Increase In Total Organic Carbon Research Articles

Nano-iron and AM fungi inoculation in dryland wheat field: A sustainable alternative to plastic film mulching

ContextPlastic film mulching is a primary cultivation measure in the dryland agricultural areas of northwest China, but comes with the drawback of plastic pollution. To overcome this issue, the biological inoculants such as arbuscular mycorrhizal (AM) with nanotechnology might be a critical pathway, but their positive effects on plants are context-dependent and vary with species, application method, concentration, size, surface charge, and other physio-chemical properties. There is so far limited information available on the combined effects of AM fungi with nanoparticles in agriculture. ObjectivesThis study aimed to investigate the potential of iron nanoparticles (FeNPs) in combination with AMF regarding wheat productivity maintenance and its driving mechanism. MethodsHerein, we used a completely randomized block design for the field experiments in the years 2018 and 2019. We conducted two field experiments using nanopriming of seeds with iron nanoparticles (FeNPs) and AMF in two growing seasons in 2018 and 2019 on wheat (Triticum aestivum L., cv. Longchun29) in the field. Each plot had a 5 m × 5 m total area having 6 rows of 0.2 m spacing and 0.5 m buffer strip among the neighboring plots. There were 8 treatments in the field experiment, and each treatment was repeated 3 times, including four nano iron concentration seed soaking treatments (0 mg L-1, 5 mg L-1, 10 mg L-1, 15 mg L-1) and two inoculation treatments of arbuscular mycorrhizal fungi (inoculated with Gi and non-inoculated). ResultsCombined treatments with arbuscular mycorrhizal fungi and iron nanoparticles led to significant increases in wheat biomass and yield across 2018 and 2019. When compared with control treatment there was an increase of 111% in biomass for the year 2018 and a 102% increase was observed for the year 2019; while the increase in the yield percent when compared to control was 91% in 2018 and 85% in 2019 respectively. Water use efficiency for yield (WUE) increased by 92% in 2018 and 57% in 2019. The colonization rate of AMF + FeNPs 10 mg L-1 treatment increased by 223%, 88%, and 211%, respectively compared with control at the jointing, anthesis, and maturity stage in 2018; and increased by 48%, 37%, and 56% respectively in the year 2019. FeNPs at 10 mg L-1 led to small increases in total organic carbon (TOC), total nitrogen (TN), microbial biomass carbon and nitrogen (MBC), and (MBN), in both growing seasons, and AMF inoculation further significantly increased these carbon fractions by 2.6%, 20%, 21% and 26% in 2018; while 1.3%, 14.8%, 12.5%, and 35% in 2019 respectively. ConclusionThe combined treatments of FeNPs and AMF at an optimal concentration (10 mg L-1) significantly increased net economic income by 229% in 2018 and 138% in 2019 when compared to the control. In this study, wheat aboveground biomass and yield and other related parameters have been improved under field trials, which verified that AMF inoculation alongside FeNPs, can play a beneficial role in promoting dryland spring wheat. ImplicationsTaken together, the co-inoculation with FeNPs and AMF displayed a promising perspective in green production with the potential replacement of plastic film mulching in semiarid dryland regions.

Fine-grained deep-water turbidite gas reservoirs in upper Bengal Fan

The Bengal Fan is a mud-rich, deep-water sediment system. A series of recently discovered biogenic gas reservoirs in the northeastern Bay of Bengal are fine-grained. The Pliocene gas discovered in the study area accumulated in the levee element of a deep-water channel complex identified by high-resolution three-dimensional (3D) seismic interpretation integrated with well logs and sidewall cores (SWC). The thickness and porosity of the levee gas reservoir are of good quality, but the permeability is relatively low owing to the high mud content. The discovery of the levee sandstone indicates various reservoirs in this mud-rich sediment system. Moreover, gas discovery implies that the gravity-flow sediment systems “link” the source rock in the study area. Gas reservoirs were discovered in Pliocene gravity-flow sediment systems, where the palaeo-climate experienced significant changes with a dramatic increase in total organic carbon (TOC) from the Miocene to the Pliocene. TOC-rich pelagic mudstones and deep-water gravity sediments act as source rocks for petroleum systems. Therefore, gravity-flow sediment systems have developed self-accumulating petroleum plays that exhibit enormous potential for exploration. Given the structural framework in the northeastern part of the Bay of Bengal, stratigraphic or structure-stratigraphic traps could have developed in the Pliocene deep-water sediment systems in the Bengal Fan.

