Oasis Farmland Research Articles

Impact of textural layers in soils on irrigation infiltration processes in an oasis farmland, northwestern China

AbstractThe Hexi Corridor Oasis in China is an important agricultural area supported by extensive irrigation. The sandy soil in the area exhibits textural layering, which has marked effects on its properties. Textural layered soils play an important role in distributing and regulating water regimes in irrigated fields. However, little is known about the textural layering‐dependent variability in soil water infiltration characteristics following irrigation and the potential effects on soil hydrology and water regimes in these soils. The objective of this study was to determine water infiltration processes and their influencing factors for six soil profile types in an oasis farmland. Six in situ constant‐head infiltration measurements (with three replications in each of six sites) were conducted with a single‐ring infiltrometer in different soil texture configurations, and Hydrus‐2D model was applied to evaluate soil water distribution. The results showed that the wetting front depth for all treatments was in the following order: ST‐1 > ST‐5 > ST‐6 > ST‐3 > ST‐2 > ST‐4; the stable infiltration rate ranged from 1.2 to 3.3 cm/min during the investigation period in all treatments. The presence of a finer‐textured soil layer decreased water infiltration rates through the profiles, and the thickness and burial depth of textured layers had obvious effects on infiltration, compared with homogeneous sand profiles. Presence of a medium‐textured layer affected the infiltration characteristics and soil water spatial variability; driven by increased field capacity and the wilting point, hydraulic conductivity was correlated with soil variables that were related to soil structure, such as wilting point and field capacity, and less so with variables that were related to soil texture, such as the clay fractions (p < 0.001). These results suggested that textural layering altered the soil structure and caused heterogeneous infiltration of water, with implications for the distribution of irrigation water and prevention of deep percolation in this oasis farmland. The result of this study offers a new analysis of ponded single‐ring water infiltrometer data that the soil water infiltration is also influenced by the type of textural layered than just the irrigation system, which supports crop irrigation management in study area and other regions with similar soil regimes.

Long-term effects of conventional cultivation on soil cation exchange capacity and base saturation in an arid desert region

Land reclamation and subsequent management affect soil condition, which is critical for sustainable agricultural production. Soil cation exchange capacity (CEC) and base saturation (BS%) play an important role in the assessment of soil fertility and buffering capacity. However, the variation of these indicators in the evolution of oasis farmland in arid desert areas remains unclear. Therefore, this study was carried out aiming to evaluate the effect of desert reclamation and following long-term conventional cultivation on the CEC and BS%. For the study, we investigated the CEC and exchangeable bases (ExBas) content in oasis farmlands along a chronosequence (0–100 years) of cultivation in arid region and identified the key factors affecting CEC and BS%. The results showed that soil CEC and ExBas significantly increased after desert reclamation, whereas the BS% dramatically decreased. However, all these changes were alleviated with the conventional cultivation age. Regression analysis showed that soil CEC, ExBas, and BS% all exponentially changed with cultivation years. Based on our findings, CEC and ExBas were closely related to soil particle size composition, total nitrogen (TN), soil organic matter (SOM) and soil water content (SWC). The multiple stepwise regression further indicated that the changes in CEC and ExBas after reclamation mainly depended on the silt content, SWC, SOM, and TN. Our findings highlight that although desert reclamation increases soil CEC and ExBas in arid area, this effect tends to disappear after about 100 years of conventional cultivation, and meanwhile, the decline in BS% due to increased acids should also be noted.

