Typical Region Research Articles

Hydrochemical Characteristics and Suitability Assessment of Groundwater Quality for Irrigation

The hydrochemical properties of groundwater play a crucial role in crop growth and soil health, as well as the maintenance of irrigation equipment. To ensure suitable water quality for irrigation, the present study was conducted to evaluate the hydrochemical properties of irrigation groundwater in a typical agricultural region of Serbia. Groundwater was sampled at three monitoring locations in the Srem region in Republic of Serbia between 2011 and 2020. Examined parameters included electrical conductivity (EC), total dissolved salts (TDS), pH values, and the concentrations of cations (sodium (Na+), calcium (Ca2+), magnesium (Mg2+) and potassium (K+)) and anions (bicarbonate (HCO3−), chloride (Cl−), sulfate (SO42−), and nitrate (NO3−)). Further assessment was done using three classification systems; Nejgebauer’s, the US USSL, and the FAO classification. To obtain a more detailed assessment, additional indices were included, such as Soluble Sodium Percentage (SSP), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Permeability Index (PI), Kelly’s Ratio (KR), Magnesium Adsorption Ratio (MAR), and Total Hardness (TH). The PCA analysis detected that the concentration of K+, Ca2+, and Na+ in the irrigation water were lower in recent years, while the concentration of Cl− was higher. The cluster analysis grouped the parameters into three clusters; I—electroconductivity, II—dry residue and HCO3−, and III—other water parameters for all three monitoring localities. According to the applied classifications, the majority of underground water samples were suitable for irrigation. However, some samples fell out of the range of the first class, indicating the need for regular water quality monitoring. In light of climate changes that influence water deficiency, the urgent need for wise and sustainable water use implies the application of a comprehensive approach to irrigation water quality assessment, as shown in this study.

Exposure Characteristics and Human Health Risk Assessment of Herbicides in Water in a Typical Region of Northeastern China

Exposure Characteristics and Human Health Risk Assessment of Herbicides in Water in a Typical Region of Northeastern China

Estimating the Past and Future Trajectory of LUCC on Wetland Ecosystem Service Values in the Yellow River Delta Region of China

Land use/cover change (LUCC) can impact the provision of ecosystem service values (ESVs), particularly in wetland regions that are subject to frequent and unsustainable land conversions. Exploring the past and future trajectory of LUCC and its effects on ESV has a great significance for wetland management and habitat stability. This study tried to reveal the patterns and magnitude of LUCC on ESV under varying land development scenarios in the Yellow River Delta region, which is a typical region undergoing serious degradation in China. In this study, a combined approach utilizing equivalent coefficients of ecosystem services was employed to determine the ESV of the wetland in relation to the major land use types (LUTs). The Markov–FLUS model was then used to simulate LUTs across multiple scenarios in 2030 and to clarify the relationship of ESV between wetland and other LUTs. The results indicated that the wetland was severely degraded, with a loss in area of 6679.89 ha between 2000 and 2020. Cropland and water body were the main sources of diversion and turnover for the wetland, respectively. Despite the multiple scenario projections revealed, the wetland area exhibited a similar growth rate and a homogeneity in ESV under the natural development (ND), urban construction and development (UCD), and the ecological development (ED) scenarios. The ED scenario was deemed the optimal development strategy for the wetland ecosystem. Our research will improve the comprehension of land development decisions and promote sustainable development in estuarine wetland areas.

Microstructural evolution and anti-corrosion properties of laser cladded Ti based coating on Q235 steel

Titanium (Ti) based coatings laser cladded on steels could effectively protect steels from corrosion in the marine environment. However, the microstructural evolution and underlying solidification mechanisms for Ti based coatings laser cladded on steels are still unclear due to the nonequilibrium solidification processes during laser cladding. In this study, a Ti based coating was prepared on a Q235 steel by laser cladding. The microstructural evolution and corrosion properties of the coating were systematically investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), electron probe micro-analysis (EPMA) and electrochemical measurements in 3.5 wt% NaCl solution. Four typical regions form in the Ti based coating and the constituent phases evolve from α-Fe + TiFe2 phases to TiFe2 phase, then to TiFe phase, and finally to Fe0.2Ti0.8 (metastable β-Ti) + TiFe + Ti2Fe phases from the fusion interface to the coating surface. Temperature gradients and solidification rates determine the microstructure morphologies of the Ti based coating, and the contents of Fe in the Ti based coating evolve and affect the phase transformations at different distances from the fusion interface. Moreover, the Ti based coating shows better anti-corrosion properties than the substrate. The effect of micro-strain at different regions on the microhardness and corrosion properties is also discussed. This study can be the base of optimizing the microstructure of laser cladded Ti based coatings on steels for better corrosion performances.

