Low Nitrate Concentrations Research Articles

Water Quality of the Odra (Oder) River before and during the Ecological Disaster in 2022: A Warning to Water Management

Aquatic ecosystems are under pressure due to human activity. In the summer of 2022, the Odra River (Central Europe) suffered a massive death of fish and mollusks. This paper aims to show selected water quality parameters before and during the ecological disaster and find which parameters may have been crucial to the development of this disaster. We used the Kruskal–Wallis test and Spearman’s correlation to check the water parameters’ spatial and temporal diversification. In addition, non-metric multidimensional scaling was performed. The water quality parameters of the Odra system were analyzed in sections: middle Odra, lower Odra, transitional waters, and Szczecin Lagoon. Human activity has led to the formation of a system with unusual characteristics, disturbing the river’s natural continuum and related processes. The year 2022 in the middle Odra differed from the previous years in having a high water temperature (>24 °C), high ammonium concentrations (>4 mg/L), and relatively low nitrate concentrations (<6.5 mg/L). At the same time, salt pollution in the river was very high (maximum 1.4 g/L). In June and July 2022, we observed low chlorophyll a concentrations in the middle Odra (on average 2.3 µg/L and 4.4 µg/L, respectively), presumably due to salinity stress and high temperatures, suppressing freshwater phytoplankton taxa. This circumstance has created the appropriate conditions for developing euryhaline and thermophilic Prymnesium parvum. Because of decaying organisms, hypoxia occurred in the lower Odra (0.26 mg/L of dissolved oxygen in surface waters), and oxygen conditions worsened in the transitional waters (<4 mg/L). The zonal deaths of fish and mollusks result from multiple stressors induced by human activity. This disaster has proven that it is necessary to improve selected water quality parameters to reduce the risk of such disasters. The most urgent recommendations are to reduce the salt pollution of the upper section of the Odra, reduce nutrient inputs, and improve the condition of smaller rivers feeding the main course of the Odra.

Short-Term Toxicity of ZnO Nanoparticles on Microalgae at Different Initial Nutrient Concentrations

The aim of this work was to investigate the combined short-term toxic effect of zinc oxide (ZnO) nanoparticles (NPs) and nitrate concentration of the medium on freshwater microalgae. For this purpose, freshwater microalgae Chlorococcum sp. was cultivated in modified Blue-Green medium (BG-11) containing nitrate concentrations ranging from 0 to 300 mg/L, and exposed to ZnO NPs in different concentrations (0.081 to 810 mg/L) for a period up to 96 h. The experimental results revealed that algal growth was affected by the exposure time, NPs concentrations, and mainly the initial nitrate concentration. Differences in microalgae growth rates were observed. The toxic effect of ZnO NPs was higher on microalgae cultured in modified BG-11 with low and high nitrate concentrations. During the 4-day exposure, the highest growth rates were observed at 24 h at an initial nitrate concentration of 50 mg/L; 1.94 d−1 and 0.22 d−1 for 0 and 810 mg/L ZnO NPs, respectively. Nitrate uptake by algal biomass reached up to 40.1% after 96 h of operation in the control culture with an initial nitrate concentration of 50 mg/L. Finally, the results of this study showed the need for the investigation of ZnO NPs toxicity on microalgae under optimum and stressful nutrient conditions for microalgae growth.

