Synthese und Funktionalisierung magnetischer Nanopartikel

Magnetische Nanomaterialien sind aufgrund ihrer Anwendungsmöglichkeiten in Biotechnologie, Pharmazie, Katalyse und vielen weiteren Bereichen von Interesse. Die Kombination ihrer besonderen magnetischen Eigenschaften mit einer hohen spezifischen Oberfläche macht diese Materialien besonders für die selektive, magnetische Separation im Down-Stream-Processing biotechnologisch erzeugter Stoffe geeignet. Ziel der Arbeit war die Kontrolle der Partikelgröße und Größenverteilung bei der kontinuierlichen Synthese magnetischer Nanopartikel deren anschließende Funktionalisierung mit SiO2. Der Fokus lag hierbei in der Hochskalierung des Prozesses auf einen industriellen Maßstab. Hierzu wurde unter anderem die Kinetik der Magnetitsynthese durch Kopräzipitation von wässrigen Fe(II) und Fe(III) Lösungen mit gekoppelter Oxidation des Fe(II) untersucht und eine zuverlässige Methode zur Bestimmung der Partikelgrößenverteilung entwickelt. Dabei zeigte sich, dass bei der Synthese sehr breite Partikelgrößenverteilungen (/µ > 30%) und deutlich geringere Primärpartikelgrößen, als durch die Messergebnisse der spezifischen Oberfläche zu erwarten wäre, erzielt werden. Die numerische Simulation des Kristallisationsprozesses zeigte, dass der Fokussierungseffekt zu Beginn der Fällungsreaktion, praktisch keine Auswirkung auf die Magnetitbildung und damit auf die Erzielung einer engen Größenverteilung besitzt. Das Partikelwachstum und damit die Partikelgrößenverteilung wird maßgeblich durch einen koagulations- und Rekristallisationsmechanismus bestimmt. Zur Funktionalisierung wurde ein alternatives Verfahren zur kontrollierten Silikabeschichtung, das ohne einen Reinigungsschritt nach der Synthese auskommt, getestet. Durch die gezielte Beschichtung der Magnetit-Nanopartikel im Bereich von 0,5 bis 2,5 mg(SiO2) / m² kann der isoelektrische Punkt bis auf pH 3,5 kontrolliert abgesenkt und damit die DNA Bindekapazität der Partikel variiert werden

Drivers of groundwater utilization in water-limited rice production systems in Nepal

Most rice farmers in Nepal’s Terai region do not fully utilize irrigation during breaks in monsoon rainfall. This leads to yield losses despite abundant groundwater resources and ongoing expansion of diesel pumps and tubewell infrastructure. We investigate this puzzle by characterizing delay factors governing tubewell irrigation across wealth and precipitation gradients. After the decision to irrigate, different factors delay irrigation by roughly one week. While more sustainable and inexpensive energy for pumping may eventually catalyze transformative change, we identify near-term interventions that may increase rice farmers’ resilience to water stress in smallholder-dominated farming communities based on prevailing types of irrigation infrastructure.</p

Improving pumpset selection to support intensification of groundwater irrigation in the Eastern Indo-Gangetic Plains

Intensification of groundwater irrigation is central to goals of improving food security and reducing chronic poverty faced by millions of rural households across the eastern Indo-Gangetic Plains (EIGP) of Nepal and parts of eastern India. At present, levels of groundwater use and access in the EIGP lag far behind other areas of South Asia despite abundant available groundwater resources. A key reason for prevailing access constraints is the dependence on diesel pumpsets for accessing groundwater, which are typically unsubsidised and therefore expensive to purchase and operate. To date, efforts to reduce access costs have focused almost exclusively on how to incentivise adoption of alternative electric or solar-powered pumping technologies, which are viewed as being cheaper to operate and less environmentally damaging due to their lower operational carbon emissions. In contrast, there has been little attention paid to identifying opportunities to make existing diesel pump systems more cost effective for farmers to operate in order to support adaptation to climate change and reduce poverty. In this study, we use evidence from 116 detailed in-situ pump tests along with interviews with pumpset dealers, mechanics and farmers in the Nepal Terai to assess how and why fuel efficiency and operational costs of diesel pump irrigation are affected by farmers’ pumpset selection decisions. We show that costs diesel pumpset irrigation can be reduced significantly by supporting and incentivising farmers (e.g., through equipment advisories, improved supply chains for maintenance services and spare parts) to invest in newer low-cost, portable and smaller horsepower pumpset designs that are more effectively matched to local operating conditions in the EIGP than older Indian manufactured engines that have historically been preferred by farmers in the region. Such interventions can help to unlock potential for intensified irrigation water use in the EIGP, contributing to goals of improving agricultural productivity and resilience to climate extremes while also strengthening farmers capacity to invest in emerging low-carbon pumping technologies.</p

