Research advances in methane emission from agricultural drainage ditch in coastal reclamation area.

Methane emissions along biomethane and biogas supply chains are underestimated

Urban and agricultural drainage ditches (DD) are important structures for the drainage of runoff. While agricultural DD remove the excess of irrigation water to lowlands areas, urban DD prevent the damage of civilian infrastructure caused by stormwater runoff. The drainage ditches in Mexico are generally unattended sites, where all type of waste is deposited. Moreover, they can be receiving bodies of clandestine domestic or industrial wastewater, which could contaminate the adjacent environment. The abandonment of urban and agricultural DD deteriorates the landscape and cause water contamination which could be derived in public health problems. This chapter presents a review of the current scenario of agricultural and urban DD in Mexico. The importance of these sites, as well as the associated environmental problems, is described. Finally, the vegetated urban and agricultural drainage ditches are presented, and their potential in the mitigation of environmental pollution and the improvement of the agricultural and urban landscape are discussed.

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.

Quantitative analysis of the species composition and succession law of a plant community in a coastal reclamation area is of great significance for revealing the community construction and species coexistence mechanisms, and provides a basis for the rational use and conservation in coastal reclamation areas. Through the investigation of natural plant communities in Dongtai reclamation area and the adjacent national nature reserves in Jiangsu Province, eastern China, the composition and succession of plant communities were studied. A quantitative method was explored to analyze the process of plant succession and its representative species. The results showed that (1) A total of 65 species were found in the vegetation survey. These belonged to 26 families and 61 genera, and Poaceae is the most common plant species. The plant communities in the unreclaimed areas were mainly composed of Poaceae and Cyperaceae. The plant species increased after reclamation, which were mainly composed of Poaceae and Asteraceae; (2) The plant coverage greatly reduced after three years of reclamation, from 80% of the tidal flat to 37.34%, then gradually increased, and remained generally between 50% and 70%; (3) The above-ground biomass of the plant community was sharply reduced after reclamation, from 1.823 kg/m2 in the tidal flat to 0.321 kg/m2 in three years of reclamation, and then maintained at 0.11~0.27 kg/m2; (4)The species succession process of the plant community in the coastal wetland ecosystem that was affected by the reclamation activities transformed from a halophyte community that was dominated by a salt marsh plant community (Suaeda salsa, Spartina alterniflora, Scirpus mariqueter, and Phragmites australis) to a mesophyte plant community that was constructed with pioneer species such as Setaria viridis, Eleusine indica, etc., and eventually succeeded to a xerophyte plant community that was dominated by Humulus scandens and Cyperus difformis, etc. Reclamation activities have a profound impact on the characteristics and succession rules of natural vegetation communities along coastal wetland ecosystems. The period of seven years is presumed to be the tipping point in the succession of the plant community in coastal reclamation areas. The results of this study can provide a basis and reference for ecological protection and restoration in coastal reclamation areas.

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.

Agricultural drainage ditches have received mixed reviews pertaining to their influence, role, and definition within the agricultural ecosystem. In the early part of the 20th Century, drainage ditches were viewed as a positive means to reduce mosquitoinfested wetlands and convert them into valuable agricultural production acreage (GRUMBLES 1991). In recent decades, however, there has been a concerted effort to attain a 'no net loss' of wetland acreage. This has placed drainage ditches in a precarious situation. They are needed to maintain field drainage, yet frequently their own characteristics may identify them as being wetlands themselves. Many drainage ditches possess the three macrofeatures of any wetland: hydroperiod, hydrosoil, and hydrophytes. There is, however, a fundamental difference in how agricultural drainage ditches are defined. For the purpose of the present study, drainage ditches are limited to those structures created to drain production acreage not marginal wetlands. Within the agricultural community, drainage ditches have been viewed as conduits for removing water from production acreage. The public perception has generally been negative in recent years, because constructed ditches have replaced natural drainage systems. Drainage ditches have largely been ignored in scientific research. Research from the Netherlands has focused on drainage ditch maintenance issues (VAN STRIEN et al. 1989, 1991), while DREN! & KERSTINU (1992) reported the use of experimental drainage ditches for ecotoxicological evaluations. Until now, little information has been available on the potential mitigation capabilities of drainage ditches. By viewing drainage ditches as buffers between production acreage and downstream aquatic receiving systems, it is possible to increase the water quality of agricultural runoff following storm events. Therefore, ditches may serve as an alternative best management practice (BMP). Historical BMPs related to agricultural land include, but are not limited to, winter cover crops, stiff grass hedges, riparian zones, grass filter strips, constructed wetlands, and conservation tillage. Most BMP research has been performed in the capacity of reducing sediment and nutrient-laden agricultural runoff (BurlElt et al. 1974, HAYES & HAIIs ION 1983, HAYES et al. 1984,

