Nitrate-nitrogen Concentrations Research Articles

Formulation and evaluation of the effective microorganisms in sewage treatment.

Effective microorganisms pose a great potential in wastewater treatment. In the present study, effective microorganisms' formulations were developed using different organic substrates that support the growth of more beneficial microorganisms for sewage treatment. Based on the metagenomic analysis and biochemical profile information, the fish waste-based effective microorganisms' formulation was identified as the effective formulation. Metagenomic analysis showed that fish-based effective microorganisms' formulation had the Lactobacillus and Acetobacter groups of bacteria. The dominant groups were Lactobacillus pontis (64.85%), Acetobacter aceti (8.92%), and Lactobacillus reuteri (8.98%). The developed fish waste-based effective microorganisms' formulation was used to treat the sewage water with different concentrations. Effective microorganisms' formulation at 3% showed appreciable results. It recorded a significant reduction in BOD from 389.2 to 117.9mg L-1 and COD from 820.5 to 257.1mg L-1 in 96h. It also significantly decreased the concentration of ammoniacal and nitrate nitrogen, phosphorus, sulphate, and coliforms. Besides, the effective microorganisms' formulation ensured the reduced level of odour from sewage water. Therefore, we can effectively use the effective microorganisms' formulation for sewage water treatment and recycling.

Impact of landscape management and vegetation on water and nutrient runoff from small catchments for over 20 years.

Land cover, vegetation, and landscape management have a large impact on surface water conditions. We analyzed the quantity and quality of surface waters draining from forest catchment with high vegetation and agricultural catchment with low or no vegetation. The following parameters were assessed: specific water runoff, precipitation totals, electrical conductivity in the surface waters, the content of suspended solids, nitrate nitrogen (N-NO3-), and phosphate phosphorus (P-PO43-) in the surface waters. Measurement of the specific water runoff took place over one hydrological year. Measurement of the water quality took place over twenty years and captured changes in the land cover. Hydrological and hydrochemical data from both sub-catchments were compared and statistically analyzed. The results showed that forest landscapes with high vegetation can retain up to twice as much rainwater compared to agricultural landscapes with low vegetation and bare areas. However, in episodes with intense short-term rainfall, forest landscapes can hold even several times more rainwater than landscapes with low vegetation. In dry periods, landscapes with large amounts of high vegetation can retain more water for longer periods than landscapes with low vegetation and bare areas that dry out relatively quickly. The runoff of nutrients and other substances from forest landscapes is much slower due to the high vegetation and thus contributes to the protection of water quality in watercourses. The main findings of this research show that as vegetation increases, the landscape holds more water and other substances, reducing the risk of floods, droughts, and water pollution. Other research results show that even a small change in vegetation cover has a significant impact on the water runoff and quality of surface waters. The work emphasizes the importance of supporting vegetation in temperate zone landscapes in landscape planning and management.

Influence of Varied Carbon Sources and Carbon-Nitrogen Ratio on Microbial Community in a Biofloc-Based Culture System and Their Effects on Growth Performance, Proximate Composition, Hematology and Oxidative Stress in Nile Tilapia

This study investigates the influence of varied carbon sources and carbon-nitrogen ratio on microbial community in a biofloc-based culture system and their effects on growth performance, proximate composition, hematology, and oxidative stress in Nile tilapia. The experiment involved three different carbon-nitrogen ratios (10:1, 15:1, 20:1) and two carbohydrate sources (molasses: ML-10, ML-15, ML-20, starch: S-10, S-15, and S-20) with three replicates each. A diet containing 25% crude protein was fed to fish in 18 experimental units for 120 days. Carbohydrate supplementation significantly increased the total heterotrophic bacterial (THB) count from C/N10 to C/N20 while decreasing pH, total ammonia nitrogen, and nitrate nitrogen contents. In addition, growth was considerably greater in the ML-10 and ML-15 groups compared to the C/N20 group. Increasing the C/N ratio increased body protein and ash, decreased lipid contents, and increased the activities of lysozyme, SOD, CAT, and GPx. Finally, the C/N10 and C/N15 groups showed significantly lower GLU and COR concentrations in biofloc compared to the C/N20 group. Furthermore, increasing the C/N ratio up to 15 resulted in improved outcomes in terms of Hb, WBCs, RBCs, and Ht content. Overall, the utilization of the C/N15 group resulted in suitable growth, proximate composition, and immunity in Nile tilapia.

