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1.
Chemosphere ; 242: 125273, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896195

RESUMO

Atmospheric processing may significantly increase solubility of iron in mineral dust, but the effects of heterogeneous reactions on iron solubility have been poorly understood. In this work, we investigated heterogeneous reaction of NO2 (15 ±â€¯1 and 2.5 ±â€¯0.1 ppmv, equal to ∼3.7 × 1014 and ∼6.2 × 1013 molecule cm-3) with hematite, magnetite and goethite at different relative humidities (RH, 0-90%), and changes in particulate nitrate and soluble iron due to heterogeneous reaction with NO2 were quantified as a function of time (up to 24 h). After reaction with 2.5 ±â€¯0.1 ppmv NO2 for 24 h (or less time), hematite and magnetite were fully saturated, while goethite was only partly deactivated. Nitrate yield was largest for goethite, and the mass ratio of formed nitrate to unreacted mineral only reached ∼1% or less after 24 h reaction. All the three minerals showed low reactivities towards NO2, and the average reactive uptake coefficients of NO2 in the first 3 h were found to be < 5 × 10-8. In addition, the increase in iron solubility was found to be small and in some cases even insignificant for the three minerals after heterogeneous reaction with NO2 for 24 h. Overall, the impacts of heterogeneous reaction of NO2 with hematite, magnetite and goethite on nitrate aerosol formation and iron solubility could be very limited.


Assuntos
Compostos Férricos/química , Óxido Ferroso-Férrico/química , Compostos de Ferro/química , Ferro/química , Minerais/química , Nitratos/análise , Óxidos de Nitrogênio/química , Aerossóis , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Poeira/análise , Modelos Químicos , Solubilidade
2.
Ecotoxicol Environ Saf ; 187: 109855, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31689622

RESUMO

A calcium precipitating and denitrifying bacterium H12 was used to investigate the F- removal performance and mechanism. The results showed that the strain H12 reduced 85.24% (0.036 mg·L-1·h-1) of F-, 62.43% (0.94 mg·L-1·h-1) of Ca2+, and approximately 100% of NO3- over 120 h in continuous determination experiments. The response surface methodology analysis demonstrated that the maximum removal efficiency of F- was 88.98% (0.062 mg·L-1·h-1) within 72 h under the following conditions: the initial Ca2+ concentration of 250.00 mg·L-1, pH of 7.50, and the initial C4H4Na2O4·6H2O concentration of 800.00 mg·L-1. The scanning electron microscopy images, the X-ray photoelectron spectroscopy, and X-ray diffraction results suggested the following removal mechanism of F-: (1) the bacteria, as the nucleation site, were encapsulated by bioprecipitation to form biological crystal seeds; (2) Biological crystal seeds adsorbed F- to form Ca5(PO4)3F and CaF2; (3) Under the induction of bacteria, calcium, fluoride and phosphate coprecipitated to form Ca5(PO4)3F and CaF2. In addition, the gas chromatography data indicated that F- had little or no effect on the gas composition during denitrification, and the fluorescence spectroscopy analysis also proved that the extracellular polymeric substance (protein) is the site of bioprecipitation nucleation.


Assuntos
Acinetobacter/crescimento & desenvolvimento , Cálcio/análise , Fluoretos/análise , Água Subterrânea/química , Nitratos/análise , Poluentes Químicos da Água/análise , Acinetobacter/metabolismo , Biodegradação Ambiental , Cálcio/metabolismo , Desnitrificação , Matriz Extracelular de Substâncias Poliméricas/metabolismo , Fluoretos/metabolismo , Nitratos/metabolismo , Poluentes Químicos da Água/metabolismo
3.
J Sci Food Agric ; 100(2): 540-550, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31523826

