Changes In Total Organic Carbon Research Articles

Evaluation of detached plume and total organic carbon in the main chimney of the Indocement Plant 9-10 Palimanan to optimize clinker production and its influence on SO2 emissions

Detached Plume is the phenomenon of the formation of a cloud of gas/smoke that is interrupted in the main chimney of a cement Plant from the combustion of a kiln containing compounds consisting of Ammonia, Sulfur and Organic Carbon. The Detached Plume that occurred at Plant 9-10 of Indocement-Palimanan was analyzed and controlled so that the SO2 emissions produced could be reduced. This research aims to analyze the effect of Total Organic Carbon (TOC) on clinker production at Plant 9-10, understand the control of Detached Plume and SO2 emissions produced in the main chimney of Plant 9-10, and determine the optimization of the clinker production process at Plant 9-10 by Total Organic Carbon as a variable in Raw Meal. The analysis methods used include monitoring the Detached Plume phenomenon in the Main Chimney, its effect on SO2 Emissions, observing the effect of TOC changes in Raw Material on Clinker production capacity at Plant 9-10. The research results show that the TOC value of Plant 9 is 1.22%, thereby reducing Clinker production capacity to 3466 tpd from the target of 3600 tpd. On the other hand, the TOC value for Plant 10 in the month was 1.00%, thereby reducing Clinker production capacity to 4070 tpd from the target of 4200 tpd. This shows that a significant increase in TOC value in Raw Meal reduces Clinker production capacity. The Detached Plume is also influenced by the ammonia gas content in the main chimney emissions, where the ammonia content > 2 mg/Nm3 increases the visibility of the Detached Plume in the main chimney of Plant 9-10, and the SO2 value

Substitution of Chemical Fertilizer with Organic Fertilizer Can Affect Soil Labile Organic Carbon Fractions and Garlic Yield by Mediating Soil Aggregate-Associated Organic Carbon

This study aimed to explore the impact paths on soil organic carbon and crop yield of completely or partially substituting chemical N fertilizer with organic fertilizers. A four-year field experiment was conducted and included four treatments: (i) N0, no N fertilization application; (ii) NF, only synthetic N fertilizer application; (iii) 1/2OF, organic fertilizer substituted for 100% of the synthetic N fertilizer, with the total N application amount being equivalent to half that of NF; and (iv) 1/3OF + 2/3NF, organic fertilizer substituted for 1/3 of the synthetic N fertilizer with the total N application amount from organic and synthetic fertilizer being equivalent to that of NF. Soil total organic carbon (TOC), labile organic-carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), and easily oxidized organic carbon (EOC)), the carbon pool management index (CPMI), soil aggregated distribution, and water-stable aggregate-associated organic carbon were determined. Structural equation modeling (SEM) was used to clarify the impact paths of TOC and garlic yield changes under different N fertilizer treatments. Results showed that compared with N0 and NF, 1/2OF and 1/3OF + 2/3NF significantly increased TOC contents by 14.1–20.6%. Soil MBC, DOC, and EOC under 1/2OF were significantly higher than under N0, whereas the 1/3OF + 2/3NF treatment had significantly greater POC. The CPMI was improved by organic fertilizer treatment, with 1/2OF treatment being significantly higher than N0 and NF. The proportion of soil aggregate mass with particle sizes >2 mm was significantly greater under N0, while 1/3OF + 2/3NF significantly increased the proportion of particle sizes of 0.5–2 mm. Soil water-stable aggregate-associated organic carbon showed a trend of first increasing and then decreasing, with the largest particle sizes being 1–2 mm. Moreover, organic fertilizer significantly increased soil water-stable aggregate organic carbon compared with N0 and NF. Similarly, the garlic yield increased with organic fertilizer treatment, while 1/3OF + 2/3NF significantly increased the yield by 37.2% and 15.3%, respectively, compared with N0 and NF. Furthermore, SEM analysis indicated that fertilizer regimes could directly affect TOC and labile organic carbon components by affecting aggregate-associated organic carbon. In particular, aggregates with particle sizes of 0.5–2 mm played an important role, indirectly affecting garlic yield and CPMI. These results indicate that organic fertilizer application has the potential to improve soil organic-carbon content and garlic yield; moreover, fully applying organic fertilizer can reduce N fertilizer input while still maintaining an increase in soil organic carbon and crop yield in the short term. However, caution is still needed regarding of the type and quantity of organic fertilizer added in different cropping systems, and with different soil textures.

