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1.
Huan Jing Ke Xue ; 42(7): 3156-3165, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212641

RESUMO

Watershed land use patterns combined with hydrological regimes affect riverine nitrogen (N) sources, transformation pathways, and exports, which can affect watershed health and freshwater ecosystem service supply. Understanding how land use and hydrological regimes affect riverine N exports is therefore useful for developing sustainable watershed management strategies. Based on in-situ observations during the period 2010-2017, watershed modeling, geospatial technology, and statistical analysis were coupled in this study to explore the responses of riverine nitrogen exports to watershed land use pattern and hydrological regime in a medium-sized watershed. Results showed that nitrate was the major form of dissolved inorganic N in the Jiulong River watershed; agricultural and urban watersheds had higher N exports and greater temporal variability than those in natural watershed. The seasonal fluctuation for watershed N concentrations and exports was obvious in wet years compared with dry years. Compared with the hydrological regime, the land use pattern had significant effects on N concentrations and exports. This study demonstrated that spatiotemporal variations of riverine nitrogen exports were mainly contributed by the coupled effects of watershed land use pattern and hydrological regime.


Assuntos
Rios , Poluentes Químicos da Água , Ecossistema , Monitoramento Ambiental , Nitrogênio/análise , Poluentes Químicos da Água/análise
2.
Huan Jing Ke Xue ; 42(7): 3176-3185, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212643

RESUMO

In order to reveal the interaction of overlying water-interstitial water nitrogen and phosphorus nutrient salt in summer at the entrance region of Baiyangdian Lake, this study sampled six main rivers in the region during July 2019. An analysis of the overlying water and interstitial water quality characteristics and the diffusion flux of applied nutrients at the sediment-water interface revealed the effects of nutrient diffusion on sediments and overlying water. The overlying water analysis showed that the water quality was slightly alkaline in the Baiyangdian Lake. The content of dissolved oxygen (DO) was lower, which provided an anaerobic environment for the release of endogenous pollutants from sediments. The ammonia nitrogen (NH4+-N) ranged from 0.35 to 1.76 mg·L-1, and the content of ammonia nitrogen was the highest in the Zhulong River, which was the main source of water supply. The nitrate nitrogen (NO3--N) content ranged from 0.75 to 1.97 mg·L-1. The total dissolved nitrogen (TDN) ranged from 0.99 to 2.70 mg·L-1, and the content of TDN was the highest in Puhe River. The content of total dissolved phosphorus (TDP) was 0.03 to 0.15 mg·L-1, and the content of TDP was the highest was Baigouyin River, which is near the residential area. The results indicated that the content of ammonia nitrogen in the interstitial water was between 5.24 and 10.64 mg·L-1, which was 10 times that of the overlying water, and endogenous pollution in the former was severe. The nitrate nitrogen content ranged from 0.36 to 0.79 mg·L-1. The total dissolved nitrogen content was between 5.36 and 12.02 mg·L-1, which was 5 times higher than that of the overlying water. The total dissolved phosphorus was between 0.03 and 0.3 mg·L-1. According to integrated pollution index, the degree of interstitial water pollution was much higher than that of overlying water, and the sampling points are seriously polluted. The exchange flux analysis of NH4+-N, TDN, and TDP demonstrated that the diffusion flux of NH4+-N was between 1.71 and 7.43 mg·(m2·d)-1, and the diffusion rate of endogenous ammonia nitrogen to the overlying water was fastest in Fu River, the absorbing river in Baoding. The diffusion flux of total dissolved nitrogen was lower in the Baigouyin River, and the other five sample points averaged 9.11 mg·(m2·d)-1. In summer, the dissolved oxygen was lower and the water-sediment had a larger concentration difference, which led to massive nitrogen nutrient of sediment in anaerobic conditions released to the overlying water in great quantities that caused the serious pollution. The diffusion flux of dissolved total phosphorus showed that the sediment of Pinghe River acted as a "sink" of phosphorus nutrients, and the other sampling points ranged from 0.03 to 0.16 mg·(m2·d)-1, showing the state of phosphorus nutrient released upward to the overlying water. Finally, diffusion flux indicated that endogenous pollutants are crucial sources of overlying water pollutants. In order to effectively control the water quality in the entrance area, desilting the nitrogen and phosphorus nutrient salt of sediment is urgently required.


