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1.
Water Res ; 191: 116814, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33461081

RESUMO

Time lags between anthropogenic nitrogen inputs and their impacts to nitrate levels cause a misunderstanding for sources and subsequently misguide the groundwater management.We investigated the hydrochemical data of groundwater samples (n = 172 from 49 wells) with chlorofluorocarbons (CFCs)-based groundwater age dating and stable N (δ15N) and O isotopes (δ18O) of nitrate to assess the legacy effect of livestock farming to groundwater in an agricultural area where intensive livestock farming started in the 1970s and illegal dumping of manure wastewater in a lava cave was revealed in 2015. Approximately 90% of the groundwater samples had nitrate concentrations exceeding the natural threshold (5.5 mg/L NO3-) for nitrate contamination and 34% exceeded the World Health Organization's guideline for drinking water quality (44.3 mg/L), indicating severe nitrate contamination. The δ15NNO3 values (5.5 to 24.3‰) in groundwater exceeding the threshold of nitrate showed that livestock manure was a major nitrate source, while ammonium fertilizer also seemed influential given the δ15NNO3 values in the overlapping fields of N sources. Factor analysis of hydrochemical data also supported nitrate contamination by manure as well as by plant farming in the study area. Based on the spatial distribution of nitrate levels and δ15NNO3, livestock farming affected nitrate contamination by illegal manure dumping in the leakage cave. According to a Bayesian mixing model, the contribution of manure wastewater was 33.5 to 81.8% as of 2015-2018, with the rest from fertilizers. Meanwhile, the groundwater ages showed negative correlations with both nitrate levels (r = -0.90) and δ15NNO3 values (r = -0.74) on a log scale, consistent with the increasing N release from livestock farming since the 1960s. In particular, the median value of δ15NNO3 rapidly increased to 9.2‰ in groundwater recharged between the late 1970s and early 1990s when N production exponentially increased, implying a significant effect of livestock farming after the 1980s. Groundwater quality is expected to deteriorate over the next several decades based on the groundwater ages (> 23.5 years), the increased N production from livestock farming, and the legacy effect of N. Long-term groundwater management plans (> 25 years) are required to decrease N loads in the study area, because it takes time for management practices to take effect. The study results are a good reference for groundwater management in regions with a source shift to livestock farming under intensive livestock production systems. Moreover, the chronological study using historical N production, groundwater age data, and dual nitrate isotopes can be applied to other regions with multiple N sources and their shifting for identifying sources and estimating time lags.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Agricultura , Animais , Teorema de Bayes , Monitoramento Ambiental , Gado , Nitratos/análise , Isótopos de Nitrogênio/análise , República da Coreia , Água , Poluentes Químicos da Água/análise , Abastecimento de Água
2.
Environ Pollut ; 272: 116410, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33433349

RESUMO

Nitrogen (N) pollution and the resulting eutrophication can have deleterious consequences on estuaries, such as hypoxia, fish kills, and loss of biotic diversity. An understanding of N sources and cycling in estuaries is fundamental to determining how to effectively manage these ecologically and commercially important areas. We applied a multiple-isotopic approach to examine the transformations and sources of the N pools in the Pearl River Estuary (PRE) during winter. The surface water in the West PRE was characterized by low salinity and high NO3-, while that in the east had high salinity and low NO3-. The NO3- in the West PRE was largely regulated by a conservative mixing process. In contrast, assimilation and nitrification dominated in the East PRE, which was attributed to the long water-residence time. For the first time, the source contributions of NO3- and NH4+ were estimated by isotope mixing models. Our results suggest that river discharge and nitrification contributed 81% and 12% to the NO3- pool, respectively. A major portion (68%) of the NH4+ was from river discharge, with the remainder likely from sewage and the aquitard-aquifer system. Our study demonstrates that internal nitrification can potentially be of pivotal importance in determining the NO3- level in an estuary and its export to coastal waters.


Assuntos
Estuários , Poluentes Químicos da Água , China , Monitoramento Ambiental , Nitratos/análise , Nitrogênio/análise , Isótopos de Nitrogênio/análise , Rios , Poluentes Químicos da Água/análise
3.
Water Res ; 188: 116537, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33126005

