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Publications

2021
Hendel, E. ; Bacher, H. ; Oksenberg, A. ; Walia, H. ; Schwartz, N. ; Peleg, Z. Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral axial conductance alleles. Plant, Cell & EnvironmentPlant, Cell & EnvironmentPlant Cell Environ 2021, n/a. Publisher's VersionAbstract
ABSTRACT Root axial conductance which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro-system, grain-filling is typically occurring during declining water availability (i.e. terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical, and physiological traits, with several hotspots harboring co-localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field-based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate. This article is protected by copyright. All rights reserved.
Shiff, S. ; Helman, D. ; Lensky, I. M. Worldwide continuous gap-filled MODIS land surface temperature dataset. Scientific Data 2021, 8 74 - 74. Publisher's VersionAbstract
Satellite land surface temperature (LST) is vital for climatological and environmental studies. However, LST datasets are not continuous in time and space mainly due to cloud cover. Here we combine LST with Climate Forecast System Version 2 (CFSv2) modeled temperatures to derive a continuous gap filled global LST dataset at a spatial resolution of 1 km. Temporal Fourier analysis is used to derive the seasonality (climatology) on a pixel-by-pixel basis, for LST and CFSv2 temperatures. Gaps are filled by adding the CFSv2 temperature anomaly to climatological LST. The accuracy is evaluated in nine regions across the globe using cloud-free LST (mean values: R2 = 0.93, Root Mean Square Error (RMSE) = 2.7 °C, Mean Absolute Error (MAE) = 2.1 °C). The provided dataset contains day, night, and daily mean LST for the Eastern Mediterranean. We provide a Google Earth Engine code and a web app that generates gap filled LST in any part of the world, alongside a pixel-based evaluation of the data in terms of MAE, RMSE and Pearson’s r.
Michael, Y. ; Helman, D. ; Glickman, O. ; Gabay, D. ; Brenner, S. ; Lensky, I. M. Forecasting fire risk with machine learning and dynamic information derived from satellite vegetation index time-series. 2021, 764, 142844. Publisher's VersionAbstract
Fire risk mapping – mapping the probability of fire occurrence and spread – is essential for pre-fire management as well as for efficient firefighting efforts. Most fire risk maps are generated using static information on variables such as topography, vegetation density, and fuel instantaneous wetness. Satellites are often used to provide such information. However, long-term vegetation dynamics and the cumulative dryness status of the woody vegetation, which may affect fire occurrence and spread, are rarely considered in fire risk mapping. Here, we investigate the impact of two satellite-derived metrics that represent long-term vegetation status and dynamics on fire risk mapping – the long-term mean normalized difference vegetation index (NDVI) of the woody vegetation (NDVIW) and its trend (NDVIT). NDVIW represents the mean woody density at the grid cell, while NDVIT is the 5-year trend of the woody NDVI representing the long-term dryness status of the vegetation. To produce these metrics, we decompose time-series of satellite-derived NDVI following a method adjusted for Mediterranean woodlands and forests. We tested whether these metrics improve fire risk mapping using three machine learning (ML) algorithms (Logistic Regression, Random Forest, and XGBoost). We chose the 2007 wildfires in Greece for the analysis. Our results indicate that XGBoost, which accounts for variable interactions and non-linear effects, was the ML model that produced the best results. NDVIW improved the model performance, while NDVIT was significant only when NDVIW was high. This NDVIW–NDVIT interaction means that the long-term dryness effect is meaningful only in places of dense woody vegetation. The proposed method can produce more accurate fire risk maps than conventional methods and can supply important dynamic information that may be used in fire behavior models.
