Net Depletion Research Articles

Evaluation of crop water stress index of wheat by using machine learning models.

The Crop Water Stress Index (CWSI), a pivotal indicator derived from canopy temperature, plays a crucial role in irrigation scheduling for water conservation in agriculture. This study focuses on determining CWSI (by empirical method) for wheat crops in the semi-arid region of western Uttar Pradesh, India, subjected to varying irrigation treatments across two cropping seasons (2021-2022 and 2022-2023). The aim is to investigate further the potential of four machine learning (ML) models-support vector regression (SVR), random forest regression (RFR), artificial neural network (ANN), and multiple linear regression (MLR) to predict CWSI. The ML models were assessed based on determination coefficient (R2), mean absolute error (MAE), and root mean square error (RMSE) under diverse scenarios created from eight distinct input combinations of six variables: air temperature (Ta), canopy temperature (Tc), vapor pressure deficit (VPD), net solar radiation (Rn), wind speed (U), and soil moisture depletion (SD). SVR emerges as the top-performing model, showcasing superior results over ANN, RFR, and MLR. The most effective input combination for SVR includes Tc, Ta, VPD, Rn, and U (R2 = 0.997, MAE = 0.901%, RMSE = 2.223%). Meanwhile, both ANN and MLR achieve optimal results with input combinations involving Tc, Ta, VPD, Rn, U, and SD (R2 = 0.992, MAE = 2.031%, RMSE = 3.705%; R2 = 0.759, MAE = 13.95%, RMSE = 19.98%, respectively). For RFR, the ideal input combination comprises Tc, Ta, VPD, and U (R2 = 0.951, MAE = 5.023%, RMSE = 9.012%). The study highlights the considerable promise of ML models in predicting CWSI, proposing their future application in integration into an irrigation decision support system (IDSS) for crop stress mitigation and efficient water management in agriculture.

Lithium Volatilization and Phase Changes during Aluminum-Doped Cubic Li6.25La3Zr2Al0.25O12 (c-LLZO) Processing

Stabilized Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) is a Li+-conducting ceramic with ionic conductivities approaching 1 mS-cm. Processing c LLZO so that it is suitable for use as a solid state electrolyte in all solid state batteries, however, is challenging due to the formation of secondary phases at elevated temperatures. The work described in this manuscript examines the formation of one such secondary phase La2Zr2O7 (LZO) formed during sintering c LLZO at 1000 °C. Specifically, spatially resolved Raman spectroscopy and X-ray Diffraction (XRD) measurements have identified gradients in Li distributions in the Li ion (Li+)-conducting ceramic Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) created by thermal processing. Sintering c-LLZO under conditions relevant to solid state Li+ electrolyte fabrication conditions lead to Li+ loss and the formation of new phases. Specifically, sintering for 1 h at 1000 °C leads to Li+ depletion and the formation of the pyrochlore lanthanum zirconate (La2Zr2O7 or LZO), a material known to be both electronically and ionically insulating. Circular c-LLZO samples are covered on the top and bottom surfaces, exposing only the 1.6 mm-thick sample perimeter to the furnace’s ambient air. Sintered samples show a radially symmetric LZO gradient, with more LZO at the center of the pellet and considerably less LZO at the edges. This profile implies that Li+ diffusion through the material is faster than Li+ loss through volatilization, and that Li+ migration from the center of the sample to the edges is not completely reversible. These conditions lead to a net depletion of Li+ at the sample center. Findings presented in this work suggest new strategies for LLZO processing that will minimize Li+ loss during sintering, leading to a more homogeneous material with more reproducible electrochemical behavior.

