Assessing the performance of international laboratories analysing the stable isotope composition (δ15 N, δ18 O, δ17 O) of nitrate in environmental waters.

RATIONALE: Stable-isotope analyses of nitrate (NO3 - ) in various water sources are crucial for understanding nitrogen pollution and its impact on aquatic ecosystems. We evaluated the accuracy and precision of stable-isotope analyses of nitrate conducted by international laboratories. METHODS: Six samples with nitrate (2 mg L-1 NO3 - -N) were sent to 47 laboratories. The NO3 - had a 30-50 ‰ range of δ values for δ15 N, δ18 O and δ17 O. One blind duplicate evaluated reproducibility and the effect of water δ18 O. Laboratories used diverse methods to convert nitrate to N2 O, N2 , CO or O2 for stable-isotopic measurements (microbial, cadmium, titanium and elemental analysis) and isotope-ratio mass spectrometry or laser-based technologies. RESULTS: Thirty-six international laboratories (83 %) reported results; however, 23 % did not analyze the test samples due to technical difficulties. Of the reporting laboratories, 79 % and 84 % produced accurate δ15 N and δ18 O results falling within ±0.8 ‰ and ±1.1 ‰ of the benchmark values, respectively. Three laboratories produced only outliers. The duplicate revealed most laboratories gave internally reproducible results at appropriate analytical precision. For δ17 O, six laboratories reported results, but 67 % could not reproduce results within their claimed analytical measurement precision. One complication is a lack of nitrate reference materials for δ17 O. CONCLUSIONS: Analyst experience contributed to better performance, and underperformance was from compromised standards or inappropriate δ range of working reference materials. The stable isotope community must develop new nitrate reference materials for δ15 N spanning -20 ‰ to +80 ‰ and new materials for δ17 O.

The impact of agricultural transformation on water quality in a data-scarce, dryland landscape-a case study in the Bot River, South Africa.

Transformation of natural vegetation to cultivated fields has resulted in marked increases in water quality degradation and nutrient loading of rivers globally. In many developing countries, monitoring and evaluating the impacts of agriculture on water quality are limited by financial constraints and focus is given to large water bodies. This paper presents and discusses the results of a year-long monitoring of a typical river system in an agricultural setting, namely the Bot River, Western Cape, South Africa. Results show seasonal increases in N concentrations and SRP driven by surrounding agricultural activities. Water chemistry and changes to nutrient loads were found to be site specific, which demonstrates that monitoring programmes focussing on one or two sites are not representative of the entire catchment. Monitoring and reporting of small river systems are thus un(der)-represented in large databases such as the UN Global Environment Monitoring System for Freshwater (GEMS/Water) programme. The results highlight the importance of selecting appropriate and representative monitoring sites for these rivers when budgetary constraints limit the number of points that can be monitored sustainably. The findings should also be applicable to similar catchments in the Western Cape and beyond as they demonstrate the magnitude of seasonal nutrient fluxes in the system.

Using soil-moisture drought indices to evaluate key indicators of agricultural drought in semi-arid Mediterranean Southern Africa.

Droughts are natural disasters that globally affect large numbers of people each year. While different forms of drought exist, their severity and extent are dependent on critical points of onset. Understanding these onsets is crucial for water, food and energy security, as well as to develop climate change adaptation strategies. This study used the JAMS/J2000 hydrological model to detect agricultural drought using the Soil Moisture Deficit Index (SMDI). The Berg River catchment in Mediterranean South Africa was used as the pilot study area, which experienced a severe drought between 2015 and 2018 and where meteorological drought progressed into agricultural drought that resulted in significant crop reductions and job losses within the agricultural sector. To combat the effects of meteorological shortfalls, water resource management opted to curb agricultural reservoir releases, forcing farmers to rely on groundwater. Modelling results illustrated the importance of detecting headwater stress within the catchment, where in 2015/2017 headwater areas were affected for the first time over the 35-year simulation. Furthermore, regional changes to the groundwater system, during which severe to extremely severe SMDI values (-3 to -4) were simulated, is postulated to be caused by wide-spread groundwater overuse resulting in a 47% reduction in winter (JJA) and a 68% reduction in spring (SON) streamflow. Immediate streamflow reductions were observed, illustrating the low resilience of these systems to meteorological and agricultural droughts, as well as the impacts of water use behavioural changes. By using SMDI in conjunction with a well constrained hydrological model, crucial drought onset triggers can be detected as well as tipping points regarding water use behaviour. As climate change drives an increase in the occurrence of meteorological droughts in many parts of the world, understanding the advance of severe long-term effects is important for the development of effective adaption strategies to promote water, food and energy security.