Occurrence, source apportionment, and ecological risk of legacy and emerging per- and poly-fluoroalkyl substances (PFASs) in the Dahei river basin of a typical arid region in China

Per- and poly-fluoroalkyl substances (PFASs) are artificial chemicals with broad commercial and industrial applications. Many studies about PFASs have been conducted in densely industrial and populated regions. However, fewer studies have focused on the PFASs’ status in a typical arid region. Here, we investigated 30 legacy and emerging PFASs in surface water from the mainstream and tributaries of the Dahei River. Our results revealed that total PFASs concentrations (∑30PFASs) in water ranged from 3.13 to 289.1 ng/L (mean: 25.40 ng/L). Perfluorooctanoic acid (PFOA) had the highest mean concentration of 2.44 ng/L with a 100% detection frequency (DF), followed by perfluorohexanoic acid (PFHxA) (mean concentration: 1.34 ng/L, DF: 59.26%). Also, perfluorohexane sulfonate (DF: 44.44%), perfluorobutane sulfonate (DF: 88.89%), and perfluorooctane sulfonate (PFOS) (DF: 92.59%) had mean concentrations of 12.94, 2.00, and 1.05 ng/L, respectively. Source apportionment through ratio analysis and principal component analysis-multiple linear regression analysis showed that treated or untreated sewage, aqueous film-forming foam, degradation of precursors, and fluoropolymer production were the primary sources. The PFOS alternatives were more prevalent than those of PFOA. Conductivity, total phosphorus, and chlorophyll a positively correlated with Σ30PFASs and total perfluoroalkane sulfonates concentrations. Furthermore, ecological risk assessment showed that more attention should be paid to perfluorooctadecanoic acid, perfluorohexadecanoic acid, perfluorooctane sulfonate, perfluorohexane sulfonate, and (6:2 and 6:2/8:2) polyfluoroalkyl phosphate mono- and di-esters. The mass load of PFASs to the Yellow River was 1.28 kg/year due to the low annual runoff in the Dahei River in the arid region. This study provides baseline data for PFASs in the Dahei River that can aid in the development of effective management strategies for controlling PFASs pollution in typical arid regions in China.

A Dataset on Population Activity Patterns in Typical Regions of North China

This data article describes the "Typical Regional Activity Patterns" (TRAP) dataset, which is based on the Tackling Key Problems in Air Pollution Control Program. In order to explore the interaction between air pollution and physical activity, we collected activity patterns of 9,221 residents with different occupations and lifestyles for three consecutive days in typical regions (Jinan and Baoding) where air pollutant concentrations were higher than those in neighboring areas. The TRAP dataset consists of two aspects of information: demographic indicators (personal information, occupation, personal habits, and living situation) and physical activity pattern data (activity location and intensity); additionally, the exposure measures of physical activity patterns are included, which data users can match to various endpoints for their specific purpose. This dataset provides evidence for exploring the attributes of activity patterns of residents in northern China and for interdisciplinary researchers to develop strategies and measures for health education and health promotion.

Overcome discrimination for older workers to achieve equality and sustainable development

Transformation of the world population age structure happens at a fast pace and creates problems of increasing social expenditures. However, Industry 4.0 technologies create large-scale opportunities for extending the labor activity of the older population. In Russia, share of people over working age is 22%, and it will increase by another 15% in next 30 years. At the same time, older people are discriminated in the labor market. The article is devoted to the study of job and salary discrimination of elderly workers in the Republic of North Ossetia-Alania as a typical Russian region with tight labor market and a deteriorating demographic situation. Methods of statistical and graphical analysis, factual and sociological research were used. Conclusions have been drawn about the predominance of the model of preserving the employment of older workers in public administration, education, science and health care; the influence of the indexation rate of pensions for non-working pensioners on their informal employment; the preservation of wage disparities for older people employed in the regional economy. The internal gender and age discrimination that has developed in the field of remuneration of older age groups has been revealed: discrimination of women's labor in all age cohorts and types of employment; inter-cohort discrimination of older men's labor within one type of employment; discrimination of wage growth rates of employees of different types of employment. Measures to improve the efficiency of regulating the employment of older workers are proposed.

