Soil-water Environment Research Articles

Top-down degradation of alpine meadow in the Qinghai-Tibetan Plateau: Gravelization initiate hillside surface aridity and meadow community disappearance

Alpine gravelization by glacier melting may subsequently cause degradation of downstream vegetation. The thinning rates of glaciers outside ice sheet peripheries in some regions has doubled over the past 20 years.However, no study is available about the effects of alpine gravelization on alpine meadow ecosystem. Here, by investigating and measuring the community characteristics, soil moisture, and soil temperature of alpine meadows under three different gravel coverage levels (No gravel covered meadow, half gravel covered meadow, and fully gravel covered meadow),we examine the response of surface microhabitats and community to gravel cover on a typical hillside alpine meadow. Results showed that gravel cover significantly decreased soil/gravel ratio and topsoil moisture. Topsoil water content of the half-covered and the fully-covered gravel meadow was outstandingly low and reached<8% and 5%, respectively. Meanwhile, the larger decrease rates for coverage (−72.53%), above- and below-ground biomass (−76.61% and −94.09%), community density (−81.76%), species richness (−77.75%) and diversity (−55.98%) were found after gravel cover. Gravel cover induced the changes of the dominant species composition from Kobresia pygmaea to Setaria viridis, and ultimately to Trigonotis peduncularis and Ranunculus pedatifidus. Cyperaceae functional group species almost disappeared with increasing gravel coverage. In general, the increase in gravel coverage caused a decrease in soil water content, coverage, above-ground and under-ground biomass, community density, species richness, and the disappearance of Cyperaceae functional group species.Our results provide a new insight into the effect of alpine gravelization on soil water environment and alpine meadow degradation.

Prodigiosin inhibits bacterial growth and virulence factors as a potential physiological response to interspecies competition.

Prodigiosin, a red linear tripyrrole pigment, has long been recognised for its antimicrobial property. However, the physiological contribution of prodigiosin to the survival of its producing hosts still remains undefined. Hence, the aim of this study was to investigate the biological role of prodigiosin from Serratia marcescens, particularly in microbial competition through its antimicrobial activity, towards the growth and secreted virulence factors of four clinical pathogenic bacteria (methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa) as well as Staphylococcus aureus and Escherichia coli. Prodigiosin was first extracted from S. marcescens and its purity confirmed by absorption spectrum, high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrophotometry (LC-MS/MS). The extracted prodigiosin was antagonistic towards all the tested bacteria. A disc-diffusion assay showed that prodigiosin is more selective towards Gram-positive bacteria and inhibited the growth of MRSA, S. aureus and E. faecalis and Gram-negative E. coli. A minimum inhibitory concentration of 10 μg/μL of prodigiosin was required to inhibit the growth of S. aureus, E. coli and E. faecalis whereas > 10 μg/μL was required to inhibit MRSA growth. We further assessed the effect of prodigiosin towards bacterial virulence factors such as haemolysin and production of protease as well as on biofilm formation. Prodigiosin did not inhibit haemolysis activity of clinically associated bacteria but was able to reduce protease activity for MRSA, E. coli and E. faecalis as well as decrease E. faecalis, Salmonella Typhimurium and E. coli biofilm formation. Results of this study show that in addition to its role in inhibiting bacterial growth, prodigiosin also inhibits the bacterial virulence factor protease production and biofilm formation, two strategies employed by bacteria in response to microbial competition. As clinical pathogens were more resistant to prodigiosin, we propose that prodigiosin is physiologically important for S. marcescens to compete against other bacteria in its natural soil and surface water environments.

Impact of Residue Incorporation on Soil Carbon Storage, Soil Organic Fractions, Microbial Community Composition and Carbon Mineralization in Rice-wheat Rotation – A Review

