Spatial and temporal distribution of nutrients in the Ciliwung River, DKI Jakarta

The Ciliwung River, one of the largest rivers to run through Jakarta, is particularly important for its water quality because it travels through the city’s center and several settlements, highly populated housing areas, and slums. The growth of algae and macrophytes, or aquatic plants, is dependent on the nutrients in the streams. These plants serve as major food sources for fish and other small invertebrates. This study aimed to describe the distribution of nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River, DKI Jakarta, in terms of both space and time. Water quality was monitored under rainy (February and June 2021) and dry (August and September 2021) conditions. The research area, which included 18 observation stations, was situated in the DKI Jakarta sector along the Ciliwung River. Geographically, all river regions’ concentrations of total nitrogen, nitrate, and total phosphate exceeded the quality criteria; however, ammonia and nitrite tended to be high and did not meet norms across the Ciliwung River area, DKI Jakarta. While ammonia concentrations were greater during the dry season and nitrate concentrations were higher during the rainy season, there was a temporary difference in the concentrations of nitrite, total nitrogen, and total phosphate between the seasons.


Introduction
Thirteen river systems run through the DKI Jakarta area, the majority of which originate in the West Java region and flow into Jakarta Bay.Hence, the river in DKI Jakarta is where these wastes are ultimately discharged.The DKI Jakarta region's water quality is declining and requires immediate care.Groundwater and river water both have significant levels of organic and inorganic contaminants, according to monitoring of 13 rivers that traverse the Jakarta region by the Regional Environmental Control Service of DKI Jakarta (BPLHD).The largest river in Jakarta is the Ciliwung River, which is 119 km long and covers a watershed area of 476 km 2 .It flows from upstream of Bogor Regency and crosses Bogor City, Depok City, and Jakarta, finally reaching the Java Sea through Jakarta Bay [1,2].The Ciliwung River passes through many settlements, densely populated housing, and slums, and therefore needs special treatment for the water quality of the river.This river is also considered the river most severely polluted by domestic waste compared to other rivers in Jakarta [3].
Bogor Regency, Bogor City, Depok City, and Jakarta City are among the six successive administrative segments that make up the Ciliwung watershed [4].As a result of the introduction of 1328 (2024) 012005 IOP Publishing doi:10.1088/1755-1315/1328/1/012005 2 several types of pollutants, including household, industrial, and agricultural wastes, increased human activity has resulted in declining water quality [5].The Ciliwung River is an open environment with a variety of pollutant sources, including home, industrial, animal, and agricultural waste, which add to the river's pollution burden [6].The value of the river pollution load depends on the spatial pattern or land use along the river [7].The condition of the Ciliwung River in DKI Jakarta has also worsened due to rapid development that causes waste to increase [8].Changes in land use from agriculture to urban areas also affect water quality [2].These factors have led to significant water quality degradation in the Ciliwung River.
Aprilia et al. [9] indicated that the Ciliwung River in the DKI Jakarta segment is moderately to extremely polluted, with parameters that did not meet the class II quality standard, including dissolved oxygen, total dissolved solids, total suspended solids, total nitrogen, ammonia, nitrite, chemical oxygen demand, biochemical oxygen demand, total coliform, and fecal coliform.At any time of the year, highly variable water conditions lead to variations in pollution levels.Water pollution is defined as the introduction or inclusion of live organisms, materials, energy, and/or other components into water by human activity, surpassing established water quality requirements (Government Regulation of the Republic of Indonesia Number 22 of 2021).Water quality refers to the characteristics of water that can be evaluated using various criteria (physics, chemistry, and biology).To maintain water availability, river water quality is a critical component of environmental management and sustainable development.The maintenance of water functions to fulfill quality criteria in accordance with their designation can be used to manage the quality of river water [10].
Algae and other plants require nutrients such as phosphorus and nitrogen to flourish.However, excessive nutrient concentrations may overstimulate the development of algae and aquatic plants.Eutrophication, or the loss of oxygen in fish and other invertebrates, is a result of bacterial breakdown of organic respiration, which can deplete dissolved oxygen [1].The goal of this study was to describe the distribution of nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River in DKI Jakarta Province in terms of both space and time.To safeguard priceless freshwater resources, a program to monitor nutrients in rivers is required.