Assuntos
Poluentes Químicos da Água , Qualidade da Água , China , Monitoramento Ambiental , Sedimentos Geológicos , Lagos , Nitrogênio/análise , Fósforo/análise , Água , Poluentes Químicos da Água/análise
3.
Huan Jing Ke Xue ; 42(7): 3186-3197, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212644

RESUMO

Zhenjiang City is located in the intersection of the Yangtze River and the Beijing-Hangzhou Grand Canal, which is the most important water transportation hub in China, with abundant water resources and a dense river network. In recent years, the water quality in this region has declined with the rapid development of the economy and enhanced anthropogenic activity. Therefore, it is crucial to understand the state of water and sediment pollution in rivers and lakes of Zhenjiang City, which can provide important basic data for improving the water environment quality for this region. In total, 21 sampling sites (including 10 sites from Jinshan Lake and 11 sites from the ancient canal) in Zhenjiang City were selected, and overlying water and sediment samples were sampled in winter and summer, respectively. In addition, the physical and chemical parameters of overlying water and sediment samples were determined, respectively, and the organic index as well as organic nitrogen index were analyzed in order to evaluate the degree of sediment contamination in this region. Results showed that ① The TN concentration of overlying water changed from 1.95 mg·L-1 to 15.71 mg·L-1 in the winter and from 0.64 mg·L-1 to 12.09 mg·L-1 in the summer, with mean values of 4.01 mg·L-1 and 4.07 mg·L-1, respectively, which are higher than those of the surface water Ⅴ class standard. In addition, the ranked order of NH4+-N was as follows:winter < summer and river > lake; ② the TN content in the sediment samples ranged from 394.61 mg·kg-1 to 3288.09 mg·kg-1 and from 869.21 mg·kg-1 to 3598.04 mg·kg-1, respectively, with the mean values of 1928.58 mg·kg-1 and 2068.40 mg·kg-1. The ranked order of TN, NH4+-N, NO3--N, and Org-N was as follows:winter > summer for lake sediment samples. For river sediment samples, the ranked order of TN was winter < summer, whereas those of NH4+-N and NO3--N were winter > summer, indicating more complicated seasonal distribution for river sediment. In addition, the NO3--N content was higher in lake sediment than in river sediment, whereas that of NH4+-N was higher in river sediment than in lake sediment. The C/N ratio results indicated that the organic matter in sediments primarily resulted from endogenous pollution in this region; ③ Results of organic nitrogen index confirmed that 60% sediment samples from the lake in winter and the river in summer belong to the Ⅳ pollution level, indicating that organic nitrogen pollution existed in these samples. The results of organic index confirmed that 70% and 54.55% sediments samples belong to the Ⅱ pollution level, indicating that the sediments were not severely polluted in rivers and lakes of Zhenjiang City. The results demonstrate that sediments in rivers and lakes of Zhenjiang City are mainly polluted by nitrogen. Our findings provide important basic data for nitrogen control schemes in river water and sediment in Zhenjiang City.


Assuntos
Rios , Poluentes Químicos da Água , Pequim , China , Monitoramento Ambiental , Sedimentos Geológicos , Lagos , Nitrogênio/análise , Fósforo/análise , Água , Poluentes Químicos da Água/análise
4.
Huan Jing Ke Xue ; 42(7): 3242-3252, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212650

RESUMO

Changes in the community stability of freshwater phytoplankton not only induce a series of ecological environment problems but also influence freshwater ecosystem service functions. To understand the changes in community stability and its driving factors, phytoplankton and environmental parameters were analyzed at 11 sample sites in Huaxi River, a tributary of the Three Gorges Reservoir, in spring, summer, autumn, and winter. Moreover, the resource use efficiency (RUEPP), phytoplankton richness (S), phytoplankton evenness (J), and community turnover (BC) were also determined. Results showed that a total of 8 phyla, including 103 genera and 380 species, were identified in Huaxi River throughout the year. Among them, 264 species were collected in spring, 181 in summer, 197 in autumn, and 183 in winter. The number of Chlorophyta was the largest, followed by Bacillariophyta, Euglenophyta, and Cyanophyta. The number of species and cell density in S0 site were the smallest, while those in S2 site were the largest. The RUEPP was fluctuated in four seasons, with the maximum in summer and the minimum in autumn. BC was significantly negatively correlated with RUEPP, phytoplankton richness, total phosphorus (TP), orthophosphate (PO43--P), total nitrogen (TN), nitrate (NO3--N), permanganate index, and conductivity (Spc); however, it was significantly positively correlated with phytoplankton evenness and dissolved oxygen (DO). These results suggest that water level regulation in the Three Gorges Reservoir has a significant impact on the structure of phytoplankton community in Huaxi River, which leads to the instability of phytoplankton community and easy replacement, and the degree of community turnover is affected by the combined effect of biological and abiotic factors.