KANDUNGAN NITRIT, NITRAT, DAN FOSFAT AIR SUNGAI KARANG MUMUS DARI HULU SAMPAI HILIR

The river found in Samarinda City is the Karang Mumus River. This river is a tributary of the Mahakam River which divides Samarinda City in East Kalimantan. The polluting source of the Karang Mumus River comes from domestic activities such as settlements, markets, shopping centers, and hotels. The purpose of this study is to determine the water quality of the Karang Mumus river in terms of predetermined parameters, namely nitrites, nitrates and phosphates in waters. This type of research is a descriptive study with a qualitative approach to see the concentration of nitrite, nitrate, and phosphate parameters in the water of the Karang Mumus River from Upstream to Downstream. The results showed that the highest nitrite value based on eight segments was in segment 3 is 0.026 mg/L. The lowest value of nitrite was in segment 8 with a concentration of 0.0095 mg/L. Based on PerDa KalTim No. 02 of 2011 class II nitrite value in all segments is still meet the quality standard of 0.06 mg/L. The highest concentration of nitrate is upstream, in segment 2 with a concentration of 0.155 mg/L. Lowest nitrate concentration is in the middle of segment 5, which is 0.069 mg/L. Based on PerDa KalTim No. 02 of 2011 class II nitrate value in all segments is still meet the quality standard of 10 mg/L. The lowest phosphate concentration in the middle of segment 5, is 0.031 mg/L. The highest phosphate concentration is upstream of segment 1, which is 0.098 mg/L. Based on PerDa KalTim No. 02 of 2011 class II, the phosphate value in all segments is still meet the quality standard of 0.2 mg/L.

Gas Flow-Dependent Modification of Plasma Chemistry in μAPP Jet-Generated Cold Atmospheric Plasma and Its Impact on Human Skin Fibroblasts.

The micro-scaled Atmospheric Pressure Plasma Jet (µAPPJ) is operated with low carrier gas flows (0.25-1.4 slm), preventing excessive dehydration and osmotic effects in the exposed area. A higher yield of reactive oxygen or nitrogen species (ROS or RNS) in the µAAPJ-generated plasmas (CAP) was achieved, due to atmospheric impurities in the working gas. With CAPs generated at different gas flows, we characterized their impact on physical/chemical changes of buffers and on biological parameters of human skin fibroblasts (hsFB). CAP treatments of buffer at 0.25 slm led to increased concentrations of nitrate (~352 µM), hydrogen peroxide (H2O2; ~124 µM) and nitrite (~161 µM). With 1.40 slm, significantly lower concentrations of nitrate (~10 µM) and nitrite (~44 µM) but a strongly increased H2O2 concentration (~1265 µM) was achieved. CAP-induced toxicity of hsFB cultures correlated with the accumulated H2O2 concentrations (20% at 0.25 slm vs. ~49% at 1.40 slm). Adverse biological consequences of CAP exposure could be reversed by exogenously applied catalase. Due to the possibility of being able to influence the plasma chemistry solely by modulating the gas flow, the therapeutic use of the µAPPJ represents an interesting option for clinical use.

OsNPF3.1, a nitrate, abscisic acid and gibberellin transporter gene, is essential for rice tillering and nitrogen utilization efficiency

Low-affinity nitrate transporter genes have been identified in subfamilies 4–8 of the rice nitrate transporter 1 (NRT1)/peptide transporter family (NPF), but the OsNPF3 subfamily responsible for nitrate and phytohormone transport and rice growth and development remains unknown. In this study, we described OsNPF3.1 as an essential nitrate and phytohormone transporter gene for rice tillering and nitrogen utilization efficiency (NUtE). OsNPF3.1 possesses four major haplotypes of its promoter sequence in 517 cultivars, and its expression is positively associated with tiller number. Its expression was higher in the basal part, culm, and leaf blade than in other parts of the plant, and was strongly induced by nitrate, abscisic acid (ABA) and gibberellin 3 (GA3) in the root and shoot of rice. Electrophysiological experiments demonstrated that OsNPF3.1 is a pH-dependent low-affinity nitrate transporter, with rice protoplast uptake assays showing it to be an ABA and GA3 transporter. OsNPF3.1 overexpression significantly promoted ABA accumulation in the roots and GA accumulation in the basal part of the plant which inhibited axillary bud outgrowth and rice tillering, especially at high nitrate concentrations. The NUtE of OsNPF3.1-overexpressing plants was enhanced under low and medium nitrate concentrations, whereas the NUtE of OsNPF3.1 clustered regularly interspaced short palindromic repeats (CRISPR) plants was increased under high nitrate concentrations. The results indicate that OsNPF3.1 transports nitrate and phytohormones in different rice tissues under different nitrate concentrations. The altered OsNPF3.1 expression improves NUtE in the OsNPF3.1-overexpressing and CRISPR lines at low and high nitrate concentrations, respectively.

