Understanding the drivers of community structure is fundamental for adequately managing ecosystems under global change. Here we used a large dataset of eighty-four headwater stream sites in three catchments in the Eastern Highlands of Zimbabwe, which represent a variety of abiotic conditions and levels of impairment, to examine the drivers of benthic macroinvertebrate community structure. We focused our assessment on macroinvertebrate family level community composition and functional feeding group classifications. Taxonomic richness was weakly positively correlated with ammonium, phosphates and pH, and weakly negatively correlated with detrital cover and dissolved oxygen. Measured abiotic variables, however, had limited influence on both macroinvertebrate diversity and functional feeding group structure, with the exception of ammonium, channel width and phosphates. This reflected the fact that many macroinvertebrate families and functional feeding guilds were well represented across a broad range of habitats. Predatory macroinvertebrates were relatively abundant, with collector-filterers having the lowest relative abundances. The findings of the study suggest that for certain ecological questions, a more detailed taxonomic resolution may be required to adequately understand the ecology of aquatic macroinvertebrates within river systems. We further recommend management and conservation initiatives on the Save River system, which showed significant impact from catchment developmental pressures, such as urbanisation, agriculture and illegal mining.
The conversions of forests and grass land to urban and farmland has exerted significant changes on terrestrial ecosystems. However, quantifying how these changes can affect the quality of water resources is still a challenge for hydrologists. Nitrate concentrations can be applied as an indicator to trace the link between land use changes and groundwater quality due to their solubility and easy transport from their source to the groundwater. In this study, 25year records (from 1989 to 2014) of nitrate concentrations are applied to show the impact of land use changes on the quality of groundwater in Northern Kelantan, Malaysia, where large scale deforestation in recent decades has occurred. The results from the integration of time series analysis and geospatial modelling revealed that nitrate (NO3-N) concentrations significantly increased with approximately 8.1% and 3.89% annually in agricultural and residential wells, respectively, over 25years. In 1989 only 1% of the total area had a nitrate value greater than 10mg/L; and this value increased sharply to 48% by 2014. The significant increase in nitrate was only observed in a shallow aquifer with a 3.74% annual nitrate increase. Based on the result of the Autoregressive Integrated Moving Average (ARIMA) model the nitrate contamination is expected to continue to rise by about 2.64% and 3.9% annually until 2030 in agricultural and residential areas. The present study develops techniques for detecting and predicting the impact of land use changes on environmental parameters as an essential step in land and water resource management strategy development.
This study explores diatom community dynamics in a highly modified semi-arid temperate region river system characterised by inconsistent river flow. Various water and sediment environmental variables were assessed using a multi-faceted analysis approach to determine the spatio-temporal drivers of benthic diatom communities in the river system. Overall, the diatom community was generally dominated by pollution tolerant species, reflecting the anthropogenic intensity and activities on the river system. Diatom community composition was found to be largely determined by water column chemistry variables particularly nutrient concentrations in comparison to sediment chemistry and physical variables. Strong seasonal diatom species composition was also observed and this was driven by strong seasonal variations in nutrient loads and metal concentrations, a result of the variable water flow across the two seasons. However, the greater temporal variation in communities was observed in the smaller systems with the mainstream river system being more homogenous over time. In addition, diatom community composition and environmental variables were found to be different and more pronounced between streams and mainstream sites, than between canals and streams. The study highlights the complex interaction between water column, sediment and physical variables in determining the diatom species composition in small river systems. It also highlights the importance of river flow inconsistency as an indirect variable that alters primary drivers such as nutrient concentrations in the water column and heavy metal levels in the sediment.