When Your Breasts Might Not Work: Anticipatory Guidance for Health-Care Professionals.

There are many factors that can negatively impact a mother developing a copious milk supply and being able to exclusively breastfeed her infant. In this article, we present two case exemplars (glandular hypoplasia and breast reduction surgery) to illustrate that not all mothers may be able to develop a full milk supply, and that families should receive appropriate prenatal anticipatory education and guidance from childbirth educators and all health-care providers. Important considerations include the value of every drop of milk that the mother is able to produce, treating the milk as an important medical intervention, and developing a plan with the family for supplementation so the infant can receive adequate intake for growth.

Hydrocarbon-Rich Groundwater above Shale-Gas Formations: A Karoo Basin Case Study.

Horizontal drilling and hydraulic fracturing have enhanced unconventional hydrocarbon recovery but raised environmental concerns related to water quality. Because most basins targeted for shale-gas development in the USA have histories of both active and legacy petroleum extraction, confusion about the hydrogeological context of naturally occurring methane in shallow aquifers overlying shales remains. The Karoo Basin, located in South Africa, provides a near-pristine setting to evaluate these processes, without a history of conventional or unconventional energy extraction. We conducted a comprehensive pre-industrial evaluation of water quality and gas geochemistry in 22 groundwater samples across the Karoo Basin, including dissolved ions, water isotopes, hydrocarbon molecular and isotopic composition, and noble gases. Methane-rich samples were associated with high-salinity, NaCl-type groundwater and elevated levels of ethane, 4 He, and other noble gases produced by radioactive decay. This endmember displayed less negative δ13 C-CH4 and evidence of mixing between thermogenic natural gases and hydrogenotrophic methane. Atmospheric noble gases in the methane-rich samples record a history of fractionation during gas-phase migration from source rocks to shallow aquifers. Conversely, methane-poor samples have a paucity of ethane and 4 He, near saturation levels of atmospheric noble gases, and more negative δ13 C-CH4 ; methane in these samples is biogenic and produced by a mixture of hydrogenotrophic and acetoclastic sources. These geochemical observations are consistent with other basins targeted for unconventional energy extraction in the USA and contribute to a growing data base of naturally occurring methane in shallow aquifers globally, which provide a framework for evaluating environmental concerns related to unconventional energy development (e.g., stray gas).

Pre-drill Groundwater Geochemistry in the Karoo Basin, South Africa.

Enhanced production of unconventional hydrocarbons in the United States has driven interest in natural gas development globally, but simultaneously raised concerns regarding water quantity and quality impacts associated with hydrocarbon extraction. We conducted a pre-development assessment of groundwater geochemistry in the critically water-restricted Karoo Basin, South Africa. Twenty-two springs and groundwater samples were analyzed for major dissolved ions, trace elements, water stable isotopes, strontium and boron isotopes, hydrocarbons and helium composition. The data revealed three end-members: a deep, saline groundwater with a sodium-chloride composition, an old, deep freshwater with a sodium-bicarbonate-chloride composition and a shallow, calcium-bicarbonate freshwater. In a few cases, we identified direct mixing of the deep saline water and shallow groundwater. Stable water isotopes indicate that the shallow groundwater was controlled by evaporation in arid conditions, while the saline waters were diluted by apparently fossil meteoric water originated under wetter climatic conditions. These geochemical and isotopic data, in combination with elevated helium levels, suggest that exogenous fluids are the source of the saline groundwater and originated from remnant seawater prior to dilution by old meteoric water combined with further modification by water-rock interactions. Samples with elevated methane concentrations (>14 ccSTP/kg) were strongly associated with the sodium-chloride water located near dolerite intrusions, which likely provide a preferential pathway for vertical migration of deeply sourced hydrocarbon-rich saline waters to the surface. This pre-drill evaluation indicates that the natural migration of methane- and salt-rich waters provides a source of geogenic contamination to shallow aquifers prior to shale gas development in the Karoo Basin.