Search

Understanding the patterns of greenhouse gas emissions and the changes in pollution load in terrestrial freshwater systems is crucial for accurately assessing the global carbon cycle and overall greenhouse gas emissions. However, current research often focuses on wetlands and rivers, with few studies on agricultural drainage ditches, which are an important part of the agricultural ecosystem. Investigating the greenhouse gas emission patterns and pollution load changes in agricultural drainage ditches can help accurately assess the greenhouse effect of agricultural systems and improve fertilization measures in farmlands. This study explored the effects of nitrogen input and aeration on the pollution load and greenhouse gas emission processes in paddy field drainage ditches. The results showed that aeration significantly reduced the concentration of ammonium nitrogen (NH4+) in the water, decreased the emissions of nitrous oxide (N2O) and methane (CH4), and slightly increased the emission of carbon dioxide (CO2), resulting in an overall reduction of the global warming potential (GWP) by 34.02%. Nitrogen input significantly increased the concentration of ammonium nitrogen in the water, slightly reduced the emissions of N2O and CH4, and increased the CO2 emissions by 46.60%, thereby increasing the GWP by 15.24%. The drainage ditches reduced the pollution load in both the water and sediment, with the overall GWP downstream being 9.34% lower than upstream. [ABSTRACT FROM AUTHOR]

The removal of nitrogen from water is a consequence of the synergistic action of plant uptake, sediment sorption, and microbial decomposition. However, there is a lack of long-term experimental studies on the effects of each component in the process of nitrogen removal. In this study, we investigated the effect of sediment, plants, and microorganisms on nitrogen removal by setting up three systems: water–sterilized sediment, water–sediment, and water–sediment–plant. The nitrogen removal effect followed the following rank order of effectiveness: the "water–sediment–plant" system > the "water–sediment" system > the "water–sterilized sediment" system. The ditch sediment had a strong enrichment effect for nitrogen. In addition, the migration rate of nitrogen in the sediment with different depths was different. The ammonia-nitrogen migration rate in the sediment showed an increasing trend with time and depth. The nitrate-nitrogen migration process in the sediment showed a trend of enrichment toward the middle layer (15.0–25.0 cm). Aquatic plants and microorganisms can promote the removal of nitrogen in water, with the average purification rates of 13.92% and 19.92%, respectively. [ABSTRACT FROM AUTHOR]

Water and nitrogen losses from farmland during the snowmelt process play a vital role in water and nitrogen management in cold regions. To explore the mechanisms and factors contributing to water and nitrogen loss from different sloping farmlands during the snowmelt period, field experiments were conducted under two slope treatments (8° and 15°), two soil water content (SWC) treatments, and two snow water equivalent (SWE) (5 mm and 10 mm) treatments in a seasonal freezing agricultural watershed of Northeast China. The results showed that during the snowmelt process, SWE was the most important factor affecting water and nitrogen production through the surface and total runoff of the sloping farmland, followed by the slope. The water and nitrogen yield in the high snow (HS) treatments ranged from 1.76 to 8.15 and 1.65 to 12.62 times higher than those in the low snow (LS) treatments. The generation of nitrogen was advanced compared with that of water induced by the preferential production of nitrogen. A higher slope promoted this preferential production function of nitrogen. Enhanced infiltration combined with the preferential yield of nitrogen resulted in a greatly decreased yield of water and nitrogen in the gentle slope and LS (GS_LS) treatments. These findings are valuable for accurately describing the water and nitrogen cycling in seasonally freezing sloping farmland. [ABSTRACT FROM AUTHOR]

This study develops a coupled model of chemical clogging and permeability coefficient of geotextile envelope. Based on the distribution characteristics of crystal precipitates on geotextile envelope and their influence on the permeability coefficient, a permeability coefficient model of an actual geotextile envelope that considers the overlapping effect is developed. Then, the densification effects of geosynthetic fiber hypothesis and the filter cake effect hypothesis are proposed to simulate the processes of increasing fiber diameter after crystal precipitation and the accumulation of crystal precipitates on the surface of geotextile envelope. The crystal precipitation module and permeability coefficient module are coupled, and their experimental values are used to confirm the availability of the model. Results indicate the satisfactory performance of the model. In addition, the parameter sensitivity analysis and trend prediction show that the saturation index SI and solution flow rate V are the main factors that affect the chemical clogging and permeability of geotextile envelope. When the solution conditions are not considered, the sensitivity of geotextile envelope parameter d f increased with the amount of precipitation in crystal precipitation. When the pores of the geotextile envelope are completely clogged, the permeability coefficient of the geotextile envelope will drop sharply, then decline slowly. • A coupled model for chemical clogging and permeability coefficient of geotextile envelope is developed. • The densification effect of geosynthetic fiber and the filter cake effect are proposed to generalize chemical clogging. • The sensitivity of geotextile envelope parameter d f increased with the amount of precipitation. [ABSTRACT FROM AUTHOR]