Determination of optimal dimensions of hybrid AC/DC distributed generation system with renewable sources for autonomous power supply of remote locations

In this paper, an autonomous hybrid power system with direct voltage and alternating voltage busbars with connected renewable sources and traditional sources that support renewable sources in the demand coverage during periods of power shortage in the system is proposed for power supply of remote locations. The issues of synthesis of the optimal structure of an autonomous system consisting of PV and WT generators with an integrated system of electric energy batteries (EEB) and diesel- generator station, at which the high reliability of power supply in remote areas is provided, are being studied. To optimally determine the installed capacity of the elements of the PV–WT–EEB–DG hybrid system, a machine learning algorithm (TLBO) is proposed, by means of which, based on the proposed multi-objective function, the most advantageous values of unit powers for PV and WT stations are determined, as well as the number of batteries and diesel generators that ensure the demand coverage in the hybrid system under various options for PV and WT generation shortage.In order to improve the efficiency of solving the optimization problem taking into account the variability of meteorological conditions, manifested in random and uncertain variability of PV and WT generation, as well as in the stochastic nature of the electricity consumption process, the studies on clustering these processes and determining typical scenarios for an array of hourly measurements of PV, WT and load generation during the year were carried out in the paper. Using the k–means approach, the numbers of clusters for PV, WT and load for typical geographic regions are determined. The results of the analysis of the optimal compositions of the hybrid AC-DS system in the PV, WT, BEE, DG in these regions are presented.

Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by the Parker Solar Probe and Its Probable Emission Mechanism

The Parker Solar Probe (PSP) provides us with an unprecedentedly close approach to the observation of the Sun and hence the possibility of directly understanding the elementary process that occurs on the kinetic scale of particles' collective interaction in solar coronal plasmas. We report a type of weak solar radio burst (SRB) that was detected by PSP when it passed a low-density magnetic channel during its second encounter phase. These weak SRBs have a low starting frequency of ∼20 MHz and a narrow frequency range from a few tens of MHz to a few hundred kHz. Their dynamic spectra display a strongly evolving feature of the intermediate relative drift rate decreasing rapidly from above 0.01 s−1 to below 0.01 s−1. Analyses based on common empirical models of solar coronal plasmas indicate that these weak SRBs originate from a heliocentric distance of ∼1.1–6.1 R S (the solar radius), a typical solar wind acceleration region with a low-β plasma, and that their sources have a typical motion velocity of ∼v A (Alfvén velocity) obviously lower than that of the fast electrons required to effectively excite SRBs. We propose that solitary kinetic Alfvén waves with kinetic scales could be responsible for the generation of these small-scale weak SRBs, called solitary wave radiation.

A Novel Comparison of Charotar Region Wheat Variety Classification Techniques using Purely Tree-based Data Mining Algorithms

Techniques for classifying data using data mining are now a day prevalent in agriculture. The method of classifying seeds involves grouping various seed varieties according to their morphological characteristics. To accomplish categorization of the typical Charotar region (generally comprising Anand and Kheda districts of the Gujarat State of India) Gujarat Wheat (GW) varieties (TRITICUM – AESTIVUM) viz. GW 273, GW 496, GW 322, LOK-1, and GDW 1255 (TRITICUM – DURUM), Weka Explorer was used. The features used are area, perimeter, solidity, aspect ratio, major and minor axis of seed kernel, Hue, Saturation, Value, and SF1 (empirical). Features reduction was done using Information Gain (IG) and its modified version Gain Ratio (GR). This paper compares performance of Tree based data mining algorithms in classifying wheat varieties. For classification we used purely tree-based machine learning algorithms viz. J48, Random Forest, Hoeffding Tree, Logistic Model Tree (LMT), and REPTree. LMT- logistics regression method gives higher accuracy 96.4% compared to other classifiers. Hoeffding Tree classifiers stood second with 96% accuracy. For validation 10-fold cross validation was used. By reducing the number of folds in cross validation performance of most algorithms decreased except J48. The percentage of correctly classified instance increased for all algorithms when features were selected by GR except for J48.

