Papers by Clinton Rissmann
Geochimica et Cosmochimica Acta, Sep 1, 2017
A new geothermometer is proposed based on soil diffuse CO 2 flux and shallow temperature measurem... more A new geothermometer is proposed based on soil diffuse CO 2 flux and shallow temperature measurements • Measured drill hole temperatures compare well with geothermometry estimates for systems in New Zealand, Iceland and Argentina
Science of The Total Environment, Jul 1, 2019
Spatial variation in landscape attributes can account for much of the variability in water qualit... more Spatial variation in landscape attributes can account for much of the variability in water quality relative to land use on its own. Such variation results from the coupling between the dominant processes governing water quality, namely hydrological, redox, and weathering and gradients in key landscape attributes, such as topography, geology, and soil drainage. Despite the importance of 'process-attribute' gradients (PAG), few water quality models explicitly account for their influence. Here a processes-based water quality modelling framework is presented that more completely accounts for the role of landscape variability over water quality-Process-Attribute Mapping (PoAM). Critically, hydrochemical measures form the basis for the identification and mapping of effective landscape attributes, producing PAG maps that attempt to replicate the natural landscape gradients governing each dominant process. Application to the province of Southland (31,824 km 2), New Zealand, utilised 12 existing geospatial datasets and a total of 28,626 surface water, groundwater, spring, soil water, and precipitation analyses to guide the identification and mapping of 11 individual PAG. The ability of PAGs to replicate regional hydrological, redox, and weathering gradients was assessed on the accuracy with which the hydrochemical indicators of each dominant process (e.g. hydrological tracers, redox indicators) were estimated across 93 long-term surface water monitoring sites (cross-validated R 2 values of 0.75-0.95). Given hydrochemical evidence that PAGs replicate actual landscape gradients governing the dominant processes, they were combined with a land use intensity
Science of The Total Environment, 2019
Spatial variation in landscape attributes can account for much of the variability in water qualit... more Spatial variation in landscape attributes can account for much of the variability in water quality relative to land use on its own. Such variation results from the coupling between the dominant processes governing water quality, namely hydrological, redox, and weathering and gradients in key landscape attributes, such as topography, geology, and soil drainage. Despite the importance of 'process-attribute' gradients (PAG), few water quality models explicitly account for their influence. Here a processes-based water quality modelling framework is presented that more completely accounts for the role of landscape variability over water quality-Process-Attribute Mapping (PoAM). Critically, hydrochemical measures form the basis for the identification and mapping of effective landscape attributes, producing PAG maps that attempt to replicate the natural landscape gradients governing each dominant process. Application to the province of Southland (31,824 km 2), New Zealand, utilised 12 existing geospatial datasets and a total of 28,626 surface water, groundwater, spring, soil water, and precipitation analyses to guide the identification and mapping of 11 individual PAG. The ability of PAGs to replicate regional hydrological, redox, and weathering gradients was assessed on the accuracy with which the hydrochemical indicators of each dominant process (e.g. hydrological tracers, redox indicators) were estimated across 93 long-term surface water monitoring sites (cross-validated R 2 values of 0.75-0.95). Given hydrochemical evidence that PAGs replicate actual landscape gradients governing the dominant processes, they were combined with a land use intensity
Surface water and groundwater interactions are inherently complex, include multiple variables, an... more Surface water and groundwater interactions are inherently complex, include multiple variables, and occur across time and spatial scales. Understanding the connections and interactions of water resources is critical to sustainable water management in New Zealand and mandated under the National Objectives Framework. The aim of this study was to characterise the groundwater and surface water contribution to the lowland Waimatuku Stream, and identify the spatial and temporal hydrological pathways to streamflow using multiple hydrogeochemical methods. In particular, this project investigated whether intercatchment flow was occurring from the adjacent Aparima River. The characterisation of the water within the Waimatuku Stream was conducted using a multi-method approach including physical hydrology, isotopic and chemical analysis during stable flows and one period of event flow. Water samples were collected and analysed for a suite of water chemistry variables, stable water isotopes (δ 18...