RESUMO

Nitrate (NO3-) pollution adversely impacts surface and groundwater quality. In recent decades, many countries have implemented measures to control and reduce anthropogenic nitrate pollution in water resources. However, to effectively implement mitigation measures at the origin of pollution,the source of nitrate must first be identified. The stable nitrogen and oxygen isotopes of NO3- (ẟ15N and ẟ18O) have been widely used to identify NO3- sources in water, and their combination with other stable isotopes such as boron (ẟ11B) has further improved nitrate source identification. However, the use of these datasets has been limited due to their overlapping isotopic ranges, mixing between sources, and/or isotopic fractionation related to physicochemical processes. To overcome these limitations, we combined a multi-isotopic analysis with fecal indicator bacteria (FIB) and microbial source tracking (MST) techniques to improve nitrate origin identification. We applied this novel approach on 149 groundwater and 39 surface water samples distributed across Catalonia (NE Spain). A further 18 wastewater treatment plant (WWTP) effluents were also isotopically and biologically characterized. The groundwater and surface water results confirm that isotopes and MST analyses were complementary and provided more reliable information on the source of nitrate contamination. The isotope and MST data agreed or partially agreed in most of the samples evaluated (79 %). This approach was especially useful for nitrate pollution tracing in surface water but was also effective in groundwater samples influenced by organic nitrate pollution. Furthermore, the findings from the WWTP effluents suggest that the use of literature values to define the isotopic ranges of anthropogenic sources can constrain interpretations. We therefore recommend that local sources be isotopically characterized for accurate interpretations. For instance, the detection of MST inferred animal influence in some WWTP effluents, but the ẟ11B values were higher than those reported in the literature for wastewater. The results of this study have been used by local water authorities to review uncertain cases and identify new vulnerable zones in Catalonia according to the European Nitrate Directive (91/676/CEE).


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Animais , Monitoramento Ambiental , Nitratos/análise , Isótopos de Nitrogênio/análise , Espanha , Poluentes Químicos da Água/análise
4.
Sci Total Environ ; 757: 143985, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33321341

RESUMO

Biological time series datasets provide an unparalleled opportunity to investigate regional and global changes in the marine environment. Baleen whales are long-lived sentinel species and an integral part of the marine ecosystem. Increasing anthropogenic terrestrial and marine activities alter ocean systems, and such alterations could change foraging and feeding behavior of baleen whales. In this study, we analyzed δ13C and δ15N of baleen whale earplugs from three different species (N = 6 earplugs, n = 337 laminae) to reconstruct the first continuous stable isotope profiles with a six-month resolution. Results of our study provide an unprecedented opportunity to assess behavioral as well as ecological changes. Abrupt shifts and temporal variability observed in δ13C and δ15N profiles could be indicative of behavior change such as shift in foraging location and/or trophic level in response to natural or anthropogenic disturbances. Additionally, five out of six individuals demonstrated long-term declining trends in δ13C profiles, which could suggest influence of emission of depleted 13CO2 from fossil fuel combustion referred to as the Suess effect. After adjusting the δ13C values of earplugs for the estimated Suess effect and re-evaluating δ13C profiles, significant decline in δ13C values as well as different rate of depletion suggest contribution of other sources that could impact δ13C values at the base of the food web.


Assuntos
Ecossistema , Baleias , Animais , Isótopos de Carbono/análise , Dispositivos de Proteção das Orelhas , Isótopos de Nitrogênio/análise
5.
Chemosphere ; 263: 127915, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297012

RESUMO

Nitrate (NO3-) has become recognized as the most important water-soluble ion in fine particulate (PM2.5), and has been proposed as a driving factor for regional haze formation. However, nitrate formation mechanisms are still poorly understood. In this study, PM2.5 samples were collected from September 2017 to August 2018 in Shijiazhuang, a city located on the North China Plain, and NO3-concentration, δ18O-NO3- and δ15N-NO3- values in PM2.5 were analyzed. NO3- concentrations increased as PM2.5 levels increased during both polluted and non-polluted days over the entire year. δ18O-NO3- values during cold months (63.5-103‰) were higher than those during warm months (50.3-85.4‰), these results suggested that the nitrate formation pathways shifted from the NO2 + OH (POH) in warm months to the N2O5 + H2O (PN2O5) and NO3 + VOCs (PNO3) pathways in cold months. Especially during cold months, δ18O-NO3- values increased from 65.2-79.9‰ to 80.7-96.2‰ when PM2.5 increased from ∼25 to >100 µg/m3, but when PM2.5 > 100 µg/m3, there were relatively small variations in δ18O-NO3-. These results suggested that nitrate formation pathways changed from POH to PN2O5 and PNO3 pathways when PM2.5 < 100 µg/m3, but that PN2O5 and PNO3 dominated nitrate production when PM2.5 > 100 µg/m3. Higher δ15N-NO3- values in warm months (-11.8-13.8‰) than in cold months (-0.7-22.6‰) may be attributed to differences in NOx emission sources and nitrogen isotopic fractionation among NOx and NO3-. These results provide information on the dual isotopic compositions of nitrate to understand nitrate formation pathways under different PM2.5 levels.