Sediment organic carbon and nitrogen trapping in a small reservoir within a typical agricultural granite catchment

Small reservoirs are more widely distributed globally than larger reservoirs, and they have characteristic sediment total organic carbon (TOC) and total nitrogen (TN) trapping patterns that differ from those of larger reservoirs. Few studies have quantified the TOC and TN trapping in a small reservoir within a catchment underlain by a single lithology, particularly in non-karst terrain, from the perspective of environmental change. Based on the chronologies established using 137Cs and 210Pbex, we assessed the temporal patterns of sediment TOC and TN trapping in a small reservoir within a typical agricultural granite catchment (Yimeng Mountains, China) by examining depth trends in TOC and TN concentrations in three sediment cores and temporal trends in TOC and TN deposition rates in the reservoir over the past ∼60 years. The TOC and TN concentrations and C/N ratios show an overall upward increase in the three cores. The TOC and TN deposition rates were relatively high during 1954–1962, decreased to the lowest rates during 1963–1972, and generally increased thereafter. Anthropogenic sources associated with agriculture were the dominant factor in the up-core increases in TOC and TN concentrations, although natural sources were the main contributor to TOC and TN deposition. The temporal changes in TOC and TN deposition rates were mainly due to the sediment yield rather than anthropogenic sources associated with agriculture. The changes in TOC and TN concentrations with depth, and temporal changes in the TOC and TN deposition rates determined from the three cores, reflect the temporal patterns of sediment TOC and TN trapping in the small reservoir over the past ∼60 years. Sediment yield exerted a greater effect on the TOC and TN deposition in the studied reservoir, as compared with a previously reported reservoir within a small agricultural limestone catchment, and the different results of the two studies originated from the contrasting lithologies in the two catchments. Moreover, a comparison with data obtained for a previously studied large reservoir suggests that differences in TOC and TN deposition (including concentrations, specific deposition rates, and temporal trends in deposition rates) are related to catchment size, and the comparison highlights the characteristic patterns of TOC and TN trapping in the small and large reservoirs. The present findings improve our understanding of the temporal patterns of sediment TOC and TN trapping in a small reservoir within a typical agricultural granite catchment in terms of environmental changes influenced by human activity. This study also enhances our knowledge of the barrier effects of a dam on the downstream transport of TOC and TN in a small catchment in a non-karst setting, and the redistribution of sediment TOC and TN in a large river, which can help guide strategies for water resource management on the river basin-scale.

An experimental investigation into the elastic and thermal properties of oil shales: Yanchang formation, Ordos basin

The relationship between oil shale's elastic behavior and geothermal parameters is vital in sweet spot identification and in-situ oil conversion techniques. To qualitatively study the elastic P- and S-wave velocities and thermal properties of oil shales, we simultaneously make ultrasonic measurement s and investigate geothermal properties in the Triassic Yanchang Formation. The results demonstrate that ultrasonic P-wave velocities are sensitive to the pressure of <5 MPa mainly due to the closure of the soft pores/cracks and kerogen content and distribution. Thermal experiments reveal that kerogen content has a significant influence on shale's thermal expansion coefficients (TEC) and heat capacity. Specifically, organic-rich shales show the highest thermal expansion coefficients in both directions in core plugs (0° and 90°), reaching a maximum of 5 × 10−5 °C−1 and the highest heat capacity compared to the other samples. On the contrary, mudstone has a relatively low thermal expansion coefficient of 1 × 10−5 °C−1. The variation trend of the TEC of typical shale samples with the change of TOC (total organic carbon) content indicates that existing four phases of TEC correspond to different dominant rock evolution. These observations imply that low ultrasonic velocities accompanied by high thermal properties (heat capacity, TEC) can be ‘sweet spot’ indicators for high TOC reservoir zones. The experiments prove that the quartz content has a significant influence on the ultrasonic P- and S-wave velocities and TEC of shale rocks. Both ultrasonic velocities and thermal parameters of shales exhibit a distinct change at ∼40% quartz volume, responding to a change in the rock skeleton, and a change in TOC content. These observations will thoroughly assist us in understanding the elastic signature and thermal properties of shales during in-situ conversion process of shale oil reservoirs in Ch7 Member of the Yanchang Formation, in the Ordos Basin, Northwest China.

