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Riverine outflow is one of the major pathways for microplastic transportation to coastal environments. Research on the output of microplastics in small- or medium-sized rivers will help accurately understand the status of their marine loads. In this study, we used both trawling and pumping methods to collect microplastics of different sizes in the Jiulong River Estuary and Xiamen Bay. We found that the abundance of small microplastics (44 μm–5.0 mm) was at least 20 times higher than the large particles (0.33–5.0 mm). The abundance of the large particles ranges from 4.96 to 16.3 particles/m 3 , and that of the small particles ranged from 82.8 to 918 particles/m 3 . Granule was the dominant shape (>60%), and polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the most common components. The riverine flux of small microplastics (44 μm–5 mm, 472 ± 230 t/y) was at a medium level and was eight times greater than that of large particles (0.33–5.0 mm, 61.2 ± 2.6 t/y). The behavior of the large microplastics was relatively conservative, whose abundance had a significant correlation with salinity ( R 2 = 0.927) and was mainly influenced by physical factors. In contrast, results of statistical analysis revealed that more complicated factors influenced the small microplastics.

The WRF-lake vertically one-dimensional (1D) water temperature model, as a submodule of the Weather Research and Forecasting (WRF) system, is being widely used to investigate water—atmosphere interactions. But previous applications revealed that it cannot accurately simulate the water temperature in a deep riverine reservoir during a large flow rate period, and whether it can produce sufficiently accurate heat flux through the water surface of deep riverine reservoirs remains uncertain. In this study, the WRF-lake model was improved for applications in large, deep riverine reservoirs by parametric scheme optimization, and the accuracy of heat flux calculation was evaluated compared with the results of a better physically based model, the Delft3D-Flow, which was previously applied to different kinds of reservoirs successfully. The results show: (1) The latest version of WRF-lake can describe the surface water temperature to some extent but performs poorly in the large flow period. We revised WRF-lake by modifying the vertical thermal diffusivity, and then, the water temperature simulation in the large flow period was improved significantly. (2) The latest version of WRF-lake overestimates the reservoir—atmosphere heat exchange throughout the year, mainly because of underestimating the downward energy transfer in the reservoir, resulting in more heat remaining at the surface and returning to the atmosphere. The modification of vertical thermal diffusivity can improve the surface heat flux calculation significantly. (3) The longitudinal temperature variation and the temperature difference between inflow and outflow, which cannot be considered in the 1D WRF-lake, can also affect the water surface heat flux.

BACKGROUND AND OBJECTIVES: The concentration of particulate organic carbon serves as a key indicator of biological productivity within the euphotic zone. Estimating its variability delivers key perspectives on the overarching trends in. The objective of this study is to explore the distribution of particulate organic carbon over time and space, as well as to model its fluctuations in Jakarta Bay, thereby enriching the knowledge of organic carbon dynamics in coastal ecosystems. METHODS: Monthly moderate-resolution imaging spectroradiometer satellite data for surface particulate organic carbon and chlorophyll-a during 2011 to 2023 periods were collected. In addition, seasonal in-situ data of salinity, sea surface temperature, dissolved oxygen, nitrate, and phosphate, were examined to assess the potential impact of natural processes on the fluctuations of particulate organic carbon variability in this bay. The seasonal autoregressive integrated moving average model was selected for particulate organic carbon forecast. FINDINGS: The concentration of particulate organic carbon varied between approximately 230 and 340 within the observed range. Significant concentrations were noted in the nearshore areas owing to the river's outflow into the bay. The seasonal variation indicates that the highest concentrations occur during the north west monsoon. Meanwhile, the lowest concentrations were observed during the Inter-monsoon II. In spite of the considerable variability, the trend in particulate organic carbon is almost constant (Coefficient of determination 0.0002) from retrospective analysis to predictive modeling. CONCLUSION: The results showed that in Jakarta Bay, particulate organic carbon variability is primarily influenced by a combination of biological production and physical transport processes modulated by monsoonal forcing. The predictions indicate that, under the current pressures, there will be negligible near-term shifts in the dynamics of particulate organic carbon along the northern coastline of Jakarta.

Detailed carbon budgets from 2008 to 2010 were created for two 1-ha flow-through riverine wetlands created in 1994 adjacent to a third–order stream in central Ohio. Measurements were taken of dissolved non-purgeable organic carbon (NPOC), dissolved inorganic carbon (DIC), fine particulate organic carbon (FPOM), and coarse particulate organic carbon (CPOM). Methane emissions, soil sequestration, aquatic primary productivity, and macrophyte aboveground net primary productivity were also included in the carbon budget. The carbon budget successfully balanced inputs (1838 ± 41 g C m −2  year −1 ) and export/sequestration (1846 ± 59 g C m −2  year −1 ) with only a 0.5 % over estimation of export in relation to input; 12.8 % of the inflow was sequestered into the wetland soil. FPOM and CPOM concentrations and exports were positively correlated with hydrologic flow under most circumstances; NPOC and DIC concentrations were usually negatively or poorly correlated with hydrologic flow. In all seasons, except winter, the change of total carbon (NPOC, DIC, FPOM, and CPOM) concentration between inflow and outflow increased with increased hydrologic flow. Although carbon concentrations increased from inflow to outflow, the total surface water export of carbon is less than the inflow due to groundwater recharge from these perched wetlands.