Time, place, and water sampling analysis
Water samples were taken four times a year from each observation site in this study, in February and June 2021 (the rainy season) and August and September 2021 (the dry season).The research location was situated in DKI Jakarta along the Ciliwung River.Eighteen observation sites provided water sample data.The research area and observation stations are depicted in Figure 1, and the observation station coordinates are shown in Table 1.The site was selected in accordance with SNI 6989.57:2008concerning Surface Water Sampling Methods, which outlines the general site selection criteria, including the location of water entry points into reservoirs, lakes, and the sea, as well as natural and contaminated water sources.Water quality monitoring of the Ciliwung River in the Jakarta segment was conducted by the Environmental Agency of DKI Jakarta (DLH DKI Jakarta) in collaboration with the Environmental Research Center of IPB University (PPLH IPB).The ammonia analysis procedure uses segmented flow analysis [11], nitrite refers to SNI 06-6989.9-2004,nitrate refers to SNI 6989.79:2011,total nitrogen by persulfate digestion method [11], and total phosphate refers to SNI 06-2483-1991.

Spatial and temporal distribution of nutrients
Mapping was performed to determine the geographical distribution of nutrients in the Ciliwung River.Using ArcMap 10.8, the Inverse Distance Weighting (IDW) approach was used to assess spatial distribution mapping.Using data from nearby locations, this deterministic interpolation approach seeks to estimate or anticipate an unsampled location value [12].The examination of temporal distribution was performed using Microsoft Excel 2013.The time distribution of dissolved oxygen was compared to the Class II river water quality standards found in Attachment VI of the Government Regulation of the Republic of Indonesia Number 22 of 2021 (water designated for freshwater fish farming, animal husbandry, irrigation, and/or other water uses requiring the same water quality).This is because, in accordance with Republic of Indonesia Number 22 of 2021 Article 527 letter f, class II water quality standards should be used if the national or regional government has not established a standard for the most recent quality of surface water bodies.Using Minitab 20 software and a one-way Analysis of Variance (ANOVA) with a 95% significance threshold, the impact of the seasons was ascertained.The mean for a single dependent variable was compared between two or more groups using one-way ANOVA.A minimum of one independent variable (season in this study) and one dependent variable (nutrients) were needed for a one-way ANOVA test.If there were at least 30 data points, it was presumed that the data were regularly distributed.The fact that there are 36 data points from both seasons indicates that the study complied with the standards.To lessen the chance of mistake in failing to reject the null hypothesis (failing to show a statistically significant difference), 30 data points is the minimum required [13].

