Chemical Variables Research Articles

Integration of ion-mobility high-resolution liquid chromatography/mass spectrometry-based untargeted metabolomics and desorption electrospray ionization-mass spectrometry imaging to unveil the ginsenosides variation induced by steaming for Panax ginseng, P. quinquefolius and P. notoginseng

The raw and steamed products of ginseng exhibit different efficacy, and elucidation of the underlying chemical transformation is significant for their rational application and quality control. This work was designed to holistically depict the chemical variation of Panax ginseng (PG), P. quinquefolius (PQ), and P. notoginseng (PN) induced by the steaming, and to unveil the steaming-associated markers diagnostic for differentiating between the raw and processed products, following a three-step strategy: 1) systematic ginsenosides characterization by hybrid scan (namely HDDIDDA) available on the Vion™ ion mobility-quadrupole time-of-flight mass spectrometer coupled with reversed-phase ultra-high performance liquid chromatography; 2) holistic depiction of the chemical variation and discovery of potential markers by the pattern recognition untargeted metabolomics analysis; and 3) construction of steaming-induced transformation network combined with desorption electrospray ionization-mass spectrometry imaging (DESI-MSI). Consequently, 542 ginsenosides were characterized from the raw and processed PG/PQ/PN. Steaming at 1–10 h could cause significant chemical variation, and separately 26, 28, and 18 potential markers were found for the steaming of PG, PQ, and PN. Steaming-induced transformation network mainly involved hydration of the malonyl group, hydrolysis of the glycosyl moiety, and dehydration at C-20. DESI-MSI further revealed spatial distribution of marker saponins in the cork layer, phloem, and xylem, and primarily confirmed the hydrolysis reactions occurring to ginseng steaming. Conclusively, the established strategy is practical to unveil the holistic ginsenosides variation of ginseng induced by the processing, which is useful in the quality control of both the herbal medicines and foods.

Chemical and boron isotopic compositions of tourmaline from the pegmatite in Ke'eryin rare metal orefield, Eastern Tibet: Implications for pegmatitic evolution

Pegmatites occur widely in the Ke'eryin rare metal orefield. The genesis and evolution of the Ke'eryin pegmatites are still in dispute, and morphological and geochemical studies on tourmalines from the Ke'eryin pegmatites are limited. In this study, in-situ analyses of major and trace elements and B isotope were conducted to uncover the origin of tourmaline and the evolution of related pegmatites. Three types of tourmaline from the Ke'eryin barren pegmatite were identified: elongated columnar or needle-columnar tourmaline (Tur-1 type), isolated, disseminated, irregular, and massive tourmaline (Tur-2 type), and long columnar tourmaline (Tur-3 type). Petrographically, the Tur-1 type crystallized at the early stage of pegmatitic crystallization sequence, the Tur-2 type possibly formed at the early- and/or syn-pegmatitic crystallization sequence, whereas the Tur-3 type likely formed at the relatively late crystallization sequence. Compositionally, most tourmalines belong to the alkali group with a few falling in the vacancy group. All the tourmalines show a schorl composition and are of magmatic origin. Chemical variations from the Tur-1 to Tur-3 tourmalines are controlled by magma fractionation and melt compositions rather than crystal chemical effects. Most tourmalines follow the (Na, Mg)(Xvac, Al)−1, (Mg, OH)(Al, O)−1, and (Ca, Mg2)(Xvac, Al2)−1 exchange vectors. The higher contents of Zn, Sn, Li, Be, Nb, and Ta and negative Eu anomalies in the Tur-3 type indicate that it was likely crystallized at a more evolved stage. In combination with textural evidence and tourmaline chemistry, we suggest that the Tur-1 and Tur-2 types were formed at the relatively earlier stage of pegmatite-forming magma and the Tur-3 type was likely formed closer to the end-stage of barren pegmatite crystallization. The B isotopic compositions are relatively homogeneous and display slightly higher in the Tur-3 type, which were likely caused by fractional crystallization during B-rich magma evolution. It can be inferred that the tourmaline in more evolved and/or Li-mineralized pegmatite with magma evolution should have higher Li, Be, Nb, Ta, and Sn contents, implying that tourmaline chemistry may be used as a potential exploration indicator for rare metal mineralization.