Tanjung Karang, Selangor, is widely known for its paddy cultivation activity and hosts the third largest paddy field in Malaysia. Pesticides contamination in agriculture fields has become an unavoidable problem, as pesticides are used to increase paddy productivity and reduce plant disease. Human exposure to agrichemicals is common and could results in both acute and chronic health effects, such as acute and chronic neurotoxicity. This study aims to determine the concentrations of commonly used pesticides (azoxystrobin, buprofezin, chlorantraniliprole, difenoconazole, fipronil, imidacloprid, isoprothiolane, pretilachlor, propiconazole, pymetrozine, tebuconazole, tricyclazole, and trifloxystrobin) in personal air samples and their associated health risks among paddy farmers. Eighty-three farmers from Tangjung Karang, Selangor were involved in this study. A solid sorbent tube was attached to the farmer's breathing zone with a clip, and an air pump was fastened to the belt to collect personal air samples. Pesticides collected in the XAD-2 resin were extracted with acetone, centrifuged, concentrated via nitrogen blowdown and reconstituted with 1mL of 3:1 ultrapure water/HPLC-grade methanol solution. The extract was analyzed using ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The target compounds were detected with a maximum concentration reaching up to 462.5ngm-3 (fipronil). The hazard quotient (HQ) was less than 1 and the hazard index (HI) value was 3.86×10-3, indicating that the risk of pesticides related diseases was not significant. The lifetime cancer risk (LCR) for pymetrozine was at an acceptable level (LCR<10-6) with 4.10×10-8. The results reported in this study can be beneficial in terms of risk management within the agricultural community.
Water pollution is a critical management issue, with many rivers and streams draining urban areas being polluted by the disposal of untreated solid waste and wastewater discharge, storm water and agricultural runoff. This has implications for biodiversity, and many rivers in the developing world are now considered compromised. We investigated benthic macroinvertebrate community structure and composition in relation to physico-chemical conditions of the water column and sediments. The study was conducted in an Austral catchment subject to both urban and agricultural pollutants in two different seasons. We assessed whether sediment characteristics were more important drivers of macroinvertebrate community composition than water column characteristics. We expected clear differences in macroinvertebrate community composition and in the associated community metrics due to distinct flow conditions between the two seasons. A combination of multivariate analyses (canonical correspondence analysis (CCA)) and biological indicator analysis were used to examine these patterns. Chironomidae was the most abundant family (>60%) in the upper mainstem river and stream sites. Stream sites were positively associated with CCA axis 2, being characterised by high turbidity and lower pH, salinity, phosphate concentration, channel width and canopy cover. Canopy cover, channel width, substrate embeddedness, phosphate concentration, pH, salinity and turbidity all had a significant effect on macroinvertebrate community composition. Using CCA variation partitioning, water quality was, however, a better predictor of benthic macroinvertebrate composition than sediment chemical conditions. Furthermore, our results suggest that seasonality had little effect on structuring benthic macroinvertebrate communities in this south-eastern zone of South Africa, despite clear changes in sediment chemistry. This likely reflects the relative lack of major variability in water chemistry compared to sediment chemistry between seasons and the relatively muted variability in precipitation between seasons than the more classic Austral temperate climates.
Exposure to secondhand smoke (SHS) can affect fetal brain development as well as subsequent neurodevelopment. This study aimed to determine the association between prenatal and postnatal SHS exposure with children's neurodevelopment at 2years of age. Among 107 mother-child pairs from a Malaysia prospective cohort, prenatal and postnatal SHS exposure was determined based on maternal and child hair nicotine concentrations. Multiple linear regressions were used to determine the association between prenatal and postnatal levels of nicotine in maternal and children's' hair with children's neurodevelopment. After adjustment for confounders, prenatal nicotine concentration levels were negatively associated with communication (β=-2.059; p=0.015) and fine motor skills (β=-2.120; p=0.002) while postnatal nicotine concentration levels were inversely associated with fine motors (β=-0.124; p=0.004) and problem solving skills (β=-0.117; p=0.013). In conclusion, this study suggests that early life exposure to SHS may affect children's neurodevelopment.
