Current Situation and Prevention of Soil Erosion from Construction of West-East Natural Gas Transmission (Ningxia-Shaanxi Section)

In the research, problems and damages of soil erosions in West -East Natural Gas Transmission were analyzed; the reasons were summarized and the characteristics of soil erosion were researched in order to explore principles of pipeline prevention and seek countermeasures.

Geochemical characteristics of soil gas in the Yanhuai basin,northern China

The geochemical backgrounds and origins of soil gases in the Yanhuai basin are discussed based on the regional seismogeological data and concentrations of Rn, Hg, CO2, H2, He and CH4 in soil gas measured at 422 investigating sites in field during September to October 2007. The geochemical background values of Rn, Hg, CO2, H2, He and CH4 are （8105.8±5937.4） Bq/m^3, （9.7±5.8） ng/m^3, （395.9±35.3）×10^-6, （4.0±2.3）×10^-6, （15.9±10.4）×10^-6 and （12.7±8.1）×10^-6, respectively. The geochemical backgrounds of the soil gases are higher in the eastern part of the Yanhuai basin. The main factors affecting the gasgeochemical backgrounds are gaseous origins, structure of the crust, faults, straaun and microbe activity. The higher values of gasgeochemical backgrounds in the eastern part are attributed to the existence of low-velocity zones in the upper crust, stronger tectonic activity and more contributions of Hg and He derived from the deep-earth and Rn origi- nated from granite, corresponding to stronger seismic activity. The results can be applied to identifying seismic precursor from monitoring data of gases in the studied area.

Effects of soil drought stress on photosynthetic gas exchange traits and chlorophyll fluorescence in Forsythia suspensa

To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.

Comparisons of the effects of different drying methods on soil nitrogen fractions:Insights into emissions of reactive nitrogen gases(HONO and NO)

Reactive nitrogen(Nr)emission from soils,e.g.,nitrous acid(HONO)and nitric oxide(NO),is a key process of the global nitrogen(N)cycle and has significant implications for atmospheric chemistry.To understand the underlying mechanisms of soil Nr emissions,air-dried or oven-dried soils are commonly used in the laboratory.To date,few studies have compared the effects of different drying methods on soil Nr gas fluxes and N fractions.Here,the authors studied soil water content,pH,(in)organic N content,and Nr gas fluxes of air-dried,freeze-dried,oven-dried,and fresh soils from different land-use types.The results showed that the soil pH of air-dried and oven-dried samples was significantly lower compared with fresh soil from farmland and grassland,but higher compared with forest soil.The difference in soil pH between freeze-dried and fresh soil(mean±standard deviation:0.52±0.31)was the lowest.In general,all drying methods increased the soil NH4+-N,NO3−-N,and dissolved organic N contents compared with fresh soil(P<0.05).The maximum HONO and NO flux and total emissions during a full wetting–drying cycle of fresh soil were also increased by air-drying and oven-drying(P<0.001),but comparable with freeze-dried soil(P>0.2).In conclusion,all drying methods should be considered for use in studies on the land–atmosphere interface and biogeochemical N cycling,whereas the freeze-drying method might be better for studies involving the measurement of soil Nr gas fluxes.

Effects of plastic film mulching on soil greenhouse gases(CO2,CH4 and N2O) concentration within soil profiles in maize fields on the Loess Plateau,China

To better understand the effects of plastic film mulching on soil greenhouse gases（GHGs） emissions,we compared seasonal and vertical variations of GHG concentrations at seven soil depths in maize（Zea mays L.） fields at Changwu station in Shaanxi,a semi-humid region,between 2012 and 2013.Gas samples were taken simultaneously every one week from non-mulched（BP） and plastic film-mulched（FM） field plots.The results showed that the concentration of GHGs varied distinctly at the soil-atmosphere interface and in the soil profile during the maize growing season（MS）.Both carbon dioxide（CO_2） and nitrous oxide（N_2O） concentrations increased with increasement of soil depth,while the methane（CH_4）concentrations decreased with increasement of soil depth.A strong seasonal variation pattern was found for CO_2 and N_2O concentrations,as compared to an inconspicuous seasonal variation of CH_4 concentrations.The mean CO_2 and N_2O concentrations were higher,but the mean CH_4 concentration in the soil profiles was lower in the FM plots than in the BP plots.The results of this study suggested that plastic film mulching significantly increased the potential emissions of CO_2and N_2O from the soil,and promoted CH_4 absorption by the soil,particularly during the MS.

Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar

Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention)of soil.However,variations in densities alter the properties of the soil ebiochar mix.Such density variations are observed in agriculture(loosely compacted)and engineering(densely compacted)applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with different densities.The major objective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS)with different biochar contents under varying degree of compaction(DOC)conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5%and 10%).All BAS samples were compacted at three DOCs(65%,80%and 95%)in polyvinyl chloride(PVC)tubes.Each soil column was subjected to dryingewetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability kg as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%)>k_(g,80%)>k_(g,95%))at a relatively low suction range(<200 kPa)because both biochar and compaction treatment reduce the connected pores.

Methane in soil gas and its transfer to the atmosphere in the Yakela condensed gas field in the Tarim Basin,Northwest China

In this study, by analyzing CH4 concentration and 613CCH4 in soil-gas profiles, the potentials of CH4 gas transfer from ground to atmosphere were studied at four representative sectors in the Yakela condensed gas field in the Tarim Basin, Xinjiang, China. These are： 1） the oil-gas interface sector, 2） fault sector, 3） oil-water interface sector, 4） an external area. Variation in CH4 in soil-gas profiles showed that CH4 microseepage resulted from the migration of subsurface hydrocarbon from deep-buried reservoirs to the earth＇s surface. It was found that CH4 from deep-buried reservoirs could migrate upwards to the surface through faults, fissures and permeable rocks, during which some CH4 was oxidized and the unoxidized methane remained in the soil or was emitted into the atmosphere. The lowest level of CH4 at the soil-gas profile was found at the CH4 gas-phase equilibrium point at which the CH4 migration upwards from deep-buried reservoirs and the CH4 diffusion downwards from the atmosphere met. The 613CcH4 and ethane, propane in soil gas exhibited thermogenic characteristics, suggesting the occurrence of CH4 microseepage from deep-buried reservoirs. A linear correlation analysis between CH4 concentrations in soil gas and temperature, moisture, pH, Eh, Ec and particle size of soil indicated that both soil Eh and soil temperature could affect CH4 concentration in soil gas while soil pH could indirectly influence soil methanotrophic oxidation via impacting soil Eh.

Measurement and Result of Soil Gas Radon and Soil Gas Mercury in the Exploration of Haihe Hidden Fault

In the exploration of the hidden Haihe fault,radon and mercury in soil gas were measured by using FG-3017 radon detector and XG-4 mercury analyzer.In this paper,based on the measurement results of 12 fault gas profiles,and integrating with the exploration results of artificial seismic prospecting,the relationship between anomalous site of fault gas and fault location is analyzed.Using the relationship between anomalous strength of fault gas and fault activity,the activity of Haihe fault is studied,thus the location and activity segmentation of the Haihe fault in Tianjin region are presented.This study shows that the method of fault gas detection can not only identify the preliminary location of fault,but also make preliminary segmentation of fault activity.The fault detected by the method of fault gas measurement is shown as a band.Through contrasting with exploration results of artificial seismic prospecting and analyzing,we find that the fault is located inside the band.According to the measurements of soil gas radon,the Haihe fault can be divided into east and west segments and the activity of the east segment of Haihe fault is stronger than that of the west segment.This is only a relative result,and it is difficult to judge whether the fault is active or not with this result.

Effects of Biochar Application on Soil Properties, Plant Biomass Production, and Soil Greenhouse Gas Emissions: A Mini-Review

Biochar has been applied extensively as a soil amendment over the past decades. This review summarizes the general findings of the impacts of biochar application on different aspects from soil physical, chemical, and microbial properties, to soil nutrient availabilities, plant growth, biomass production and yield, greenhouse gases (GHG) emissions, and soil carbon sequestration. Due to different biochar pyrolysis conditions, feedstock types, biochar application rates and methods, and potential interactions with other factors such as plant species and soil nutrient conditions, results from those studies are not inclusive. However, most studies reported positive effects of biochar application on soil physical and chemical properties, soil microbial activities, plant biomass and yield, and potential reductions of soil GHG emissions. A framework of biochar impacts is summarized, and possible mechanisms are discussed. Further research of biochar application in agriculture is called to verify the proposed mechanisms involved in biochar-soil-microbial-plant interactions for soil carbon sequestration and crop biomass and yield improvements.