Increasing employment of the elderly population for sustainable demographic development of the region

Russia, like a number of other countries, is experiencing a process of population aging, which is leading to an increased role in the employment of the older generation, while at the same time, employers have a negative perception of their labor potential. The article is devoted to substantiating the hypothesis that employment of older people is an important factor in demographic development. The object of the study is North Ossetia as a typical region of Russia with a worsening demographic situation and tension in the labor market. The work used methods of statistical and graphical analysis, the "resume test" method. The problem of discrimination in hiring workers of pre-retirement age. It has been shown that limited opportunities in the labor market for the older generation lead to a decrease in the level and quality of life, and degradation of human potential. Conclusions are drawn about a decrease in the efficiency of the regional labor market in terms of employment of the elderly. Recommendations are offered to regional bodies of state regulation of the economy on the institutional prevention of the practice of age discrimination among employees; development of flexible part-time employment models; organization of continuous professional training and advanced training.

Exposure risk assessment of representative phthalate acid esters and associated plastic debris under the agricultural land use in typical Chinese regions

Phthalate acid esters (PAEs) are frequently detected in the global environment and can cause potential health hazards. In this study, quantitative exposure risk assessment was undertaken to derive soil generic assessment criteria (GAC) for six representative PAEs under the agricultural land use in the evaluated Chinese regions, which coupled multi-media transport and human exposure models based on multiple exposure pathways including vegetables consumption, dermal absorption, ingestion of soil and dust, and the exposure from non-soil sources. It is identified that the PAEs in agricultural soil are dominated by DEHP and DnBP representing 72–96% of the total PAEs. The GAC for BBP and DEHP, calculated on the basis of region-specific exposure parameters and soil properties in various locations, are stringent, signifying greater potential health risks from exposure to them, warranting more rigorous contamination management. The proposed soil GAC for plastic debris are 100, 107, 73 and 88 mg kg−1 for Heilongjiang Province, Beijing City, Jiangsu and Guangdong Provinces respectively. Additionally, the potential risks of 1.68 × 10−6 and 7 × 10−6 are identified for BBP and DEHP in Guangdong Province as indicated by the exceedance of target risk level of 1 × 10−6, with the consumption of vegetables being the dominant contributor to the total estimated PAEs exposure. Overall, this methodology based on the coupled contaminant transport and exposure models incorporating region-specific data provides a technical framework to derive science-based soil GAC for representative PAEs for maintaining and assessing soil quality and food safety under the agricultural land use.

Long-Term Simulated Direct N2O Emissions from German Oilseed Rape Cultivation below the IPCC Emission Factor

The low nitrogen (N)-use efficiency of intensive winter oilseed rape (WOSR) cropping systems may cause negative environmental impacts, especially due to N leaching and gaseous losses. The aim of this study was to use data from field experiments (five sites across Germany representing typical WOSR regions) for parametrization of a nitrous oxide (N2O) emission component for implementation into a process-based dynamic plant-soil-atmosphere model (PSAM). After calibration and evaluation with three years of field data from five different N fertilizer treatments, a long-term simulation with 25-year historical weather data was conducted to derive functional relations and emission factors (EFs). The model performed best at higher aggregation levels (cumulative emissions over the entire cropping period, R2 of 0.48/0.77 for calibration/evaluation), but also reasonably simulated short-term dynamics (e.g., fertilizer applications, extreme weather events). Site-specific and year-specific N2O emissions varied within the range of medians from 0.56–4.93 kg N2O-N ha−1. Mineral fertilizer-induced EFs at economic optimal N inputs ranged from 0.16–0.65%, which was markedly below the aggregated IPCC standard value of 1% for direct N2O emissions. Generally, the simulated emissions were consistently higher with finer soil textures and increasing N inputs. The process-based approach, moreover, allowed the identification of the major source of N2O, which mainly originated from nitrification processes.

Flow-induced high frequency vascular wall vibrations in an arteriovenous fistula: a specific stimulus for stenosis development?

Hemodialysis is the lifeline for nearly three million end stage renal disease patients worldwide. Native arteriovenous fistula (AVF) is the preferred vascular access, but 40% fail within 1 year. We recently demonstrated that AVFs harbour transitional flows and the goal of the present study was to investigate whether the associated high-frequency pressure fluctuations could promote vibrations within the vascular wall. We acquired MRI images and flow rates immediately after surgery in one patient and generated a 3D patient-specific model. High-fidelity fluid structure interaction simulations revealed the presence of wall vibrations in distinct frequency bands up to 200 Hz and amplitude of 200 μm. A sensitivity analysis to assess the impact of flow rates, and vascular wall stiffness and thickness, changes that typically occur during AVF maturation, confirmed the robustness of the results. Interestingly, the vibrations were always predominant at the anastomosis floor and on the inner venous side, which correlates with typical stenotic regions. As studies seeking to correlate aberrant stresses and vascular remodelling have been largely inconclusive, the focal colocalization between vibrations and stenosis may suggest an unknown mechanobiological process between high-frequency mechanical stresses within the vascular wall and adverse vascular remodelling.