Nitrogen forms and concentration influence the impact of titanium dioxide nanoparticles on the biomass and antioxidant enzyme activities of Microcystis aeruginosa

Nanoparticles (NPs) are becoming more widely produced, used, and released into the aquatic environment. In aquatic ecosystems, these NPs affect different populations of photosynthesizing organisms, such as cyanobacteria. This study aimed to evaluate the effects of titanium dioxide (TiO2) NPs (48mgl-1) combined with low (0.04mM) and high (9mM) concentrations of urea and nitrate on Microcystis aeruginosa. Microcystins (MCs) production and release were monitored in the cyanobacterium. The results showed that high urea concentration (9mM) combined with TiO2 NPs inhibited growth, pigment, and malondialdehyde (MDA) content by 82%, 63%, and 47%, respectively. The treatment also increased the reactive oxygen species (ROS) and glutathione S-transferase (GST) activity by 40.7% and 67.7%, respectively. Similarly, low nitrate (0.04mM) combined with TiO2 NPs inhibited growth by 40.3% and GST activity by 36.3% but stimulated pigment production and ROS concentration in M. aeruginosa. These responses suggest that high urea combined with TiO2.NPs and high nitrate combined with TiO2 NPs induced oxidative stress in cyanobacteria. The peroxidase (POD) activity of M. aeruginosa decreased by 17.7% with increasing urea concentrations. Our findings suggest that TiO2 NPs combined with changing nutrient (urea and nitrate) concentrations may adversely affect cyanobacterial development and antioxidant defense enzymes.

Influence of concentration of different chemical precursors on the physical properties of Cr2O3 thin films elaborated via pneumatic spray

In this paper, Cr2O3 thin films were synthesized successfully on glass substrates at 450 °C using a simple and low-cost homemade pneumatic spray system (SP) using two different precursors: chromium chloride and chromium nitrate. A systematic study of the influence of concentration of each precursor used for deposition on the structural, morphological, optical and electrical properties has investigated. The XRD results show that the Cr2O3 films prepared with chromium chloride are polycrystalline with rhombohedral structure and those prepared with low concentration of chromium nitrate have a poor crystallinity. Peaks associated with Cr and O elements are present in EDS analysis that confirm the composition of the films and SEM images revealed a uniform, homogeneous and well covered surface. The measured electrical conductivity was found in the order of 5(Ω.cm)–1. The average transmittance of the films deposited from chromium nitrate is in the range of 60 % and for the films deposited from chromium chloride, it reaches75 % in the visible region. These electrical and optical properties of Cr2O3 thin film ascribed to its wide band gap, are indeed required for optoelectronic devices especially for solar cell window.

Modification and validation of an analytical method for the simple determination of nitrate in seawater by reduction to nitrite with zinc powder

As copper-coated cadmium granules, which are recommended for use in the standard method for analyzing nitrate, are environmentally unfriendly and forbidden in some countries, an alternative method is required. To enhance the method for determining low nitrate concentration in seawater, the optimal conditions for reducing nitrate to nitrite using zinc powder were assessed in this study. The modified zinc method was optimal at an 0.8:1 (v/v) ratio of buffer solution (pH 8.5) (4 ml) to water sample (5 ml) with 50 mg of zinc powder and a standing time of 30 min. The nitrite was reacted with sulfanilamide and N-(1-Naphthyl)-ethylenediamine dihydrochloride after nitrate reduction, and spectrophotometrically quantified at 543 nm. This modified method was found to have a linear dynamic range of 0.1–7.0 μM, a low detection limit (0.1 μM), good intra-day and inter-day reproducibility (<5% relative standard deviation), high-efficiency reduction (>95%), and excellent accuracy in analysis of certified reference material (95% relative accuracy). The results obtained using the modified method agreed well with those obtained using the conventional cadmium column method. Overall, this alternative green chemistry method is a simplified procedure for determining nitrate in seawater with a high efficiency.