• A few dominant processes (atmospheric, hydrological, redox, chemical and physical weathering) g... more • A few dominant processes (atmospheric, hydrological, redox, chemical and physical weathering) govern spatial variability in water quality • Hydrochemistry is used to guide the mapping of dominant processgradients and expert knowledge and machine learning is used to validate • Failure to consider dominant process-gradients in modeling and policy application risks poor water quality outcomes
Geochemistry: Exploration, Environment, Analysis
Groundwaters recovered from the Salar de Punta Negra and Monturaqui basins in the Atacama Desert ... more Groundwaters recovered from the Salar de Punta Negra and Monturaqui basins in the Atacama Desert of northern Chile exhibit distinctly different isotopic, major, trace, and porphyry copper elemental compositions related to contrasting morphostructural, geochemical, and hydrodynamic settings. Comparison of these distinct groundwater signatures with groundwaters from known porphyry copper deposits (Salar de Hamburgo and Spence Deposit), can be used to determine if either basin might be prospective for porphyry copper mineralization. Groundwaters within the Punta Negra Basin exhibit geochemical characteristics consistent with other closed basin settings throughout the arid Andes. Elemental and isotopic compositions within the Punta Negra Basin reflect closed basin evaporitic processes consistent with the hyperarid, volcanic setting of the central Andes. Pathfinder metals and isotopic compositions are not consistent with porphyry copper type mineralization as described for groundwaters within the Salar de Hamburgo Basin, and the Spence Deposit. Within the Monturaqui Basin the geochemical composition of groundwaters are characteristic of diffuse hydrothermal activity. Sulfur isotopic composition within the waters of the northern Monturaqui Basin exhibit δ34SCDT isotopic signatures that fall within the range for sulfide mineralization as reported for groundwaters in and around the Spence Deposit and the Salar de Hamburgo. However, porphyry copper related elements within the Monturaqui Basin are impoverished relative to groundwaters of the Spence and Escondida Deposit. Such impoverishment in porphyry related elements taken in conjunction with enriched δ13CPDB compositions, elevated groundwater temperatures, groundwater compositions dominated by HCO3, SO4, and Si, and the proximity of the Monturaqui Basin to the current magmatic arc are in keeping with a volcanic hydrothermal origin. In summary, the groundwater geochemistry of the Monturaqui and Punta Negra Basins are not indicative of porphyry-copper type mineralization.
This dataset was developed to evaluate the method for Rissmann et al. (submitted to JGR Biogeosci... more This dataset was developed to evaluate the method for Rissmann et al. (submitted to JGR Biogeosciences) 'A hydrochemically guided landscape-based classification for water quality: a case study application of process-attribute mapping (PoAM) at a national scale'. The surface water dataset was produced from the collation of chemical analyses of low, median, and event flows taken from 730 long-term surface water monitoring sites across the regions of Northland, Auckland, Waikato, Bay of Plenty, Manawatū-Whanganui, Canterbury, and Southland (representing 58 % of New Zealand), between 2017 and 2019. Across the same regions and for the same time period, data for the sample chemical constituents were collected at 2,191 long-term groundwater monitoring sites. The respective hydrochemical datasets for surface water and groundwater were subsequently combined with pre-existing hydrochemical data collected between 2007-2017 and median values calculated. The hydrochemical analytes includ...
This dataset was developed to evaluate the method for Rissmann et al. (submitted to JGR Biogeosci... more This dataset was developed to evaluate the method for Rissmann et al. (submitted to JGR Biogeosciences) 'A hydrochemically guided landscape-based classification for water quality: a case study application of process-attribute mapping (PoAM) at a national scale'. The data was produced from an independent surface water quality dataset, comprising 991 long-term monitoring sites across New Zealand. Water quality data was downloaded from Land Air Water Aotearoa (LAWA) for each year between 2014 – 2018 (https://www.lawa.org.nz/). Water quality data includes total nitrogen, nitrate nitrite nitrogen, ammoniacal nitrogen, total phosphorus, dissolved reactive phosphorus, turbidity, black disk (clarity), and E.coli as an indicator of microbial contamination. LAWA data is collected by each regional authority, with quality assurance performed according to National Environmental Monitoring and Reporting Standards (Davies-Colley et al., 2012). A minimum of 60 repeat measures are included f...