DEMOGRAPHY OF SOUTHERN UKRAINE IN THE LAST QUARTER OF THE 18 th CENTURY: SCIENTIFIC MODELS AND THE RESULTS OF THEIR IMPLEMENTATION

This article explores the demographic processes in the territories of the former Domain of the Lower Zaporizhian Host of the last quarter of the 18th century. It has been shown that the relevance of this research goes well beyond the scope of demography and is closely related to the modern tendencies of using ‘Novorossiya’ concept. The developed research model is based on information from registers of births, marriages and deaths, as well as on findings, map books and audit evidence and envisages the use of demographic and sociological methods of research of the impact of Zaporizhian Cossacks and various migrant streams on population social structure and of horizontal contacts between its different segments. The reasons arise to explore the fertility dynamics in families representing different social segments: urban commoners, subjects of landlords, the military and their subjects. It has been shown that the fact of excess mortality among the military was enhanced by the effect of restrictions imposed by age peculiarities and ex-soldiers’ matrimonial strategies on natural increase in this social category. Opportunities for expansion in the number of non-Ukrainian population through settlement of the military in the surroundings decreased. Information from registers of births, marriages and deaths about godparents and married couples has enabled the use of M. Granovetter’s option of ‘the Strength of the Weak Ties’ permitting to identify informal small reference groups at the level of populated localities, their role and number in a community, their isolated or open status, formation criteria, number of their members and period of existence. The suggested model offers the possibility to trace the process of ex-Zaporizhian Cossacks transition to other social categories, degree of settlement in a region of influx from various Ukrainian lands as well as from typical Muscovite regions.

Hybrid-order soft trust region-based sequential convex programming for reentry trajectory optimization

Due to the complex aerodynamic effects, the reentry trajectory optimization problem is highly nonlinear. When using sequential convex programming (SCP) methods to solve it, the iteration solution is difficult to converge. To improve this, we propose a hybrid-order soft trust region-based SCP method. We analyze the penalty effect of typical trust regions. Based on the analysis, we develop a hybrid-order soft trust region combining a small-weight first-order component and a higher-order components. To solve the subproblem reliably and effectively, we equivalently reformulate it as a second-order cone programming (SOCP) form through the relaxation technique. Combined with the line search method, we further design an SCP algorithm with guaranteed convergence under some assumptions. In the numerical simulations, the effectiveness and robustness of the proposed method have been verified using a nominal case and 200 Monte Carlo cases.

Coniferous Forests Aboveground Biomass Inversion in Typical Regions of China with Joint Sentinel-1 and Sentinel-2 Remote Sensing Data Supported by Different Feature Optimizing Algorithms

Multispectral remote sensing (RS) data and synthetic aperture radar (SAR) data can provide horizontal and vertical information about forest AGB under different stand conditions. With the abundance of RS features extracted from multispectral and SAR datasets, a key point for accurate forest AGB estimation is to use suitable feature optimization inversion algorithms. In this study, feature optimization inversion algorithms including multiple linear stepwise regression (MLSR), K-nearest neighbor with fast iterative feature selection (KNN-FIFS), and random forest (RF) were explored, with a total of 93 RS features working as inversion model input for forest AGB inversion. The results showed that KNN-FIFS with the combination of Sentinel-1 and Sentinel-2 performed best at both test sites (R2 = 0.568 and RMSE = 15.05 t/hm2 for Puer and R2 = 0.511 and RMSE = 32.29 t/hm2 for Genhe). Among the three feature optimization inversion algorithms, RF performed worst for forest AGB estimation with R2 = 0.348 and RMSE = 18.06 t/hm2 for Puer and R2 = 0.345 and RMSE = 35.98 t/hm2 for Genhe using the feature combination of Sentinel-1 and Sentinel-2. The results indicated that a combination of features extracted from Sentinel-1 and Sentinel-2 can improve the inversion accuracy of forest AGB, and the KNN-FIFS algorithm has robustness and transferability in forest AGB inversions.