Long-term Influence of Crop Residue Management and Tillage Practices on Distribution of C and N within Aggregate Size Fractions in Alluvial Soils

Aims: The goal of this experiment is to observe the variations in soil aggregate fractions and the change in percentage of carbon and nitrogen stored in the fractions due to the effect of crop residue management and tillage practices in Rice-Wheat cropping system.&#x0D; Study Design: An experiment was set up in Randomized Block Design with five treatments, i.e, T0-control, T1- zero-tillage+ no residue application, T2- zero-tillage+ residue application, T3- conventional tillage + no residue application, T4- conventional tillage+ residue application.&#x0D; Place and Duration of Study: It was conducted in a long-term experimental plot situated in University Research Farm at Pundibari in Coochbehar district of West Bengal. The data was taken in the 9th and 10th year of the experiment, i.e, 2018 and 2019.&#x0D; Methodology: Samples were collected from three different depths, i.e., 0-5 cm, 5-15 cm and 15-30 cm from four cropping seasons, i.e., wheat 2018, rice 2018, wheat 2019 and rice 2019 and were prepared and analyzed for physico-chemical factors. Dry stable aggregates were obtained by the method of sieving and change of carbon, nitrogen and C/N ratios in various fractions were observed.&#x0D; Results: Mostly for all the soil depths the total organic carbon content was highest for the treatment with zero-tillage and application of residues (T2). Total nitrogen content also followed the similar trend. Whereas in most of the crop seasons, the C/N ratio was observed to be higher in the treatment where conventional tillage was followed along with residue incorporation (T4). Within the short span of two years positive changes in total organic carbon and total nitrogen content was observed for almost all the treatments, across the depths.&#x0D; Conclusion: The optimum percentage of decrease in C/N ratio of the control as well as the treatment with zero-tillage and residue application (T2) in the large aggregate fractions (&lt;2mm) indicates the suitability of the soil for higher productivity.

Sheepfolds induce significant increase of seasonal CO2, CH4 and N2O emissions in temperate steppes of Inner Mongolia

IntroductionThe changes in grassland management and grassland types are strongly linked with dynamics in soil physico-chemical properties and vegetation attributes, with important implications for carbon/nitrogen cycling and greenhouse gas (GHG) fluxes. However, the seasonal variations of GHG emissions from sheepfolds, and the underlying biotic and abiotic drivers affecting GHG exchanges across different steppe and management types remain largely unclear.MethodsTaking the Inner Mongolian grassland as a model system, we measured the fluxes of CO2, CH4 and N2O, as well as soil and vegetation variables, in three contrasting grassland management areas (grazing, sheepfold, enclosure) and in three representative (wet typical, dry typical, desert) grassland ecosystems in July, September and November 2016.ResultsOur results showed that: (1) GHG fluxes were mostly higher in the plant growing season (July and September) than in the nongrowing season (November); sheepfold area had significantly higher GHG emissions (in July and mean over the season) than enclosed and grazing areas, with the effects being most pronounced in dry typical steppe. (2) The high GHG emissions in dry typical steppe were closely associated with the interactions among favorable soil temperature and moisture, high total organic carbon (TOC) content, and high aboveground biomass. The important predictors for CO2 emission were soil TOC and pH, whereas that for CH4 and N2O emissions were soil temperature and moisture content, in sheepfold areas. (3) Three GHG emissions were negatively affected by species richness across all steppe and management types, which might be a consequence of indirect effects through the changes in soil TOC and total nitrogen (TN).DiscussionThese results indicate that sheepfold areas are intensive hotspot sources of GHGs in the steppes, and it is of great importance to help to account GHG emissions and develop mitigation strategies for sheepfold areas for sustainable grassland management in the natural steppe based pastoral production ecosystems.

Fiberglass cloth coated by coffee ground waste-derived carbon quantum dots/titanium dioxide composite for removal of caffeine and other pharmaceuticals from water

Coffee ground waste from the coffee beverage preparation is mainly discarded and consequently ends up in landfill, which cause the contamination of caffeine in various environmental compartments. This study focuses on the upcycling of coffee-ground waste to carbon quantum dots (CQDs) for use as a modifying material to improve the visible light activity of titanium dioxide (TiO2). The CQD solution was synthesized by hydrothermal method, which has an average size of 2.80 ± 0.63 nm. The CQDs/TiO2 photocatalysts were prepared by combining CQD solutions at various amounts with sol-gel TiO2 and then coated on the fiberglass cloths (FGCs). The photocatalytic application mainly focuses on the removal of caffeine from the water. The photocatalytic experiment was preliminary run in a simple batch reactor under visible light. The 5CQDs/TiO2 coated FGC (5 mL of CQD solution/g of Ti-based on sol-gel) showed the best performance, and it was selected for the removal of caffeine and other pharmaceuticals (i.e., carbamazepine and ibuprofen) in the recirculating reactor. The removals of caffeine, carbamazepine, and ibuprofen after irradiation for 9 h were 82%, 88%, and 84%, respectively. The residual concentrations were significantly lower than the reported toxicity levels based on specific species. The changes in total organic carbon were observed, indicating the mineralization of pharmaceuticals in water. The 5CQDs/TiO2 coated FGC showed good flexible performance. No obvious loss of activity was observed for five runs. The actual wastewater from the coffee pot cleaning process was also tested. The removal was 80% for caffeine and 86% for color in the unit of the American Dye Manufacturers Institute (ADMI).