Weksler, S. ; Rozenstein, O. ; Haish, N. ; Moshelion, M. ; Wallach, R. ; Ben-Dor, E. Detection of Potassium Deficiency and Momentary Transpiration Rate Estimation at Early Growth Stages Using Proximal Hyperspectral Imaging and Extreme Gradient Boosting. Sensors 2021, 21. Publisher's VersionAbstract
Potassium is a macro element in plants that is typically supplied to crops in excess throughout the season to avoid a deficit leading to reduced crop yield. Transpiration rate is a momentary physiological attribute that is indicative of soil water content, the plant’s water requirements, and abiotic stress factors. In this study, two systems were combined to create a hyperspectral–physiological plant database for classification of potassium treatments (low, medium, and high) and estimation of momentary transpiration rate from hyperspectral images. PlantArray 3.0 was used to control fertigation, log ambient conditions, and calculate transpiration rates. In addition, a semi-automated platform carrying a hyperspectral camera was triggered every hour to capture images of a large array of pepper plants. The combined attributes and spectral information on an hourly basis were used to classify plants into their given potassium treatments (average accuracy = 80%) and to estimate transpiration rate  
2020
Zaarur, S. ; Stein, M. ; Adam, O. ; Mingram, J. ; Liu, J. ; Wu, J. ; Raveh-Rubin, S. ; Erel, Y. Synoptic stability and anomalies in NE China inferred from dust provenance of Sihailongwan maar sediments during the past ∼80 kyr. 2020, 239, 106279. Publisher's VersionAbstract
The paleo-synoptic conditions that prevailed during the past ∼80 kyr in northeastern China are inferred from the elemental and Sr–Nd isotopic compositions of Lake Sihailongwan Maar sediments. The detrital fraction in the lake sediments is dominated by aeolian input of felsic-rock origin, with little contribution of local volcanic material. Based on the isotopic Sr–Nd composition of the lake core-sediments, we postulate that the deserts of northern China are the main source of allochthonous particles to the lake throughout the past ∼80 kyr. Northwesterly winds associated with the East Asian winter monsoon and high latitude westerlies are the main carriers of dust from these deserts to the lake. The deserts of central China are an additional minor dust source. The episodic dust input from these deserts results from anomalous dry southwesterly winds. These could be related to either El Niño conditions, or to delays in the onset of the East Asian summer monsoon rains.
Xue, B. ; Wang, G. ; Xiao, J. ; Helman, D. ; Sun, W. ; Wang, J. ; Liu, T. Global convergence but regional disparity in the hydrological resilience of ecosystems and watersheds to drought. 2020, 591, 125589. Publisher's VersionAbstract
Drought is a major climate disturbance that can lower vegetation productivity and induce widespread vegetation die-off, which in turn can have a profound effect on the water cycle. Therefore, quantification of vegetation-specific responses to drought is essential to predict the impacts of climate change on ecosystem services. We used two previously-suggested quantitative metrics – dynamic deviation (d) and elasticity (e) based on the Budyko framework –to evaluate site- and watershed-level hydrological resilience of different plant functional types (PFTs) to drought. By using data from 41 FLUXNET sites and 2275 watersheds, we found a global convergence in hydrological resilience to drought across a variety of PFTs. Hydrological resilience of vegetation was related to drought intensity and water use efficiency. A greater hydrological resilience was found in PTFs in drier areas than in wetter areas, while this greater hydrological resilience was related to the coefficient of variation in precipitation. We also found that PFTs with a larger water use efficiency had higher hydrological resilience, particularly in drier regions, indicating adaptation strategies to changes in local climate conditions. Our findings can shed light on how ecosystems and watersheds dominated by different PFTs will respond to future climatic change and inform water resources management.
Helman, D. ; Zaitchik, B. F. ; Funk, C. Climate has contrasting direct and indirect effects on armed conflicts. Environmental Research Letters 2020, 15, 104017. Publisher's VersionAbstract
There is an active debate regarding the influence that climate has on the risk of armed conflict, which stems from challenges in assembling unbiased datasets, competing hypotheses on the mechanisms of climate influence, and the difficulty of disentangling direct and indirect climate effects. We use gridded historical non-state conflict records, satellite data, and land surface models in a structural equation modeling approach to uncover the direct and indirect effects of climate on violent conflicts in Africa and the Middle East (ME). We show that climate–conflict linkages in these regions are more complex than previously suggested, with multiple mechanisms at work. Warm temperatures and low rainfall direct effects on conflict risk were stronger than indirect effects through food and water supplies. Warming increases the risk of violence in Africa but unexpectedly decreases this risk in the ME. Furthermore, at the country level, warming decreases the risk of violence in most West African countries. Overall, we find a non-linear response of conflict to warming across countries that depends on the local temperature conditions. We further show that magnitude and sign of the effects largely depend on the scale of analysis and geographical context. These results imply that extreme caution should be exerted when attempting to explain or project local climate–conflict relationships based on a single, generalized theory.
