Estimation of soil organic carbon reservoir in China

The paper respectively adopted physio-chemical properties of every soil stratum from 2473 soil profiles of the second national soil survey. The corresponding carbon content of soils is estimated by utilizing conversion coefficient 0.58. In the second soil survey, the total amount of soil organic carbon is about 924.18xl08t and carbon density is about 10.53 kgC/m2 in China according to the area of 877.63x106hm2 surveyed throughout the country. The spatial distribution characteristics of soil organic carbon in China is that the carbon storage increases when latitude increases in eastern China and the carbon storage decreases when longitude reduces in northern China. A transitional zone with great variation in carbon storage exists. Moreover, there is an increasing tendency of carbon density with decrease of latitude in western China. Soil circle is of great significance to global change, but with substantial difference in soil spatial distribution throughout the country. Because the structure of soil is inhomogeneous, it could bring some mistakes in estimating soil carbon reservoirs. It is necessary to farther resolve soil respiration and organic matter conversion and other questions by developing uniform and normal methods of measurement and sampling.

Functional Rehabilitation of the "Soil Reservoir"in Degraded Soils to Control Floods in the Yangtze River Watershed

The reasons for the Yangtze River flood calamity in 1998 are briefly introduced. The authors believe that using a 'soil reservoir' concept is an important means to help control flooding of the Yangtze River.A 'soil reservoir' has a large potential storage capacity and its water can be rapidly 'discharged' into the underground water in a timely fashion. The eroded, infertile soils of the Yangtze River Watershed are currently an obstacle to efficient operation of the 'soil reservoir'. The storage capacity of this 'soil reservoir'has been severely hampered due to intensive soil erosion and the formation of soil crusts. Therefore, possible measures to control floods in the Yangtze River Watershed include: rehabilitating the vegetation to preserve soil and water on the eroded infertile soils, enhancing infiltration of the different soil types, and utilizing the large 'soil reservoir' of the upper reaches of the Yangtze River.

Dynamic Monitoring of Soil Erosion for Upper Stream of Miyun Reservoir in the Last 30 Years

The Revised Universal Soil Loss Equation(RUSLE) was applied to assess the spatial distribution and dynamic properties of soil loss with geographic information system(GIS) and remote sensing(RS) technologies.To improve the accuracy of soil-erosion estimates,a new C-factor estimation model was developed based on land cover and time series normalized difference vegetation index(NDVI) datasets.The new C-factor was then applied in the RUSLE to integrate rainfall,soil,vegetation,and topography data of different periods,and thus monitor the distribution of soil erosion patterns and their dynamics during a 30-year period of the upstream watershed of Miyun Reservoir(UWMR),China.The results showed that the new C-factor estimation method,which considers land cover status and dynamics,and explicitly incorporates within-land cover variability,was more rational,quantitative,and reliable.An average annual soil loss in UWMR of 25.68,21.04,and 16.80 t ha-1a-1was estimated for 1990,2000 and 2010,respectively,corroborated by comparing spatial and temporal variation in sediment yield.Between 2000 and 2010,a 1.38% average annual increase was observed in the area of lands that lost less than 5 t ha-1a-1,while during 1990-2000 such lands only increased on average by 0.46%.Areas that classified as severe,very severe and extremely severe accounted for 5.68% of the total UWMR in 2010,and primarily occurred in dry areas or grasslands of sloping fields.The reason for the change in rate of soil loss is explained by an increased appreciation of soil conservation by developers and planners.Moreover,we recommend that UWMR watershed adopt further conservation measures such as terraced plowing of dry land,afforestation,or grassland enclosures as part of a concerted effort to reduce on-going soil erosion.