Temporal trend evaluation in monitoring programs with high spatial resolution and low temporal resolution using geographically weighted regression models

Data from monitoring programs with high spatial resolution but low temporal resolution are often overlooked when assessing temporal trends, as the data structure does not permit the use of established trend analysis methods. However, the data include uniquely detailed information about geographically differentiated temporal trends driven by large-scale influences, such as climate or airborne deposition. In this study, we used geographically weighted regression models, extended with a temporal component, to evaluate linear and nonlinear trends in environmental monitoring data. To improve the results, we tested approaches for station-wise pre-processing of data and for validation of the resulting models. To illustrate the method, we used data on changes in total organic carbon (TOC) obtained in a monitoring program of around 4800 Swedish lakes observed once every 6 years between 2008 and 2021. On applying the methods developed here, we identified nonlinear changes in TOC from consistent negative trends over most of Sweden around 2010 to positive trends during later years in parts of the country.

Cover legumes promote the growth of young rubber trees by increasing organic carbon and organic nitrogen content in the soil

Cover crops are often intercropped in rubber plantations to improve utilization of understory space; however, how cover crops promote the growth rate (GR) of young rubber trees remains unclear, as these are largely dependent on the growth time and varieties of cover crops. We conducted a five-year experiment with five cover crop treatments of no cover crop (CK) and cover with four varieties of perennial leguminous crops, namely, Stylosanthes guianensis Reyan No. 2 (RY2), Reyan No. 5 (RY5), Reyan No. 7 (RY7), and Reyan No.10 (RY10). We analyzed changes in total organic carbon (TOC), total nitrogen (TN), and the fractions of labile organic carbon (LOC), mineral nitrogen (MN), and organic nitrogen (ON) in understory soil of young rubber plants (Hevea Brisiliensis cv. Reyan 7–33–97) in tropical China and their effects on the GR. The results showed that cover year and cover crop varieties significantly affected soil TOC, LOC fractions, TN, MN, and ON fractions, as well as GR. Compared to CK, the five-year average GRs of rubber trees covering the RY2, RY5, RY7, and RY10 increased by 12.8%, 41.5% 30.0%, and 43.1%, respectively. Compared with CK, the five-year average nutrients of RY5 and RY10 all increased after covering, whereas the soil NH4+-N of RY2 decreased by 0.3%. Meanwhile, the soil TOC, TN, acid-hydrolyzable ammonium nitrogen (AN), and amino acid nitrogen of RY7 decreased by 10.1%, 13.4%, 6.7%, and 21.3%, respectively. The soil nutrients all show a good linear relationship with GR. We identified TN and MN as the main nutrients for the growth of young rubber plants through linear regression and stepwise regression. In addition, structural equation modeling indicated that TOC was the carrier of nitrogen transformation and utilization in soil. The total effects of TOC, AN, and NH4+-N on GR of rubber trees were 0.55, 0.52, and 0.31, respectively. The results demonstrated that RY5 and RY10 are suitable for young rubber plantation in tropical China as these effectively improved soil nitrogen supply potential, improved soil fertility, and promoted the GR of young rubber trees.

Microbial Composition on Abandoned and Reclaimed Mining Sites in the Komi Republic (North Russia)