Dynamics of the content of mineral elements and effective fertility of alluvial meadow soil in vegetable crop rotation

In vegetable crop rotation with different fertilization systems of vegetable crops, the dynamics of the content of mineral elements of plant nutrition was determined, effective soil fertility was evaluated in comparison with potential under experimental conditions, and the most effective fertilizer system was identified not only to obtain the highest yields, but also to preserve and reproduce the potential fertility of alluvial meadow soil. The study was conducted in 2015–2019 in the Ramensky district of the Moscow region on the alluvial meadow medium loamy soil of the central floodplain of the Moscow River. The seasonal dynamics of the content of 3 elements of plant mineral nutrition (nitrate nitrogen, mobile phosphorus and potassium) in the carrot – beet – cabbage crop rotation was studied, using 3 main fertilization systems for vegetable crops (mineral, organic, organo-mineral). It was found that the maximum content of nitrate nitrogen (on average in crop rotation 47.4 mg/kg) and mobile potassium (on average 156 mg/kg) occurred in the third decade of June. The content of mobile phosphorus in the soil was high (200 mg/kg) at all accounting periods. A close correlation was determined between the yield of root crops and cabbage with the average content of nitrate nitrogen in the soil during the growing season (r = 0.735–0.934), mobile phosphorus (r = 0.539–0.972) and potassium (r = 0.532–0.976). The effective soil fertility of the site under 3 crops per crop rotation had the following characteristics: when using a mineral fertilizer system, the content of nitrate nitrogen was 21.3, organic – 10.1, organo-mineral – 22.1 mg/kg, the content of mobile phosphorus when using a mineral system – 40.4, organic – 34.1, organo-mineral – 47.9 mg/kg, the content of mobile potassium is 44.4, 20.6, 50.8 mg/kg, respectively. It was found that under crops of carrots and beets, the potential fertility of the soil during crop rotation was reproduced with the use of mineral (recommended dose of NPK) and organo-mineral fertilization systems of these crops, and the yield of carrots (67–69 t/ha) and beets (67–68 t/ ha) under these systems was high, more than expected estimated 60 t/ha. Under cabbage, late soil depletion also did not occur when using the recommended mineral and organo-mineral fertilizer systems, yields of 78 and 81 t/ha were close to the expected estimated yield of 80 t/ha. At the same time, the organo-mineral system had an advantage: during crop rotation, it retained 13% more nitrate nitrogen in the soil, 8% more mobile phosphorus and 40% more mobile potassium than the mineral one. One and a half and double doses of mineral fertilizers for late cabbage led to a significant increase in its yield (85–90 t/ha), but at the same time a significant part of nitrogen (on average for the season 33–41 mg/kg) was irretrievably lost in the soil.

The influence of degradation processes on enzymatic activity and the content of forms of mineral nitrogen in agricultural soils

The purpose of the work was to study the concentration of various forms of mineral nitrogen and nitrogen cycle enzymes in farmland soils. The objectives of the research included studying the content of ammonium and nitrate forms of nitrogen, as well as the activity of urease and nitrate reductase in soils of farmland on the territory of the Donetsk People's Republic (DPR). To study the soils of agricultural lands, model sites located in the southern part of the Shakhtersky district of the DPR were selected and represented by moderately washed-out chernozems with low, low and medium humus. The control was an area with steppe vegetation (ordinary chernozem, thick, with medium humus content). The results of the researches allow us to draw conclusions about the development of degradation processes in a number of model sites and their impact on the content of ammonium and nitrate nitrogen in agricultural soils. Growing crops removing substantial amount of mineral nutrients, the slope of the sites surface, and the duration of cultivation of grain crops in the same sites lead to a significant decrease in the concentration of ammonium and nitrate nitrogen. Thus, the most significant decrease in the concentration of nitrogen of ammonium compounds (by 77–82%) was recorded in model slope areas under maize and sunflower. Analysis of the data showed that exchange ammonium is confined to the underlying genetic horizons. The minimum concentration of nitrates in the arable horizon was recorded under the joint influence of such unfavorable factors as: unreasonable layout of fields along the relief elements; violation of crop rotation conditions; use of precursor crops with a significant level of removal of nutrients (wheat, maize). When studying the activity of urease, it was found that a low number of soil microorganisms associated with the cultivation of maize and sunflower, as well as with the development of degradation processes of various genesis, led to the suppression of the functioning of the urease of soils in model areas. The maximum urease activity was observed in areas under winter wheat and amounted to 68–72% in relation to the control indicators. As a result of studies of nitrate reductase activity, a decrease in its values was also found in areas used to grow crops that form a large phytomass (maize and sunflower).

