmental parameters and coating material when analysing NPs toxicity. Firstly, impacts of longer exposure time should be studied. Secondly, environmental parameters such as pH and medium-composition need to be considered when investigating NPs toxicity. Lastly, coating of NPs should always be considered in the context of NPs toxicity, and similar NPs with different coatings require separate toxicity tests.