In agroecosystems, straw return is a useful management strategy for increasing soil fertility and crop productivity. The total organic carbon (TOC), dissolved organic C (DOC), and microbial biomass C (MBC) contents all increased significantly when compared to the no straw return (N) and straw return (S) treatments, while the easily oxidizable C content remained same. The S treatment resulted in a 28–52 percent increase in soil light fraction, light fraction organic C, and particle organic C over the N treatment. When compared to the N treatment, crop straw return increased total phospholipid fatty acid (PLFA), bacterial biomass, and actinomycete biomass by 52, 75, and 56 percent, respectively. Under short-term crop straw return, MBC and TOC were the two key determinants determining microbial populations. In comparison to residue removal, residue retention (RR) enhanced SOC storage by 11.3 percent. SOC content and contribution of macro-aggregates in the 0-20 cm depth and micro-aggregates in the 20-40 cm depth rose significantly when no-tillage and straw returns were used together. When no-tillage with straw returning (NTS) was used instead of CT, SOC content, mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimensions (FD) rose by 25%, 21%, 19%, and 12%, respectively, in the 0-20 cm depth. Soil micro-aggregates were greater in the 20-40 cm depth after CTS treatment. In the 0-20 cm depth, the percentages of macro- and micro-aggregates increased by 60% and 40%, respectively, under NTS. MWD, GMD, &gt; 5, 2-5, 1-2, and 0.25-0.5 mm aggregates all had a positive linear relationship with the SOC. Microbial biomass C (MBC) was considerably enhanced by 20.0 percent when compared to conventional tillage (CT) and no-tillage (NT), but total organic C (TOC), dissolved organic C (DOC), readily oxidizable C (EOC), and SOC of aggregates were not affected. MBC increased by 18.3% and SOC content of 2–1-mm aggregate increased by 9.4% when residue was returned. Total PLFAs grew by 9.8%, while fungal biomass increased by 40.8 percent, thanks to NT. Total PLFAs, bacterial biomass, fungal biomass, F/B, and MUFA/STFA were all increased by 31.1, 36.0, 95.9, 42.5, and 58.8 percent, respectively, while microbial stress was reduced by 45.9%. Wheat straw return had a considerable impact on the bacterial community in the soil, but not on the fungus community. It increased the relative abundance of the bacteria phylum Proteobacteria and the fungal phylum Zygomycota, while decreasing the relative richness of the bacterial phylum Acidobacteria and the fungal phylum Ascomycota. It increased the relative abundance of nitrogen-cycling bacterial taxa including Bradyrhizobium and Rhizobium, among others. This diversity includes bacteria, cyanobacteria, archaea, planctomycetes, and -proteobacteria, as well as endophytes. The system's intricacy and dynamic nature necessitate in-depth research on the three-part interactions between plants, microorganisms, and the soil-water environment.

By increasing infiltration and reducing evaporation, mulching can improve the soil water environment and apple yield of orchards in semiarid areas

Infiltration and evaporation are two important components of soil water balance in semiarid areas. For local orchards using drip irrigation, rainfall and irrigation events have a profound impact on soil infiltration and evaporation. As an effective water conservation technique, soil surface mulching is widely used in semiarid areas. The aim of this study was to investigate the effect of mulching (e.g., horticultural fabric mulching and corn straw mulching) on soil infiltration and evaporation after irrigation and rainfall. Through field experiments, we investigated soil infiltration and evaporation during three wet-dry cycles and for a rainy month and studied the effects of mulching on soil physical properties and apple yields. The results showed that both horticultural fabric mulching (FM) and straw mulching (SM) improved soil physical properties by reducing soil bulk density and increasing porosity and that SM had a better effect. Mulching increased infiltration after irrigation and heavy rain, while SM reduced infiltration when light rain occurred. Regardless of whether the soil was in the energy-limited stage or falling-rate stage, mulching can effectively reduce soil evaporation. We determined that the threshold of soil water content (SWC) between the energy-limited stage and falling-rate stage was 22.09–22.75%. When SWC is lower than the threshold, there is a positive significant correlation between evaporation and SWC, while no significant correlation was found when it is above the threshold. Moreover, mulching effectively increased apple yields and irrigation water use efficiency (IWUE) for three consecutive years. Therefore, both FM and SM have potential for application in orchards in semiarid areas to improve soil and moisture conditions in the root zone.

Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting conditions

Non-traditional stable isotope systems are increasingly used to study micronutrient cycling and acquisition in terrestrial ecosystems. We previously proposed for zinc (Zn) a conceptual model linking observed isotope signatures and fractionations to biogeochemical processes occurring in the rice soil environment and we suggested that 2’deoxymugineic acid (DMA) could play an important role for rice during the acquisition of Zn when grown under Zn limiting conditions. This proposition was sustained by the extent and direction of isotope fractionation observed during the complexation of Zn with DMA synthesised in our laboratory. Here we report a new set of experimental data from field and laboratory studies designed to further elucidate the mechanisms controlling Zn isotope fractionation in the rice rhizosphere and the role of DMA. First, we present acidity (pKa) and complexation (logK) constants for DMA with H+ and Zn2+, respectively, using synthetic 2’deoxymugineic acid and show that they are significantly different from previously published data using isolates from plants. Our new set of thermodynamic data allows for a more accurate calculation of the formation of ZnDMA complexes over pH ranges typically found in the rhizosphere of flooded lowland rice soils and in rice plant compartments (xylem, phloem). We show that at pH > 6.5, Zn is fully complexed by DMA and at pH <4.5 fully dissociated. This has important implications, i.e. that in alkaline paddy soils, DMA can strip Zn from soil solids (organic and inorganic) and that ZnDMA complexes are stable at the root interface if the pH is alkaline and in the phloem and xylem of the rice shoot. Second, we present a new set of Zn isotope data in rice grown in alkaline soils with low Zn availability with and without Zn addition. We used two genotypes not tested to date, i.e. A69–1, tolerant to low Zn supply, and IR26, sensitive to low Zn supply. We confirm previous findings that, in contrast to observations with rice grown in hydroponic studies, no isotopically light Zn is taken up into the shoot irrespective of Zn fertilization and that isotopically heavier Zn is taken up by rice grown in soils with low Zn supply. Third, we determined the isotope fractionation isotherm for Zn during absorption on goethite, representing the iron phase (plaque) typically forming on rice roots, in acidic solution. The negative Zn isotope fractionation observed (i.e., Δ66Zngoethite-solution < 0, where Δ66Zngoethite-solution = (δ66Zn of goethite) – (δ66Zn of solution)) is in contrast to the positive isotope fractionation (Δ66Zngoethite-solution > 0) detected during adsorption of Zn on goethite in alkaline solutions or between root and soil solution in rice grown in alkaline soils. We show that removal of different Zn species from solution and changes in the Zn coordination control extent and direction of isotope fraction during adsorption. Using the new set of results and combining it with recent findings from the literature, we present a refined conceptual model linking biogeochemical processes to Zn isotope fractionation in the rice soil system. Our results confirm the importance of root induced chemical changes in the rhizosphere of rice growing in soils with low Zn availability, demonstrate the unique ability of isotope signatures to deconvolve geochemical processes and conditions in the plant-soil environment and support the hypothesis of an important role of DMA in Zn acquisition under Zn limiting conditions.

Fabrication of NiS2 Nanomaterials for Cd2+ Sensing

Heavy metal Cadmium (Cd) will continuously pollute the atmosphere, soil and various water environments through material circulation, and even pose a threat to human safety. It has been designated as a first-class pollutant in sewage by China, therefore there is an urgent need to find new, more effective, and low-cost method to accurately detect Cadmium ion (Cd2+) concentration. We experimentally prepared a new Cd2+ sensor based on NiS2 nanomaterials capable of measuring Cd2+ concentration. The corresponding relationship between over potential of NiS2 nanomaterials in H2SO4 electrolyte solutions with different Cd2+ concentration and reduction peak with change of Cd2+ concentration was obtained by electrochemical method.

Variations in bacterial community structure and antimicrobial resistance gene abundance in cattle manure and poultry litter

Cattle manure and poultry litter are widely used as fertilizers as they are excellent sources of nutrients; however, potential adverse environmental effects exist during land applications, due to the release of zoonotic bacteria and antimicrobial resistance (AMR) genes. This study was conducted to understand linkages between physiochemical composition, bacterial diversity, and AMR gene presence of cattle manure and poultry litter using quantitative polymerase chain reaction to enumerate four AMR genes (ermB, sulI, intlI, and blactx-m-32), Illumina sequencing of the 16 S region, and analysis of physical and chemical properties. Principal coordinate analysis of Bray–Curtis distance revealed distinct bacterial community structures between the two manure sources. Greater alpha diversity occurred in cattle manure compared to poultry litter (P < 0.05). Redundancy analysis showed a strong relationship between manure physiochemical and composition and bacterial abundance, with positive relationships occurring among electrical conductivity and carbon/nitrogen, and negative associations for total solids and soluble fractions of heavy metals. Cattle manure exhibited greater abundance of macrolide (ermB) and sulfonamide (sulI) resistant genes. Consequently, fresh cattle manure applications may result in greater potential spread of AMR genes to the soil-water environment (relative to poultry litter) and novel best management strategies (such as composting) may reduce the release of AMR genes to the soil-water environment.

