Effects of irrigation water quality on the presence of pharmaceutical and personal care products in topsoil and vegetables in greenhouses.

The presence of pharmaceutical and personal care products (PPCPs) in the environment has harmful effects on humans and the ecosystem. Reclaimed water irrigation may introduce PPCPs into the agricultural system. Here, a greenhouse experiment investigated the impact of reclaimed water irrigation on PPCP levels in the edible parts of vegetables and topsoil in the North China Plain in 2015 and 2016. Three treatment protocols were applied to each vegetable: irrigation with reclaimed water, irrigation with groundwater, and mixed irrigation with groundwater and reclaimed water (1:1, v/v). The total concentrations of 10 PPCPs in the topsoil (0-20 cm deep) and vegetables were 4.06-19.0 and 2.33-189 µg/kg, respectively. Among the target PPCPs, acetyl-sulfamethoxazole (AC-SMX) had the highest concentration in both soil and vegetables (0.23-10.8 and 1.56-116 µg/kg, respectively). The total concentration of the 10 PPCPs among cabbage, cauliflower, carrot, and cucumber were 13.1-28.1, 10.3-28.3, 2.33-4.04, and 110-189 µg/kg, respectively. The total hazard quotients for the mixture of target PPCPs across all vegetables were 0.0007 and 0.0003 for toddlers and adults, respectively. Compared with groundwater irrigation, reclaimed water irrigation did not evidently affect the vegetable yields, soil-vegetable PPCP concentrations, and BCFs. In this study, we found no potential hazard to human health when people consumed vegetables grown using reclaimed water irrigation.

Regional estimation of net anthropogenic nitrogen inputs (NANI) and the relationships with socioeconomic factors.

Human activities have strongly influenced nitrogen loads; thus, the accurate evaluation of net anthropogenic nitrogen input (NANI) is very important for developing countermeasures to control N pollution. The spatiotemporal distribution and main components of NANI at the city scale in Hubei Province in 2008-2018 were analyzed using the NANI model. Furthermore, the relationships between NANI and socioeconomic factors, namely, the gross industrial output value per unit area (GIOV), gross agricultural output value per unit area (GAOV), grain yield per unit area (GY), fertilizer consumption density (FCD), population density (PD), and cultivated land area per unit area (CLA), were further analyzed. The results show that NANI in Hubei tended to increase from 14,422.66 kg km-2 year-1 in 2008 to 16,779.39 kg km-2 year-1 in 2012 and then fell to 13,415.74 kg km-2 year-1 in 2018. In terms of the spatial distribution, the NANI values in the mid-east region of Hubei, i.e., Xiangyang, Jingmen, Jingzhou, Suizhou, Xiaogan, Wuhan, Ezhou, and Huanggang and counties directly under the jurisdiction of the province, were significantly higher than those in the west, i.e., Shiyan, Yichang, and Enshi autonomous prefecture. The largest 11-year annual NANI, 39,462.03 kg km-2 year-1, occurred in Ezhou, while Shiyan had the lowest 11-year annual NANI of 6592.32 kg km-2 year-1. N fertilizer use (Nfer), which accounted for 55.23% of the NANI was the largest N input source, followed by net N import in food and feed (Nim), atmospheric N deposition (Ndep), N fixation (Nfix), and seeding N (Nsee). Pearson correlation analysis between the components of NANI and 6 socioeconomic factors revealed FCD as the primary factor responsible for NANI (r = 0.948), followed by GAOV (r = 0.607) and CLA (r = 0.558). The most direct driving factors of Ndep, Nfer, Nsee, and Nim were GIOV (r = 0.727), FCD (r = 0.966), CLA (r = 0.813), and GAOV (r = 0.746), respectively. All factors had a significant negative impact on Nfix. Therefore, the most efficient strategy to decrease NANI is to control the fertilizer application amount and improve agricultural development. Additionally, it is necessary to replace traditional high-polluting industries with ecological industry to reduce industrial pollution. Graphical abstract.

Quantitative study on redistribution of nitrogen and phosphorus by wetland plants under different water quality conditions.

The application of wetland plants to purify surface rivers has gradually become an important means to control water pollution. However, there are many species of wetland plants which differ greatly in living conditions, water purification effects and pollutant migration paths. Therefore, it is necessary to select suitable wetland plants and quantitatively analyze the effects of different wetland plants on pollutant transport paths for the protection of water quality. In this research, the Typha orientalis C. Presl (T), Lemna minor L.(L) and Ceratophyllum demersum L.(C) were selected as typical wetland plants to conduct single-factor and multi-factor experiments under different water quality conditions. The results showed that wetland plants had significantly decreased nitrogen (N) and phosphorus (P) concentration in two sewage bodies. The NH4+-N and NO3--N removal efficiencies ranged from 71 to 96% and from 46% to 76%, and the PO43--P removal efficiencies ranged from 79% to 94% . The concentration of nutrient in the sewage decreased rapidly in the early stage and then tended to reach a stable state. The total nitrogen (TN) removal efficiencies under two kinds of sewage ranked as follows: T+L+C>T>C>L. Under high concentration sewage, the TN removal efficiencies by wetland plants mostly attributed to the change in the microbial status of the water body, which ranged from 82% to 95%. Under low concentration sewage, the combination of wetland plants could optimize the purification effect of plant consumption and microbial decomposition, and the TN removal efficiencies ranged from 75% to 95%. The total phosphorus (TP) removal efficiencies of T and T+L+C were better in two concentration sewages. The research demonstrated that P in sewage was mainly accumulated in soil matrix and it was important to select the emergent plants with well-develoed roots and vigorous growth to purify sewage.

Mathematical model of ammonium nitrogen transport with overland flow on a slope after polyacrylamide application.

The nutrient loss caused by soil erosion is the main reason for soil degradation and environmental pollution, and polyacrylamide (PAM) as a common soil amendment has a great influence on runoff and erosion processes at the slope. In order to investigate the mechanism of nutrient transport with runoff, a field experiment was conducted and a simple mathematical model was developed in this study. Four PAM application rates (0, 1, 2, and 4 g·m-2) and two rainfall intensities (50 and 80 mm·h-1) were applied in the field experiment. The results revealed that runoff rate of 2 g·m-2 PAM application treatments decreased by 5.3%-10.6% compared with the control groups, but it increased by10.9%-18.7% at 4 g·m-2 PAM application treatments. Polyacrylamide application reduced ammonium nitrogen concentrations of runoff by 10.0% to 44.3% relative to the control groups. The best performance with correlation coefficient (R2) and Nash-Sutcliffe efficiency (NSE) showed that the ammonium transport with runoff could be well described by the proposed model. Furthermore, the model parameter of the depth of the mixing layer (hm) linearly increased with an increase in flow velocity, but exponentially decreased with an increase in PAM application rate.