Assuntos
Diatomáceas , Fitoplâncton , China , Ecossistema , Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise , Rios , Estações do Ano
5.
Huan Jing Ke Xue ; 42(7): 3272-3280, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212653

RESUMO

To clarify the impact of water quality and social activity in the Baiyangdian wetland on the biological community, the change characteristics of bacterial, fungal, and archaeal communities in different areas of the Dian District were studied. Samples were collected at the entrance of Fuhe District (NBB), tourist areas with frequent human social activities (NBD), residential breeding areas (NBX), and village sparse areas (NBN). The physical and chemical characteristics and biological communities of the samples were evaluated. The results of the study show that the COD concentration of organic pollutants in the NBB was 12.35 mg·L-1, and the total nitrogen concentration was 10.12 mg·L-1, that the concentration was highest. Moreover, the water quality in NBD and NBX was better than that of NBB. The NBN area exhibited the best water quality, with COD and total nitrogen concentration values of 6.9 mg·L-1 and 1.82 mg·L-1, respectively. Many types of NBB bacteria were recorded, with a diversity index of 5.86, and NBN diversity index exceeding 4.78. The dominant bacterial flora in all samples was the Proteobacteria, which accounts for 68.8% of the total bacterial communities in NBN samples. The diversity index of fungi in NBB was only 2.14. There were many types of fungi in NBN, with a diversity index of 3.23. Chytridiomycota was found in the NBD and NBN, accounting for 5.4% and 9.8% of the total number of fungi, respectively. The Chytridiomycota was main decomposer of hard to degrade organic carbon. The diversity of archaea of NBN was the lowest among all the samples. Crenarchaeota was the dominant phylum, which accounts for 39.0%, 51.9%, 47.3%, and 30.1% of NBB, NBD, NBX, and NBN samples, respectively. The number of Halobacterota was lower than Crenarchaeota. The main factor of eutrophication and microbial community changes in Baiyangdian wetland was the results of the combined action of external and internal pollution. Both external and internal pollution increased the organic matter, nitrogen and phosphorus content in the water, and the microbial community structure has changed significantly. The contents of organic matter, nitrogen, and phosphorus in water were increased and the microbial community structures were changed significantly by the increase of both external and internal pollution.


Assuntos
Microbiota , Áreas Alagadas , Humanos , Nitrogênio/análise , Qualidade da Água , Abastecimento de Água
6.
Huan Jing Ke Xue ; 42(7): 3316-3327, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212657

RESUMO

In semi-arid and semi-humid areas, the occurrence of non-point source nutrient pollution is mainly driven by rainfall-runoff events, and nutrient loss under rainfall events determines annual total pollution load. Therefore, research on riverine nutrient dynamics under rainfall-runoff events in flood seasons is critical for simulating and controlling pollution load in semi-arid and semi-humid areas. The Chaohe River watershed, upstream watershed of Miyun Reservoir in Beijing was considered as study area, water quantity and quality of rainfall-runoff process at Gubeikou and Xiahui stations were monitored synchronously in flood seasons in 2018 and 2019. The results indicated the following:① Among the three rainfall events (E1, E2, and E3), E1 had the highest precipitation and rainfall intensity, and the corresponding discharge and pollutant concentrations were the highest. ② Under different rainfall events, the pollutant concentrations and their variations were different. The variations of concentrations of total nitrogen (TN), ammonia (NH4+-N), nitrate (NO3--N), total phosphorus (TP), and total suspended solids (TSS) were similar to the discharge process under the heavy rainstorm event (E1) and the rainstorm event (E3). The concentrations of total nitrogen (TN), ammonia (NH4+-N), total phosphorus (TP), and total suspended solids (TSS) were similar to the discharge process under the heavy rain events (E2), but the variations of nitrate (NO3--N) concentrations were opposite to those in the discharge process. ③ The concentrations and variations of different forms of pollutants were different under different rainfall events. Under the event of strong rainfall erosion (E1 and E2), the concentrations of particulate pollutants varied significantly, being positively correlated with that of total suspended solids (TSS). For the rainfall event that did not cause soil erosion (E3), the forms of nitrogen and phosphorus were dominated by total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) respectively, whose variations were mainly related to discharge. ④ The discharge and pollutant concentrations at each station varied under different rainfall events. Heavy rainfall erosion was more obvious at Gubeikou station, causing significant variations in discharge, TP, and TSS. Therefore, these results can be used to determine migration patterns of non-point source pollutants caused by rainfall-runoff events and provide references for water quality prediction and control in flood seasons.


Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Pequim , China , Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise , Chuva , Rios , Movimentos da Água , Poluentes Químicos da Água/análise
7.
Huan Jing Ke Xue ; 42(7): 3422-3429, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212669

RESUMO

Cold acclimation is an effective approach for improving the nitrogen removal performance and operational stability of partial nitritation/ANAMMOX (PN/A) combined processes at low temperatures. To explore the specific effects of cold acclimation on the characteristics of sludge, differentiations in temperature sensitivity, granular morphology, composition of extracellular polymer substance (EPS), and bacterial community structure between PN/A granular sludges cultivated at medium-high temperature (30℃) and acclimated to low temperature (15℃) were investigated in this study. The results of reaction thermodynamics showed that the nitrogen removal performance of the granules acclimated to low temperature (GL) was significantly higher than that of those cultivated at medium-high temperature (GH) under the low temperature (10-20℃), and the apparent activation energy (Ea) of total inorganic nitrogen removal for the former was decreased by 28.4%. Compared with GH, GL had a smaller average particle size of 25.8% and higher EPS contents of 16.6%, resulting in a significant lower settling property. Based on the high-throughput sequencing results, GL exhibited a higher diversity of bacterial community, and a lower relative abundance ratio (0.04) of aerobic ammonium-oxidizing bacteria (Nitrosomonas) and anaerobic ammonium-oxidizing bacteria (Candidatus_Kuenenia) than 0.34 for GH. It indicated that the PN/A granules held a strong ability to retain slow-growing autotrophic bacteria in the system, even under low temperatures. These findings could provide meaningful references for analyzing the self-adaption mechanisms of PN/A sludge to low temperature conditions and promote the industrial application of combined processes.


Assuntos
Nitrogênio , Esgotos , Aclimatação , Reatores Biológicos , Desnitrificação , Nitrogênio/análise , Oxirredução
8.
Huan Jing Ke Xue ; 42(7): 3442-3450, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212671

RESUMO

Based on Landsat satellite remote sensing images, this study interprets land use changes in the Yangtze River Delta (YRD) region from 2000 to 2018. Combined with changes in nitrogen fertilizer application, the changes in ammonia emissions from farmland ecosystem due changes in land use and nitrogen fertilizer application were further investigated. The results show that along with the rapid urbanization process, the area of cultivated land in the YRD region has gradually decreased from 276269 km2 (49% of total land area) in 2000 to 244001 km2 (44%) in 2018. The effects of changes in land use and nitrogen fertilizer application on ammonia emissions from farmland ecosystems mainly include emissions from soil background and nitrogen fertilizer application. From 2000 to 2018, ammonia emissions due to the application of nitrogen fertilizer decreased from 690 kt·a-1 to 541 kt·a-1 (relative decrease by 22%), while the ammonia emissions from the soil background reduced from 32 kt·a-1 to 29 kt·a-1 (decrease by 9%). During the past 20 years, urbanization in the YRD region has accelerated, and the area of cultivated land and the total amount of nitrogen fertilizer application have significantly reduced, thus resulting in reductions in ammonia emissions from the farmland ecosystem.


Assuntos
Amônia , Ecossistema , Agricultura , Amônia/análise , China , Fertilizantes/análise , Nitrogênio/análise , Rios , Solo
9.
Huan Jing Ke Xue ; 42(7): 3451-3457, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212672

RESUMO

Hydrochar can mitigate ammonia volatilization when applied in paddy fields due to its acidity and adsorption property. To realize the recycling of agricultural biowaste as well as the control of nutrient loss from paddy fields, a simulation soil-column experiment with wheat straw hydrochar (WHC) and water-washed hydrochar (W-WHC) was conducted to evaluate the performance of rice yield and ammonia volatilization from paddy fields. The results showed that WHC and W-WHC applied in paddy fields both increased the rice yield and the increased effect at low application rate (0.5%) was higher than that at high application rate (1.5%). In comparison with the control treatment (CKU), the rice yields achieved from low application rate treatments for WHC and W-WHC increased by 17.16% and 20.20% respectively. Except for the equal emission rate between W-WHC with low application rate and CKU treatments, hydrochar (WHC, W-WHC) addition reduced the ammonia volatilization from paddy fields when compared with the CKU. Among them, the ammonia volatilization levels from low-application WHC and high-application W-WHC treatments were significantly lower than that from the CKU treatment, reduced by 31.01% and 17.40%, respectively. Based on the analysis of ammonia volatilization during different fertilization stages, the control effect of hydrochar addition on ammonia volatilization was mainly benefited from tillering and panicle fertilizer stages. The change in the nitrogen concentration of surface water at the tillering fertilizer stage and in pH at the panicle fertilizer stage with the addition of hydrochar was the main driving factor for the reduction in ammonia volatilization. The results show that sufficient amounts of hydrochar derived from wheat straw application can increase crop yield while reducing ammonia volatilization from paddy fields. This method provides an effective route for recycling agricultural biowastes.