No report was found on the occurrence of microplastics in processed seafood products that are manufactured for direct human consumption. This study investigates the potential presence of micro- and mesoplastics in 20 brands of canned sardines and sprats originating from 13 countries over 4 continents followed by their chemical composition determination using micro-Raman spectroscopy. The particles were further inspected for their inorganic composition through energy-dispersive X-ray spectroscopy (EDX). Plastic particles were absent in 16 brands while between 1 and 3 plastic particles per brand were found in the other 4 brands. The most abundant plastic polymers were polypropylene (PP) and polyethylene terephthalate (PET). The presence of micro- and mesoplastics in the canned sardines and sprats might be due to the translocation of these particles into the edible tissues, improper gutting, or the result of contamination from the canneries. The low prevalence of micro- and mesoplastics sized >149μm, and the absence of potentially hazardous inorganic elements on them, might indicate the limited health risks associated with their presence in canned sardines and sprats. Due to the possible increase in micro- and mesoplastic loads in seafood products over time, the findings of this study suggest their quantification to be included as one of the components of food safety management systems.
Microplastics are important novel pollutants in freshwaters but their behaviour in river sediments is poorly understood due to the large amounts of coloured dissolved organic matter that impede sample processing. The present study aimed to 1.) estimate the microplastic pollution dynamics in an urban river system experiencing temporal differences in river flow, and 2.) investigate the potential use of chironomids as indicators of microplastic pollution levels in degraded freshwater environments. Microplastic levels were estimated from sediment and Chironomus spp. larvae collected from various sites along the Bloukrans River system, in the Eastern Cape South Africa during the summer and winter season. River flow, water depth, channel width, substrate embeddedness and sediment organic matter were simultaneously collected from each site. The winter season was characterised by elevated microplastic abundances, likely as a result of lower energy and increased sediment deposition associated with reduced river flow. In addition, results showed that particle distribution may be governed by various other external factors, such as substrate type and sediment organic matter. The study further highlighted that deposit feeders associated with the benthic river habitats, namely Chironomus spp. ingest microplastics and that the seasonal differences in sediment microplastic dynamics were reflected in chironomid microplastic abundance. There was a positive, though weakly significant relationship between deposit feeders and sediment suggesting that deposit feeders such as Chironomus spp. larvae could serve as an important indicator of microplastic loads within freshwater ecosystems.
Air pollution can be detected through rainwater composition. In this study, long-term measurements (2000-2014) of wet deposition were made to evaluate the physicochemical interaction and the potential sources of pollution due to changes of land use. The rainwater samples were obtained from an urban site in Kuala Lumpur and a highland-rural site in the middle of Peninsular Malaysia. The compositions of rainwater were obtained from the Malaysian Meteorological Department. The results showed that the urban site experienced more acidity in rainwater (avg=277mm, range of 13.8 to 841mm; pH=4.37) than the rural background site (avg=245mm, range of 2.90 to 598mm; pH=4.97) due to higher anthropogenic input of acid precursors. The enrichment factor (EF) analysis showed that at both sites, SO42-, Ca2+ and K+ were less sensitive to seawater but were greatly influenced by soil dust. NH4+ and Ca2+ can neutralise a larger fraction of the available acid ions in the rainwater at the urban and rural background sites. However, acidifying potential was dominant at urban site compared to rural site. Source-receptor relationship via positive matrix factorisation (PMF 5.0) revealed four similar major sources at both sites with a large variation of the contribution proportions. For urban, the major sources influence on the rainwater chemistry were in the order of secondary nitrates and sulfates>ammonium-rich/agricultural farming>soil components>marine sea salt and biomass burning, while at the background site the order was secondary nitrates and sulfates>marine sea salt and biomass burning=soil components>ammonia-rich/agricultural farming. The long-term trend showed that anthropogenic activities and land use changes have greatly altered the rainwater compositions in the urban environment while the seasonality strongly affected the contribution of sources in the background environment.