Emergence of red, star-forming galaxies (red misfits) in a ΛCDM universe

ABSTRACT We investigate the formation of red misfits (RM) using a cosmological, hydrodynamical simulation from the eagle project. Similar to observations, the RM possess less dust, higher stellar metallicities, and older stellar populations compared to blue, star-forming galaxies (BA) at the same $M_\star$. Lagrangian particle-tracking reveals that the older ages of RM have resulted from a combined effect of higher star formation efficiency (SFE), and the earlier onset and faster net depletion of their interstellar medium (ISM). For the centrals, the latter was partially due to higher efficiency of escape from ISM, driven by stronger stellar and/or active galactic nucleus feedback (depending on the mass). There was an additional contribution to this escape from gas stripping for satellite RM, as suggested by the higher group masses ($\gtrsim 0.5$ dex) and $\mathrm{H_2}/\mathrm{H}\, {\rm{\small I}}$ ratios ($\gtrsim 0.3$ dex). Moreover, accretion of circumgalactic gas (CGM) on to the galaxy has been less efficient for the satellites. On the metallicity front, the offsets are largely due to the disparity in SFE, causing varying degrees of enrichment through the mass transfers associated with stellar winds and supernovae. We ascribe this SFE disparity to the lower specific angular momentum (j) of freshly accreted CGM for RM, which ultimately manifested in the ISM kinematics due to interactions with cooling flows. The impact on $j_{\rm ism}$ was further intensified by poorer alignment with the flow’s $\vec{j}$, particularly for the satellites. Our results illuminate potential origins of RM, and motivate further exploration of this peculiar class through a synergy between observations and simulations.

Management of soil cover and tillage regimes in upland rice-sweet corn systems for better system performance, energy use and carbon footprints

This study investigates the effects of tillage and mulching regimes on rice-sweet corn systems in the lower Gangetic plains, focusing on region-specific and crop-specific impacts on soil-crop-environmental parameters. The experiment consisted of three levels of tillage: conventional (CT), minimum (MT), and zero (ZT), and four levels of mulching: live, leaf litter, paddy straw, and no mulching. The results show that ZT tillage resulted in higher bulk density (BD) compared to other treatments, despite an increase in soil organic carbon (SOC). Live and leaf litter mulching led to slight reductions in BD in the upper soil layers. CT resulted in net depletion of SOC whereas ZT registered a positive sequestration rate of 1.19 Mg ha−1 yr−1. Live and leaf litter mulching increased SOC sequestration by 42.6% and 38.8% compared to paddy straw mulching, respectively. Initially, ZT resulted in a 10.3% reduction in system productivity compared to CT, while MT yields were comparable to CT. However, mulching regimes consistently improved production by 16.4%–25.2% as compared to no mulch. ZT and MT were found to be more affordable than CT, with cost savings of 18.2% and 6.8%, respectively. ZT had the highest B: C ratio, indicating better economic efficiency. Among the mulching treatments, live mulching was the most economical. Both ZT and MT saved input energy by approximately 22.9% and 13.5%, respectively compared to CT. Live mulching resulted in the highest net energy and energy output. Compared to CT, ZT reduced carbon footprint (CF) by 41.5 and 22.2% in rice and sweet corn, respectively. MT scored midway between ZT and CT in all parameters. CT exhibited several limitations, including high input energy requirements, high cost of cultivation, poor economic efficiency, negative environmental impacts, and loss of SOC. ZT initially experienced yield reduction and lower net returns in the early years. Therefore, MT was identified as the best alternative in the initial years before transitioning completely to ZT, as it provided comparable yields to CT with better overall benefits. Among the soil cover regimes, live mulching was found to be the most favorable option across all dimensions.

The misconception of soil organic carbon sequestration notion: When do we achieve climate benefit?

AbstractSoil organic carbon (SOC) sequestration is a key function of natural and semi‐natural ecosystems. Restoring this property in terrestrial ecosystems has become central to the EU's climate change mitigation and adaptation strategies. However, SOC sequestration is a widely misunderstood concept. The different methodological approaches used to investigate and compare SOC stock under sustainable agricultural practices play a key role in reinforcing misconceptions about this complex process. This commentary paper aimed not only to provide a clear definition of SOC sequestration, but also to interpret the results that can be obtained for SOC stock change estimation using the SOC stock difference and the paired comparison methods, as well as to identify the soil carbon‐related processes that achieve climate mitigation. SOC sequestration can be defined as the progressive increase in a site's SOC stock compared with pre‐intervention via a net depletion and transfer of atmospheric CO2 into the soil, where it is retained as soil organic matter (SOM), by plants, plant residues, or other organic solids such as the material derived from the organic fraction of farming solid waste, which can be used as a fertilizer (e.g., manure, compost, biochar, and digestate), and that is produced or derived from that land unit. To date, the most appropriate way to determine whether a land unit's soil is a sink or rather a source of atmospheric CO2 is to implement the SOC stock difference method, provided the non‐occurrence of carbon exchange between ecosystems.