Assuntos
Amônia , Oryza , Amônia/análise , Fertilizantes/análise , Nitrogênio/análise , Solo , Triticum , Volatilização
10.
Huan Jing Ke Xue ; 42(7): 3555-3564, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212682

RESUMO

The spatial distribution of fertilization intensity and its influencing factors are significant for the accurate management of fertilization and pollution prevention and control. Previous studies are mostly limited to the discussion of human factors that influences the spatial distribution of fertilization intensity while ignoring natural geographical factors. Based on the chemical fertilizer survey data collected from 23492 sites in Chengdu Plain and combined with Geostatistics analysis and Geographic Information System (GIS) technology, the spatial distribution characteristics and influencing factors of average nitrogen and phosphorus fertilizer application intensity from 2010 to 2015 in this region were explored. The results show that:① the average annual application intensity of nitrogen and phosphorus fertilizer in the study area from 2010 to 2015 is generally in the low and medium risk intensity of 120-360 kg·hm-2 and 60-180 kg·hm-2. The high risk intensity is mainly distributed in the grain (fruit) and vegetable growing areas such as Pidu, Pengzhou, Shifang, Longquanyi and Jintang, while the relatively low value areas are mostly distributed in the south and northeast. ② the nugget coefficients of nitrogen and phosphorus fertilizer application intensities are 66.17% and 41.60%. Their spatial distribution is determined by structural and random factors, showing a moderate spatial autocorrelation. ③ both human and natural factors have significant effects on the application intensity of nitrogen and phosphorus fertilizer. The crop type (fine classification) can explain the spatial variation of nitrogen fertilizer and phosphorus fertilizer respectively by 12.90% and 25.10%, which is the main controlling factor affecting the spatial distribution of nitrogen and phosphorus application intensity; the importance of soil parent material is second only to the planting crop type, and the independent explanation ability of phosphorus application intensity is about 3.6 times higher than that of nitrogen application intensity. When the type of planting crop plays a decisive role, the soil parent material still deeply restricts and affects the spatial distribution of nitrogen and phosphorus fertilizer application intensity in the study area. Therefore, the comprehensive effects of planting crop types and soil parent materials should be considered in fertilization management and environmental risk analysis, and the effects of soil parent material should also be taken into account in the application of phosphate fertilizer.


Assuntos
Fertilizantes , Fósforo , Agricultura , China , Fertilizantes/análise , Nitrogênio/análise , Fósforo/análise , Solo
11.
Artigo em Inglês | MEDLINE | ID: mdl-34200308

RESUMO

Water pollution caused by excessive nutrient and biological invasion is increasingly widespread in China, which can lead to problems with drinking water as well as serious damage to the ecosystem if not be properly treated. Aquatic plant restoration (phytoremediation) has become a promising and increasingly popular solution. In this study, eight native species of low-temperature-tolerant aquatic macrophytes were chosen to construct three combinations of aquatic macrophytes to study their purification efficiency on eutrophic water in large open tanks during autumn in Guangzhou City. The total nitrogen (TN) removal rates of group A (Vallisneria natans + Ludwigia adscendens + Monochoria vaginalis + Saururus chinensis), group B (V. natans + Ipomoea aquatica + Acorus calamus + Typha orientalis), and group C (V. natans + L. adscendens + Schoenoplectus juncoides + T. orientalis) were 79.10%, 46.39%, and 67.46%, respectively. The total phosphorus (TP) removal rates were 89.39%, 88.37%, and 91.96% in groups A, B, and C, respectively, while the chemical oxygen demand (COD) removal rates were 93.91%, 96.48%, and 92.78%, respectively. In the control group (CK), the removal rates of TN, TP, and COD were 70.42%, 86.59%, and 87.94%, respectively. The overall removal rates of TN, TP, and COD in the plant groups were only slightly higher than that in CK group, which did not show a significant advantage. This may be related to the leaf decay of some aquatic plants during the experiment, whereby the decay of V. natans was the most obvious. The results suggest that a proper amount of plant residue will not lead to a significant deterioration of water quality.


