[Effect of Biochar on Ammonia Volatilization in Saline-Alkali Soil].

In order to investigate the effect of biochar on NH3 volatilization in saline-alkali soils of the Yellow River Delta, continuous laboratory incubation was conducted. Firstly, the recovery rate of NH3 volatilization by an improved aeration method was determined, the effects of fertilizer particles and aqueous fertilizer solution on NH3 volatilization were then compared. Finally, the effects of biochar species, application amount, and fertilizer type on NH3 volatilization rate and total amount were explored. The results showed that the average recovery rate of NH3 reached 100.30% using ammonium sulfate as the nitrogen source. With the same rate of nitrogen application, the volatilization of NH3 decreased by 60.29% in the treatment with urea as the aqueous solution compared to the treatment with urea particles, and decreased by 61.40% in the treatment with an ammonium sulfate aqueous solution compared to the treatment with ammonium sulfate particles. Compared with the control treatment (without the addition of biochar and with the addition of ammonium sulfate solution), the addition of 0.5% biochar derived from 300℃ rice biochar (RB-300), 600℃ rice biochar (RB-600), 300℃ cotton biochar (CB-300), and 600℃ cotton biochar (CB-600) reduced the total volatilization of NH3 by 18.68%, 16.16%, 9.35%, and 8.26% respectively. The volatilization rate of NH3 was at its highest within two days of fertilization, which accounted for 53.80%-64.02% of the total volatilization. After the addition of the biochar, volatilization of NH3 decreased at first and then increased in proportion to an increase in biochar content. Therefore, adding a small amount of biochar before field fertilization, combined with the integrated management of water and fertilizer, can effectively reduce NH3 volatilization and improve nitrogen use efficiency.

Transcriptome profiling reveals the genetic basis of alkalinity tolerance in wheat.

BACKGROUND: Soil alkalinity shows significant constraints to crop productivity; however, much less attention has been paid to analyze the effect of soil alkalinity on plant growth and development. Shanrong No. 4 (SR4) is an alkalinity tolerant bread wheat cultivar selected from an asymmetric somatic hybridization between the bread wheat cultivar Jinan 177 (JN177) and tall wheatgrass (Thinopyrum ponticum), which is a suitable material for studying alkalinity tolerant associate genes. RESULTS: The growth of SR4 plant seedlings was less inhibited than that of JN177 when exposed to alkalinity stress conditions. The root cytosolic Na+/K+ ratio in alkalinity stressed SR4 was lower than in JN177, while alkalinity stressed SR4 contained higher level of nutrient elements than in JN177. SR4 plant seedlings accumulated less malondialdehyde (MDA) and reactive oxygen species (ROS), it also showed higher activity of ROS scavenging enzymes than JN177 under alkalinity stress. The root intracellular pH decreased in both alkalinity stressed JN177 and SR4, however, it was much lower in SR4 than in JN177 under alkalinity stress. The transcriptomes of SR4 and JN177 seedlings exposed to alkalinity stress were analyzed by digital gene expression tag profiling method. Alkalinity stress conditions up- and down-regulated a large number of genes in the seedling roots that play the functions in the categories of transcription regulation, signal transduction and protein modification. CONCLUSIONS: SR4 expresses a superior tolerance to alkaline stress conditions which is due to its strong absorbing ability for nutrient ions, a strong regulating ability for intracellular and rhizosphere pH and a more active ROS scavenging ability.

Health risk to residents and stimulation to inherent bacteria of various heavy metals in soil.