Restoration of anthropogenically disturbed soils is an urgent problem in modern ecology and soil biology. Restoration processes in northern environments are especially important, due to the small amounts of fertile land and low levels of natural succession. We analyzed the soil microbiota, which is one of the indicators of the succession process is the soil. Samples were obtained from three disturbed soils (self-overgrown and reclaimed quarries), and two undisturbed soils (primary and secondary forests). Primary Forest soil had a well-developed soil profile, and a low pH and TOC (total organic carbon) amount. The microbial community of this soil had low richness, formed a clear remote cluster in the beta-diversity analysis, and showed an overrepresentation of Geobacter (Desulfobacteriota). Soil formation in clay and limestone abandoned quarries was at the initial stage, and was caused by both a low rate of mineral profile formation and severe climatic conditions in the region. Microbial communities of these soils did not have specific abundant taxa, and included a high amount of sparse taxa. Differences in taxa composition were correlated with abiotic factors (ammonium concentration), which, in turn, can be explained by the parent rock properties. Limestone quarry reclaimed by topsoil coverage resulted in an adaptation of the top soil microbiota to a novel parent rock. According to the CCA analysis, the microbial composition of samples was connected with pH, TOC and ammonium nitrogen concentration. Changes in pH and TOC were connected with ASVs from Chloroflexota, Gemmatimonadota and Patescibacteria. ASVs from Gemmatimonadota also were correlated with a high ammonium concentration.

Long-term adoption of reduced tillage and green manure improves soil physicochemical properties and increases the abundance of beneficial bacteria in a Mediterranean rainfed almond orchard

Soil health and function is one of the most important components for sustainable management of woody orchards. Intensive use of machinery and tillage creates heavy pressure on agroecosystems by altering the soil physicochemical and biological characteristics. In this study we aimed to assess the changes in soil physicochemical properties and the soil bacterial community structure, as well as the main drivers involved in shifts in the microbial community following 10 years implementing reduced tillage and reduced tillage plus green manure in a rainfed Mediterranean almond orchard. The treatments were: i) conventional tillage (CT); ii) reduced tillage (RT); and iii) reduced tillage and diversification with Avena sativa and Vicia sativa (RTD). After ten years, the results showed that the different managements had no significant effect on almond yields. RTD significantly increased total organic carbon (TOC), with an average content of 19.5 g kg−1 compared to 17.1 g kg−1 in CT. RTD also contributed to an increase in the fraction of soil macro-aggregates. Both RT and RTD significantly increased soil total nitrogen (NT) and particulate organic carbon (POC). However, other physical and chemical variables such as exchangeable Ca, Mg and K, bioavailable Fe, Cu, Zn and Mn, cation exchange capacity, bulk density, wilting point and field capacity were not significantly affected by the management. The bacterial community significantly changed with management: RTD showed a higher relative abundance of the family Solirubrobacteraceae and the genera Streptomyces and Solirubrobacter. The bacterial community structure was explained by changes in TOC, POC, pH, and NT values. Thus, a combination of reduced tillage and green manure could represent an appropriate sustainable management for rainfed almond orchards in very fragile environmental conditions, due to an increase in soil organic matter, total nitrogen, and the higher presence of beneficial bacteria related to soil productivity.

Size-dependent associations of woody plant structural diversity with soil C:N:P stoichiometry in a subtropical forest

Woody plant structural diversity and soil C:N:P stoichiometry have widely been examined for their spatial patterns and changes across environmental gradients, but the interactions and relationship of these biotic and abiotic variables have not been well understood. Here, we investigated the associations of woody plant structural diversity variables with soil total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), and their stoichiometry. We found only weak associations between soil C:N:P stoichiometry and species diversity variables, however, stronger significant associations were detected between C:N:P stoichiometry and species diversity variables for the adult trees and saplings when analyses were carried out with appropriate size stratification of woody plants. Most size diversity variables were significantly correlated with TOC, TN, TP, and their stoichiometric ratios, and the size diversity variables were greater in strength than species diversity in their associations with TOC, TN, TP, and C:N:P stoichiometric ratios. In most cases, C:N:P stoichiometric ratios were more sensitive than TOC, TN, or TP in predicting species diversity and size diversity. Our findings demonstrate that the associations of woody plant species diversity with TOC, TN, TP, C:N:P stoichiometry are size-dependent, and the size diversity is much more sensitive than species diversity in predicting the change of soil TOC, TN, TP, and C:N:P stoichiometric ratios. These findings also suggest that an appropriate size stratification will help demonstrate the linear relations between woody plant structural diversity and C:N:P stoichiometry and amplify the environmental signals from soil factors in predicting the biotic variables.