Carbon Dioxide Toxicity to Zebra Mussels (Dreissena polymorpha) is Dependent on Water Chemistry.

Carbon dioxide (CO2) is gaining interest as a tool to combat aquatic invasive species, including zebra mussels (Dreissena polymorpha). However, the effects of water chemistry on CO2 efficacy are not well described. We conducted five trials in which we exposed adult zebra mussels to a range of CO2 in water with adjusted total hardness and specific conductance. We compared dose-responses and found differences in lethal concentration to 50% of organisms (LC50) estimates ranging from 108.3 to 179.3 mg/L CO2 and lethal concentration to 90% of organisms (LC90) estimates ranging from 163.7 to 216.6 mg/L CO2. We modeled LC50 and LC90 estimates with measured water chemistry variables from the trials. We found sodium (Na+) concentration to have the strongest correlation to changes in the LC50 and specific conductance to have the strongest correlation to changes in the LC90. Our results identify water chemistry as an important factor in considering efficacious CO2 concentrations for zebra mussel control. Additional research into the physiological responses of zebra mussels exposed to CO2 may be warranted to further explain mode of action and reported selectivity. Further study could likely develop a robust and relevant model to refine CO2 applications for a wider range of water chemistries. Environ Toxicol Chem 2024;43:1312-1319. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Kelp-associated variability in seawater chemistry during a marine heatwave event connects to transgenerational effects in the purple urchin Strongylocentrotus purpuratus

Giant kelp Macrocystis pyrifera provides the foundation for immense biodiversity on the coast of California, USA. Kelp forests can change seawater retention time, altering water chemistry, including pH and dissolved oxygen (DO), as well as the magnitude and predictability of variability in the same properties. Environmental heterogeneity across space and time could drive organismal performance and processes such as transgenerational plasticity (TGP), where parental experience modifies the offspring phenotype, potentially conferring tolerance to future environmental stress. We monitored environmental variability by deploying temperature, pH, and DO sensors inside and outside a temperate kelp forest in the Santa Barbara Channel (SBC) throughout the gametogenesis period of a key herbivore, the purple urchin Strongylocentrotus purpuratus. Over the 6 mo period, pH and temperature were slightly elevated inside the kelp forest, accompanied by more predictable, low-frequency variability relative to outside. Adult S. purpuratus were conditioned inside and outside the kelp spanning gametogenesis. The urchins were spawned and their larvae were raised under high (1053 µatm) and low pCO2 (435 µatm) at 15°C in the laboratory to assess their physiological response to the maternal and developmental environments. Larvae raised under high pCO2 were more susceptible to acute thermal stress; however, within each larval treatment, progeny from outside-conditioned mothers had a 0.4°C higher lethal temperature (LT50). Our results indicate that heterogeneity in abiotic factors associated with kelp can have transgenerational effects in the field, and interactions between factors, including temperature and pH, will impact purple urchins as local variability associated with marine heatwaves and upwelling evolves with climate change.

Deposition of silica in sorghum root endodermis modifies the chemistry of associated lignin.

Silica aggregates at the endodermis of sorghum roots. Aggregation follows a spotted pattern of locally deposited lignin at the inner tangential cell walls. Autofluorescence microscopy suggests that non-silicified (-Si) lignin spots are composed of two distinct concentric regions of varied composition. To highlight variations in lignin chemistry, we used Raman microspectroscopy to map the endodermal cell wall and silica aggregation sites in sorghum roots grown hydroponically with or without Si amendment. In +Si samples, the aggregate center was characterized by typical lignin monomer bands surrounded by lignin with a low level of polymerization. Farther from the spot, polysaccharide concentration increased and soluble silicic acid was detected in addition to silica bands. In -Si samples, the main band at the spot center was assigned to lignin radicals and highly polymerized lignin. Both +Si and -Si loci were enriched by aromatic carbonyls. We propose that at silica aggregation sites, carbonyl rich lignin monomers are locally exported to the apoplast. These monomers are radicalized and polymerized into short lignin polymers. In the presence of silicic acid, bonds typically involved in lignin extension, bind to silanols and nucleate silica aggregates near the monomer extrusion loci. This process inhibits further polymerization of lignin. In -Si samples, the monomers diffuse farther in the wall and crosslink with cell wall polymers, forming a ring of dense lignified cell wall around their export sites.