Xu, Y.; Pu, L.; Zhu, M.; Li, J.; Zhang, M.; Li, P., and Zhang, J., 2014. Spatial variation of soil salinity in the coastal reclamation area, eastern China. Reclamation of coastal saline tidal flats has become a common practice for coastal countries faced with a decrease in cultivated land and an increase in population. Because the variability of soil salinity is considerable, understanding the spatial distribution of this salinity and its components is essential for land use planning. This study was conducted in a coastal area in eastern China that has been reclaimed under various land use types at different times. The objective of the work was to assess the effect of the reclamation time and land use types on soil salinity and spatial variation of soil salinity by using conventional statistics and geostatistical techniques. The results indicate that reclamation times and land use types significantly influence soil salinity in coastal areas. Cropland and aquaculture pond have same effect on soil ...

He, C.; Xiang, X.; Lin, J., and Yu, L., 2020. Study on urban design characteristics of new coastal “reclamation type” town. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 363–367. Coconut Creek (Florida), ISSN 0749-0208.The construction of new coastal reclamation areas is an important decision in China, because it is a form of development and construction that must adapt to many problems in coastal areas, including rapid socioeconomic development, rapid population growth, and serious shortage of land resources. China has many coastal provinces, which will be limited by the shortage of land resources. Therefore, in the rapid economic development, coastal cities will be greatly restricted, which will limit the rapid process of urbanization. China has abundant beach resources. Therefore, reclamation and city building have become the main means to alleviate land resource shortages. In recent years, various coastal cities in China have carried out new reclamation-type town design, which has its own unique characteristics. These new city construction plans need to be improved, because the “reclamation type” city is an important part of urban construction planning in the future. This paper analyzes the current situation of the construction of the new coastal reclamation areas, presents the methods, and suggests improvements.

Considering the characteristics of seabed ground in coastal reclamation area, ultra soft clay improvement method by heavy tamping after rockfilling displacement was proposed combined with a case study. The improvement mechanisms of the method can primarily be attributed to rockfilling displacement (RD), dynamic compaction (DC), dynamic replacement (DR) and dynamic replacement and mixing (DRM). For the case study given in this article, heavy tamping construction program was proposed based on field pilot tests. Furthermore, the effectiveness of the proposed ground improvement method was verified through in situ plate load test, sand fill test and the analyses of observed settlement data. Thus, the method of heavy tamping after rockfilling displacement is applicable for the improvement of seabed ground in coastal reclamation area. It is proposed for similar projects that heavy tamping of fills may be performed by layers and correspondingly tamping energy increased to further enhance the improvement effect of DC, DR and DRM. In addition, delayed improvement effect or time effect of soil mass after heavy tamping is still an issue to be further studied.