Coastal streams and sewage outfalls: Hot spots of mercury discharge, pollution and cycling in nearshore environments

The coastal streams (CSs) and sewage outfalls (SOs) are widely distributed and direct anthropogenic stress on global coastal ecosystems. However, the CS/SO-associated mercury (Hg) discharge, pollution and cycle in nearshore environment are less quantified. Here, we report that total Hg (THg) and methylmercury (MMHg) concentrations in waters of CSs (n = 8) and SOs (n = 15) of the northern China were ∼102 to 103 times of coastal surface waters and 10 to 102 times of major rivers in China and other regions. The CS/SO discharges resulted in the increase of total organic carbon (TOC) contents, THg and MMHg concentrations and TOC-normalized THg and MMHg concentrations in sediments of CS/SO-impacted coasts. The laboratory experiments further illustrated that the CS/SO-impacted sediments characterized with high potentials of dissolved THg and MMHg productions and releases. Our findings indicate that the layout optimization of SOs is able to reduce the Hg risk in coastal environment.

Impacts of poly(lactic acid) microplastics on organic compound leaching and heavy metal distribution during hydrothermal treatment of sludge

This study provides an in-depth examination of the role of poly(lactic acid) microplastics (PLA-MPs) during sludge treatment, particularly in relation to organic compound leaching and heavy metal distribution. Through the application of advanced analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermal analysis, and gas chromatography–mass spectrometry (GC–MS), the release of degradation byproducts was quantified, and the effects on organic compound leaching and heavy metal distribution were assessed. Specifically, the results demonstrated that PLA-MPs significantly impacted the hydrolysis reaction, with the pH value descending in pure water as the hydrothermal temperature escalated. At 140 °C, the hydrolysate contained 20.66 % propylene ester and 16.57 % lactic acid. Furthermore, an increase in total organic carbon (TOC) was observed with increasing temperature, with TOC content at 140 °C in water almost doubling from that at 120 °C and 130 °C. With respect to heavy metals, the presence of PLA-MPs influenced the migration of Cr(VI) between solid and liquid phases in sludge. Notably, after 180 °C hydrothermal treatment, the content of Cr(VI) in the liquid phase of sludge with PLA-MPs was 9.72 %, which is higher than that of sludge without PLA-MPs at 5.80 %. These findings underline the need to consider PLA-MPs' influence on organic compound leaching and heavy metal distribution during sludge treatment.

Fertilization Enhances Grain Inorganic Arsenic Assimilation in Rice

To investigate how soil fertilization/amendments alters arsenic speciation grain off-take in paddy rice, rice was grown to maturity in growth chambers fertilized with standard mineral fertilizer, wood ash (rich in silica), pig slurry (rich in organic matter), and non-amended control. The soil was sourced from a Chinese paddy field. The primary fertilized elements (nitrogen, phosphorus, potassium) were kept constant across treatments. Porewater chemistry and soil microbiology were monitored throughout the experiments. Total grain arsenic, sum of inorganic arsenic and dimethylarsinic acid (DMA), was significantly different between treatments (P = 0.024), with inorganic arsenic varying from 0.025 to 0.08 mg/kg and DMA from 0.08 to 0.16 mg/kg for control compared to fertilized, respectively. Fertilizer source made no difference to arsenic speciation concentration in grain. Porewater analysis found that as anaerobism set in, inorganic arsenic, phosphorus and manganese greatly lowered in concentration. Methylated arsenic species concentrations increased over time, concurrent with an increase in pH, decrease in Eh, and increase in total organic carbon and iron, with no strong treatment effects, except for pig slurry that enhanced pH and decreased Eh. Methanogenic archaea, sulfate-reducing bacteria and Acidobacteria increased with time and some Actinobacteria and Firmicutes increased due to slurry, but then decreased with time (P < 0.01). Methanogenic archaea and sulphate-reducing bacteria correlated positively with porewater DMA and negatively with porewater inorganic arsenic (P < 0.05). Genera within the Actinobacteria and Burkholderiaceae correlated negatively with DMA, while genera with iron-reducing capacity (Clostridiales) correlated positively with porewater inorganic arsenic and DMA (P < 0.05).