Maize Straw and Nitrogen Fertilizer Alter Soil Carbon and Nitrogen Mineralization during the Fallow Period in the Oasis Farmland area

Maize Straw and Nitrogen Fertilizer Alter Soil Carbon and Nitrogen Mineralization during the Fallow Period in the Oasis Farmland area

Numerical simulation of shelter effect assessment for single-row windbreaks on the periphery of oasis farmland

Dust storms, resulting from aeolian erosion, pose significant environmental hazards, while farmland is one of the main sources of dust storm release. An effective strategy to mitigate surface wind speed and curb dust emissions involves the establishment of windbreaks on the periphery of oasis farmland. This study conducts a series of numerical simulations using computational fluid dynamics (CFD) to explore the airflow fields around windbreaks with diverse systematic structural parameters, encompassing porosity, planting spacing, and fence effects. The main findings are as follows: (1) When the vegetation porosity is consistent (e.g., porosity α = 0.7, 0.8, and 0.9), exact geometry results can effectively reflect the distribution of wall shear stress, while the porous medium model overlooks these details. (2) The “Venturi effect” contributes to the acceleration of surface erosion and improper planting spacing results in an elevation of near-surface velocity. Planting spacing of 0.5 m demonstrates superior wind speed reduction performance, mitigating aeolian erosion and accumulation. (3) When the fence is positioned at l = 5h (h represents the height of the windbreaks), the flow field around the windbreaks is minimally influenced. The optimal placement distance for fences should be close to the windbreaks, featuring minimal porosity (l = 0 h, α = 0.1), extending the shelter distance from 3 to 4 h to 5–6 h. The research results can provide a theoretical basis for optimizing the plant configuration of biological desertification control and soil erosion control measures.

Long-term conventional cultivation after desert reclamation is not conducive to the improvement of soil carbon pool and nutrient stocks, a case study from northwest China

Reclamation in desert-oasis areas is effective for improving land productivity and ensuring food supply. However, the understanding of the sustainable productivity of soils under long-term conventional cultivation after desert reclamation is still poor. This study was conducted to determine soil structural properties, organic carbon stocks (SOCS) and nutrient stocks under four desert reclamation ages (0, 30, 60, and 100) in the arid region of northwest China, and evaluate the influence of long-term conventional cultivation on desert soil quality. The results indicated that soil structural stability index (SI) in topsoil improved after desert reclamation, but showed a slight downward trend after 60 years of cultivation, and farmland soil in the study area was still at serious risk of degradation (SI ≤ 5 %) overall. SOCS were enlarged by 4.2 times after desert reclamation, and nitrogen stocks (NS) and phosphorus stocks (PS) were increased by 1.2–6.5 times. However, the regression analysis showed that SOCS and NS in 0–40 cm soil layer and PS in topsoil stopped increasing after about 60-year conventional cultivation. Soil stoichiometry, pH and texture were the key factors affecting SOCS, NS and PS in oasis farmlands. In summary, our study emphasized that soil quality in arid areas was greatly improved after desert reclamation, however, long-term conventional agriculture management measures limited this improvement. Therefore, long-term conventional management of agricultural land in arid areas should introduce appropriate conservation measures to achieve sustainable soil productivity.

Continuous straw returning enhances the carbon sequestration potential of soil aggregates by altering the quality and stability of organic carbon

Soil structure plays an important role in organic carbon (OC) sequestration, thereby influencing soil fertility and changes in global climate. However, aggregate OC chemical structure changes due to long-term return of straw in oasis farmland of arid northwest China remains unclear. This study conducted 0-, 5-, 10-, 15-, and 20-year straw returning experiments during which three soil components where measured: (1) the functional carbon (C) pool and macroaggregates; (2) microaggregates and silt + clay; (3) the chemical structure of soil OC (SOC). The results demonstrated that in comparison with the control, straw return increased SOC, particulate OC (POC), and mineral-associated OC (MAOC) by 21.90%–63.51%, 5.00%–31.00%, and 46.00%–226.00%, respectively. With increasing duration of straw return, microaggregates transitioned to macroaggregates, and percentages of soil macroaggregates under 10-year straw return increased by 20.26%, 3.39%, 4.40%, and 11.12% compared with that under 0-, 5-, 15- and 20-year straw return, respectively. Soil geometric mean diameter (GMD) and mean weight diameter (MWD) first increased and then decreased, with maximum values after 10-year straw return at 1.20 mm and 1.63 mm, respectively. Solid state 13C NMR (Nuclear Magnetic Resonance) indicated O-alkyl C to be the dominant chemical component of soil OC over different years of straw return. There were increases in aromatic C, aromaticity, and hydrophobicity up to 10-year straw return, after which they decreased. A mantel test confirmed positive correlations of the distributions of macroaggregates, microaggregates, OC of macroaggregates, and silt + clay with MWD and GMD, whereas the OC content of aggregates was positively correlated with O-OA and hydrophobicity. Long-term straw returns improved soil structure and stabilized soil OC, thereby facilitating soil sequestration of OC.