Assessment of the Effects of Temperature, Precipitation and Altitude on Greenhouse Gas Emission from Soils in Lagos Metropolis

Significant pool of carbon is present in the biosphere as soil organic carbon (SOC). More carbon is stored in the soils which include peatlands, wetlands and permafrost than is present in the atmosphere. There are still controversies regarding the effects of climate change on global soil carbon stocks. This study seeks to: assess the effect of altitude, temperature and precipitation on the greenhouse gas emission from soil;and to examine the correlation between soil organic carbon and soil texture. With a total of 81 samples collected at 3 different depths (0 - 10 cm, 10 - 20 cm, 20 - 30 cm) from 27 locations in different regions of Lagos, the relation of soil organic carbon concentration to climate was investigated. Samples taken were analyzed for soil organic matter, soil organic carbon (SOC), and percentage of silt/clay/sand. The amount of carbon dioxide released was calculated. Temperature, precipitation and altitude were also taken into consideration. From the 27 locations topsoil had 8 locations of highest SOC contents;middle soil had 2 locations of highest SOC contents while bottom soil had 17 locations of highest SOC contents. SOC contents of top soil were linked with soil texture, vegetation type, temperature, precipitation, and altitude. The study showed that SOC increased with decrease in temperature, decrease in precipitation, and increase in altitude. Forest, shrubs and grassland types of vegetation, as well as soil depths also favour SOC contents. The study also showed that increase in temperature and altitude favours greenhouse gas emission from the soil. From our findings, SOC and climate change are greatly linked.

Influence of biochar on soil air permeability and greenhouse gas emissions in vegetated soil:A review

The increasing emission of greenhouse gases such as CO_(2),CH_(4),and N_(2)O from the soil has become a growing concern globally.To address this issue,biochar has emerged as an environmentally friendly soil amendment that can affect the gas permeability of soil and reduce greenhouse gas emissions.The biochar-soil-plant system exhibits a complicated interaction that promotes plant productivity and root elongation,further impacting greenhouse gas emissions.The objective of this paper is to provide a comprehensive review of the effects of biochar on soil gas permeability and consequently greenhouse gas emission in vegetated soil.The paper begins by discussing the basic characteristics of biochar and its impact on soil microstructure.It then explores the impact of biochar on the gas permeability of both non-vegetated and vegetated soil.The mechanisms through which biochar influences greenhouse gas emission are explained in terms of modified soil aeration,water holding capacity,adsorption,pH,available nutrients,and the activity of soil microbes and enzymes.The role of plants in greenhouse gas emission in biochar-amended soil is also analysed by comparing the vegetated group with the non-vegetation group.The paper includes a discussion of the various methods used to measure soil gas permeability,such as the steady-state and transient methods,as well as greenhouse gas emission measurement techniques,such as the chamber system and micrometeorological methods.Finally,future research directions are proposed to highlight the impact and corresponding mechanisms of plant roots on the biochar-induced variation of soil gas permeability and greenhouse gas emission.

Numerical model of compressible gas flow in soil pollution control

Based on the theory of fluid dynamics in porous media, a numerical model of gas flow in unsaturated zone is developed with the consideration of gas density change due to variation of air pressure. This model is characterized of its wider range of availability. The accuracy of this numerical model is analyzed through comparison with modeling results by previous model with presumption of little pressure variation and the validity of this numerical model is shown. Thus it provides basis for the designing and management of landfill gas control system or soil vapor extraction system in soil pollution control.

GC/MS: A Valid Tool for Soil Gas Hydrocarbons Speciation

This work describes an alternative method based on GC/MS technique with SCAN-ion approach for speciation of hydrocarbons contained in soil gas matrices and sampled on solid sorbent tubes (coconut shell charcoal).