Very short-lived halogens amplify ozone depletion trends in the tropical lower stratosphere

In contrast to the general stratospheric ozone recovery following international agreements, recent observations show an ongoing net ozone depletion in the tropical lower stratosphere (LS). This depletion is thought to be driven by dynamical transport accelerated by global warming, while chemical processes have been considered to be unimportant. Here we use a chemistry–climate model to demonstrate that halogenated ozone-depleting very short-lived substances (VSLS) chemistry may account for around a quarter of the observed tropical LS negative ozone trend in 1998–2018. VSLS sources include both natural and anthropogenic emissions. Future projections show the persistence of the currently unaccounted for contribution of VSLS to ozone loss throughout the twenty-first century in the tropical LS, the only region of the global stratosphere not projecting an ozone recovery by 2100. Our results show the need for mitigation strategies of anthropogenic VSLS emissions to preserve the present and future ozone layer in low latitudes.

Net zero climate remediations and potential terminal depletion of global critical metal resources: A synoptic geological perspective

• Climate change accords led to widespread acceptance of Net Zero by 2060 targets. • Critical metals depletion making low carbon technology production impossible. • Climate change in geological perspective is slow incremental not catastrophic. • A reset in Net Zero ambitions should be made for the future. Over the past two decades, concerns about anthropogenic CO 2 emissions have led to computer-based climate models of the consequences, first on global warming and then on more general climate change. The more extremes of these models have been used to engender concerns about climate events that could be catastrophic for global populations even though natural climate change has always been incremental with only periodic large volcanic eruptions producing short-term catastrophic changes due to massive additions of aerosols to the atmosphere. Climate change accords have led to widespread acceptance of Net Zero by 2060 targets. However, indicative modelling of the nexus between clean energy and the critical metals required for low carbon solar and wind technologies and electric vehicles and their chargers indicates that many metals, particularly Co, Ni, Cu, Se, Ag, Cd, In, Te, and Pt, may be severely to terminally depleted by 2060, making further low carbon technology production impossible. Mineral exploration and currently unmined deposits with high risk factors are only likely to be able to replace these non-renewable metals at lower grades in more inaccessible or deeper mines, leading to even further increases in conventional energy for mining and metallurgy and consequent cost of the low carbon technology revolution. There is no current indication that recycling can replace the critical metal stocks. The heterogeneous global distribution of both mineral deposits containing the critical metals and production points could become a geopolitical issue if global security declines. These factors combined with the slow incremental, rather than catastrophic, changes related to climate change, suggest that a reset in Net Zero ambitions should be made to consider a more multicomponent plan for the future that involves a balanced portfolio of least polluting energy sources that do not cause serious depletion of affordable metal resources for the future. Graphical Abstract. .

Biomass and Nutrient Accumulation by Dual-Purpose Hemp and Concurrent Soil Profile Water Depletion at Manhattan, KS, in 2021

Hemp has garnered interest as a potential crop that is not constrained by the typical food, feed, and fuel market channels. Although hemp varieties are available for the production of either grain, fiber, or both (dual-purpose: both grain and fiber) markets, little research-based information is available on hemp growth and water use in Kansas environments. In 2019, Kansas State University researchers began conducting experi­ments to characterize hemp growth, nutrient uptake, and soil water depletion at three locations representing the precipitation gradient across Kansas. In 2021, one fiber and one grain variety were evaluated with and without fertilizer nitrogen. Soil water content and biomass accumulation were monitored in plots with full nitrogen fertil­izer. Multiple plantings of the experiment at Haysville had to be abandoned because heavy rains soon after planting prevented successful stand establishment. The Colby experiment was abandoned because dry soils prevented successful stand establishment. Results from the experiment at Manhattan confirmed the benefit of nitrogen fertilizer, which roughly doubled total biomass yield. Although total biomass yield was similar for the two varieties, more of that yield was partitioned to grain in the grain variety, and stalks in the fiber variety. Nutrient uptake patterns were similar to those observed the previous year, with nitrogen and potassium accumulation occurring at a faster rate than dry matter, and phosphorus accumulation lagging that of dry matter. Carbon accumu­lation closely followed total dry matter accumulation. Hemp appeared to extract soil water to a depth of 5 feet because soil water content did not change at deeper depths. The sum of net depletion of the soil profile water plus precipitation was 14.64 inches, but some of the precipitation came in intense events causing a portion to run off. As an indeterminate species, hemp continues vegetative growth after flowering begins, increasing the probability that some grain will be produced even when resources are limited. Across three experiments conducted in Kansas in 2020 and 2021, stalk yields have varied by a factor of 1.5, and grain yields by a factor of 13.3. Relatively stable stalk yield coupled with more variable grain yield reveals hemp’s potential ability to adjust growth to match the inconsistent growing conditions typical of Kansas.