The Nitrogen Preference of Cactus Pear (Opuntia ficus-indica): A Sand Culture Snapshot.

Cactus pear (Opuntia-ficus indica (L.) Mill.) is an important agricultural crassulacean acid metabolism (CAM) species used as a source of food, forage, fodder, and secondary products and as a biofuel feedstock. However, the preferred source of nitrogen for this species, whether it be nitrate (NO3-), ammonium (NH4+), or a combination of both, is not well understood. To investigate the nitrate and ammonium preference of cactus pear, we grew cladodes in sand culture with deionized water as a control or with a cross-factorial set of nutrient solutions of 0.0, 2.5, 5.0, and 10.0 mmol of nitrate and/or ammonium for one month. We then assessed a set of physiological parameters including cladode growth, relative water content, chlorophyll, tissue acidity, soluble sugars, starch, nitrate, ammonium, glyoxylic acid, nitrate reductase activity, and nitrogen and carbon content. We found significant differences in all measured parameters except for cladode length, relative water content, and carbon content. Cladodes provided with only deionized water produced no new cladodes and showed decreased soluble sugar content, increased starch content, and increased tissue acidity. We also determined the relative steady-state transcript abundance of genes that encode enzymes involved in N metabolism and CAM. Compared with control cladodes, nutrient-supplied cladodes generally showed increased or variable steady-state mRNA expression of selected CAM-related genes and nitrogen-metabolism-related genes. Our results suggest that O. ficus-indica prefers fertilizers containing either equal concentrations nitrate and ammonium or more nitrate than ammonium.

Simulation of nitrate nitrogen concentrations and DOM characteristics in groundwater from Southwest China's Karst Wetlands using an improved GMS model.

Existing models often face limitations in the understanding and prediction of nitrate nitrogen (NO3--N) concentrations in karst groundwater. In this study, to tackle this issue, a Gaussian function model was coupled with the Groundwater Modeling System (GMS) to simulate NO3--N concentration changes in the southwest karst wetland of China. Additionally, fluorescence spectroscopy was employed to measure dissolved organic matter (DOM) components in the groundwater, providing insights into their variation and influence on NO3--N dynamics. The results demonstrated that coupling the Gaussian curve fitting method with the GMS model accurately simulated NO3--N concentration changes in the study area. The simulation revealed lower NO3--N levels in the northern region, with higher concentrations in the central area, peaking at 20.73mg/L at lower elevations. NO3--N was primarily distributed in the southwestern region and upper Mudong Lake, exhibiting a diffusion trend from west to east. DOM analysis indicated significant autochthonous contributions, particularly microbial metabolic by-products. The total fluorescence intensity and DOM components increased downstream, with the lowest values at the source and the highest values at river confluences. The humification index (HIX) was correlated with NO3--N concentrations, where lower NO3--N levels corresponded to lower HIX values, and higher NO3--N levels corresponded to higher HIX values. In conclusion, this study provides valuable insights into NO3--N prediction in groundwater and the role of DOM, offering a reference for groundwater protection in the southwest China karst basin.

Growth, Quality, and Nitrogen Metabolism of Medicago sativa Under Continuous Light from Red-Blue-Green LEDs Responded Better to High Nitrogen Concentrations than Under Red-Blue LEDs.