Estimation of soil reinforcement by the roots of four postdam prevailing grass species in the riparian zone of Three Gorges Reservoir, China

Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density(RLD) and root area ratio(RAR) were measured by using the Win RHIZO image analysis system. Root tensile strength(TR) was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu's perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers(>10 cm). RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides(62.26MPa) followed by C. dactylon(51.49 MPa), H.compressa(50.66 MPa), and H. altissima(48.81MPa). Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa(21.1 k Pa), P.paspaloides(19.5 k Pa), and C. dactylon(15.4 k Pa) at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.

The Influencing Factors of Soil Organic Carbon Density in Lanlingxi Watershed in Three Gorges Reservoir Area

To reveal the influencing factors of soil organic carbon( SOC) density in 0-30 cm soil layer of Lanlingxi watershed in Three Gorges Reservoir Area,build the regression equation for soil organic carbon density and adjust carbon sink strategy in this region,soil samples of top soil profile( 0-30 cm) in five land use types were selected by the typical method. The SOC density of top soil profile( 0-30 cm) and other environmental factors,such as elevation,slope and aspect and soil properties in five land use types,including grassland,scrubland,woodland,land for tea plantation and farmland in the watershed was investigated. The relationship of SOC density with physical properties of soil was also examined. The SOC density of the above five land use types averaged 7. 55,3. 83,6. 04,10. 24,2. 83 kg·m^(-2),respectively. There was a significant difference in the SOC density( p < 0. 01); SOC density was significantly positively correlated with organic matter content( R= 0. 942,p < 0. 01),clay mass percentage( R = 0. 898,p < 0. 01),total nitrogen( R = 0. 863,p < 0. 01),elevation( R = 0. 599,p < 0. 01); SOC density was significantly negatively correlated with sand content( R =-0. 932,p < 0. 01) and slope( R =-0. 407,p < 0. 05); and the correlation between SOC density and soil p H,total phosphorus or total potassium was not obvious. Multiple correlation coefficient R = 0. 986( R > 0. 8,highly correlated) between SOC density and environmental factors was greater than the correlation coefficient between any one independent variable and dependent variable,which fully proved the combined effect of environmental factors on SOC density.

A Study of Soil Nutrients in the Terrace Field Changed from Mountain Slope in Three Gorges Reservoir Region

In order to accurately grasp the soil fertility in Three Gorges Reservoir Region after changing mountain slope into terrace field,we take Wushan County for example,and use the spatio-temporal substitution method to analyze the soil nutrient status and trend about the terrace field changed from mountain slope under different length of implementation.The results show that the soil fertility is generally low in the study area,and according to the soil nutrient grading standards in the second national land survey,the average content of total nitrogen,available potassium,organic matter and available phosphorus reaches Standard III,Standard III,Standard IV and Standard V,respectively,and the spatial heterogeneity of soil nutrients is small.Compared to the sloping land,the terrace field changed from mountain slope has increasing soil nutrients on the whole with the length of farming.The mean of various indicators about soil nutrients in the terrace field changed from mountain slope for 2 years is lower than in the sloping land,and there is the biggest difference in soil fertility,while the mean of various indicators about soil nutrients in the terrace field changed from mountain slope for 14 years shows a linear upward trend,and the difference in soil fertility decreases.

Soil Geochemistry Changes Induced by a Foreign Soil Reconstruction Project in Three Gorges Reservoir Region of China

Fertile topsoil was added onto the surface of barren slope land in Three Gorges Reservoir region of China in an anthropogenic process known as the foreign soil reconstruction project. The main goal of this paper was to reveal the influence of anthropogenic activities on pedogenic processes and soil classifications. Chemical weathering indices and comparative analysis were applied to discuss changes in geochemical compositions and weathering features of purplish soils(Cambisols) before and after the project. Results showed that:(1) The foreign soil reconstruction project slightly altered the major element composition of topsoil and improved the soil structure. Although the distributions of major elements in the original topsoil, original subsoil, foreign topsoil and newly constructed topsoil were all similar to that in upper continental crust, newly constructed topsoil was the most similar soil.(2) The chemical index of alteration was more sensitive than the weathering index of Parker at indicating chemical weathering status of purplish soil. The chemical weathering status of newly constructed topsoil was higher than that of the original topsoil and lower than that of foreign topsoil.(3) Anthropogenic activities may provide a promising new thought for the anthropogenic soil classification system. The scope and subgroups of Anthrosols should be extended and strengthened. Or there may be a need to combine Anthrosols and Technosols orders to create a new soil order. The results may be used for optimizing soil mellowing engineering activities and enriching the soil classification system.