RESUMO

BACKGROUND: Root-shoot ratio plays an important role in mulching effects on increases in maize kernel dry weight and grain yield. RESULTS: We examined the effects of plastic film mulching with fertigation on soil nitrate, soil Olsen-P, aboveground and belowground growth, grain filling, and yield of maize. The 2-year research was conducted in a field with a subsoil sand layer (FSS) and in a field without a subsoil sand layer (FNS) in the Hetao Irrigation District, northwest China. Treatments included two levels of plastic film mulching (FM, fully mulched; PM, partially mulched with a cover ratio of 60%), and a non-mulched (NM) control. Mulching methods significantly increased soil NO3 -N concentrations (SNCs) in the main root zone in FSS, but not in FNS. Mulching significantly increased root length density in the 0-40 cm soil layer. Mulching increased brace roots emergence by 20.2% under full, and by 9.9% under partial mulching, accelerating soil phosphorus use in the surface soil layer. Mulching increased grain yield in spring maize via enhancing base stem diameter, leaf area, and relative chlorophyll content, decreased the ratio of surface root area to leaf area, and improved kernel dry weight increase. CONCLUSIONS: A high proportion of base fertilizer to total fertilizer input resulted in nutrient deficiency during reproductive stage in fertigated maize, therefore, applying a portion of base fertilizer after the maize elongation stage is recommended for a further yield increase of mulched fertigated maize. © 2019 Society of Chemical Industry.


Assuntos
Produção Agrícola/métodos , Raízes de Plantas/crescimento & desenvolvimento , Zea mays/crescimento & desenvolvimento , China , Produção Agrícola/instrumentação , Fertilizantes/análise , Nitratos/análise , Nitratos/metabolismo , Nutrientes/análise , Nutrientes/metabolismo , Raízes de Plantas/metabolismo , Plásticos/análise , Solo/química , Água/análise , Água/metabolismo , Zea mays/metabolismo
4.
Environ Monit Assess ; 191(12): 779, 2019 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-31784811

RESUMO

This work aims to evaluate the different water sources available in Mahayel Aseer, KSA, chemically, toxicology and microbiologically. Several water samples, such as tap water, differentially desalinated water and bottled water, were analysed. Moreover, different metal ions and anions, including sodium, potassium, calcium, lead, cadmium, manganese, bicarbonate, fluoride, chloride, sulphate, nitrate and nitrite, were evaluated and assessed for human health. Bacterial and fungal pollutions arising from various water sources were also investigated. This study was conducted on polymer bottles and the best storage conditions. In order to acquire purified water safe for human consumption, certain recommendations pertaining to the steps of water treatment can be recommended.


Assuntos
Água Potável , Substâncias Perigosas , Poluentes Químicos da Água , Água , Ânions/análise , Cálcio/análise , Água Potável/química , Substâncias Perigosas/análise , Substâncias Perigosas/toxicidade , Humanos , Minerais/análise , Nitratos/análise , Nitritos/análise , Arábia Saudita , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade , Abastecimento de Água
5.
Environ Monit Assess ; 191(12): 768, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31761967

RESUMO

Deterioration of groundwater quality due to the introduction of pollutants from natural and anthropic sources has become a major environmental issue. We tested three methodologies in assessing groundwater quality and intrinsic aquifer vulnerability in the Agro-Aversano area (Southern Italy). A geographic information system (GIS)-based groundwater quality index (GQI) was realized to assess groundwater quality for drinking and irrigation use and, in parallel, standard SINTACS was applied to evaluate the intrinsic vulnerability of the aquifer. Nitrate concentrations and sodium absorption ratio (SAR) in groundwater samples were used to verify the reliability of vulnerability data. GQI analysis pointed to a general poor quality of groundwater both for drinking and irrigation use, especially in sub-urban areas. The spatial pattern of water quality from GQI analysis was positively related to nitrate and fluoride concentrations for drinking use and to bicarbonate and sodium concentrations for irrigation use, whose levels exceeded the WHO and FAO recommended thresholds, respectively. Standard SINTACS was found to be inadequate for describing the aquifer state, its results showing no correlation with nitrate concentration or SAR. Because of this inconsistency, we tested a novel approach combining GQI with SINTACS analysis. Results showed positive correlation with nitrate (r = 0.63) and SAR (r = 0.64) contents, thus pointing to combined SINTACS-GQI as a more reliable approach than standard methodologies.