Phytochemical analysis, post-harvest shade drying, and biological activities of Melaleuca linariifolia Sm. from foothills of Kumaun Himalayas, India

Melaleuca linariifolia Sm. (Genus: Melaleuca; Family: Myrtaceae) cultivated for its ornamental usages in the Kumaun Himalayan region of Uttarakhand is commercially known as flax-leaved paper bark tree. The present study analyzes the chemical variation of the essential oils obtained from aerial parts and flowers of M. linariifolia. The effect of post-harvest shade drying on the essential oil composition was also assessed in the study. Total of 16 compounds accounting for 94.2 % and 94.6 % were identified in the aerial parts and flowers essential oil, respectively. 1,8-Cineole (71.8 %–73.8 %) was identified as the predominant compound in both the studied essential oils followed by limonene (1.7 %–9.3 %) and α-terpineol (4.2 %–6.7 %). Moreover, the fresh aerial parts had 73.8% of 1,8-cineole content which increased up to 79.2% post-harvest drying. The study revealed oxygenated monoterpenes as the major class constituents with 1,8-cineole as the marker component ranging from 67.7 % to 79.2 % during the post drying analysis. While assessing the biological activities, the antioxidant activity of the oils was investigated in vitro using three assays: DPPH radical scavenging activity, Iron(II) complexing activity, and H2O2 radical scavenging activity. The oil also inhibited the activity of α-amylase with IC50 of 3.26 ± 0.04 μg/ml and protein denaturation with IC50 of 3.0 ± 0.03 g/ml. This is the first-time report of essential oil analysis of M. linariifolia flowers and post-harvest drying study from bhabar region of the Kumaun Himalayas. The high essential oil yield, rich chemical composition and biological activities suggest the cultivation of Melaleuca species as an industrial crop.

Genotypic identification and catechin profiling of Uncaria gambir in West Sumatra, Indonesia

Abstract. Wardi ES, Syukur S, Chaidir Z, Jamsari J. 2024. Genotypic identification and catechin profiling of Uncaria gambir in West Sumatra, Indonesia. Biodiversitas 25: 1151-1158. The primary objective of this study is to assess genetic and chemical variability among four genotypes of Uncaria gambir cultivated in West Sumatra. Uncaria gambir is native to Indonesia, widely cultivated in West Sumatra, used as an herbal remedy, and become a significant agricultural product for Indonesian export with catechin content as a standard. The phytochemical components of this species have been extensively studied, and its extracts are employed in traditional medicine. To fingerprint genomic DNA, we employed three pairs of Specific Sequence-Related Amplified Polymorphism (SRAP) markers selected from 29 combinations tested. A total of 150 amplified bands were generated, highlighting substantial genetic variability among the tested genotypes. Notably, the highest amplified and polymorphic band was obtained with primer E combination from three selected primers (primer E, primer F, and primer T). In addition, only catechins were identified among the four types of catechins employed as HPLC standards. We detected varying catechin concentrations among the genotypes, with genotype Mancik exhibiting the highest concentration. This finding underscores the potential for genotype-specific bioactive marker identification within U. gambir. In addition, this study shows the efficiency of SRAP markers in genotype identification within U. gambir. Furthermore, the identification of catechin as a prominent bioactive marker emphasizes its significance for further exploration and conservation efforts.

Tourmaline growth in the border and wall zones of the Emmons pegmatite (Maine, U.S.A.): Evidence for disequilibrium crystallization and boundary layer formation