Biomethane production and microbial strategies corresponding to high organic loading treatment for molasses wastewater in an upflow anaerobic filter reactor.

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. In this study, an upflow anaerobic filter (UAF) reactor was employed to establish a high organic loading treatment system for molasses wastewater and further investigated the microbial community dynamics in response to this stressful operation. The biogas production increased with an increase in total organic carbon (TOC) loading rate from 1.0 to 14g/L/day, and then it decreased with further TOC loading rate addition until 16g/L/day. The UAF reactor achieved a maximum biogas production of 6800mL/L/day with a TOC removal efficiency of 66.5% at a TOC loading rate of 14g/L/day. Further microbial analyses revealed that both the bacterial and archaeal communities developed multiple strategies to maintain stable operation of the reactor at high organic loading (e.g., Proteiniphilum and Defluviitoga maintained high abundances throughout the operation; Tissierella temporarily dominated the bacterial community at TOC loading rates of 8.0 to 14g/L/day; and multi-trophic Methanosarcina shifted as the dominant methanogen at the TOC loading rates of 8.0 to 16g/L/day). This study presents insights into a high organic loading molasses wastewater treatment system and the microbial flexibility in methane fermentation in response to process disturbances.

Effects of Polystyrene Microplastics on Multiple Tetracycline Removals by Ferrate

Water treatment processes typically focus on eliminating organic pollutants in wastewater but often overlook the presence of coexisting microplastics. In this study, we examined the effects of polystyrene microplastics on removing three tetracyclines using ferrate. The presence of polystyrene microplastics influenced the efficiency of oxidation, adsorption, coagulation, and complexation, leading to varying degrees of tetracycline removal by ferrate. Our results showed that unaged polystyrene microplastics increased tetracycline removal by 29.2%, while three aged polystyrene microplastics showed an increased removal ratio, and ten soaked polystyrene microplastics inhibited tetracyclines removal by up to 41.6%. The breakdown of polystyrene microplastics also released small molecules and contributed to a 7.4% increase in total organic carbon. The carbonyl index of polystyrene microplastics also rose to 1.68, and specific functional groups, including C–O, C═O, Fe–O, and C–N–C, appeared on the surface. While polystyrene microplastics weakened the oxidation capacity of ferrate in removing tetracyclines, their increased surface area and pore volume aided in tetracyclines adsorption. Furthermore, polystyrene microplastics acted as support sites for Fe3+ and Fe(OH)3, facilitating the formation of polystyrene-Fe-tetracycline complexes, which aided in tetracycline removal via complexation. Fe(OH)3 helped with the adsorption and coagulation removal of tetracyclines. The potential adverse effects of polystyrene microplastics are widespread and require more attention in removing pollutants when microplastics coexist in aquatic environments.

Explicating the fertilizer potential of anaerobic digestate: Effect on soil nutrient profile and growth of Solanum melongena L.