Assuntos
Monitoramento Ambiental , Nitratos , China , Cidades , Nitratos/análise , Isótopos de Nitrogênio/análise , Material Particulado/análise
6.
Chemosphere ; 263: 128219, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297176

RESUMO

Quantitative identification of non-point sources of nitrate in urban channels plays a critical role in effective nutrient management in urban regions. This is an emerging issue due to fast urbanization and the resultant complicated hydrological and hydraulic conditions in urban areas. In this study, we examine spatial-temporal characteristics of nitrogen concentration in urban channels based on dense in-situ samplings during a one-year period over a small urban catchment in China. We quantitatively identify nitrate sources into urban channels based on dual-isotope analyses and Bayesian isotope mixing model. Results show that nitrogen concentration peaks in winter as well as in urban channels and land surfaces in the urban core region. Sewage (47%) is the dominate contributor to NO3--N in urban channels, followed by NH4+ in fertilizer (30%) as the second contributor. Sewage (NH4+ in fertilizer) contributes more NO3--N to channels in winter (summer) with the proportion of 65% (44%), and more NO3--N to urban core (suburban) channels with the proportion of 59% (42%). The rainfall and distribution of rainwater drains explain the monthly and spatial variations of contribution of NO3--N sources well, respectively. In addition, less NO3--N in the urban channels derives from nitrification, which is consistent with the results of high properties of NH4+-N/TN in this region. Our results highlight the key roles of land use types and rainfall in NO3--N source apportionment, and provide support for the nitrogen management practices in urbanized regions.


Assuntos
Nitratos , Poluentes Químicos da Água , Teorema de Bayes , China , Monitoramento Ambiental , Esterco/análise , Nitratos/análise , Isótopos de Nitrogênio/análise , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 750: 141667, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32871370

RESUMO

Stable isotopes are increasingly used to detect and understand the impacts of environmental changes on riverine ecological properties. The δ13C and δ15N signatures of fish with different feeding habits were measured in a large subtropical river to evaluate how fish isotopic niches respond to environmental gradients and human disturbance. From basal resources to fish consumers, the high values of epilithic periphyton (biofilm) δ13C and suspended particulate organic matter δ15N concurrently determined the niche ranges and space (e.g., convex hull area) of fish communities. Along a longitudinal gradient (except in the industrial zone), the number of fish trophic guilds identified by Bayesian ellipses continuously increased; meanwhile, higher trophic diversity and less redundancy were observed near the lower reaches and estuary. Variance inflation factors were estimated to detect the multicollinearity of 40 environmental variables, 14 of which were selected as indicators. Relative importance (RI) analysis was used to evaluate the explanatory power of these indicators for the spatial variation in isotopic niche metrics; the results showed that riffle habitat area, water nitrate concentration, gravel-cobble substrate, and riparian buffer width were the 4 key environmental indicators (average RI > 12%) that determined the longitudinal pattern of fish isotopic niches. These findings suggested that community-level δ13C signatures are more responsive to changes in habitats (e.g., riffle) and substrates (e.g., gravel-cobble) supporting the productivity of autochthonous diatoms while δ15N signatures respond to water quality altered by nitrogen pollution from manure-fertilized farming and poultry livestock effluent. Furthermore, δ15N may be more robust and interpretable than δ13C as an isotopic indicator of ecosystem change in rivers exposed to multiple or complex anthropogenic stressors.


Assuntos
Ecossistema , Rios , Animais , Teorema de Bayes , Isótopos de Carbono/análise , China , Indicadores Ambientais , Monitoramento Ambiental , Humanos , Isótopos de Nitrogênio/análise
8.
Ying Yong Sheng Tai Xue Bao ; 31(10): 3559-3567, 2020 Oct.
Artigo em Chinês | MEDLINE | ID: mdl-33314847