A comprehensive study was conducted to identify the salinization origins and the major hydrogeochemical processes controlling the salinization and deterioration of the Gaza coastal aquifer system through a combination approaches of statistical and geostatistical techniques, and detailed hydrogeochemical assessments. These analyses were applied on ten physicochemical variables for 219 wells using STATA/SE12 and Surfer softwares. Geostatistical analysis of the groundwater salinity showed that seawater intrusion along the coastline, and saltwater up-coning inland highly influenced the groundwater salinity of the study area. The hierarchical cluster analysis (HCA) technique yielded seven distinct hydrogeochemical signature clusters; (C1&C2: Eocene brackish water invasion, C3 saltwater up-coning, C4 human inputs, C5 seawater intrusion, C6 & C7 rainfall and mixing inputs). Box plot shows a wide variation of most of the ions while Chadha's plot elucidates the predominance of Na-Cl (71.6%) and Ca/Mg-Cl (25%) water types. It is found that, the highest and the lowest levels of salinization and the highest level of nitrate pollution were recorded in the northern area. This result reflects the sensitivity of this area to the human activities and/or natural actions. Around 90.4% of the wells are nitrate polluted. The main source of nitrate pollution is the sewage inputs while the farming inputs are very limited and restricted mostly in the sensitive northern area. Among the hydrogeochemical processes, ion exchange process was the most effective process all over the study area. Carbonate dissolution was common in the study area with the highest level in clusters 6, 7, 4 and 2 in the north while Gypsum dissolution was significant only in cluster 1 in the south and limited in the other clusters. This integrated multi-techniques research should be of benefit for effective utilization and management of the Gaza coastal aquifer system as well as for future work in other similar aquifers systems.
The municipal landfill is an example of human-made environment that harbours some complex diversity of microorganism communities. To evaluate this complexity, the structures of bacterial communities in active (operational) and closed (non-operational) landfills in Malaysia were analysed with culture independent metagenomics approaches. Several points of soil samples were collected from 0 to 20cm depth and were subjected to physicochemical test, such as temperature, pH, and moisture content. In addition, the heavy metal contamination was determined by using ICPMS. The bacterial enumeration was examined on nutrient agar (NA) plates aerobically at 30°C. The soil DNA was extracted, purified and amplified prior to sequence the 16S rRNA gene for statistical and bioinformatics analyses. As a result, the average of bacteria for the closed landfill was higher compared to that for the active landfill at 9.16×107 and 1.50×107, respectively. The higher bacterial OTUs sequenced was also recorded in closed landfills compared to active landfill i.e. 6625 and 4552 OTUs respectively. The data from both landfills showed that the predominant phyla belonged to Proteobacteria (55.7%). On average, Bacteroidetes was the second highest phylum followed by Firmicutes for the active landfill. While the phyla for communities in closed landfill were dominated by phyla from Acidobacteria and Actinobacteria. There was also Euryarchaeota (Archaea) which became a minor phylum that was detected in active landfill, but almost completely absent in closed landfill. As such, the composition of bacterial communities suggests some variances between the bacterial communities found in active and closed landfills. Thus, this study offers new clues pertaining to bacterial diversity pattern between the varied types of landfills studied.