Convergently selected NPF2.12 coordinates root growth and nitrogen use efficiency in wheat and barley.

Understanding the genetic and molecular function of nitrate sensing and acquisition across crop species will accelerate breeding of cultivars with improved nitrogen use efficiency (NUE). Here, we performed a genome-wide scan using wheat and barley accessions characterized under low and high N inputs that uncovered the NPF2.12 gene, encoding a homolog of the Arabidopsis nitrate transceptor NRT1.6 and other low-affinity nitrate transporters that belong to the MAJOR FACILITATOR SUPERFAMILY. Next, it is shown that variations in the NPF2.12 promoter correlated with altered NPF2.12 transcript levels where decreased gene expression was measured under low nitrate availability. Multiple field trials revealed a significantly enhanced N content in leaves and grains and NUE in the presence of the elite allele TaNPF2.12TT grown under low N conditions. Furthermore, the nitrate reductase encoding gene NIA1 was up-regulated in npf2.12 mutant upon low nitrate concentrations, thereby resulting in elevated levels of nitric oxide (NO) production. This increase in NO correlated with the higher root growth, nitrate uptake, and N translocation observed in the mutant when compared to wild-type. The presented data indicate that the elite haplotype alleles of NPF2.12 are convergently selected in wheat and barley that by inactivation indirectly contribute to root growth and NUE by activating NO signaling under low nitrate conditions.

Proteomic and toxicological analysis of the response of dinoflagellate Alexandrium catenella to changes in NaNO3 concentration

Dinoflagellates of the genus Alexandrium cause Harmful Algal Blooms (HABs) in coastal waters worldwide, damaging marine environments, aquaculture, and human health. They synthesize potent neurotoxic alkaloids known as PSTs (i.e., Paralytic Shellfish Toxins), the etiological agents of PSP (i.e., Paralytic Shellfish Poisoning). In recent decades, the eutrophication of coastal waters with inorganic nitrogen (e.g., nitrate, nitrite, and ammonia) has increased the frequency and scale of HABs. PSTs concentrations within Alexandrium cells can increase by up to 76% after a nitrogen enrichment event; however, the mechanisms that underlie their biosynthesis in dinoflagellates remains unclear. This study combines mass spectrometry, bioinformatics, and toxicology and investigates the expression profiles of PSTs in Alexandrium catenella grown in 0.4, 0.9 and 1.3 mM NaNO3. Pathway analysis of protein expression revealed that tRNA amino acylation, glycolysis, TCA cycle and pigment biosynthesis were upregulated in 0.4 mM and downregulated in 1.3 mM NaNO3 compared to those grown in 0.9 mM NaNO3. Conversely, ATP synthesis, photosynthesis and arginine biosynthesis were downregulated in 0.4 mM and upregulated in 1.3 mM NaNO3. Additionally, the expression of proteins involved in PST biosynthesis (sxtA, sxtG, sxtV, sxtW and sxtZ) and overall PST production like STX, NEO, C1, C2, GTX1-6 and dcGTX2 was higher at lower nitrate concentrations. Therefore, increased nitrogen concentrations increase protein synthesis, photosynthesis, and energy metabolism and decrease enzyme expression in PST biosynthesis and production. This research provides new clues about how the changes in the nitrate concentration can modulate different metabolic pathways and the expression of PST biosynthesis in toxigenic dinoflagellates.