Global crop yields can be lifted by timely adaptation of growing periods to climate change

Adaptive management of crop growing periods by adjusting sowing dates and cultivars is one of the central aspects of crop production systems, tightly connected to local climate. However, it is so far underrepresented in crop-model based assessments of yields under climate change. In this study, we integrate models of farmers’ decision making with biophysical crop modeling at the global scale to simulate crop calendars adaptation and its effect on crop yields of maize, rice, sorghum, soybean and wheat. We simulate crop growing periods and yields (1986-2099) under counterfactual management scenarios assuming no adaptation, timely adaptation or delayed adaptation of sowing dates and cultivars. We then compare the counterfactual growing periods and corresponding yields at the end of the century (2080-2099). We find that (i) with adaptation, temperature-driven sowing dates (typical at latitudes >30°N-S) will have larger shifts than precipitation-driven sowing dates (at latitudes <30°N-S); (ii) later-maturing cultivars will be needed, particularly at higher latitudes; (iii) timely adaptation of growing periods would increase actual crop yields by ~12%, reducing climate change negative impacts and enhancing the positive CO2 fertilization effect. Despite remaining uncertainties, crop growing periods adaptation require consideration in climate change impact assessments

Towards sustainable groundwater systems in South Asia: Data exploration in Nalanda district in Bihar, India

Groundwater resources and irrigation systems are a fundamental consideration for sustainable and inclusive food system transitions in South Asia. Over the course of the latter part of the 20th century and the early 21st century, groundwater has become the primary source of irrigation water across South Asia and globally. The aquifers in Western and Peninsula regions in South Asia have faced water scarcity and groundwater depletion. But in the Eastern Gangetic Plains, aquifers are still considered underutilized by most planners and policymakers. This has resulted in increased investments in groundwater irrigation for water security and climate adaptation. However, the aquifer response to increasing irrigation water withdrawals remains poorly understood. To address this knowledge gap, TAFSSA is developing watershed assessment on sustainable groundwater use. Starting with Nalanda distric in Bihar, India, a relatively water scarce district within the Eastern Gangetic Plains. This research note reports on the initial findings from existing groundwater data and outlines key steps towards building a groundwater model to support sustainable groundwater management and planning

Global crop yields can be lifted by timely adaptation of growing periods to climate change

Adaptive management of crop growing periods by adjusting sowing dates and cultivars is one of the central aspects of crop production systems, tightly connected to local climate. However, it is so far underrepresented in crop-model based assessments of yields under climate change. In this study, we integrate models of farmers’ decision making with biophysical crop modeling at the global scale to simulate crop calendars adaptation and its effect on crop yields of maize, rice, sorghum, soybean and wheat. We simulate crop growing periods and yields (1986-2099) under counterfactual management scenarios assuming no adaptation, timely adaptation or delayed adaptation of sowing dates and cultivars. We then compare the counterfactual growing periods and corresponding yields at the end of the century (2080-2099). We find that (i) with adaptation, temperature-driven sowing dates (typical at latitudes >30°N-S) will have larger shifts than precipitation-driven sowing dates (at latitudes <30°N-S); (ii) later-maturing cultivars will be needed, particularly at higher latitudes; (iii) timely adaptation of growing periods would increase actual crop yields by ~12%, reducing climate change negative impacts and enhancing the positive CO2 fertilization effect. Despite remaining uncertainties, crop growing periods adaptation require consideration in climate change impact assessments

Patterns and Drivers of Agricultural Biodiversity in South Asia: A preliminary overview of a regional dataset

