Responses of runoff and sediment yield to slope length and gravel content of Lou soil engineering accumulation slope in Guanzhong region, Northwest China

With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.

[Spatial and temporal distribution characteristics of extreme wind and its effect on wind erosion in Northeast China]

Under the background of climate change, extreme wind events occur frequently in Northeast China, and the soil erosion caused by these extreme wind events has attracted progressively more attention from scholars. We used the methods of linear analysis, Sen+Mann-Kendal trend analysis, and Kriging interpolation to analyze the spatial and temporal characteristics of extreme wind in Northeast China from 2005 to 2020, and used the RWEQ wind erosion estimation model to calculate the annual soil wind erosion of typical wind erosion sites and wind erosion under extreme wind conditions. The results showed that the extreme wind frequency in Northeast China presented a significant upward trend from 2005 to 2020, with an increase of 2.9 times·a-1. The annual average extreme wind frequency in Northeast China ranged from 1 to 49 times·a-1, and the high frequency areas were distributed in the northwest of Xilin Gol, the west of the Hulunbuir Plateau, and the northeast of Changbai Mountain. The average contribution rate of extreme wind to soil wind erosion in four typical sites (Xilinhot, New Barhu Right Banner, Nenjiang, and Tongyu) was 31%.

Corrigendum: Impact of climate change and rubber (Hevea brasiliensis) plantation expansion on reference evapotranspiration in Xishuangbanna, Southwest China

[This corrects the article DOI: 10.3389/fpls.2022.830519.].

Identification of Key Antioxidants of Free, Esterified, and Bound Phenolics in Walnut Kernel and Skin

Walnut is a natural source of antioxidants. Its antioxidant capacity is determined by the distribution and composition of phenolics. The key phenolic antioxidants in various forms (free, esterified, and bound) in walnut kernel (particularly seed skin) are unknown. The phenolic compounds in twelve walnut cultivars were analyzed using ultra-performance liquid chromatography coupled with a triple quadrupole mass spectrometer in this study. A boosted regression tree analysis was used to identify the key antioxidants. Ellagic acid, gallic acid, catechin, ferulic acid, and epicatechin were abundant in the kernel and skin. The majority of phenolic acids were widely distributed in the free, esterified, and bound forms in the kernel but more concentrated in bound phenolics in the skin. The total phenolic levels of the three forms were positively correlated with antioxidant activities (R = 0.76-0.94, p < 0.05). Ellagic acid was the most important antioxidant in the kernel, accounting for more than 20%, 40%, and 15% of antioxidants, respectively. Caffeic acid was responsible for up to 25% of free phenolics and 40% of esterified phenolics in the skin. The differences in the antioxidant activity between the cultivars were explained by the total phenolics and key antioxidants. The identification of key antioxidants is critical for new walnut industrial applications and functional food design in food chemistry.

Spatio-Temporal Distribution Characteristics and Driving Factors of Main Grain Crop Water Productivity in the Yellow River Basin

To reveal the relationship between agricultural water resource consumption and grain production in the Yellow River Basin, the irrigation water productivity (WPI), crop water productivity (WPC), total inflow water productivity (WPT), and eleven influencing factors were selected. The spatial and temporal distribution characteristics and driving factors of water productivity of the main crops in the Yellow River Basin were analyzed with the spatial autocorrelation analysis, grey correlation analysis, sensitivity analysis, and relative contribution rate. The results showed that the minimum mean values of WPI, WPC, and WPT were 0.22, 0.35, and 0.18 kg/m³ in Qinghai, respectively, the maximum mean value of WPI was 2.11 kg/m³ in Henan, and the maximum mean values of WPC and WPT were 0.71 and 0.61 kg/m³ in Shandong, respectively. The changing trends in WPI and WPT in Qinghai and in WPC in Shandong were insignificant, whereas the WPI, WPC, and WPT in other provinces showed a significant increasing trend. Water productivity displayed a certain spatial clustering feature in the Yellow River Basin in different years, such as a high-high (H-H) aggregation in Henan in 2005, and an H-H aggregation in Shanxi in 2015 for WPI. The water productivity had a significant positive correlation with the consumption of chemical fertilizer with a 100% effective component (CFCEC), effective irrigated area (EIA), plastic film used for agriculture (PFUA), and total power of agricultural machinery (AMTP), while it had a significant negative correlation with the persons engaged in rural areas (PERA). There was a large grey correlation degree between the water productivity and the average annual precipitation (AAP), CFCEC, PFUA, consumption of chemical pesticides (CFC), and AMTP in the Yellow River Basin, but their sensitivity was relatively small. The main driving factors were EIA (8.98%), agricultural water (AW, 15.55%), AMTP (12.64%), CFCEC (12.06%), and CPC (9.77%) for WPI; AMTP (16.46%), CFCEC (13.25%), average annual evaporation (AAE, 12.94%), EIA (10.49%), and PERA (10.19%) for WPC; and EIA (14.26%), AMTP (13.38%), AAP (12.30%), CFCEC (10.49%), and PFUA (9.69%) for WPT in the Yellow River Basin. The results can provide support for improving the utilization efficiency of agricultural water resources, optimizing the allocation of water resources, and implementing high-quality agricultural developments in the Yellow River Basin.