Abstract The anisotropic textures, including unidirectional solidification textures and graphic intergrowths, characteristic for pegmatites, are interpreted to result from disequilibrium crystallization at high degrees of undercooling. Experimental studies have revealed the existence of thin boundary layers surrounding the rapidly growing crystals. Here, tourmaline-bearing samples from the outer zones of the Emmons pegmatite (Maine, U.S.A.) are used to examine if a boundary layer can also occur in natural samples. Crystal morphology is linked with geochemistry to understand the evolution of pegmatite melts and to constrain disequilibrium conditions at large degrees of undercooling. Petrographic studies and semiquantitative micro-X-ray fluorescence element mapping were conducted to identify crystal morphology and zonation, complemented with electron microprobe analyses to determine major and minor element compositions and LA-ICP-MS analyses of selected trace elements. Three textural groups were identified: comb-like tourmaline, quartz-tourmaline intergrowths, and radiating tourmaline. The intergrowths are optically coherent and are split into three different morphologies: central, second tier, and skeletal tourmaline. Most tourmaline is schorl, but chemical variation occurs on three different scales: between textural groups, between different morphologies, and intracrystalline. The largest scale geochemical variation is caused by the progressive evolution of the melt as it crystallized from the borders inwards, while the intracrystalline variations are attributed to sector zoning. A model is suggested where the systematic variation of Mg, Mn, and Fe within individual intergrowths is proposed to be the result of crystallization from a boundary layer, rich in water and other fluxing elements (e.g., Li, P, B), formed around the rapidly growing central tourmaline. Here, we show the first examples of boundary layers in natural pegmatites. Furthermore, the results bring into question whether boundary layer tourmaline can be used as a bulk melt indicator in pegmatitic melts.

Uncovering the metabolite complexity and variability of cultivated hemp (Cannabis sativa L.): A first phytochemical diversity mapping in Greece

The high value of fiber-type Cannabis sativa L. (hemp) due to its phytochemicals has yet to be fully recognized and leveraged. Besides cannabidiol (CBD), which is the most prevalent non-psychoactive cannabinoid, hemp contains numerous other cannabinoids with unexplored bioactivities, in addition to various compound classes. Previous works have aimed to correlate chemical profiles of C. sativa inflorescences with important parameters, mostly based on experiments under controlled conditions. However, mapping studies that explore the phytochemical diversity of hemp in a more realistic context are crucial to guide decisions at multiple levels, especially in areas where hemp cultivation was recently re-authorized, including Mediterranean countries. In this work, a powerful strategy was followed to map the phytochemical diversity of cultivated hemp in Greece, being the first study of its kind for this environment. A panel of 98 inflorescence samples, covering two harvesting years, eleven geographical regions and seven commonly used EU varieties, were studied using a combination of targeted and untargeted approaches. Quantitative results based on UPLC-PDA revealed relatively constant CBD/THC (total) ratios, while profiling by LC-HRMS effectively probed the phytochemical variability of samples, and led to the annotation of 88 metabolites, including a multitude of minor cannabinoids. Multivariate analysis substantiated a strong effect of harvesting year in sample discrimination and related biomarkers were revealed, belonging to fatty acids and flavonoids. The effect of geographical region and, especially, variety on chemical variation patterns was more intricate to interpret. The results of this work are envisioned to enhance our understanding of the real-world phytochemical complexity of C. sativa (hemp), with a view to maximized utilization of hemp for the promotion of human well-being.

Mineral chemistry and alteration patterns of Cr-spinel in serpentinized peridotites from NW Iran

The Late Cretaceous ophiolite mélange in the Salmas area of NW Iran is a part of the Neotethys ophiolites. The mélange includes serpentinized harzburgite, serpentinites, mafic rocks, radiolarite, layered red pelagic limestones and grey and white marbles. Harzburgite main primary mineral phases are olivine, orthopyroxene, clinopyroxene and Cr-spinel. Cr-spinel has Cr2O3 contents of 21.13 to 30.18 wt% and high Al2O3 (38.67–48.52 wt%), FeO (15.18–18.13 wt%) and MgO (15.18–17.51 wt%) contents. The 100 × Cr/(Cr + Al) ratios of 23 to 34 indicate 9 to 13 % partial melting in the Mid Ocean Ridge (MOR) environment for the origin of the peridotites. An alteration zone is developed around the altered Cr-spinel. Fine-grained minerals assemblage at the spinel crystals’ margin includes Cr-rich chlorite, Cr-rich garnet and spinel-silicate mixture. A 2–5 μm wide transitional zone is developed between the chromite-silicate assemblage and the Cr-rich garnet zone. The chemical variations of major oxides across the alteration zone are mainly diffusion controlled. Al, Cr and Mg have diffused out from the primary spinel and Fe and Mn have diffused into the spinel. Cr-spinel is altered in two stages due to serpentinization. During the first stage and following hydration, spinel reacted with olivine and orthopyroxene to form Cr-rich chlorite and ferrian chromite. Silica formed at this stage. At the second stage, the reaction between the chromite-silicate assemblage and Cr-rich chlorite plus silica form the first stage and Ca2+ in the fluid (released from clinopyroxene alteration) produced Cr-rich garnet and H2O-rich fluid, at temperature between 400 and 600 °C.