Results and Discussion
Anthropogenic activities along rivers are assumed to be closely associated with variations in the geographical distribution of nutrients.The state of water quality can be impacted by human activity near rivers, as stated by Sudarso et al. [14].The Ciliwung River's surrounding businesses, plantations, leaching of rubbish mounds, traditional markets, and farmland all contribute to anthropogenic activities.The introduction of biodegradable organic waste and mercury metal pollution into the waterways was the primary reason for the Ciliwung River's declining water quality, according to studies by Sudarso et al. [14].
Both industrial and domestic processes, as well as natural sources, can contribute to the existence of organic materials.There are two categories of domestic wastewater: washing water (containing soap, detergent, oil, and grease) and latrine water (containing urine and feces).Microorganisms, suspended and dissolved organic materials, and inorganic elements are all present in wastewater [15].Surface water runoff and industrial and residential sewage pipelines are sources of pollutant load input (as non-point source pollution).This idea is corroborated by Yudo [16], who discovered a number of tiny and homebased businesses that contaminate the Ciliwung River, including motorbike welding shops, batik dyeing, printing, tofu, and tempeh production.
The nutrient distributions from 18 observation locations during the wet and dry seasons are shown in Figures 2-7.The mean nutrient concentration values for each sample station are displayed.In terms of location, Station 4-2 (Pademangan, North Jakarta) during the wet season (Figure 2) and Station 2-1 (Menteng, Central Jakarta) during the dry season (Figure 3) had the greatest concentration of dissolved inorganic nitrogen (DIN).Station 2-1 (Menteng, Central Jakarta) in the dry season (Figure 5) and Station 5-1 (Pademangan, North Jakarta) in the wet season (Figure 4) had the highest total nitrogen content.1-5 (Tebet, South Jakarta) during the rainy season (Figure 6) and Stations 1-1 (Cimanggis, Depok) during the dry season (Figure 7) had the highest total phosphate concentrations.
Both organic and inorganic nitrogen make up the total nitrogen in water [17].Ammonia, nitrite, and nitrate are the sole components of dissolved inorganic nitrogen (DIN), as is often known [18].Stations 2-1 (Menteng, Central Jakarta) and 4-2 (Pademangan, North Jakarta) had the highest quantities of dissolved inorganic nitrogen (Figures 2 and 3).Stations 2-1 (Menteng, Central Jakarta) and 5-1 (Pademangan, North Jakarta) had the highest quantities of total nitrogen (Figures 4 and 5).The state of the observation station is assumed to be the reason for this.This observation indicates that Station 2-1, which is close to the highway, has water conditions that visibly indicate the existence of an oil layer and organic materials, such as the remaining dried leaves on the water surface.Station 4-2 is close to residential areas, and at Station 5-1 there is a drainpipe from the restaurant that flows directly into the water body.Residential settlements contribute to the input of domestic waste in the form of nitrogen into waters.
While the quantity of nitrate during the investigation was still below the class II river water quality level, the concentrations of ammonia and nitrite were frequently high and above the quality limit.However, overall nitrate concentrations were still greater than nitrite and ammonia concentrations.In aquatic environments, nitrogen molecules such as ammonia, nitrites, and nitrates may readily reach dangerous levels.Ammonia is the most poisonous of the three and is typically a by-product of protein metabolism.These substances are limiting variables that affect the ability of aquatic organisms to develop and maintain good health [19].The significant amount of organic materials that enter the water body is the reason for the high ammonia concentration [20].High levels of readily soluble nitrogen are seen in urine; however, this nitrogen quickly depletes and becomes ammonia [21].
In aquatic environments, increasing nitrite content is a significant issue [22].The nitrogen that has been partially oxidized is called nitrite.Season, temperature, and precipitation all affect the amount of nitrite in the water.Aquatic organisms experience acute toxicity and tissue damage when nitrite concentrations are elevated [23].The primary nitrogen generated from nitrification is nitrate; however, compared to ammonia and nitrite, nitrate is generally not thought to be deadly hazardous to aquatic species [24].However, because nitrate is the last by-product of nitrification, it is usually present in considerably larger amounts than ammonia and nitrites [25].
Low dissolved oxygen concentrations and high BOD5 and COD concentrations resulting from the inflow of household garbage into the Ciliwung River, DKI Jakarta, were responsible for the observed high concentrations of ammonia and nitrite [26].High oxygen consumption, significant levels of organic nitrogen, and mineralization of nutrients as a result of the breakdown of organic matter can also result in high concentrations of ammonia and nitrite [27].The breakdown of organic matter produces ammonia and nitrite at a pace that is out of balance with the nitrification process due to low dissolved oxygen content.Nutrient mineralization and organic matter breakdown are not facilitated by the amount of oxygen present in the water.Thus, the water becomes more nitrate-and ammonia-rich [28].
