Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands

Several microcosm wetlands unplanted and planted with five macrophytes (Phragmites australis, Commelina communis, Penniserum purpureum, Ipomoea aquatica, and Pistia stratiotes) were employed to remove nitrate from groundwater at a concentration of 21-47 mg NO3-N/l. In the absence of external carbon, nitrate removal rates ranged from 0.63 to 1.26 g NO3-N/m2/day for planted wetlands. Planted wetlands exhibited significantly greater nitrate removal than unplanted wetlands (P<0.01), indicating that macrophytes are essential to efficient nitrate removal. Additionally, a wetland planted with Penniserum showed consistently higher nitrate removal than those planted with the other four macrophytes, suggesting that macrophytes present species-specific nitrate removal efficiency possibly depending on their ability to produce carbon for denitrification. Although adding external carbon to the influent improved nitrate removal, a significant fraction of the added carbon was lost via microbial oxidation in the wetlands. Planting a wetland with macrophytes with high productivity may be an economic way for removing nitrate from groundwater. According to the harvest result, 4-11% of nitrogen removed by the planted wetland was due to vegetation uptake, and 89-96% was due to denitrification.     

Greenhouse gas production and efficiency of planted and artificially aerated constructed wetlands

Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) production in CW mesocosms over three seasons. CW emitted 2-10 times more GHG than natural wetlands. Overall, CH₄ was the most important GHG emitted in unplanted treatments. Oxygen availability through artificial aeration reduced CH₄ fluxes. Plant presence also decreased CH₄ fluxes but favoured CO₂ production. Nitrous oxide had a minor contribution to global warming potential (GWP < 15%). The introduction of oxygen through artificial aeration combined with plant presence, particularly Typha angustifolia, had the overall best performance among the treatments tested in this study, including lowest GWP, greatest nutrient removal, and best hydraulic properties.     

Trends and research features on greenhouse gas emissions from rice production: review based on bibliometric analysis

Environmental Science and Pollution Research - Greenhouse gas from rice production has become a great concern and the focus of a lot of research in recent years. The main aim of the study was to...     

The impact of greenhouse gas emissions on the performance of water companies: a dynamic assessment

Environmental Science and Pollution Research - The water industry plays an important role in reducing greenhouse gas (GHG) emissions and therefore, moving to a low-carbon urban water cycle is of...     

不同植物的表面流人工湿地系统对污染物的去除效果

通过对4种不同植物的表面流人工湿地系统处理新沂河河水的中试研究表明,在CODMn和NH 4-N进水浓度相同条件下,香蒲湿地系统出水CODMn平均浓度最低,仅为13.44 mg/L;美人蕉湿地系统出水NH 4-N平均浓度最低,仅为1.75 mg/L;香蒲和美人蕉湿地系统对CODMn的平均去除率都达到40%以上,而千屈菜和水葱湿地系统都低于30%;美人蕉、香蒲和千屈菜湿地系统对NH 4-N的平均去除率都达到65%以上,而水葱系统则低于60%.综合比较,香蒲和美人蕉湿地系统的净化能力较强.4种植物中水葱耐淹能力最强,完全淹水22 d以上依然生长良好;千屈菜耐淹能力最弱,完全淹水7 d后就开始枯萎,17 d后地上、地下部分全部死亡.     

水力负荷与有机负荷协同作用对人工湿地微生物群落结构的影响

以单层基质结构(CW1)、3层基质结构(CW3)、6层基质结构(CW6)的水平潜流人工湿地系统为对象,考察水力负荷及有机负荷对不同人工湿地系统去除COD、总悬浮固体(TSS)效果的影响,同时利用高通量测序技术,分析高负荷条件下系统微生物群落结构。结果表明,不同水力负荷运行条件下,随着有机负荷的提高,CW1、CW3、CW6湿地系统对COD、TSS的去除率均表现出先升高后下降的趋势,总体看来,在相同运行条件下CW6湿地系统COD、TSS的去除率最高。群落结构分析表明,不同人工湿地系统微生物结构存在相似性,但湿地床体的基质结构会对微生物群落结构产生一定影响,总的来说分层填充的人工湿地系统微生物群落结构更为稳定,对污染物的去除效果更好。     

