Sewage is widely used on agricultural soils in peri-urban areas of developing countries to meet shortages of water resource. Although sewage is a good source of plant nutrients, it also increases the heavy metals loads to soils. Microbial responses to these contaminants may serve as early warning indicators of adverse effects of sewage irrigation on soil quality. The purpose of this study was to assess the effect of time of sewage irrigation on soil microbial indicators. Soil samples were collected from seven soil sites (S1-S7) irrigated with 0 years, 16 years, 23 years, 25 years, 27 years, 32 years and 52 years, respectively in Shijiazhuang of China and analyzed. For each soil sample, we determined the quantities of bacteria, fungi and actinomycete, and enzyme activities of urease, sucrase, phosphatase, dehydrogenase and catalase. Our results showed that the soils of S2-S7 irrigated with sewage effluents for different times (ranged between 16 and 52 years) exhibited higher densities of bacteria, actinomycete, urease, sucrase and phosphatase but lower densities of fungi when compared with S1 irrigated with sewage effluents for 0 years. The soil S7 irrigated with sewage effluents for longest times (52 years) contained lowest activities of catalase when compared with the soils of S1-S6. The densities of bacteria (R = 0.877, p < 0.01), actinomycete (R = 0.875, p < 0.01), sucrase (R = 0.858, p < 0.01) and phosphatase (R = 0.804, p < 0.05) were significantly correlated in a positive manner with time of sewage irrigation. Soil fungi quantities and urease, dehydrogenase and catalase activities did not change significantly with irrigation time. This study confirms that sewage irrigation had negative effects on microbial properties including fungi, catalase and dehydrogenase in the long term, so there is a need for continuous monitoring for sustainable soil health.
The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed.
The objective of this research is to study the efficiency of acclimating the Tapumei Series red clay collected from Ming-Tou, Na-Tou in central Taiwan by using the calcium-rich by-product recovered from the CFB (Circulation Fluidized-Bed Boiler) de-sulfur operation. At the end of the testing period, the samples were dried, sieved and analyzed for pH, exchangeable calcium, magnesium, potassium, and sodium, and aluminum. The plant growth was observed for 7 weeks in order to investigate the influence of soil improvement on the growth and production of corn. The results reveal that all samples show an initial sharp increase from 3 to 7.5, 8.1, 8.4 and 8.6 for samples added with 18, 27, 36 and 45 tons/hectare of lime, respectively, and the final pH values after 6 months were 6.5, 7.2, 7.6 and 7.9, respectively. The lime treatment increases the soil exchangeable anion concentrations and reduces the aluminum ion concentration. This is because that the recovered CBF by-product is rich in CaO that neutralizes the soil H+ and raises the soil pH. Additionally, the anions contained in the by-product will also enhance the soil nutrients and lower the solubility of aluminum.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.