Total suspended solid (TSS) pollution load model at the Jagir River Estuary, Surabaya, East Java

The research aims to create a TSS spatial distribution map model and a pollution load model at the Jagir River Estuary—a descriptive method for the last six years to describe the TSS pollution load model. Satellite image data processing uses SNAP software with the application of the Laili algorithm (2015). The distribution of TSS pollution values and loads still meets the quality standards for mangrove ecosystems. The average value of TSS distribution in 2018 - 2023, respectively, is 18,966 mg/L, 14,578 mg/L, 17,267 mg/L, 16.921 mg/L, and 15,013 mg/L with the highest TSS pollution load occurring in 2023 and the lowest in 2021 and 2022. The average pollution load from 6 research stations in 2019 – 2023 still does not exceed the capacity limit of the Jagir River to accommodate TSS accumulation. The TSS pollution load model in the Jagir River Estuary, Surabaya, East Java, follows a quadratic pattern with the regression equation y = -173.01X2 + 2339.20X - 2299.80 (R2 = 0.7674) with a peak TSS pollution load reaching 5,607.05 tons m3/month in January and lowest in August


Introduction
The mouth bar of the Jagir River is located in Wonorejo Village, Rungkut District, Surabaya City, East Java.This area has experienced much degradation due to land conversion, erosion, and sedimentation from various activities along its flow [1].Pollution monitoring aims to determine the total pollution load entering the waters.Pollution monitoring can be done directly in the field (in situ) and indirectly using remote sensing technology from satellite imagery [2].One of the water quality parameters that dominates river water pollution is TSS [3][4][5][6].
Monitoring TSS pollutant loads can be carried out using remote sensing methods because this method is considered adequate in terms of time, cost, and coverage of the observation area using satellite imagery [7].A sensor system's spatial, temporal, spectral, and radiometric resolution determines its ability to remotely sense watercolor [8].The Sentinel 2 Multispectral Imager (MSI), a constellation of two satellites in sun-synchronous polar orbit, targets land and coastal zone monitoring by providing high spatial (10-60 m) and temporal (2-5 days) resolution images [9].MSI has 13 bands from the visible to shortwave infrared (SWIR) spectral regions, providing an appropriate data source for documenting suspended particulate matter (CSPM) variations in coastal and inland waters [10].Several studies have been carried out in retrieving water parameters using Sentinel 2 MSI data.[11] applied a Sentinel 2 MSI dataset simulation to extract CSPM values in turbid estuarine waters.[12] investigated the sensitivity of Sentinel 2 MSI to optically active material in an Italian lake with simulated reflectance from a bio-optical model.[13] applied Sentinel 2 MSI to assess oligotrophic lake waters' water content and bottom characteristics.[14] demonstrated the superiority of Sentinel 2 MSI over Landsat 8 OLI in retrieving suspended matter in black lakes.[15] obtained high agreement accuracy between in-situ data and remote sensing reflectance from Sentinel 2 MSI for chlorophyll-a (R2 = 0, 83) and organic carbon dissolved chlorophyll (R2 = 0.92).In addition, the potential of Sentinel 2 MSI in monitoring water quality in inland and coastal waters has been anticipated [16,17].Sentinel-2 data can be used for TSS modeling using channel 7 (Visible and Near Independent/VNIR) [18].
Remote sensing is a technique for obtaining information about an object through data analysis without direct contact with the studied object.The satellite image used in the research is the Sentinel 2A satellite image.The application of remote sensing in TSS monitoring applies the NDWI (Normalised Difference Water Index) algorithm and the application of the algorithm in research [19].This research aims to analyze the spatial distribution of TSS and the TSS pollution load at the river mouth bar. .

Description of the research site and experimental design
The research location at the mouth bar of the Jagir River is located in Wonorejo Village, Rungkut District, Surabaya City, East Java.The Jagir River flows through urban areas in the form of densely populated residential areas, industrial areas, and the Wonorejo Mangrove conservation area, Surabaya.
Based on the sampling points, tss data plotted on the map is obtained as follows (Figure 1).where: 2 is reflectance band 2; 4 is reflectance band 4.

River Water Discharge Model
Discharge measurements are measurements of wet cross-section, flow velocity, and water level.However, on the Jagir Wonokromo River, Surabaya, this is done by making discharge recapitulation data from observers of the magnitude of the discharge using a measuring instrument in the form of a measuring ruler located on the side of the river, precisely in the cliff area close to the river.Sluice.Based on calculation results (23), the water discharge of the Jagir Manan River is 188.56 m³/month, with the highest peak being 386 m3/month in March and the lowest in September at 67.70 m3/month.

Data analysis
The research uses Sentinel-2A image data from 2019 to 2023 and water discharge model data from the Jagir Manan River.Data analysis includes satellite image analysis, classification model analysis, and Ftest statistical analysis.