This study investigates how field practices in handling and applying pesticides influence the long-term patterns of professional agricultural operators' exposure to pesticides. It presents the first use of a comprehensive pesticide application dataset collected on behalf of the European Food Safety Authority with 50 operators selected to cover arable and orchard cropping systems in Greece, Lithuania and the UK. Exposure was predicted based on the harmonised Agricultural Operator Exposure Model (AOEM) and compared with Acceptable Operator Exposure Levels (AOELs). The amount of pesticides handled by individual operators across a cropping season was largest in the UK arable and orchard systems (median 580 and 437kg active substance, respectively), intermediate for the arable systems in Greece and Lithuania (151 and 77kg, respectively), and smallest in the Greek orchard system (22kg). Overall, 30 of the 50 operators made at least one application within a day with predicted exposure greater than the AOEL. The rate of AOEL exceedance was greatest in the Greek cropping systems (8 orchard operators, 2.8-16% of total applications; 7 arable operators, 1.1-14% of total applications), and least for the Lithuanian arable system (2 operators, 2.9-4.5% of total applications). Instances in Greece when predicted exposure exceed the AOEL were strongly influenced by the widespread use of wettable powder formulations (>40% of the total pesticide active substance handled for 11 of the 20 Greek operators). In contrast, the total area of land treated with an active substance on a single day was more important in the UK and Lithuania (95th percentile observed value was 132 and 19haday-1 for UK arable and orchard systems, respectively). Study findings can be used to evaluate current assumptions in regulatory exposure calculations and to identify situations with potential risk that require further analysis including measurements of exposure to validate model estimations.
Antibiotic residues in swine manure when entered the soil would most likely affect the complex composition and functions of the soil microbiome, which is also responsible for degrading these antibiotics. Three different methods of adding ciprofloxacin (CIP), a common antibiotic used in the swine industry, to the soil were used to investigate the effects of CIP on the soil microbiome and the degradation of CIP. Results of the study showed that the microbiome could promote the degradation of CIP in the soil when CIP was incorporated into the soil together with manure. However, the CIP degradation time was prolonged when adding the manure of swine fed with diet containing CIP in the soil. All treatments did not affect the copy number of the resistance genes, except for aac(6')-Ib-cr, as compared with the initial numbers of each treatment. MiSeq Illumina sequencing and Biolog-ECO microplates results showed that CIP had a significant effect on the abundance, structure, and function of the soil microbiome, but different addition methods resulted in distinct effects. Results of the present study demonstrated that the microbiome and fate of CIP responded differently to the different methods of adding CIP to the soil.
Microwave vacuum pyrolysis of palm kernel shell (PKS) was performed to produce biochar, which was then tested as bio-fertilizer in growing Oyster mushroom (Pleurotus ostreatus). The pyrolysis approach produced biochar containing a highly porous structure with a high BET surface area of up to 270m2/g and low moisture content (≤10wt%), exhibiting desirable adsorption properties to be used as bio-fertilizer since it can act as a housing that provides many sites on which living microorganisms (mycelium or plant-growth promoting bacteria) and organic nutrients can be attached or adsorbed onto. This could in turn stimulate plant growth by increasing the availability and supply of nutrients to the targeted host plant. The results from growing Oyster mushroom using the biochar recorded an impressive growth rate and a monthly production of up to about 550g of mushroom. A shorter time for mycelium growth on one whole baglog (21days) and the highest yield of Oyster mushroom (550g) were obtained from cultivation medium added with 20g of biochar. Our results demonstrate that the biochar-based bio-fertilizer produced from microwave vacuum pyrolysis of PKS shows exceptional promise as growth promoting material for mushroom cultivation.
This study aimed to measure the equilibrium equivalent radon (EECRn) concentration in an old building (Building-1) and a new building (Building-2) with mechanical ventilation and a natural ventilation system, respectively. Both buildings were located at the campus of University Kebangsaan Malaysia. The concentration of indoor radon was measured at 25 sampling stations using a radon detector model DOSEman PRO. The sampling was conducted for 8 h to represent daily working hours. A correlation of the radon concentration was made with the annual inhalation dose of the occupants at the indoor stations. The equilibrium factor and the annual effective dose on the lung cancer risks of each occupant were calculated at each sampling station. The average equilibrium equivalent radon measured in Building-1 and Building-2 was 2.33 ± 0.99 and 3.17 ± 1.74 Bqm-3, respectively. The equilibrium factor for Building 1 ranged from 0.1053 to 0.2273, and it ranged from 0.1031 to 0.16 for Building 2. The average annual inhalation doses recorded at Building-1 and Building-2 were 0.014 ± 0.005 mSv y-1and 0.020 ± 0.013 mSv y-1, respectively. The annual effective dose for Building-1 was 0.034 ± 0.012 mSv y-1, and it was 0.048 ± 0.031 mSv y-1for Building-2. The values of equilibrium equivalent radon concentration for both buildings were below the standard recommended by the International Commission on Radiological Protection (ICRP). However, people may have different radon tolerance levels. Therefore, the inhalation of the radon concentration can pose a deleterious health effect for people in an indoor environment.