Profile Soil Carbon and Nitrogen Dynamics in Typical Chernozem under Long-Term Tillage Use

For the first time in research literature, this report presents the seasonal changes of total organic carbon (TOC), total nitrogen (TN), and TOC:TN ratio in Chernozem solum (0–100 cm) as effected by 14 years of application of conventional tillage (CTu), deep reduced tillage (DRTu), and reduced tillage (RTu) under barley growing. During the season, TOC content drastically declined in the spring, increased in the summer, decreased in the middle of August, and recovered in October. TN content was gradually decreased during a crop growing season and renewed in the autumn. A trend of TOC:TN changes (vertical peak curve) in 0–30 cm soil layer varied from TOC (S-shaped curve) and TN (unsymmetrical decayed curve). The amplitude of seasonal TOC and TN changes in deeper layers was far fewer related to the upper horizons. The highest amplitude in 0–30, 30–60 and 60–100 cm layers was under: DRTu, CTu, DRTu—for TOC and DRTu, CTu, RTu—for TN correspondently. Tillage practices differently stratified the content of organic carbon and nitrogen in Chernozem profile. Minimum tillage benefited TOC sequestration in 0–5 and 5–10 cm layers: 24.83 ± 0.64- and 24.65 ± 0.57 g kg−1—under RTu, 24.49 ± 0.62- and 24.71 ± 0.47 g kg−1—under DRTu, while CT—deeper than 20 cm: 22.49–15.03 g kg−1. The vertical distribution of TN content repeated TOC trend. TOC:TN ratio upraised from 12.60 in 0–5 to 14.33 in 80–100 cm layer and was the highest in summertime. A total (0–100 cm) profile was much greater under RTu and DRTu—for TN, and CTu, DRTu—for TOC. The correlation coefficient (r) was almost negligible between TOC and: T (air temperature), P (precipitation) and W (soil moisture). The strong and very strong r was found for TN—W, and P—W pairs. The negative r was between: TOC–P, TN–P, TOC:TN-W, TOC:TN–T and P–W pairs.

Occurrence of polycyclic aromatic hydrocarbons in the estuarine sediments of the Taihu Lake and their associated toxic effects on aquatic organisms

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous toxic organic pollutants in the natural environment that are strongly associated with socioeconomic activities. Exploring the distribution, sources, and ecological toxicity of PAHs is essential to abate their pollution and biological risks. Sixteen priority PAHs in different lakeside city estuarine sediments in northern Taihu Lake in China were determined by gas chromatography-mass spectrometry. Results showed that total concentrations of PAHs (ΣPAHs) ranged from 672.07 to 5 858.34 ng g -1 , with a mean value of 2 121.37 ng g -1 . High-molecular-weight PAHs (4–6 rings) were dominant, accounting for 85% of the ΣPAHs detected. Due to the barrier of gate/dam in the estuarine area, the concentrations of PAHs in the sediments were significantly different between the river mouth and lake side. Changes in total organic carbon (TOC) content and the spatial distribution of PAHs in the sediments were consistent. Sediment pollution assessment explored using the fuzzy evaluation model indicated 75% of slight PAH pollution. Some estuarine sediments (22%) concentrated in the east of Wuli Lake were moderately or heavily polluted. The PAHs may lead to occasional detrimental biological consequences in the area. Diagnostic ratios and principal component analysis-multiple linear regression suggested vehicle emission and natural gas combustion as the primary PAH contributors (81%).

Reduced tillage with residue retention improves soil labile carbon pools and carbon lability and management indices in a seven-year trial with wheat-mung bean-rice rotation

Soil total organic carbon (TOC) is a composite indicator of soil quality with implications for crop production and the regulation of soil ecosystem services. Research reports on the dynamics of TOC as a consequence of soil management practices in subtropical climatic conditions, where microbial carbon (C) loss is high, are very limited. The objective of our study was to evaluate the impact of seven years of continuous tillage and residue management on soil TOC dynamics (quantitative and qualitative) with respect to lability and stratification under an annual wheat-mung bean-rice cropping sequence. Composite soil samples were collected at 0-15 and 15-30 cm depths from a three-replicate split-plot experiment with tillage treatment as the main plots and crop residue levels as the sub-plots. The tillage treatments included conventional tillage (CT) and strip tillage (ST). Residue levels were high residue level (HR), 30% of the plant height, and low residue level (LR), 15%. In addition to TOC, soil samples were analyzed for particulate organic C (POC), permanganate oxidizable C (POXC), basal respiration (BR), specific maintenance respiration rate (qCO2), microbial biomass C (MBC), potentially mineralizable C (PMC), and TOC lability and management indices. The ST treatment significantly increased the TOC and labile C pools at both depths compared with the CT treatment, with the effect being more pronounced in the surface layer. The HR treatment increased TOC and labile C pools compared with the LR treatment. The ST + HR treatment showed significant increases in MBC, metabolic quotient (qR), C pool index (CPI), C lability index (CLI), and C management index (CMI), indicating improved and efficient soil biological activities in such systems compared with the CT treatment. Similarly, the stratification values, a measure of soil quality improvement, for POC and MBC were > 2, indicating improved soil quality in the ST + HR treatment compared with the CT treatment. The ST + HR treatment not only significantly increased the contents of TOC pools, but also their stocks. The CMI was correlated with qCO2, BR, and MBC, suggesting that these are sensitive indicators of early changes in TOC. The qCO2 was significantly higher in the CT + LR treatment and negatively correlated with MBC and CMI, indicating a biologically stressed soil condition in this treatment. Our findings highlight that medium-term reduced tillage with HR management has profound consequences on soil TOC quality and dynamics as mediated by alterations in labile C pools.