The use of anaerobic digestate (ADg), a nutrient-rich residual product of the anaerobic digestion (AD) process, could be a promising strategy for nutrient recycling in agriculture. However, when analyzing the usage of waste digestate as an organic amendment, properties such as organic and nutritional content, hygienic quality, and stability are important factors to consider. In this context, the present study elucidates the suitability of ADg as a fertilizer supplement based on agricultural criteria, including soil nutrient dynamics and the growth performance of brinjal (Solanum melongena L. var. Kashi Uttam). Pot experiments were conducted to explore the viability and response of ADg produced from three different organic wastes viz. the organic fraction of municipal solid waste (OFMSW), sewage sludge (SS), and flower waste (FW). Five fertilization treatments of each ADg, i.e., 0, 25, 50, 75, and 100%, designated as C, T1, T2, T3, and T4, were examined. The findings exhibited a significant (p<0.05) increase in Total Organic Carbon (TOC), exchangeable Na, K, Ca, and available P, while a considerable increment (p>0.05) in TKN was noticed in all the treatments. Biochemical analyses of brinjal depicted significant enhancement (p<0.05) in total chlorophyll (66.7 %) and carotenoid (56.03%) in T1 treatment of OFMSW ADg at 65 DAS. Likewise, maximum protein content increased by 326.8% in T2 of FW ADg at 65 DAS. However, a few of the metal contents also increased with increasing ADg(s) dosage but were well within the permissible limits of the Indian standard. A progressive increase in proline, peroxidase, and lipid peroxidation (p<0.05) was observed with increasing dosages, indicating metal-induced physiological stress in plants. However, improved ascorbic acid and phenol (23.8% at T2 treatment of OFMSW ADg) content allayed oxidative stress. Likewise, augmented morphological and yield (173.4% in T3 treatment of OFMSW ADg and 153.6% in T4 treatment of FW ADg) responses of brinjal in all the treatments showed their aptness for agricultural application with multifaceted environmental benefits. However, more research into the impacts of ADg on soil and plant growth and its transformation during AD is needed to identify the digestate’s end-use value.

Characterization of the Colloidal Properties of Dissolved Organic Matter From Forest Soils

Components of dissolved organic matter (DOM) span from sub-nm molecules to colloidal aggregates of several hundred nm. The colloidal fraction is important for the transport of organic matter and associated elements in the environment, and for the stability of DOM constituents with respect to microbial decomposition. This study focuses on the colloidal properties of DOM extracted from spruce forest soils of a chronosequence. The DOM samples were obtained by common water extraction procedures at 21 and 100°C, respectively. We applied an experimental approach combining chemical analysis with light and X-ray scattering techniques that informed on the colloidal size, charge, and structure of DOM. Results showed that two main types of colloids were present: semi-flexible cylinders and fractal aggregates. The cylinders consisted of carbohydrates, presumably hemicelluloses, while the aggregates were a composite material containing a large fraction of carbohydrates together with aliphatics and clay particles. These fractal aggregates dominated the cold-water extracts whereas the strong increase in total organic carbon by hot-water extraction caused a concomitantly strong increase of semi-flexible cylinders, which became the predominant species. Comparison between the chronosequence soils showed that with increasing forest age, the amount of carbon extracted per gram of soil declined and the concentration of the semi-flexible cylinders decreased. Thus, the distribution between the fractal aggregates and cylinders in the forest soil DOM samples depends on the composition of the soil organic matter and the leaching temperature. Changes in this distribution may have important implications for the reactivity and stability of DOM colloids.

Semi-continuous hydrolysis of onion skin wastes with subcritical water: Pectin recovery and oligomers identification

The semi-continuous hydrolysis of onion skin wastes (OSW) using subcritical water (SubW; working conditions: 105–180 °C; 5 MPa; 2.5 mL/min) has been studied in this work. Liquids after hydrolysis showed a sharp increase in total organic carbon (>30 mg/g OSW) at temperatures above 145 °C, when SubW began to promote the partial hydrolysis of the structural components of OSW. Among them, pectin was one of main components recovered (extraction yield up to 9% at 145 °C), whereas cellulose was barely hydrolyzed in the range of temperatures studied. The composition of pectin demonstrated that SubW promoted the recovery of the valuable RG-I (21.1 ± 1.1 mol%) regions compared to acid water extraction processes (10.8 ± 0.9 mol%). The control of the hydrolysis conditions was found to be critical, since high temperatures and long hydrolysis times led to the formation of organic acids (acetic, formic and levulinic) and degradation products such as furfural (up to 0.8 mg/g OSW) from the C5 sugars. Finally, the High Heating Value (HHV) calculated for the solid residue obtained at 180 °C (16.4 ± 0.2 MJ/kg) indicated the potential use of this residue as a fuel, once the valuable compounds (phenolics and pectins) have been recovered.

The Effects of Wastewater Treatment Plant Failure on the Gulf of Gdansk (Southern Baltic Sea).

