Carbon sequestration value of biosolids applied to soil: A global meta-analysis.

Biosolids produced at wastewater treatment facilities are extensively used in agricultural land and degraded mine sites to improve soil health and soil organic carbon (SOC) stocks. Many studies have reported increases in SOC due to application of biosolids to such sites. However, lack of a comprehensive quantification on overall trends and changes of magnitude in SOC remains. Here, we performed a meta-analysis to identify drivers with a relationship with SOC stocks. A meta-regression of 297 treatments found four variables with a relationship with SOC stocks: cumulative biosolids carbon (C) input rate, time after application, soil depth and type of biosolids. The cumulative biosolids C input rate was the most influencing driver. The highest mean difference for SOC% of 3.3 was observed at 0-15 cm soil depth for a cumulative C input of 100 Mg ha-1 at one year after biosolids application. Although years after biosolids application demonstrated a negative relationship with SOC stocks, mineralization of C in biosolids-applied soils is slow, as indicated with the SOC% decrease from 4.6 to 2.8 at 0-15 cm soil depth over five years of 100 Mg ha-1 biosolids C input. Soil depth illustrated a strong negative effect with SOC stocks decreasing by 2.7% at 0-15 cm soil depth at a cumulative biosolids C input of 100 Mg ha-1 over a year. Overall, our model estimated an effect of 2.8 SOC% change, indicating the application of biosolids as a viable strategy for soil C sequestration on a global scale.

Exogenous application of ß-sitosterol mediated growth and yield improvement in water-stressed wheat (Triticum aestivum) involves up-regulated antioxidant system.

Water stress reduces crop production significantly, and climate change has further aggravated the problem mainly in arid and semi-arid regions. This was the first study on the possible effects of ß-sitosterol application in ameliorating the deleterious changes in wheat induced by water stress under field condition and drip irrigation regimes. A field experiment with the split-plot design was conducted, and wheat plants were foliar sprayed with four ß-sitosterol (BBS) concentrations (0, 25, 75, and 100 mg L-1) and two irrigation regimes [50 and 100% of crop evapotranspiration (ETc)]. Water stress without BBS treatment reduced biological yield, grain yield, harvest index, and photosynthetic efficiency significantly by 28.9%, 42.8%, 19.6%, and 20.5% compared with the well-watered plants, respectively. Proline content increased in water-stressed and BSS-treated plants, owing to a significant role in cellular osmotic adjustment. Application of BSS was effective in reducing the generation of hydrogen peroxide (H2O2) and hence the malondialdehyde content significantly in water-stressed and well-watered wheat plants. Application of BSS up-regulated the activity of antioxidant enzymes (SOD, CAT, POD, and APX) significantly and increased the content of tocopherol, ascorbic acid, and carotene thereby reducing the levels of reactive oxygen species. The increased antioxidant system in BSS treated plants was further supported by the expression level of SOD and dehydrin genes in both water-stressed and well-watered plants. In the present study, the application of BBS at 100 mg L-1 was beneficial and can be recommended for improving the growth and yield of the wheat crop under water stress.

Plant pathogen nanodiagnostic techniques: forthcoming changes?

Plant diseases are among the major factors limiting crop productivity. A first step towards managing a plant disease under greenhouse and field conditions is to correctly identify the pathogen. Current technologies, such as quantitative polymerase chain reaction (Q-PCR), require a relatively large amount of target tissue and rely on multiple assays to accurately identify distinct plant pathogens. The common disadvantage of the traditional diagnostic methods is that they are time consuming and lack high sensitivity. Consequently, developing low-cost methods to improve the accuracy and rapidity of plant pathogens diagnosis is needed. Nanotechnology, nano particles and quantum dots (QDs) have emerged as essential tools for fast detection of a particular biological marker with extreme accuracy. Biosensor, QDs, nanostructured platforms, nanoimaging and nanopore DNA sequencing tools have the potential to raise sensitivity, specificity and speed of the pathogen detection, facilitate high-throughput analysis, and to be used for high-quality monitoring and crop protection. Furthermore, nanodiagnostic kit equipment can easily and quickly detect potential serious plant pathogens, allowing experts to help farmers in the prevention of epidemic diseases. The current review deals with the application of nanotechnology for quicker, more cost-effective and precise diagnostic procedures of plant diseases. Such an accurate technology may help to design a proper integrated disease management system which may modify crop environments to adversely affect crop pathogens.

Potential health risk assessment for heavy metals in Tilapia fish of different spatiotemporal monitoring patterns in Kafr El-Shaikh and El-Faiyum Governorates of Egypt.