Using ^(137)Cs Tracing Methods to Estimate Soil Redistribution Rates and to Construct a Sediment Budget for a Small Agricultural Catchment in the Three Gorges Reservoir Region,China

Soil erosion and associated off-site sedimentation are threatening the sustainable use of the Three Gorges Dam.To initiate management intervention to reduce sediment yields,there is an increasing need for reliable information on soil erosion in the Three Gorges Reservoir Region(TGRR).The purpose of this study is to use 137 Cs tracing methods to construct a sediment budget for a small agricultural catchment in the TGRR.Cores were taken from a pond and from paddy fields,for 137 Cs measurements.The results show that the average sedimentation rate in the pond since 1963 is 1.50 g cm-2 yr-1 and the corresponding amount of sediment deposited is 1,553 t.The surface erosion rate for the sloping cultivated lands and the sedimentation rate in the paddy fields were estimated to be 3,770 t km-2 yr-1 and 2,600 t km-2 yr-1,respectively.Based on the estimated erosion and deposition rates,and the area of each unit,the post 1970 sediment budget for the catchment has been constructed.A sediment delivery ratio of 0.5 has been estimated for the past 42 years.The data indicate that the sloping cultivated lands are the primary sediment source areas,and that the paddy fields are deposition zones.The typical land use pattern(with the upper parts characterized by sloping cultivated land and the lower parts by paddy fields) plays an important role in reducing sediment yield from agricultural catchments in the TGRR.A 137 Cs profile for the sediment deposited in a pond is shown to provide an effective means of estimating the land surface erosion rate in the upstream catchment.

The Characteristics of Soil Nutrients in Terracing Land under Different Land Use Patterns in Three Gorges Reservoir Area

In this study,taking the typical terracing land in Wushan County of Chongqing Municipality for example,we study the distribution of soil nutrients in the terracing land under different land use patterns in Three Gorges Reservoir Area. We conduct field survey and sampling on three different land use patterns( cash crop land,food crop land and abandoned land),and do the indoor experimental analysis of soil nutrient indicators. The results indicate that there is significant or very significant impact on soil nutrients under different land use patterns. The content of soil organic matter declines in sequence from abandoned land,food crop land to cash crop land; the content of soil N declines in sequence from cash crop land,abandoned land to food crop land; the content of soil P declines in sequence from cash crop land,food crop land to abandoned land; the content of soil K declines in sequence from abandoned land,cash crop land to food crop land. The result is in close relation to land use patterns,human cultivation activity,land disturbance and application of fertilizer.

高效液相色谱-质谱法测定油藏地层水和土壤中甜菜碱型表面活性剂的样品处理

比较了测定油藏地层水和土壤这类复杂基质中3种甜菜碱型表面活性剂的样品净化方法。选用直接过微孔滤膜、活性炭固相萃取柱、碱性氧化铝固相萃取柱、HLB固相萃取柱、MCX固相萃取柱、WCX固相萃取柱,对10、50、100 mg/L质量浓度下的回收率对比分析,并结合高效液相色谱-质谱联用全扫描质谱图甄选较优净化手段。分析结果显示,采用混合型强阳离子交换柱(MCX固相萃取柱)进行净化提取后,用高效液相色谱-质谱联用法进行检测,3种甜菜碱型表面活性剂在质量浓度10~50 mg/L内与色谱峰面积线性良好,相关系数均达到0.99以上,检出限为0.01 mg/L。加标回收率为96.9%~100.5%,相对标准偏差为0.7%~2.1%(n=7)。该方法操作简单,特异性强,作为复杂基质中甜菜碱型表面活性剂净化最佳方法,为甜菜碱型表面活性剂的检测提供坚实的基础。