In August 2019 and during August/September 2020, the main collection system of the Wastewater Treatment Plant (WWTP) in Warsaw, Poland, malfunctioned. During that system failure, over 4.8 million m3 of untreated wastewater was dropped directly into the Vistula River in just a few days. It is currently considered as one of the largest known failures of WWTP worldwide. In order to assess the environmental impact, water samples were collected from 2 spots at the Vistula river estuary (406 and 415 km from the discharge location, respectively), and 4 spots at the Gulf of Gdansk, situated on the southern shore of the Baltic Sea. The sampling was conducted before the wastewater wave reached the Vistula river’s mouth, followed by daily sampling during 21 days after the malfunction occurred. The study showed the decline in water quality at the Vistula river estuary and the Baltic shore waters as the wave of wastewater reached those points, despite being situated over 400 km downstream from the place of the accident. Those changes included the reduction in the dissolved oxygen content (by 0.69-fold at its peak), the increase in Total Organic Carbon (TOC) (by 1.28-fold at its peak), nitrate-nitrogen (N-NO3) (by 1.68-fold at its peak), phosphorous (P) (by 2.41-fold at its peak), conductivity (by 16.8-fold at its peak), and Chemical Oxygen Demand (COD) (by 1.84-fold). In the samples from the Vistula river, the decline in water quality was seen as incidental and lasted 2–3 days. Subsequently, the levels of physical and chemical parameters returned to the levels from before the accident. However, the changes in the Gulf of Gdańsk lasted significantly longer, especially on the West side of the Vistula river, where, even after 21 days from the initial accident, some parameters remained altered.

Potential of Floating Photovoltaic Technology and Their Effects on Energy Output, Water Quality and Supply in Jordan

In this work, floating photovoltaic systems were experimentally studied under Jordan’s weather conditions to determine their effects on energy output, water quality and supply. A limited number of studies have addressed the effect of floating photovoltaic systems on water quality and evaporation reduction especially in a semi-arid region like Jordan. Energy measurements were taken from August 2020 to January 2021 using an Arduino board with data logging sensors. Water quality parameters were tested for collected samples on a monthly basis from August 2020 to February 2021 using a spectrophotometer. Results revealed that the floating panel temperature was lower than the ground-mounted counterpart. An average increase of 1.68% in voltage and 4.40% in current were observed for the floating panel compared to the ground-mounted panel which translates to an average increase of 5.33% in power generation over the ground-mounted panel. Furthermore, efficiency and fill factor increased by 4.89% and 5.51%, respectively. Evaporation results showed that covering water bodies with panels can save a considerable amount of water. Over a period of 30 days, the 30% coverage pan saved 31.2% (36 mm) of water while the 50% coverage pan saved 54.5% (63 mm) of water in the same period compared to the uncovered pan. Moreover, this study involved examining the effect of shading caused by the floating structure on water quality. Results showed a reduction in pH, improvement in transparency, and an increase in total organic carbon indicating water quality enhancement and algal biomass reduction. However, due to the respiration of algae, the dissolved oxygen declined significantly, accompanied by the release of phosphate due to algae decomposition. Overall, findings of this research provided better understanding of floating photovoltaic systems and their applicability in Jordan to provide a safe and reliable supply of water and energy. Additionally, such systems can help to diversify the energy mix and help Jordan to alleviate some of the problems associated with limited energy and water resources.

Characteristics of Pore Structure and Gas Content of the Lower Paleozoic Shale from the Upper Yangtze Plate, South China