RESUMO

Carbon and nitrogen stable isotope analysis was carried out on pelagic fishery organisms caught in light traps and falling nets in the central and western South China Sea in the spring of 2018. The stable isotope values of the sampled individuals were used to elucidate the isotopic variations for the pelagic fishery organisms, to classify species into trophic functional groups, and to compare the differences of trophic structure among the classified trophic functional groups. The results showed that among 23 fishery species the mean δ13C value of Coryphaena hippurus was the lowest (-17.58‰±0.21‰), and that of Grammistes sexlineatus was the highest (-19.86‰±0.33‰). The mean δ15N values ranged from 8.31‰ in Psenes cyanophrys to (12.46±0.74)‰ in Chirocentrus dorab. The continuous trophic spectrum indicated that the trophic level (TL) for the sampled pela-gic fishery organisms ranged from 3.01 to 4.23, of which 19 species (83% of the total) fell between TL 3.0 and 4.0. The 23 species of fishery organisms were classified into three trophic functional groups, i.e., plankton feeding functional group (PFFG), nekton feeding functional group (NFFG), and mixed feeding functional group (MFFG). The analysis of standard ellipse area (SEA) showed that the PFFG occupied the largest trophic niche width (SEA=1.56‰2), followed by the MFFG (SEA=0.99‰2) and NFFG (SEA=0.31‰2). The MFFG overlapped with PFFG and NFFG in the trophic niche, with a relative percentage of 17% and 26%, respectively. There was no overlap between PFFG and NFFG.


Assuntos
Carbono , Nitrogênio , Animais , Isótopos de Carbono/análise , China , Pesqueiros , Cadeia Alimentar , Humanos , Isótopos de Nitrogênio/análise
9.
Mar Pollut Bull ; 160: 111622, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33181920

RESUMO

Sedimentary nitrogen (SN) provenience and fate in surface and subsurface sediments collected from the Baltic Sea were assessed. SN and sedimentary organic carbon (SOC) concentrations, stable isotopic signatures (δ15NSN and δ13CSOC) and SOC/SN molar ratios, were determined in subsequent layers of twenty-four sediment cores dated with 210Pb/137Cs and fifty-seven surface sediments. Sedimentation rates in the range 66-736 g/m2yr-1 (0.05-0.34 cm/year) were measured. Prolonged incubation of sediments in the laboratory led to a 17-37% decrease of SN in surface sediments, and no SN loss in sediments deposited before 1940. Decrease of δ15NSN on incubation (1‰ on average), and gradients of δ15NSN, between recent - surface (3.5‰) vs. 100 years old - subsurface (2.1‰) sediments were attributed to varying contributions of labile nitrogen to the SN pool. Annual deposition of SN to sediment surface and burial in subsurface sediments amounted, respectively, to 5 ± 2 g/m2 and 3.5 ± 1 g/m2.


Assuntos
Sedimentos Geológicos , Nitrogênio , Carbono/análise , Isótopos de Carbono/análise , Monitoramento Ambiental , Nitrogênio/análise , Isótopos de Nitrogênio/análise
10.
Mar Pollut Bull ; 160: 111672, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33181945

RESUMO

The spatial and seasonal variations in resource use of the lacustrine shrimp Palaemon paucidens were investigated in three different Korean lagoon systems in June and October 2018 by measuring their carbon and nitrogen stable isotope ratios. P. paucidens had much higher δ13C values at the permanently open lagoon (PL) as compared to the intermittently open lagoons (ILs), revealing a disparity in resource utilization. Isotopic niches of the shrimp were relatively wider at the PL than at the ILs, suggesting a greater diversity of carbon pathways in the PL system. These results indicate that the degree of water exchange with the sea, associated with lagoon geomorphology, may be a major factor influencing resource availability for P. paucidens. Our findings suggest that the duration and degree of inlet opening may affect dietary variation at the population level, and may be one of the key components of sustainable management for coastal lagoon ecosystems.


Assuntos
Ecossistema , Palaemonidae , Animais , Isótopos de Carbono/análise , Isótopos de Nitrogênio/análise , República da Coreia , Estações do Ano
11.
Mar Environ Res ; 162: 105163, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33137597

RESUMO

Shallow coastal zones may provide cross-habitat nutrient subsidies for benthic communities offshore, as macrophyte matter can drift to deeper sediments. To study the relative importance of carbon and nutrient flows derived from different primary food sources in a coastal ecosystem, the diets of clam Macoma balthica, polychaete Marenzelleria spp. and mussel Mytilus trossulus were examined across environmental gradients in the northern Baltic Sea using a triple-isotope approach (i.e. 13C, 15N and 34S) and Bayesian mixing models (MixSIAR). Our results suggest that in shallow habitats, production from Fucus vesiculosus is the primary energy source for M. balthica. The proportion of macroalgae-derived matter in the diet of M. balthica and Marenzelleria spp. decreased following a depth gradient. Our models for M. trossulus indicate that the pelagic POM dominates its diet. Our results indicate a trophic connectivity between shallow macrophyte-dominated and deeper habitats, which receive significant amounts of nutrient subsidies from shallower areas.