Gabay, M. ; Raveh-Rubin, S. ; Peleg, M. ; Fredj, E. ; Tas, E. Is oxidation of atmospheric mercury controlled by different mechanisms in the polluted continental boundary layer vs. remote marine boundary layer?. Environmental Research Letters 2020, 15, 064026. Publisher's VersionAbstract
Deposition of atmospheric mercury is of global concern, primarily due to health effects associated with efficient bioaccumulation of mercury in marine food webs. Although oxidation of gaseous elementary mercury (GEM), the major fraction of atmospheric mercury, is a critical stage in regulating atmospheric mercury deposition efficiency, this oxidation is currently not well-characterized, limiting modeling-based assessments of mercury in the environment. Based on a previous study, we hypothesized that the oxidation of GEM is predominantly controlled by multistep bromine- and chlorine-induced oxidation (MBCO) in the remote marine boundary layer (RMBL), and by photochemical smog oxidants, primarily ozone (O3) and hydroxyl radical (OH), in the polluted continental boundary layer (PCBL). To test this hypothesis, we used the following analyses: (i) application of a newly developed criterion to evaluate the gaseous oxidized mercury (GOM)–O3 association based on previous studies in the RMBL and PCBL; (ii) measurement-based box simulations of GEM oxidation in the RMBL and at a PCBL site; and (iii) measurement-based analysis of photochemical oxidation vs. other processes which potentially influence GOM. Our model simulations indicated that the MBCO mechanism can reproduce GOM levels in the RMBL, but not in the PCBL. Our data analysis suggested the important role of photochemical smog oxidants in GEM oxidation in the PCBL, potentially masked by the effect of relative humidity and entrainment of free tropospheric air.
Dayan, C. ; Fredj, E. ; Misztal, P. K. ; Gabay, M. ; Guenther, A. B. ; Tas, E. Emission of biogenic volatile organic compounds from warm and oligotrophic seawater in the Eastern Mediterranean. Atmospheric Chemistry and Physics 2020, 20, 12741–12759. Publisher's Version
Dalal, A. ; Shenhar, I. ; Bourstein, R. ; Mayo, A. ; Grunwald, Y. ; Averbuch, N. ; Attia, Z. ; Wallach, R. ; Moshelion, M. A Telemetric, Gravimetric Platform for Real-Time Physiological Phenotyping of Plant–Environment Interactions. 2020, e61280. Publisher's VersionAbstract
Food security for the growing global population is a major concern. The data provided by genomic tools far exceeds the supply of phenotypic data, creating a knowledge gap. To meet the challenge of improving crops to feed the growing global population, this gap must be bridged.Physiological traits are considered key functional traits in the context of responsiveness or sensitivity to environmental conditions. Many recently introduced high-throughput (HTP) phenotyping techniques are based on remote sensing or imaging and are capable of directly measuring morphological traits, but measure physiological parameters mainly indirectly. This paper describes a method for direct physiological phenotyping that has several advantages for the functional phenotyping of plant–environment interactions. It helps users overcome the many challenges encountered in the use of load-cell gravimetric systems and pot experiments. The suggested techniques will enable users to distinguish between soil weight, plant weight and soil water content, providing a method for the continuous and simultaneous measurement of dynamic soil, plant and atmosphere conditions, alongside the measurement of key physiological traits. This method allows researchers to closely mimic field stress scenarios while taking into consideration the environment’s effects on the plants’ physiology. This method also minimizes pot effects, which are one of the major problems in pre-field phenotyping. It includes a feed-back fertigation system that enables a truly randomized experimental design at a field-like plant density. This system detects the soil-water-content limiting threshold (θ) and allows for the translation of data into knowledge through the use of a real-time analytic tool and an online statistical resource. This method for the rapid and direct measurement of the physiological responses of multiple plants to a dynamic environment has great potential for use in screening for beneficial traits associated with responses to abiotic stress, in the context of pre-field breeding and crop improvement.
