In drinking water distribution systems (DWDSs), pipe material and water temperature are some of the critical factors affecting the microbial flora of water. Six model DWDSs consisting of three pipe materials (galvanized steel, copper, and PEX) were constructed. The temperature in three systems was maintained at 22 °C and the other 3 at 32 °C to study microbial and elemental contaminants in a 6-week survey using 16S rRNA next-generation sequencing (NGS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Pipe material and temperature were preferentially linked with the composition of trace elements and the microbiome of the DWDSs, respectively. Proteobacteria was the most dominant phylum across all water samples ranging from 60.9% to 91.1%. Species richness (alpha diversity) ranking was PEX < steel ≤ copper system and elevated temperature resulted in decreased alpha diversity. Legionellaceae were omni-prevalent, while Mycobacteriaceae were more prevalent at 32 °C (100% vs. 58.6%) and Pseudomonadaceae at 22 °C (53.3% vs. 62.9%). Heterogeneity between communities was disproportionately driven by the pipe material and water temperature. The elevated temperature resulted in well-defined microbial clusters (high pseudo-F index) in all systems, with the highest impact in PEX (10.928) followed by copper (9.696) and steel (5.448). Legionellaceae and Mycobacteriaceae are preferentially prevalent in warmer waters. The results suggest that the water temperature has a higher magnitude of impact on the microbiome than the pipe material.

In the Kingdom of Saudi Arabia (KSA) and other arid regions, higher education institutions account for a significant share of energy consumption and greenhouse gas (GHG) emissions. Improving the environmental performance of higher education institutions is important to achieving nationwide impact reduction. This study evaluates the water, energy, and carbon (WEC) footprint of higher education campuses in arid environments. Qassim University (QU), KSA, is a leading public institution of higher education and research in Buraydah City and was selected for this study. A comprehensive assessment based on the GHG Protocol was conducted for the period 2022–2025, covering Scope I, II, and III emissions. This study analyzed institutional data on water use, wastewater, electricity consumption, transportation, waste generation, and air travel. The results show that total water consumption increased from 354,747 m³ in 2022 to 547,268 m³ in 2025, with per capita use rising from 46.2 to 61.7 L/c/day. Net water demand, including irrigation, reached 877,456 m³ in 2025. The declining trend in energy consumption between 2022 and 2025 reflects significant (33%) energy savings with the use of sensors and the overall tendency towards sustainability. Correspondingly, Scope II emissions decreased significantly from 147.2 million kg CO₂/year to 99.1 million kg CO₂/year and were the dominant CO₂ contributor (60–75% of total emissions). In contrast, Scope III emissions from commuting staff and students increased, with transport-related emissions rising from 36.4 million kg CO₂/year in 2022 to 52.2 million kg CO₂/year in 2025. This study also evaluated current and potential CO₂ emission reduction scenarios targeting energy and transportation systems on the QU campus. The findings indicate that the deployment of a 5.1 MW solar energy system can generate approximately 8.6 million kWh annually, resulting in a reduction of around 4000 tCO₂ and contributing to nearly 43% of the 2030 emission reduction target. In addition, transportation-focused strategies—including modal shift, vehicle electrification, and hybrid learning approaches—demonstrate significant mitigation potential, with total reductions reaching up to 18,700 tCO₂ by 2030. Overall, this study contributes to the limited body of knowledge on WEC footprint assessments on university campuses in arid regions and provides a baseline for future sustainability planning.

Legionnaires’ disease incidence has risen substantially across industrialised nations since the early 2000s, yet standard control protocols—primarily secondary disinfection verified by culture—rely on an evidence base that warrants further scrutiny. This review offers three interpretations of the available evidence, without claiming they are established conclusions. First, culture-based verification has inherent methodological limitations: treatments that reduce culturability can induce viable-but-non-culturable (VBNC) states undetected by culture alone, creating potential discrepancies between verified culture reduction and complete microbial clearance. This reading rests on evidence that monochloramine at ≥1 mg/L abolishes culturability while genomic units remain essentially unchanged and that starved VBNC Legionella retain the capacity to infect human macrophages after more than 220 days, albeit at roughly 1% the efficiency of culturable cells; whether this translates into material risk in operating buildings remains undetermined. Second, much of the comparative-effectiveness literature evaluating disinfectants relies on observational single-site studies, and early validation frameworks often depended on self-reported survey data; randomised comparison in occupied healthcare buildings is frequently impractical, though recent systematic reviews now supply quantitative synthesis earlier work lacked. Third, regulatory thresholds remain expressed in the units of the method whose deficiencies motivated the alternatives, and the alignment of verification standards with advances in molecular detection remains an ongoing challenge.

Backward-trajectory statistics locate arid-region dust sources on the assumption that trajectories separate emission from transport, an assumption seldom tested where the local contribution is known. We build one from ten years (2016–2025) of routine METAR observations at Riyadh, Saudi Arabia, where present-weather codes distinguish locally lifted dust (BLDU/BLSA) from dust in suspension (DU/SA). Suspension-dominated days outnumbered locally lifted days 345 to 179 (1.9:1), and ERA5-driven models reproduced the locally lifted class substantially better (held-out AUC 0.914 versus 0.765), indicating distinct meteorological signatures. Dust activity then fell 85.9% below the 2016–2022 baseline in 2023–2024, recovering only to 56.0% below it in 2025. The model did not anticipate this: observed dust days in 2023–2024 were 13–27% of the calibrated expectation in every class while local surfaces in 2024 stayed favorable for emission; upwind dust availability and transport remain hypotheses. We then computed PSCF and CWT fields from 14,612 HYSPLIT trajectories, running the locally lifted class, for which a distant source is not required, as an imperfect negative control, tested against permutation nulls. Under unmatched and season-matched backgrounds, the control was more enriched than the suspension-dominated class over the eight a priori candidate regions (p ≤ 0.007), and wind matching removed most regional structure from both. Both fields are shaped largely by the shared Shamal transport climatology and the wind selection of dust days, limiting their ability to identify emitting terrain. At wind-selected, single-regime receptors, PSCF and CWT source fields should be interpreted alongside such a control.

Sustainable coastal environmental management relies on continuous assessment of sediment quality. In the Saudi Arabian Red Sea, such sediments function as both sinks and potential secondary sources of heavy metals (HMs) originating from natural processes and anthropogenic activities. The present study investigated the concentrations of HMs in surface sediments from Jeddah and Rabigh. Contamination levels, as well as possible natural and anthropogenic inputs and potential risks to human health through ingestion, dermal contact, and inhalation pathways, were evaluated. The results indicated that Fe is the most abundant metal at both sites (1570.40 mg/kg at Jeddah and 1804.11 mg/kg at Rabigh). Cu, Ni, and Zn are present in the sediments at concentrations ranging between 3.12 and 4.49 mg/kg, while Cd and Pb remain below the detection limits in all samples. Generally, the contamination index values indicated low levels in both regions. The evaluation of human health risks identified ingestion as the primary exposure pathway. Non-carcinogenic risk levels were within safe limits for both adults and children. However, the carcinogenic risk assessment of nickel (Ni) indicated that all values fall within the acceptable range (10⁻⁶–10⁻⁴), although children consistently showed higher risks than adults. Despite the overall low levels of pollution, the moderate enrichment of Cu, Ni, and Zn in Jeddah and Cu in Rabigh, along with the higher non-carcinogenic risks to children at the Rabigh site, highlights the need for continuous environmental monitoring and further investigation to support the sustainable management of coastal ecosystems.