Corrigendum: Impact of climate change and rubber (Hevea brasiliensis) plantation expansion on reference evapotranspiration in Xishuangbanna, Southwest China

[This corrects the article DOI: 10.3389/fpls.2022.830519.].

[Baseflow variation and its response to precipitation in Jiuqushui watershed, Southern Jiangxi Province, China]

Baseflow is an important part of water resources. Exploring the characteristics of baseflow and its response to precipitation is of great significance to optimize the partition of water resources. Based on the data of daily precipitation and runoff from 1982 to 2019 in Jiuqushui watershed, we analyzed the characteristics of baseflow change, investigated the time lag effect of baseflow on precipitation, and calculated the contribution rate of precipitation to baseflow change by using digital filtering method, cross wavelet transform method, and slope change ratio of accumulative quantity method. The results showed that during the study period, the variation trend of annual baseflow depth and annual baseflow index was not significant, with annual average values of 384.21 mm and 0.44, respectively. The depth of baseflow in spring and summer was greater than that in autumn and winter, while the baseflow index showed an opposite pattern. Annual precipitation affected the dynamic change of annual baseflow depth, with the effects in spring and summer being stronger than that in autumn and winter. The lag time of baseflow in spring, summer, autumn and winter were 3.5-10.3, 1.5-8.5, 2-10, 2-13 and 5-20.5 days, while the average annual lag time was 6.4, 4.9, 5.3, 6.8 and 10.8 days, respectively. The annual baseflow depth changed abruptly in 1992. The contribution rate of precipitation to baseflow change was 68.2%, and that of other factors was 31.8%. The results could provide scientific basis for evaluating the hydrological effects of forests and ensuring water ecological security of rivers in the red soil region of southern China.

[Effects of biological crusts on soil organic carbon in sandlands under a precipitation gradient]

Biological crusts (Biocrusts) are important surface active coverings in arid and semi-arid regions, which affect the content of soil organic carbon (SOC), SOC labile fractions and stability of SOC through photosynthetic carbon fixation. At present, studies on the variation characteristics of SOC, SOC labile fractions and the stability of SOC in biocrusts are rather limited. In this study, two types of typical biocrusts (moss crusts and algae crusts) were selected along a precipitation gradient from northwest to southeast in the Mu Us Sandland (straight line distance 188 km) by measuring soil organic carbon (SOC), soil microbial biomass carbon (MBC), water soluble carbon (DOC), particulate carbon (POC), easily oxidizable carbon (ROC). We aimed to explore the effects of biocrusts on the stability of SOC and carbon decomposition across the precipitation gradient. Results showed that:1) Two types of biocrusts significantly increased the contents of SOC, MBC, DOC, POC, ROC and stability of SOC. Moss crusts increased SOC contents by 1.6 to 2.6 times as that of algae crusts. 2) The lowest SOC contents of the two types of biocrusts were 6.43 g·kg^-1 and 14.50 g·kg^-1 respectively, which showed an increasing trend with increasing precipitation along the gradient. 3) With the increases of precipitation, the decomposition time of moss litters gradually decreased. The decomposition coefficient of moss litters during the study period (From July to Feb-ruary of the next year) ranged from 0.010 to 0.014, which was significantly lower than that of vascular plants. The carbon release of moss litters from northwest to southeast was 8.09, 10.89, 12.88 g·kg^-1, respectively. 4) Results of canonical correspondence analysis showed that water vapor partial pressure, actual evapotranspiration, annual average temperature, subsurface short-wave radiation, potential evapotranspiration and vapor pressure difference were the key climate factors affecting the content of SOC and its active components. Silt content was the main soil factor affecting the content of SOC and its active components.