Assuntos
Agricultura , Água Potável , Água Subterrânea , Qualidade da Água , Água Potável/normas , Monitoramento Ambiental/métodos , Fluoretos/análise , Sistemas de Informação Geográfica , Água Subterrânea/análise , Água Subterrânea/normas , Itália , Minerais/análise , Nitratos/análise , Reprodutibilidade dos Testes , Poluentes Químicos da Água/análise , Abastecimento de Água/normas
6.
Environ Sci Pollut Res Int ; 26(32): 33702-33714, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31595410

RESUMO

In this study, we aimed at determining greenhouse gas (GHG) (CO2, CH4, and N2O) fluxes exchange between the soil collected from sites dominated by different vegetation types (Calamagrostis epigeios, Phragmites australis, and Carex schnimdtii) in nitrogenous loaded riparian wetland and the atmosphere. The intact soil columns collected from the wetland were incubated in laboratory and continuously treated with [Formula: see text]-enriched water simulating downward surface water percolating through the soil to become groundwater in a natural system. This study revealed that the soil collected from the site dominated by C. epigeios was net CO2 and N2O sources, whereas the soil from P. australis and C. schnimdtii were net sinks of CO2 and N2O, respectively. The soil from the site dominated by C. schnimdtii had the highest climate impact, as it had the highest global warming potential (GWP) compared with the other sites. Our study indicates that total organic carbon and [Formula: see text] concentration in the soil water has great influence on GHG fluxes. Carbon dioxide (CO2) and N2O fluxes were accelerated by the availability of higher [Formula: see text] concentration in soil water. On the other hand, higher [Formula: see text] concentration in soil water favors CH4 oxidation, hence the low CH4 production. Temporally, CO2 fluxes were relatively higher in the first 15 days and reduced gradually likely due to a decline in organic carbon. The finding of this study implies that higher [Formula: see text] concentration in wetland soil, caused by human activities, could increase N2O and CO2 emissions from the soil. This therefore stresses the importance of controls of [Formula: see text] leaching in the mitigation of anthropogenic N2O and CO2 emissions.


Assuntos
Monitoramento Ambiental , Gases de Efeito Estufa/análise , Nitratos/análise , Áreas Alagadas , Atmosfera , Dióxido de Carbono/análise , Clima , Aquecimento Global , Efeito Estufa , Água Subterrânea , Estudos Longitudinais , Metano/análise , Nitrogênio , Óxido Nitroso/análise , Poaceae , Solo
7.
Environ Pollut ; 255(Pt 1): 113062, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31622959

RESUMO

The major objective of the current study is to estimate the groundwater quality and identify the likely sources of contamination in Chandigarh, India. Total 80 groundwater samples were collected from different locations and at various depths. Further, physcio-chemical analysis was done to estimate pH, electrical conductivity (EC), total dissolved solids, total hardness (TH), total alkalinity (TA), Na+, K+, Cl-, SO42-, PO43- and NO3-. The groundwater samples collected from shallow water sources contain higher concentration of total dissolved salts. EC, TA, Cl-, TH, Na+, and K+ were found relatively higher in the shallow aquifer (<150 ft). Based on the location of pollution sources at the surface and consecutive geo-statistical distribution of physicochemical characteristics, this study suggests that non-scientific disposal of municipal solid waste, dumping of industrial waste and agricultural activities, in the nearby areas lead to the deterioration of groundwater of shallow aquifer. These observations were also confirmed using various water quality indices and outcomes of multivariate modeling, including principal component analysis. Health risk assessment for nitrates indicated that 29 groundwater samples pose non-carcinogenic health risk for children due to dermal and oral exposure. Hence, there is a need to establish a system for regularly assessing the groundwater quality to minimize public health risks.


Assuntos
Monitoramento Ambiental/métodos , Água Subterrânea/química , Poluentes Químicos da Água/análise , Qualidade da Água/normas , Agricultura , Criança , Humanos , Índia , Resíduos Industriais/análise , Nitratos/análise , Medição de Risco , Resíduos Sólidos/análise
8.
Environ Pollut ; 255(Pt 1): 113125, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31520903

RESUMO

Groundwater in the Chalk aquifer is an important water resource whose quality has degraded due to fertilizer and pesticide use. Atrazine, classified as a priority substance, has been one of the most applied pesticides and also one of the most frequently detected pesticides in groundwater. The present study investigated the transfer and degradation of atrazine in the unsaturated zone of the Chalk aquifer in Northern France. The study was conducted in an underground quarry (Saint-Martin-le-Noeud), which provides a direct access to the water table and intercepts the unsaturated zone at different depths. The lake and the ceiling percolation of 16 sites throughout the quarry were followed. For 16 sites, the percolating flow rate and lake level were measured and the lake water was sampled for nitrate, atrazine and deethylatrazine (DEA, main degradation product of atrazine) analysis over 2.5 years. High spatial variations in hydrodynamics (percolating flow rate and lake level) and in lake water quality (atrazine between 55±11 and 202±40 ng L-1 and DEA between 269±53 and 1727±345 ng L-1) indicate that the properties of the unsaturated zone influence the transfer and the degradation of atrazine. A counterclockwise hysteresis characterizes the relationship between the lake level and atrazine concentration. Temporal variation shows that the atrazine is transferred through the matrix and fractures with a delay caused by the sorption process that differs in atrazine and DEA. The layer of clay-with-flints is shown to favor the degradation of atrazine near the surface. Preferential pathways may be created below clay-with-flints, through which the transfer of atrazine is quicker.