Hormesis effects of phenol on growth and cellular metabolites of Chlorella sp. under different nutritional conditions using response surface methodology

The present study investigated the effects of different phenol concentrations (200 – 1000 mg L−1) towards Chlorella sp. under different culture conditions (light vs. dark) and NaNO3 concentrations (0 – 0.1 g L−1) using central composite design. Phenol induced hormesis effects on the algal growth and cellular metabolites. Nitrate was identified as a crucial factor for promoting the uptake of phenol by Chlorella cells, while light was a limiting factor for growth, but the phyco-toxicity of phenol was decreased in the dark. The pigment contents were generally increased in the treated cells to protect against the oxidative phenol stress. The incorporation of 200 mg L−1 phenol and 0.05 g L−1 NaNO3 to the illuminated cells markedly promoted biomass and lipid contents to 0.22 g L−1 and 26.26% w/w, which was 44 and 112% higher than the phenol-less control, respectively. Under the same conditions, the increase of phenol concentration to 600 mg L−1, the protein contents were increased to 18.59% w/w. Conversely, the algal cells were able to accumulate more than 60% w/w of soluble carbohydrates under dark conditions at 600 mg L−1 of phenol. Nitrate replete conditions stimulated lipid accumulation at the expense of protein biosynthesis. Furthermore, most of the treatments showed an increase of H2O2 and malonaldehyde contents, especially for the illuminated cells. However, catalase activity tended to increase under dark conditions, especially at low phenol and nitrate concentrations. This study is valuable in indicating the effects of phenol on microalgae by exploiting response surface methodology, which can be applied as a powerful tool in growth monitoring and toxicity assessment.

Groundwater characterization of the eastern Minesing Wetlands in support of the endangered Hine’s emerald dragonfly (Somatochlora hineana)

The Minesing Wetlands contain Canada’s only known population of Hine’s emerald dragonfly (HED), a species listed as endangered since 2011. The HED relies on groundwater discharge areas to complete its life cycle and therefore the population is potentially sensitive to changes in groundwater. The goals of this study were to, (1) characterize groundwater discharge to the eastern portion of the Minesing Wetlands, which corresponds to the HED habitat, (2) document any significant changes in groundwater chemistry since a 1998 study, and (3) establish a comprehensive baseline water quality data set to facilitate future comparisons. Consistent with HED habitats in the USA, the chemistry of Minesing Wetlands groundwater was dominated by calcium and bicarbonate. Low groundwater chloride and nitrate concentrations indicated minimal impact from activities such as road salt application and fertilizer use. Nitrate was generally only found at the wetland margin where groundwater springs emerged from the base of the uplands. The dominant form of inorganic nitrogen in wetland groundwater was ammonium (max = 1.5 mg N/L), and soluble reactive phosphorus concentrations were also relatively high (8 to 122 µg/L). The most consistent change in wetland groundwater chemistry between the 1998 study and samples collected in 2015–2017 was that chloride concentrations in 10 of 23 wells increased over time, however the maximum mean well chloride (11.6 mg/L) remained well below the guideline for the protection of aquatic life (120 mg/L). To preserve HED habitat, potential impacts to groundwater need to be considered during land use planning for the recharge area.

Physicochemical characteristics and heavy metals of groundwater during the wet and dry seasons at the Lafarge cement factory environment, Sagamu, Ogun State, Nigeria

AbstractThis study examined the physical, chemical, and heavy metals in groundwater from boreholes and hand‐dug wells at the Lafarge cement factory environment at Sagamu, Ogun State, Nigeria. Water samples were obtained from 20 sampling locations during the wet and dry seasons of 2019. The 17 parameters determined include the pH, temperature, electrical conductivity, total dissolved solids (TDS), total hardness, alkalinity, salinity, chloride, sulfate, phosphate, nitrate, calcium, magnesium, copper, lead, iron, and cadmium. The samples were analyzed using titrimetric and spectrophotometric methods. Correlation analysis was applied as part of the analytical tool in this study. The result indicated low physiochemical concentration of pH, total hardness, sulfate, nitrate, chloride, magnesium, calcium (&gt;1% to 15%), and electrical conductivity (&gt;1000 μS/cm) and fell within the Standard Organization of Nigeria (SON) and World Health Organization (WHO) desirable and maximum permissible limits for potable water during the wet and dry seasons. However, phosphate was above the standard limit for portable water of 6.5 mg/L in all sampling locations, whereas the total alkalinity was above the WHO standard limit (200 mg/L) in 12 locations in the wet seasons and a location in the dry season. Salinity was also above standards in one and four locations in the wet and dry seasons, respectively. Lead and cadmium were not detected in most locations, whereas iron, lead, cadmium, and copper were above standard limits in some locations. A significant relationship exists between the heavy metals and some of the physiochemical parameters at p ≥ .05 and p ≥ .01. The polluted water in most locations is capable of resulting in an adverse health hazard. Thus, this study explains the effect of physicochemical and heavy metals on water management at Sagamu and is important for water resource planning.