紫色土坡耕地耕层持水抗旱性能及生产力对侵蚀程度的响应

【目的】分析侵蚀条件下紫色土坡耕地耕层持水性能与产量响应特征,为调控坡耕地季节性干旱及水分利用效率、提升侵蚀条件下坡耕地玉米产量提供理论依据。【方法】采用铲土侵蚀模拟法,以未侵蚀地块为对照组(S_(-0)),对比分析5 cm(S_(-5))、10 cm(S_(-10))、15 cm(S_(-15))、20 cm(S_(-20))侵蚀程度和3种管理措施下(不施肥(CK)、施化肥(F)、生物炭+化肥(BF)),坡耕地耕层持水抗旱性能和玉米产量的年际变化特征及对侵蚀程度的响应。【结果】(1)坡耕地心土层土壤持水性能更强。在相同水平土壤水吸力下,耕作层土壤容积含水量降低幅度(13.9%—18.2%)较心土层更大(9.8%);随年际变化,土壤容积含水量在S_(-5)时增幅最大为耕作层(14.2%),而心土层表现为在S_(-15)最大(33.2%)。(2)坡耕地土壤总库容、兴利库容、最大有效库容及有效水分含量,随侵蚀加剧呈开口朝下的抛物线变化规律。随年际变化,各侵蚀程度下土壤最大有效库容最大增幅(44.7%)处于较强烈侵蚀程度(S_(-15)),而有效水分含量、最大储水量及单次接纳最大降雨量在微弱侵蚀程度下(S_(-0)至S_(-10))提升幅度最大。(3)坡耕地玉米产量随侵蚀加剧总体呈降低趋势,且与土壤最大有效库容、田间持水量有正相关关系;随年际变化,各侵蚀程度下坡耕地减产效果降低,且产量变化随侵蚀加剧呈一定滞后性,即侵蚀发生年产量无明显减产。(4)侵蚀条件下坡耕地土壤最大有效库容主要受土壤质地中黏粒含量、毛管孔隙度和有机质含量显著影响(P<0.01);而田间持水量与土层深度、有机质、粉粒及孔隙度呈极显著关系(P<0.01)。【结论】土壤持水抗旱性能的强弱主要受土壤结构优劣的影响。对坡耕地侵蚀耕层辅以深翻耕作和生物炭+化肥管理措施改善土壤结构,可有效调控坡耕地侵蚀性耕层持水抗旱性能,提升侵蚀条件下坡耕地作物产量。

以确保“一泓清水永续北上” 引领南水北调中线水源区水土保持高质量发展

丹江口库区及上游是南水北调中线水源区(以下简称“水源区”),其水土保持高质量发展是保障“一泓清水永续北上”的重要支撑。文章针对水源区水土流失现状和特点,总结了丹江口库区及上游水土保持重点防治工程(以下简称“丹治”工程)实施以来的水土保持成效,分析了水土保持面临的新形势和新要求,梳理了水土保持存在的短板和不足,研究提出了引领丹江口库区及上游水土保持高质量发展的对策举措,为各级政府加强南水北调中线水源区水土保持治理管理提供参考。