The toxicities and effects of various metals and metalloids would be misunderstood by health risks based on their concentrations, when their effects on bacterial and ecological functions in soil are disregarded. This study investigated the concentrations and health risks of heavy metals, soil properties, and bacterial 16S rRNA gene in soil around the largest fresh water lake in North China. The health risks posed by Mn and As were higher than those of other heavy metals and metalloids. Mn, As, and C were significantly correlated with the bacterial species richness indices. According to canonical correspondence analysis, species richness was mainly affected by Mn, Pb, As, and organic matter, while species evenness was mainly affected by Mn, pH, N, C, Cd, and Pb. Covariable analysis confirmed that most effects of metals on bacterial diversity were attributed to the combined effects of metals and soil properties rather than single metals. Most bacteria detected in (almost) all soil were identified as Gammaproteobacteria. Specific bacteria belonging to Proteobacteria (Gamma, Alpha, Epsilon, and Beta), Firmicutes, Actinobacteria, Cyanobacterium, Nitrospirae, and Fusobacterium were only identified in soil with high concentrations of Mn, Pb, and As, indicating their remediation potency. Bacterial abilities and mechanisms in pollutant resistance and element cycling in the region were also discussed.

Effects of pollution sources and soil properties on distribution of polycyclic aromatic hydrocarbons and risk assessment.

In this study, the concentrations of polycyclic aromatic hydrocarbons (PAHs) in soil profiles and the soil properties were analyzed in Hunpu, a typical wastewater irrigation area, northeast of China. The total concentrations of 16 priority control PAHs ranged from 7.88 to 2,231.42 µg/kg. Among 16 PAHs, the most abundant was Phenanthrene and the 3- or 4- ring PAHs were predominant. The PAH concentrations were higher in the upland fields near the oil wells, whereas leaching of PAH into the groundwater caused low concentrations in the paddy fields. The geochemical indices and the results from the principal component analysis of all 16 PAHs indicated that PAHs were mainly from atmospheric dusts in the top soil in I-1P/I-3P/I-7P and through soil profiles in I-4U/I-5P/I-8U, whereas those in the bottom layers were mainly from petroleum production and wastewater irrigation in I-1P/I-3P/I-7P and through soil profiles in I-2U and I-6U. In the redundancy analysis, PAHs exhibited negative correlation with pH, depth, silt, and clay, but had positive correlation with sand and organic matter. Finally, total toxic equivalent in the soil profiles and the calculated health risk of PAHs in the surface soil using contaminated land exposure assessment model elucidated the cancer risk that PAHs pose on human health in the Hunpu region.

Contamination, source, and input route of polycyclic aromatic hydrocarbons in historic wastewater-irrigated agricultural soils.

Contamination by polycyclic aromatic hydrocarbons (PAHs) of historic wastewater-irrigated agricultural topsoil (0-5 cm) and the contribution of groundwater irrigation and atmospheric deposition to soil PAHs were studied in a typical agricultural region, i.e. Hunpu region, Liaoning, China. Concentrations of total PAHs ranged from 0.43 to 2.64 mg kg⁻¹ in topsoil, being lower than those found in other wastewater-irrigated areas. The levels of PAHs in soil declined as the distance from a water source increased. Concentrations of individual PAHs were generally higher in upland than in paddy topsoils. The calculated nemerow composite index showed that agricultural soil in the region was "polluted" by PAHs. A human health risk assessment based on the total toxic equivalent concentration showed that the presence of elevated concentrations of PAHs in the soil might pose a great threat to the health of local residents. Ratios of pairs of PAHs and principal component analysis (PCA) showed that pyrogenesis, such as coal combustion, was the main source of PAHs, while petroleum, to some extent, also had a strong influence on PAHs contamination in upland soil. The distribution patterns of individual PAHs and composition of PAHs differed between irrigation groundwater and topsoil, but were similar between atmospheric deposition and topsoil. There were significant linear correlations (r = 0.90; p < 0.01) between atmospheric deposition rates and average concentrations of the 16 individual PAHs in soils, while no significant relationships were observed between irrigation groundwater and topsoil in levels of PAHs. These suggested that PAHs in agricultural soils were mainly introduced from atmospheric deposition, rather than from groundwater irrigation after the phasing out of wastewater irrigation in the region since 2002. This study provides a reference to ensure agricultural product safety, pollution control, and proper soil management.

[Soil environmental background concentrations in old course of the Yellow River in Shandong Province].