Assuntos
Atrazina/análogos & derivados , Herbicidas/análise , Praguicidas/análise , Poluentes Químicos da Água/análise , Atrazina/análise , França , Água Subterrânea/química , Lagos/análise , Nitratos/análise
9.
Chemosphere ; 236: 124835, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549673

RESUMO

In this contribution, the electrocatalytic abatement of bisphenol A (BPA) with boron-doped diamond (BDD) anode had been conducted in NaNO2 electrolytes. Central composite design was used as statistical multivariate method to optimize the operating parameters adopted (applied current density, flow rate, concentration of NaNO2 and initial pH). The results from response surface analysis indicated that pH was the most influential factor for TOC decay, and a maximum TOC decay of 63.7% was achieved under the optimized operating conditions (9.04 mA cm-2 of applied current density, 400 mL min-1 of flow rate, 10 mM of NaNO2, 4.0 of initial pH and 60 min of electrolysis time). Besides, LC/MS technique was applied to identify the main reaction intermediates, and plenty of nitrated oligomers were detected at the end of the degradation. These by-products were generated via the coaction of coupling reaction of nitrated phenol and electrophilic substitution mediated by nitrogen dioxide radicals. Moreover, our results showed that the degree of nitration depended heavily on the employed initial nitrite concentration. This was one of the very few investigations dealing with nitrophenolic by-products in nitrite medium, and thus the findings exhibited important implications for electrochemical degradation of BPA and its related phenolic pollutants.


Assuntos
Compostos Benzidrílicos/química , Técnicas Eletroquímicas/métodos , Nitratos/química , Nitritos/química , Fenóis/química , Poluentes Químicos da Água/química , Boro/análise , Diamante , Eletrodos , Eletrólise , Concentração de Íons de Hidrogênio , Nitratos/análise , Nitritos/análise , Oxirredução , Fenóis/análise , Poluentes Químicos da Água/análise
10.
Environ Pollut ; 255(Pt 1): 113131, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31521992

RESUMO

Low-cost particulate matter (PM) air quality sensors are becoming widely available and are being increasingly deployed in ambient and home/workplace environments due to their low cost, compactness, and ability to provide more highly resolved spatiotemporal PM concentrations. However, the PM data from these sensors are often of questionable quality, and the sensors need to be characterized individually for the environmental conditions under which they will be making measurements. In this study, we designed and assessed a cost-effective (∼$700) calibration chamber capable of continuously providing a uniform PM concentration simultaneously to multiple low-cost PM sensors and robust calibration relationships that are independent of sensor position. The chamber was designed and evaluated with a Computational Fluid Dynamics (CFD) model and a rigorous experimental protocol. We then used this new chamber to calibrate 242 Plantower PMS 3003 sensors from two production lots (Batches I and II) with two aerosol types: ammonium nitrate (for Batches I and II) and alumina oxide (for Batch I). Our CFD models and experiments demonstrated that the chamber is capable of providing uniform PM concentration to 8 PM sensors at once within 6% error and with excellent reliability (intraclass correlation coefficient > 0.771). The study identified two malfunctioning sensors and showed that the remaining sensors had high linear correlations with a DustTrak monitor that was calibrated for each aerosol type (R2 > 0.978). Finally, the results revealed statistically significant differences between the responses of Batches I and II sensors to the same aerosol (P-value<0.001) and the Batch I sensors to the two different aerosol types (P-value<0.001). This chamber design and evaluation protocol can provide a useful tool for those interested in systematic laboratory characterization of low-cost PM sensors.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Monitoramento Ambiental/instrumentação , Monitoramento Ambiental/métodos , Material Particulado/análise , Aerossóis/análise , Óxido de Alumínio/análise , Calibragem , Hidrodinâmica , Nitratos/análise , Tamanho da Partícula , Reprodutibilidade dos Testes
11.
Environ Pollut ; 255(Pt 1): 113219, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31539849