This study is predominantly about the differences in shale pore structure and the controlling factors of shale gas content between Lower Silurian and Lower Cambrian from the upper Yangtze plate, which are of great significance to the occurrence mechanism of shale gas. The field emission scanning electron microscopy combined with Particles (Pores) and Cracks Analysis System software, CO2/N2 adsorption and the high-pressure mercury injection porosimetry, and methane adsorption were used to investigate characteristics of overall shale pore structure and organic matter pore, heterogeneity and gas content of the Lower Paleozoic in southern Sichuan Basin and northern Guizhou province from the upper Yangtze plate. Results show that porosity and the development of organic matter pores of the Lower Silurian are better than that of the Lower Cambrian, and there are four main types of pore, including interparticle pore, intraparticle pore, organic matter pore and micro-fracture. The micropores of the Lower Cambrian shale provide major pore volume and specific surface areas. In the Lower Silurian shale, there are mesopores besides micropores. Fractal dimensions representing pore structure complexity and heterogeneity gradually increase with the increase in pore volume and specific surface areas. There is a significant positive linear relationship between total organic carbon content and micropores volume and specific surface areas of the Lower Paleozoic shale, and the correlation of the Lower Silurian is more obvious than that of the Lower Cambrian. The plane porosity of organic matter increases with the increase in total organic carbon when it is less than 5%. The plane porosity of organic matter pores is positively correlated with clay minerals content and negatively correlated with brittle minerals content. The adsorption gas content of Lower Silurian and Lower Cambrian shale are 1.51–3.86 m3/t (average, 2.31 m3/t) and 0.35–2.38 m3/t (average, 1.36 m3/t). Total organic carbon, clay minerals and porosity are the main controlling factors for the differences in shale gas content between Lower Cambrian and Lower Silurian from the upper Yangtze plate. Probability entropy and organic matter plane porosity of the Lower Silurian are higher than those of Lower Cambrian shale, but form factor and roundness is smaller.

Distribution Patterns of Benthic Foraminifera in Fish Farming Areas (Corsica, France): Implications for the Implementation of Biotic Indices in Biomonitoring Studies

Corsican marine aquaculture is one of the highest contributors of fish production in France, which may result in environmental perturbations caused by organic matter (OM) accumulation under fish farms and impacting natural communities. This study aimed to (1) characterise the environmental conditions at two different fish farms, (2) monitor the response of benthic foraminiferal species to this activity, and (3) assess the accuracy of existing foraminiferal biotic indices. In 2017, sea floor sediment was sampled in transects from two Corsican fish farms for living foraminiferal and sedimentary analyses. Four indices were calculated and compared: exp(H′bc), Foram-AMBI, Foram Stress Index and TSI-Med. A significant increase in total organic carbon (TOC) has been shown, mainly below the fish cages. Communities were characterized by a shift from high density, opportunistic and tolerant species under the cages to lower densities and more sensitive species further away. According to their distribution patterns along the TOC gradient, we propose to update the ecological group classification of seven species to improve Foram-AMBI’s accuracy and sensitivity: Triloculina oblonga and Quinqueloculina lamarckiana to Ecological Group (EG) I; Rosalina bradyi to EGIII; and Bolivina dilatata, Bulimina aculeata and Quinqueloculina stalkeri to EGIV. We recommend prioritising the use of TSI-Med and Foram-AMBI with the updated list to assess ecological quality in coastal waters of the Mediterranean Sea.

Chemoautotrophy as the driver of decoupled organic and carbonate carbon isotope records at the onset of the Hangenberg (Devonian-Carboniferous Boundary) Oceanic Anoxic Event

New high-resolution organic (δ13Corg) and carbonate (δ13Ccarb) carbon isotope data from middle shelf deposits in southeastern Iowa demonstrate decoupled signals during the onset of the Hangenberg Event and across the Devonian-Carboniferous Boundary. High-resolution sampling captures a transient negative excursion in δ13Corg during the initiation of rising δ13Ccarb values at the onset of the Hangenberg Event that ends prior to the onset of the final rise in δ13Ccarb to values greater than +6.0‰ in the Louisiana Limestone. This negative excursion in δ13Corg is coincident with a significant increase in Total Organic Carbon (TOC) content in the underlying English River Formation, which likely corresponds to the well-known Hangenberg Black Shale of the classical European sections. The complex behavior of the carbon isotope record recovered here, combined with recently published geochemical data from classical European sections, demonstrate that a succession of geochemical events took place during the initiation of this global biogeochemical event that include a negative excursion in both δ13Ccarb and δ13Corg prior to the major positive carbon isotope excursion, and that the role of organic carbon burial in this Devonian Oceanic Anoxic Event (OAE) extends well beyond the depositional interval of the Hangenberg Black Shale.