Alfalfa is a widely grown forage with a high crude protein content. Clarifying the interactions between light quality and nitrogen level on yield and nitrogen metabolism can purposely improve alfalfa productivity in plant factories with artificial light (PFAL). In this study, the growth, quality, and nitrogen metabolism of alfalfa grown in PFAL were investigated using three nitrate-nitrogen concentrations (10, 15, and 20 mM, labeled as N10, N15, and N20) and continuous light (CL) with two light qualities (red-blue and red-blue-green light, labeled as RB-C and RBG-C). The results showed that the adaptation performance of alfalfa to nitrogen concentrations differed under red-blue and red-blue-green CL. Plant height, stem diameter, leaf area, yield, Chl a + b, Chl a, Chl b, crude protein contents, and NiR activity under the RB-CN15 treatment were significantly higher than RB-CN10 and RB-CN20 treatments. The RB-CN20 treatment showed morphological damage, such as plant dwarfing and leaf chlorosis, and physiological damage, including the accumulation of proline, H2O2, and MDA. However, the difference was that under red-blue-green CL, the leaf area, yield, and Chl a + b, carotenoid, nitrate, and glutamate contents under RBG-CN20 treatment were significantly higher than in the RBG-CN10 and RBG-CN15 treatments. Meanwhile, the contents of soluble sugar, starch, and cysteine were significantly lower. However, the crude protein content reached 21.15 mg·g-1. The fresh yield, dry yield, stomatal conductance, leaf area, plant height, stem diameter, crude protein, GS, and free amino acids of alfalfa were positively correlated with increased green light. In addition, with the increase in nitrogen concentration, photosynthetic capacity, NiR, and GOGAT activities increased, promoting growth and improving feeding value. The growth, yield, photosynthetic pigments, carbon, nitrogen substances, and enzyme activities of alfalfa were significantly affected by the interaction between nitrogen concentration and light quality, whereas leaf/stem ratio and DPPH had no effect. In conclusion, RB-CN15 and RBG-CN20 are suitable for the production of alfalfa in PFAL, and green light can increase the threshold for the nitrogen concentration adaptation of alfalfa.

Anion exchange resin installation in reducing nitrate nitrogen and phosphate phosphorus concentrations: The backwater of Turawa reservoir, Poland case study

Anion exchange resin installation in reducing nitrate nitrogen and phosphate phosphorus concentrations: The backwater of Turawa reservoir, Poland case study

Black Soil Quality After 19 Years of Continuous Conservation Tillage

Conservation tillage is a practice adopted worldwide to prevent soil degradation. Although there have been many studies on the impact of conservation tillage on soil quality, most studies on cultivated land in the black soil region of Northeast China are based on the physical and chemical indicators of soil. In addition, the experiment time is generally short, so there is a lack of information about long-term conservation tillage from the perspective of the physical, chemical, and biological integration of soil. A comparative analysis of the physical, chemical, and biological characteristics of soil was conducted under no-till (NT) with straw mulching and conventional tillage (CT) treatments after 19 years of field experiments. By using membership functions to normalize and render all the indicators dimensionless, and calculating the weight of each indicator through principal component analysis, the comprehensive index of soil quality can be calculated as a weighted summation. The results indicate that NT had no significant effect on soil bulk density at a soil depth of 0–20 cm. NT increased the field water-holding capacity of the 0–5 cm layer, reduced the total porosity of the 5–10 cm soil layer, and decreased the non-capillary porosity of the 0–20 cm soil layer. Compared to CT, NT significantly increased the organic carbon content of the soil in the 0–5 cm layer, comprehensively improved the total nutrient content of the soil, and significantly increased the contents of ammonium nitrogen, nitrate-nitrogen, and available phosphorus in the soil. It also significantly improved the total phosphorus content in the 5–20 cm soil layer. NT improved the microbial carbon and nitrogen content of the soil, significantly enhanced the microbial nitrogen content in the 0–5 and 5–10 cm soil layers, and reduced the bacterial species diversity in the 5–10 cm soil layer. However, the soil enzyme activities showed no significant differences between different treatments. Under the NT treatment, the evaluation of soil quality indicators, such as mean weight diameter, field water-holding capacity, non-capillary porosity, microbial biomass nitrogen, total nutrients, and available nutrients, was relatively successful. Based on the weight calculation, the organic carbon, catalase activity, fungal richness, and bacterial diversity indicators are the most important of the 22 soil quality indicators. In terms of the comprehensive index of soil fertility quality, NT increased the soil quality comprehensive index by 34.2% compared to CT. Long-term conservation tillage improved the physical, chemical, and biological properties of the soil, which significantly enhanced the quality of the black soil.

