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The presence of excessive algae in water is always considered as a negative factor in irrigation. However, the optimal balance between algal removal and retention in irrigation water when the algal biomass is controllable remains unknown. Therefore, this study explores the impact of low-level algal presence (Scytonema javanicum) on soil and microbial activity through controlled soil column experiments. Soil moisture was measured, and 16S rRNA gene amplicons sequencing was applied to characterize the microbial community. Slight community changes indicated no negative impact on the local microbial community of S. javanicum. Enzyme assays and quantitative polymerase chain reaction (qPCR) revealed that algae improved soil moisture retention, and enhanced the nutrient content of the topsoil. The decrease in moisture in the treatment group (from 27.53% to 26.42%) was significantly reduced (p < 0.05) compared to the control (from 27.55% to 25.17%), while the contents of ammonium (NH3-N) and total nitrogen (TN) in the treatment (0.70 mg/kg and 0.54 g/kg) were also higher (p < 0.05) than that of the control (0.43 mg/kg and 0.49 g/kg). The results of the abundance of functional gene suggested algae facilitated nitrogen fixation and nitrification. This research offers innovative insights for diversifying the sources of irrigation water. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the current status of soil fertility in the long-term wastewater-irrigated agricultural areas of Beiyechang District in the suburb of Beijing. A total of 103 soil samples from the top 20 cm of soil layer were collected and analyzed for macro- and micronutrient elements. The mean values of these elements were: total nitrogen (TN), 0.08 ± 0.02%; available nitrogen (AN), 60.34 ± 10.08 mg/kg; available phosphorus (AP), 19.59 ± 9.75 mg/kg; available potassium (AK), 84.22 ± 19.66 mg/kg; and availabilities of trace elements (B, Cu, Fe, Mn, Mo, and Zn), 0.29 ± 0.12, 1.44 ± 0.34, 8.97 ± 2.05, 5.44 ± 0.95, 0.27 ± 0.16, 1.16 ± 0.42 mg/kg, respectively. Compared with other similar areas, the overall soil nutrient content in the study area was still at a low level after nearly 30 years of wastewater irrigation. The organic matter content of wastewater-irrigated soils has significant impact on the accumulation of nutrient elements in these soils. Geostatistical analyses suggested that the spatial distribution of TN and AP was on account of agricultural practices, such as wastewater irrigation and fertilizer use. The availability of P, Mo, Cu and Zn may be due to the joint effect of soil parent material and wastewater irrigation. The availability of K, Fe and Mn was attributed to soil parent material. A significant availability of some elements occurred around sewage outfalls in the irrigation area and water canals, where the wastewater could be easily lifted. The knowledge of spatial distribution and sources of soil nutrients in such areas is the basis for undertaking appropriate farming and irrigation activities with rationalized utilization of treated wastewater. [ABSTRACT FROM AUTHOR]

Reclaimed water reuse is an effective method of alleviating agricultural water shortages, which entails some potential risks for groundwater. In this study, the impacts of wastewater reuse on groundwater were evaluated by combination of groundwater chemistry and isotopes. In reclaimed water infiltration, salt composition was affected not only by ion exchange and dissolution equilibrium but also by carbonic acid equilibrium. The dissolution and precipitation of calcites and dolomites as well as exchange and adsorption between Na and Ca/Mg were simultaneous, leading to significant changes in Na/Cl, (Ca + Mg)/Cl, electrical conductivity (EC) and sodium adsorption ratio (SAR). The reclaimed water was of the Na-Mg-Ca-HCO 3 -Cl type, and groundwater recharged by reclaimed water was of the Na-Mg-HCO 3 and Mg-Na-HCO 3 types. The hydrogeological conditions characterized by sand-clay alternation led to both total nitrogen (TN) and total phosphorus (TP) removal efficiencies > 95%, and there was no significant difference in those contents between aquifers recharged by precipitation and reclamation water. > 40 years of long-term infiltration and recharge from sewage and reclaimed water did not cause groundwater contamination by nitrogen, phosphorus and heavy metals. These results indicate that characteristics of the study area, such as the lithologic structure with sand-clay alternation, relatively thick clay layer, and relatively large groundwater depth have a significant role in the high vulnerability. [ABSTRACT FROM AUTHOR]

Seen as a solution to water shortages, wastewater reuse for crop irrigation does however poses a risk owing to the potential release of organic contaminants into soil and water. The frequency of detection (FOD), concentration, and migration of nonylphenol (NP) isomers in reclaimed water (FOD RW ), surface water (FOD SW ), and groundwater (FOD GW ) were investigated in a long-term wastewater irrigation area in Beijing. The FOD RW , FOD SW and FOD GW of any or all of 12 NP isomers were 66.7% to 100%, 76.9% to 100% and 13.3% to 60%, respectively. The mean (± standard deviation) NP concentrations of the reclaimed water, surface water, and groundwater (NP RW , NP SW , NP GW , repectively) were 469.4 ± 73.4 ng L − 1 , 694.6 ± 248.7 ng − 1 and 244.4 ± 230.8 ng − 1 , respectively. The existence of external pollution sources during water transmission and distribution resulted in NP SW exceeding NP RW . NP distribution in groundwater was related to the duration and quantity of wastewater irrigation, the sources of aquifer recharge, and was seen to decrease with increasing aquifer depth. Higher riverside infiltration rate nearby leads to higher FOD GW values. The migration rate of NP isomers was classified as high, moderate or low. [ABSTRACT FROM AUTHOR]

Reclaimed water is an important water resource to alleviate the agricultural water crisis around the world. Meanwhile, the environmental behavior of emerging contaminants and the impact on soil microorganisms during the reuse of recycled water have attracted wide attention. In this study, the content of trimethoprim and sulfamethoxazole in the 0–120 cm soil irrigated with reclaimed water increased by 42% and 61%, respectively, compared with the soil irrigated with groundwater water. Trimethoprim and sulfamethoxazole both showed a downward migration trend after 12 years of irrigation with reclaimed water. The reclaimed irrigation resulted in the peak concentration of trimethoprim and sulfamethoxazole at the depth of 0–120 cm soil increased to 2.3 and 1.8 times of the control, while no significant change on the concentration of triclosan in soil was found. The three types of pharmaceuticals and personal care products showed significant increase in the surface soil from 0 to 40 cm. The total bacterial abundance significantly increased by 16% after irrigation with reclaimed water, but there was no significant effect on the total archaea abundance (p > 0.05). The correlation results showed high negative associations between the rate of variation of soil pharmaceuticals and personal care products and the total number of bacteria (p < 0.05), in which the increase of soil pharmaceuticals and personal care products concentration under irrigation with reclaimed water would reduce the soil microbial abundance. This study will help us understand the fate of three chemical components in soil with long term irrigation with reclaimed water and their effects on soil microorganisms. • Reclaimed water irrigation led the increase of SXT and TMP. • SXT and TMP both showed downward migration characteristics in soil. • The impact of reclaimed water irrigation on TBA was higher than TAA. • Soil microorganisms had a significant positive correlation with TC and TN. • There was a significant negative correlation between CV TAA and CV TA. [ABSTRACT FROM AUTHOR]