RESUMO

The conversion of natural saltmarshes to shrimp aquaculture ponds can potentially influence the biogeochemical cycling of nutrients in coastal wetlands, but its impact on the dynamics of sediment dissimilatory nitrate (NO3-) reduction remains poorly understood. In this study, three sediment NO3- reduction processes including denitrification (DNF), anaerobic ammonium oxidation (ANAMMOX), and dissimilatory NO3- reduction to ammonium (DNRA) were examined simultaneously in a natural saltmarsh and two shrimp culture ponds (5- and 18-year-old) in July and November, using nitrogen (N) isotope-tracing experiments. Our results showed that sediment potential DNF, ANAMMOX and DNRA rates were generally higher in the shrimp culture ponds than the natural saltmarsh in the two seasons. The rates of all three processes generally increased with the age of shrimp ponds, with the magnitude of increase being less pronounced for DNF and ANAMMOX than DNRA. The contribution of DNRA to total NO3- reduction increased significantly following saltmarsh conversion to shrimp ponds, suggesting that DNRA became an increasingly important biogeochemical process under shrimp culture. DNRA competed with DNF and limited reactive N loss to some extent after natural saltmarshes converted to shrimp culture ponds. The results of redundancy analysis revealed that the availability of substrates and sulfides in sediments, rather than the bacteria gene abundance, were the most important factor influencing the NO3- reduction processes. Overall, our findings highlighted that shrimp-aquaculture reclamation may aggravate nitrogen loading in coastal wetlands by promoting the production of bioavailable ammonium.


Assuntos
Aquicultura , Nitratos/análise , Áreas Alagadas , Compostos de Amônio/análise , Animais , China , Crustáceos , Desnitrificação , Monitoramento Ambiental , Sedimentos Geológicos/microbiologia , Nitrogênio/análise , Óxidos de Nitrogênio/análise , Tanques , Eliminação de Resíduos Líquidos
12.
Science ; 365(6457): 1040-1044, 2019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31488692

RESUMO

From June to August 2018, the eruption of Kilauea volcano on the island of Hawai'i injected millions of cubic meters of molten lava into the nutrient-poor waters of the North Pacific Subtropical Gyre. The lava-impacted seawater was characterized by high concentrations of metals and nutrients that stimulated phytoplankton growth, resulting in an extensive plume of chlorophyll a that was detectable by satellite. Chemical and molecular evidence revealed that this biological response hinged on unexpectedly high concentrations of nitrate, despite the negligible quantities of nitrogen in basaltic lava. We hypothesize that the high nitrate was caused by buoyant plumes of nutrient-rich deep waters created by the substantial input of lava into the ocean. This large-scale ocean fertilization was therefore a unique perturbation event that revealed how marine ecosystems respond to exogenous inputs of nutrients.


Assuntos
Fitoplâncton/crescimento & desenvolvimento , Água do Mar/química , Erupções Vulcânicas , Clorofila A/análise , Clorofila A/metabolismo , Eutrofização , Hawaii , Metais/análise , Nitratos/análise , Nitrogênio/análise , Oceano Pacífico , Fitoplâncton/metabolismo , Água do Mar/análise
13.
Environ Pollut ; 254(Pt B): 113084, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31473385

RESUMO

Human activities lead to increasing concentration of the stable elements cesium (Cs) and strontium (Sr) and their radioactive isotopes in the food chain, where plants play an important part. Here we investigated Plantago major under the influence of long-term exposure to stable Cs and Sr. The plants were cultivated hydroponically in different concentrations of cesium sulfate (between 0.002 and 20 mM) and strontium nitrate (between 0.001 and 100 mM). Uptake of Cs and Sr into leaves was analyzed from extracts by inductively coupled plasma mass spectrometry (ICP-MS). It was increased with increasing external Cs and Sr concentrations. However, the efficiency of Cs and Sr transfer from solution to plants was higher for low external concentrations. Highest transfer factors were 6.78 for Cs and 71.13 for Sr. Accumulation of Sr was accompanied by a slight decrease of potassium (K) and calcium (Ca) in leaves, whereas the presence of Cs in the medium affected only uptake of K. The toxic effects of Cs and Sr were estimated from photosynthetic reactions and plant growth. In leaves, Cs and Sr affected the chlorophyll fluorescence even at their low concentrations. Low and high concentrations of both ions reduced dry weight and length of roots and leaves. The distribution of the elements between the different tissues of leaves and roots was investigated using Energy Dispersive X-Ray microanalysis (EDX) with scanning electron microscope (SEM). Overall, observations suggested differential patterns in accumulating Cs and Sr within the roots and leaves. When present in higher concentrations the amount of Cs and Sr transferred from environment to plants was sufficient to affect some physiological processes. The experimental model showed a potential for P. major to study the influence of radioactive contaminants and their removal from hotspots.