The Application of Straw Return with Nitrogen Fertilizer Increases Rice Yield in Saline–Sodic Soils by Regulating Rice Organ Ion Concentrations and Soil Leaching Parameters

Soil salinization is a severe environmental problem that restricts crop productivity. Straw amendment could increase the fertility of saline–sodic soils by improving soil physical properties and carbon sequestration; however, the chemical mechanism of saline soil improvement via straw reclamation is not clear. This study aimed to investigate the effects of straw return with nitrogen fertilizer on soil leaching characteristics, rice organ ion concentrations, and yield. Therefore, a soil column leaching experiment was conducted in 2021 in Baicheng, Jilin Province, using two straw application rate treatments (0 and 8 t hm−2) and three nitrogen application rate treatments (0, 180, and 360 kg hm−2). The results revealed the following: 1. The combination of straw return and nitrogen fertilizer significantly increased the soil leachate volume, leachate pH, Na+ concentration, and Na+/K+ ratio, thereby reducing Na+ stress on rice; 2. The application of nitrogen fertilizer during straw return effectively minimized soil nitrogen loss by lowering the ammonium and nitrate nitrogen concentrations in the soil leachate; 3. This combination also reduced plant Na+ concentrations while increasing plant K+ concentrations, thus improving the Na+/K+ ratio in the plants; 4. Straw return with nitrogen fertilizer significantly enhanced rice yield, which increased with higher nitrogen application rates. In summary, the integration of straw return with nitrogen fertilizer not only regulates rice salinity tolerance but also boosts rice yield, presenting a novel approach for improving saline–sodic soils.

Effect of Nutrient Management During the Nursery Period on the Growth, Tissue Nutrient Content, and Flowering Characteristics of Hydroponic Strawberry in 2022

The objective of a strawberry nursery is to produce numerous runners and improve the quality of the runner plants, ensuring their uniformity and health. About 80% of the strawberry nurseries in Wanju-gun, Republic of Korea, are cultivated by the growers themselves, which results in variations in the cultivation techniques. Different methods are employed to reduce the nitrogen levels to promote floral bud initiation in the later nursery stage, and these methods vary between farms. This study was conducted on the ‘Sulhyang’ cultivar (Fragaria × ananassa Dutch. cv. Sulhyang) to measure the nutrient content in runner plants obtained from eight growers using various cultivation methods, supply EC levels, nutrient solution termination times, etc., and to correlate the nutrient levels with floral bud initiation during the nursery period. Four investigations were conducted at 15-day intervals from Julian day 214 (2 August) to Julian day 259 (16 September) in 2022, focusing on nutrient management during the nursery period, runner plant growth, petiole nitrate nitrogen content (NO3-N), and soluble solid content (SSC). The NO3-N content decreased, and the SSC/NO3-N ratio increased near the transplanting period, as assessed using a rapid inorganic nutrient diagnostic device. The proportion of runner plants that had advanced to stage 3 or above in floral bud initiation was investigated using a stereomicroscope. As a result, differences in the percentage of floral bud initiation were confirmed based on the varying nutrient management among the farms. In this study, on Julian day 243 (31 August 2022), there was a strong negative correlation (r = −0.86, r2 = 0.73) between the NO3-N content in the runner plants and the percentage of floral bud initiation. These results emphasize the importance of nutrient management during the nursery period, especially for strawberry self-propagating growers, and demonstrate a strong correlation between nutrient content and floral bud initiation in strawberries.

Root morphology, nitrogen metabolism and amino acid metabolism in soybean under low phosphorus stress.

