Bottom-up ship emission inventories derived from Automatic Identification System (AIS) data are normally reported on kilometre-scale grids, which merge port waters that perform very different functions. Working with an AIS-based STEAM inventory for the Yangtze River Delta (YRD), we ask a question that gridded inventories rarely separate: are the cells where ships accumulate time the same cells where they emit? To answer it, we define the Static–Dynamic Ratio (SDR), the ratio of hotelling (auxiliary-engine) to propulsion (main-engine) emissions within a cell, and use it to classify YRD waters without recourse to external port charts. Hotelling-dominated cells occupy 17.7% of the sea area and accumulate 59.3% of all ship-hours, a ship-hour density seven times that of transit-dominated fairways, yet they carry only 22.4% of NOx. A vessel at anchor emits about one-eighth as much NOx per hour as one under way, and the two effects nearly cancel. The cancellation is species dependent: low-load correction factors are steeper for sulfur and particulate species than for NOx, so hotelling zones reach relative SO2 and PM2.5 densities of 1.21 and 1.09 against 0.89 for NOx. Coarsening the same activity field from 100 m to 1 km drops the share held by the busiest 1% of cells from 70% to 50%, showing how kilometre grids manufacture apparent continuity along shipping lanes. Activity hotspots are therefore not emission hotspots, and anchorage-targeted measures such as shore power are best justified by particulate and sulfur exposure near populated coasts rather than by their share of the regional NOx burden.
Under the ongoing implementation of China's Domestic Emission Control Area (DECA) policy, shipping emissions and their impacts on air quality have drawn increasing attention. However, most studies have focused on the early and intermediate phases of DECA implementation, leaving the emission characteristics and multi-pollutant responses in the post-DECA era insufficiently quantified. This study investigates the Yangtze River Basin, the world's busiest inland shipping corridor, by constructing a high-resolution emission inventory for 18,478 vessels based on approximately 230 million Automatic Identification System (AIS) trajectories in 2023, and coupling it with the WRF-Chem model to quantify the contribution of ship emissions to regional air quality. Results show that SO2 and PM2.5 emissions from Yangtze shipping have been substantially controlled in the post-DECA era, whereas NOx emissions reached 156.41 kt yr-1, accounting for 82.0% of the total emissions of major pollutants, and formed pronounced hotspots along heavily trafficked reaches, including Yichang-Jingzhou, Wuhan, and Nanjing-Shanghai. Concentration simulations indicate a stable positive contribution of ship emissions to NO2 with marked near-source effects, yielding annual mean contributions of 0.16-3.41 μg m-3 across 11 mainstem cities. PM2.5 increments are generally low, but nitrate constitutes a substantial fraction. O3 responds differently, showing clear seasonal variation driven by photochemical processes: it decreases in January and October due to near-source NO titration but increases in July under strong photochemical conditions. These findings suggest that, beyond sustaining fuel-sulfur control and particulate mitigation, inland shipping emission management should advance toward coordinated strategies centered on source-level NOx reduction.
In the context of multimodal-freight modeling efforts, the US Army Corps of Engineers (USACE), Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), entered into an inter-agency agreement with the Department of Transportation (USDOT), Bureau of Transportation Statistics (BTS), to produce travel-time statistics for select portions of the US inland waterway transportation system. Statistics include the median, interquartile range average, and 10th–90th percentile averages between origin and destination (OD) sets selected based on vessel traffic activity, especially lock and dam locations, which are natural stopping points. Travel-time statistics are derived from position reports broadcast via Automatic Identification System (AIS) transceivers for vessel transits that occurred in 2021. This technical report summarizes the methodology and findings.
Marin M. Kress, Magdalena I. Asborno, Laura Dods et al.· 0 citations
Anthropogenic greenhouse gases (GHGs) and emissions from maritime transport represent a significant challenge for atmospheric monitoring and control. The Istanbul Strait, characterized by its narrow, winding geography and high traffic density, presents a unique chokepoint where these emissions directly impact local air quality. This study proposes a gas-focused integrated framework that combines Sentinel-5 Precursor (Sentinel-5P) TROPOspheric Monitoring Instrument (TROPOMI) satellite observations with Automatic Identification System (AIS) data to analyze atmospheric trace pollutant time series in the Istanbul Strait during 2025. A bottom-up emission methodology based on the IMO 4th GHG Study was employed, yielding annual gaseous pollutant totals of 213,678 tons of carbon dioxide (CO2), 5970 tons of nitrogen oxides (NOx), and 686 tons of sulfur oxides (SOx). Time-series and cross-correlation analyses demonstrated a quantifiable relationship between AIS-derived NOx estimates and TROPOMI NO2 tropospheric column densities (r = 0.76, p < 0.05, n = 12), validating the use of satellite sensors for marine atmospheric monitoring. A decision support system (DSS) proof of concept (PoC) was developed to evaluate emission control scenarios through speed optimization. The results indicate that implementing a 10% speed reduction strategy could reduce CO2 emissions by 18% (38,462 tons) and generate net economic savings of EUR 3.07 million under the European Union Emissions Trading System (EU ETS) carbon pricing framework. Furthermore, a scenario with a 20% speed reduction resulted in a 35% decrease in CO2 emissions. The findings underscore the potential of integrating satellite-based gas remote sensing with AIS data, thereby facilitating real-time atmospheric monitoring and strengthening emission control policy enforcement in maritime chokepoints.