Topaz, T. ; Boxall, A. ; Suari, Y. ; Egozi, R. ; Sade, T. ; Chefetz, B. Ecological Risk Dynamics of Pharmaceuticals in Micro-Estuary Environments. Environmental Science & TechnologyEnvironmental Science & Technology 2020. Publisher's VersionAbstract
Micro-estuarine ecosystems have a surface area <1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to the effects of chemical pollution. Due to the fluctuating flow conditions of base flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently struggling to provide ecological services. This 2 year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n = 280) at as high as 18 μg L–1 in flood events and 14 μg L–1 in base flow. The pharmaceutical mixture composition was affected by flow conditions with carbamazepine dominating the base flow and caffeine dominating flood events. The median annual risk quotients for fish, crustaceans, and algae were 19.6, 5.2, and 4.5, respectively, indicating that pharmaceuticals pose a high risk to the ecosystem. Ibuprofen, carbamazepine, and caffeine contributed most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk in comparison to the more frequently studied large estuarine systems.Micro-estuarine ecosystems have a surface area <1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to the effects of chemical pollution. Due to the fluctuating flow conditions of base flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently struggling to provide ecological services. This 2 year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n = 280) at as high as 18 μg L–1 in flood events and 14 μg L–1 in base flow. The pharmaceutical mixture composition was affected by flow conditions with carbamazepine dominating the base flow and caffeine dominating flood events. The median annual risk quotients for fish, crustaceans, and algae were 19.6, 5.2, and 4.5, respectively, indicating that pharmaceuticals pose a high risk to the ecosystem. Ibuprofen, carbamazepine, and caffeine contributed most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk in comparison to the more frequently studied large estuarine systems.
Helman, D. ; Zaitchik, B. F. Temperature anomalies affect violent conflicts in African and Middle Eastern warm regions. 2020, 63, 102118. Publisher's VersionAbstract
Several studies have linked high temperatures to increases in violent conflicts. The findings are controversial, however, as there has been no systematic cross-sectional analysis performed to demonstrate the generality of the proposed relationship. Moreover, the timescale of temperature/violence relationships have not been fully investigated; it is unclear how short versus long-term, or seasonal and inter-annual temperature variability contribute to the likelihood or frequency of violent events. We here perform systematic regional and grid-based longitudinal analyses in Africa and the Middle East for the period 1990–2017, using geolocated information on armed conflicts and a recently released satellite-based gridded temperature data set. We find seasonal synchrony between temperature and number of armed conflicts at the regional scale (climatic region), as well as a positive relationship in temperature and conflict anomalies on inter-annual timescales at the grid cell level (for the entire African and ME region). After controlling for ‘location effects’, we do not find that long-term warming has affected armed conflicts for the last three decades. However, the effects of temperature anomalies are stronger in warmer places (~5% increase per 10 °C, P < 0.05), suggesting that populations living in warmer places are more sensitive to temperature deviations. Taken together, these findings imply that projected warming and increasing temperature variability may enhance violence in these regions, though the mechanisms of the relationships still need to be exposed.