Biomass and Nutrient Accumulation by Dual-Purpose Hemp and Concurrent Soil Profile Water Depletion at Three Locations in Kansas in 2022

Hemp has garnered interest as a potential crop that is not constrained by the typical food, feed, and fuel market channels. Although hemp varieties are available for either grain, fiber, or both (dual-purpose: both grain and fiber) markets, little information is available on hemp growth and water use in Kansas environments. Experiments were conducted at three locations representing the precipitation gradient across Kansas in 2022 to characterize hemp growth, nutrient uptake, and soil water depletion. One fiber and one grain variety were evaluated with and without fertilizer nitrogen at Manhattan, Haysville, and Scandia, KS. Both non-irrigated and fully irrigated plots were evaluated at Scandia. Soil water content and biomass accumulation were monitored in plots with full nitrogen fertilizer. Results from the 2022 season confirmed the benefit of nitrogen fertilizer. Although total biomass yield was similar for the two varieties, more of that yield was partitioned to grain in the grain variety and to stalks in the fiber variety. Nutrient uptake patterns were similar to those observed for hemp in previous years and documented in other crops. Nitrogen and potassium accumulation occurred at a faster rate than dry matter, and phosphorus accumulation lagged that of dry matter. Carbon accumulation closely followed total dry matter accumulation. The sum of net depletion of the soil profile water plus precipitation averaged 17.3 inches across the three locations in 2022, but some of the precipitation came in intense events that resulted in runoff. Relatively stable stalk yield coupled with more variable grain yield reveals hemp’s ability to adjust growth to match the inconsistent growing conditions typical of Kansas.

The cerium isotope fingerprints of redox fluctuation in bauxites

We measured the Ce concentration, oxidation state, and isotope composition of bauxites developed on the Columbia River Basalts (CRBs) to evaluate the impacts of redox and non-redox processes on the Ce isotopic variability on Earth's surface. Bauxites recovered from drill cores show upward increasing Ce concentration (5.4–88.7 μg/g) and overall depletion of Ce (mass transfer coefficient, τCe,Nb: -0.96 to -0.52, i.e., net depletion of 52-96% relative to their parent CRBs). There is a wide range of the Ce anomaly (Ce/Ce⁎) from 0.4 to 6.3 and 0.6 to 1.4 in the Cowlitz and Columbia bauxites, respectively. The most positive Ce anomalies appear at the shallow regolith (2-5 m depth). Cerium primarily presents in its trivalent form in deposited exogenous materials (wind-blown dust from an old, weathered region of the continent) and primary CRBs. There is a downward increase in the fraction of Ce (IV) in the regolith. Bauxite δ142Ce ranges from -0.161±0.034 to -0.018±0.043‰ and -0.277±0.034 to -0.046±0.034‰ in the Cowlitz and Columbia profiles, respectively. The Ce isotope record reflects the redox cycle of Ce and Mn and is masked by dust accretion on the top. The enrichment of Ce (IV) occurs in the transition zone (the bottom of the shallow regolith) with minor Ce isotope shifts from the CRBs (δ142Ce from -0.080±0.034 to -0.04±0.034‰) likely caused by minor isotopic fractionation linked to O2-driven CeO2 precipitation. There are negative Ce isotope shifts from the basaltic parents and the enrichment of oxidized Ce and Mn in the deep regolith (5-9 m depth), where large isotopic fractionation probably induced by Ce oxidative adsorption on MnO2 plays a vital role. The vertical difference between Ce/Ce⁎ and δ142Ce may be attributed to the climatic oxidation-reduction cycle of Mn and Ce, leaving discrete CeO2 grains in the shallow regolith while transferring isotopically light Ce associated to oxidized Mn deposits down to the deep regolith. We conclude that a combination of Ce species isotopes and anomalies potentially records terrestrial redox status and fluctuation.

