The increasing frequency and severity of wildfires are among the most visible impacts of climate change. However, the effects of wildfires on mercury (Hg) transformations and bioaccumulation in stream ecosystems are poorly understood. We sampled soils, water, sediment, in-stream leaf litter, periphyton, and aquatic invertebrates in 36 burned (one-year post fire) and 21 reference headwater streams across the northwestern U.S. to evaluate the effects of wildfire occurrence and severity on total Hg (THg) and methylmercury (MeHg) transport and bioaccumulation. Suspended particulate THg and MeHg concentrations were 89 and 178% greater in burned watersheds compared to unburned watersheds and increased with burn severity, likely associated with increased soil erosion. Concentrations of filter-passing THg were similar in burned and unburned watersheds, but filter-passing MeHg was 51% greater in burned watersheds, and suspended particles in burned watersheds were enriched in MeHg but not THg, suggesting higher MeHg production in burned watersheds. Among invertebrates, MeHg in grazers, filter-feeders, and collectors was 33, 48, and 251% greater in burned watersheds, respectively, but did not differ in shredders or predators. Thus, increasing wildfire frequency and severity may yield increased MeHg production, mobilization, and bioaccumulation in headwaters and increased transport of particulate THg and MeHg to downstream environments.

The characteristics of the resistome distribution in rivers have been extensively studied. However, the distribution patterns of resistomes in multiple habitats and contributions of upstream habitats to the resistome profile in water bodies remains unclear. The current study explored the distribution and coalescence of antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and mobile genetic elements (MGEs) in four habitats (including water bodies, sediments, biofilms, and riparian soils) within the Shichuan River watershed. The results revealed significant variations in the abundances and diversity of resistomes across the four habitats and two seasons. Assembly processes of resistomes were predominated by stochastic processes in summer but deterministic processes in winter. The main source of the resistome in summer water bodies was the movement of genes from upstream water bodies. However, the main sources of resistome in downstream water bodies in winter were the movement of resistomes in upstream sediments and the input of external pollution. The physicochemical properties of winter water bodies significantly influenced the movement of the resistomes across habitats. The current study elucidated the multi-habitat distribution pattern and migration mechanism of the resistome in the river system, providing new insights for effectively monitoring and controlling bacterial resistance.

Two years of monthly sampling and hydrological monitoring were performed at the outlet of a Mediterranean watershed in northern Tunisia to determine the contents of 469 pesticide active ingredients and metabolites in water and evaluate their behavior. Wadi Guenniche is a tributary of the Bizerte coastal lagoon, with a watershed area of 86 km2, which exhibits pluvial cereal, legume, and orchid cultivation and irrigated market gardening. Twenty-nine pesticide active ingredients and 2 metabolites were detected in water. Twenty-four pesticide active ingredients were authorized for use in Tunisia. Among them, 14 had never been mentioned in previous farmer surveys. Five herbicides and their metabolites were the most frequently detected: aminomethylphosphonic acid (AMPA) (100%), glyphosate (94%), simazine (94%), 2,4-D (70%), and deisopropylatrazine (DIA) (47%). The detection frequency and concentration range suggested that the phytosanitary pressure and resulting water contamination are close to those on the northern Mediterranean shore. These results, in addition to characterizing the pollution state, emphasized the need for additional studies on the use and fate of pesticides on the southern shore of the Mediterranean Sea, particularly in Tunisia.

Mercury (Hg) in runoff water poses significant ecological risks to aquatic ecosystems that can affect organisms. However, accurately identifying the sources and transformation processes of Hg in runoff water is challenging due to complex natural conditions. This study provides a comprehensive investigation of Hg dynamics in water from rainfall to runoff. The Hg isotope fractionation in water was characterized, which allows accurate quantification of Hg sources, transport, and transformations in rainfall-runoff processes. Δ200Hg and corrected Δ199Hg values can serve as reliable tracers for identifying Hg sources in the runoff water and the variation of δ202Hg can be explained by Hg transformation processes. During runoff migration processes, Hg from rainfall is rapidly absorbed on the land surface, while terrestrial Hg entering the water by the dissolution process becomes the primary component of dissolved mercury (DHg). Besides the dissolution and adsorption, microbial Hg(II) reduction and demethylation of MeHg were dominant processes for DHg in the runoff water that flows through the rice paddies, while photochemical Hg(II) reduction was the dominant process for DHg in the runoff water with low water exchange rates. Particulate Hg (PHg) in runoff water is dominantly originated by the terrestrial material and derived from the dissolution and adsorption process. Tracking sources and transformations of Hg in runoff water during the rainfall-runoff process provides a basis for studying Hg pollution in larger water bodies under complex environmental factors.