Assuntos
Césio/análise , Nitratos/metabolismo , Fotossíntese , Plantago/metabolismo , Estrôncio/metabolismo , Cálcio/análise , Cálcio/metabolismo , Césio/metabolismo , Hidroponia , Nitratos/análise , Folhas de Planta/química , Folhas de Planta/metabolismo , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Plantago/crescimento & desenvolvimento , Potássio/análise , Potássio/metabolismo , Poluentes Radioativos do Solo/análise , Poluentes Radioativos do Solo/metabolismo , Estrôncio/análise
14.
Plant Physiol Biochem ; 142: 363-371, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31398585

RESUMO

Nitrogen is one of the most important nutrients for plant growth and development. Nitrate nitrogen (NO3--N) is the main form of nitrogen taken up by plants. Understanding the effects of exogenous NO3--N on nitrogen metabolism at the gene expression and enzyme activity levels during nitrogen assimilation and chlorophyll synthesis is important for increasing nitrogen utilization efficiency. In this study, cell morphology, NO3--N uptake rates, the expression of key genes related to nitrogen assimilation and chlorophyll synthesis and enzyme activity in apple leaves under NO3--N deficiency were investigated. The results showed that the cell morphology of apple leaves was irreversibly deformed due to NO3--N deficiency. NO3--N was absorbed slightly one day after NO3--N deficiency treatment and effluxed after 3 days. The relative expression of genes encoding nitrogen assimilation enzymes and the activity of such enzymes decreased significantly after 1 day of NO3--N deficiency treatment. After treatment for 14 days, gene expression was upregulated, enzyme activity was increased, and NO3--N content was increased. NO3--N deficiency hindered the transformation of 5-aminobilinic acid (ALA) to porphobilinogen (PBG), suggesting a possible route by which NO3--N levels affect chlorophyll synthesis. Collectively, the results indicate that NO3--N deficiency affects enzyme activity by altering the expression of key genes in the nitrogen assimilation pathway, thereby suppressing NO3--N absorption and assimilation. NO3--N deficiency inhibits the synthesis of the chlorophyll precursor PBG, thereby hindering chlorophyll synthesis.


Assuntos
Clorofila/biossíntese , Malus/metabolismo , Nitratos/metabolismo , Folhas de Planta/metabolismo , Regulação da Expressão Gênica de Plantas , Malus/anatomia & histologia , Nitratos/análise , Nitrogênio/deficiência , Folhas de Planta/anatomia & histologia , Folhas de Planta/química , Reação em Cadeia da Polimerase em Tempo Real
15.
Environ Sci Process Impacts ; 21(9): 1570-1579, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31407763

RESUMO

The effects of antibiotics on nitrate denitrification in groundwater have acquired growing concern. Denitrification is a microbially mediated process. The effects of antibiotics on denitrification were mainly reflected in denitrifying bacteria. However, little is known about the relationship between antibiotics and denitrifying bacteria. Based on this, both direct antimicrobial susceptibility testing and microbial batch-culture experiments were conducted to assess the influences of typical antibiotics on denitrifying groundwater bacteria, mainly Pseudomonas (46.17%). Denitrifying bacteria, screened from a long-term groundwater denitrification environment, were tested for sensitivity to five typical antibiotics in groundwater: sulfamethoxazole (SMX), erythromycin (ERY), enrofloxacin (ENR), clindamycin (CLI), and tetracycline (TCY). The results showed that the sensitivity of denitrifying bacteria to antibiotics is mainly related to the type and concentration of antibiotics. For antibiotic types, the order of sensitivity by quantitative assessment is ENR > TCY > SMX > ERY > CLI. Fluoroquinolones (FQs) represented by ENR were selected to explore their concentration effects. The influences on denitrifying bacteria were divided into the high concentration effect (500 µg L-1 to 100 mg L-1) and the low concentration effect (100 ng L-1 to 10 µg L-1) with about 100 µg L-1 as a boundary. Exposure to high concentrations had significant inhibitory effects on bacterial growth and exhibited dose dependency, especially for ciprofloxacin (CIP). The low concentration effect was independent of concentration, which may be stimulation or inhibition. The stimulation mainly occurred due to ENR-exposure. For inhibitory effects, Lomefloxacin (LOM) was more effective than other FQs. Especially for inhibition at ng-level exposure, LOM and norfloxacin (NOR) exposures led to the highest and lowest inhibition rates, respectively.


