Understanding and Predicting Vadose Zone Processes

Vadose zone hydrologic and biogeochemical processes play a significant role in the capture, storage and distribution of contaminants between the land surface and groundwater. One major issue facing geoscientists in dealing with investigations of the unsaturated zone flow and transport processes is the evaluation of heterogeneity of subsurface media. This chapter presents a summary of approaches for monitoring and modeling of vadose zone dynamics in the presence of heterogeneities and complex features, as well as incorporating transient conditions. Modeling results can then be used to provide early warning of soil and groundwater contamination before problems arise, provide scientific and regulatory credibility to environmental management decision-making process to enhance protection of human health and the environment. We recommend that future studies target the use of RTMs to identify and quantify critical interfaces that control large-scale biogeochemical reaction rates and ecosystem functioning. Improvements also need to be made in devising scaling approaches to reduce the disconnect between measured data and the scale at which processes occur

Structures and processes of the initial ecosystem development phase in an artificial water catchment (Final report CRC/TR 38)

Objective of the Transregional Collaborative Research Centre (CRC/TR) 38 was the study of structures and processes of the initial ecosystem development. It was assumed that the initial phase is characterized by less structured and therefore less heterogeneous ecosystems. Thus, analysis of young ecosystems in their initial stages should provide better insights into ecosystem functioning. Following this basic concept, the idea of the CRC/TR 38 was to analyze the establishment of new structures and processes which lead to a growing structuring and in consequence to a growing complexity and heterogeneity in an artificially created watershed. Further, with the help of this step-by-step development of the ecosystem it was aimed to learn from occurring feedbacks, which appear between old and newly emerging structures and patterns in order to better understand also the behavior of more mature systems. Special emphasis was placed on the spatial and temporal dynamics of both evolving structures and related processes and their interactions. In summary, the CRC/TR 38 was able to identify a number of structures and processes that are considered to be relevant and specific for young systems.Ziel des Sonderforschungsbereichs/Transregio (SFB/TRR) 38 war die Untersuchung von Strukturen und Prozessen der initialen Ökosystemgenese. Es wurde angenommen, dass die initiale Entwicklungsphase durch geringere Strukturierung und damit durch eine geringere Heterogenität der Ökosysteme gekennzeichnet ist. Entsprechend sollte die Untersuchung von Ökosystemen in ihrer initialen Entwicklungsphase verbesserte Erkenntnisse zur Funktion von Ökosystemen bieten. Diesem Konzept folgend untersuchte der SFB/TRR 38 in einem künstlichen Wassereinzugsgebiet die Entwicklung von neuen Strukturen und Prozessen, die zu einer zunehmenden Strukturierung und damit zu einer zunehmenden Heterogenität führte. Weiterhin war beabsichtigt, mit Hilfe der schrittweisen Entwicklung des Ökosystems auftretende Rückkopplungsprozesse zwischen alten und sich neu etablierenden Strukturen und Mustern zu erkennen und damit auch das Verständnis der Funktionsweise gereifter Ökosysteme zu verbessern. Besonderes Augenmerk wurde auf die zeitliche und räumliche Dynamik sowohl der sich entwickelnden Strukturen als auch der damit verbundenen Prozesse und ihrer Interaktionen gelegt. Zusammenfassend kann gesagt werden, dass der SFB/TRR 38 in der Lage war, zahlreiche Strukturen und Prozesse zu identifizieren, die als relevant und spezifisch für junge Ökosysteme betrachtet werden können

Assessing Coastal Plain Risk Indices for Subsurface Phosphorus Loss

Phosphorus (P) Index evaluations are critical to advancing nutrient management planning in the United States. However, most assessments until now have focused on the risks of P losses in surface runoff. In artificially drained agroecosystems of the Atlantic Coastal Plain, subsurface flow is the predominant mode of P transport, but its representation in most P Indices is often inadequate. We explored methods to evaluate the subsurface P risk routines of five P Indices from Delaware, Maryland (two), Virginia, and North Carolina using available water quality and soils datasets. Relationships between subsurface P risk scores and published dissolved P loads in leachate (Delaware, Maryland, and North Carolina) and ditch drainage (Maryland) were directionally correct and often statistically significant, yet the brevity of the observation periods (weeks to several years) and the limited number of sampling locations precluded a more robust assessment of each P Index. Given the paucity of measured P loss data, we then showed that soil water extractable P concentrations at depths corresponding with the seasonal high water table (WEPWT) could serve as a realistic proxy for subsurface P losses in ditch drainage. The associations between WEPWT and subsurface P risk ratings reasonably mirrored those obtained with sparser water quality data. As such, WEPWT is seen as a valuable metric that offers interim insight into the directionality of subsurface P risk scores when water quality data are inaccessible. In the long term, improved monitoring and modeling of subsurface P losses clearly should enhance the rigor of future P Index appraisals

Geomorphology of the upper Mkhomazi River basin, KwaZulu-Natal, South Africa, with emphasis on late Pleistocene colluvial deposits

We present a 1:50 000 scale geomorphological map of the upper Mkhomazi River basin, located in the foothills of the Drakensberg mountains in KwaZulu-Natal Province, South Africa. The sub-horizontal strata of the Permo-Triassic Beaufort Group forms plateau interfluves with a concave valley slope morphology. Locally, thick sequences of late Pleistocene colluvial deposits and associated buried paleosols (Masotcheni Formation) infill first-order tributary stream valleys and extend across the adjacent lower slopes. Surface runoff processes preferentially incise into the poorly consolidated, highly erodible sediments causing severe gully erosion that is responsible for widespread land degradation and desertification phenomena. The main purpose of this work is to derive a geomorphological map of the study area focussing on the erosional landforms to understand their spatial distribution and their relation to the colluvial deposits. Finally, a local and regional stratigraphic correlation of colluvial deposits and associated buried palaeosol profiles is proposed