Water and Nutrient Recovery for Cucumber Hydroponic Cultivation in Simultaneous Biological Treatment of Urine and Grey Water

Water and nutrient deficiencies in soil are becoming a serious threat to crop production. Therefore, usable water and nutrient recovery from wastewater, such as urine and grey water, should be considered. In this work, we showed the possibility of using grey water and urine after processing in an aerobic reactor with activated sludge in which the nitrification process takes place. The resulting liquid (nitrified urine and grey water, NUG) contains three potential factors that can adversely affect plant growth in a hydroponic system: anionic surfactants, nutrient deficits, and salinity. After dilution and supplementation with small amounts of macro- and micro-elements, NUG was suitable for cucumber cultivation. Plant growth on this modified medium (enriched nitrified urine and grey water, NUGE) was similar to that of plants cultivated on Hoagland solution (HS) and reference commercial fertilizer (RCF). The modified medium (NUGE) contained a significant amount of sodium (Na) ions. Therefore, typical effects of salt stress were observed in cucumber plants, including reduced chlorophyll levels, slightly weaker photosynthesis parameters, increased H2O2 levels, lipid peroxidation, ascorbate peroxidase (APX) activity, and proline content in the leaves. In addition, reduced protein levels were observed in plants treated with recycled medium. At the same time, lower nitrate content in tissues was found, which may have resulted from their intensive use by nitrate reductase (NR), the activity of which significantly increased. Although cucumber is a glycophyte, it grew very well in this recycled medium. Interestingly, salt stress and possibly anionic surfactants promoted flower formation, which in turn could positively affect plant yield.

The impact of livestock activities and geochemical processes on groundwater quality of fractured volcanic rock aquifer: Lake Çıldır watershed (NE Turkey)

This paper presents the impact of livestock activities and geochemical processes on the water quality of a fractured volcanic rock aquifer in the Lake Çıldır watershed, located at the northeastern part of Turkey. The existence of a high livestock population and animal grazing activities in meadow and pasturelands of the watershed during the short summer period poses serious stress on both surface and groundwater resources being the only drinking water supply for the local communities. Therefore, understanding the effect of grazing and livestock breeding activities occurring in the recharge areas of the fractured volcanic rock aquifer is vital to take precautions in order to protect limited water supplies at the watershed and vulnerable lake ecosystem as well. The mean nitrate content of the groundwater was measured at 6.4 ± 6.6 (std. dev) mg/L in the wet (before grazing) period and 7.1 ± 5.9mg/L in the dry (after grazing) period. Despite low nitrate concentration levels of groundwater, microbial contamination was observed in the spring waters at alarming levels especially after the animal grazing activities. 56%, 26%, and 11% of the groundwater samples showed bacterial contamination in terms of total coliform, fecal coliform, and fecal streptococci contents, respectively, prior to grazing activity, while in pursuit of intense livestock grazing at highland, these microbial indicators have been increased to 92%, 85%, and 77% in the dry period. A significant increase observed in fecal contamination indicates the negative impact of livestock activities on groundwater quality. Al (200-638µg/L) and Fe (66-218µg/L) enrichments locally observed in groundwater were related to advanced argillic alteration (kaolinization) and hematization zones in pyroclastic rocks.