Changes in soil microbial carbon fixation pathways along the oasification process in arid desert region: A confirmation based on metagenome analysis

Microbial carbon fixation has been proved to play a key role in soil carbon accumulation in arid desert oasis, but the fixation mechanism remains unclear. To solve it, we used metagenomic sequencing technology to measure the changes of soil microbial community structure, carbon fixation–related genes and carbon fixation pathway, as well as their relationships with soil properties between natural desert shrubbery (CK) and four oasis farmlands with different cultivation years (i.e., 3, 18 and 30 years) in the arid desert region of northwest China. The results showed that the contents of four soil carbon fraction (soil organic carbon/SOC, soil recalcitrant organic carbon/ROC, soil water solution carbon /WSC, and microbial biomass carbon/MBC) all significantly increased with the cultivation years (30 years ≥ 18 years > 6 years ≥ 3 years ≥ CK) (P < 0.05). Microbial composition was significant difference among CK, 3-, 6-, 18- and 30-years cultivated farmlands. Bacteria were the soil dominant taxa, and its relative abundance gradually decreased with the cultivation years. Proteobacteria, Actinobacteria, Bacteroidetes and Acidobacteria were the dominant phylum of soil microorganisms in desert shrubbery and oasis farmlands. Their relative abundance changed obviously with cultivation years. Six microbial carbon fixation pathways. i.e., the reductive tricarboxylic acid cycle (rTCA), dicarboxylate/4–hydroxybutyrate cycle (DC/4–HB cycle), 3–hydroxypropionate bicycle (3–HP bi–cycle), 3–hydroxypropionate/4–hydroxybutyrate cycle (3–HP/4–HB cycle), Calvin cycle and the Wood–Ljungdahl pathway (WL pathway), were found in all soils, but only the rTCA, DC/4–HB, 3–HP/4–HB cycles and WL pathway significantly changed with the cultivation years. The rTCA cycle was the most common fixation pathway, followed by DC/4–HB cycle and 3–HP/4–HB cycle, while WL pathway was least detected. Soil properties, especially pH, recalcitrant organic carbon, bulk density, total salinity and soil water contents, affected microbial community composition and carbon fixation–related genes in the oasification process. Our results suggested that oasification affected microbial carbon fixation by changing the soil environment due to human agricultural activities. Limited by energy supply in the nutrient–poor soils, rTCA and DC/4–HB cycles were mainly used by microorganisms to fix carbon in oasis farmlands.

Integrating multisource information to delineate oasis farmland salinity management zones in southern Xinjiang, China