Helman, D. ; Mussery, A. Using Landsat satellites to assess the impact of check dams built across erosive gullies on vegetation rehabilitation. 2020, 730, 138873. Publisher's VersionAbstract
Gully erosion, a process of soil removal due to water accumulation and runoff, is a worldwide problem affecting agricultural lands. Building check dams perpendicular to the flow direction is one of the suggested control practices to stabilize this process. Though there are many studies on the effect of erosive controls on land stabilization, few examine its effect on the rehabilitation of vegetation. Here we use information from the satellites Landsat-7 (1999–2018) and Landsat-8 (2013–2018) to assess the effect of soil check dams built during 2012 across three gullies with distinct structures in a dryland area on vegetative cover and water status. We use a time series analysis technique to decompose Landsat-derived soil adjusted vegetation index (SAVI) into woody (SAVIW) and herbaceous (iSAVIH) contributions. The integral over the seasonal signal of the normalized difference water index (iNDWI) was used to assess changes in water status in the gully. We used herbaceous biomass collected in the field in 2014–2017 to validate iSAVIH as a proxy of herbaceous biomass. Our results show that following the construction of the check dams, the change in woody vegetation cover is best described by a sigmoid model with an increase of ~57% (95% CI: 39%–76%; p < 0.0001), while the herbaceous vegetation increases linearly at a rate of ~71% per year (95% CI: 48%–93% y−1; p < 0.0001). The correlation between iSAVIH and herbaceous biomass (R2 = 0.56; n = 16; p < 0.001) corroborates this increase. We found higher herbaceous productivity in the deeper gully compared to the shallower gullies but not statistically different increase rates. An increase in iNDWI of ~68% (95% CI: 43%–95%; p < 0.0001) likely implies an improved water infiltration rate that favored the vegetation expansion. Our satellite-based approach can be used to assess the impact of erosive control practices on vegetation rehabilitation in heterogeneous gullies.
Mor-Mussery, A. ; Helman, D. ; Agmon, Y. ; Ben-Shabat, I. ; El-Frejat, S. ; Golan, D. G. The indigenous Bedouin farmers as land rehabilitators—Setup of an action research programme in the Negev. Land Degradation & DevelopmentLand Degradation & DevelopmentLand Degrad Dev 2020, n/a. Publisher's VersionAbstract
Abstract The Negev suffers from enhanced land degradation, mostly due to lack of awareness about its state, and hostility between the region's indigenous Bedouin farmers and the authorities. In order to examine a potential solution to this 'Lose?Lose' situation, a unique project is underway, with the collaboration of the Yeroham Municipality and the adjacent Rahma Bedouin farmers' village. The concept of this ongoing Programme is based on bidirectional knowledge transfer of farming data between the farmers and land scientists, aimed to adapt Bedouin traditional cultivation methods and transform them into methods that restore the environment and are also profitable. In order to reach this goal, a highly knowledgeable Bedouin liaison person was appointed to carry out the project together with the Coordinating Team. A comprehensive study and tour were carried out in order to analyze the different landforms and Bedouin cultivation preferences. An initial survey was carried out and data from literature collected in order to determine the ecological and archaeological characteristics of the ecosystem. The area was then prepared for agricultural utilization by removing widespread garbage and dealing with wadis that have been filled with construction waste. This project, which integrates soil enhancement, agriculture utilization, and traditional Bedouin farming, aims for rehabilitation of the northern Negev gullied areas. However, the implementation of the study concept in the field is accompanied by many challenges related to Bedouin interclan communication and the diverse types of degraded lands.
Gorovits, R. ; Sobol, I. ; Akama, K. ; Chefetz, B. ; Czosnek, H. Pharmaceuticals in treated wastewater induce a stress response in tomato plants. Sci Rep 2020, 10, 1856.Abstract
Pharmaceuticals remain in treated wastewater used to irrigate agricultural crops. Their effect on terrestrial plants is practically unknown. Here we tested whether these compounds can be considered as plant stress inducers. Several features characterize the general stress response in plants: production of reactive oxygen species acting as stress-response signals, MAPKs signaling cascade inducing expression of defense genes, heat shock proteins preventing protein denaturation and degradation, and amino acids playing signaling roles and involved in osmoregulation. Tomato seedlings bathing in a cocktail of pharmaceuticals (Carbamazepine, Valporic acid, Phenytoin, Diazepam, Lamotrigine) or in Carbamazepine alone, at different concentrations and during different time-periods, were used to study the patterns of stress-related markers. The accumulation of the stress-related biomarkers in leaf and root tissues pointed to a cumulative stress response, mobilizing the cell protection machinery to avoid metabolic modifications and to restore homeostasis. The described approach is suitable for the investigation of stress response of different crop plants to various contaminants present in treated wastewater.