Impact of Climate Change and Rubber (Hevea brasiliensis) Plantation Expansion on Reference Evapotranspiration in Xishuangbanna, Southwest China

The expansion of rubber (Hevea brasiliensis) cultivation plantation over the past few decades has been significantly explosive in Xishuangbanna, southwest China. More and more evidences concerning the expansion of rubber plantations lead to the negative influence to local regional hydrology. It is vital to explore the impact of climate change and rubber (Hevea brasiliensis) plantation expansion on reference evapotranspiration (ET₀) for the sustainable and efficient use of regional water resources. In this study, the spatiotemporal variation of ET0 as well as its relationship in rubber plantations area in Xishuangbanna from 1970-2017 were analyzed by using trend, correlation and contribution analysis. The results showed that the rubber plantation was 12,768 ha yr^-1 from 1990 to 2017 in Xishuangbanna, and nearly 40.8% of new rubber plantations expanded above 900 m in altitude from 2000 to 2017. Sunshine duration and average relative humidity were the key meteorological factors that affect ET₀ in Xishuangbanna, with the sensitivity coefficient of 0.51 and 0.35, respectively. The multiyear relative change of ET₀ in Xishuangbanna was 9.18%, and the total contribution of major climate factors was 7.87% during 1970 and 2017. The average relative humidity in the plantation area decreases, which directly leads to the increase of ET₀. The amount of ET₀ change from 2000 to 2017 affected by climate change increased at 3.13 mm/10a, whereas it was 2.17 mm/10a affected by the expansion of rubber plantations by quantitative separation. ET₀ was significantly affected by climate change but intensified by the expansion of rubber plantation.

[Spatio-temporal variation of reference crop evapotranspiration and its climatic mechanism in Nenjiang River Basin, China]

To understand the temporal and spatial variations of reference crop evapotranspiration (ET₀) in Nenjiang River Basin, and clarify the effects of climatic factors on ET₀, we calculated the daily ET₀ of each station in Nenjiang River Basin from 1970 to 2019 by Penman-Monteith formula, analyzed the temporal variation trend and spatial distribution pattern of ET₀. We further quantitatively examined the sensitivity of ET₀ to meteorological factors by sensitivity analysis, and explored the contribution of meteorological factors to ET₀ changes. The results showed that ET₀ generally showed an insignificant decreasing trend during the study period in the Nenjiang River Basin. ET₀ decreased in spring, summer, and autumn, but increased in winter, and decreased from southeast to northwest. ET₀ had the highest sensitivity to relative humidity at both temporal and spatial scales. The sensitivity coefficients of mean temperature, relative humidity and wind speed increased gradually, while that of sunshine hours decreased gradually. ET₀ was sensitive to mean temperature in northern Greater Khingan Mountains and Lesser Khingan Mountains, while to wind speed in southern Greater Khingan Mountains and Songnen Plain. Wind speed was the main factor affecting the change of ET₀ in the whole year, spring, autumn, and winter. Sunshine hours was the main affecting factor in summer. The mean temperature and relative humidity had the greatest contribution to ET₀ in the north of Greater Khingan Mountains and Lesser Khingan Mountains, and it was the wind speed in Songnen Plain.

Institutional Design and Incentives for Migrant Workers to Participate in Social Insurance in China: Evidence From a Policy Experiment in Chengdu City

Rural-to-urban migration has increased rapidly in China since the early 1980s, with the number of migrants has reached 376 million by 2020. Despite this sharp trend and the significant contributions that migrants have made to urban development, the migrant workers have had very limited access to the social insurance that the majority of urban workers enjoy. Against the background of the social insurance system adjustment in Chengdu in 2011, this study uses a difference-in-differences (DID) model to empirically test the impacts of changes in the social insurance policy contribution rates on the social insurance participation rates of migrant workers, using the China Migrants Dynamic Survey (CMDS) data for 2009–2016. We find that the social insurance participation rate of migrant workers was significantly reduced after they were incorporated into the urban worker insurance system. There was no significant change in the wages of migrant workers, but the working hours were increased and their consumption level decreased. In other words, simply changing the social insurance model of migrant workers from “comprehensive social insurance” to “urban employee insurance” reduces the incentives for migrant workers to participate in insurance and harms the overall welfare of migrant workers. Our study indicates that the design of the social security policy is an important reason for the lower participation rate of migrants. It is necessary to solve the problem of insufficient incentives through the targeted social security policies; primarily, the formulation of a social security policy contribution rate suitable for the migrants, and the establishment of a comprehensive social security policy and the gradual integration of the social security system.