Soil salinization and the shortage of water resources have become important factors affecting the sustainable development of agriculture in the southern Xinjiang. Agricultural flooding in winter or spring is the main means to reduce the damage of secondary soil salinization in southern Xinjiang. However, the spatial heterogeneity of soil salinization is not considered in previous irrigation strategy. Excessive irrigation always leads to a serious waste of agricultural water resources. Irrigation zones delineation based on the degree of soil salinization is beneficial for the management of agricultural salinized land and the improvement of water use efficiency in arid areas. This study used 1599 sets of apparent electrical conductivity (ECa) data obtained before winter irrigation and after crop harvest to characterize soil salinity directly. And the spatial heterogeneity of soil salinity in the study area was analyzed directly using ECa values and statistical as well as geostatistical methods. Three main variables obtained from apparent electrical conductivity measurements (EC0.375, EC0.75, EC1.5), vegetation information (NDVI, GNDVI, SAVI), which indirectly reflected the degree of salinity, and environmental factors (Clay, Sand, Silt, DEM), which affecting the distribution of salinity, were used as auxiliary variables. Four zoning models including soil information, soil + vegetation information, soil information + environmental factors and soil + vegetation information + environmental factors were constructed. A multi-scale segmentation algorithm was used to delineate for four zone patterns and evaluate the results of management zones based on the different information. The results showed that there was a strong spatial heterogeneity of soil salinity in the study area, with the coefficients of variation of ECa all higher than 74 %. But the mean of coefficient of variation intra-zone in each zone after delineation was less than 24 %, which was significantly lower than the value before delineation. The zoning result based on only soil information was more fragmented than other zoning results, and the homogeneity intra-zone and heterogeneity among zones were both lower. This result was not desirable to the development and effective implementation of water resource allocation. Management zones delineation with additional vegetation information or environmental factors showed a better zoning result. Delineation using multisource data of soil, vegetation information and environmental factors not only had the highest homogeneity intra-zone and heterogeneity among zones, but also facilitated the implementation of variable-rate irrigation. Consequently, salinity management zoning, which integrates soil, vegetation information and environmental factors, will facilitate the implementation of efficient irrigation with variable irrigating rate.

Estimating non-productive water loss in irrigated farmland in arid oasis regions: Based on stable isotope data

In arid oasis regions, water resources are severely scarce, with agricultural water usage far exceeding that of more humid areas. As a result, assessing non-productive water losses in farmland becomes crucial for estimating the water requirements reliant on irrigation for oasis cultivation. From April 2018 to October 2021, we established an observation system in the Minqin Oasis farmland. By utilizing hydrogen and oxygen isotopes in precipitation, soil water, and maize stem xylem water, we quantified the non-productive water loss (FE) and soil water infiltration rate (fe) in maize fields. Our findings indicate: (1) The average non-productive losses from rainfall and irrigation in arid maize fields were 39 %, with peak losses reaching 58 %; (2) Non-productive losses due to evapotranspiration were mainly observed in June and July, while losses from infiltration predominantly occurred in April-May and August-September; (3) Crop evapotranspiration capacity emerged as a significant factor influencing evaporation losses, while individual irrigation amounts and rainfall determined soil infiltration losses. We believe that judiciously managing irrigation volume and adjusting irrigation strategies in arid farmlands could unlock substantial potential for conserving water resources.

Ammoniated straw incorporation coupled with N management synergistically enhanced soil structure and crop productivity in a desert oasis farmland

AbstractStraw return is the simplest and the most economic method to improve soil structure. Slow decomposition rate limits straw return in sandy fields, which has becoming one of the obstacles in sandy land reclamation. Ammonification of straw before return accelerates straw decomposition, but it requires the use of extra N fertilizer, however, little is known about N fertilizer management in fields with ammoniated straw incorporation. So, a 3‐year field experiment was conducted with different proportions of N fertilizer aimed to maize straw ammonification and field broadcasting, and evaluated straw decomposition proportion, straw N release, soil organic carbon content, soil aggregates, soil water and N availability, and grain yield. Total N application rate was 300 kg per hectare, with five N input amounts for straw per hectare ammonification: 0 (SN0), 40 (SN40), 80 (SN80), 120 (SN120), and 160 (SN160) kg, and the rest of N broadcasted in soil during maize growing season. Ammonification accelerated straw decomposition and N release, and these effects showed no significant difference between SN80, SN120, and SN160. After straw decomposition for 150 days, the decomposition proportion was 62.1%, 53.0%, and 39.2% in SN80, SN40, and SN0, respectively. After 3 years of straw return, SN80 exhibited a significantly higher mean weight diameter of soil aggregates (35.6% higher), organic carbon content (18.4% higher), water‐holding capacity (17.4% higher), and soil water storage (17.2% higher) than SN0. Additionally, SN80 and SN120 showed the most significant effect on “N slow‐release” in soil. The above effects resulted with more available soil water and N used for crop growth, and increased grain yields (18.1% higher) and water use efficiency (18.6% higher) in SN80, compared with SN0. Hence, we conclude that a proper N allocation between straw and soil can synergistically enhance soil structure and crop productivity in sandy farmlands. This founding would provide scientific and technological support for straw return in sandy fields and is beneficial to sustainable development of oasis.