Dredging effects on selected nutrient concentrations and ecoenzymatic activity in two drainage ditch sediments in the lower Mississippi River Valley

Contrasting impacts of afforestation on nitrous oxide and methane emissions

High energy dynamic compaction (HEDC) is adopted in a coastal reclamation area because the grain size of backfilled soil mostly ranges between 20 cm and 100 cm. The in situ tests for evaluating the effectiveness of HEDC were performed on the backfilled soil ground. The crater depth per drop and the whole test zone elevations before and after HEDC were measured and analyzed. Dynamic penetration tests and spectral analysis of surface wave (SASW) tests were used for investigating the improvement depth. Furthermore, the allowable bearing capacity of HEDC treated ground was determined based on the results of plate-load tests. It was found that HEDC did not cause the ground surface heave during construction, and was more effective than low energy dynamic compaction (LEDC) in terms of applied energy utilization. Based on the test results, the improvement depth of HEDC at this site was not less than 14 m, and there was no obvious weak layer within the range of improvement depth. The allowable bearing capacities were larger than 160 kPa. The investigation results indicate that the HEDC technique is an effective way for improving backfilled coarse-grained soil in coastal reclamation areas. This technique helps to achieve both greater improvement depths and higher ground bearing capacities as compared with LEDC.

Agricultural drainage ditches are ubiquitous features in lowland agricultural landscapes, built primarily to facilitate land drainage, irrigate agricultural crops and alleviate flood risk. Most drainage ditches are considered artificial waterbodies and are not typically included in routine monitoring programmes, and as a result the faunal and floral communities they support are poorly quantified. This paper characterises the aquatic macroinvertebrate diversity (alpha, beta and gamma) of agricultural drainage ditches managed by an internal drainage board in Lincolnshire, UK. The drainage ditches support very diverse macroinvertebrate communities at both the site (alpha diversity) and landscape scale (gamma diversity) with the main arterial drainage ditches supporting greater numbers of taxa when compared to smaller side ditches. Examination of the between site community heterogeneity (beta diversity) indicated that differences among ditches were high spatially and temporally. The results illustrate that both main arterial and side ditches make a unique contribution to aquatic biodiversity of the agricultural landscape. Given the need to maintain drainage ditches to support agriculture and flood defence measures, we advocate the application of principles from ‘reconciliation ecology’ to inform the future management and conservation of drainage ditches.

Assessing GHG cycling in agricultural and riparian soils using a uniform reactive transport modeling approach

To investigate the whole-reach nitrate (NO3--N) uptake dynamics in a headwater agricultural stream, we performed five pulse tracer additions of a reactive solute (as KNO3) and a conservative solute (as NaBr) in an agricultural drainage ditch in Hefei district, Chaohu Lake basin, from October 2016 to April 2017. The TASCC (tracer additions for spiraling curve characterization) approach and Michaelis-Menten (M-M) method were applied for the simulation of NO3--N uptake dynamics. Results showed that the ambient areal rate of total NO3--N uptake Uamb varied from 11.40 to 69.13 μg ·(m2 ·s)-1 with an average of 34.45 μg ·(m2 ·s)-1, and the ambient uptake velocity Vf-amb averaged 0.24 mm ·s-1 and varied from 0.07 to 0.43 mm ·s-1 across three well-mixed sub-reaches in the study. The ambient uptake length Sw-amb averaged 199.06 m with a range from 92.51 to 405.74 m, which was much smaller than the length of the drainage ditch (about 2.5 km), suggesting that the agricultural drainage ditch had a high potential for NO3--N retention. Generally, the M-M model fit the NO3--N uptake dynamics well, and the maximum uptake Umax ranged from 158 to 1280 μg ·(m2 ·s)-1 with a mean of 631.13 μg ·(m2 ·s)-1. The half saturation constant Km ranged from 0.16 to 5.52 mg ·L-1 with a mean of 1.46 mg ·L-1. According to correlation analysis, Sw-amb was negatively correlated with NO3--Namb, and Uambwas significantly positively correlated with NO3--Namb, while other nutrient spiraling metrics were not correlated with the NO3--N ambient concentration. Hydrological conditions had no distinct effect on the NO3--N retention, but both the width variability Фw and variability in cross-sectional area ФA were significantly correlated with most of the nutrient spiraling metrics, indicating that geomorphic features in the drainage ditch evidently impacted NO3--N uptake.