Nitrate losses from agriculture have significant impacts on freshwater, and occur when runoff gen... more Nitrate losses from agriculture have significant impacts on freshwater, and occur when runoff generation coincides with nitrogen excess in soil. Analysis of δ15N and δ18O in NO3 is well suited to characterize hot spots and hot moments when NO3 losses occur, by working back from impacted water to soil sources. New Zealand's lack of high δ18O atmospheric and fertilizer NO3 sources and the nation's intensive pastoral agriculture enable δ15N and δ18O in NO3 to differentiate soil and effluent sources, as well as processes linked to flow in different soil physiographic zones. This presentation reviews δ15N-NO3 and δ18O-NO3 results gathered across multiple catchments in three regions (Manawatu, Wairarapa, and Southland) with at least 100 measurements per region. River monitoring sites provide an integrated measure of sources, while fractionation associated with removal processes such as denitrification is largely lost. Within rivers, predominantly pastoral regions show a tight patt...
Baisden, W. T., Rissmann, C., Horton, T., Wells, N. S., & Clough, T. J. (2015, 1-4 December 2015)... more Baisden, W. T., Rissmann, C., Horton, T., Wells, N. S., & Clough, T. J. (2015, 1-4 December 2015). Can isotope tools rapidly fill gaps in knowledge of nitrate sources and sinks needed for water quality policy? 2015 NZHS Conference: From Data to Knowledge, Hamilton. <br>Aims Management of nitrate pollution through the implementation of New Zealand's National Policy Statement for Freshwater Management (2014) creates strong demand for understanding of the sources and sinks (attenuation) of nitrate within catchments. Over the last seven years, analysis of N and O isotopes in nitrate has been developed as a tracer technique capable of constraining the sources and sinks of nitrate in New Zealand. This presentation reviews this new tool's potential to reveal sources and sinks of nitrate that may be associated with "hot spots" and "hot moments" that are difficult to resolve with other techniques. <br> Method Isotopes in nitrate (δ15N and δ18O) were me...
IntroductionThe use of nitrogen and oxygen isotopes in nitrate (δ15N-NO3 and δ18O-NO3, respective... more IntroductionThe use of nitrogen and oxygen isotopes in nitrate (δ15N-NO3 and δ18O-NO3, respectively) has developed over the past 30 years to provide powerful tracer value, identifying sources and tracking processes related to nitrogen fluxes through the atmosphere, biosphere and hydrosphere. Globally, the high δ18O-NO3 values associated with atmospheric sources and oxidation processes has been most powerful in source identification for polluted northern hemisphere regions.In these regions, the signal in δ18O-NO3 is immense but highly variable, and therefore obscures nuanced studies of nitrogen cycling. Over a decade of intensive New Zealand studies have shown signatures dominated by nitrogen cycle processes without substantial atmospheric inputs, therefore offering unique potential to drill into the detail of controls on ecosystem nitrogen retention.<br>MethodsA range of programmes and activities have collected nitrate isotope samples with a 100 mL target size, preserved for i...