Water and sediment chemistry drivers of chlorophyll-a dynamics within a Ramsar declared floodplain pan wetland system.

Floodplain pans are hydrologically dynamic in nature and characterised by variables such as chlorophyll-a (chl-a), water, and sediment chemistry over their hydroperiods. The present study investigated the spatio-temporal variations in water and sediment physico-chemical, and chlorophyll-a concentration characteristics of six floodplain pans found in the Ramsar declared Makuleke wetlands, Kruger National Park, South Africa. The water and sediment physico-chemical variable values were generally elevated during the high-water period, whereas chlorophyll-a concentrations varied across pans and hydroperiod. Benthic chl-a concentration significantly varied across pans with concentrations ranging from 161 to 1036.2mg m2. The two-way ANOVA showed significant differences in benthic chl-a concentration among hydroperiods, and no significant differences were observed in pelagic chl-a across pans and hydroperiods. Generally, pelagic and benthic chl-a concentration increased as water and sediment chemistry variables increased. Furthermore, three sediment variables, i.e. pH, calcium, and magnesium, and water conductivity were found to be significant in structuring benthic chlorophyll-a dynamics in pans. However, none of the sediment and water variables had a significant effect on pelagic chl-a. Hydroperiod had a significant effect on influencing chl-a concentration, with high and low water level periods being characterised by low and high chl-a concentration, respectively. The n-MDS results showed strong overlaps in chl-a biomass among the Makuleke floodplain pans across hydroperiods. The increasing chl-a concentration in these floodplain pans due to potential bioturbation effects as a result of large mammals could potentially lead to eutrophication, which in turn could affect the system's primary productivity and aquatic biota. Therefore, it is important to establish a continuous monitoring programme on these pans to inform sound management decisions.

The Importance of Variety and Regional Identity on the Dextrin-Reducing Enzymatic Activity of Cascade and Mosaic® Hops Grown in Washington and Oregon

This study analyzed hops from 35 fields located in two states (Washington and Oregon) repeatedly over 2 harvest years (2020 and 2021) to determine the impact that hop variety and regional identity, or “terroir,” might have on hops’ dextrin reducing enzymatic potential. Cascade and Mosaic® hops were harvested, kilned, pelletized, and analyzed for dextrin-reducing enzymatic activity using a bench-top dry-hopping assay in a high-dextrin beer. In addition, data for 25 soil, 14 management, 13 climate, and 27 chemistry variables were collected and compared to the enzyme activity results from the bench-top dry-hopping assay. There existed a highly significant difference in enzymatic activity based on hop variety (two sample t-test p-value = 1.18 × 10−14) with Cascade hops being approximately 60% higher on average than Mosaic® hops regardless of growing region or harvest year. The soil and farm management variables also showed statistically significant interactions with enzymatic activity (p-values of 7.82 × 10−9 for Cascade and < 2 × 10−16 for Mosaic®), though there was little clarity with respect to the specific “terroir” variables that might relate to hop creep. Further research is needed to better understand causal interactions between farm, soil, climate, and management practices and dry-hop-induced dextrin-reducing enzymatic activity.

Chemical variability and insect repellent effects of lemon catnip essential oil and related phytochemicals against Cimex lectularius L