The in situ treatment of Basic Violet 16 synthetic dye in groundwater

AbstractSynthetic dyes have been shown to be micropollutants in various aquatic and groundwater systems, often occurring at milligram per liter (mg/L) concentrations. Synthetic dyes are typically introduced into the environment either as a continuous stream from wastewater or as episodic events related to the disposal of residues or spills generated during the manufacturing process. Various studies for the treatment of synthetic dyes have been undertaken for wastewater but studies for the in situ treatment of synthetic dyes in groundwater are limited. A pilot‐scale test was conducted to determine if the use of colloidal activated carbon (CAC) could effectively reduce dissolved concentrations of the synthetic dye Basic Violet (BV16) in groundwater using in situ methods. The pilot test was carried out downgradient of a textile manufacturing facility where historic disposal practices resulted in the release of various chemicals of concern including BV16 to an unconfined silty sand aquifer. A 10‐weight percent CAC solution was injected into a series of temporary direct push injection points to target the synthetic dye that was present at concentrations of up to 1,640 micrograms per liter (μg/L) during the 738‐day study. The results from the pilot test indicated that the CAC was effectively delivered to the target injection zone resulting in a three order of magnitude increase in total organic carbon (TOC) concentrations compared to preinjection TOC concentrations within the aquifer. Distribution of the CAC within the targeted injection zone indicated that heterogeneity affected the distribution with a zone of higher horizontal hydraulic conductivity (KH) having an average TOC concentration approximately 100 percent greater than the mean TOC concentration within the surrounding aquifer targeted by the CAC injection. Analyses of the groundwater chemistry before and postinjection indicated that the CAC had no detrimental impact on the groundwater quality while reducing the concentration of dissolved BV16 within the plume to below the method detection limits within 62 days of injection. The concentration of BV16 remained below the method detection limit of 10 µg/L for the 738‐day duration of the study apart from one detection of 180 µg/L at Day 183 within groundwater sampled from one monitoring well suggesting that the CAC was effective in attenuating the BV16 over the short and moderate term.

Post-Fire Impacts of Vegetation Burning on Soil Properties and Water Repellency in a Pine Forest, South Korea

Forest fires can have a direct and immediate impact on soil properties, particularly soil water repellency. This study investigated the direct impacts of the Gangneung forest fire of 2019 on soil properties and the spatial variability of soil water repellency with vegetation burn severity in the Korean red pine (Pinus densiflora Siebold and Zucc) forest of South Korea. A total of 36 soil samples were collected at depth intervals of 0–5 cm, 10–15 cm, and 20–25 cm from three burned sites, representing surface-fuel consumption (SC), foliage necrosis (FN), and crown-fuel consumption (CC), respectively. An unburned site was also used as a control. Soil properties such as soil texture, pH, bulk density, electrical conductivity (EC), total organic carbon (TOC), and cation exchange capacity (CEC) were analyzed in the laboratory. The increase in the sand fraction near the soil surface after a fire was associated with changes in silt and clay fractions. Moderate to high vegetation burn severity at the FN and CC sites caused a decrease in soil pH due to the thermal destruction of kaolinite mineral structure, but organic matter combustion on the soil surface increased soil pH at the SC site. Forest fires led to increases in total organic carbon at the FN and SC sites, owing to the external input of heat damaged foliage and burnt materials. Molarity of an ethanol droplet (MED) tests were also conducted to measure the presence and intensity of soil water repellency from different locations and soil depths. MED tests showed that vegetation burn severity was important for determining the strength of water repellency, because severely burned sites tended to have stronger water repellency of soil than slightly burned sites. Unburned soils had very hydrophilic characteristics across soil depths, but a considerably thick hydrophobic layer was found in severely burned sites. The soil water repellency tended to be stronger on steep (&gt;30°) slopes than on gentle (&lt;15°) slopes.