不同组合垂直潜流式人工湿地对高碳或氮污水的净化效果

4种组合的垂直潜流式人工湿地在高C和高N污染物负荷条件下都可以得到很好的污染物降解效果.VDFVUF湿地组合被确定为最优的组合,它在夏末(7月和8月)和初秋(9月)可以得到较高的污染物去除率,且在8月份可以达到最大值.VDF-VUF湿地组合对于COD、TN和TP去除率的平均值在高C污染物负荷条件下分别为(96.97 ±6.32)％、(89.45 ±5.29)％和(83.12±6.03)％;在高N污染物负荷条件下分别为(93.21±7.84)％、(94.27±4.36)％和(82.36±5.52)％.各种人工湿地组合的COD和TN的去除率都受到了季节变化、湿地组合类型以及这两者的综合效应的显著影响;但是TP的去除率则不受任何因素的显著影响.     

Impact of droughts on industrial emissions into surface waters

Environmental Science and Pollution Research - In this paper, we examine the impact of droughts on industrial emissions into surface waters and transfers to publicly owned treatment works (POTWs)....     

Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes

Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6 kg m⁻²) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3 months and 14 months after char addition. N₂O, CH₄ and CO₂ fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3 months, but after 14 months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N₂O fluxes were from 26% to 79% lower than N₂O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N₂O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH₄ fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14 months after biochar incorporation.     

Impact of agricultural production outsourcing services on carbon emissions in China

Environmental Science and Pollution Research - Increasing food output while reducing agricultural carbon emissions (ACE) is a major challenge to achieving green agriculture in China. Previously...     

Isotopes for improved management of nitrate pollution in aqueous resources: review of surface water field studies

Background  

Environmental agencies have to take measures to either reduce discharges and emissions of nitrate or to remediate nitrate-polluted water bodies where the nitrate concentrations exceed threshold values. Isotope data can support the identification of nitrate pollution sources and natural attenuation processes of nitrate.     

Impact of soil amendments on metribuzin and DCPA half-lives and mobility into agricultural runoff water

The retention and behavior of two herbicides, metribuzin [4-amino-6-tert-butyl-4, 5-dihydro-3-methylthio-1, 2, 4-triazin-5-one] and DCPA [1, 4-Benzenedicarboxylic acid, 2, 3, 5, 6-tetrachloro-, dimethyl] ester, in runoff and seepage water from agricultural fields were investigated. The objectives of this investigation were to: (i) determine the dissipation and half-life (T _1/2) of metribuzin and DCPA herbicides in soil under three management practices: chicken manure (CM), sewage sludge (SS), and no-mulch native soil (NM); (ii) monitor herbicides residues in runoff and infiltration water following addition of soil amendments; and (iii) determine the impact of soil amendments on the transport of NO₃, NH₄, and PO₄ from soil into surface and subsurface water. Half-life (T _1/2) values of metribuzin were 24, 18, and 12 d in CM, SS, and NM treatments, respectively. Similarly, T _1/2 values of DCPA were greater in CM and SS incorporated soil (45.8 and 52.2 d, respectively) compared to NM native soil (26.2 d). Addition of CM and SS to native agricultural soil increased water infiltration, lowering runoff water volume and herbicide residues in runoff following natural rainfall events. We concluded that soil amendments could be used to intercept pesticide-contaminated runoff from agricultural fields. This practice might provide a potential solution to pesticide contamination of surface and seepage water from farmlands.     