Food systems face multifaceted challenges ranging from inadequate supply of nutritious food products to a range of negative environmental impacts (Fable et al., 202; Rockstöm et al., 2020; Willet et al., 2019). Fuctional agricultural bidiversity has emerged as an important consideration that, if carefully managed, could help to improved food system outcomes through several pathways including production risk miigation, increased and diversified incomes and livelihoods, and potentially as a contributor to healthier diets (Gaitán-Cremaschi et al., 2018; Klerkx & Rose 2020). However, large-scale regional patterns and drivers of agricultural biodiversity in South Asia remain largely underexplored. To address this gap, TAFFSA is producing a regional agricultural biodiversity database that will support researchers and policy markers in better understanding diversification in the food system and the relationships between agrobiodiversity and key food system outcomes. The current dataset contains regional district-level production data from 2019-2022, depending on availability, and includes a dietary groupings of food groups. Preliminary results show that cereals are by far the largest food category, but also highlight spatial variation in the diversity of food production. Bangladesh, Pakistan, Northen and Eastern India, and Nepal appear to be more diverse and dedicate larger shares of cultivated land to cereals than Western and Central India. After fully harmonizing the data sources,this dataset will help to identify hotspots of agobiodiversity including diagnostics and drivers of diversification that can inform sustainable food system transitions

Ecological footprints of food systems in South Asia

Food systems in South Asia exert considerable pressure on climate systems, water systems, and biodiversity. Quantifying these impacts and is crucial for steering food systems transitions. However, approaches and assessments for environmental footprints of food systems remain largely fragmented in South Asia, especially for low-income and data-scarce regions. We address this knowledge gap with systematic scoping review of peer-reviewed literature to identify existing methods and datasets applicable for assessing the environmental footprints and planetary boundaries of food systems in South Asia. We find that such assessments have started to become more common, although many remain narrowly focused on reliant on Tier 1 type of approaches. Others are singular case studies or describe experiments. For example, most studies look either at carbon and/or water footprints of national dietary or production patterns and their relationship to ecosystem functioning. We also find a concentration of studies on specific crops or food products in select ecological boundaries. We consequent suggest two avenues for future research: First, consolidating a meso-scale overview of environmental impacts of food systems exercises and strategy development. Second, research is needed to generate sub-regional diagnostic datasets. These could be helpful in developing context-specific, data-driven, and socially desirable solutions to address the most actionable environmental impacts of food systems in South Asia

Impact of climate change on water resources and crop production in Western Nepal: Implications and adaptation strategies

Irrigation-led farming system intensification and efficient use of ground and surface water resources are currently being championed as a crucial ingredient for achieving food security and reducing poverty in Nepal. The potential scope and sustainability of irrigation interventions under current and future climates however remains poorly understood. Potential adaptation options in Western Nepal were analyzed using bias-corrected Regional Climate Model (RCM) data and the Soil and Water Assessment Tool (SWAT) model. The RCM climate change scenario suggested that average annual rainfall will increase by about 4% with occurrence of increased number and intensity of rainfall events in the winter. RCM outputs also suggested that average annual maximum temperature could decrease by 1.4 °C, and average annual minimum temperature may increase by 0.3 °C from 2021 to 2050. Similarly, average monthly streamflow volume could increase by about 65% from March–April, although it could decrease by about 10% in June. Our results highlight the tight hydrological coupling of surface and groundwater. Farmers making use of surface water for irrigation in upstream subbasins may inadvertently cause a decrease in average water availability in downstream subbasins at approximately 14%, which may result in increased need to abstract groundwater to compensate for deficits. Well-designed irrigated crop rotations that fully utilize both surface and groundwater conversely may increase groundwater levels by an average of 45 mm from 2022 to 2050, suggesting that in particular subbasins the cultivation of two crops a year may not cause long-term groundwater depletion. Modeled crop yield for the winter and spring seasons were however lower under future climate change scenarios, even with sufficient irrigation application. Lower yields were associated with shortened growing periods and high temperature stress. Irrigation intensification appears to be feasible if both surface and groundwater resources are appropriately targeted and rationally used. Conjunctive irrigation planning is required for equitable and year-round irrigation supply as neither the streamflow nor groundwater can provide full and year-round irrigation for intensified cropping systems without causing the degradation of natural resources