Analysis of the Expansion Characteristics and Carrying Capacity of Oasis Farmland in Northwestern China in Recent 40 Years

An oasis is a unique landscape that fuels human subsistence and socioeconomic development in the desert ecosystem. However, the overexpansion of oases, especially farmlands, poses severe threats to available land and water resources. This study aims to assess the expansion levels, carrying capacity dynamics, and planting structure optimization to maximize economic returns in northwest China’s five Typical Oasis Groups (5TOGs) using uniform data sources, time scales, and methods. Satellite products and a water-heat balance model were used to evaluate the changes in the area and carrying capacity dynamics of the 5TOGs. A linear programming approach was used to optimize each oasis’s cropping structure for the carrying level scenario. The results showed that the area of 5TOGs has expanded from 1980–2020, and the increment of oasis farmland is the main driver of oasis expansion. The most dramatic expansion of oases and their farmlands occurred during 2010–2020. As a consequence, the carrying capacity of each oasis is deteriorating with this expansion. The additional water resources to support this expansion of the oases and their farmlands come from groundwater, which is declining rapidly. Based on the optimized planting structure, cotton remains the main crop in Xinjiang oases with more than 60% area, the cotton area should be reduced in the Hotan River Oases, and the planting structure of the Heihe River Oasis will remain unchanged. The findings of this study have provided a quantitative analysis of oasis expansion and planting structure optimization, which have practical implications for water resource management and sustainable development of agriculture to maintain the stability of the oasis ecosystem.

Soil water and salt migration in oasis farmland during crop growing season

Soil water and salt migration in oasis farmland during crop growing season

Stable water isotope monitoring network of different water bodies in Shiyang River basin, a typical arid river in China

Abstract. Ecosystems in arid areas are fragile and are easily disturbed by various natural and human factors. As natural tracers widely exist in nature, stable isotopes can be valuable for studying environmental change and the water cycle. From 2015 to 2020, we took the Shiyang River basin, which has the highest utilization rate of water resources and the most prominent contradiction of water use, as a typical demonstration basin to establish and improve the isotope hydrology observation system. The data in the observation system are classified by water type (precipitation, river water, lake water, groundwater, soil water, and plant water). Six observation systems with stable isotopes as the main observation elements have been built. These include river source region, oasis region, reservoir channel system region, oasis farmland region, ecological engineering construction region, and salinization process region; meteorological and hydrological data have also been collected. We will gradually improve the various observation systems, increase the data of observation sites, and update the data set yearly. We can use these data to research the continental river basin ecological hydrology, such as surface water evaporation loss, landscape river water cycle impact of the dam, dam water retention time, oasis farmland irrigation methods, and the atmosphere, such as the contribution of inland water circulation to inland river precipitation, climate transformation, below-cloud evaporation effect, and extreme climate events, which provides a scientific basis for water resources utilization and ecological environment restoration in the arid area. The data sets are available at https://doi.org/10.17632/vhm44t74sy.1 (Zhu, 2022).