基质中铁碳-沸石填充方式对人工湿地温室气体排放的影响

人工湿地在污水治理中已获得广泛应用,但其温室气体排放通量是自然湿地的 2~10倍,对人工湿地温室气体的减排已是亟待解决的问题。通过在温室构建潜流人工湿地系统装置,均为间歇曝气,设立不同填料的填充配比和填充顺序,分别为：添加20%铁碳+80%沸石 (其中铁碳在上层沸石在下层记为T2F8,铁碳在下层沸石在上层记为F8T2,下同) 、40%铁碳+60%沸石 (记为T4F6和F6T4) 、60%铁碳+40%沸石 (记为T6F4和F4T6) 、以添加100%沸石为对照组 (F) ,探究了基质的填充方式对人工湿地系统中温室气体排放的影响。结果表明,与铁碳填充在表层的湿地组1 (T2F8、T4F6、T6F4) 相比,铁碳填充在底层的湿地组2 (F8T2、F6T4、F4T6) 均显著实现了人工湿地中CH₄、N₂O的减排 (P<0.05) ;同时,铁碳-沸石体积比对CH₄、N₂O减排效果影响显著,且铁碳占比越低CH₄和N₂O排放越少 (P<0.05) ;典型周期中曝气段出现CH₄和N₂O排放峰值,湿地F8T2的排放峰值均显著低于其他湿地 (P<0.05) ,其综合GWP最大减排值达到75.82%。铁碳填充在底层及铁碳-沸石体积比为2:8铁碳-沸石人工湿地 (F8T2) 的综合GWP最低,温室气体的减排效果最好。本研究结果可为人工湿地温室气体减排的实践提供参考。     

Fluxes of methane,carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions

We have examined how some major catchment disturbances may affect the aquatic greenhouse gas fluxes in the boreal zone, using gas flux data from studies made in 1994-1999 in the pelagic regions of seven lakes and two reservoirs in Finland. The highest pelagic seasonal average methane (CH(4)) emissions were up to 12 mmol x m(-2) x d(-1) from eutrophied lakes with agricultural catchments. Nutrient loading increases autochthonous primary production in lakes, promoting oxygen consumption and anaerobic decomposition in the sediments and this can lead to increased CH(4) release from lakes to the atmosphere. The carbon dioxide (CO(2)) fluxes were higher from reservoirs and lakes whose catchment areas were rich in peatlands or managed forests, and from eutrophied lakes in comparison to oligotrophic and mesotrophic sites. However, all these sites were net sources of CO(2) to the atmosphere. The pelagic CH(4) emissions were generally lower than those from the littoral zone. The fluxes of nitrous oxide (N(2)O) were negligible in the pelagic regions, apparently due to low nitrate inputs and/or low nitrification activity. However, the littoral zone, acting as a buffer for leached nitrogen, did release N(2)O. Anthropogenic disturbances of boreal lakes, such as increasing eutrophication, can change the aquatic greenhouse gas balance, but also the gas exchange in the littoral zone should be included in any assessment of the overall effect. It seems that autochthonous and allochthonous carbon sources, which contribute to the CH(4) and CO(2) production in lakes, also have importance in the greenhouse gas emissions from reservoirs.     

Effects of pen bedding and feeding high crude protein diets on manure composition and greenhouse gas emissions from a feedlot pen surface

Greenhouse gas (GHG) emissions from concentrated animal feeding operations vary by stage of production and management practices. The objective of this research was to study the effect of two dietary crude protein levels (12 and 16%) fed to beef steers in pens with or without corn stover bedding. Manure characteristics and GHG emissions were measured from feedlot pen surfaces. Sixteen equal-sized feedlot pens (19?×?23 m) were used. Eight were bedded approximately twice a week with corn stover and the remaining eight feedlot pens were not bedded. Angus steers (n = 138) were blocked by live weights (lighter and heavier) with 7 to 10 animals per pen. The trial was a 2?×?2 factorial design with factors of two protein levels and two bedding types (bedding vs. non bedding), with four replicates. The study was conducted from June through September and consisted of four ?28-day periods. Manure from each pen was scrapped once every 28 days and composite manure samples from each pen were collected. Air samples from pen surfaces were sampled in Tedlar bags using a Vac-U-Chamber coupled with a portable wind tunnel and analyzed with a greenhouse gas gas chromatograph within 24 hr of sampling. The manure samples were analyzed for crude protein (CP), total nitrogen (TN), ammonia (NH₃), total volatile fatty acid (TVFA), total carbon (TC), total phosphorus (TP), and potassium (K). The air samples were analyzed for methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) concentrations. The concentration of TN was significantly higher (p < 0.05) in manure from pens with cattle fed the high protein diets. The volatile fatty acids (VFAs) such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids concentrations were similar across both treatments. There were no significant differences in pen surface GHG emissions across manure management and dietary crude protein levels.

