Screen time and mental health in college students: Time in nature as a protective factor.

Objective: To examine how time spent on handheld screens was related to internalizing mental health symptoms in college students and whether time spent in nature was associated with fewer mental health symptoms. Participants: Three hundred seventy-two college students (Mage = 19.47 ± 1.74, 63.8% female; 62.8% college freshman). Methods: College students completed questionnaires for research credit in their psychology courses. Results: Screen time significantly predicted higher anxiety, depression, and stress. Spending time outdoors ("green time") significantly predicted lower stress and depression, but not lower anxiety. Green time moderated the relationship, such that college students who spent less time outside (1SD below mean) had consistent rates of mental health symptoms across hours of screentime, but individuals who spent average/above average (mean, 1SD above mean) time outside had fewer mental health symptoms at lower levels of screentime. Conclusions: Promoting green time in students may be an effective way of improving stress and depression.

Method development for the analysis of ionophore antimicrobials in dairy manure to assess removal within a membrane-based treatment system.

Ionophore antimicrobials are heavily used in the livestock industries, both for preventing animal infection by coccidia protozoa and for increasing feed efficiency. Ionophores are excreted mostly unmetabolized and are released into the environment when manure is land-applied to fertilize croplands. Here, an analytical method was optimized to study the occurrences of five ionophore residues (monensin, lasalocid, maduramycin, salinomycin, and narasin) in dairy manure after solid-liquid separation and further treatment of the liquid manure by a membrane-based treatment system. Ionophore residues from the separated solid manure (dewatered manure) and suspended solids of manure slurry samples were extracted using ultrasonication with methanol, followed by sample clean-up using solid phase extraction (SPE) and subsequent analysis via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The use of an ethyl acetate and methanol (1:1 v:v) mixture as an SPE eluent resulted in higher recoveries and lower method quantitation limits (MQL), when compared to using methanol. Overall recoveries from separated solid manure ranged from 73 to 134%. Liquid manure fractions were diluted with Nanopure™ water and cleaned up using SPE, where recoveries ranged from 51 to 100%. The developed extraction and LC-MS/MS methods were applied to analyze dairy manure samples subjected to an advanced manure treatment process involving a membrane-based filtration step (reverse osmosis). Monensin and lasalocid were detected at higher concentrations in the suspended solid fractions (4.40-420 ng/g for lasalocid and 85-1950 ng/g for monensin) compared to the liquid fractions (