Multiple sources characteristics of root water uptake of crop under oasis farmlands in hyper-arid regions

Understanding the water use strategy of crops is important for maintaining the stability of agricultural production and improving water use efficiency (WUE). Affected by a variety of water sources and hyper-arid climate, the characteristics of root water uptake (RWU) in seed maize are extremely complicated but underestimated in oasis farmlands with shallow groundwater. We hypothesized that isotope (δ2H and δ18O) measurements over three years coupled with a MixSIAR model would reveal the characteristics of RWU in maize. Stable water isotopes in oasis farmlands were continuously observed from 2019 to 2021. Over the growing season, the soil matrix potential increased with soil depth. The isotopes in stem water had high similarity to groundwater, irrigation water, and soil water. The contributions of soil water in 0–20 cm, 20–40 cm, 40–60 cm, and 60–100 cm soil layers to RWU in maize were 29.7%, 12.2%, 14.8%, and 43.3%, respectively. From the jointing stage to the dough stage, the depth of RWU in maize was from shallow to deep; but after the dough stage, the depth of RWU in maize was from deep to shallow. Crops might prefer to absorb more groundwater and irrigation water in oasis farmlands with shallow groundwater. This study provides insights into crop water uptake and agricultural water management in hyper-arid regions.

'Only One Earth' – Celebrating soil science on World Environment Day 2022

'Only One Earth' – Celebrating soil science on World Environment Day 2022

Resource Capture, Growth, and Productivity of Maize (Zea mays L.) in Response to Nighttime Warming Under Oasis Farmlands in Hyper-arid Regions

Resource Capture, Growth, and Productivity of Maize (Zea mays L.) in Response to Nighttime Warming Under Oasis Farmlands in Hyper-arid Regions

Soil macroporosity and water flow in the root zone of oases in hyper‐arid regions

AbstractThe characteristics of soil macropores and water infiltration are closely connected to the growth of plant roots and their root zone environment. However, it is unclear how the root zone environment of oasis farmlands regulates the development of soil macropores and water flow in hyper‐arid regions. The objective of this study was to investigate soil macropores and their effect on water flow under irrigated oasis farmlands using a combination of X‐ray computed tomography (CT) and dye tracer. It was hypothesized that the integration of CT and dye tracer could clearly reveal preferential flow through biopores and large pores of oasis soils. A helical medical CT scanner was used to quantify more information about soil macropores in the root zone, along with an in situ single‐ring dye infiltration experiment to reveal water flow in three different oasis farmlands (piedmont oasis farmland, marginal oasis farmland, and old oasis farmland). Soil macroporosity was 0.44% under crop rows, while soil macroporosity in the interrows was only 0.30% across the oasis farmlands. Biopores contributed 73% of the volume of the total macropores under crop rows. The stable infiltration rate in the interrows was 0.3 mm min−1, which was significantly (p &lt; 0.05) less than that under crop rows (0.7 mm min−1). Water flow under crop rows were mainly transported in biopores and large pores. The contribution of macropores to preferential flow under crop rows was 4.8 times larger than interrows. The integration of CT and dye tracer was a more holistic technique, which adequately revealed that oases had preferential flow affected by biopores and large pores, resulting in higher solute and contaminant transport.Key Points Soil macropores and preferential flow affected by crop roots were investigated in hyper‐arid regions. The integration of CT and dye tracer adequately identified preferential flowpaths of oasis soils. Biopores were larger under crop rows than interrows. Preferential flow transported in biopores and large soil pores under crop rows.

Dynamic Patterns of the Vertical Distribution of Vegetation in Heihe River Basin since the 1980s