Heavy metal (HMs) levels were evaluated in aquacultured tilapia fish collected from two highly producing districts in Egypt (Kafr El-Sheikh and El-Faiyum Governorates) during two seasons (autumn 2021 and spring 2022). As well, health risk assessment of exposure to HMs in tilapia fish was studied. The results revealed that six HMs: As, Cu, Fe, Mn, Cr and Zn were predominant in fish samples of the first season (autumn 2021), while most of HMs were existed in samples of the second season. All samples of the two seasons were free of Hg. Notably, autumn season's fish samples showed higher concentrations of HMs than those of the spring season. As well, Kafr El-Sheikh farms were highly contaminated with HMs than those of El-Faiyum governorate. Risk assessment results indicated that the THQ values of As substantially exceeded 1 either for Kafr El-Shaikh samples (3.15 ± 0.5) or for El-Faiyum samples (2.39 ± 0.8) of autumn season. Meanwhile, THQ values for all HMs, in spring season 2021, were less than one whole. These results indicated a potential health risk arising from the exposure to HMs, As in particular, in fish samples of autumn season as compared to those of spring season. Therefore, there is a need for remedial applications, in such polluted aquacultures in autumn season, which are currently under investigation as an integral part of the research project that funded the current study.

(Im)mobilization and speciation of lead under dynamic redox conditions in a contaminated soil amended with pine sawdust biochar.

Biochar can reduce the mobility and availability of potentially toxic elements (PTEs) in soils and improve soil properties. However, immobilization efficiencies of biochar can be varied according to environmental conditions, such as pH and redox potential (Eh), especially for soils under flood-dry cycles. In the current study, biochar produced at 300 and 550 °C (referred as BC300 and BC550, respectively) and its feedstock (pine sawdust biomass, BM) were used to amend a lead (Pb)-contaminated soil under pre-defined redox windows (from -300 to +250 mV). Key features of the soil-solution were evaluated in detail, including pH, dissolved organic carbon, sulphate, and dissolved Al, Fe, and Mn. The BC550 reduced the amount of dissolved Pb and showed a different pattern of Eh-pH in the soil slurry compared with BM and BC300. This might be attributed to its higher alkalinity and surface area. The highest amount of dissolved Pb was found at slightly anoxic conditions (-100 to 0 mV) in CS (control soil), S&BM (soil amended with BM), and S&BC300 (soil amended with BC300), which could be associated with the dissolution of Fe/Mn oxides. Moreover, the fitting results of Pb X-ray absorption fine structure (XAFS) indicated that the proportion of Pb(CH3COO)2 was decreasing when changing from anoxic to oxic condition in S&BC300, while the Pb speciation pattern in soil was stable in S&BC550. These results suggested that BC550 is more suitable amendment for Pb immobilization than BM and BC300 in this study. In addition, biochar produced at higher temperatures can be more stable so it can be suitable for remediation of Pb-contaminated soils which are frequently flooded.

Mobility and phytoavailability of As and Pb in a contaminated soil using pine sawdust biochar under systematic change of redox conditions.

Biochar has been adopted to control the mobility and phytoavailability of trace elements (TEs) in soils. To date, no attempt has been made to determine the mobility and phytoavailability of arsenic (As) and lead (Pb) in a contaminated soil with biochars as amendments under predefined redox potentials (EH). Thus, in this study, a soil contaminated with As and Pb (2047 and 1677 mg kg-1, respectively) was pre-incubated for 105 days with three amendments (pine sawdust biomass (BM) and two biochars produced from the same feedstock at 300 °C (BC300) and 550 °C (BC550)). The aged samples were then exposed to dynamic EH conditions to evaluate the mobility and phytoavailability of As and Pb after immobilization. The BM amendment significantly decreased and the BC300 slightly reduced the mobility and phytoavailability of As and Pb, which may be related to the oxygen-containing functional groups on the surface of BM and BC300. In contrast, BC550 increased the mobility of As at -300 to -100 mV and 100 mV, enhanced the phytoavailability of As under oxidizing condition (>100 mV), but reduced the phytoavailability of Pb, which might be caused by the properties of amendments and redox chemistry of the TEs. The effectiveness of BM and biochars for the stabilization of As and Pb varied under dynamic EH conditions, which indicates that detailed investigations should be conducted before the applications of biochar as soil amendment under variable environmental conditions, especially for contaminated paddy soils.

Soil pollution assessment and identification of hyperaccumulating plants in chromated copper arsenate (CCA) contaminated sites, Korea.

In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAF(shoots) and BAF(roots)) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg(-1), 27.78-120.83 mg kg(-1), and 0.13-9.43 mg kg(-1), respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg(-1)) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAF(shoot) (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAF(root) values>1 and TF values<1 were suitable; however, Typha orientalis was the best for Cr.