Causes and consequences of the Macta basin closure, Algeria

ABSTRACT The Macta River basin in Algeria is under pressure. A water accounting of the basin demonstrates the severity of the crisis, with a net water depletion rate estimated at 93–142%, depending on the assumptions made. This reflects the overexploitation of the aquifers whose annual depletion is estimated at between 86 and 126 Mm3. This paper first discusses the causes of basin overbuilding and the over-allocation of water, and then analyses the economic, social and environmental consequences. It calls for a stricter water accounting of river basins in Algeria as the 2030 Agenda for Sustainable Development and its SDG 6 are implemented.

Grazing by wild red deer can mitigate nutrient enrichment in protected semi-natural open habitats

Eutrophication through atmospheric nutrient deposition is threatening the biodiversity of semi-natural habitats characterized by low nutrient availability. Accordingly, local management measures aiming at open habitat conservation need to maintain habitat-specific nutrient conditions despite atmospheric inputs. Grazing by wild herbivores, such as red deer (Cervus elaphus), has been proposed as an alternative to mechanical or livestock-based measures for preserving open habitats. The role of red deer for nutrient dynamics in protected open habitat types, however, is yet unclear. Therefore, we collected data on vegetation productivity, forage removal, quantity of red deer dung and nutrient concentrations in vegetation and dung from permanent plots in heathlands and grasslands (eight plots à 225 m2 per habitat type) on a military training area inhabited by a large population of free-ranging red deer over one year. The annual nutrient export of nitrogen (N) and phosphorus (P) by red deer grazing was higher than the nutrient import through red deer excreta, resulting in an average net nutrient removal of 14 and 30 kg N ha−1 a−1 and 1.1 and 3.3 kg P ha−1 a−1 in heathlands and grasslands, respectively. Even when considering approximate local atmospheric deposition values, net nutrient depletion due to red deer grazing seemed very likely, notably in grasslands. Demonstrating that grazing by wild red deer can mitigate the effects of atmospheric nutrient deposition in semi-natural open habitats similarly to extensive livestock grazing, our results support the idea that red deer are suitable grazing animals for open habitat conservation.

Identifying the ozone-neutral aircraft cruise altitude

Depletion of stratospheric ozone, and the associated increase in population exposure to UV radiation, is an environmental consequence of high-altitude, supersonic aviation. Assessments of the impacts of emissions from subsonic aircraft – which fly at lower altitudes – have instead shown that they produce a net increase, rather than decrease, in global net ozone, suggesting the existence of an intermediate “column ozone neutral” cruise altitude. Knowing this altitude and its variation with factors such as latitude, season, and fuel composition could provide a pathway towards reducing the environmental impacts of aviation, but would require a prohibitive number of atmospheric simulations. We instead use the newly developed GEOS-Chem tropospheric-stratospheric adjoint to identify the location of the column ozone-neutral aircraft cruise altitude as a function of these factors. We show that, although the mean ozone neutral altitude is at 13.5 km globally, this varies from 14.6 km to 12.5 km between the equator and 60°N. This altitude varies by less than a kilometer between seasons, but the net depletion resulting from flying at greater altitudes varies by a factor of two. We also find that eliminating fuel sulfur would result in a neutral altitude 0.5–1.0 km greater than when conventional jet fuel is burned. Our results imply that a low Mach number supersonic aircraft burning low-sulfur fuel (e.g. biofuels) may be able to achieve net zero global ozone change. However, for a fleet to achieve ozone neutrality will require careful consideration of the non-linear variation in sensitivity with altitude and latitude.