Assuntos
Antibacterianos/análise , Água Subterrânea/química , Nitratos/análise , Pseudomonas/efeitos dos fármacos , Poluentes Químicos da Água/análise , Desnitrificação , Relação Dose-Resposta a Droga , Água Subterrânea/microbiologia , Testes de Sensibilidade Microbiana , Pseudomonas/crescimento & desenvolvimento
16.
Environ Pollut ; 254(Pt A): 112864, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31369912

RESUMO

To better understand the mechanism of PM2.5 explosive growth (EG), we conducted concurrent measurements of gaseous pollutants, PM2.5 and its chemical composition (inorganic ions, organic carbon, and element carbon) with a time resolution of 1 h in Shanghai in late autumn and winter from 2014 to 2017. In this study, the EG events, which are defined as the net increase in the mass concentration of PM2.5 by more than 100 µg m-3 within hours, are separately discussed for 3, 6, or 9 h. The number of EG events decreased from 19 cases in 2014 to 6 cases in 2017 and the corresponding PM2.5 concentration on average decreased from 183.6 µg m-3 to 128.8 µg m-3. Both regional transport and stagnant weather (windspeed < 2.0 m s-1) could lead to EG events. The potential source contribution function (PSCF) shows that the major high-pollution region is in East China (including Zhejiang, Jiangsu, Shandong, and Anhui Province) and the North China Plain. The contribution of stagnant conditions to EG episode hours of 55% (198 h, 156.9 µg m-3) is higher than that of regional transport (45%, 230 h, 163.0 µg m-3). To study the impact of local emission, chemical characteristics and driving factors of EG were discussed under stagnant conditions. The major components contributing to PM2.5 are NO3- (17.9%), organics (14.1%), SO42- (13.1%), and NH4+ (13.1%). The driving factors of EG events are the secondary aerosol formation of sulfate and nitrate and primary emissions (vehicle emissions, fireworks, and biomass burning), but the secondary transformation contributes more to EG events. The formation of sulfate and nitrate is dominated by gas-phase oxidation and heterogeneous reactions, which are enhanced by a high relative humidity. The current study helps to understand the chemical mechanism of haze and provides a scientific basis for air pollution control in Shanghai.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Aerossóis/análise , Carbono/análise , China , Poluentes Ambientais , Poluição Ambiental , Gases , Nitratos/análise , Óxidos de Nitrogênio , Estações do Ano , Sulfatos/análise , Emissões de Veículos/análise , Tempo (Meteorologia)
17.
Mar Pollut Bull ; 146: 377-386, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426170

RESUMO

The effects of nutrient distribution and structure on the behavior and speciation of dissolved inorganic arsenic (DIAs) in coastal waters were analyzed based on the data of 48 surface water samples collected in the southwestern coast of Laizhou Bay and its adjacent rivers (SWLZB). The concentration of DIAs in the SWLZB ranged from 0.016 to 0.099 µmol l-1 and generally decreased from west to south. The inshore waters exhibited higher DIAs level than the open ocean. The As5+/As3+ ratio was significantly positively correlated with the concentration of TDN, NO3-N, PO4-P, DSi, Chl-a and DO. The concentration of DIAs was strongly correlated with the concentration of PO4-P and DSi, suggesting that adsorption/desorption was an important process for regulating the total DIAs concentration. The results indicated that the distribution of nutrients might well be an important environmental factor affecting the speciation and behavior of DIAs in surface water of the SWLZB.