Assuntos
Águas Residuárias , Purificação da Água , China , Ecossistema , Nitrogênio/análise , Fósforo/análise
12.
J Environ Sci (China) ; 106: 39-46, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34210438

RESUMO

Salinization in estuarine wetlands significantly alters the balance between their nitrogen (N) removal and retention abilities but these processes have not yet been characterized effectively. In the present study, the potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped using N isotope tracing methods along salinity gradients across the Yellow River Delta wetland (YRDW) in China. The contribution of anammox to total dissimilatory N transformations in YRDW was merely 6.8%, whereas denitrification and DNRA contributed 52.3% and 40.9%, respectively. The potential rate of denitrification (5.82 µmol/kg/h) decreased significantly along salinity gradients and markedly exceeded DNRA potential rate (2.7 µmol/kg/h) in fresh wetlands, but was lower than that of DNRA in oligohaline wetlands (3.06 and 3.18 µmol/kg/h, respectively). Moreover, a significantly positive relationship between salinity and DNRA/denitrification was obeserved, indicating that increased salinity may favor DNRA over denitrification. Furthermore, total sulfur (TS) content and ratio of total organic carbon to total nitrogen (C/N) increased with the salinity gradient and showed evident positive relationships with the DNRA/denitrification ratio. In this study, we proved that increased salinization resulted in the dominance of DNRA over denitrification, possible through the addition of S and alteration of the C/N in estuarine wetlands, leading to increased N retention in estuarine wetlands during salinization, which would enhance the eutrophication potential within wetlands and in downstream ecosystems.


Assuntos
Compostos de Amônio , China , Desnitrificação , Ecossistema , Nitratos/análise , Nitrogênio/análise , Oxirredução , Salinidade , Áreas Alagadas
13.
Ying Yong Sheng Tai Xue Bao ; 32(6): 1919-1927, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212595

RESUMO

Understanding the changes of natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) along soil profile is of great importance in revealing the mechanisms of soil carbon and nitrogen cycling in terrestrial ecosystems. Based on a comprehensive review on the distribution of δ13C and δ15N along soil profile, the mechanisms underlying their vertical distribution were mainly introduced here. There were three mechanisms driving the δ13C vertical distribution in soil profile: 1) historical changes of vegetation δ13C value, 2) changes of C3-C4 species dominance in plant communities, 3) accumulation of 13C-enriched microbial-derived carbon during decomposition. The effects of 13C Suess effect on the vertical distribution of δ13C in soil profile were also discussed. There were four mechanisms underlying the vertical distribution of δ15N in soil profile: 1) 15N-depletion gas loss during denitrification, 2) accumulation of 15N-enriched microbial-derived nitrogen during decomposition, 3) accumulation of 15N-encriched mycorrhizal fungi residues in deep soil as a result of transferring 15N-depleted nitrogen compounds to plants by mycorrhizae, 4) intera-ction between soil organic matter and mineral substance. We proposed important concerning points for the future study on vertical distribution of natural abundance of stable carbon and nitrogen isotopes in soil profile.


Assuntos
Carbono , Solo , Isótopos de Carbono/análise , Ecossistema , Nitrogênio/análise , Isótopos de Nitrogênio
14.
Ying Yong Sheng Tai Xue Bao ; 32(6): 1989-1997, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212603

RESUMO

Gaseous nitrogen (N) emission [nitric oxide (NO), nitrous oxide (N2O), and nitrogen (N2)] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the 15N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N2O and N2 production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total 15N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added 15N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N2O and N2 respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N2O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N2O production. For N2 production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N2O and N2 production. Our results demonstrated that the 15N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.