Stations 1-1 (Cimanggis, Depok) and 1-5 (Tebet, South Jakarta) had the highest amounts of total phosphate (Figures 6 and 7).However, its concentration was still below the quality requirement at all stations.It is believed that the circumstances during water sampling and the features of the stations are connected to the high total phosphate content at Stations 1-1 and 1-5.the.It is believed that P trapped in the sand spreads out and results in high quantities at that station because water sampling at Stations 1-5 took place concurrently with the dredging operation to remove silt, according to field observations.Meanwhile, Station 1-1 is near a number of heavily inhabited areas that could add to the inflow of organic waste, such detergents.Detergents are composed of surfactants, which are fundamental chemicals; phosphate compounds, which are components; and additives, such as bleach and scent, according to Comber et al. [29].P intake into rivers can also originate from runoff, deterioration of organic materials, and residential waste from communities, according to Meirinawati and Muchtar [30].Vinneras et al. [31] reported that human urine contains around 15% to 19% N, 10% to 20% N, 65% P, and 20% to 50% P in feces.
To ascertain the overall temporal distribution pattern of nutrients, station plots were plotted for each river subnetwork.The dry season of August had the highest average ammonia content, which was beyond the quality threshold (Figure 8).Throughout the rainy and dry seasons, there were variations in the concentrations of nitrite and nitrate.Figure 9 shows that the majority of nitrite concentrations surpassed the quality level; however, Figure 10 shows that the nitrate concentration was still below the standard.Even though the study's total nitrogen and total phosphate concentrations varied, they remained below the class II river water quality criterion (Figures 11 and 12).Seasonal variations in the amounts of nitrite, total nitrogen, and total phosphate were observed.During the dry season, ammonia concentrations were greater, while during the rainy season, nitrate concentrations were higher.According to Adrianto [32], the dry season's low rainfall reduces the river water volume, which in turn reduces the river water's capacity to dilute garbage.Nutrients then begin to accumulate as a result, both as dissolved and suspended particles.However, because rains encourage runoff that brings household and agricultural wastes to river bodies, nitrate concentrations are greater during the rainy season than during the dry season [10].The nitrification process also affects variations in the concentration of nitrogen (ammonia, nitrite, and nitrate).If the nitrifying bacteria proliferate well, the nitrification process will proceed as best as possible.The ideal conditions for the development of nitrifying bacteria are 25-35 °C, pH 7.5-8.6,and dissolved oxygen content >1 mg/L [33].Communities beside rivers can have negative effects on riparian aesthetic quality, the physical condition of the landscape, and the quality of river water.Riparian areas naturally link the land and water components of the ecosystem.Apart from offering a range of habitats and operating pathways for species to move through increasingly fragmented urban landscapes, healthy riparian landscapes may also reduce riverbank erosion, filter air pollution, filter surface and subsurface water flow, and more [34].It is believed that irregular settlements are not connected to Wastewater Treatment Plant (WWTP) infrastructure because they typically lack proper sanitation and exhibit irregular architecture [35].As a result, management actions are required to regulate the amount of organic waste and nutrients entering the Ciliwung River in DKI Jakarta.One-way ANOVA was used to compare the means of two or more groups for a single dependent variable in the statistical tests to ascertain the impact of the seasons.According to the results, the ammonia and nitrate parameters displayed significant seasonal variations, but the nitrite, total nitrogen, and total phosphate parameters did not, which were statistically significant at the 95% confidence level (Table 2).Management initiatives that might be recommended include educating the public and MSMEs (Micro, Small, and Medium-Sized Enterprises) on the value of waste management.The socializing and training that takes place might be focused on other uses of wastewater from homes, including irrigation of crops.Additionally, there has to be more oversight of the MSME liquid waste disposal process and regulation of sewage from dwellings to community WWTP.Communal WWTPs are large-scale home wastewater treatment facilities shared by many families, according to Susanthi et al. [36].Monthly performance reviews and monitoring are required following the construction of a community WWTP.

Conclusion
Spatially, the Ciliwung River area in DKI Jakarta does not satisfy the quality criteria for ammonia and nitrite content, which tend to be high.In contrast, the total nitrogen, nitrate, and phosphate contents met the standards for all river sections.Ammonia concentrations were greater during the dry season and nitrate concentrations were greater during the rainy season, whereas nitrite, total nitrogen, and total phosphate concentrations varied only marginally from season to season.

Acknowledgments
The authors express gratitude to the Environmental Research Center of IPB (PPLH IPB) and the Environmental Agency of DKI Jakarta (DLH DKI Jakarta) for their 2021 monitoring of the DKI Jakarta

6 Figure 2 .Figure 3 .
Figure 2. Spatial distribution of DIN during the rainy season

Table 2 .
Statistical test of the effect of season on nutrients