Reduced groundwater use and increased grain production by optimized irrigation scheduling in winter wheat–summer maize double cropping system—A 16-year field study in North China Plain

Optimizing irrigation strategies to increase water utilization efficiency and achieve higher yield is vital for balancing groundwater use and improving food security during water shortage in the North China Plain (NCP). Based on a 16-year field experiment (2003–2018) using seven irrigation schedules from W0M0 to W4M3 (numbers are irrigation times in wheat (W) and maize (M) season, 75 mm each) in the winter wheat–summer maize double cropping system, we analyzed annual total water consumption ( ET a ) and groundwater table change in terms of net groundwater depletion, annual total grain yield, water productivity (WP), irrigation water productivity (IWP) and marginal benefit of the whole wheat–maize system. Relationship between yield or WP and irrigation or ET a were also revealed. Results showed that (1) total ET a increased as irrigation input increased, ranging from 427.3 mm (Rainfed, W0M0) to 891.0 mm (W4M3). Soil water storage contributed nearly 30% to ET a for winter wheat under water deficit conditions. Pre-sowing soil water storage played an important role in improving the annual yield and WP of both wheat and maize by promoting germination, seedling emergence and root growth; (2) the rainfed treatment (W0M0) was best for mitigating the groundwater table decline (0.1 m yr -1 ), followed by W1M1 (0.5 m yr -1 ) and W2M1 (0.8 m yr -1 ). Groundwater table decline in M2W2 almost overlapped the observed data at the station (1.1 m yr -1 ). In W3M2, the farmers’ traditional practice, the groundwater table declined by 1.4 m yr -1 , obviously over exploitation, while W4M2 and W4M3 declined by almost 2.0 m yr -1 ; (3) the relationship between total annual yield and irrigation (or ET a ) followed a quadratic curve. Total annual yield significantly increased from W0M0 to M1W1 (25%) to M2M1 (5%) and then kept stable. Average annual WP decreased as irrigation increased, from 2.4 kg m -3 (W0M0) to 1.6 kg m -3 (W4M3). Average annual IWP and marginal benefit also declined as irrigation increased. These results over 16 years indicated that the W2M1 is the most balanced irrigation regime for wheat– maize rotation to mitigate groundwater decline, maintain grain production, and improve water use efficiency in the NCP. ● A 16 - year field experiment of seven irrigation regimes for wheat-maize was conducted. ● ET a increased and water productivity decreased with increasing irrigation amount. ● W2M1 was the best optimized irrigation regime for balancing groundwater use and yield.

Evaluation of GRACE derived groundwater storage changes in different agro-ecological zones of the Indus Basin

The Gravity Recovery and Climate Experiment (GRACE) has recently been identified as a useful tool for monitoring changes in groundwater storage (GWS), especially in areas with sparse groundwater monitoring networks. However, GRACE's performance has not been evaluated in the highly heterogeneous Indus Basin (IB) to date. The objective of this study was thus (i) to evaluate GRACE's performance in two distinctively different agro-ecological zones of the IB, and (ii) to quantify the trend of groundwater abstraction over 15 years (i.e., from 2002 to 2017). To capture this heterogeneity at the IB, the two different agro-ecological zones were selected: i) the Kabul River Basin (KRB), Afghanistan, and ii) the Lower Bari Doab Canal (LBDC) command area in Pakistan. The groundwater storage anomalies (GWSA) for both regions were extracted from random pixels. The results show a correlation (R2) of 0.46 for LBDC and 0.32 for the KRB, between the GWSA and in-situ measurements. The results further reveal a mean annual depletion in GWSA of −304.2 ± 749 and −301 ± 527 mm at the LBDC and the KRB, respectively. Overall, a net GWS depletion during 2002–2017 at the LBDC and KRB was 4.87 and 4.82 m, respectively. The GWSA’s response to precipitation analyzed through cross-correlation shows a lag of 4 and 3 months at the KRB and the LBDC, respectively. The GWSA's poor correlation with the in-situ measurements particularly in the mountainous region of the KRB is driven by the 4 months lag time unlike in the LBDC (i.e. 3 months); besides, the observations wells are sparse and limited. The complex geomorphology and slope of the landscape also cause discrepancies in the correlation of the in-situ measurements and the GRACE-derived changes in GWS at the two different agroecological zones of the IB. The spatially averaged GWSA in monthly time steps is another reason for the lower correlation between GRACE-based GWSA estimates and point-based in-situ measurements. Therefore, care must be taken while using GRACE's output in regions with heterogeneous geomorphologic features.