Assuntos
Óxido Nitroso , Solo , Anaerobiose , Desnitrificação , Gases , Nitrificação , Nitrogênio/análise , Óxido Nitroso/análise
15.
Food Chem ; 362: 130151, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34087707

RESUMO

Hydrogels based on alginate and methylcellulose were developed as a colorimetric indicator for monitoring minced pork spoilage. The hydrogel was fabricated by an external gelation method using Ca2+ as the crosslinking agent. The pH-sensitive dye bromothymol blue was incorporated into the hydrogel to act as an indicator. The hydrogel's swelling index increased with an increasing ratio of methylcellulose, suggesting that the water uptake capacity is tunable by the polymer composition. The hydrogel's compression strength is directly proportional to the alginate content. The hydrogel indicator demonstrated a color change from orange to yellow (day 6) upon detecting total volatile basic nitrogen (TVB-N) built up in the package during minced pork storage at 4 °C, and the results showed a positive correlation between the color change, TVB-N and pH change of minced pork. This result demonstrated the potential application of the hydrogel as a spoilage indicator in intelligent packaging.


Assuntos
Amônia/análise , Colorimetria/métodos , Análise de Alimentos/métodos , Hidrogéis/química , Carne de Porco/análise , Alginatos/química , Animais , Azul de Bromotimol/química , Cálcio/química , Cor , Colorimetria/instrumentação , Análise de Alimentos/instrumentação , Qualidade dos Alimentos , Armazenamento de Alimentos , Concentração de Íons de Hidrogênio , Metilcelulose/química , Nitrogênio/análise , Suínos , Água/química
16.
Chemosphere ; 279: 130876, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34134436

RESUMO

Conventional wastewater treatment processes cannot effectively remove dissolved organic nitrogen (DON) and soluble non-reactive phosphorus (sNRP), which can pose regulatory compliance challenges for total nitrogen and total phosphorus discharges. Moreover, DON and sNRP are not easily recoverable for beneficial reuse as part of the waste to resource paradigm. Conversion of DON and sNRP to more readily removable dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (sRP), respectively, will help meet stringent nutrient limits and facilitate nutrient recovery. In this study, electro-oxidation (EO) was evaluated for conversion of four DON compounds to DIN and five sNRP compounds to sRP. EO was more efficient and provided higher extents of conversion of the recalcitrant nutrient fractions compared to a more traditional advanced oxidation process, UV/H2O2. Direct electron transfer was likely the dominant oxidation mechanism for EO-based DON and sNRP conversion, with DON being more recalcitrant. Among the DON compounds tested, greater availability of primary amine (C-N bonds) yielded greater conversion compared to compounds with fewer primary amine or those with secondary amine (C-N-C bond). Among the sNRP compounds tested, those with P-O-C bonds (organic sNRP) converted more readily than those with P-O-P bonds (inorganic sNRP), presumably because cleavage of the latter bond requires greater energy. Using 30 min of EO treatment, the highest DON and sNRP compound conversion was 11.7 ± 0.09% for urea and 31.1 ± 0.75% for beta-glycerol phosphate. A similar extent of EO-based conversion of DON (6.41 ± 1.5%) and sNRP (32.7 ± 3.3%) was observed in real wastewater.


Assuntos
Fósforo , Purificação da Água , Peróxido de Hidrogênio , Nitrogênio/análise , Águas Residuárias
17.
Ecotoxicol Environ Saf ; 220: 112413, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34139628

RESUMO

Aerobic composting is commonly used to dispose livestock manure and is an efficient way to reduce antibiotic resistance genes (ARGs). Here, the effects of different quality substrates on the fate of ARGs were assessed during manure composting. Results showed that the total relative abundances of ARGs and intI1 in additive treatments were lower than that in control, and high quality treatment with low C/N ratio and lignin significantly decreased the relative abundance of tetW, ermB, ermC, sul1 and sul2 at the end of composting. Additionally, higher quality treatment reduced the relative abundances of some pathogens such as Actinomadura and Pusillimonas, and some thermotolerant degrading-related bacteria comprising Pseudogracilibacillus and Sinibacillus on day 42, probably owing to the change of composting properties in piles. Structural equation models (SEMs) further verified that the physiochemical properties of composting were the dominant contributor to the variations in ARGs and they could also indirectly impact ARGs by influencing bacterial community and the abundance of intI1. Overall, these findings indicated that additives with high quality reduced the reservoir of antibiotic resistance genes of livestock manure compost.