Plants are sources of natural products that reflect the ecological interactions that shaped their secondary metabolism. Among those, phytochemicals with insect repellent activity have shown potential to be part of integrated pest management programs. In this study, we performed an initial screening of the repellent activities of five commercially available essential oils, as well as the essential oil of lemon catnip (Nepeta cataria var. citriodora Dumoulin ex Lej.) and related natural products against the common bed bug (Cimex lectularius L.). Additionally, we studied the effects of two different growing locations (Upper Deerfield and Pittstown, state of New Jersey, United States) on the chemical composition of three lemon catnip lines (commercial lemon catnips Richters and Jelitto, and lemon-scented catnip line CN5). The chemical composition of the essential oils was determined by gas chromatography-mass spectrometry (GC-MS) and the repellent activity was assessed by the petri dish method. Cinnamon bark, clove buds, citronella and geranium essential oils were as effective as N,N-diethyl-meta-toluamide (DEET), the gold standard of insect repellents, against bed bugs after one hour of exposure in vitro. The essential oil of lemon catnip and its major compounds citronellol and geraniol were also as repellent as DEET using the same test. Citral shows promising short-term repellency but is inferior to geraniol and citronellol for extended duration of repellency. As for the chemical variability of lemon catnip lines in different growing locations, CN5 line was not significantly affected by the different locations, while both commercial lines Richters and Jelitto had significantly higher proportions of geraniol when grown in Upper Deerfield. Richters lemon catnip produced more nepetalactone in its essential oil when cultivated in Pittstown. This study is the first report of the activity of lemon catnip essential oil as an insect repellent and emphasized the importance of ecological conditions for the production of natural products for pest control applications.

Variation in the Floral Scent Chemistry of Nymphaea 'Eldorado', a Valuable Water Lily, with Different Flowering Stages and Flower Parts.

Nymphaea 'Eldorado', a valuable water lily, is a well-known fragrant plant in China. Studying the temporal and spatial characteristics of the floral components of this plant can provide a reference for the further development and utilization of water lily germplasm resources. In this study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to explore the types and relative contents of floral components at different flowering stages (S1: bud stage; S2: initial-flowering stage; S3: full-flowering stage; S4: end-flowering stage) and in different floral organs of N. 'Elidorado', combined with the observation of the microscopic structure of petals. A total of 60 volatile organic compounds (VOCs) were detected at different flowering stages, and there were significant differences in floral VOCs at different flowering stages and in different flower organs. The volatile compounds of N. 'Eldorado' can be divided into seven chemical classes,, namely, alkenes, alcohols, esters, aldehydes, ketones, alkanes, and others; the most common were alkenes and alkanes. A total of 39, 44, 47, and 42 volatile compounds were detected at S1, S2, S3, and S4. The VOCs present in high concentrations include benzaldehyde, benzyl alcohol, benzyl acetate, trans-α-bergamotene, α-curcumene, cis-α-farnesene, and so on. The types and total contents of volatiles at the full-flowering stage were higher than at other flowering stages. Comparing the VOCs in different parts of flower organs, it was found that the contents of alcohols, esters, and aldehydes were greatest in the petals, the alkenes in stamens were abundant with a relative content of up to 54.93%, and alkanes in the pistil were higher than in other parts. The types and total contents of volatiles in the stamens of N. 'Eldorado' were higher than those in other flower organs; they were the main part releasing fragrance. The observation of petal microstructure revealed that the size and quantity of the papillae on the epidermises of petals, the number of intracellular plastids, and the aggregates of floral components (osmophilic matrix granules) were significantly higher at the full-flowering stage than at the other flowering stages. This study suggested the main flowering stage and location at which the floral VOCs are released by N. 'Eldorado' and provided a reference for guiding the breeding of this water lily, exploring genetic patterns and developing related products.

Assessing the Influence of Agricultural Nonpoint Source Pollution on Water Quality in Central Kentucky’s Headwater Streams

This study addresses the pressing issue of nonpoint source water pollution in Kentucky, particularly associated with large-scale agriculture. Centered on the outer bluegrass region of Central Kentucky, the research examines the water quality of headwater streams during the agricultural season. The approach involves geospatial land cover classification using aerial imagery. Water quality data were collected during the agricultural growing season from May to October 2018. Land cover classification utilized ERDAS Imagine 2016 and ESRI ArcGIS 10.6 GIS software, while conventional water quality parameters were measured with a YSI ProDSS® multiparameter water probe and a Marsh-McBirney Flo-Mate 2000 flow meter. Statistical analyses show significant differences in stream water chemistry, suggesting the impact of agricultural nonpoint source pollution. Forested streams exhibited more varied conditions, indicating a potentially better environment. As agricultural land percentage increased, water chemistry variation suggested a measurable threshold for changes. Significant differences in water quality between agricultural and forested streams highlight the potential benefits of expanding riparian zones beyond regulations. Enlarging these zones is proposed as a strategy to mitigate nonpoint source pollution in Kentucky’s waterways.

