Search

BACKGROUND Water is critical to the production of crops, especially when faced with seasonal drought or freshwater scarcity. We compared the effect of negative pressure irrigation (NPI) on water use efficiency (WUE), nutrient uptake, yield and quality of Brassica chinensis L. using a greenhouse plot experiment. Three different water supply pressures (-5, -10 and -15 kPa), and a conventional irrigation (CK) treatment, were arranged in a randomized design with three replications. RESULTS Our results suggest that plant height, leaf area, number of leaves and ratio of root to shoot were significantly correlated with water supply pressure. Specifically, our results show that B. chinensis L. yield was increased 50% with NPI versus CK. Water supply pressure had a significant effect on N and P nutrient uptake and no significant effect on K. The average concentration of vitamin C was greatest with -5 kPa treatment and consecutively declined. According to our results, NPI can save up to 36.8% of water used and improve WUE by 61.3% during growth of B. chinensis L. Our results suggest that the optimum irrigation management strategy is -5 kPa treatment. CONCLUSION NPI versus CK can provide more stable irrigation water and retain soil moisture during plant growth, resulting in an increased WUE and yield with suitable water supply pressure. While our results suggest that NPI can enhance B. chinensis L. yield and perhaps also quality, future research should explore the mechanism of NPI in relation to yield and water use efficiency. © 2021 Society of Chemical Industry.

China has become the largest carbon-emitting country in the world since 2007. To achieve national environmental goals by 2030, the carbon emissions per unit of gross domestic product (GDP) will need to fall to 60-65% of 2005 levels. Such a dramatic decrease presents a challenge for a nation in adjusting its energy source and usage, but via monitoring of reductions, greater understanding can be gained of how carbon emitters are responding to national goals. We analyzed the change in carbon emissions from China's fossil energy consumption from population, per capita GDP, energy efficiency improvements and energy structure using a Kaya identity model and Logarithmic Mean Divisia Index (LMDI) factor decomposition method from 2006 to 2018. Results suggest that trends in carbon emissions from 2006 to 2018 can be broken down into four periods: a rapid increase period during 2006-2011, a slowdown increase period during 2011-2014, a consecutive decline period during 2014-2016 and a rebound during 2017-2018. Trends in carbon emissions were greatly affected by per capita GDP and energy efficiency. While per capita GDP increased carbon emissions, energy efficiency had a countering effect on carbon emissions. Our results suggests that China's measures in the past decade to reduce carbon emissions (i.e. carrying out carbon emissions trading on a fixed basis, readjusting the economic structure, optimizing the energy structure, improving energy efficiency and increasing forest carbon sinks) have helped to reduce carbon emissions. However, China should continue to actively respond to climate change while striving to achieve of economic sustainable development and social progress.

A deep understanding of root–soil–microbe interactions in response to drip irrigation can help optimize drip irrigation techniques and improve crop yield; however, relevant knowledge remains limited. In this study, field experiments were conducted for two consecutive years to investigate the effects of surface drip irrigation (DI), subsurface drip irrigation (SDI), and alternate drip irrigation (ADI) on root–soil–microbe interactions and tomato yield. The results showed that the soil moisture distribution uniformity in the root zone (0–60 cm depth) was reduced in the order SDI > DI > ADI. In the SDI treatment, the tomato root lengths were 4.83- and 3.94-fold higher than those in the DI and ADI treatments, respectively, and the relative abundances of Patescibacteria in the bacterial community and Blastocladiomycota in the fungal community were significantly elevated. In the ADI treatment, the root length was 1.23-fold higher than that in the DI treatment, and the relative abundance of Patescibacteria also increased significantly compared with that in the DI treatment. These changes led to distinct root–soil–microbe interactions. The most intensive positive root–soil–microbe interactions occurred in the SDI treatment, followed by the ADI and DI treatments. The differences in the root–soil–microbe interactions regulated tomato yield. The tomato yield in the SDI treatment was increased by 19.77% and 7.77% compared with that in the DI and ADI treatments, respectively. In the ADI treatment, the tomato yield was 24.09% higher than that in the DI treatment. Therefore, the different drip irrigation methods can regulate tomato yield by affecting root–soil–microbe interactions. The results provide a reference for the optimization of the drip irrigation mode to regulate root–soil–microbe interactions and increase tomato yield.