Effect of Gas Flaring on Soil and Cassava Productivity in Ebedei, Ukwuani Local Government Area, Delta State, Nigeria

The threat to human, fauna and flora life posed by pollution due to gas flaring cannot be over-emphasized. Gas flared often resulted in some environmental degradation, one of such influence is soil pollution and poor crop yield. This study examined the effect of gas flaring on soil and cassava productivity in Ebedei, Ukwuani LGA, Delta State. For the purpose of data collection, five (5) experimental sites were systematically selected around the flare site in Ebedei and a control site at Obiaruku. Soil samples were collected at surface 0 - 10 cm and 10 - 20 cm at distance of 50 m, 100 m, 150 m, 200 m and 250 m apart respectively away from the bund wall of the flare. The data generated were analysed using multiple regression and paired t-test analyses. The study revealed that the soils found in Ebedei have high composition of sand and soil temperature and are acidic. The soil electrical conductivity, Phosphorous, Nitrogen, Potassium and Sodium were very low. More so, the yield of cassava increases with a corresponding increase in distances from flare site. The first hypothesis revealed that there is significant variation in soil nutrients as distance increases from gas flare sites. This is evident from F value of 234.99 which is greater than the critical table value of 4.39. Furthermore, as flare distance increases, so also the organic carbon, electrical conductivity and Nitrogen increase. The second hypothesis revealed that there is a significant difference in cassava yield at gas-flared area and the non-flared area which is evident at t (6.032) is greater than the critical table (1.895) at P 0.05. It is therefore recommended that Government and FEPA should enact environmental Policies and revisit and review existing environmental and oil drilling laws in Nigeria with a view of updating them to international and environmental friendly standards.

Pesticides Recovery and Detection from Agricultural Soil Leachates Using Gas Chromatography Masses with Electron Capture Detector

In this study, it is reported an analytical approach to recover organochlorine pesticides from a clay soil. Soil was physical and chemically characterized. Also pesticides extraction was carried out using packed columns and various aqueous media (H2O-milliQ, NaOH, HCl, SDS, Triton X-114, Humic acids and Acetonitrile). The leachate samples were analyzed on an Agilent Technologies 6890N Gas Chromatograph with electron capture in a# AB002 Column 30.0 m × 250 μm × 0.25 μm calibrated, 25 psi pressure, flow 2.9 ml/min, temperature 25°C, ultra-high purity Helium as the entrainment gas and an elution time of 50 min. The results show that the highest extraction percentage of pollutants in the soil washing was obtained with acetonitrile recovering: p, p’-DDT (91.0%);p, p’-DDE (92.0%);p, p’-DDD (96.0%);aldrin (98.6%);dieldrin (98.0%). With Triton X-114, the extractions recovery was: p, p’-DDT (63.0%);p, p’-DDE (64.0%);p, p’-DDD (65.0%);aldrin (67.0%);dieldrin (72.0%). This study illustrates the potential Applicability of SPME for routine analysis of organochlorine pesticides in soils.

Effects of Nitrogen Application Rate to Late Rice on Greenhouse Gas Emissions and Soil Carbon Pool During the Growing Season of Winter Chinese Milk vetch

It is of important referential values for the further understanding of the effects of fertilization on greenhouse gas emissions and the effects of winter green manure on soil carbon pool to study the effects of fertilization on the greenhouse gas emissions and soil carbon pool during the growing season of winter Chinese milk vetch in the process of rice cultivation.This study investigated the effects of nitrogen application in late rice season on the yield of the succeeding Chinese milk vetch and greenhouse gas emissions as well as the soil carbon pool characteristics after the winter planting of Chinese milk vetch with the winter idling of no nitrogen application as the control.The results showed that the yield of Chinese milk vetch was the highest under the nitrogen application of 225 kg/hm^2 in the late rice season,reaching up to 18 388.97 kg/hm^2,which was significantly different from other treatments( P <0.05).Nitrogen application in late rice season increased the emissions of N_2 O,CH_4,CO_2 and global warming potential( GWP) in the growing season of Chinese milk vetch.Compared with the winter idling treatment,winter planting of Chinese milk vetch significantly increased the soil organic carbon and soil carbon pool management index.The yield of Chinese milk vetch was significantly positively correlated with N_2O and CH_4 emissions( P < 0.05),while it presented extremely significant positive correlations with CO_2 emissions,GWP,active organic carbon,and carbon pool management index( P < 0.01).Nitrogen application in the late rice season increased the emissions of N_2 O,CH_4,CO_2,and enhanced the greenhouse gas emission potential during the growing season of Chinese milk vetch.Therefore,without reducing the yield of rice,reducing the amount of nitrogen fertilizer in rice could reduce the greenhouse gas emissions in the growing season of succeeding Chinese milk vetch.