基于Swin Transformer目标全景分割的三峡库首土质滑坡识别

【目的】滑坡识别是解决山区地质灾害隐患在哪里的关键。尤其人工智能是深度学习方法开始被广泛应用于目标识别领域,但对于多植被山区复杂环境下的滑坡隐患识别,存在着模型单一、精度较差等问题。【方法】故文章提出一种基于Swin Transformer(Shift Windows Transformer)作为骨干网络结合目标全景分割的智能识别方法,对三峡库首区域土质滑坡开展识别。将三峡库首的485处土质滑坡制作成样本集,并分为训练集和测试集。将训练集加载进Swin Transformer模型中进行训练,模型采用自注意力机制对训练集提取特征,构建特征图,测试集验证特征图的识别精度,保留识别精度最高的特征图。最终以此实现滑坡目标与背景区域的有效区分进而完成隐患识别,同时与DeepLab V3模型进行对比。【结果】结果显示:Swin Transformer模型在识别精度和识别速度上都要高于DeepLab V3模型,在三峡库首的试验中准确率可以达到83.55%,单张图片预测时间为0.18 s。【结论】结果表明:该方法能够在多植被山区复杂环境下快速识别土质滑坡,可为多植被山区的滑坡灾害调查提供参考。

深海能源土含气储层边坡稳定性研究

深海能源土开采不当往往会造成含水合物储层的强度劣化,诱发海床失稳问题。为探究深海能源土开采对含气储层边坡稳定性的影响,以深海能源土采挖回填装置的开采工况为实际工程背景,针对3种工况下能源土采挖回填诱发的海底滑坡现象,基于有限元强度折减法建立数值模型,分析不同黏土含量、含气量及回填加固等因素引起的水合物含气储层稳定性问题,得到相应安全系数。研究结果表明:黏土含量越高,海底沉积物边坡的安全系数越低,边坡稳定性越差;含气量对深海能源土含气储层的边坡稳定性呈非线性影响,安全系数随含气量的增加呈先上升后下降的趋势;采用胶结性材料进行回填加固处理可提高海底边坡安全系数,边坡稳定性增强。

降雨和库水位升降条件下考虑非饱和渗透系数空间变异的边坡可靠度分析

降雨和水位升降对库岸边坡具有显著影响,传统确定性分析难以准确评估其稳定性。考虑降雨和水位升降联合作用下水力参数的空间变异性,进行非饱和土边坡可靠度分析具有重要意义。以赣江库区中的莒洲岛边坡为研究对象,以贝叶斯方法校准的多元水力参数的联合随机场为基础,建立非饱和土边坡的稳定性分析方法。根据有限的岩土力学室内试验数据,采用贝叶斯方法校准土水特征曲线的模型参数,并从VGM、VGB、VG和FX模型中选出最优模型;联合多元水力参数的随机统计特征,生成非饱和土边坡渗透系数的随机场空间分布;针对2021年5月赣江水位快速升降并伴随暴雨的工程背景,将上述方法应用于莒洲岛库岸边坡的稳定性分析。研究结果表明,暴雨与水位变化的联合作用对边坡安全系数的影响显著,确定性分析的边坡安全系数偏低,考虑非饱和渗透系数空间变异性后计算所得到的SWCC综合可靠指标不能满足规范要求,需采取额外的边坡工程加固措施以保证边坡的长期稳定性。

高新沙水库土壤重金属形态分布、浸出特征及其对水质安全影响

为了研究高新沙水库土壤重金属对水质安全风险的影响,本文通过8个采样区域3 m深处土壤重金属含量与形态的测定,采用地累积指数和生态风险指数法阐明重金属潜在生态风险,并通过浸提模拟试验来探究重金属浸出特性及对水质安全影响.结果表明,8种重金属Cu、Zn、Cd、Pb、Ni、Cr、Hg和As含量范围分别为11—42.5、70.75—119.5、0.01—0.16、24.5—100、20.25—35、89—177、0.05—0.17、10.15—22.1 mg·kg^(-1),在8处区域普遍未超出农田土壤环境标准风险筛选值(GB 15618-2018),仅有1处As含量为22.10 mg·kg^(-1),超出筛选值20 mg·kg^(-1).重金属主要以残渣态为主,其中Zn、Ni、Cr、Hg和As等5种重金属残渣态所占比例均达到70%以上,总体潜在生态风险处于轻微水平.在不同pH浸提液模拟作用下(pH=6.34、5.6和3.6),绝大部分重金属浸出浓度未超出生活饮用水卫生标准限值(GB 5749-2022),但浸提液pH=1.0极端情况下,Cu、Zn、Cd、Pb、Ni和As出现了不同程度的超标现象.在实际水体作用下,整体上库底土工膜破损程度对水质未产生不良影响,除了1处土壤点位中Ni出现轻微超标现象.综合以上结果,水库土壤重金属污染风险处于较安全水平,对水质造成的环境风险非常有限,但在水库实际运行中加强重金属含量的监测与管理,尤其是Pb和Ni.