Surface ozone (O3) pollution persists in the Yangtze River Delta (YRD) of China, with frequent exceedances despite stringent controls, driven by complex NOx-VOC interactions. Current monitoring struggles to accurately identify O3 formation regimes (VOC- vs. NOx-limited) at urban scales during daytime. By integrating TROPOMI satellite data with high-resolution ground-based joint observations, we reveal scale-dependent regime transitions: megacities (G1 cities, population > 5 million and GDP > 1 trillion CNY yr−1) exhibit narrow HCHO-to-NO2 ratio (FNR) transition ranges (1.54–2.86), and O3 pollution (≥160 μg/m−3) may occur under all regimes (VOC-limited, transitional, and NOx-limited). In contrast, smaller G2 cities show wider transition ranges (1.85–3.43), with O3 pollution occurring primarily under transitional and NOx-limited conditions. Observations from a typical G1 city demonstrate that VOC reductions effectively control O3 under VOC-limited regimes, while NOx mitigation alone is insufficient in NOx-limited environments due to persistently high VOC backgrounds. Our findings suggest city-specific strategies: G1 cities require adaptive co-control of VOCs and NOx to accommodate localized chemistry, whereas G2 cities benefit from targeted measures aligned with dominant sensitivity regimes. This study provides observational verification of environment-dependent O3 formation mechanisms, offering a methodological framework for precision air quality management in rapidly developing regions.
Keqiang Cheng, Wei Dai, M. Xie et al.· Remote Sensing· 0 citations
Flooding along the Bontang River in Gunung Telihan Village, Bontang City, recurs almost annually, yet its causes had not been diagnosed mechanistically. This study applied one dimensional steady-flow HEC-RAS 4.1 modeling to a 1,936 m reach, using primary topographic data and design discharges (Q2, Q10, Q20) from the Nakayasu Synthetic Unit Hydrograph. Unlike prior single mechanism studies, the analysis resolved four co occurring flood mechanisms: bank-asymmetry overflow, right bank levee overflow, undersized sluice-gate backwater, and a downstream constriction. Although nominal channel capacity (13.83 m3/s) marginally exceeded Q2 (11.88 m3/s), the low right bank reduced the effective overflow threshold below Q2. A 95% confidence interval on design discharge, computed using Kite's asymptotic method, indicated the downstream constriction could approach overflow at the upper bound of Q10 uncertainty. An independent tidal sensitivity check showed the tidal range effect at the confluence (2.2 m) exceeded the sluice-gate backwater step alone (0.42-0.68 m). A planned condition simulation combining retention ponds, levee reinforcement, and gate augmentation achieved safe status at all critical points, indicating site differentiated intervention is a promising, land feasible direction pending detailed design verification.
Viva Oktaviani, Heri Purnomo· ZERO Jurnal Sains Matematika...· 0 citations
As variable renewable generation grows, intermittent dispatch of run-of-river hydropower plants may transfer required environmental-flow releases from turbines to spillways, creating conditions that favor total dissolved gas (TDG) supersaturation and may constrain hydropower flexibility. This study presents a reproducible basin-scale screening assessment for 24 selected hydropower plants in the Brazilian Amazon and Tocantins–Araguaia basins. The analysis combines a plant inventory, spillway typology, standardized environmental-flow scenarios, and two configuration-specific linear relationships between unit discharge and the increase in TDG saturation (ΔTDG), derived from digitized Pubugou and Gongzui observations. Two release configurations were examined: flow distributed among all available bays and flow concentrated in a single bay as a theoretical hydraulic bounding case. The Pubugou-based relationship was applied only to broadly comparable ski-jump configurations within 9.1 ≤ UD ≤ 72.3 m3 m−1 s−1, whereas the Gongzui-based relationship was provisionally assigned, as an inventory-level first-order analog, to controlled spillways discharging into stilling basins within 34.6 ≤ UD ≤ 234.6 m3 m−1 s−1. Hydraulically dissimilar cases were classified as NE-H, and cases outside the applicable empirical domain as NE-UD. Digitization sensitivity, regression uncertainty, and model-form selection were explicitly evaluated and documented. None of the distributed-flow scenarios produced a numerical estimate: cases assigned to the Pubugou- or Gongzui-based relationships were classified as NE-UD, whereas hydraulically dissimilar free-surface cases were classified as NE-H. Four single-bay scenarios produced configuration-specific ΔTDG increments: 22.5–33.4 percentage points for three Gongzui-based cases and 13.6 percentage points for one Pubugou-based case. Upstream TDG was not added, and no plant-specific final concentration or universal ranking was reported. Sinop and Colíder observations were retained as qualitative contextual evidence of limited transferability and the importance of site-specific hydraulics. The outputs support conditional monitoring prioritization under standardized assumptions, not compliance prediction, ecological-risk assessment, or gate-operation recommendations. Synchronized monitoring and plant-specific rating curves are required before TDG-related variables can be incorporated into operational planning.
G. Ferraz, D. Ribeiro, Guilherme S. Bastos et al.· Energies· 0 citations