The coral reefs of the Persian Gulf are the most diverse systems of life in the marine environment of the Middle East. Unfortunately, they are highly threatened by local and global stressors, particularly oil pollutants. This is the first quantitative and qualitative study aimed at assessing the concentration and sources of n-alkanes and POPs (PAHs, PCBs and PCNs) in coral tissues, symbiotic algae (zooxanthellae), reef sediments and seawaters in coral reefs of Lark and Kharg in the Persian Gulf, Iran. This work was conducted on eight species of six genera and three families of hard corals and one family of soft coral. A significant variation in the concentration of ∑30n-alkanes and POPs (∑40PAHs, ∑22PCBs and 20PCNs) was found in the decreasing order: zooxanthellae > coral tissue > skeleton > reef sediment > seawater. The bioaccumulation of these compounds was 2-times higher in ahermatypic than in hermatypic corals, among which significant variations were observed in both sites. In Kharg, Porites lutea had the highest mean concentration of ∑30n-alkanes and ∑40PAHs in soft tissue, whereas the lowest values were in Platygyra daedalea. A contrasting trend was documented for ∑22PCBs and 20PCNs, with the highest level reported in soft tissue of P. daedalea and the lowest in P. lutea at Kharg. Compositional pattern of AHs and PAHs demonstrated the predominance of LMW-PAHs and n-alkanes. In skeleton and reef sediments, tetra, penta and tri-CBs were the most abundant PCBs congeners followed by di-CB > hexa-CB > hepta-CB > octa-CB,whiletri-CB > di-CB > tetra-CB > penta-CB > hexa-CB > hepta-CB > octa-CB was observed for soft tissue, zooxanthellae and seawater. The results of RAD test indicated significantly negative correlation between total concentration of these compounds with zooxanthellae density, the chlorophyll-a and C2 in corals at both reefs. This is the first report on levels, health assessment and source apportionments of POPs in zooxanthellae and a first step in the implementation of specific coral reef management measures.
In many regions around the world, there are issues associated with groundwater resources due to human and natural factors. However, the relation between these factors is difficult to determine due to the large number of parameters and complex processes required. In order to understand the relation between land use allocations, the intrinsic factors of the aquifer, climate change data and groundwater chemistry in the multilayered aquifer system in Malaysia's Northern Kelantan Basin, twenty-two years hydrogeochemical data set was used in this research. The groundwater salinisation in the intermediate aquifer, which mainly extends along the coastal line, was revealed through the hydrogeochemical investigation. Even so, there had been no significant trend detected on groundwater salinity from 1989 to 2011. In contrast to salinity, as seen from the nitrate contaminations there had been significantly increasing trends in the shallow aquifer, particularly in the central part of the study area. Additionally, a strong association between high nitrate values and the areas covered with palm oil cultivations and mixed agricultural have been detected by a multiple correspondence analysis (MCA), which implies that the increasing nitrate concentrations are associated with nitrate loading from the application of N-fertilisers. From the process of groundwater salinisation in the intermediate aquifer, could be seen that it has a strong correlation the aquifer lithology, specifically marine sediments which are influenced by the ancient seawater trapped within the sediments.