Phosphorus deficiency is a major influence on growth and development of soybean. Therefore, improving phosphorus utilization efficiency in soybean is a research priority for the soybean community. In this experiment, Liaodou 13 (high phosphorus utilization: HPE) and Tiefeng 3 (low phosphorus utilization: LPE) were used as test varieties. We investigated changes in root morphology, amino acid content, and content of key substances of the nitrogen metabolic pathway with normal phosphorus (0.5 mM) and low phosphorus (0.005 mM) treatments. The results showed that the root length, root surface area and number of lateral roots of HPE roots were higher than those of LPE roots under normal and low phosphorus conditions. The contents of different types of amino acids showed different trends in two varieties. The HPE showed small change in the content of total hydrolyzed amino acids under the low phosphorus condition when compared to the normal phosphorus treatment by a 6.67% decrease, on the contrary LPE showed a drastic decrease by 20.36%. However, HPE exhibited similar decreasing trends in the contents of hydrolyzed and free aspartic acid with the low phosphorus treatment. Moreover, the contents of free histidine and valine in LPE were significantly increased by 657.84% and 149.29% respectively, in contrast to significant decreases in HPE. In aspects of major nutrient elements, the contents of phosphorus, total nitrogen and ammonia nitrogen in both HPE and LPE varieties decreased to dramatic levels. However, the nitrate nitrogen content significantly increased 78.51% for HPE and 65.12% for LPE. Compare to the normal condition, the GOGAT activity in HPE decreased by 5.18% but increased by 33.10% in LPE. Compare to the normal condition, the GS activity in HPE increased by 7.26% but decreased by 21.72% in LPE under phosphorus deficiency. In summary, the phosphorus-efficient soybean variety HPE exhibited superior tolerance to low phosphorus deficiency through advantageous root morphology, phosphorus uptake and transfer capability, and balanced amino acid metabolism and nitrogen metabolism pathways.

The spatial scale and threshold effects of the relationship between landscape metrics and water quality in the Hutuo River Basin

The impact of landscape patterns on river water quality has been widely studied; however, it remains unclear which spatial scale has the greatest impact on water quality. Here, we analyzed the spatial scale and threshold impacts of the link between landscape metrics and water quality in a large-scale basin using the random forest (RF) model and nonparametric change point analysis (nCPA) method. The concentrations of nitrate nitrogen (NO3−-N) and total nitrogen (TN) were comparatively high in winter and relatively low during spring and summer, whereas the total phosphorus (TP) concentrations were comparatively low during winter and summer and relatively high during spring. The R2 values of the RF models at the sub-basin scale were generally higher than those at the riparian zone scale. Moreover, the R2 of water quality modelling at the riparian zone scale demonstrated a declining tendency from a riparian zone 30 m–210 m wide in the majority of seasons. This shows that landscape metrics at the subbasin scale provide a better explanation for the variability in water quality than those at the riparian zone scale in the Hutuo River Basin. The results of the RF model indicated that landscape metrics of landscape configuration were more important in determining water quality during winter, whereas landscape metrics of landscape composition or physiography were more important in determining water quality during summer. Furthermore, several abrupt thresholds were estimated by nCPA; for example, the summertime slope abrupt threshold was 10.79° in the relationship between the slope and NO3−-N. This study contributes to the understanding of the debate regarding the scale effects of landscape patterns on water quality, emphasizing the significance of the basin area and offering managers valuable insights into the control of non-point source pollution.

Effects of Rubber Plantation Restoration in National Parks on Plant Diversity and Soil Chemical Properties

Plantations left for natural succession play a significant role in Tropical Rainforest National Parks. Studying the succession and restoration of plantations is crucial for achieving a park’s authenticity and integrity, as well as for maximizing its ecological functions. However, the changes in vegetation and soil properties during the natural succession of these decommissioned plantations remain unclear. In this study, we examined rubber [(Hevea brasiliensis (Willd. Ex A. Juss.) Muell. Arg] plantations in the Yinggeling area of the National Park of Hainan Tropical Rainforest. We used community surveys, field sampling, and soil property analyses to investigate the species richness, diversity, and species composition of the aboveground plant communities during three succession periods of rubber plantations left for natural succession, including 0 years (ZY), 3 years (TY), and 7 years (SY). The soil pH, total organic carbon, total nitrogen, total phosphorus, available phosphorus, nitrate nitrogen, ammonium nitrogen, and total potassium contents in the three succession periods were analyzed. These results showed that there were 92 species of understory plants in the decommissioned rubber plantations, belonging to 72 genera in 39 families. The highest number of understory plant species was found in the plantations with 3 years of natural succession, totaling 66 species from 49 genera in 29 families. The number of families, genera, and species followed the pattern TY > SY > ZY. The Margalef richness index (F), Simpson index (D), and Shannon–Wiener index (H) of understory plants in the 0-year succession plantations were significantly lower than those in the 3-year and 7-year succession plantations. However, there was no significant difference in the Pielou (EH) index among the succession gradients. The soil pH, nitrate nitrogen (NO3--N), and available phosphorus (AP) in the 0-year succession plantations were significantly higher than those in the 3-year and 7-year succession plantations. There were no significant differences in soil total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and ammonium nitrogen (NH4+-N) across the three succession gradients. The soil total potassium (TK) in the 3-year succession plantations was significantly higher than that in the 0-year and 7-year succession plantations. Soil available phosphorus and total phosphorus (TP) were positively correlated with the Margalef index, Simpson index, Shannon–Wiener index, and Pielou index. The recovery rate of understory vegetation in decommissioned rubber plantations was faster than that of the soil. This indicates that the construction of the National Park of Hainan Tropical Rainforest has significantly promoted the recovery of the number of plant species and plant species diversity that have been left from rubber plantation operations. These findings not only deepen our understanding of soil property changes during the vegetation succession of artificial forests, particularly rubber plantations, but they also hold significant implications for guiding tropical forest management and sustainable development.