Nitrogen is an indispensable and limiting element for plant and microbial growth. To investigate the combined effects of salinity and freezing–thawing (FT) processes on soil inorganic nitrogen (SIN) transformation in seasonally freezing salinized farmland, laboratory incubation experiments were conducted under five soil salt content (SSC) treatments (0.08%, 0.25%, 0.35%, 0.50%, and 0.70%), four FT temperature treatments (C (5 °C), FT (−5 + 5 °C), FT (−10 + 5 °C), and FT (−15 + 5 °C)), and two soil water content (SWC) treatments (40% and 80% of maximum water holding capacity (WHC)). Ammonium (NH4+-N) and nitrate (NO3−-N) nitrogen were monitored at the first, second, fifth, and eighth incubation days. The FT processes increased relative NH4+-N content by 13%, 39%, and 77% with the decreasing of freezing temperature from −5 °C to −15 °C compared with C (5 °C) treatments, respectively. FT (−5 + 5 °C) and FT (−15 + 5 °C) treatments decreased the relative NO3--N contents by 4% and 6% compared with C (5 °C) treatments, respectively. Under FT treatments, the increment of relative NH4+-N content was higher in low-SSC treatments and lower in high-SSC treatments. The relationship between relative NO3–-N content and SSC gradually changed from a decrease in C (5 °C) to an increase in FT (−15+5 °C) treatments. SWC decreased NH4+-N content in high-SSC and low-freezing temperature treatments (SSC × freezing temperature < −2.5%· °C), while NH4+-N increased in low-SSC and unfrozen treatments. The variations of SIN/Rmin (nitrogen mineralization rate) were mostly affected by NO3–-N/Rnit (net nitrification rate) and NH4+-N/Ra (net ammonification rate) in C (5 °C) and FT treatments, respectively. Overall, the results suggested that enhanced salinity inhibited the effects of freezing temperature on NH4+-N and NO3−-N formation, respectively. The increase in SWC weakened the NH4+-N formation induced by the decrease in freezing temperature, and this function increased with the increase in salinity. [ABSTRACT FROM AUTHOR]

The geometric structure of corrugated plastic pipes affects performance in agricultural subsurface drainage systems. To explore the influence of pipe geometry on flow field characteristics and the characterization of water movements, we developed a three-dimensional (3D) steady-state subsurface drainage model based on computational fluid dynamics (CFD). An analysis of the CFD and sand tank results indicated that the proposed model can accurately simulate the subsurface drainage process (R2 = 0.99). The corrugation structure parameters of the drainpipe, including the outside diameter, corrugation valley width and corrugation height, were taken as the objects for this study, and the influence of corrugation parameters on drainage discharge was orthogonally analysed. During drainage, the soil water initially collects in the corrugation valley and then approximately ninety percent of the water flows into the pipe through the bottom perforations; increasing the contact face area between the corrugation valley and soil can increase the flow rate of the drainpipe and the water table height above the pipe, which decreases the intersection position of the pipe and water table. The results of the analysis of the range and variance of the orthogonal experiment showed that the order of the primary and secondary factors influencing the drainage discharge was the outside diameter, corrugation valley width and corrugation height, with the outside diameter being most critical influencing factor. [ABSTRACT FROM AUTHOR]