Data analysis
The Jagir River estuary's multi-temporal average TSS distribution value over the last six years is 17.02 ± 1.27 (Table 1).This TSS distribution value results from processing Sentinel 2A satellite image data and the algorithm (19).The average value of the highest TSS concentration distribution in 2018 was 18.94 ± 1.11 mg/l.In 2019, 2020, 2021, and 2022, respectively, the TSS distribution value was 16.31 ± 0.99 mg/l, 17.22±1.20mg/l, 15.77±1.18mg/l and 17.02±1.14mg/l, (Table 1).TSS tends to decrease in 2019 and will increase again in 2022.Changes in TSS in the Manan Jagir River estuary decreased with the 2019 COVID outbreak and increased again after COVID-19 subsided.This model of the rise and fall of TSS in the Jagir Manan River is identical to the results of TSS research in the Min River in China [24].This research shows a correlation between a decrease in TSS during the 2019 COVID-19 pandemic and an increase again after the 2019 COVID-19 subsided.[24] further stated that the decline in TSS values during the Covid-19 pandemic reached 48% in the Min River (China) in February 2020 due to a significant reduction in waste disposal from industrial areas, densely populated city centers and shipping.
4 Based on the TSS distribution results from Sentinel 2A satellite image data processing, the TSS concentration at the mouth bar of the Jagir River has not exceeded the quality standards set by the Ministry of the Environment No. 22 of 2021 attachment VI.The TSS value at the mouth bar of the Jagir River still meets the requirements for ecosystem use, including mangroves, coral reefs, and seagrass, as well as meeting the requirements for marine tourism and ports.

TSS model and Jagir Manan River water discharge
Measuring water discharge is measuring the wet cross-section, flow velocity, and water level.However, on the Kali Jagir Wonokromo Surabaya, discharge calculations are carried out by making discharge recapitulation data from observers of the magnitude of the discharge using a measuring instrument in the form of a measuring ruler located on the side of the river, precisely at cliff area close to the water gate.Based on calculation results (23), the water discharge of the Jagir Manan River is 188.56 m³/month, with the highest peak being 386 m3/month in March and the lowest in September at 67.70 m3/month.The monthly distribution model of water discharge in the Jaguar Manan River follows an inverse quadratic distribution pattern with the equation model y = 180.62x2-2,164.1x+ 7,813 (R² = 0.9187).Meanwhile, the model for the average distribution of TSS each month follows the distribution pattern Y = 0.0387x2 -0.1381x + 15.923 R² = 0.7953) with the lowest TSS of 15.80 mg/l.The monthly water discharge and TSS equation model is presented in Figure 2.

TSS Pollution Load Analysis
The pollution load comes from the input of waste resulting from activities such as household activities, fisheries, ponds, and industrial activities along the Jagir River.River pollution load is calculated based on measurements of discharge and TSS pollutant concentration values (25).In this case, TSS, the approach to the concentration value of water quality parameters, was carried out to determine the influence of existing activities on the total pollutant load that empties into the Jagir River, Wonorejo Waters, Surabaya, Java.The TSS quality standard value is based on PP 82 of 2001 concerning water quality management and water pollution control; the TSS value of good waters is ≤1000 mg/L.The average concentration of TSS pollution load in the Jagir River Estuary was the highest in 2018, 3,129 ± 2,643 tonnes/month.The lowest TSS pollution load concentration will be in 2022, namely 2,4843 ± 1,575 tonnes/month.Furthermore, in 2019, 2020, 2021, and 2023, respectively, the TSS pollution load concentration was obtained at 2,549 ± 1,595 tons/month, 2,841 ± 2,001 tons/month, 2,628 ± 1,826 tons/month and 2,539 ± 1,591 tons/month.Although there is no difference in TSS during the rainy and dry seasons, higher monthly TSS pollutant loads occur during the rainy season as a result of high water discharge [5,[23][24][25].These findings are valuable for determining when the peak TSS pollutant load will occur in Jagir Manan River water and for finding the position of the main source of TSS.This remote sensing-based approach with high temporal resolution for TSS estimation has the potential to support river system water quality monitoring and management efforts.

Conclusion
There has been no difference in monthly TSS over the last five years, with a TSS range of 15 -19 ppm.
The TSS pollution load model in the Jagir River Estuary, Surabaya, East Java, follows a quadratic pattern with the regression equation y = -173.01X

5 Figure 2 .
Figure 2. TSS distribution model and monthly water flow in the Jagir Manan River

Table 1 .
Average TSS at the mouth bar of the Jagir River Figure 3. Monthly TSS distribution model in the Jagir Manan RiverThe monthly average TSS pollution load model in the Jagir River Estuary, Surabaya City, East Java, during 2019 -2023 obtained the equation y= -138.38X2+1733X-572.21(withR²= 0.7109).Based on the predictions of this equation, the peak TSS pollutant load occurs at the end of February or towards the beginning of March, with a peak pollutant load of 4,853.59tonnes/month(Figure3).The quality standard value for TSS pollutant load is based on PP 82 of 2001 concerning water quality management and pollution control; a good TSS value for water is ≤1000 mg/L.The average concentration of TSS pollution load in the Jagir River Estuary was the highest in 2018, at 3,719.82 tonnes/month. 6 2+ 2339.20X-2299.80(R² = 0.77) with a peak TSS pollution load reaching 5,607.05m 3 / month in January and the lowest in August.