Field-derived phosphorus accumulation rates and solid phase speciation in the filter medium of an urban bioretention system.

Soil phosphorous (P) loss and its partition in various pathways may differ depending on water management practices. A study was conducted using large field plots equipped with automatic flow volume measurement and sampling systems over a 5-year period to determine the effectiveness of regular free drainage (RFD) and controlled drainage with sub-irrigation (CDS) for mitigating soil P losses of various forms (dissolved reactive P - DRP, dissolved un-reactive P - DURP, and particulate P - PP) and to identify the relative roles of surface runoff and sub-surface tile drainage in soil P loss. For RFD, flow weighted means (FWM) of DRP, DURP, PP and the total P (TP) concentrations over the 5-yr period were averaged at 0.057, 0.057, 0.627, and 0.741 mg P L-1 in surface runoff water and at 0.034, 0.053, 0.393, and 0.480 mg P L-1 in tile drainage water, respectively. CDS increased FWM of most forms of P and the TP concentrations in surface runoff water, but decreased the FWM of DURP, PP and the TP concentrations in tile drainage water. The CDS produced similar annual TDP loss, the sum of DRP and DURP, but reduced losses of PP by 15% and of TP by12 %, relative to RFD. The PP loss accounted for over 80 % of TP loss for both CDS and RFD. Of the total soil P loss, from 3 to 5 % was accounted for in surface runoff water, while from 95 to 97 % was accounted for in tile drainage water, for RFD. For CDS, from 29 to 35 % of the total soil P loss was in surface runoff water, while 65 to 71% was in tile drainage water. Subsurface tile drainage played predominant role in soil P loss. CDS can be considered as a beneficial management practice to reduce soil P loss.

Nitrogen removal and nitrifying and denitrifying bacteria quantification in a stormwater bioretention system

Phosphorus and its solubility in aerosols from continental and marine sources in the sea areas near China: Results from a 40-day cruise mission in late spring

Removal of nitrogen from rainwater runoff by bioretention cells filled with modified collapsible loess

In tropical lakes relatively little is known about the general relationship between nutrient concentration and phytoplankton biomass. Using data from 192 lakes from tropical and subtropical regions we examine the relationship between total P (TP) and chlorophyll (Chl). The lakes are all located between 30° S to 31° N include systems in Asia, Africa, and North and South America but are dominated by Brazilian (n=79) and subtropical N. American (n=67) systems. The systems vary in morphometry (mean depth and lake area), trophic state as well total N (TN) to total P (TP) ratios and light extinction. Despite a nearly 500-fold range in TP concentrations (2–970 µg P l−1), there was a poorer relationship between log TP and log Chl (r 2=0.42) than is generally observed for temperate systems from either narrow or broad geographic regions. N limitation is not a likely explanation for the relatively weak TP-Chl relationship in the tropical-subtropical systems. Systems had high average TN:TP ratios and neither a multiple regression with log TP and log TN nor separating systems with high TN:TP (>17 by weight) improved the predictive power of the log TP-log Chl relationship.

Effective stormwater management is increasingly vital due to climate change impacts, such as intensified rainfall and flooding. Urban expansion, water scarcity, and intensified agriculture demand innovative solutions like Green Stormwater Infrastructure (GSI), including vegetated biofilters, green roofs, wetlands, bioretention systems, and high-rate filtration. These systems, enhanced by natural and engineered filter materials, improve contaminant removal across diverse contexts. Modern practices prioritize retention, infiltration, and groundwater recharge over traditional rapid drainage, reframing stormwater as a resource amid rising extreme weather events. In water-scarce regions, stormwater management offers dual-use potential for drinking and non-drinking applications, addressing freshwater scarcity exacerbated by population growth and climate change. Targeting the “first flush” of pollutants after rainfall allows for more efficient, cost-effective treatment. This paper identifies three key objectives: addressing GSI limitations and exploring new technologies, evaluating treatment train combinations for cost-effective reuse, and advancing urban stormwater treatment research. Various filter media, such as those in green roofs, bioretention systems, and swales, effectively remove pollutants like nutrients, heavy metals, PAHs, and micropollutants. Granular activated carbon (GAC) filters excel at reducing heavy metals and dissolved organic carbon (DOC), with pre-screening via anthracite filters to extend GAC lifespan by trapping sediments and pollutants. Managing emerging contaminants and microplastics remains underexplored and requires further investigation.