[Erosion process of loess slope and influencing factors in the loess hilly-gully region, China]

Rainfall intensity, slope length, and slope gradient are the important factors affecting runoff and sediment yield. In order to quantitatively analyze the effects of rainfall intensity, slope length, and slope gradient on the erosion process of Ansai loess slope in loess hilly and gully region, we analyzed the variation of runoff and sediment yield on Ansai loess with two slope lengths (5, 10 m), three slopes (5°, 10°, 15°) and two rainfall intensities (60, 90 mm·h^-1) in an indoor simulated rainfall experiment. The results showed that the initial runoff generation time decreased with the increases of slope length, though the overall change was not significant. The initial runoff generation time decreased with the increases of rainfall intensity. Compared with the intensity of 60 mm·h^-1, the initial runoff generation time decreased by 5.7-18 min under the intensity of 90 mm·h^-1. Among them, the runoff initiation time on the slope of 10° was the fastest. With the duration of rainfall, runoff yield rate increased rapidly at first, and then gradually fluctuated around a certain value. The sediment yield rate increased rapidly in a short period of time at the initial stage of runoff generation, and then decreased after reaching the maximum, and being gradua-lly stable. The rates of runoff and sediment yield increased with the increases of slope length and rainfall intensity, but the law of change with slope was not obvious. With the increases of rainfall intensity, slope length and gradient, the total sediment yield increased accordingly. Under the rainfall intensity of 90 mm·h^-1, the slope surface with the length of 10 m and slope of 15° generated rill, leading to the highest total erosion amount (11885.66 g). Under the rainfall intensity of 60 mm·h^-1, the erosion amount per unit area decreased with the increases of slope length, and there was a critical erosion slope length in 5-10 m slope section. Slope length, slope and rainfall intensity all played a promoting role in runoff process. Rainfall intensity, slope length, and their interaction contributed more to runoff yield rate and total erosion amount. Rainfall intensity contributed the most to runoff yield rate, with a contribution rate of 49.8%. The contribution rate of slope length to the total erosion was the largest, which reached 37.8%.

[Characterization of oil/water partition coefficient of chishao terpene glucoside components based on contribution rate of representative components for myocardial ischemia]

The components of traditional Chinese medicine(TCMCs) are the basic unit of raw materials for Chinese medicines, and their physical and chemical properties directly affect the choice of dosage forms and the optimization of prescriptions. However, most of TCMCs are multi-component complex systems, and the characterization of their overall properties is still in the exploration stage. On the basis of biological activity, the representative components are determined, and then the individual characteristics are fitted with the weight coefficient of efficacy contribution rate, which may provide reference for characterizing the overall properties of TCMCs. In this study, with the pharmacological effects of isoproterenol(ISO)-induced myocardial ischemia in rats as the indicators, the pharmacodynamic contribution rates of three representative components of chishao terpene glucoside components(CSTGCs) were evaluated by the normalization weighting method. The contribution rates of paeoniflorin, paeoniflorin and benzoylpaeoniflorin were 54.87%, 32.46% and 12.67%, respectively. The oil-water partition coefficients of paeoniflorin, albiflorin, benzoylpaeoniflorin in water and buffer solutions with different pH values were measured, and the oil-water partition coefficients of CSTGCs were characterized by the weight of their pharmacodynamics contribution rate. The results showed that the apparent oil-water partition coefficient(log P) of CSTGCs in the phosphate buffer system such as n-octanol-water(pH 2.0, 2.5, 5.0, 5.8, 6.8) were 0.18-0.22, indicating that CSTGCs have common absorption and low permeability, providing basis for the preparation of CSTGCs.

Decreased Contribution Rates Increase Public Pension Fund Revenue: Evidence from China

The basic pension plan for urban enterprise workers (PPUEW) is the primary form of public pension system in China and is managed by provincial governments. Although the federal government requires that employers contribute 20% and individuals 8%, provincial governments have the right to adjust the rate. As different rates apply in different provinces, this study assesses the effect of rates on enterprises' incentive to participate in the PPUEW, using data from the 2011 China Annual Survey of Industrial Firms. As rates increase, employers and employees pay more; however, once the contribution ratio reaches a tipping point, they try to reduce deductibles. The findings suggest that a lower contribution rate motivates enterprises to participate in the PPUEW and boosts the fund's revenue.