Apparent Seasonal Bias in Delta Outflow Estimates as Revealed in the Historical Salinity Record of the San Francisco Estuary: Implications for Delta Net Channel Depletion Estimates

Accurate estimates of freshwater flow to the San Francisco Estuary are important in successfully regulating this water body, in protecting its beneficial uses, and in accurately modeling its hydrodynamic and water-quality transport regime. For regulatory purposes, freshwater flow to the estuary is not directly measured; rather, it is estimated from a daily balance of upstream Delta inflows, exports, and in-Delta water use termed the net Delta outflow index (NDOI). Field research in the 1960s indicated that NDOI estimates are biased low in summer–fall and biased high in winter–spring as a result of conflating Delta island evapotranspiration estimates with the sum of ungauged hydrologic interactions between channels and islands referred to as net channel depletions. In this work, we employed a 50-year observed salinity record along with gauged tidal flows and an ensemble of five empirical flow-salinity (X2) models to test whether a seasonal bias in Delta outflow estimates could be inferred. We accomplished this objective by conducting statistical analyses and evaluating whether model skill could be improved through seasonal NDOI flow adjustments. Assuming that model residuals are associated with channel depletion uncertainty, our findings corroborate the 1960s research and suggest that channel depletions are biased low in winter months (i.e., NDOI is biased high) and biased high in late summer and early fall months (i.e., NDOI is biased low). The magnitude of seasonal bias, which can reach 1,000 cfs, is a small percentage of typical winter outflow but represents a significant percentage of typical summer outflow. Our findings were derived from five independently developed models, and are consistent with the physical understanding of water exchanges on the islands. This work provides motivation for improved characterization of these exchanges to improve Delta outflow estimates, particularly during drought periods when water supplies are scarce and must be carefully managed.

A comparison of calcium and phosphorus in components of fertile and size-matched unbanded Nile crocodile eggs

ABSTRACT Research in other species suggests that the source of embryonic calcium (Ca) and phosphorus (P) for Crocodylus niloticus is likely yolk and shell. Using inductively coupled plasma optical emission spectroscopy (ICP-OES), the Ca and P concentration and content of 30 fertile eggs was determined within 10 days prior to anticipated hatching, and compared with those of size-matched unbanded eggs (eggs that failed to form an opaque band around the lesser circumference, indicative of presumed infertility). Shell contained the highest Ca concentration and content, followed by the foetus, followed by the intra-abdominal yolk. Foetal tissue had the highest P concentration and content, followed by intra-abdominal yolk. The Ca and P concentration of intra-abdominal yolk of foetuses in fertile eggs varied more widely than did the yolk of unbanded eggs, based on coefficient of variation. Ca concentration of fertile egg yolk was in some cases found to exceed that of the yolk of unbanded eggs, suggesting that Ca is stored there after being removed from the shell, however, yolk Ca content was consistently lower in fertile than in unbanded eggs, indicating net yolk Ca depletion. Yolk P concentration and content of fertile eggs was consistently lower than that of unbanded eggs, suggesting a net depletion of yolk P reserves, without replenishment. The Nile crocodile appears to follow the classic archosaurian pattern of Ca mobilisation, whereby the shell supplies the majority of foetal Ca, but the intra-abdominal yolk contains substantial Ca reserves for use by the hatchling. This study provides clinicians and researchers with information on sample collection and analysis of Nile crocodile egg and foetal tissue, provides baseline descriptive data on Ca and P concentration and content, discusses the effect of potential covariates on Ca and P concentration and content, and discusses the movement of Ca and P from reserves within the egg to the developing foetus.

Covariation of Airborne Biogenic Tracers (CO2, COS, and CO) Supports Stronger Than Expected Growing Season Photosynthetic Uptake in the Southeastern US

AbstractThe Atmospheric Carbon Transport (ACT)‐America Earth Venture mission conducted five airborne campaigns across four seasons from 2016 to 2019, to study the transport and fluxes of Greenhouse gases across the eastern United States. Unprecedented spatial sampling of atmospheric tracers (CO2, carbon monoxide [CO], carbonyl sulfide [COS]) related to biospheric processes offers opportunities to improve our qualitative and quantitative understanding of seasonal and spatial patterns of biospheric carbon uptake. Here, we examine co‐variation of boundary layer enhancements of CO2, CO, and COS across three diverse regions: the crop‐dominated Midwest, evergreen‐dominated South, and deciduous broadleaf‐dominated Northeast. To understand the biogeochemical processes controlling these tracers, we compare the observed co‐variation to simulated co‐variation resulting from model‐ and satellite‐ constrained surface carbon fluxes. We found indication of a common terrestrial biogenic sink of CO2 and COS and secondary production of CO from biogenic sources in summer throughout the eastern US, driven by stomatal conductance. Upper Midwest crops drive CO2 and COS depletion from early to late summer. Northeastern temperate forests drive CO2 and COS depletion in late summer. The unprecedented ACT‐America flask samples uncovered evidence that southern humid temperate forests photosynthesize and absorb CO2 and COS, and emit CO precursors, deep into the growing season. Satellite‐ constrained carbon fluxes capture much of the observed seasonal and spatial variability, but underestimate the magnitude of net CO2 and COS depletion in the South, indicating a stronger than expected net sink of CO2 in late summer. Additional sampling of the South will more accurately constrain underlying biological processes and climate sensitivities governing southern carbon dynamics.