Assuntos
Alga Marinha , Animais , Países Bálticos , Teorema de Bayes , Ecossistema , Cadeia Alimentar , Isótopos de Nitrogênio/análise
12.
Huan Jing Ke Xue ; 41(11): 4936-4947, 2020 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124237

RESUMO

The multi-environment media of water, surface soil and vadose zone soil samples were collected in the upstream of Miyun Reservoir, in the Luanping Basin of Chengde City, Hebei Province. The aim was to identify the pollution source, ratio, spatial distribution, migration, and transformation characteristics of nitrogen in groundwater. Hydrogeochemistry, soil total nitrogen, and dissolved nitrate nitrogen of vadose zone soil analysis and a multi isotope tracer technique of δ15 N-NO3 and δ18O-NO3, δ34S-SO4 and δ18O-SO4, δ14 C, combined with land-use type analysis and geostatistics, were used in the study. The results showed that nitrate was the main form of nitrogen in the groundwater of the Luanping Basin. The NO3- concentration of groundwater was significantly correlated with the land-use types of residential land and cultivated land where the nitrate pollution of shallow groundwater was mainly distributed. Of the groundwater samples, 13.79% exceeded the National Standard Ⅲ for Groundwater (GB/T 14848-2017) of NO3- concentration value, while the excess multiple was 1.04-3.86, and 37.93% of the groundwater samples exceeded the World Health Organization NO3- concentration standard value. The excess multiple was 1.08-6.83. The spatial variation of groundwater NO3- concentration, soil total nitrogen and surface soil dissolved nitrate nitrogen of vadose zone was affected by the combination of natural structural factors and anthropogenic factors. The source of groundwater nitrate was mainly from livestock manure and domestic sewage, followed by chemical fertilizer leaching. The nitrogen cycle in the aeration zone-groundwater-dominated nitrogen circulation in the groundwater runoff area of the piedmont basin was nitrification. These findings are highly significant for the prevention and remediation of groundwater pollution when viewing the basin system as an independent unit, and for studying the sources and fate of nitrate pollution in the water environment.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Monitoramento Ambiental , Nitratos/análise , Isótopos de Nitrogênio/análise , Poluentes Químicos da Água/análise
13.
Huan Jing Ke Xue ; 41(9): 4333-4344, 2020 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124315

RESUMO

Nitrogen plays a vital role in biological activities as the basic element of organic molecules and the main nutrient of soil. In the study of nitrogen pollution, the first step is to understand the transformation mechanism of various nitrogen forms. Based on the transformation process and the mechanism of nitrogen in the ecosystem, this review summarizes the research methods of nitrogen source analysis and nitrogen isotope fractionation in soil and water, and categorically reviews the applications of nitrogen source identification in surface water and groundwater. We showed that it is more effective to identify the sources of soil and water nitrogen pollution by combining hydrochemical methods with the multi-isotope approach. The importance of primary nitrogen sources should also be quantified to study groundwater pollution. A new approach to determine the source of oxygen atoms during nitrosation was also presented, and the enrichment principle of δ18O-NO3- during secondary oxidation was explained. Finally, the contribution of primary ammonium nitrogen to groundwater pollution was discussed, and innovative research ideas were provided.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Ecossistema , Monitoramento Ambiental , Nitratos/análise , Nitrogênio/análise , Isótopos de Nitrogênio/análise , Solo , Água , Poluentes Químicos da Água/análise
14.
Huan Jing Ke Xue ; 41(8): 3637-3645, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124337