Soil magnetic parameters are increasingly being linked to climatic and environmental variation, and thus provide an useful information for tracking perturbations in terrestrial environments. Climat...

The study integrates surface and vertical distribution of magnetic susceptibility and heavy metal contents (Pb, Cu, Zn and Fe) to characterize the signature of vehicle pollutants in roadside soils at Linfen city, China. Sites with reforestation and without vegetation cover were investigated. The results showed that magnetic susceptibility and heavy metal contents were higher at the roadside without trees than in the reforest belt. The variations of magnetic susceptibility and heavy metal contents decreased both with distance and with depth. The maximum value was observed at 5–10 m away from the roadside edge. The vertical distribution in soil revealed accumulation of pollutants in 0–5 cm topsoils. The average contents were higher than the background values and in the order Fe (107.21 g kg−1), Zn (99.72 mg kg−1), Pb (90.99 mg kg−1), Cu (36.14 mg kg−1). Coarse multi domain grains were identified as the dominating magnetic particles. Multivariate statistical and SEM/EDX analyses suggested that the heavy metals derived from traffic sources. Trees act as efficient receptors and green barrier, which can reduce vehicle derived pollution.

The values of magnetic susceptibility and Cu, Zn, Ni, Pb, Cr, Cd concentrations of 70 topsoil samples were analyzed and assessed for soil contamination in the Linfen basin of China. The contamination factor (CF) and pollution load index (PLI) were used to assess the degree of heavy metal pollution. All heavy metal concentrations in the soil were greater than the background values of Shanxi agricultural soils. PLI values ranged from 1.27 to 2.18 indicating significant soil contamination. Principal component analyses and correlation analyses were adopted for data treatment to identify heavy metal sources. Cu, Zn, Ni, and Pb were responsible for 31.2% of the total variance suggesting that these elements mainly originated from agrochemistry and atmospheric deposition. A positive correlation of magnetic susceptibility with Cu and PLI were observed in cultivated soils. This study shows that magnetic susceptibility measurements can be used as a technique in which different types of soil pollution can be distinguished and can also be used to rapidly monitor anomalies in areas that might require expensive and time consuming detailed chemical analyses.

Identifying areas of environmental exposure potential for humans due to contaminated soils is an ever growing concern for cities with extensive industrial histories. We applied a Potential Ecological Risk Index (RI) to evaluate the contamination degree of hazardous elements in soils from Linfen, northern China. The city has experienced extensive industrial pollution over time and is home to ～676,500 people. We analyzed in 0–10 and 10–20 cm soil depth the spatial distribution, sources and potential ecological risks of heavy metals (Cr, Ni, Cu, Zn, As and Pb) across Linfen in order to derive a human exposure risk map. Results indicate that the mean urban topsoil concentrations of Ni, Zn, As and Pb were 36.24 mg·kg−1, 91.41 mg·kg−1, 15.20 mg·kg−1 and 28.12 mg·kg−1, respectively, and exceeded corresponding background values. The coefficient of variation of Cu, Zn and Pb was greater than 50%, suggesting high variation in urban area. Contamination factor indices for Ni, Zn, As and Pb were higher than 1 and suggests urban soils in Linfen are moderately contaminated. The calculated 47.1% integrated pollution load index was higher than 1 and suggests that half of the city has an increasing pollution risk. The spatial variability of the Pollution Load Index and Risk Index suggest moderately to strongly contaminated areas in the east and center areas of the city. Our data suggest that Ni, As and Pb have the potential for posing the greatest ecological risk at most city sites and likely originated from numerous sources (vehicular traffic, exhaust, coal combustion, metal manufacturing and other anthropogenic activities) given the disparate spatial pattern and elevated concentrations relative to native soil background values.