Subsurface irrigation with ceramic emitters: An effective method to improve apple yield and irrigation water use efficiency in the semiarid Loess Plateau

Apple trees consume a large amount of water, causing soil desiccation which reduces the land quality in the Loess Plateau. The development of efficient water-saving irrigation technology has become the main way to maintain apple production and prevent land degradation in this area. Subsurface irrigation with ceramic emitters (SICE) is an energy-efficient and water-saving technology for arid and semi-arid regions. However, the effectiveness of SICE for apple trees needs to be researched because of the special environment of the Loess Plateau. In this study, we determined the optimal buried depth of SICE tape, based on the soil water content (SWC), yield, water use efficiency (WUE) and irrigation water use efficiency (IWUE) of apple trees over a two-year field experiment. Results shown that SICE buried at a depth of 40 cm significantly improved new shoot length, yield, WUE and IWUE by 15.9%, 7.6%, 14.8% and 6.5% respectively compared to subsurface drip irrigation (SDI). Variations in SWC for SICE buried at a depth of 40 cm were smaller than those for SDI. SICE significantly enhanced yield through its ability to save water and increase soil temperature for apple trees. Our study shows that SICE did not only produce a suitable soil water environment and ensure stable growth of apple trees, but also saved more water resources.

Changes in rainfall partitioning and its effect on soil water replenishment after the conversion of croplands into apple orchards on the Loess Plateau

The partitioning of rainfall by plant canopies into throughfall (TF) and stemflow (SF) affects the process of rainfall infiltration into the soil as well as the ecological functions of soil water. A change in land use from croplands to orchards inevitably influences the preexisting rainfall partitioning and soil water replenishment processes. However, few studies have focused on the differences in TF and SF and their effects on soil water replenishment after converting croplands into apple orchards. Thus, the objectives of this study were to quantify the differences in TF and SF between maize (Zea mays L.) and apple trees (Malus domestica, cv. Fuji), clarify their influencing factors, and compare the efficiency of soil water replenishment by rainfall from June to September as well as the soil water content and storage in each hydrological year of the study. Under the same rainfall conditions, the rainfall was distributed differently due to the presence of the maize and apple tree canopies. The sum of the TF and SF in the maize field (129.1 mm and 167.6 mm) was lower than that in the apple orchard (250.4 mm and 354.2 mm) in 2017 and 2018, respectively; the TF amount in the apple orchard was on average 3.4 times that in the maize field, while the SF amount in the maize field was on average 12.9 times that in the apple orchard. The TF percentage ranged from 0 to 76.9 % and 0 to 97.9 % for the maize field and the apple orchard, respectively, while the SF percentage ranged from 0 to 37.5 % and 0 to 3.3 %. The soil water input sources for the maize field were TF and SF, while the input source for the apple orchard was mainly TF. TF and SF production increased linearly with rainfall in the apple orchard. The rainfall amount was identified as the variable with the greatest influence on rainfall partitioning among the rainfall factors considered. An increasing leaf area index resulted in decreasing relative TF but increasing relative SF for maize and decreasing relative TF and SF for apple trees. The mean efficiency of the replenishment of soil water by rainfall in the maize field (30.8 % and 37.4 % in 2017 and 2018, respectively) was slightly lower than that in the apple orchard (34.4 % and 41.0 %). This study provides insight into water cycle analyses aimed at understanding rainfall partitioning and the soil water environment within croplands converted into apple orchards on the Loess Plateau and in other, similar regions.

Poly- and Perfluoroalkyl Substances (PFAS) in the soil-water environment

Poly- and Perfluoroalkyl Substances (PFAS) in the soil-water environment

Review of Research Methods for Assessing the Activity of a Municipal Landfill Based on the Landfill Gas Analysis

Accurate projection of gas generation from landfills poses numerous difficulties. One needs to select and use an appropriate method from among several available options, and consider local and individual conditions of a landfill. These aspects are crucial for the economic management of the landfill gas in new landfills, and for assessing the impact of the gas on soil-water environment in old landfills. This paper is aimed at reviewing the research methods that can be used to assess the activity of new municipal waste landfills currently in operation, and of old, closed landfills after reclamation. Landfill activity can be assessed using different models and analysis of the produced gas. The actual data on the investigated municipal landfill showed that the landfill activity can be accurately assessed based on the quantitative determination of biogas formation using the LandGEM method, and the analysis of gas phase variability in the landfill accounting for oxygen, methane, carbon dioxide and hydrogen sulfide share/presence. Each landfill is different and calls for an individual approach or methodological modifications.