The article presents the results of the characterization of the geometric structure of the surface of unalloyed structural steel and alloyed (martensitic) steel subjected to chemical processing. Prior to phosphating, the samples were heat-treated. Both the surfaces and the cross-sections of the samples were investigated. Detailed studies were made using scanning electron microscopy (SEM), XRD, metallographic microscopy, chemical composition analysis and fractal analysis. The characteristics of the surface geometry involved such parameters as circularity, roundness, solidity, Feret\'s diameter, watershed diameter, fractal dimensions and corner frequencies, which were calculated by numerical processing of SEM images.

Rainstorm flooding in developed urban areas has become a global focus. This study proposes a data-driven approach to urban rainstorm flood risk assessment. In contrast to the existing research, this study focuses on terrain watersheds as an assessment unit. Using Changsha as the study area, an inventory of 238 historical rainstorm flood locations was produced using automatic web crawling and literature data mining. Subsequently, an assessment model was developed based on a Bayesian algorithm and 16 influencing factors, and its accuracy was verified using a receiver operating characteristic curve. Because underground infrastructure is prone to backflow at its entrances and exits during rainstorms, the developed model was used to assess the backflow risk of two typical underground structures subjected to three rainstorm return periods: 5 (scenario 1), 10 (scenario 2), and 100 years (scenario 3). The conclusions are as follows: (1) The proposed method has a prediction accuracy of 88 % for flood risk. The most influential factors were H11 (proportion of impervious surface), H4 (mean elevation), and H1 (rainfall), contributing 52 %, 14.3 %, and 11.9 %, respectively. (2) Watersheds are classified into \"Very Low,\" \"Low,\" \"High,\" and \"Very High\" based on the degree of flooding impact, accounting for 83.6 %, 11.9 %, 3.9 %, and 0.7 %, respectively. Watersheds classified as \"Very High\" are mainly distributed in the central region. (3) A total of 48 subway stations (7.9 % of the total) and 148 underground parking lots (6.5 % of the total) in the study area are located in \"Very High\" risk areas. (4) Compared to that in scenario 1, the proportion of underground entrances and exits with a \"Very high\" protection level in scenario 3 increased by approximately 10 %. In conclusion, this framework can assist urban planners in understanding the risks of urban flooding and mitigating potential flooding impacts.

The pollutant transport equilibrium in a watershed can be analyzed on a large time scale, and land-use export coefficients can be calculated directly under certain hydrologic and transport conditions, by ignoring hydrologic and transport processes at small space and time scales on hydrologic response units. In this study, the water environment system of a watershed was deconstructed into three parts (source, source-sink, and runoff transport) to construct a pollutant transportation equilibrium model on a large time scale. A watershed with an annual source-sink accumulation of zero was defined as a completely transported watershed; therefore, we derived a completely transported equilibrium equation. The problem of seeking the land export coefficient was converted into a problem of seeking the optimal solution of linear programming, which can be estimated according to the variation in pollutant output processes. The feasibility of the solution can be analyzed using multi-year stochastic rainfall processes. The model was used to analyze the transport equilibrium of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) upstream of the monitored cross-sections in a watershed, which covered 3145.66 km2. The land export coefficients were calculated according to the model. The model calculations indicated that the watershed was completely transported during perennial years. The calculated export coefficients of COD, TN, and TP for farmland, primary vegetation, and urban land were within the range of general empirical values. The calculated maximum accumulations of COD, TN, and TP were 0.19 × 107, 0.063 × 107, and 0.049 × 106 kg, respectively, for perennial rainfall. PRACTITIONER POINTS: A completely transported watershed was defined, and a model of pollutant transportation equilibrium with large time-scale was constructed. A problem of seeking the optimal solution of a linear programming was designed to estimate the land export coefficient of COD, TN, and TP. The runoff transport and accumulation processes of COD, TN, and TP in a watershed was analyzed.