Bioretention systems are used to treat stormwater. Using coarser filter media than commonly recommended with high saturated hydraulic conductivities may increase annual runoff volume capture, facilitate smaller filters, less overflow and adaptation to cold winters. However, this may affect water quality treatment negatively. Therefore, we investigated total and dissolved metal treatment at three full scale bioretention systems with a coarse filter material and saturated hydraulic conductivities >1500mm/h in Malmö/Sweden. One bioretention system was designed with a coarse sand-based filter medium, another with coarse sand-based filter medium and a submerged zone and the third with a 50:50 mixture of coarse sand and pumice as filter medium. The study included 19 rain events, partly during winter season when road salt was applied. The results suggest that also filter media with high hydraulic conductivity can be an effective option when metal treatment is targeted. The two systems with coarse sand filter media treated total metals effectively with median removals >80% for Cu, Pb and Zn and median removals >35% for Ni and Cr. Dissolved metal treatment was variable reaching from effective treatment for dissolved Cu, Pb and Zn with median removals >60% to overall leaching of dissolved Cd, Ni and Cr. Applying a submerged zone did not showed benefits for total or dissolved metal removal. Further, treatment of total and partly dissolved metals was significantly impaired due to pumice addition of the filter media, discouraging pumice as a filter media amendment. Coarser filter materials could be recommended for sites with space limitations or when frozen ground is expected in winter. Further, they can generally reduce clogging risks and untreated overflows.

We investigated plastic pollution in soil-based stormwater bioretention systems (BRS), which are potentially important pollutant receptors and pathways. Our integrated study is the first of its kind, focusing on plastic abundance, size fractionation, composition, and interactions with urban metrics (including housing density and auxiliary stormwater treatment infrastructure) in BRS filter media. Our results revealed that mesoplastic (MEP) and microplastic (MP) concentrations in BRS are comparable with those reported in other stormwater systems (e.g. wetlands) as well as soils in other land use areas (e.g. agriculture). Distributional sampling within the BRS revealed MP abundances do not change with horizontal distance from the inlet to the outlet. However, MEP abundances drastically decreased towards the outlet, indicating plastic accumulation within BRS. This is important because MEPs can breakdown into MPs which can affect BRS function as well as mobilise downstream. Yet our data uncovered more complex mechanisms involved in BRS plastic fate, with composition data revealing that MPs are not simply breakdown products of MEPs but are instead derived from different sources. Composition, morphology and colour analysis confirmed that BRS polymer liners are a key source of MPs and MEPs in soil filter media. Multivariate analysis of the data with urban design metrics showed gross pollutant traps are effective at decreasing MP concentrations in BRS but not as effective at controlling MEPs. Our results point to complex plastic transmission and accumulation pathways in BRS. Interception measures can partially alleviate plastic risk, but more work is needed to elucidate plastic long-term fate in BRS.

Broiler breeder manure phosphorus forms are affected by diet, location, and period of accumulation

Suspended solids (SS) are important carriers of pollutants such as phosphorus (P) in streams, but the sampling frequency in monitoring programs is usually insufficiently frequent to capture episodic SS and total P (TP) peaks. The suitability of turbidity and conductivity as a surrogate for SS and TP was studied using 108 monitoring stations located in catchments of different sizes, land uses, and pollution levels. The use of high-frequency turbidity measurements to estimate SS and TP loads was compared with the use of two sampling methods (grab, flow-proportional sampling) in a case study. When all samples were considered, turbidity was a good predictor of SS (r2 = 0.76) and TP (r2 = 0.75). For single sites, there was a large range in how well turbidity could predict the two variables. The site-specific turbidity-SS relationship was significant at 87% of sites (mean r2 = 0.72). The site turbidity and conductivity-TP relationship was significant at 78% of sites (mean r2 = 0.62). A stronger turbidity-SS relationship was found in catchments with a higher percentage of agricultural land. The turbidity and conductivity-TP relationship was stronger when the TP concentration was high. In the case study, TP loads were smallest when estimated with grab sampling, which missed several discharge peaks. Loads estimated with high-frequency turbidity measurements were 19–51% smaller than with flow-proportional sampling, probably due to differences in sampling points. High-frequency turbidity measurements can be a viable alternative to conventional sampling methods in studies on concentration dynamics and load estimates.