Human activities input a large amount of carbon and nitrogen nutrients into water, resulting in inland freshwater becoming an important source of greenhouse gas (GHG) emissions. Agricultural drainage ditches are the main transport route of non-point source pollution. Understanding the rules for how greenhouse gas emissions from drainage ditches impact the environment can help to accurately estimate the greenhouse effect of agricultural systems. However, current research mainly focuses on the effect of different measures on the migration and transformation process of pollutants in drainage ditches. The process of greenhouse gas emissions when the non-point source of pollution is transported by drainage ditches is still unclear. In this study, the influence of aeration on the pollution load and GHG emission process of a drainage ditch in a paddy field was explored. The following conclusions were drawn: Aeration reduced the content of nitrate nitrogen in the water but had no significant effect on the content of ammonium nitrogen and it reduced the chemical oxygen demand (COD) of water by 24.9%. Aeration increased the potential of hydrogen (PH), dissolved oxygen (DO) and oxidation–reduction potential (ORP) of water and reduced the total organic carbon content, microbial carbon content and soluble carbon content of the soil in the sediment. Aeration reduced the N2O and CH4 emission fluxes and increased the CO2 emission fluxes in the drainage ditch, but it reduced the greenhouse effect generated by the drainage ditch by 33.7%. This study shows that aeration can reduce both the pollution load and the greenhouse gas emission flux in drainage ditches. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper focuses on the effects of chemical precipitation on the permeability of geotextile envelopes for a subsurface drainage system in arid areas by conducting precipitation experiments of the geotextile in static or flowing solution. The results show that the precipitation process is not significantly promoted or inhibited by the network structure of geotextile. The precipitates in the form of rhombus wrap around the fiber surface. The number of geotextile pores with the smaller diameters decreases significantly after precipitation experiments. As the increase of the area density of precipitates (Δ R), the variation of the pore area (Δ S) and the variation of permeability coefficient (Δ K) of the geotextile decrease rapidly at first and then slowly. The Δ K and Δ S VS Δ R data were best fitted with logarithmic trend line. This study provides a preliminary reference for quantifying the chemical clogging process of geotextile envelopes in arid areas. • The precipitation process is not significantly promoted or inhibited by the network structure of geotextile. • The precipitates wrap around the fiber surface. • The number of geotextile pores with the smaller diameters decreases significantly after precipitation experiments. [ABSTRACT FROM AUTHOR]

This study investigates the influence of clogging substances on pore characteristics and permeability of geotextile envelopes that were used for 3, 7 and 15 years in irrigated farmlands in Xinjiang region, which is arid and suffers from the soil salinity problem. Results show that the macropores (above 125 μm) of envelopes are evidently clogged, whereas the smaller pores less than 100 μm are still unblocked after operation. The permeability coefficients of geotextile envelopes after serving for 3 and 15 years are smaller than the minimum required permeability coefficients after clogging. The main chemical components of clogging substances in the geotextile envelope are silicon dioxide and calcium carbonate. Calcium carbonate content of the geotextile envelope is consistent with calcium carbonate content of soil. Chemical clogging susceptibility increases with the operation time of the subsurface drainage pipes. The ratio of O 90 size of envelope material over d 90 of soils (O 90 / d 90) and saturation index (SI) can be used to assess the susceptibility of physical and chemical clogging respectively. This study provides a preliminary reference for estimating the clogging susceptibility of geotextile envelopes in arid areas. [ABSTRACT FROM AUTHOR]

Streptococcus suis (S.suis)is an important zoonotic pathogen in pigs and human. Bacterial ghosts (BGs) which are empty envelopes were used recently as efficient delivery system in vaccine development. In this study, S.suis ghosts were prepared and protective efficacy was evaluated in mice. Sodium hydroxide was used to prepare S.suis ghosts which were visualized under scanning electron microscopy. The optimum concentration of is Sodium hydroxide 6 mg/mL for ghosts formed. To investigate the S.suis ghosts as a candidate vaccine, the 50 BALB/c mice were randomly divided into three groups: Group A (control group), group B (subcutaneous injection of inactivated S.suis 2), group C (subcutaneous injection of inactivated S.suis 9), group D (subcutaneous injection of S.suis 2 ghosts), group E (subcutaneous injection of S.suis 9 ghosts). Serum were collected from five groups on the day of 7, 14, 21 and 28 after the first immunization for potency assay. Indirect ELISA results showed that antibody titer of blood serum of mice from group S.suis2 ghosts and group S.suis 9 ghosts were significantly higher than blank group(P < 0.01), but were approximate to the conventional inactivated vaccine group SS2. In comparison with the conventional inactivated vaccine, S.suis ghosts as candidate vaccine strategy showed the excellent immunogenicity and provided protection against S.suis challenge in mice model. • A novel method to prepare Streptococcus suis ghost vaccine by treating bacteria with 6 mg/mL NaOH. • The antibody titer of blood serum shows that, for SS9, ghost vaccine group has higher antibody titer than the inactivated vaccine group in mice modle. • S.suis ghosts vaccine showed the excellent immunogenicity and provided protection against S.suis challenge in mice model. [ABSTRACT FROM AUTHOR]