Organophosphate esters in rural wastewater along the Yangtze river Basin: Occurrence, removal efficiency and environmental implications.

Organophosphate esters (OPEs) discharged from rural domestic wastewater were one of the important sources of OPEs in receiving water bodies, which has posed a potential threat to the ecological environment. However, very little information on the characteristics of OPEs in the rural domestic wastewater is available. Herein, the occurrence, removal efficiency and environmental implication of OPEs in rural domestic wastewater treatment facilities (RD-WWTFs) along the Yangtze River Basin were investigated. Results indicated that the median concentrations of ΣAlkyl-OPEs, ΣHalogenated-OPEs, ΣAryl-OPEs and the total OPE (ΣOPEs) in influents were 28.28, 99.25, 10.22 and 136.84 ng/L, while the median concentrations of them in effluents were 25.80, 141.86, 7.98 and 173.31 ng/L, respectively. Undoubtedly, halogenated OPEs were the most abundant in both influent and effluent, followed by alkyl and aryl OPEs, and they accounted for average proportions of 69.50%, 19.96%and 10.54% for influents, and 78.16%, 16.14%and 5.71% for effluents, respectively. Specifically, tris(2-chloroisopropyl) phosphate (TCPP, median: 55.17 ng/L in influents and 85.75 ng/L in effluents) was the dominant contributor to the ΣOPEs concentrations with average proportions of 37.75% and 47.33% for influents and effluents, respectively. Moreover, the concentration ranks for most OPEs except for aryl OPEs from high to low were upper reaches > lower reaches > middle reaches. However, negative values of tris(2-chloroethyl)phosphate (TCEP, -32.4%), TCPP (-55.4%) and tris(1,3-dichloroisopropyl) phosphate (TDCPP, -26.3%) were observed. The removal rates of alkyl OPEs (10-20%) and aryl OPEs (20-30%) were also not sufficient. Ecological risk values of ΣOPEs showed that there were 2.44% of high risk, 31.7% of moderate risk and 41.5% of low risk for effluents; while 0.00%, 48.8% and 46.3% were exhibited in high, moderate and low risk for influents, indicating that very slight reduction in risk was achieved by the RD-WWTFs.

Occurrence and removal of conventional pollutants, estrogenicities, and fecal coliform in village sewage treatment plants along the Yangtze River, China.

The present study investigated the occurrence and removal efficiency of some conventional pollutants, estrogenic effects, and fecal coliform in influents and/or effluents of village sewage treatment plants (STPs) in the upper, middle, and lower reaches of the Yangtze River Basin. The water quality of sewage from the village STPs showed significant seasonal and spatial variability. The removal rates of conventional pollutants by the village STPs were mostly lower than urban STPs, thereby resulting in that the water quality compliance rate of the effluents was only 33.3%. In addition, the average removal rate of estrogenic compounds was only 22.2%, which caused the estrogenicity of effluent to exceed the safety threshold. And E2 was determined to be the main estrogenic component. Moreover, ultraviolet (UV) disinfection, as the main disinfection treatment process of sewage along the Yangtze River Basin, was unable to meet the discharge standard of fecal coliform. The sequential chlorine (10 mg L-1)-UV (20 mJ cm-2) disinfection was found to both achieve up-to-standard discharge of fecal coliform and increase the removal rate of estrogenic effect from 3.78 to 9.86%. Overall, the present study provides valuable information on the conventional pollutants, estrogenic effects, and fecal coliform in sewage from village STPs along the Yangtze River Basin, and practical suggestions for basin-wide pollution control.

Effects of soil compaction on plant growth, nutrient absorption, and root respiration in soybean seedlings.

Soil compaction is a major environmental problem that affects plant growth and development. In this study, to further our understanding of its negative effects on plant growth, we investigated the effects of soil compaction on the growth, mineral absorption, and activities of key respiratory enzymes in soybean seedlings. We found that moderate-level soil compaction increased the activities of pyruvate kinase and phosphofructokinase in soybean seedling roots, enhancing the accumulation of P, K, Mg, Ca, and other elements. These accumulated elements, particularly Ca, increased the number of fibrous upper roots, but reduced root length and inhibited plant growth. High-level soil compaction inhibited the accumulation of P, K, Mg, Mn, Fe, Cu, and Zn and increased the accumulation of Ca via decreasing the activities of isocitrate dehydrogenase and cytochrome c oxidase. These effects led to a decreased root cell size, blurred root cell boundaries, and the inhibition of plant growth. Taken together, our results provide a new insight into the mechanisms by which soil compaction inhibits plant growth.

Effects of elevated ultraviolet-B radiation on root growth and chemical signaling molecules in plants.

Ozone layer depletion leads to elevated ultraviolet-B (UV-B) radiation, which affects plant growth; however, little is known about the relationship between root growth and signaling molecules in roots. Therefore, in this work, simulated UV-B radiation was used to study the effects of elevated UV-B radiation on root growth of soybean seedlings and changes in the content of signaling molecules in roots. The results showed that compared with the control, the 2.63 kJ m-2 d-1 and 6.17 kJ m-2 d-1 elevated UV-B radiation treatments inhibited root growth, and root growth parameters (total root length, root surface area, root volume, average diameter, root tip number, and root dry weight) all decreased. For root signaling molecules, the content of nitric oxide, reactive oxygen species, abscisic acid, salicylic acid, and jasmonic acid increased, and the content of auxin, cytokinin, and gibberellin decreased. The above indices changed more significantly under the 6.17 kJ m-2 d-1 treatment. After withdrawal of the exposure, the above indices could be restored to a certain extent. These data indicated that UV-B radiation interfered with root growth by affecting the content of signaling molecules in roots, and the degree of the effects was related to the intensity of UV-B radiation. The results from this study provide a theoretical basis for studying the preliminary mechanism of elevated UV-B radiation on root growth and possible pathways that can mitigate UV-B radiation damage for root growth. ONE SENTENCE SUMMARY: The effects of elevated UV-B on root growth of soybean seedlings were regulated by signaling molecules, and the degree of the effects was related to the intensity of UV-B radiation.

Analysis for effects of lanthanum (III) on the aboveground modules and respiration of soybean populations.

The accumulation of rare earth elements (REEs) in the environment has become an environmental safety issue that cannot be ignored. However, previous studies on the environmental risks of REEs have mostly been performed at the individual level. In this work, to explore the effects of REE pollution at the population level, the effects of lanthanum (III) [La(III)] on the aboveground modules of soybean (Glycine max L) populations at different planting densities were investigated by simulating La(III) pollution, and the underlying mechanism was revealed on the physiological and biochemical levels of respiration. The results showed that the addition of 0.4 and 1.2 mM La(III) decreased the aboveground module growth parameters of the soybean populations, and this effect was more evident in the 1.2 mM La(III) treatment. At a certain dose of La(III), the effects of La(III) on the aboveground module growth parameters decreased with increasing plant densities. In addition, the effects of La(III) on the aboveground module growth parameters of soybean plants at different planting densities were related to plant respiration, in particular, to changes in the activities of respiratory key enzymes. The results indicated that the inhibitory effects of La(III) depended on the dose and on the planting density. This finding could provide a novel perspective and a basis for the objective assessment of potential environmental risks of REEs. ONE SENTENCE SUMMARY: La(III) pollution effects on the aboveground modules of soybean populations are related to the changes of the population respiration and the respiratory key enzymes; moreover, these effects are restricted by the population density.