Changes in boiling regime and heat transfer effectiveness during water droplet collision with a superheated wall

We experimentally investigated changes in boiling regime and heat transfer effectiveness when single droplets collided with superheated substrates at various initial temperatures. Saturated water droplets colliding at constant speeds were studied over a range of initial substrate temperatures that spanned all boiling regimes from nucleate through transition to film boiling. Space- and time-resolved infrared thermometry and convectional shadowgraph imaging were used to precisely derive local heat transfer distributions and detect characteristic boiling regimes. The results confirmed the existence of the typical regions of a boiling curve: nucleate, transition, and film. The transition boiling regime could be subdivided into three sub-regimes—bubbly, oscillating, and fingering—during which the heat transfer effectiveness (THE) varied in a non-linear manner, exhibiting local minima and maxima. To facilitate interpretation of non-linear variations in HTE during transition boiling, the basic physical parameters of local heat flux, contact area, and residence time were quantitatively measured using obtained thermometry images. In the transition boiling regime, HTE first rapidly decreased during bubbly boiling principally because of a substantial decrease in the droplet residence time. And THE increased during oscillating boiling because of contact area expansion and increased heat flux. Finally, THE decreased during fingering boiling due to substantial reduction in the area fraction of liquid contact. When liquid-solid contact was completely prohibited, stable film boiling was stable. Thus, the dynamic Leidenfrost temperature point could be detected based on heat transfer characteristics, rather than collision dynamics.

Nature's contributions to people responding to landscape stability in a typical karst region, southwest China

Understanding the response of nature's contributions to people (NCP) to change in landscape stability may constrain and guide human modification of nature. However, the effects of landscape stability on NCP, in the context of active human modification, remain unclear. To address this issue, we chose the Wujiang River Basin in the Yangtze River Economic Belt of China as a study area and quantified landscape stability in 2000, 2010, and 2020 under different scenarios. Environmental protection and comprehensive development scenarios were simulated for 2030 using the patch-generating land use simulation (PLUS) model. For current and future scenarios, NCP were assessed in terms of indicators, which included habitat creation and maintenance (NCP1), regulation of freshwater (NCP6), and protection of soils (NCP8). Under the current status quo, urban expansion was 491.547 km2, and landscape stability showed a decreasing trend, with the mean value decreasing from 0.049 in 2000 to 0.015 in 2020. In future scenarios, landscape stability was highest under the comprehensive development scenario. In addition, in terms of changes in NCP, the high-value contributions declined by 16%–48% from 2000 to 2020. Our results clarified how NCP respond to landscape stability. These results can help conservation managers develop more targeted ecological strategies that will constrain human modification activities to enhance well-being.

The mass accretion history of dark matter haloes down to Earth mass

ABSTRACT We take advantage of the unprecedented dynamical range provided by the ‘Cosmic-Zoom’ project to study the mass accretion history (MAH) of present-day dark matter haloes over the entire mass range present in the Lambda cold dark matter paradigm when the dark matter is made of weakly interacting massive particles of mass 100 GeV. In particular, we complement previous studies by exploring the MAHs of haloes with mass from $10^8\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$ down to Earth mass, $10^{-6}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$. The formation redshift of low-mass haloes anticorrelates weakly with mass, peaking at z = 3 for haloes of mass $10^{-4}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$. Even lower masses are affected by the free-streaming cut-off in the primordial spectrum of density fluctuations and form at lower redshift. We compare MAHs in our simulations with predictions from two analytical models based on the extended Press–Schechter theory (EPS), and three empirical models derived by fitting and extrapolating either results from cosmological N-body simulations or Monte Carlo realizations of halo growth. All models fit our simulations reasonably well over the mass range for which they were calibrated. While the empirical models match better for more massive haloes, $M\gt 10^{10}\ h^{-1}\,\mathrm{{\rm M}_{\odot }}$, the analytical models do better when extrapolated down to Earth mass. At the higher masses, we explore the correlation between local environment density and MAH, finding that biases are relatively weak, with typical MAHs for haloes in extremely low-density and in typical regions differing by less than 20 per cent at high redshift. If this result can be extrapolated to lower halo masses, we conclude that EPS theory predicts the hierarchical build up of dark matter haloes quite well over the entire halo mass range.