RESUMO

Due to the vulnerability of karst hydrological systems, nitrate pollution in karst groundwater has become a global common and serious environmental problem. In order to ensure drinking water safety, it is very important to accurately identify groundwater nitrate sources. The groundwater hydrochemistry and δ15N-NO3- and δ18O-NO3- isotopes were analyzed in samples taken from a suburb of Chongqing:the Longfeng karst trough-valley, which is mainly affected by agricultural activities, and the Longche karst trough-valley, which is primarily affected by urbanization. The IsoSource model was then used to quantify the groundwater nitrate sources. The results showed that:① The NO3- concentration in groundwater ranged from 19.31 mg·L-1 to 37.01 mg·L-1(mean of 28.21 mg·L-1) in the Longfeng karst trough-valley, and from 2.15 mg·L-1 to 27.69 mg·L-1(mean of 10.31 mg·L-1) in the Longche karst trough-valley. The groundwater NO3- concentration exhibited an obvious seasonal variation in both valleys. ② The δ15N-NO3- and δ18O-NO3- isotopes in groundwater in the Longfeng karst trough-valley ranged from 3.29‰ to 11.03‰ (mean of 6.74‰) and 0.88‰ to 7.51‰ (mean of 3.18‰), respectively. In contrast, groundwater in the Longche karst trough-valley presented higher δ15N-NO3- and δ18O-NO3- values that ranged from 5.25‰ to 11.40‰ (mean of 7.95‰) and 2.90‰ to 19.94‰ (mean of 11.18‰), respectively. The lower values of δ15N-NO3- and δ18O-NO3- in groundwater in the Longfeng karst trough-valley suggest that groundwater NO3- was mainly sourced from agricultural N fertilizer, while the higher values of δ15N-NO3- and δ18O-NO3- in groundwater in the Longche karst trough-valley indicate that groundwater NO3- was primarily sourced from domestic sewage. Moreover, such δ15N-NO3- and δ18O-NO3- values in groundwater indicate that nitrification was the primary process for nitrogen conversion in both valleys. Meanwhile, significant seasonal differences in groundwater δ15N-NO3- and δ18O-NO3- were observed in both valleys; the δ15N-NO3- and δ18O-NO3- values were higher during the dry season (means of 8.83‰ and 2.79‰, respectively) than during the rainy season (means of 4.64‰ and 3.58‰, respectively) in the Longfeng karst trough-valley, whereas the δ15N-NO3- and δ18O-NO3- values were lower during the dry season (means of 9.79‰ and 14.56‰, respectively) than during the rainy season (means of 5.12‰ and 7.8‰, respectively) in the Longche trough-valley. This suggests that there were differences in the seasonal NO3- sources to groundwater in both valleys. During the rainy season, the groundwater NO3- concentration in the Longfeng karst trough-valley was mainly due to the nitrification of NH4+ in precipitation and fertilizer as well as organic nitrogen in soil, whereas during the dry season, the groundwater NO3- concentration primarily originated from domestic sewage. In contrast, the groundwater NO3- concentration in the Longche karst trough-valley primarily originated from domestic sewage in both seasons. ③ The results of the IsoSource model indicated that the nitrification of NH4+ from fertilizer and rainwater was the primary NO3- source to groundwater (44.63% of the total) in the Longfeng trough valley, and was followed by domestic sewage (29.5%), soil organic nitrogen (22.38%), and NO3- from rainwater and fertilizer (<10%). During the rainy season, the groundwater NO3- concentration was mainly due to the nitrification of NH4+ from fertilizer and rainwater (52.25% of the total) in Longfeng trough-valley, while groundwater NO3- concentration primarily originated from domestic sewage during the dry season (41% of the total). In contrast, the groundwater NO3- concentration was mainly from domestic sewage (36.17%) in Longche karst trough-valley, and was followed by the nitrification of NH4+ from fertilizer and rainwater (23.5%), soil organic nitrogen (22.5%), and NO3- from rainwater and fertilizer (<10%). The groundwater NO3- concentration in the Longche karst trough-valley primarily originated from domestic sewage in both seasons, and accounted for 47% and 25% during the rainy season and dry season, respectively.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Monitoramento Ambiental , Nitratos/análise , Isótopos de Nitrogênio/análise , Poluentes Químicos da Água/análise
15.
Environ Pollut ; 267: 115274, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32891045

RESUMO

Inorganic particulate nitrate (p-NO3-), gaseous nitric acid (HNO3(g)) and nitrogen oxides (NOx = NO + NO2), as main atmospheric pollutants, have detrimental effects on human health and aquatic/terrestrial ecosystems. Referred to as the 'Third Pole' and the 'Water Tower of Asia', the Tibetan Plateau (TP) has attracted wide attention on its environmental changes. Here, we evaluated the oxidation processes of atmospheric nitrate as well as traced its potential sources by analyzing the isotopic compositions of nitrate (δ15N, δ18O, and Δ17O) in the aerosols collected from the Mt. Everest region during April to September 2018. Over the entire sampling campaigns, the average of δ15N(NO3-), δ18O(NO3-), and Δ17O(NO3-) was -5.1 ± 2.3‰, 66.7 ± 10.2‰, and 24.1 ± 3.9‰, respectively. The seasonal variation in Δ17O(NO3-) indicates the relative importance of O3 and HO2/RO2/OH in NOx oxidation processes among different seasons. A significant correlation between NO3- and Ca2+ and frequent dust storms in the Mt. Everest region indicate that initially, the atmospheric nitrate in this region might have undergone a process of settling; subsequently, it got re-suspended in the dust. Compared with the Δ17O(NO3-) values in the northern TP, our observed significantly higher values suggest that spatial variations in atmospheric Δ17O(NO3-) exist within the TP, and this might result from the spatial variations of the atmospheric O3 levels, especially the stratospheric O3, over the TP. The observed δ15N(NO3-) values predicted remarkably low δ15N values in the NOx of the sources and the N isotopic fractionation plays a crucial role in the seasonal changes of δ15N(NO3-). Combined with the results from the backward trajectory analysis of air mass, we suggest that the vehicle exhausts and agricultural activities in South Asia play a dominant role in determining the nitrate levels in the Mt. Everest region.