Implications: Livestock manure produces odor and emits GHGs (CO₂, CH₄, and N₂O) at different stages of production and management practices that have significant environmental concerns. Thus, it is important to measure GHG contributions from different sources and develop appropriate mitigation strategies for minimizing GHG contribution from livestock production facilities. Two dietary protein levels (12 and 16%) fed to beef steers in pens with or without corn stover bedding were studied. The results indicated that dietary protein levels and bedding vs. no bedding had very little effect on GHG emissions and manure composition under open feedlot conditions in North Dakota climatic conditions and management practices.     

Influence of deployment time and surface wind speed on the accuracy of measurements of greenhouse gas fluxes using a closed chamber method under low surface wind speed

As a convenient method, the closed chamber method has been applied to determine gaseous emission fluxes from fully open animal feeding operations despite the measured fluxes being theoretically affected by deployment time, wind speed over the emitting surface and detected gas mass. This laboratory study evaluated the effects of deployment time (0 to 120 min) and external surface wind speed (ESWS) (0.00, 0.25, 0.50, 0.75, 1.00, 1.50 and 2.00 m sec^-1) on the measurement accuracy of a 300 mm (diameter) × 400 mm (height) (D300×H400) closed chamber using methane (CH₄), nitrous oxide (N₂O) and sulfur hexafluoride (SF₆) as reference gases. The results showed that the overall deviation ratio between the measured and reference CH₄ fluxes ranged from 9.99 % to -37.32 % and the flux was overestimated in the first 20 min. The measured N₂O and SF₆ emissions were smaller than the reference fluxes using the chamber. N₂O measurement accuracy decreased from -14.47 to -35.09% with deployment time extended to 120 min, while SF₆ accuracy sharply increased in the first 40 min, with the deviation stabilizing at approximately -5.00%. CH₄, N₂O and SF₆ measurements were significantly affected by deployment time and ESWS (P<0.05), and the interaction of those two factors greatly influenced CH₄ and SF₆ measurements (P<0.05). With the D300×H400 closed chamber, deployment times of 20 to 30 min and 10 to 20 min are recommended to measure CH₄ and N₂O, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec^-1.

Implications: This study recommended the suitable deployment times and wind speeds for using a D300 × H400 closed chamber to measure CH₄, N₂O, and SF₆ in an open system, such as a dairy open lot and manure stockpile, to help researchers and other related industry workers get accurate data for gas emission rate. Deployment times of 20 to 30 min and 10 to 20 min were recommended to measure CH₄ and N₂O emissions using the D300 × H400 closed chamber, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec^?1. For the measurement of SF₆, a typical tracer gas, a deployment of 70 to 90 min was suggested.     

Long-term increases in surface water dissolved organic carbon: observations, possible causes and environmental impacts

Dissolved organic carbon (DOC) concentrations in 22 UK upland waters have increased by an average of 91% during the last 15 years. Increases have also occurred elsewhere in the UK, northern Europe and North America. A range of potential drivers of these trends are considered, including temperature, rainfall, acid deposition, land-use, nitrogen and CO2 enrichment. From examination of recent environmental changes, spatial patterns in observed trends, and analysis of time series, it is suggested that DOC may be increasing in response to a combination of declining acid deposition and rising temperatures; however it is difficult to isolate mechanisms based on monitoring data alone. Long-term DOC increases may have wide-ranging impacts on freshwater biota, drinking water quality, coastal marine ecosystems and upland carbon balances. Full understanding of the significance of these increases requires further knowledge of the extent of natural long-term variability, and of the natural "reference" state of these systems.     