Via magnetic susceptibility and X-ray fluorescence spectrometry, we examined soil heavy metal contents across an abandoned steel and iron plant that has been in production for 50 years. Soil magnetic susceptibility and heavy metal contents similarly decreased with increasing distance from the plant's industrial, central area. Results indicate that the mean value of soil magnetic susceptibility was 2727 × 10−8 m3·kg−1 and the max peak was 100 m from the plant's center. Frequency dependent susceptibility values less than 2%, suggest the presence of coarse grains from industrial activities. A significant positive correlation occurs between magnetic susceptibility and Mn, Fe, Cu and Pb. Irregular-shaped and non-spherical aggregates are the main morphology of technogenic magnetic particles found in soil samples. Our results indicate that the North, Northeast and East sampling areas generally have the highest pollutants values and these directions correspond with prevailing wind directions at differing times of the year. Mapping the spatial distribution of metals could lead to high-resolution risk targeting areas for remediation and land use planning.

This study compared water-use efficiency (WUE) and nutrient absorption of Glebionis coronaria L. through emitters of ceramic tube (CT) and polyvinyl formal (PF) under negative pressure irrigation. Three (↓4 kPa, ↓8 kPa, ↓12 kPa) water-supply treatments and artificial watering (CK) with pot experiments were investigated. The results showed that soil water content ranged from 18.1 to 27.2% with CT and 18.5–27.6% with PF, respectively. A decrease of water supply pressure resulted in a gradual decrease of water supply, water consumption, and nitrogen content of Glebionis coronaria L., whereas the contents of phosphorus and potassium gradually increased. The soil water content, plant height, yield, nutrient uptake, and WUE of plants irrigated with the PF emitter were superior to those irrigated with the CT emitter. The best water supply model was a water supply pressure of ↓4 kPa during the early growth stage and ↓8 kPa in the middle and late stages. Thus, water supply pressure has significant effects on the growth and development, yield, WUE, and nutrient absorption of Crown Daisy.

Albedo is one of the import parameters for the routine applications of various remote sensing models, and most methods for estimating albedo are only applicable in plain areas with relatively flat topography. Due to the existence of the undulant terrain in mountain areas, the incoming radiance can be decomposed into beam, diffuse, and terrain radiance, which are affected by atmospheric transmittance, solar zenith and azimuth angles, terrain slope and aspect, etc. The existence of partial shadow in low-resolution pixel makes the calculation of albedo more complicated in the mountain areas. This paper presents a rapid and operational method for estimating albedo on complex terrain using high-resolution Digital Elevation Model (DEM) and MODerate-resolution Imaging Spectroradiometer (MODIS) data with sensor view angles less than 20°. Shadow coverage ratio of the low-resolution map was retrieved from high-resolution shadow map, and was used for the correction of beam radiance. The parameters used for the atmospheric correction of narrowband beam radiance and weighting coefficients for the calculation of broadband albedo using MODIS with and without band 5 were developed based on the SMARTS2 simulation under different atmospheric conditions. Taken the Taihang Mountain in the North China as the study area, the calculated reflectance and albedo were compared with the MODIS reflectance and albedo products. The maximum deviations between estimated and blue-sky albedos were −0.0155 and +0.0151 in plain areas, and −0.00667 and 0.01747 in the mountain areas, respectively. Good agreements indicate that the procedure presented in this paper is applicable for the albedo calculation in the mountain areas using MODIS images and high-resolution DEM.

Magnetic susceptibility is a non-conventional way that can be used for evaluating proxy soil heavy metals pollution. The paper monitors available heavy metals (Cu, Fe, Zn, and Mn) present in cultivated soils around ironsteel plant by soil magnetic susceptibility. Our study was located in an area with high pollution with small grid density of 250?m in China. Results showed that low field magnetic susceptibility was significantly correlated with available Cu, Zn, and Mn. No clear association exists between magnetic susceptibility and available Fe, soil organic matter, pH. Frequency dependent susceptibility >5% suggests the possible presence of super-paramagnetic particles, fly ashes produced during coal combustion.