[Start-up Performance of Low-substrate Anaerobic Ammonium Oxidation Under Different COD Concentrations]

An anaerobic sequencing batch reactor(ASBR)was used to treat low-substrate simulated wastewater with NH₄⁺-N and NO₂^--N concentrations of (25.00±0.40) mg·L^-1 and (33.00±0.60) mg·L^-1, respectively. The COD concentrations were controlled at 5.00, 15.00, 30.00, and 50.00 mg·L^-1 by adding sodium acetate, and its effects on start-up of anaerobic ammonia oxidation (ANAMMOX) were investigated under the temperature of 30℃. The results showed that ① The start-up of ANAMMOX could be achieved successfully after 74, 94, 106, and 129 days. The nitrogen removal efficiency was optimum when the COD concentration was between 15.00 and 30.00 mg·L^-1. In the steady phase, the average effluent concentrations of NH₄⁺-N were 1.98 and 1.89 mg·L^-1, the average effluent concentrations of NO₂^--N were below 0.62 mg·L^-1, and the average effluent concentrations of TN were 2.37 and 2.28 mg·L^-1. ② The average contribution of heterotrophic denitrification to nitrogen removal decreased to 4.78%, 9.59%, 10.21%, and 36.50%, respectively, during start-up process. The average contribution of ANAMMOX to nitrogen removal gradually increased to 95.22%, 90.41%, 89.79%, and 63.50%, respectively. ③ The activities of ANAMMOX exceeded denitrification activities at 44, 76, 86, and 114 days, respectively, which finally reached 0.700, 0.690, 0.670, and 0.510 mg·(g·h)^-1, and the denitrification activities were 0.110, 0.130, 0.240 and 0.410 mg·(g·h)^-1, respectively. Thus, the research results have provided references for the application of ANAMMOX to engineering.

[Status of Antibiotic Contamination and Ecological Risks Assessment of Several Typical Chinese Surface-Water Environments]

To learn about the status of antibiotic contamination and their ecological risks in Chinese surface-water environments, the risk quotient (RQ) and joint risk quotient (RQ_SUM) methods were applied to assess the ecological risks of five typical surface-water environments in China during the flood season. The results showed that the main types of antibiotic contamination in the five regions were sulfamethoxazole (SMX), sulfamethazine (SM), erythromycin (ETM), roxithromycin (RTM), tetracycline (TC), oxytetracycline (OTC), norfloxacin (NOR), and ofloxacin (OFL). Among eight types of antibiotic contamination, sulfamethoxazole (SMX) and erythromycin (ETM) occupied a dominant position. The contribution rate of SMX in the Yangtze River Delta and Chaohu Basin was 91.1% and 98.5%, respectively. Meanwhile, the contribution rates of ETM in Jianghan Plain, Pearl River Delta, and Yellow River Delta were 94.4%, 81.8%, and 60%, respectively. Based on the joint risk quotients (RQ_SUM), the order of ecological risks in the research areas was:Jianghan Plain (20.204) > Yangtze River Delta (8.769) > Chaohu Basin (2.692) > Yellow River Delta (1.943) > Pearl River Delta (1.222).

[Effect of Substrate Ratio on Removal of Nitrogen and Carbon Using Anaerobic Ammonium Oxidation and Denitrification]

Real domestic sewage was treated in a sequencing batch reactor (SBR). When the partial nitrification of SBR was achieved, the effluent was fed with quantitative NaNO₂, which served as the influent of the anaerobic ammonium oxidation (ANAMMOX) process of the anaerobic SBR (ASBR). The effect of different substrate ratios on the removal of nitrogen and carbon using anaerobic ammonium oxidation and denitrification was investigated under conditions with a temperature of 24℃ and pH of 7.2±0.2. The results showed that ① the nitrogen removal efficiency was optimum when the influent NO₂^--N/NH₄⁺-N was 1.4-1.6. The average effluent concentrations of NH₄⁺-N, NO₂^--N, and chemical oxygen demand (COD) were 2.14, 1.07, and 30.50 mg·L^-1, and their removal rates were 93.62%, 97.79%, and 74.75%, respectively. The △NO₂^--N/△NH₄⁺-N and △NO₃^--N/△NH₄⁺-N ratios were 1.60 and 0.17, respectively. Total nitrogen was removed by the joint action of denitrifying and ANAMMOX bacteria. ② When the influent ratio of NO₂^--N/NH₄⁺-N increased, the contribution of ANAMMOX to nitrogen removal decreased, but the contribution of heterotrophic denitrification to nitrogen removal increased gradually. ③ The NH₄⁺-N and NO₂^--N degradation processes corresponded with zero-order reactions and fitted the linear relationship in the typical cycle. Their specific degradation rates were 0.404 and 0.599 mg·(g·h)^-1, respectively. Their ratio was 1.48, and the specific degradation rate of COD gradually increased.