Changes in total organic carbon and organic carbon fractions of reclaimed minesoils in response to the filling of different substrates

Soil organic carbon (SOC) of reclaimed minesoil (RMS) is regarded as an important part of terrestrial SOC, and SOC losses of RMSs occur during the substantial soil compaction and the removal, storage and backfilling of the topsoil, which lead to poor soil structure. The filling of alternative soil substrates is considered to disturb the soil structure of RMSs, however, how SOC pool changes in the RMSs filled with various substrates and the mechanisms are less clearly understood. Therefore, a study on reclaimed area filled with three typical alternative soil substrates, including mining waste reclamation (MWR), river sand reclamation (RSR) and river mud reclamation (RMR), was started in mining area of Eastern China, where total SOC, labile SOC fractions, stable SOC fraction and soil physicochemical properties were measured. The results showed that (1) the total SOC, labile SOC fractions (microbial biomass carbon (MBC), readily oxidizable organic carbon (ROOC), light fraction organic carbon (LFOC) and particulate organic carbon (POC)) and stable SOC fraction (humic acids carbon (HAC)) contents of RMSs were lower than those of non-subsided cultivated land (NCL), the filling of alternative soil substrates had a significant effect on the SOC composition of RMSs, and the backfilling layer of RSR and the filling layer of MWR were more similar with NCL than other treatments in SOC composition; (2) In backfilling layer, bulk density (BD), connectivity index (τ), available phosphorus (AP), available potassium (AK) and soil urease (URE) were strong predictors for dissimilarities of SOC composition, and the difference in soil physics and soil fertility had more direct and indirect effects on the contents of SOC and SOC fractions; (3) In filling layer, water content (WC), macropore number (MN), microporosity (Φmac), available nitrogen (AN), electronic conductivity (EC), soil urease (URE) and sucrase (SUC) were strong predictors for dissimilarities of SOC composition, and the substrate texture and soil physics had more direct and indirect effects on the contents of SOC and SOC fractions. Easing the compactness and strengthening fertilizing management of backfilling layer, while improving the texture of filling substrates benefit the increasing of the SOC content of RMSs.

Driving Factors of Total Organic Carbon in Danjiangkou Reservoir Using Generalized Additive Model

Dynamic changes in total organic carbon (TOC) concentration in lakes and reservoirs affect the functions of aquatic ecosystems and are a key component of water quality management, especially in drinking water sources. The Danjiangkou Reservoir is the water source area of the Middle Route Project of the South-to-North Water Diversion in China. Its water quality is of critical importance to the safety of water diversion. TOC concentration and other environmental factors at 19 sampling sites in the Danjiangkou Reservoir were investigated quarterly during 2020–2021 to explore the differences at the spatio-temporal scales. A generalized additive model (GAM) was used to analyze the environmental factors correlated with the observed spatio-temporal variations of TOC concentration. The results showed that the comprehensive trophic level index (TLI) of the Danjiangkou Reservoir was under the state of intermediate nutrition, and the water quality was overall good. In terms of temporal patterns, TOC concentration was higher in both spring and summer and lower in other seasons. Spatially, TOC concentrations were found in descending order from the site of outlet, Han reservoir, entrance of reservoir, and Dan reservoir. The single-factor GAM model showed that TOC correlated with different environmental factors across spatio-temporal scales. Water temperature (WT), permanganate index (CODMn), and ammonia nitrogen (NH4+-N) were significantly correlated with TOC in autumn, but only total nitrogen (TN) and transparency (SD) were significant in winter. Spatially, WT, chemical oxygen demand (COD), NH4+-N, TN, and conductivity (Cond) correlated with TOC in the Dan reservoir, but WT, COD, NH4+-N, total phosphorus (TP), and chlorophyll a (Chl.a) were significant in the Han reservoir. The multi-factor GAM model indicated that the environmental factors correlated with TOC concentration were mainly WT, TN, Cond, CODMn, and TP, among which WT and Cond showed a significant linear relationship with TOC concentration (edf = 1, p &lt; 0.05), while TN, CODMn, and TP had a significant nonlinear relationship with TOC concentration (edf &gt; 1, p &lt; 0.05). Comprehensive trophic level index (TLI) and TOC concentration revealed a highly significant correlation (R2 = 0.414, p &lt; 0.001). Therefore, the GAM model could well explain the environmental factors associated with the spatio-temporal dynamics of TOC concentration, providing a reference for the evaluation of water quality and research on the carbon cycle in similar inland reservoirs.