The environmental background concentrations of soil heavy metals, HCH, DDT and organic matter in old course of the Yellow River (Shandong area) were studied. Heavy metals vertical distribution, correlative analysis between organic matter and heavy metals, and the effect of different land use types were analyzed. The results showed that the background concentrations were 13.46 mg x kg(-1) for Cu, 16.23 mg x kg(-1) for Pb, 42.31 mg x kg(-1) for Zn, 30.97 mg x kg(-1) for Cr, 0.090 mg x kg(-1) for Hg, 3.90 mg x kg(-1) for As, 8.01 mg x kg(-1) for Co, 36.42 mg x kg(-1) for V, 426.83 mg x kg(-1) for Mn, 0.063 mg x kg(-1) for Cd, 18.71 mg x kg(-1) for Ni, and 0.74% for organic matter respectively. The detection rates of HCH and DDT were 100% and 60% respectively, and their concentrations were lower than Grade II of environmental quality standard for soils. All the heavy metals in soils were lower than Grade I of environmental quality standard for soils, and were lower than the background concentrations in the whole country, Shandong Province and the Loess Plateau area except for Hg. Mercury was significantly enriched in the surface soil, and the concentration of Cd was higher in the sublayer soil. The differences were significant between the layer 0-20 cm and 20-40 cm for Hg, Cd and organic matter, but not for the other heavy metals. The differences were not significant for environmental background concentrations among different land use types. Organic matter had highly positive correlations with Cu, As, Mn, Pb, Zn, Cr, Co and Ni.

Selecting iodine-enriched vegetables and the residual effect of iodate application to soil.

A greenhouse pot experiment was conducted to select vegetables for iodine uptake. The residual effect of iodate fertilization on the growth of and iodine uptake by spinach plants were also investigated. Six vegetables, including leafy vegetables (pakchoi [Brassica chinensis L.], spinach [Spinacia oleracea L.]), tuber vegetables (onion [Allium cepa L.]), shoot vegetables (water spinach [Ipomoea aquatica Forsk.], celery [Apium graveolens L.]), and root vegetables (carrot [Daucus carota var. sativa DC.]) were examined. Results showed that the concentrations of iodate in soil had significant effect on the biomass of edible parts of pakchoi and spinach (p<0.01), whereas the concentrations of iodate in soil had no significant effect on that of carrots, water spinach, celery, and onion. Iodine concentrations in edible parts of vegetables and the transfer factors (TFedible parts) of soil-to-edible parts of vegetables significantly increased with increasing iodine concentrations in soil (p<0.001), and iodine concentrations in edible parts and TFedible parts of spinach were much higher than those of other vegetables at any treatment. Both transfer coefficients for edible parts (TCedible parts) and for aerial parts (TCaerial parts) of vegetables changed differently with increasing iodine concentrations in the soil, and TCedible parts and TCaerial parts of spinach were higher than those of other vegetables. Therefore, spinach was considered as an efficient vegetable for iodine biofortification. Further experiment showed that there is considerable residual effect of soil fertilization with iodate.

Adsorption and desorption of iodine by various Chinese soils: I. Iodate.

In order to assess the adsorption of iodate by different soils from China, a series of batch experiments were conducted. It was found that soils rich in iron oxide had high affinity for iodate. Iodate adsorption isotherms could be well fitted with both Langmuir and Freundlich equations. Iodate adsorption by 20 different soils from China revealed that iodate adsorption was significantly correlated with soil organic matter negatively and positively with free iron oxide contents. At initial concentration of 4 mg I L(-1), iodate adsorption ranged between 9 and 34 mg kg(-1) soil. No correlation between iodate adsorption and cation exchange capacity and soil pH was found. For a single soil, there was a significant linear relationship between the amounts of iodate adsorbed and desorbed, but for a group of different soils, the relationship between the amounts of iodate adsorption and desorption followed a nonlinear relationship, the deviation mainly occurred at high adsorption side. The relationship between K(d) and free aluminum oxide and free iron oxide contents showed an exponential relationship for various soils with exception of the soil from Hetian in Xinjiang.