Phosphorus (P) fractionation and distribution in sediments are of great concern in the Florida Everglades ecosystem because potential eutrophication of surface waters usually results from P external loading and stability. Intact core sediment samples were collected to a depth of 35 cm from wetlands and canals across Water Conservation Area 3 (WCA‐3) of the Florida Everglades. These sediment cores were sliced into 5 cm increments and analyzed for P contents in different fractions by sequential extraction. These fractions mainly included total P (TP), readily available P (Pi‐KCl), Fe/Al‐bound P (Pi‐NaOH), Ca/Mg‐bound P (Pi‐HCl), organic P (Po‐NaOH), and residual P (PoResidue). Results showed that the canal sediments had the highest concentrations of TP, with about 87% in the form of Ca/Mg‐bound fraction, and the concentrations of TP in these sediments increased with depth. In contrast, the wetland sediments contained the lowest concentrations of TP (predominantly in the organic fraction), with 43% residual P and 27% Po‐NaOH, and the concentrations of TP in these sediments decreased with depth. In addition, a large amount of the readily available P (up to 1500 mg kg−1) in the canal sediments was accumulated at the top layer of 0–5 cm. This study suggests that any disturbance and/or environmental alterations, such as high canal flow and dredging in canal sediments, could pose a potential risk of a P increase in the water column and, consequently, in the wetlands because of the release of readily available P despite the relatively stable nature of such P fractions in these sediments.

Using radiometric tools to track sediment and phosphorus movement in an agricultural watershed

Phosphorus removal of rural wastewater by the paddy-rice-wetland system in Tai Lake Basin

An empirical phosphorus (P) loading model modified from the original Vollenweider formulation has been used since the late 1970s to track progress toward a legally mandated P loading target for Lake Okeechobee, Florida. The loading target is designed to achieve, as an annual average for the pelagic region, a total P (TP) concentration of 40 μg L−1. This TP goal is not based on historic data from the lake, nor on how certain levels of TP might cause use-impairment or ecological harm. Nevertheless, our retrospective analyses indicate that the goal falls within a range of TP concentrations (26 to 92 μg L−1) derived from historical data, pelagic TP-algal bloom relationships, pelagic TP-chlorophyll a relationships, and a Florida lake regression model. When first applied to Lake Okeechobee, the modified Vollenweider model gave accurate estimates of pelagic TP, but now it under-predicts TP by nearly 50 percent. This may reflect time lags in lake responses to recent reductions in P loads, an increase in the relative magnitude of internal vs. external P loads, or a change of in-lake processing of P. The lake's P budget shows a decline over time in the net sedimentation of P. The Vollenweider model estimates P sedimentation based on a fixed empirical relationship using water residence time (τw), a parameter that has not displayed a significant historical trend. Given these issues, it is important to consider whether the existing model is an effective management tool for Lake Okeechobee. Our results indicate that the modified Vollenweider model may suffice as a coarse-scale tool for tracking progress in the eutrophication management program, with a major caveat: model predictions of pelagic TP at any given external loading rate may reflect what is potentially attainable, if internal loading rates decrease to their previous lower levels. A more complex dynamic model is being developed, which accounts for sediment-water P exchanges. The new model should provide more accurate estimates of pelagic TP, as well as estimates of recovery time and predictions of short-term responses to management actions.

Elevated phosphorus (P) concentrations in subsurface drainage water are thought to be the result of P bypassing the soil matrix via macropore flow. The objectives of this study were to quantify event water delivery to tile drains via macropore flow paths during storm events and to determine the effect of tillage practices on event water and P delivery to tiles. Tile discharge, total dissolved P (DP) and total P (TP) concentrations, and stable oxygen and deuterium isotopic signatures were measured from two adjacent tile‐drained fields in Ohio, USA during seven spring storms. Fertilizer was surface‐applied to both fields and disk tillage was used to incorporate the fertilizer on one field while the other remained in no‐till. Median DP concentration in tile discharge prior to fertilizer application was 0.08 mg L−1 in both fields. Following fertilizer application, median DP concentration was significantly greater in the no‐tilled field (1.19 mg L−1) compared to the tilled field (0.66 mg L−1), with concentrations remaining significantly greater in the no‐till field for the remainder of the monitored storms. Both DP and TP concentrations in the no‐till field were significantly related to event water contributions to tile discharge, while only TP concentration was significantly related to event water in the tilled field. Event water accounted for between 26 and 69% of total tile discharge from both fields, but tillage substantially reduced maximum contributions of event water. Collectively, these results suggest that incorporating surface‐applied fertilizers has the potential to substantially reduce the risk of P transport from tile‐drained fields.