Review of Singapore's air quality and greenhouse gas emissions: Current situation and opportunities

Singapore has many environmental accomplishments to its credit. Accessible data on air quality indicates that all criteria pollutants satisfy both U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO) air quality standards and guidelines, respectively. The exception is PM_2.5 (particles with an aerodynamic diameter ≤2.5 μm), which is not currently considered a criteria pollutant in Singapore but may potentially be the major local air pollution problem and cause for health concern. Levels of other airborne pollutants as well as their physical and chemical processes associated with local formation, transformation, dispersion, and deposition are not known. According to available emission inventories, Singapore's contribution to the total atmospheric pollution and carbon budget at the regional and global scales is small. Emissions per unit gross domestic product (GDP) are low compared with other countries, although Singapore's per-capita GDP and per-capita emissions are among the highest in the world. Some information is available on health effects, but the impacts on the ecosystem and the complex interactions of air pollution and climate change at a regional level are also unknown. This article reviews existing available information on atmospheric pollution and greenhouse gas emissions and proposes a multipollutant approach to greenhouse gas mitigation and local air quality. Singapore, by reducing its per-capita emissions, increasing the availability of information (e.g., through regularly publishing hourly and/or daily PM_2.5 concentrations) and developing a research agenda in this area, would likely be seen to be a model of a high-density, livable, and sustainable city in Southeast Asia and other tropical regions worldwide.

Implications Singapore is widely recognized for its environmental achievements and often cited as a model of a high-density, livable, and sustainable city. This article reviews available information with the aim to provide a reference for future scientific research of strategic relevance for Singapore's air quality and greenhouse gas mitigation management under a multipollutant framework. However, the limited publicly accessible data and little scientific information prevent a comprehensive assessment of the local air quality and greenhouse gas emissions. Singapore's dynamic economy and strong profile in advanced science and technological innovation have the potential to enhance the research agenda in this area, which is not yet well developed in tropical cities.     

Review of Singapore's air quality and greenhouse gas emissions: current situation and opportunities

Singapore has many environmental accomplishments to its credit. Accessible data on air quality indicates that all criteria pollutants satisfy both U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO) air quality standards and guidelines, respectively. The exception is PM2.5 (particles with an aerodynamic diameter < or = 2.5 microm), which is not currently considered a criteria pollutant in Singapore but may potentially be the major local air pollution problem and cause for health concern. Levels of other airborne pollutants as well as their physical and chemical processes associated with local formation, transformation, dispersion, and deposition are not known. According to available emission inventories, Singapore contribution to the total atmospheric pollution and carbon budget at the regional and global scales is small. Emissions per unit gross domestic product (GDP) are low compared with other countries, although Singapore's per-capita GDP and per-capita emissions are among the highest in the world. Some information is available on health effects, but the impacts on the ecosystem and the complex interactions of air pollution and climate change at a regional level are also unknown. This article reviews existing available information on atmospheric pollution and greenhouse gas emissions and proposes a multipollutant approach to greenhouse gas mitigation and local air quality. Singapore, by reducing its per-capita emissions, increasing the availability of information (e.g., through regularly publishing hourly and/or daily PM2.5 concentrations) and developing a research agenda in this area, would likely be seen to be a model of a high-density, livable, and sustainable city in Southeast Asia and other tropical regions worldwide.     

The influence on carbon,nitrogen recycling,and greenhouse gas emissions under different C/N ratios by black soldier fly

Environmental Science and Pollution Research - Currently, sustainable utilization, including recycling and valorization, is becoming increasingly popular in waste management. Black soldier fly...