Assuntos
Monitoramento Ambiental , Poluentes Químicos da Água , Ásia , Ecossistema , Nitratos/análise , Isótopos de Nitrogênio/análise , Óxidos de Nitrogênio/análise , Poluentes Químicos da Água/análise
16.
Proc Natl Acad Sci U S A ; 117(33): 20044-20051, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32747534

RESUMO

Carbon and nitrogen isotope ratios in hair sampled from 65 communities across the central and intermountain regions of the United States and more intensively throughout 29 ZIP codes in the Salt Lake Valley, Utah, revealed a dietary divergence related to socioeconomic status as measured by cost of living, household income, and adjusted gross income. Corn-fed, animal-derived proteins were more common in the diets of lower socioeconomic status populations than were plant-derived proteins, with individual estimates of animal-derived protein diets as high as 75%; United States towns and cities averaged 57%. Similar patterns were seen across the socioeconomic status spectrum in the Salt Lake Valley. It is likely that corn-fed animal proteins were associated with concentrated animal-feeding operations, a common practice for industrial animal production in the United States today. Given recent studies highlighting the negative impacts of animal-derived proteins in our diets, hair carbon isotope ratios could provide an approach for scaling assessments of animal-sourced foods and health risks in communities across the United States.


Assuntos
Isótopos de Carbono/análise , Dieta/economia , Proteínas na Dieta/análise , Cabelo/química , Isótopos de Nitrogênio/análise , Animais , Proteínas na Dieta/economia , Proteínas na Dieta/metabolismo , Cabelo/metabolismo , Humanos , Isótopos de Nitrogênio/metabolismo , Classe Social , Estados Unidos , Utah
17.
Environ Pollut ; 266(Pt 3): 115142, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32750525

RESUMO

Chemical warfare agents (CWA) dumped worldwide in all types of aquatic reservoirs pose a potential environmental hazard. Leakage of CWAs from eroding containers at dumping sites had been observed, and their presence in the tissues of aquatic animals was confirmed. However, the ecological effects of CWA have not yet been studied. In standardized laboratory bioassays, we tested if sublethal concentration of Clark I, an arsenic based CWA, can affect life histories (somatic growth rate, fecundity, size at maturity), population growth rate and stable isotope signatures of a keystone crustacean grazer Daphnia magna. We found that the life histories and fitness of daphnids reared in the presence of Clark I differed from those reared in Clark-free conditions. The effects were observed when Clark I concentrations were no less than 5 µg×L-1. With increasing concentrations of the tested CWA, all of the tested parameters decreased linearly. The finding indicates that even sublethal concentrations of Clark I can affect crustacean populations, which should be taken into account when assessing the environmental risks of this particular CWA. We found intraspecific diversity in susceptibility to Clark I, with some clones being significantly less vulnerable than others. We also found that in the presence of Clark I, the ratio of heavy and light isotopes of nitrogen in the bodies of daphnids was affected - daphnids exhibited δ15N enrichment with increasing concentrations of this CWA. The isotopic composition of carbon was not affected by the presence of Clark I. The nitrogen isotopic signature may be used as an indicator of stress in zooplankton exposed to the presence of toxic xenobiotics.


Assuntos
Arsênico , Substâncias para a Guerra Química , Poluentes Químicos da Água/análise , Animais , Daphnia , Isótopos de Nitrogênio/análise
18.
Mar Pollut Bull ; 159: 111477, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32750595

RESUMO

Stable isotopic composition of carbon (δ13CPOM) and nitrogen (δ15NPOM) in the particulate organic matter (POM) is used to identify sources of organic carbon and nutrients using monthly time-series observation in the coastal Bay of Bengal (BoB). The hydrographic structure indicates that the coastal BoB is influenced by coastal upwelling during March-May, advection of peninsular river discharge during June to September and glacial (Ganges) river discharge during October to December due to reversing of East India Coastal Currents (EICC). C/N ratios in POM were mostly higher values than Redfield ratio in the study region indicating possible contribution of terrestrial origin. Enriched δ13CPOM were found during March-May associated with coastal upwelling indicating major contribution of POM from the in situ production while lower values were noticed during June to September followed by October to December indicating influence of terrestrial sources. δ15NPOM displayed strong inverse relation with salinity and linear relation with Chl-a suggesting that anthropogenic nutrients from the land increased coastal phytoplankton biomass. δ15NPOM linearly decreased with increase in distance from the coast and reached to the typical offshore value of 6-6.5‰ indicating that terrestrial nutrients influence was spread up to a distance of 15 to 20 km from the coast in the study region. Our study suggested that coastal waters are influenced by terrestrial/anthropogenic nutrients and its impact can be noticed up to 15 to 20 km from the coast and its impact on Biodiversity Beyond National Jurisdiction may be negligible than hitherto hypothesized.