Control Measures of Soil Erosion in a Typical Construction Project Area ( Dina 2 Gas Field)

To treat the relationship between project construction and ecological environment and effectively prevent new soil erosion during the construction, according to the project layout, soil erosion distribution as well as natural and socio-economic conditions, the control measures of newly increased soil erosion along the project were carried out based on site survey and analysis of relevant information. In addition, adhering to the prin- ciple of partition prevention and treatment, some guiding prevention and control measures of the natural zone passed by the project and soil erosion control district were determined, which provided scientific references and technical support for the rational layout of water and soil conservation and ecological restoration measures in Dina 2 gas field.

The Degradation and Pollution of Soils on the Territory of the Kovykta Gas Condensate Field

In this paper, research results from the time interval 2002-2012 are used to give an account of the chemical composition of soils on the territory of the Kovykta gas condensate field. The findings presented provide a better understanding of the ecological state of soil cover, its resilience to anthropogenic impacts, and its possible disturbance caused by the drilling pad construction activity, and by the laying of geophysical profiles. An analysis of soil pollution for the study territory generally showed that the soils are polluted with chemical elements which refer to toxicity classes： Pb, Cu, Ni, Cr, Ba and Mn. High levels ofoil products were detected near boreholes. Strong mineralization was recorded in the soil near borehole. It has a chloride-sodium chemical composition. As a result of the construction of foundation pits, recesses, ditches and earth embankments, the soil is totally destroyed, and rock outcrops show up. Disturbances of the sod cover due to road construction or even by all-terrain vehicles in these extreme conditions entail an accelerated development of linear erosion to form scours and gullies. Elimination of the canopy layer leads to an increase in surface heating, and to an acceleration of permafrost thawing. Swamping is accelerated on negative relief forms due to the increased entry of melt waters.

Study on the Monitoring Malfunction of Water Pollution during Drought or Flood Period and Low-carbon and High-value Methodology--A Case Study of the Correlation Test of Water,Soil and Gas Pollution in Xiangxiang County

Based on the low-carbon and high-value methodology of chemical ecology and chemical informatics,combining theory and methods,taking saving,environmental protection,low carbon,high production,high value and circulation as values and aims,the relationship between human and land as a basis,ecosystem as a center,overall control as a goal and agricultural ecological engineering as a mean,environmental pollution detection,as one of bottlenecks for agricultural products and food security,should be solved firstly;through the field survey in dry years from 2009 to 2010 when drought and flood were frequent and the frequency of drought was higher than that of flood,plus the determination of surface water flow and water quantity in a small typical river basin,the correlation of local water,soil and gas in the county could be found,and the transfer of monitoring focus from water environment to atmospheric environment was possible and necessary.The study would promote the quantitative research on the correlation among water,soil and gas,and the results were in accordance with the conclusions of related studies.

Numerical study on the deformation of soil stratum and vertical wells with gas hydrate dissociation

Gas hydrate（GH） dissociates owing to thermal injection or pressure reduction from the well in gas/oil or GH exploitation. GH dissociation leads to, for example, decreases in soil strength, engineering failures such as wellbore instabilities, and marine landslides. The FLAC3 D software was used to analyze the deformation of the soil stratum and vertical wells with GH dissociation. The effects of Young＇s modulus, internal friction angle, cohesion of the GH layer after dissociation, and the thickness of the GH layer on the deformation of soils were studied. It is shown that the maximum displacement in the whole soil stratum occurs at the interface between the GH layer and the overlayer. The deformation of the soil stratum and wells increases with decreases in the modulus, internal friction angle, and cohesion after GH dissociation. The increase in thickness of the GH layer enlarges the deformation of the soil stratum and wells with GH dissociation. The hydrostatic pressure increases the settlement of the soil stratum, while constraining horizontal displacement. The interaction between two wells becomes significant when the affected zone around each well exceeds half the length of the GH dissociation zone.