Effects of whole soil-plastic mulching system and fertilization rates on water consumption characteristics and yield of tartary buckwheat in arid land

<p indent=0mm>In order to study the effects of whole soil-plastic mulching planting and different fertilization rates on soil water consumption characteristics and yields of tartary buckwheat, a three-year (2015–2017) located experiment was carried out in semi-arid region of east-central Gansu Province, China, under whole soil-plastic mulching planting system. Four fertilization treatments under soil-plastic mulching were accordingly designed, including high application rate (HF, N <sc>120 kg</sc> hm^–2 + P₂O₅ <sc>90 kg</sc> hm^–2 + K₂O <sc>60 kg</sc> hm^–2), medium rate (MF, N <sc>80 kg</sc> hm^–2 + P₂O₅ <sc>60 kg</sc> hm^–2 + K₂O <sc>40 kg</sc> hm^–2), low rate (LF, N <sc>40 kg</sc> hm^–2 + P₂O₅ <sc>30 kg</sc> hm^–2 + K₂O <sc>20 kg</sc> hm^–2), and zero fertilization rate (ZF), whereas ZF with traditional non-mulching planting was set as the control (CK) to illustrate the effects of soil-plastic mulching and fertilization on water consumption characteristics, yields and water use efficiency (WUE) of tartary buckwheat in semi-arid area of China. The results showed that the effects of rainwater collection and soil moisture conservation were obvious after planting tartary buckwheat with whole soil-plastic mulching, which also improved soil water environment and increased pre-anthesis soil water storage (SWS, mm). LF was able to regulate soil water consumption before and after anthesis stage according to different precipitation years and soil moisture conditions. Compared with ZF, MF, HF, and CK in dry years, LF improved post-anthesis SWS by <sc>2.8–23.5 mm</sc> and increased crop pre-anthesis water consumption in the <sc>0–100 mm</sc> soil profile by <sc>26.3–32.4 mm</sc> in tartary buckwheat. As a result, LF increased total crop water consumption in the whole growth period by <sc>44.5 mm,</sc> and boosted water consumption module coefficient and intensity. Moreover, compared with ZF, MF, HF and CK, LF treatment increased dry matter weight at maturity stage by 1.2%–58.8%, leaf area index (LAI) at filling stage by 4.1%–68.5%, grain weight per plant by 1.6%–61.6%, plumpness rate by 0.6%–29.2%, biomass yield by 1.1%–182.5%, grain yield by 1.1%–130.4%, and water use efficiency (WUE, kg hm^–2 mm^–1) by 0.3%–102.7%, respectively. In conclusion, the storage effect of low amount fertilizer treatment for tartary buckwheat planting with whole soil-plastic mulching in dry land was obvious, which could achieve the coupling effects of soil moisture and fertilizer and regulate crop water consumption according to the environmental conditions such as precipitation during crop growth period, and it could significantly improve the biomass yield, grain yield and WUE of tartary buckwheat. Therefore, it was a suitable cultivation mode for yield-increasing and efficiency-boosting of tartary buckwheat in semi-arid area.

Critical effects on the photosynthetic efficiency and stem sap flow of poplar in the Yellow River Delta in response to soil water

To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture, two-year-old poplar saplings were selected and a packaged stem sap flow gauge, based on the stem-heat balance method, and a CIRAS-2 portable photosynthesis system were used. The results show that photosynthetic rates (Pn), transpiration rates (Tr), instantaneous water use efficiency (WUE) and the stem sap flow increased initially and then decreased with decreasing soil water, but their critical values were different. The turning point of relative soil water content (Wr) from stomatal limitation to nonstomatal limitation of Pn was 42%, and the water compensation point of Pn was 13%. Water saturation points of Pn and Tr were 64% and 56%, respectively, and the WUE was 71%. With increasing soil water, the apparent quantum yield (AQY), light saturation point (LSP) and maximum net photosynthetic rate (Pnmax) increased first and then decreased, while the light compensation point (LCP) decreased first and then increased. When Wr was 64%, LCP reached a lower value of 30.7 µmol m−2 s−1, and AQY a higher value of 0.044, indicating that poplar had a strong ability to utilize weak light. When Wr was 74%, LSP reached its highest point at 1138.3 µmol∙m−2 s−1, indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency. Stem sap flow and daily sap flow reached the highest value (1679.7 g d−1) at Wr values of 56% and 64%, respectively, and then declined with increasing or decreasing Wr, indicating that soil moisture significantly affected the transpiration water-consumption of poplar. Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels, and a Wr of 64–71% was classified to be at the level of high productivity and high efficiency. In this range, poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption. The saplings had characteristics of water tolerance and were not drought resistant. Full attention should be given to the soil water environment in the Yellow River Delta when planting Populus.