Magnetic susceptibility can provide rich environmental information, especially for hazardous heavy metals and saline-alkaline in the contaminated soils. Magnetic susceptibility in four vertical profiles from saline-alkaline soils in lower Hai River basin was investigated. Soil sites were extended from alluvial fan to coastal plain areas. They are aligned along a latitudinal strip. Magnetic parameters including low/high frequency susceptibility, frequency-dependent susceptibility was measured. Moreover, some standard pedological parameters such as pH value and organic matter content were also determined. The results showed that low frequency magnetic susceptibility values is very high at the surface and decreases with the profile to a low value. In all profiles from alluvial fan frequency-dependent susceptibility greater than 3% may suggest the presence of relatively more super-paramagnetic particles. Magnetic susceptibility showed obvious vertical distribution in alluvial fan higher than coastal plain. No significant correlations between organic matter, pH and low frequency magnetic susceptibility were found, while there is a negative correlation between organic matter and frequency-dependent susceptibility. A positive correlation between pH and frequency-dependent susceptibility was found in the study areas.

The study evaluated eight heavy metals content and soil pollution from agricultural soils in northern China. Multivariate and geostatistical analysis approaches were used to determine the anthropogenic and natural contribution of soil heavy metal concentrations. Single pollution index and integrated pollution index could be used to evaluate soil heavy metal risk. The results show that the first factor explains 27.3% of the eight soil heavy metals with strong positive loadings on Cu, Zn, and Cd, which indicates that Cu, Zn, and Cd are associated with and controlled by anthropic activities. The average value of heavy metal is lower than the second grade standard values of soil environmental quality standards in China. Single pollution index is lower than 1, and the Nemerow integrated pollution index is 0.305, which means that study area has not been polluted. The semivariograms of soil heavy metal single pollution index fitted spherical and exponential models. The variable ratio of single pollution index showed moderately spatial dependence. Heavy metal contents showed relative safety in the study area.

Understanding spatial variability of hazardous soil heavy metals is an important precondition for suitably monitoring and evaluating eco-environment quality in the primary agricultural production zone. One hundred topsoils were sampled from the urban-rural transition zone in Taihang Piedmont Plain, China. The contents of eight heavy metals Cu, Zn, Cr, Ni, Pb, Cd, Hg and As were tested for each soil sample, and their spatial patterns were analyzed by the semivariogram approach of geostatistics and geographical information system (GIS) technology. Results showed that Cd concentration exceeded its background level. The local pollution from Cd attributed to the anthropogenic influence. The concentrations of eight hazardous heavy metals are relatively lower than the critical values of the national soil quality standard. The correlation distance of soil heavy metals ranged from 3.28 to 11.63 km, with the eight heavy metals having moderate spatial dependence. Cu, Cr, Ni, Pb and As are associated with and controlled by parent material. The results are helpful for improving agricultural and forest ecosystem in the and and semiarid region. (C) 2009 Elsevier B.V. All rights reserved.

The understanding of the spatial variability of soil heavy metals is an important precondition for suitably monitoring and evaluating eco-environment quality in a primary agricultural production zone. 100 topsoils were sampled from the Zhengding County of the urban-rural transition zone in Taihang Piedmont Plain, China. The contents of eight heavy metals Cu, Zn, Cr, Ni, Pb, Cd, Hg and As were tested for each soil sample, and their spatial patterns were analyzed by using the semivariogram approach of geostatistics, with which the kriging method was used to estimate the unobserved points. Then GIS technology was employed to produce spatial distribution maps of the 8 elements. The results showed that the concentration of Cd exceeded its background level. The local pollution from Cd was attributed to the anthropogenic influence. The concentrations of the eight heavy metals are relatively lower than the critical values of the national soil quality standard. The correlation distance of soil heavy metals ranged from 3.28 to 11.63 km, with the eight heavy metals having moderate spatial dependence. Cu, Cr, Ni, Pb and As were associated with and controlled by parent material. The spherical model was fitted to the semivariograms of Cu, Cr, Cd, Hg, Pb and As, and the Zn and Ni were fitted with the Gaussian model and the linear model, respectively. The results are helpful for improving agricultural and forest ecosystem in the region.