Impact of iron-modified biochars on soil nitrous oxide emissions: Variations with iron salts and soil fertility

Nitrous oxide (N2O) emissions from soils are a significant environmental concern due to their contribution to greenhouse gas emissions. Biochar has been considered as a promising soil amendment for its potential to influence soil processes. Iron modification of biochar has been extensively discussed for its ability to enhance adsorption of pollutants, yet its impact on mitigating soil N2O emissions remains poorly understood. In the present study, corn straw (CB) and wood (WB) biochars were treated with FeSO4/FeCl3 (SCB and SWB) and Fe(NO3)3 (NCB and NWB). The effects of these biochars on soil N2O emissions were investigated using soils with varying fertility levels over a 35-day incubation period at 20 °C. Results revealed significant variations in biochar surface chemistry depending on biochar feedstock and iron salts. Compared to pristine biochars, NWB and NCB exhibited higher pH, total N content, and dissolved NO3–N concentrations (246 ± 17 and 298 ± 35 mg kg−1, respectively), but lower bulk and surface C content. In contrast, SWB and SCB demonstrated acidic pH and elevated dissolved NH4–N concentrations (5.38 ± 0.43 and 4.19 ± 0.22 mg kg−1, respectively). In forest soils, NWB and NCB increased cumulative N2O emission by 28.5% and 67.0%, respectively, likely due to the introduction of mineral nitrogen evidenced by significant positive correlation with NO3–N or NH4–N. Conversely, SWB and SCB reduced emissions in the same soil by 28.5% and 6.9%, respectively. In agricultural soil, most biochars, except SWB, enhanced N2O emissions, possibly through the release of labile organic carbon facilitating denitrification. These findings underscore the significance of changes in biochar surface chemistry and the associated potential risk in triggering soil N2O emissions. This study highlights the need for a balanced design of biochar that considers both engineering benefits and climate change mitigation.

Evolution and determinants of precipitation chemistry in a plateau city, China: Insight from the pollutants source identification and environmental effect

Rainfall-related chemical ions deposition processes have important environment effects on earth-surface, which is also a vital sink of urban air pollutants. Therefore, identifying the rainwater chemical evolution and determinants, and source is essential. The daily-based rainwater samples during 2022– 2023 and the historical rainwater data in a typical plateau city (Kunming) were investigated. The Ca2+ and NH4+, SO42− and NO3− dominated the rainwater cations and anions, with the cationic and anionic percentages of 78% and 10%, 50% and 33%. The historical variations in ions percentages revealed the achievement of environmental protection. The precipitation amount and the seasonal changes of source emission were critical determinants for the variations of rainwater chemistry. Using the stoichiometry and receptor model, the contributions of potential origins to rainwater chemicals were assessed. 86% of NO3− and 40% SO42− were from combustion-related anthropogenic source, volatilization-related source contributed 85% of NH4+ (e.g., agricultural/municipal wastes emissions), whereas marine input was the main contributor of Cl− (59%) and Na+ (52%). Mg2+ (58%) and Ca2+ (41%) were primary from terrestrial input source. The risk of wet deposition-caused acidification was limited due to the high rainwater neutralization level, whereas the impact of nitrogen-related deposition on gross primary productivity (GPP) was non-negligible and further attention was need. Overall, the present study clarified the rainfall chemical features of plateau city region and further provided decision support for more effective urban air environmental management programs.