[Effect of HRT on Nitrogen Removal Using ANAMMOX and Heterotrophic Denitrification]

Real domestic sewage was first treated in SBR and partial nitrification was achieved. When average concentrations of NH₄⁺-N, NO₂^--N, and COD were 37.27, 39.97, and 120 mg·L^-1, respectively, the effluent was delivered as influent of an anaerobic ammonia oxidation reactor (ASBR). The effect of different HRTs (36 h, 33 h, 30 h, 27 h) on nitrogen removal of ANAMMOX and heterotrophic denitrification were investigated under conditions of temperature of 24℃ and pH of 7.2±0.2. Results showed that 1 nitrogen removal efficiency was optimum with HRT of 33 h. The average total nitrogen load rate(TNLR)and total nitrogen removal rate(TNRR)were 0.056 kg·(m³·d)^-1and 0.050 kg·(m³·d)^-1, respectively. The average effluent concentrations of NH₄⁺-N, NO₂^--N, and COD were 1.36, 0.47, and 49.79 mg·L^-1, and removal rates were 96.30%, 98.83%, and 56.17%, respectively. △NO₂^--N/△NH₄⁺-N and △NO₃^--N/△NH₄⁺-N were 1.17 and 0.15, 0.15 and 0.11 less than theoretical ANAMMOX values (1.32, 0.26) due to heterotrophic denitrification. 2 The contribution of ANAMMOX to nitrogen removal decreased; however, the contribution of heterotrophic denitrification to nitrogen removal gradually increased with decreasing HRT. This provides a point of reference for ANAMMOX in engineering applications.

[Effects of Straw and Biochar Return in Soil on Soil Aggregate and Carbon Sequestration]

The aim of this work is to understand the effects of straw and biochar return in soil on the content, distribution, stability, and relative contribution rate of organic carbon for soil aggregates, which could be used to better understanding the stability of the soil carbon pool and the protection mechanisms under straw and biochar return. In this study, a field experiment was conducted to study the effects of straw and biochar return on soil aggregates and carbon sequestration characteristics in a rape-maize rotation planting system. Five treatments, including a control (no organic material added, CK), straw (CS), straw and microorganism (CSD), Biochar (BC), half straw and half biochar (CSBC), were used. The results indicated that ① Straw and biochar could improve the content of soil organic carbon, and the BC and CSBC treatments increased it by 16.88-17.37 g·kg^-1, values higher than those with the CS and CSD treatments (13.76-14.68 g·kg^-1); ② Compared with the CK treatment, CS and CSD treatments could increase the stability of the aggregates through significantly increasing the content of macro-aggregate by 94.00%-117.78% and significantly increasing the mean weight diameter (MWD), geometric mean diameter (GMD), and R_0.25 of water stable aggregates, but reducing the D value (P<0.05); and ③ With the increase in aggregate particle size, the content of organic carbon in the aggregates decreased first and then increased. The contribution rate of soil organic carbon in silt and clay was the highest (29.61%-42.18%), and the contribution rate of organic carbon in the macro-aggregate was the lowest (9.19%-17.81%). In addition to the CSD treatment, the CS, BC, and CSBC treatments reduced the contribution of larger aggregates (2-0.25 mm) and micro-aggregates (0.25-0.053 mm). In general, the benefit of straw return was better than that of biochar in promoting soil aggregation. However, the application of biochar was better than straw in improving the aggregates organic carbon content. The newly generated carbon from straw degradation was mainly distributed in large aggregates. Straw with microorganisms could promote the combination of carbon by different components in the larger aggregates. The carbon from biochar and straw with biochar treatments were mainly concentrated in micro-aggregates.