Natural horticultural systems in organic farming as a tool for resilience: improvement of economic performance and prevention of soil erosion

ABSTRACT In the Mediterranean area many organic farms oriented toward the marketing of fresh products or toward agro-food processing have been interested in the conversion of at least a part of their horticultural production to natural cultivation systems in order to supply “natural” food to satisfy a particular market demand. In this study, the role of natural agriculture has been investigated in order to evaluate its effects in environmental safeguarding and organic farm production, contrasting soil erosion and soil organic matter decline, maintaining general soil fertility on hilly farms and supporting income in the context of climate change. This study is a field trial on a hilly farm, which compared a natural plot to an organic one. It showed that in the plot conducted with natural farming, total soil organic C increased significantly compared to the organic plot, from 1.97% to 4.16%. In organic farming system a significant increase of Total Organic Carbon (TOC) at the lower part of plot was observed as a consequence of soil loss (+ 25%). An economic analysis of the two farming systems on four farms, carried out considering the average costs and the average revenues, highlighted for the first time the greater profitability of natural cultivation compared to organic farming (+43%). The balance between safe food production, natural resources management and economic performance, obtained by substituting the organic farming with natural techniques, provides new and effective resilient agricultural practices to the organic farm sector.

Dynamics of Soil Nutrients, Microbial Community Structure, Enzymatic Activity, and Their Relationships along a Chronosequence of Pinus massoniana Plantations

Pinus massoniana is the major afforestation and vegetation restoration tree in southern China, and it plays an important role in the sustainable development of plantations. However, long-term single planting of P. massoniana has resulted in the decline of soil quality and forest productivity, and a soil fertility assessment is urgently needed. We selected P. massoniana plantations of four age stages for plot investigation and sampling to determine the soil physicochemical properties, microbial diversity and composition, and enzyme activities at different soil depths. The results showed that soil total phosphorus (TP) and available phosphorus (AP) decreased with the increase of age, especially low C/N ratio and high C/P and N/P ratio in the 30-year and 36-year stands, leading to P limitation. Meanwhile, the bacterial Shannon index also decreased with the increase of age and was positively correlated with AP, NO3−-N, and pH. However, the fungal Shannon index decreased first and then increased with the increase of age; soil acid phosphatase (S-ACP) and urease activities showed a similar trend. Correlation analysis demonstrated that the increase of total organic carbon (TOC) and total nitrogen (TN) promoted the increase of fungal Shannon index, which was beneficial to the secretion of more enzymes. We found that soil physicochemical properties, microbial diversity, and enzyme activity decreased simultaneously when soil depths increased. Moreover, Acidobacteria and Basidiomycota were the most abundant bacterial and fungal communities, respectively, followed by Proteobacteria and Actinobacteria for bacteria and Ascomycota for fungi, and these microbial taxa were significantly affected by soil water content (SWC), TOC, AP, and C/P. In conclusion, this work reveals the potential correlation among soil physicochemical properties, microbial diversity and composition, and enzyme activities, and revealed potential correlations among them which will help to improve understanding of soil conditions and provide a reference for rational management of soil resources.

Allium cepa L. Inoculation with a Consortium of Plant Growth-Promoting Bacteria: Effects on Plants, Soil, and the Autochthonous Microbial Community.

The present work was aimed at investigating the effects of a four bacterial strain consortium—Azospirillum brasilense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, and Burkholderia ambifaria—on Allium cepa L. and on soil health. The bacterial consortium was inoculated on seeds of two different onion varieties; inoculated and Control seeds (treated with autoclaved inoculum) were sown in an open-field and followed until harvest. Plant growth development parameters, as well as soil physico–chemical and molecular profiles (DNA extraction and 16S community sequencing on the Mi-Seq Illumina platform), were investigated. The results showed a positive influence of bacterial application on plant growth, with increased plant height (+18%), total chlorophylls (+42%), crop yields (+13%), and bulb dry matter (+3%) with respect to the Control. The differences between Control and treatments were also underlined in the bulb extracts in terms of total phenolic contents (+25%) and antioxidant activities (+20%). Soil fertility and microbial community structure and diversity were also positively affected by the bacterial inoculum. At harvest, the soil with the presence of the bacterial consortium showed an increase in total organic carbon, organic matter, and available phosphorus, as well as higher concentrations of nutrients than the Control. The ecological indexes calculated from the molecular profiles showed that community diversity was positively affected by the bacterial treatment. The present work showed the effective use of plant growth-promoting bacteria as a valid fertilization strategy to improve yield in productive landscapes whilst safeguarding soil biodiversity.