The evolutionary genomics of adaptation to stress in wild rhizobium bacteria

Microbiota comprise the bulk of life's diversity, yet we know little about how populations of microbes accumulate adaptive diversity across natural landscapes. Adaptation to stressful soil conditions in plants provides seminal examples of adaptation in response to natural selection via allelic substitution. For microbes symbiotic with plants however, horizontal gene transfer allows for adaptation via gene gain and loss, which could generate fundamentally different evolutionary dynamics. We use comparative genomics and genetics to elucidate the evolutionary mechanisms of adaptation to physiologically stressful serpentine soils in rhizobial bacteria in western North American grasslands. In vitro experiments demonstrate that the presence of a locus of major effect, the nre operon, is necessary and sufficient to confer adaptation to nickel, a heavy metal enriched to toxic levels in serpentine soil, and a major axis of environmental soil chemistry variation. We find discordance between inferred evolutionary histories of the core genome and nreAXY genes, which often reside in putative genomic islands. This suggests that the evolutionary history of this adaptive variant is marked by frequent losses, and/or gains via horizontal acquisition across divergent rhizobium clades. However, different nre alleles confer distinct levels of nickel resistance, suggesting allelic substitution could also play a role in rhizobium adaptation to serpentine soil. These results illustrate that the interplay between evolution via gene gain and loss and evolution via allelic substitution may underlie adaptation in wild soil microbiota. Both processes are important to consider for understanding adaptive diversity in microbes and improving stress-adapted microbial inocula for human use.

Dominant herbaceous plants contribute to the spatial heterogeneity of beech and riparian forest soils by influencing fungal and bacterial diversity

Understanding of factors that shape diversity patterns in forest ecosystems is a main challenge in forest ecology and management practices. Although herbaceous plants are known to contribute to the maintenance of the structure and function of temperate forests, their impact on fungal and bacterial communities in soils is largely unknown. Therefore, we conducted a comparative study of soil fungal and bacterial diversity in two Central European deciduous forests, focusing on plots with dominant herbaceous species of contrasting morphology, phenology, reproduction, and ecology, including Allium ursinum and Dentaria enneaphyllos in a beech forest, as well as Aegopodium podagraria and Ficaria verna in a riparian forest. Plots with a mixture of herbaceous species and without plant cover were also studied. In both forests, fungal communities showed the strongest association with spatial location, part of which was explained by between-site variability in soil chemistry and was also influenced by herbaceous vegetation. The community composition of saprotrophic fungi depended on the presence and type of herbaceous vegetation in both forests. In addition, herbaceous plants affected the composition of arbuscular mycorrhizal fungi community in the beech forest, while in the riparian forest they affected endophytes and plant pathogens. For bacteria, soil chemistry played the most important role. Our results showed that dominant herbaceous vegetation is one of the drivers shaping microbial community composition, contributing to spatial heterogeneity of forest sites. Given that herbaceous species, especially those forming monospecific patches, affect the soil biotic properties in temperate forests, they should be included in forest management practices.

Using Principal Component Analysis to Assess Soil Chemical Properties in the Mwea Irrigation Scheme, Kenya: Implications for Rice Agronomic Management

Sub-Saharan Africa faces significant challenges as a net importer of rice, with self-sufficiency rates plummeting to as low as 14% in countries like Kenya. The Mwea irrigation scheme shoulders the bulk of rice cultivation, contributing over 80% of the country’s production. However, productivity within the scheme has seen a concerning decline, dropping from 5.6 ─ 6.0 t ha-1 to 1.3 ─ 4.6 t ha-1 between 1977 and 2018. This decline could be attributed to site-specific nutritional deficiencies and/or toxicities, rendering generalized agronomic recommendations ineffective in certain areas. To address this problem, our study aimed to assess soil chemical properties variability within the Mwea irrigation scheme, identify clusters with similar nutritional status, and tailor area-specific agronomic recommendations. During May to September 2020, we collected and analyzed four hundred samples from five sections of the scheme for total organic carbon, soil pH, macro and micronutrients, and exchangeable cations. Principal component analysis was conducted on the mean values of the soil chemical properties to identify significant contributors to variation and establish zones with similar patterns. Principal components 1 to 4 collectively explained 72.2% of the total variability. Cluster analysis revealed four distinct clusters, namely MW, TB, KT, and MU. Within cluster MW, soil pH was below the optimum range for rice cultivation, suggesting a need for liming. Potassium deficiency was observed across all clusters, with rice straw incorporation recommended as a long-term solution. Furthermore, zinc deficiency was noted in cluster WU, necessitating zinc fertilizer application. Conversely, iron toxicity was a concern in cluster MW, suggesting the adoption of alternating wetting and drying techniques and cultivating tolerant varieties. By proving tailored recommendations based on localized soil conditions, we aim to bolster rice productivity within the Mwea irrigation scheme and contribute to regional food security efforts.