Declines in New Zealand's freshwater quality have led to legislative requirements under the 2... more Declines in New Zealand's freshwater quality have led to legislative requirements under the 2014 National Policy Statement on Freshwater Management (NPS-FM), which requires regional governments to set "objectives" and design policies accordingly. In most regions, increases in freshwater contaminants are derived largely from intensifying agriculture and come as N, P, pathogens or sediment, or a combination thereof. Here, the development and application of N and O isotopes as natural tracers for nitrate-N is examined as a case study, in the context of a wider hierarchy of observations such as N concentrations, flow and broader hydrochemistry used for NPS-FM implementation.<br>Baisden, W.T.; Ellis, T.; Rissman, C.; Moore, C.; Matthews, A. 2016. Designing Observation and Modeling Systems to Inform Decisions and Policies on Freshwater Objectives in New Zealand. AGU Fall Meeting, San Francisco. PA11B-1959 <br><br>
Accepted for Oral Presentation at https://www.nzhsconference.co.nz 30 Nov – 3 Dec 2021 Wellington... more Accepted for Oral Presentation at https://www.nzhsconference.co.nz 30 Nov – 3 Dec 2021 Wellington<br>In the wrong place, or at excessive concentrations, nutrients (nitrogen and phosphorus) and sediment become contaminants. Along with pathogens, they require reduction to improve water quality. Our Land and Water National Science Challenge (OLW NSC) and Ministry for the Environment (MfE) have commissioned a research programme 'Mapping Contaminants from Source to Sink' to inform both national and local government policy and planning on the fate of freshwater contaminants, specifically nitrogen and phosphorus species, sediment, and microbes in our environment and will be used to support the implementation of the National Policy Statement for Freshwater Management (2020). The overall objective of this project is to produce a national landscape classification for water quality to support contaminant risk assessment for policy option development. The classification units will...
Ore Geology Reviews, 2020
Abstract An abundance of world-class copper deposits in the Atacama region of northern Chile has ... more Abstract An abundance of world-class copper deposits in the Atacama region of northern Chile has made Chile the world’s leading copper producer. However, despite extensive exploration activities, the region remains a conundrum, with mature outcropping exploration plays juxtaposed with largely unexplored, extensive areas of post-mineral cover. This scenario offers exciting mineral exploration opportunities in the highly prospective and well-endowed, but locally concealed, metallogenic belts of northern Chile. Conventional exploration of local vast gravel plains or ignimbrite cover in northern Chile are hindered by the ineffectiveness of traditional geochemical techniques in covered settings and the commonly uneconomical costs associated with the systematic use of geophysics and extensive grid drilling. Porphyry deposits of the Atacama region have served as a test case for the use and testing of the effectiveness of hydrogeochemistry and isotopic vectoring in base metal exploration, with a comprehensive set of mineral exploration case studies, including examples of porphyry, epithermal and strata-bound deposits in Chile. Despite previous pilot studies, hydrogeochemistry remains a tool underutilized tool by many explorers, presumably due to a perception that sampling is challenging and laborious, and that data interpretation is intricate and complicated. Here we present a compilation of historical and current case studies to provide an overview of the most likely solute sources and sinks in the hyper-arid Atacama Desert as well as the resulting potential hydrogeochemical signatures that can be expected and their interpretation. The objective of this study is to provide a guide for the interpretation of hydrogeochemical exploration datasets.
Geochemistry: Exploration, Environment, Analysis, 2014
ABSTRACT LakeTexomaisalargeimpoundmentontheborderofTexasandOklahoma,formedfromtheconfluenceoftwo ... more ABSTRACT LakeTexomaisalargeimpoundmentontheborderofTexasandOklahoma,formedfromtheconfluenceoftwo river systems with different salinities, the Red River (total dissolved salt, TDS, of 2700–11 900 mg/l, average of 4862 mg/l) and the Washita River (TDS of 420–915mg/l, average of 701.4mg/l). Systematic analyses for major and trace elements were conducted of water samples collected spatially and with depth in the lake in different seasons. Overall, Lake Texoma waters are characterized by Na-Ca-Cl-SO4-type waters with spatial distribution shifting from Na-Cl type to Ca-SO4 type from the Red River arm to the main lake and to the Washita River arm. In addition, vertical and seasonal variations in major and trace elements concentrations indicate major elements in the lake are mainly controlled by different bedrock weather- ing from the two river systems. Trace elements that exhibit different distribution patterns to the major species are associated with variable sources such as river inflow, summer stratification effects, biological effects and anthropogenic activities. In Lake Texoma, differential inflow volumes and summer stratification are principal factors controlling the variation and geochemistry of lake waters and mixing dynamics.
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Papers by Clinton Rissmann