Soil Water Content Shapes Microbial Community Along Gradients of Wetland Degradation on the Tibetan Plateau.

Soil microbes are important components in element cycling and nutrient supply for the development of alpine ecosystems. However, the development of microbial community compositions and networks in the context of alpine wetland degradation is unclear. We applied high-throughput 16S rRNA gene amplicon sequencing to track changes in microbial communities along degradation gradients from typical alpine wetland (W), to wet meadow (WM), to typical meadow (M), to grassland (G), and to desert (D) in the Zoige alpine wetland region on the Tibetan Plateau. Soil water content (SWC) decreased as wetland degradation progressed (79.4 and 9.3% in W and D soils, respectively). Total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) increased in the soils of WM, and then decreased with alpine wetlands degradation from WM to the soils of M, G, and D, respectively. Wetland degradation did not affect microbial community richness and diversity from W soils to WM, M, and G soils, but did affect richness and diversity in D soils. Microbial community structure was strongly affected by wetland degradation, mainly due to changes in SWC, TOC, TN, and TP. SWC was the primary soil physicochemical property influencing microbial community compositions and networks. In wetland degradation areas, Actinobacteriota, Acidobacteriota, Cholorflexi, and Proteovacteria closely interacted in the microbial network. Compared to soils of W, WM, and M, Actinobacteriota played an important role in the microbial co-occurrence network of the G and D soils. This research contributes to our understanding of how microbial community composition and networks change with varied soil properties during degradation of different alpine wetlands.

Analysis of Toc Values of Mixed Sewage Sludge Following the Hydrodynamic Treatment, in Course of Pilot Experiment in the Framework of R&amp;D Ginop Ongoing Project

The primary and secondary stages in wastewater treatment generate a large amount of sewage sludge consisting of 90% water, mineral components, nutrients and also a variety of organic and inorganic contaminants. The contaminants do not degrade completely during these processes, thus an additional degradation is needed to stabilize the sewage sludge. The innovative technology is proposed consisting of hydrodynamic cavitation process along with the addition of Bakony brown coal as adsorbent. Hydrodynamic cavitation is known as an effective tool improving sewage sludge stabilization via aerobic degradation, while adsorbent, besides the adsorption ability, has microbial cells disintegration ability as well, further enhancing the biodegradation process. The changes in total organic carbon (TOC) values of sewage sludge after hydrodynamic treatment for various retention times (0, 5, 10, 15, and 25 minutes) was traced and interpreted.

Ozonation of Amoxicillin and Ciprofloxacin in Model Hospital Wastewater to Increase Biotreatability.

Amoxicillin (AMX) and Ciprofloxacin (CIP) are antibiotics commonly used in human medicine with high environmental toxicity and poor biodegradability. They have been found in various hospital effluents and groundwater, and their environmental impact is still not fully understood. In this work, we investigated the possibility of treating model wastewaters containing the antibiotics AMX and CIP using ozonation, with the addition of H2O2 under various conditions, including different pH values, H2O2, and ozone dosages. The quantification of and treatment efficacy for antibiotic removal were determined via solid phase extraction followed by chromatographic separation by liquid chromatography coupled with tandem triple quadrupole mass spectrometry (LC/MS/MS). This analytical system is quite efficient for the detection of all major antibiotic classes, even if they are present at very low concentrations. The efficiency of ozonation was determined by measuring the TOC (Total Organic Carbon) changes after ozonation of the model wastewater and by measuring the concentration of the two antibiotics. In a sequential activated sludge process of ozone-treated model wastewater, almost complete TOC removal and an overwhelming decrease in antibiotic concentrations (up to 99%) were observed. Ozonation resulted in complete removal of AMX and CIP in less than 30 and 120 min, respectively. The results of this work indicate that ozonation could be a suitable pretreatment method to reduce the toxicity of contaminants (AMX and CIP) and improve the biodegradability of hospital wastewater.