Evaluation of Responsivity to Drought Stress Using Infrared Thermography and Chlorophyll Fluorescence in Potted Clones of Cryptomeria japonica

As climate change progresses, the breeding of drought-tolerant forest trees is necessary. Breeding drought-tolerant trees requires screening for drought stress using a large number of individuals and a high-throughput phenotyping method. The aim of this study was therefore to establish high-throughput methods for evaluating the clonal stress responses to drought stress using infrared thermography and chlorophyll fluorescence methods in Cryptomeria japonica. The stomatal conductance index (Ig), maximum photochemical quantum yield of photosystem II (Fv/Fm), and axial growth of four plus-tree clones of C. japonica planted in pots were measured weekly for 85 days after irrigation was stopped. The phenotypic trait responsivity to drought stress was estimated by a nonlinear mixed model and by introducing the cumulative water index, which considers the past history of the soil water environment. These methods and procedures enabled us to evaluate the clonal stress responses in C. japonica and could be applied to large-scale clone materials to promote the breeding program for drought tolerance.

ШЛЯХИ ЗАБЕЗПЕЧЕННЯ ЕКОЛОГІЧНОЇ БЕЗПЕКИ МІСЦЬ ЗБЕРІГАННЯ ПАЛЬНО-МАСТИЛЬНИХ МАТЕРІАЛІВ АЕРОПОРТІВ

This paper considers the possibility of creating a system for monitoring the state of the components of the environment - atmospheric air, soil and underground water environment - during loading, pumping, storage of fuel and lubricants on the territory of airports during the operation of helicopter transport . An automated complex for ensuring environmental safety is proposed for monitoring the levels of pollution of atmospheric air, soils, underground aquifers during loading, pumping, storage of fuel and lubricants, their possible entry into the ground, and then through underground waters into the surface water layers. Taking into account the quantitative and qualitative characteristics of fuel and lubricants, indicators of harmful effects have been established in case of accidental intake of fuel and lubricants in the components of the environment. It was found that the greatest contribution to the level of environmental hazard is made by heavy metal ions due to intensive technogenic and chemical pollution of airport territories and adjacent areas. The degree of environmental risk during loading, pumping, storage of fuel and lubricants has been determined. The research resulted in an approach to the monitoring and management of technogenic and ecological risk and ecological safety of the components of the natural environment. A structural diagram of an automated complex for ensuring the environmental safety of the air and water environment has been developed, which monitors and informs about the state of the corresponding components of the environment in the territories of airports during the operation of helicopter transport using the mobile communication system (Global System for Mobile Communications GSM). Key words: fuel and lubricants, environmental safety, environmental risk, airports, monitoring, automated system

Ammonium Adsorption onto a Contaminated Soil-Water Environment Amended with Organic Matter

Ammonium Adsorption onto a Contaminated Soil-Water Environment Amended with Organic Matter

Estimating soil ammonium adsorption using pedotransfer functions in an irrigation district of the North China Plain

Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen (NH 4 + -N) in soil. Desorption and leaching of NH 4 + -N has led to pollution of natural waters. The adsorption of NH 4 + -N in soil plays an important role in the fate of the NH 4 + -N. Understanding the adsorption characteristics of NH 4 + -N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions (PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture (silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH 4 + -N adsorption capacity than sandy loam soils. Clay and silt contents significantly affected the adsorption capacity of NH 4 + -N in the different soils. The adsorption isotherms of NH 4 + -N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay, silt, and organic carbon contents and Fe 2+ and Fe 3+ ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH 4 + -N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH 4 + -N adsorption at a regional scale in irrigation districts.