三峡水库消落带土壤反硝化及DOM的影响

在重庆主城与涪陵选取了3个典型点位采集土壤样品,并对土壤的理化性质、原位反硝化速率、溶解性有机质(DOM)驱动的反硝化以及库区土壤的微生物进行了考察与分析.结果显示在海拔145~155m区间,淹水期镇安镇、涪陵区和鱼嘴镇最高氨氮(NH_(4)^(+)-N)平均浓度分别为31.32,28.63和19.23mg/kg,均高于落干期.在淹水期,与高海拔区域土壤中硝酸盐氮(NO_(3)^(-)-N)平均浓度相比,低海拔土壤中NO_(3)^(-)-N平均浓度分别增大了46.91%(镇安镇)、37.89%(涪陵区)和29.69%(鱼嘴镇).在淹水期,土壤有机质(SOM)平均浓度随着海拔高程的降低而降低,镇安镇、涪陵区和鱼嘴镇分别从109.16,80.93和82.61mg/kg降至65.63,64.53,53.41mg/kg.土壤中NH_(4)^(+)-N和NO_(3)^(-)-N的含量与现场反硝化速率呈显著正相关(P<0.05),在提供充足的碳(C)和氮(N)营养元素后,土壤潜在反硝化速率表现出较大的时间和空间差异性.在由DOM驱动的反硝化实验中,DOM降解符合一级动力学模型(R^(2)>0.93),N2O累积量符合Logistic模型(R^(2)>0.97).在三峡水库消落带土壤中,反硝化功能微生物主要是Bacillus和Comamonadaceae,其丰度变化与土壤潜在反硝化速率呈现显著的正相关性(P<0.05).

峡山水库流域表层土壤氮磷淋溶特征及释放预测

以峡山水库流域表层土壤为研究对象,采用室内土柱淋溶法模拟不同淋溶量下总氮(TN)、总磷(TP)、氨氮(NH_(3)-N)的淋出情况,并预测氮磷释放量。结果表明,在不同土地利用方式下,该区域的TN、TP、NH_(3)-N含量总体上来说耕地大于林地,但并不存在显著差异。TN、TP、NH_(3)-N淋溶浓度与其在土壤中总量均呈现显著正相关。淋溶液中TN浓度随淋溶量的增加而逐渐降低,这表明土壤对TN的吸附能力较差,易随降雨渗透发生损失;TP和NH_(3)-N浓度随淋溶量的增加无明显变化规律,且其淋溶强度均小于TN。在一定淋溶量条件下,氮磷淋出浓度与淋溶液体积呈指数相关,氮磷淋溶浓度随淋溶量的增加经过拟合得到峡山水库流域表层土壤营养盐的淋溶函数C=C_(0)e^(KV)。通过确定性数学模型模拟计算出采样点TN、TP、NH_(3)-N的年均释放浓度均值分别为23.00、4.33、4.49 mg/L,其中TN和TP年均释放浓度综合营养状态指数均超过水体重度富营养化标准,很可能通过径流等过程导致水体中氮磷富集。

大洋河水库除险加固工程水保措施及水土流失预测

以大洋河水库除险加固工程为例,介绍了工程施工期间水土流失防治措施,并进行水土流失防治效果预测。结果表明,通过采取水土流失防治措施,可以有效地控制水土流失,维护并增强区域水土保持功能,并有利于项目区域生态环境的恢复。