ВМІСТ БІЛКА ТА НІТРАТІВ У ЗЕРНІ КУКУРУДЗИ І НАСІННІ СОНЯШНИКУ ПРИ ЇХ ВИРОЩУВАННІ НА СХИЛОВИХ ЗЕМЛЯХ

В Україні приблизно третина всіх орних земель зазнає прояву водної ерозії. Причинами розвитку ерозійних процесів є розорювання схилових земель крутизною понад 3 °, вирощування на них просапних культур, переважно кукурудзи та соняшнику, інтенсивний обробіток ґрунту з перевертанням скиби. За вирощування на таких землях сільськогосподарських культур їхня продуктивність істотно зменшується, проте питання зміни показників поживності й екологічної безпечності одержаної продукції на силових землях не досліджене. Дослідження проводилися закладанням польових дослідів на схилових землях з поширеням слабо- і середньозмитих ерозійних процесів і вирощуванням на них кукурудзи та соняшнику. Лабораторні дослідження проводили в сертифікованій Науково-вимірювальній агрохімічній лабораторії Вінницького національного аграрного університету. Визначали зміну вмісту білка та нітратів у рослинницькій продукції залежно від схилу. У разі вирощування кукурудзи та соняшнику на схилових землях найвищий вміст білка та нітратів спостерігається в їхній продукції з нижньої частини схилу. Найнижчий вміст білка в насінні соняшнику встановлений у середній частині схилу, який був на 4,0% менший, ніж у нижній частині схилу. Найнижчий вміст білка в зерні кукурудзи спостерігався у верхній частині схилу, що був на 0,3% менший, ніж у нижній частині схилу. Найнижчий вміст нітратів у зерні кукурудзи встановлений у верхній частині схилу, що був на 21,0% менший, ніж у низу схилу. Найменший вміст нітратів у насінні соняшнику встановлений у середній частині схилу і був на 20,0% нижчий, ніж у низу схилу.

In situ investigation of N deposit effects on polycyclic aromatic hydrocarbons (PAHs) photolysis in snow

As snow is an ideal scavenger of polycyclic aromatic hydrocarbons (PAHs) for both particulate- and gas-phase PAHs, a large amount of PAHs are accumulated in snowpacks. These PAHs could be released from seasonal snowpacks into environment over a short time during the snow melting period, causing a flush of contaminants. Understanding the fate of PAHs in snow therefore is important to evaluate the contaminant flush during snow melting. However, as an important natural process, PAH photolysis in snow is still unclear, especially in the context of global climate change. Therefore, photolysis of the 16 PAHs, which are listed as priority controlled pollutants by United States Environmental Protection Agency (US EPA), was investigated with N deposit in field in snow in this study. A mixture of the 16 US EPA priority PAHs and nitrate/ammonia were spiked into sealed quartzose bottles containing snow samples in field. The bottles were then exposed to solar radiation in field for 6 h. Experimental results showed that >50% of PAHs were lost during 6 h photolysis, mostly occurred in the first hour. Generally, HMW PAHs were photolyzed faster than LMW PAHs, though the photolysis rate did not strictly increase with molecular weight. Low concentrations of nitrate can enhance photolysis of Ant and Pyr, while photolysis of investigated PAHs was inhibited with nitrate concentration increasing. In contrast, both low and high concentration of ammonium can inhibit PAH photolysis. The inhibiting effect of both nitrate and ammonia on photolysis of HMW PAH is stronger than that of LMW PAHs, indicating direct photolysis of PAHs is the main pathway of PAH degradation in snow in situ. This study firstly showed the effect of N deposition on PAH photolysis in snow. Under current increasing N deposition in northeast China, this study implied that more PAHs in snow could be preserved during winter and released shortly during snowmelt, resulting in high ecological risk in spring.

Diversity, distribution and organic substrates preferences of microbial communities of a low anthropic activity cave in North-Western Romania.