Occurrence, migration, and assessment of human health and ecological risks of PFASs and EDCs in groundwater of Northeast China

Northeast China as an important base of grain production in China, has been suffering from potential groundwater pollution due to the excessive and prolonged application of fertilizers and pesticides. However, exploration of emerging contaminants pollution in groundwater and assessment of human health and ecological risks caused by large-scale agricultural activities have been relatively scarce. This study collected groundwater samples from typical agricultural areas in Northeast China to investigate the extent of contamination by nitrate, per- and polyfluoroalkyl substances (PFASs) and endocrine-disrupting compounds (EDCs), and then compared the levels of these pollutants with those in other regions of China. Groundwater nitrate pollution caused by strong agricultural activity is widespread in Northeast China, with nitrate-nitrogen (NO3N) concentrations exceeding 10 mg/L in as many as 40.3 % of 429 samples. 8 types of PFASs (3.7–7.1 ng/L) and 11 types of EDCs (18,114.0–62,029.8 ng/L) were detected in the collected groundwater samples. Using the Risk Quotient (RQ) method, this study assessed ecological risk and found that the risk level of perfluorooctane sulfonate (PFOS) was higher than that of other PFASs. The groundwater EDCs risks in Northeast China was higher compared to other regions in China, with dibutyl phthalate (DBP), Di-(2-ethylhexyl) phthalate (DEHP), Bisphenol A (BPA) having high ecological risk levels. Nitrate, PFASs and EDCs have been detected in deep groundwater (70–100 m depth), indicating that the deeper aquifers could be significantly threatened by pollutants due to human activities. Fertilizers, pesticides, domestic wastewater, and industrial discharges are major sources of groundwater pollutants in the agricultural regions. Industrial-sourced EDCs were widely detected in groundwater of agricultural area, suggesting that the transport of these pollutants is very active in groundwater system. Groundwater monitoring and pollution prevention are extremely urgent, especially for emerging contaminants. This study can provide important warnings and water resource management references for other agricultural areas affected by intensively agricultural activities in the world.

Effects of Rice Root Development and Rhizosphere Soil on Methane Emission in Paddy Fields.

Paddy fields are important anthropogenic emission sources of methane (CH4). However, it is not clear how rice root development and rhizosphere soil properties affect CH4 emissions. Therefore, we selected rice varieties with similar growth periods but different root traits in the local area. We measured CH4 emission fluxes, cumulative CH4 emissions, root dry weight, root length, and the dissolved organic carbon (DOC), microbial biomass carbon (MBC), redox potential (Eh), ammonium nitrogen (NH4+-N), and nitrate nitrogen (NO3--N) contents in rhizosphere soil. Methanogens and methanotrophs are crucial factors influencing CH4 emissions; thus, their abundance and community composition were also assessed. The result showed that CH4 fluxes of each rice variety reached the peak at tillering stage and jointing-booting stage. The CH4 emissions in tillering stage were the largest in each growth period. CH4 emissions had negative correlations with root length, root dry weight, Eh NO3--N, methanotroph abundance, and the pmoA/mcrA ratio, and positive correlations with NH4+-N, MBC, DOC, and methanogen abundance. Path analysis confirmed methanogens and methanotrophs as direct influences on CH4 emissions. Root development and rhizosphere soil properties affect CH4 emissions indirectly through these microbes. This study suggests that choosing rice varieties with good root systems and managing the rhizosphere soil can effectively reduce CH4 emissions.