Grodek, T. ; Morin, E. ; Helman, D. ; Lensky, I. ; Dahan, O. ; Seely, M. ; Benito, G. ; Enzel, Y. Eco-hydrology and geomorphology of the largest floods along the hyperarid Kuiseb River, Namibia. Journal of Hydrology 2020, 582, 124450. Publisher's VersionAbstract
Flood-fed aquifers along the sandy lower reach of the Kuiseb River sustain a 130-km-long green belt of lush oases across the hyperarid Namib desert. This oasis is a year-round source for water creating dense-tall woodland along the narrow corridor of the ephemeral river valley, which, in turn, supports human activity and fauna including during the long dry austral winters and multi-year droughts. Occasional floods, originating at the river’s wetter headwaters, travel ∼280 km downstream, before recharging these aquifers. We analyzed the flood-aquifer-vegetation dynamics at-a-site and along the river, determining the relative impact of floods with diverse magnitude and frequency on downstream reaches. We find that flood discharge that feeds the alluvial aquifers also affects vegetation dynamics along the river. The downstream aquifers are fed only by the largest floods that allow the infrequent germination of plants; mean annual recharge volume is too low to support the aquifers level. These short-term vegetation cycles of green-up and then fast senescence in-between floods are easily detected by satellite-derived vegetation index. This index identifies historical floods and their magnitudes in arid and hyperarid regions; specifically, it determines occurrences of large floods in headwater-fed, ephemeral Namib streams as well as in other hyperarid regions. Our study reveals the importance of flood properties on the oasis life cycle, emphasizing the impact of drought and wet years on the Namib’s riparian vegetation.
Ogunmokun, F. A. ; Liu, Z. ; Wallach, R. The influence of surfactant-application method on the effectiveness of water-repellent soil remediation. Geoderma 2020, 362. Publisher's VersionAbstract
Soil water repellency (SWR) has a substantial effect on soil–water hydrology: it hinders infiltration, leading to enhanced surface runoff and soil erosion, and causes preferential flow in the soil profile beyond that from the soil's natural heterogeneity. SWR is associated with soil organic matter content, the latter added to the soil by vegetation exudates, litter and residues, forest fires, and replacement of fresh water by treated wastewater for irrigation. Surfactants are surface-active substances composed of organic molecules with hydrophobic tails and hydrophilic heads that can reduce the surface tension (γ) of the aqueous solution, thereby reducing SWR, via adsorption to soil particles. Surfactants are commonly used to remediate water-repellent soils. We investigated the role of two surfactant-application methods on the efficacy of SWR remediation. Aqueous solutions of two commercial surfactants had a substantial effect on parameters used to characterize the persistence and severity of SWR. However, the efficacy of these surfactants in remediating sandy soils rendered water-repellent by irrigation with treated effluent was substantially affected by their application method. Whereas application of aqueous surfactant solution to the surface of water-repellent soil, the commonly used remediation method, formed finger-like plumes similar to those obtained for water application, bulbous-like plumes were formed when the soil was premixed with the aqueous surfactant solution prior to water application. These differences were attributed to the significant role of the rate-limited surfactant adsorption to the soil particles. © 2019 Elsevier B.V.