Assuntos
Baías , Monitoramento Ambiental , Isótopos de Nitrogênio/análise , Nutrientes , Rios
19.
Environ Pollut ; 265(Pt B): 115105, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32806467

RESUMO

Sulfate (SO42-) contamination in groundwater and surface water is an environmental problem of widespread concern. In this study, we combined stable isotope analyses of SO42- (δ34S and δ18O) and water (δ2H and δ18O) with a Bayesian mixing model (SIAR), for the first time, to identify sources and transformation of SO42- in an area of northern China with multiple potential sources of pollution. The overall values of δ34S and δ18O-SO42- ranged from 1.3‰ to 16.3‰ and -3.8‰-8.8‰ in groundwater, and from -1.1‰ to 9.3‰ and 2.7‰-9.2‰ in surface waters, respectively. Analyses of SO42- isotopes and water chemistry indicated that SO42- in groundwater and surface water mainly originated from mixing of oxidation of sulfate, sewage, chemical fertilizers, dissolution of evaporite and precipitation. There was no significant correlation between δ34S and δ18O and SO42- concentration in groundwater, indicating that bacterial sulfate reduction did not affect the SO42- isotopic composition. SIAR model showed the main sources of SO42- in groundwater and surface water comprised oxidation of sulfide minerals and sewage. In groundwater, oxidation of sulfide minerals and sewage accounted for 37.5-44.5% and 35.5-42.7% of SO42-, respectively. In regard to surface waters, the contribution of oxidation of sulfide minerals to SO42- was higher in the wet season (31.8 ± 9.9%) than in the intermediate (22.4 ± 7.8%) and dry (20.9 ± 8.2%) seasons, but the contribution proportion of sewage was slightly lower in the wet season (19.9 ± 8.5%) than in the intermediate (23.8 ± 8.7%) and dry (24.2 ± 8.5%) seasons. This study indicates that it is necessary for local government to improve the treatment infrastructure for domestic sewage and optimize methods of agricultural fertilization and irrigation to prevent SO42- contamination of groundwater and surface water.


Assuntos
Monitoramento Ambiental , Poluentes Químicos da Água/análise , Teorema de Bayes , China , Nitratos/análise , Isótopos de Nitrogênio/análise , Sulfatos
20.
J Environ Manage ; 274: 111197, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32798850

RESUMO

The Lancang River in China is the headwater of the Mekong River. The impacts of reservoirs on the water, sediment and nutrient trapping in the Lancang River have attracted considerable attention, both locally and abroad. In this research, watershed-scale nitrogen load and nitrate sources along the Lancang River upstream in free-flowing reaches (FFRs) and downstream regulated reaches (RRs) were analyzed using stable nitrogen and oxygen isotopes. The results showed that the nitrogen nutrient (TN, NO3- and NH4+) concentration increased from upstream to downstream along the Lancang River, and the highest values come from large-scale urban samples rather than the reservoirs. Compared to other large rivers in China, such as the Yangtze River, Yellow River and Yalu Tsangpo River, nitrogen nutrient content in the Lancang River is at low level. The nitrate concentration ranged from 0.14 mg/L to 0.63mg/Land increased significantly downstream. The isotopic values ranged from 2.8‰ to 5.2‰ for δ15N-NO3- and from 4‰ to 8.5‰ for δ18O-NO3- along the river, and the δ15N-NO3- value rose significantly downstream. According to the nitrogen and oxygen isotope approach, soil organic nitrogen mineralization was the main source of the nitrate with an average of 51% contribution; domestic sewage was the second largest contributor with an average of 33% but increase downstream, likely due to the significantly larger population in the downstream region. Furthermore, the nitrate concentration decreased and δ15N- and δ18O-NO3- enriched in the Nuozhadu reservoir, indicating that the reservoir may enhance nitrate consumption and reduce nitrogen pollution to downstream reaches. The results provide a perspective of nitrogen nutrient for the trans-border river management and more insight researches are called for understanding the controversial nutrient transport topic in this region.


Assuntos
Nitrogênio/análise , Poluentes Químicos da Água/análise , China , Monitoramento Ambiental , Nitratos/análise , Isótopos de Nitrogênio/análise , Isótopos de Oxigênio/análise
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