Release and sedimentation behaviors of biochar colloids in soil solutions

The release of biochar colloids considerably affects the stability of biochar in environment. Currently, information on the release behavior and suspension stability of biochar colloids in real soil solutions is scarce. In this study, 20 soils were collected from different districts in China and the release behavior of biochar colloids and their suspension stability in soil solutions were systematically examined. The results showed that both pyrolysis temperature and biomass source had important effects on the formation of biochar colloids in soil solutions. The formation amount of biochar colloids from low pyrolysis temperatures (400 °C) (average amount of 9.33–16.41 mg/g) were significantly higher than those from high pyrolysis temperatures (700 °C) (average amount of less than 2 mg/g). The formation amount of wheat straw-derived biochar colloids were higher than those of rice straw-derived biochar colloids probably due to the higher O/C ratio in wheat-straw biochar. Further, biochar colloidal formation amount was negatively correlated with comprehensive effect of dissolved organic carbon, Fe and Al in soil solutions. The sedimentation curve of biochar colloids in soil solutions is well described by an exponential model and demonstrated high suspension stability. Around 40% of the biochar colloids were maintained in the suspension at the final sedimentation equilibrium. The settling efficiency of biochar colloids was positively correlated with comprehensive effect of the ionic strength and K, Ca, Na, and Mg contents in soil solutions. Our findings help promote a deeper understanding of biochar loss and stability in the soil-water environment.

Effects of particle size and surface chemistry on plastic nanoparticle transport in saturated natural porous media

Plastic nanoparticles (PNPs) are considered contaminants of emerging concern, but little information is available on their transport behavior in the soil-water environment, as well as their behavior relative to metal and other carbon-based nanoparticles. Here we show that size and surface functional groups affect the transport of polystyrene nanoparticles (PS-NPs) through saturated soil. Unmodified 110 nm and 50 nm PS-NPs demonstrated similar transport patterns in soil. However, a maximum elution value of 90% from the soil was found for the 50 nm PS-NPs, compared to a maximum value of ∼45% for 110 nm PS-NPs. The breakthrough curve for 190 nm PS-NPs demonstrated a maximum elution value of 60% from the soil. PS-NPs with surface functional groups display different mobility profiles: carboxylated PS-NPs demonstrated a plateau of 40% elution from the soil, while aminated PS-NPs were eluted only in small amounts and showed a spike pattern of elution from the column. These findings are attributed to the effects of common soil constituents such as calcium cations and humic acids on the size and charge of the PS-NPs with surface functional groups. Overall, PS-NP mobility in soil can vary widely, depending on PNP properties such as size and surface chemistry, and on matrix properties, such as the type of porous medium and its composition. These findings suggest that knowledge of inherent characteristics (size, surface charge, surface functional groups) of PNPs are required to elucidate the behavior of such particles in soil-water environments, and predict the extent of contaminant spreading.

Hydrologic modeling to examine the influence of the forestry reclamation approach and climate change on mineland hydrology

Forests in the Appalachian region of the U.S. are threatened by a variety of short- and long-term pressures, including climate change, invasive species, and resource extraction. Surface mining for coal is one of the most important drivers of land-use change in the region, reducing native forest cover, causing forest fragmentation, eliminating intact soil, and affecting water resources. The Forestry Reclamation Approach (FRA) has been demonstrated as a successful best practice for restoring forests on mine-impacted landscapes, but little information exists on how the practice will affect hydrologic processes. A study was initiated to examine soil-water movement, as in-situ saturated hydraulic conductivity (Ksat), combined with soil porosity to quantify the potential influence on streamflow of reclaimed mines relative to an unmined, forested control site in eastern Kentucky. We compared different reclamation techniques and time since reclamation to determine the extent to which hydrologic function can be restored. We also simulated evapotranspiration at the watershed scale as a function of reclamation technique for both historical and projected (2050) climate. Results indicate that conventional grassland reclamation critically changes how soil water transitions to streamflow, primarily due to Ksat variability that exceeds that measured for intact and FRA soils. Sites reclaimed using FRA exhibited a soil-water environment that was more similar to the unmined control. However, all reclaimed mine soils were thinner, retained and stored less soil water, and thus could provide less plant-available water during the growing season. The plant-available water stored in reclaimed landscapes may not be sufficient to support forest health and this is exacerbated by projected climate conditions. However, soil development under a combination of FRA techniques has the potential to mitigate this limitation.