2019
Ott, R. F. ; Gallen, S. F. ; Caves Rugenstein, J. K. ; Ivy-Ochs, S. ; Helman, D. ; Fassoulas, C. ; Vockenhuber, C. ; Christl, M. ; Willett, S. D. Chemical Versus Mechanical Denudation in Meta-Clastic and Carbonate Bedrock Catchments on Crete, Greece, and Mechanisms for Steep and High Carbonate Topography. Journal of Geophysical Research: Earth Surface 2019, 124. Publisher's VersionAbstract
Abstract On Crete—as is common elsewhere in the Mediterranean—carbonate massifs form high mountain ranges whereas topography is lower in areas with meta-clastic rocks. This observation suggests that differences in denudational processes between carbonate-rich rocks and quartzofeldspathic units impart a fundamental control on landscape evolution. Here we present new cosmogenic basin-average denudation rate measurements from both 10Be and 36Cl in meta-clastic and carbonate bedrock catchments, respectively, to assess relationships between denudation rates, processes, and topographic form. We compare total denudation rates to dissolution rates calculated from 49 new and previously published water samples. Basin-average denudation rates of meta-clastic and carbonate catchments are similar, with mean values of  0.10 mm/a and  0.13 mm/a, respectively. The contribution of dissolution to total denudation rate was <10% in the one measured meta-clastic catchment, and  40% for carbonate catchments ( 0.05 mm/a), suggesting the dominance of physical over chemical weathering at the catchment scale in both rock types. Water mass-balance calculations for three carbonate catchments suggests 40–90% of surface runoff is lost to groundwater. To explore the impact of dissolution and infiltration to groundwater on relief, we develop a numerical model for carbonate denudation. We find that dissolution modifies the river profile channel steepness, and infiltration changes the fluvial response time to external forcing. Furthermore, we show that infiltration of surface runoff to groundwater in karst regions is an efficient way to steepen topography and generate the dramatic relief in carbonates observed throughout Crete and the Mediterranean.
Brienza, M. ; Nir, S. ; Plantard, G. ; Goetz, V. ; Chiron, S. Combining micelle-clay sorption to solar photo-Fenton processes for domestic wastewater treatment. Environmental Science and Pollution Research 2019, 26, 18971-18978. Publisher's VersionAbstract
A tertiary treatment of effluent from a biological domestic wastewater treatment plant was tested by combining filtration and solar photocatalysis. Adsorption was carried out by a sequence of two column filters, the first one filled with granular activated carbon (GAC) and the second one with granulated nano-composite of micelle-montmorillonite mixed with sand (20:100, w/w). The applied solar advanced oxidation process was homogeneous photo-Fenton photocatalysis using peroxymonosulfate (PMS) as oxidant agent. This combination of simple, robust, and low-cost technologies aimed to ensure water disinfection and emerging contaminants (ECs, mainly pharmaceuticals) removal. The filtration step showed good performances in removing dissolved organic matter and practically removing all bacteria such as Escherichia coli and Enterococcus faecalis from the secondary treated water. Solar advanced oxidation processes were efficient in elimination of trace levels of ECs. The final effluent presented an improved sanitary level with acceptable chemical and biological characteristics for irrigation. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Olk, D. C. ; Bloom, P. R. ; Perdue, E. M. ; McKnight, D. M. ; Chen, Y. ; Farenhorst, A. ; Senesi, N. ; Chin, Y. - P. ; Schmitt-Kopplin, P. ; Hertkorn, N. ; et al. Environmental and agricultural relevance of humic fractions extracted by alkali from soils and natural waters. Journal of Environmental Quality 2019, 48, 217-232. Publisher's VersionAbstract
To study the structure and function of soil organic matter, soil scientists have performed alkali extractions for soil humic acid (HA) and fulvic acid (FA) fractions for more than 200 years. Over the last few decades aquatic scientists have used similar fractions of dissolved organic matter, extracted by resin adsorption followed by alkali desorption. Critics have claimed that alkali-extractable fractions are laboratory artifacts, hence unsuitable for studying natural organic matter structure and function in field conditions. In response, this review first addresses specific conceptual concerns about humic fractions. Then we discuss several case studies in which HA and FA were extracted from soils, waters, and organic materials to address meaningful problems across diverse research settings. Specifically, one case study demonstrated the importance of humic substances for understanding transport and bioavailability of persistent organic pollutants. An understanding of metal binding sites in FA and HA proved essential to accurately model metal ion behavior in soil and water. In landscape-based studies, pesticides were preferentially bound to HA, reducing their mobility. Compost maturity and acceptability of other organic waste for land application were well evaluated by properties of HA extracted from these materials. A young humic fraction helped understand N cycling in paddy rice (Oryza sativa L.) soils, leading to improved rice management. The HA and FA fractions accurately represent natural organic matter across multiple environments, source materials, and research objectives. Studying them can help resolve important scientific and practical issues. Copyright © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.