Southeast Asian haze is a semi-natural phenomenon that chokes the region each year during the dry monsoon season. Smoke-haze episodes caused by the vegetation and peat fires in Indonesia severely affected large parts of Malaysia during the 2015 El Niño phenomenon. This study aimed to evaluate the factors that influenced the concentrations of aerosol and trace gases during the 2015 haze and non-haze period on a semi-urban site in the southern part of Malaysian peninsula that facing Sumatra (Muar, Site A), and on an urban site near to Kuala Lumpur, influenced by the city centre (Cheras, Site B). Local land use data and the cluster of air mass weighted backward trajectory were used to identify the potential factors from local sources and the transboundary region, respectively. The annual median concentrations of PM10 for semi-urban and urban sites were 45.0μg/m3 and 47.0μg/m3, respectively for the study period (Jan-Dec 2015) from the hourly observation dataset. The highest PM10 concentrations during the haze were 358μg/m3 and 415μg/m3 for the two sites, respectively, representing absolutely unhealthy air. However, the trace gases were within the safe threshold. The average concentrations of PM10 and carbon monoxide were two fold higher during the haze than the non-haze episodes on both sites. Nitrogen dioxide was more influenced by haze compared with sulphur dioxide and ozone. The results of the land use change suggest that the local factor can also partially affect the air pollution on the urban area (Site B) but more visible in 2015. The results of the backward trajectory and the wildfire radiative power showed that the smoke-haze episodes that affected Malaysia in 2015 were mainly initiated in the Indonesian Sumatra and Kalimantan regions. This study provides a very useful information towards the impacted region during El Niño haze episode.
Contaminants of Emerging Concerns (CECs) have been introduced as one type of recalcitrant pollutant sources in water. In this study, the non-steroidal anti-inflammatory drug diclofenac (DCF) has been removed from water solutions using Molecularly Imprinted Polymer (MIP), synthetized via bulk polymerization with allylthiourea (AT) as the functional monomer and using DCF as template (MIP-DCF). DCF detection has been performed by UV spectrophotometer. From the kinetic study in batch mode, approximately 100% of removal is observed by using 10mg of MIP-DCF, with an initial concentration of 5mg/L of DCF at pH7, within 3min and agitated at 25°C. In continuous flow mode study, using a cartridge pre-packed with 10mg of MIP-DCF, a high adsorption capacity of 160mgDCF/g MIP was obtained. To study the porosity of MIPs, scanning electron microscopy (SEM) has been used. In order to characterize the chemical interaction between monomer and template, the pre-polymerization mixture for MIP and DCF has also been studied by 1H NMR. One of the chemical shift observed has been related to the formation of a complex between amine protons of thiourea group of AT with carboxylic acid on DCF. In conclusion, the developed MIP works as a good adsorbent for DCF removal, and is selective to DCF in the presence of indomethacin and ibuprofen.
Atmospheric deposition nitrogen (ADN) increases the N content in soil and subsequently impacts microbial activity of soil. However, the effects of ADN on paddy soil microbial activity have not been well characterized. In this study, we studied how red paddy soil microbial activity responses to different contents of ADN through a 10-months ADN simulation on well managed pot experiments. Results showed that all tested contents of ADN fluxes (27, 55, and 82kgNha-1 when its ratio of NH4+/NO3--N (RN) was 2:1) enhanced the soil enzyme activity and microbial biomass carbon and nitrogen and 27kgNha-1 ADN had maximum effects while comparing with the fertilizer treatment. Generally, increasing of both ADN flux and RN (1:2, 1:1 and 2:1 with the ADN flux of 55kgNha-1) had similar reduced effects on microbial activity. Furthermore, both ADN flux and RN significantly reduced soil bacterial alpha diversity (p<0.05) and altered bacterial community structure (e.g., the relative abundances of genera Dyella and Rhodoblastus affiliated to Proteobacteria increased). Redundancy analysis demonstrated that ADN flux and RN were the main drivers in shaping paddy soil bacteria community. Overall, the results have indicated that increasing ADN flux and ammonium reduced soil microbial activity and changed the soil bacterial community. The finding highlights how paddy soil microbial community response to ADN and provides information for N management in paddy soil.