The impact of tourism, renewable energy, and economic growth on ecological footprint and natural resources: A panel data analysis

Global warming and the conservation of resources is a challenge for policymakers to achieve sustainable development. This study develops a new global tourism index, based on standard index-making procedures (indicators selection, winsorization, normalization, aggregation). It explores the impact of the global tourism index, renewable energy, gross domestic product, trade openness, urbanization, and cultural globalization on total ecological footprints and net resource depletion in 47 high-income countries, 33 upper-middle-income countries, 35 lower-middle-income countries, and 13 low-income countries from 1995 to 2019. The environmental Kuznets curve hypothesis has been validated in high-income (turning point: 41.010), lower-middle-income (turning point: 38.919), and low-income (turning point: 31.553) countries. The regression analysis confirmed a reduction in ecological footprint due to an increase in renewable energy use (all panels), urbanization (upper middle and low-income countries), and cultural globalization (lower-middle and low-income countries). The increase in ecological footprints was reported due to an increase in the gross domestic product (all panels), trade (high and low-income countries), and urbanization (high-income countries). The reduction in resource depletion was occurred due to an increase in tourism (high, upper-middle, and lower-middle-income countries), renewable energy (all panels), urbanization (upper middle and low-income countries), and cultural globalization (all panels). It is recommended to expand tourism activities and renewable energy. It is suggested to educate people about sustainable utilization of natural resources.

Trace metals and metalloids and Ga/Al ratios in grey shale weathering profiles along a climate gradient and in batch reactors

Shale is an important lithology globally due to its wide spatial abundance and potentially high trace metal and metalloid (TMM) geochemistry, which can be potentially inherited by its overlying soils. Unlike other soils, shale-derived soils inherit organic matter and oxides (Fe and Mn) which promote accumulation and retention of both geogenic and exogeneous TMMs. Here, we explore TMMs in seven grey shales weathering profiles along a north–south transect spanning the western flank of the Appalachian Mountains from New York to Tennessee. Overall, total TMM concentrations in the grey shales and their soils were below concentrations known to be toxic and below concentrations observed in black shales. Tau values show that shale-derived soils are net accumulators of many TMMs (As, Cd, Co, Cu, Ni, Pb, Sb, Sn and Zn) but others (Cr, W, and V) showed a net depletion. Many of the TMMs had high proportions (5–50%) that were sequestered in reducible phases (amorphous and crystalline Fe oxides) but few TMMs were associated with oxidizable phases (organic matter, reduced minerals). Sulfides and oxides (Mn nor Fe) were not detected by X-ray diffraction (<2% g/g). TMM accumulation and release during weathering was not extensively related to climate or soil development/age as we hypothesized, potentially due to localized effects of vegetation, geomorphology, pollution, and physicochemical parameters of the shale. Our laboratory batch reactor experiments indicated that some TMMs had highest release rates under oxic, acidic conditions with organic acids present (Cr, Ga, Sn, Sb, and W) implying aluminosilicate dissolution control or under slightly acidic, reduced conditions (As, Cd, Co, Cu, Ni, Pb, V, and Zn), suggesting association with geogenic oxides. Total Ga/Al ratios in rock to soil profiles were not varying significantly across the climate-soil development gradient, despite batch reactor acidic conditions generating low Ga/Al ratios. This implies weathering of shales is dominated by processes that do not fractionate Ga/Al ratio (organic or inorganic colloid production) as our laboratory results suggests oxic, acidic aluminosilicate weathering should generate a high Ga/Al solid phase.