The vertical distribution of vegetation in Heihe River Basin has presented a significant dynamic change in the different elevation zones since the 1980s. To explore the dynamic patterns of vegetation types located in the different elevation zones of Heihe River Basin, this study collected 440 field sampling datapoints of vegetation types, remote sensing images, climatic observation data, and DEM and preprocessed them. On the basis of the vegetation distribution and the terrain characteristics of Heihe River Basin, this study classified the vertical distribution of vegetation in Heihe River Basin into six vegetation zones, namely, the oasis farmland and desert zone, desert-steppe zone, dry scrub-steppe zone, mountain forest-steppe zone, subalpine scrub-meadow zone, and alpine cold desert-meadow zone. Moreover, the mean annual biotemperature (MAB) and total annual average precipitation (TAP) were used to analyze the relationship between vegetation change and climate change in the different elevation zones. The results show that the change rate of vegetation was up to 25.75% in Heihe River Basin. The area of vegetation that changed in the oasis farmland and desert zone was the largest (7224 km2), and the rate of vegetation that changed in the mountain forest-steppe zone was up to 56.93%. The mean annual biotemperature (MAB) and total annual average precipitation (TAP) in the six elevation zones showed an increasing trend, in which the increased rate of TAP presented a downward trend with the increase of elevation, and that of MAB showed a continuous upward trend with the increase of elevation. The change rate of vegetation was generally higher than that of MAB and TAP in the low and middle vegetation zones. The influence intensity of human activities on vegetation change in the lower and middle elevation zones of Heihe River Basin was greater than that in the high elevation zone between the 1980s and the 2010s. MAB is the major impact factor to vegetation change in the alpine cold zone of Heihe River Basin.

Infiltration process of irrigation water in oasis farmland and its enlightenment to optimization of irrigation mode: Based on stable isotope data

The transmission of water through soil is one of the critical links to reflect the hydrological process. At present, there are controversies about the infiltration of farmland irrigation water and the replacement of old and new water in arid areas, which significantly reduces the scientific nature of the irrigation policy formulation. In this study, we monitored the temporal and spatial changes of stable isotopes of soil water in Minqin Oasis farmland, analyzed the infiltration process of irrigation water, used the MixSIAR isotope mixture model to estimate the contribution of irrigation water to soil water and evaluated their effective contribution time to different soil layers. This study suggests that: The temporal and spatial changes in pore water isotope reflect the process of artificial irrigation and evaporation. Within 5 days after irrigation, the average contribution rate of irrigation at 0–20 cm, 20–60 cm, and 60–100 cm soil layers was 31.11 ± 17.74%, 19.17 ± 12.72%, and 31.56 ± 12.42%, respectively. Under the influence of soil water content, topography, and plastic film cover, the effective contribution time of irrigation water to 0–20 cm and 60–100 cm soil layers was more than 5 d, and the effective contribution time to the 60–100 cm soil layer is only 4 d. The research results will help understand the hydrological process of farmland in the arid oasis area and provide a scientific basis for improving agricultural irrigation mode, which will help realize the sustainable development of regional agriculture.

A joint method to quantify source contributions of heavy metals to ecological and human health risks in oasis farmland soil

AbstractSource identification and risk assessment of heavy metals are ongoing hot topics in current research, but few studies have been performed on the linkage mechanism between them. In the past, the amount of heavy metals discharged was the identification criterion for high‐risk source but failed to consider different toxicity of heavy metals in the risk level of each pollution source. Therefore, it is impossible to accurately determine high‐risk pollution source. For this situation, this study introduced a risk assessment model based on the source apportionment model, which can quantitatively analyze the source‐based risk. Meanwhile, pollution assessment indexes and a risk assessment model were applied to evaluate the levels of pollution and risk of heavy metals, showing that lead (Pb) caused relatively serious pollution and arsenic (As) generated the highest ecological risk and noncarcinogenic risk. Positive matrix factorization (PMF) model identified and quantified the sources of heavy metals (coal‐related activities source, mixed source of mining and traffic emissions, industrial activity source, agricultural source related to the application of agrochemicals) with the corresponding contributions of 42, 30, 26, and 2%, respectively. Then PMF was combined with potential ecological risk index and human health risk assessment model to quantify the risk from pollution sources, indicating that the coal‐related activities source was the largest pollution source (31–36%) that caused human health risks, while the mixed source of mining and transportation emissions posed the greatest threat (29%) to the ecosystem health. Therefore, both sources should be identified as the priority pollution sources.