Assuntos
Compostagem/métodos , Resistência Microbiana a Medicamentos/genética , Genes Bacterianos/efeitos dos fármacos , Esterco/análise , Esterco/microbiologia , Animais , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Carbono/análise , Carbono/farmacologia , Galinhas/microbiologia , Lignina/análise , Lignina/farmacologia , Microbiota/efeitos dos fármacos , Nitrogênio/análise , Nitrogênio/farmacologia
18.
Environ Sci Technol ; 55(12): 7890-7899, 2021 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-34060819

RESUMO

To understand the environmental and anthropogenic drivers of stream nitrogen (N) concentrations across the conterminous US, we combined summer low-flow data from 4997 streams with watershed information across three survey periods (2000-2014) of the US EPA's National Rivers and Streams Assessment. Watershed N inputs explained 51% of the variation in log-transformed stream total N (TN) concentrations. Both N source and input rates influenced stream NO3/TN ratios and N concentrations. Streams dominated by oxidized N forms (NO3/TN ratio > 0.50) were more strongly responsive to the N input rate compared to streams dominated by other N forms. NO3 proportional contribution increased with N inputs, supporting N saturation-enhanced NO3 export to aquatic ecosystems. By combining information about N inputs with climatic and landscape factors, random forest models of stream N concentrations explained 70, 58, and 60% of the spatial variation in stream concentrations of TN, dissolved inorganic N, and total organic N, respectively. The strength and direction of relationships between watershed drivers and stream N concentrations and forms varied with N input intensity. Model results for high N input watersheds not only indicated potential contributions from contaminated groundwater to high stream N concentrations but also the mitigating role of wetlands.


Assuntos
Água Subterrânea , Rios , Ecossistema , Monitoramento Ambiental , Nitrogênio/análise , Estações do Ano
19.
Artigo em Inglês | MEDLINE | ID: mdl-34071994

RESUMO

After years of water environment improvement, China's water quality has improved to some extent in recent years. However, different water areas have different characteristics of water pollution. The paper used mathematical models to investigate the influence of different parameters on the water quality of Xuanwu Lake, China. The predominant focus was on the nutrients concentration due to changing the amount of pollutants, degradation coefficient, water diversion discharge and diffusion coefficient. The results showed that the amount of pollutants had the most significant impact, followed by the degradation coefficient. The total phosphorus and total nitrogen concentrations of Xuanwu Lake increased with the increase of the amount of pollutants. The water quality of Xuanwu Lake decreased significantly with the increase of degradation coefficient. Increasing the water diversion discharge will not only make a big difference in water quality, but it will also worsen the water quality. The effect of the amount of pollutants on Xuanwu Lake total phosphorus and total nitrogen is 4.1 and 5.7 times that of water diversion discharge. The influence of total phosphorus and total nitrogen in the degradation coefficient scheme is 3.5 and 6.2 times that of the water diversion discharge scheme. The diffusion coefficient has almost no effect on the water quality of Xuanwu Lake. From the practical difficulty and implementation effect of water environment improvement, the order of water quality improvement effect from good to bad is as follows: the amount of pollutants scheme, degradation coefficient scheme, water diversion scheme, diffusion coefficient scheme. Under the circumstance of limited water diversion, the lake will effectively improve the water quality. Reducing the discharge of pollutants is the fundamental measure to control water environment problems, and water diversion is an auxiliary measure to improve the water ecology. It will become a trend to combine the reduction of pollutant discharge and water transfer for water environment improvement. This paper is of significance for improving the water quality of Xuanwu Lake, and it also provides a scientific method for water environment improvement of water diversion projects.


Assuntos
Lagos , Poluentes Químicos da Água , China , Monitoramento Ambiental , Eutrofização , Nitrogênio/análise , Fósforo/análise , Poluentes Químicos da Água/análise , Qualidade da Água
20.
Mar Environ Res ; 169: 105397, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34157564

RESUMO

Microbial densities, functional genes, and their responses to environment factors have been studied for years, but still a lot remains unknown about their interactions with each other. In this study, the abundances of 7 nitrogen cycling genes in the sediments from Hangzhou Bay were analyzed along with bacterial and archaeal 16S rRNA abundances as the biomarkers of their densities. The amount of organic matter (OM) and total nitrogen (TN) strongly positively correlated with each other and microbial densities, while total phosphate (TP) and ammonia-nitrogen (NH3-N) did not. Most studied genes were density suppressed, while nirS was density stable, and nosZ and hzo were density irrelevant. This suggests eutrophication could limit inorganic nitrogen cycle pathways and the removal of nitrogen in the sediment and emit more greenhouse gases. This study provides a new insight of microbial community structures, functions and their interactions in the sediments of eutrophic bays.


Assuntos
Archaea , Baías , Archaea/genética , China , Pool Gênico , Sedimentos Geológicos , Lagos , Nitrogênio/análise , Ciclo do Nitrogênio , RNA Ribossômico 16S/genética
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