Assuntos
Arsênico/análise , Água do Mar/química , Poluentes Químicos da Água/análise , Arsênico/química , Baías , China , Clorofila A/análise , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Nitratos/análise , Nitrogênio/análise , Nutrientes/análise , Fosfatos/análise , Fósforo/análise , Rios/química , Água do Mar/análise , Poluentes Químicos da Água/química
18.
Mar Pollut Bull ; 146: 417-426, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426176

RESUMO

The Arabian Gulf is a warm (summer SST > 30 °C) and hypersaline (salinity > 40 psu at any time) marginal sea of the Indian Ocean. This paper reports on a 3-year study of seasonal and spatial changes of primary production and associated physico-chemical and biological parameters in the coastal waters of Saudi Arabia in the western Arabian Gulf. The primary production rates were low and yet showed a seasonality, with a major spring peak and a minor autumn peak, and a possible significant role for heterotrophs. While the strong relationships between the net changes of carbon uptake and nutrients between seasons showed a control of primary production by the availability of nutrients, the decrease in primary production between spring and summer when nutrients continued to increase suggests that the primary production at this time could have been controlled by higher ambient temperatures and intensities of incident light.


Assuntos
Nitratos/análise , Fosfatos/análise , Água do Mar/química , Radioisótopos de Carbono/análise , Clorofila A/análise , Clorofila A/metabolismo , Monitoramento Ambiental , Oceano Índico , Salinidade , Arábia Saudita , Estações do Ano , Análise Espaço-Temporal , Temperatura Ambiente
19.
Environ Pollut ; 253: 1000-1008, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31434177

RESUMO

Intertidal wetlands can sequester pollutants along estuarine conduits. Here we test the effectiveness of a mangrove-dominated estuary in removing dissolved nitrogen during a rain event. We intensively and simultaneously sampled surface water nutrients upstream and downstream of an estuary before, during and after a 63 mm rain event in Coffs Creek (Australia). NOx was the main form of dissolved nitrogen upstream of the estuary (∼60%), while dissolved organic nitrogen (DON) was an important form at the downstream station (∼46%) during observations. High NOx attenuation (71%) occurred during the rain event when the loads reached 31 µmol m-2 catchment area day-1. In contrast, the estuary was found to be a source of NH4+ (∼5 µmol m-2 catchment area day-1). This implies a moderate conversion of upstream NOx into NH4+ and DON along the transport pathway, likely due to tidally-driven pore water exchange within the anoxic estuarine mangrove sediments. Overall, the mangrove-lined estuary attenuated upstream total dissolved nitrogen loads, maintaining water quality and minimizing exports to the coastal ocean even during high flow conditions.


Assuntos
Monitoramento Ambiental , Inundações , Nitratos/análise , Áreas Alagadas , Austrália , Estuários , Nitrogênio/análise , Óxidos de Nitrogênio , Chuva , Qualidade da Água
20.
Environ Sci Pollut Res Int ; 26(30): 31026-31037, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31452118

RESUMO

An in situ soil experimental system was designed to determine how urbanization impacts soil nitrogen and phosphorus dynamics. Variables including the road density, normalized difference vegetation index, distance to the nearest highway and industrial area from the soil experimental site, land use impact index, population density, population change index, total population, and percentage of water area were used to quantitatively explain the soil nitrogen and phosphorous contents. The results showed that the total phosphorous in the soil increased slowly after September 2013, indicating a phosphorous accumulation phenomenon in the soil in urban areas. The nitrate nitrogen in the soil had a higher value in September 2013, while the soil ammonium nitrogen content was higher during the winter. Moreover, the soil ammonium nitrogen content was higher than the nitrate nitrogen content during most of the experimental period. The distance from the urban centre, road density, proportion of built-up land, and population density can explain the soil nutrient dynamics quantitatively, showing that 45.4% of the soil nitrate nitrogen content, 84.1% of the soil ammonium nitrogen content, 44.6% of the ratio of NO3/NH4, 58.1% of the ratio of total inorganic nitrogen (TIN)/total phosphorous (TP), and 81.6% of the TIN could be explained by one of these variables at most. The potential factors affecting the changes in soil N contents include changes in human dietary habits as more people migrate to cities and industrial wastewater discharge. This study is helpful in quantitatively understanding the urbanization process and associated environmental impacts.


Assuntos
Nitrogênio/análise , Fósforo/análise , Solo/química , China , Cidades , Meio Ambiente , Nitratos/análise , Urbanização , Água
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