Response of microbial communities to roxarsone under different culture conditions

Roxarsone is a feed additive widely used in the broiler and swine industries that has the potential to contaminate the environment, mainly via the use of poultry manure as fertilizer, which results in release of inorganic arsenic to the soil and water. This study was conducted to investigate roxarsone degradation and the response of the microbial community under different culture conditions using high-throughput sequencing technology. Poultry litter was incubated for 288 h in the presence of roxarsone under light aerobic, dark aerobic, or dark anaerobic conditions. The results showed that roxarsone was completely degraded after 48 h of dark anaerobic incubation, while 79.9% and 94.5% of roxarsone was degraded after 288 h of dark aerobic and light aerobic incubation, respectively. Under dark aerobic conditions with microbial inhibitor sodium azide, roxarsone was rarely degraded during the 288 h of incubation, illustrating that microorganisms play an important role in roxarsone degradation. Microbial community structure was significantly different among various culture conditions. Olivibacter, Sphingobacterium, and Proteiniphilum were the top 3 genera in the control samples. Sphingobacterium and Alishewanella dominated the light aerobic samples, while the dominant microflora of the dark aerobic samples were Acinetobacter spp. Pseudomonas and Advenella were the predominant genera of dark anaerobic samples. This study emphasizes the potential importance of microbes in roxarsone degradation and expands our current understanding of microbial ecology during roxarsone degradation under different environmental conditions.

[Rock Weathering Characteristics and the Atmospheric Carbon Sink in the Chemical Weathering Processes of Qingshuijiang River Basin]

Carbon sink produced during rock weathering is critical to global carbon cycles. In this work, the major ion chemistry and ion sources of Qingshuijiang River Basin were investigated. The principal component analysis, mass balance approach and deduction method were applied for estimating the weathering rate and atmospheric CO₂ consumption via the chemical weathering of rocks. The results demonstrated that the chemical weathering of carbonate and silicate rocks within the drainage basin was the main source of the dissolved chemical substances in the Qingshuijiang River Basin, prior to carbonate rock weathering. Some 58.28% of the total dissolved chemical substances were derived from the chemical weathering of carbonate rock, 17.38% from the dissolution of silicate rock, and 17.74% from atmospheric CO₂ contribution rates. The chemical weathering rate of this catchment was estimated to be 109.97t·(km²·a)^-1, which was comparable to Wujiang River Basin, but higher than the average of global rivers. Furthermore, the atmospheric CO₂ consumption rate was estimated to be 7.25×10⁵ mol·(km²·a)^-1. The CO₂ flux consumed by the rock chemical processes within this catchment was 12.45×10⁹ mol·a^-1, of which about 63.13%(7.86×10⁹ mol·a^-1) was resulted from carbonate weathering and 36.87%(4.59×10⁹ mol·a^-1) from silicate weathering. The CO₂ consumed by rock chemical weathering in the Qingshuijiang River reduced the atmospheric CO₂ level and constituted a significant part of the global carbon budget. Correlation and spatial distribution analysis of SO₄^2-, F^-, NO₃^- showed that anthropogenic activities contributed remarkably to dissolved solutes and associated CO₂ consumption worldwide, and anthropogenic inputs probably contributed some 4.87% to the dissolved solutes in the Qingshuijiang River.

The Preventive Approaches of the Statutory Accident Insurance System and Their Effectiveness

For decades, prevention has been an integral and important part of the German statutory accident insurance system. The very close link between prevention, rehabilitation, and compensation, which is so typical for the German system, had an extremely positive effect on the frequency of notifiable occupational accidents. What is more, if we compare benefits and costs of the system, it appears that prevention has also been successful in a strictly monetary sense. After a short outline of the basic principles of the German accident insurance system, the authors take stock of the last 33 years. The period between 1960 and 1993 also covers the repercussions of the German reunification in 1990. The trends in accident and disease frequency are presented together with the trends in costs and benefits. To allow a realistic comparison, all figures are indicated in terms of 1960. It can be shown that the average contribution rate to accident insurance decreased in the period under consideration. This is particularly remarkable if we look at the enormous increase in contribution rates that took place in all other branches of social insurance. It is also noted that the contribution rates of the different industrial branches are immediately dependent on the accident risks in those industries. The last part of the article contains a qualitative and quantitative description of the prevention measures available to the German accident insurance institutions.