Karst caves are characterized by relatively constant temperature, lack of light, high humidity, and low nutrients availability. The diversity and functionality of the microorganisms dwelling in caves micro-habitats are yet underexplored. Therefore, in-depth investigations of these ecosystems aid in enlarging our understanding of the microbial interactions and microbially driven biogeochemical cycles. Here, we aimed at evaluating the diversity, abundance, distribution, and organic substrate preferences of microbial communities from Peștera cu Apă din Valea Leșului (Leșu Cave) located in the Apuseni Mountains (North-Western Romania). To achieve this goal, we employed 16S rRNA gene amplicon sequencing and community-level physiological profiling (CLPP) paralleled by the assessment of environmental parameters of cave sediments and water. Pseudomonadota (synonym Proteobacteria) was the most prevalent phylum detected across all samples whereas the abundance detected at order level varied among sites and between water and sediment samples. Despite the general similarity at the phylum-level in Leșu Cave across the sampled area, the results obtained in this study suggest that specific sites drive bacterial community at the order-level, perhaps sustaining the enrichment of unique bacterial populations due to microenvironmental conditions. For most of the dominant orders the distribution pattern showed a positive correlation with C-sources such as putrescine, γ-amino butyric acid, and D-malic acid, while particular cases were positively correlated with polymers (Tween 40, Tween 80 and α-cyclodextrin), carbohydrates (α-D-lactose, i-erythritol, D-mannitol) and most of the carboxylic and ketonic acids. Physicochemical analysis reveals that sediments are geochemically distinct, with increased concentration of Ca, Fe, Al, Mg, Na and K, whereas water showed low nitrate concentration. Our PCA indicated the clustering of different dominant orders with Mg, As, P, Fe, and Cr. This information serves as a starting point for further studies in elucidating the links between the taxonomic and functional diversity of subterranean microbial communities.

Study on removing marine multiple pollutants in raw exhaust gas with a novel composited method combined with pre-agglomeration and wet scrubbing technology.

Most of the existing oxidation denitrification methods need longer residence time to obtain higher NOx removal efficiency. In this study, urea peroxide (CO(NH2)2·H2O2) was first used for removing SO2 and NOx on diesel engine bench. The addition of ferrous sulfate can enhance the oxidant capacity of the solution. The better removal efficiency and lower nitrate content in liquid can be achieved in short exhaust gas residence time. The raw gas flow and residence time contained the actual application situation in ships and have high reference value. The removal efficiency decreased with the increase of gas flow, and the reaction temperature, urea peroxide concentration, liquid-gas ratio were the main factors. The optimal Fe2+ concentration of 50mmol/L and pH value of 4 were determined. The urea peroxide concentration, reaction temperature, and liquid-gas ratio were 9%, 70℃, and 10L/m3 respectively. The maximum gas treatment capacity was about 100L/min, and residence time was close to 10s for the scrubber. The pre-agglomerating method were used to improve the particle capturing efficiency combined with spray technology. The composited method can realize the synchronous and efficient removal of multiple pollutants in a single scrubber. The possibility of application on ship was further increased.

Droughts can reduce the nitrogen retention capacity of catchments

Abstract. In 2018–2019, Central Europe experienced an unprecedented 2-year drought with severe impacts on society and ecosystems. In this study, we analyzed the impact of this drought on water quality by comparing long-term (1997–2017) nitrate export with 2018–2019 export in a heterogeneous mesoscale catchment. We combined data-driven analysis with process-based modeling to analyze nitrogen retention and the underlying mechanisms in the soils and during subsurface transport. We found a drought-induced shift in concentration–discharge relationships, reflecting exceptionally low riverine nitrate concentrations during dry periods and exceptionally high concentrations during subsequent wet periods. Nitrate loads were up to 73 % higher compared to the long-term load–discharge relationship. Model simulations confirmed that this increase was driven by decreased denitrification and plant uptake and subsequent flushing of accumulated nitrogen during rewetting. Fast transit times (&lt;2 months) during wet periods in the upstream sub-catchments enabled a fast water quality response to drought. In contrast, longer transit times downstream (&gt;20 years) inhibited a fast response but potentially contribute to a long-term drought legacy. Overall, our study reveals that severe droughts, which are predicted to become more frequent across Europe, can reduce the nitrogen retention capacity of catchments, thereby intensifying nitrate pollution and threatening water quality.