RESEARCH OF THE EFFICIENCY OF ORGANIC MATTER REMOVALFROM WATER USING SYNTHETIC ZEOLITE

The paper investigated the effectiveness of using synthetic zeolite as an adsorbent for the removal of organic matter from water. Characterization of zeolite was performed using advanced testing methods: XRD, FTIR, BET and SEM/EDS. Raw water was analyzed for physicochemical characteristics before treatment (turbidity, color, pH,conductivity, content of organic matter, ammonia, nitrate and nitrite nitrogen, iron, manganese and chloride) and after treatment with an adsorbent (content of organic matter). Research on the efficiency of adsorption was carried out under the conditions of water temperature 25°C, individual doses of zeolite of 1, 2 and 4 g/L, mixing 200 rpm and adsorption time 60 minutes. The obtained results showed that by applying synthetic zeolite in a dose of 1 g/L, it is possible to achieve the removal of organic matter of 71.2%, while increasement of that dose up to four times has an insignificant effect on the adsorption efficiency. KEYWORDS:synthetic zeolite; organic matter removal

Pennycress reduces potential for nutrient loss in Illinois.

Nutrient export of nitrogen and phosphorus from row crop agriculture in the Upper US Midwest is a threat to the structure and function of aquatic systems. To meet Environmental Protection Agency (EPA) nutrient reduction goals, the Upper US Midwest needs to implement strategies to reduce nutrient export from agriculture. Studies demonstrate the potential of cover crops to reduce the export of nitrate-nitrogen from the Upper US Midwest. We investigated the impact of the economically viable winter cash cover crop pennycress (Thlaspi arvense) on soil porewater nutrients and soil nutrients and characteristics. We used nine replicated 0.8ha plots (n=3 per treatment) at a production scale research farm over 4 years with pennycress and fertilized pennycress (56kg ha-1 of urea) treatments compared to a fallow reference. Over the study period, soil porewater nitrate-nitrogen was reduced by 53% in pennycress plots and 34% in fertilized pennycress plots relative to the fallow reference at a depth of 45cm. Early season establishment was crucial in providing nutrient reduction potential. In 2021, poor pennycress establishment resulted in porewater nitrate-nitrogen concentrations 141% higher than in 2022 with excellent pennycress establishment. Following pennycress termination, soil nitrate-nitrogen was reduced by 24% in pennycress and 26% in fertilized pennycress compared to the fallow reference in the top 30cm of soil. Following 4 years of pennycress planting, nitrate-nitrogen concentrations were significantly reduced with no broad effect on soil characteristics. We conclude that the novel pennycress crop has potential to reduce nutrient loss from row crop agriculture in the Upper US Midwest.

Influence of rubber particle inputs on nitrogen removal efficiency of bioretention systems.

Bioretention systems effectively capture rubber particles and other microplastics in stormwater runoff. However, it is uncertain whether long-term particle accumulation affects pollutant removal efficacy. This study investigated the impact of various concentrations of ethylene-propylene-diene-monomer (EPDM) particles (0, 50, 100, and 400 mg/L) on bioretention system nitrogen removal performance. The input of EPDM during short-duration (2 h) rainfall favored the removal of nitrogen, and the total nitrogen effluent concentration of the bioretention system with EPDM was reduced by 0.59-1.52 mg/L compared with that of the system without EPDM. In addition, the input of EPDM reduced the negative effects of drought. During long-duration (24 h) rainfall, higher concentrations of EPDM led to lower nitrate-nitrogen concentrations in the effluent. The bioretention system with EPDM required less time for nitrate-nitrogen removal to reach 50% than that without EPDM input. Microbial community analysis showed that EPDM increased the relative total abundance of denitrifying bacteria (such as Dechloromonas, Zoogloea, Ramlibacter, and Aeromonas) by 7.25-10.26%, which improved the denitrification capacity of the system.