Patients with a persistent primitive trigeminal artery frequently have a poorly developed vertebrobasilar arterial system. However, they are not at higher risk of stroke and most are asymptomatic. Left cerebral watershed infarction was identified in a 75-year-old man who presented with aphasia and disorientation on magnetic resonance image (MRI). Additional imaging studies also demonstrated a right persistent primitive trigeminal artery, aplastic basilar artery, and 47% left internal carotid artery stenosis. Antiplatelet medication was administered and he was discharged 2 weeks after admission on aspirin. At the 4-month follow-up, cerebral blood flow in the left watershed territory was still decreased; however, no recurrent stroke had occurred. Although the indication for surgical or endovascular intervention for internal carotid artery stenosis is primarily determined by the degree of stenosis, cerebral blood flow evaluation is recommended in patients with internal carotid artery stenosis and a persistent primitive trigeminal artery.

Inadequate conservation practice affects the sustainable production of agricultural watersheds due to erosion and fertility decline. Understanding soil erosion and implementing site-specific conservation practice could enhance agriculture-based rural development. The study was aimed to document soil erosion problem and soil and water conservation effort. The specific objectives of this study were to assess soil erosion severity, practices to reduce erosion, and determinants of the decision to reduce erosion. Data were collected by interviewing 198 farm household heads, undertaking four focus group discussions, and assessing rill erosion in 10 farm fields in Morayo and Wacho sub-watersheds of southern Ethiopia. Descriptive statistics and binary logit model were applied to analyze the data. Results indicated that many of the farm households, 63% in Morayo and 83% in the Wacho sub-watershed, perceived moderate to severe soil erosion, which is characterized by big rills and small gullies on the farmlands. Rill densities of 231.4 m ha-1 and 84.1 m ha-1 in the Morayo and Wacho sub-watersheds were observed, respectively. The estimated annual soil loss due to rills was 61.2 and 23.4 Mg ha-1 in the Morayo and Wacho sub-watersheds, respectively. The soil erosion from rills alone exceeds the expected tolerable soil erosion (11 tons ha-1 year-1). Due to erosion, about 90% of farmers perceived farmland degradation as described by a progressive decline in crop yield. Farmers used to practice traditional techniques to reduce erosion and government introduced conservation measures such as soil and stone bunds. However, many farmers did not use well-promoted conservation measures such as bunds, which could have negative impact on long-term erosion control effort and sustainable implementation of the conservation options. Among the assessed explanatory variables, educational level, farm distance from home, slope of the cultivated land, and frequency of extension contact were significantly affected (p < 0.05) farmers\' sustainable use of conservation measures. Development planners and policy makers are advised to consider site-specific and innovative approaches to implement conservation measures in sustainable approach in the smallholder crop-livestock mixed agriculture system.

The Ala Wai Canal is an artificial waterway in the tourist district of Waikiki in Honolulu, HI. Originally built to collect runoff from industrial, residential, and green spaces dedicated to recreation, the Ala Wai Canal has since experienced potent levels of toxicity due to this runoff entering the watershed and making it hazardous for both marine life and humans at current concentration, including Danio rerio (zebrafish). A community of learners at educations levels from high school to postbaccalaureate from Oahu, HI was connected through the Consortium for Increasing Research and Collaborative Learning Experiences (CIRCLE) distance research program. This team conducted research with an Investigator and team from Mayo Clinic in Rochester, MN, with the Ala Wai Canal as its primary subject. Through CIRCLE, research trainees sent two 32 oz bottles of Ala Wai- acquired water to a partnered laboratory at the Mayo Clinic in which zebrafish embryos were observed at differing concentrations of the sampled water against a variety of developmental and behavioral assays. Research trainees also created atlases of developmental outcomes in zebrafish following exposure to environmental toxins and tables of potential pesticide contaminants to enable the identification of the substances linked to structural defects and enhanced stress during Ala Wai water exposure experiments.