EFFICIENCY OF AN INFILTRATION BASIN IN REMOVING CONTAMINANTS FROM URBAN STORMWATER

The efficiency of a Stormwater Infiltration Basin (SIB) to remove contaminants from urban stormwater was assessed in the current investigation. The SIB, installed in an urban suburb in eastern Sydney (Australia), was monitored over seven rainfall events to assess the removal efficiency of the remedial device for total suspended solids (TSS), nutrients (TP, TKN, N_ox, TN), trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn), organochlorine pesticides and faecal coliforms (FC) from stormwater. The weighted average concentration (WAC) of TSS in the stormwater effluent from the SIB was reduced by an average of 50%, whereas the WAC of Cu, Pb and Zn were also reduced by an average 68%, 93% and 52%, respectively. However, the WAC of Cr, Fe, Mn and Ni displays either similar concentrations as the stormwater influent (Cr and Mn), or substantially higher concentrations (Fe and Ni), due possibly to leaching of fine-grained zeolite clay particles in the filtration bed. The mean removal efficiency of the SIB for total phosphorus (TP) and total Kjeldahl nitrogen (TKN) was 51% and 65%, respectively. In contrast, the average WAC of oxidisable nitrogen (nitrate and nitrite nitrogen or N_ox) is about 2.5 times greater in the effluent (1.34 ± 0.69 mg L^–1) than in the incoming stormwater (0.62 ± 0.25 mg L^–1). The WAC of total nitrogen (TN) was similar for stormwater at the in-flow and out-flow points. The SIB was very efficient in removing FC from stormwater; and the WAC of almost 70 (100 mL)^–1 at inflow was reduced to <2000 cfu (100 Ml)^–1 at the outflow, representing a mean removal efficiency of 96%. Due to the low concentrations of Cd, organochlorine pesticides and PAHs in the stormwater, it was not possible to assess the efficiency of the SIB in removing these contaminants.     

Temporal and spatial variations of nutrients in the Ten Mile Creek of South Florida, USA and effects on phytoplankton biomass

Water quality throughout south Florida has been a major concern for many years. Nutrient enrichment in the Indian River Lagoon (IRL) is a major surface water issue and is suggested as a possible cause of symptoms of ecological degradation. In 2005-06, water samples were collected weekly from seven sites along Ten Mile Creek (TMC), which drains into the Indian River Lagoon, to investigate and analyze spatial and temporal fluctuations of nutrients nitrogen (N) and phosphorus (P). The objective of this study was to understand the relationships among chlorophyll a concentration, nutrient enrichment and hydrological parameters in the surface water body.High median concentrations of total P (TP, 0.272 mg L(-1)), PO4-P (0.122 mg L(-1)), and dissolved total P (DTP, 0.179 mg L(-1)); and total N (TN, 0.988 mg L(-1)), NO3(-)-N (0.104 mg L(-1)), NH4+-N (0.103 mg L(-1)), and total Kjeldahl N (TKN, 0.829 mg L(-1)), were measured in TMC. The concentrations of TP, PO4-P, DTP, TN, NO3(-)-N, NH4+-N, and TKN were higher in summer and fall than in winter and spring. However, chlorophyll a and pheophytin concentrations during this period in TMC varied in the range of 0.000-60.7 and 0.000-17.4 microg L(-1), with their median values of 3.54 and 3.02 microg L(-1), respectively. The greatest mean chlorophyll a (10.3 microg L(-1)) and pheophytin (5.71 microg L(-1)) concentrations occurred in spring, while the lowest chlorophyll a (1.49 microg L(-1)) and pheophytin (1.97 mug L(-1)) in fall. High concentrations of PO4-P (>0.16 mg L(-1)), DTP (>0.24 mg L(-1)), NO3(-)-N (>0.15 mg L(-1)), NH4+-N (>0.12 mg L(-1)), and TKN (>0.96 mg L(-1)), occurred in the upstream of TMC, while high concentrations of chlorophyll a (>6.8 mug L(-l)) and pheophytin (>3.9 microg L(-l)) were detected in the downstream of TMC. The highest chlorophyll a (11.8 mug L(-l)) and pheophytin (6.06 microg L(-l)) concentrations, however, were associated with static and open water conditions. Hydrological parameters (total dissolved solid, electrical conductivity, salinity, pH, and water temperature) were positively correlated with chlorophyll a and pheophytin concentrations (P < 0.01) and these factors overshadowed the relationships between N and P concentrations and chlorophyll a under field conditions. Principal component analysis and the ratios of DIN/DP and TN/TP in the water suggest that N is the limiting nutrient factor for phytoplankton growth in the TMC and elevated N relative to P is beneficial to the growth of phytoplankton, which is supported by laboratory culture experiments under controlled conditions.     

太湖氮磷大气干湿沉降时空特征

为了探索太湖氮磷营养盐干湿沉降特征及对太湖营养盐输入的贡献,于2011年不同季节采集太湖不同位点的大气干湿沉降样品,分析干湿沉降中氮（N）和磷（P）的形态和沉降量。研究结果表明,输入太湖的磷以干沉降为主,而氮以湿沉降为主。在太湖干沉降中总无机氮（TIN）占总氮（TN）的77.1%,溶解性磷（DIP）占总磷（TP）的77.9%。干沉降中TIN主要以NH+4-N为主。西太湖是TN与TP通过大气干湿沉降输入太湖的最高湖区。太湖全年大气TN沉降总量为20 978 t,TP沉降总量为1 268 t,因此,氮磷大气干湿沉降是太湖营养盐输入的重要来源之一。     

Assessment Of A Natural Wetland For Use In Wastewater Remediation

An environmental study was conducted to assess various aspects of the water and sediment quality of a natural wetland to determine its feasibility for advanced wastewater treatment in Louisiana. Nitrate (NO₃), nitrite (NO₂), ammonia (NH₄), total Kjeldahl nitrogen (TKN), total phosphorus, chloride, total organic carbon, pH, trace metals, fecal coliform, dissolved oxygen (DO), and biochemical oxygen demand (BOD) were monitored. Productivity of a dominant shrub, Iva frutescens, in the wetland was also assessed. Research results indicated that gradients of chloride and salinity concentrations showed a broad mixing of the discharged fresh water into the more saline natural brackish waters. This provided an ideal pattern for nutrient assimilation by the receiving marsh. NH₄ was reduced in the range of 50–100% when all combinations of sources and outflows were considered. For total phosphorus and TKN, reduction ranged from 0–95.1% and 11.2–89.7%, respectively. Some nutrient concentrations in the effluent outlet, NO₃ in particular, were lower than background concentrations found in the reference wetland. Sediment and water showed no significant deficiency or toxicity problems for the major nutrients and metals analyzed. The secondary effluent discharges had little demonstrable negative impact on the wetland during the study period from 1995 to 1996.     

Bioavailable phosphorus transport from a hillslope cropland of purple soil under natural and simulated rainfall

To further understand the mechanism of bioavailable total P (BAP) and bioavailable dissolved P (BDP) transport by overland and subsurface flow, we exposed a runoff plot 4.5 m long × 1.5 m wide × 0.6 m deep to simulated and natural rainfall in order to study the effects of rainfall type, rainfall intensity, and vegetation cover on BAP and BDP transport. The results showed that vegetation cover could alleviate the discharge of overland flow and sediment transport and enhance subsurface flow. BAP transport significantly increased with elevated rainfall intensity. Vegetation cover reduced the BAP transport by overland flow and increased it by subsurface flow. BDP transport showed no significant relationship with vegetation cover and rainfall type. The bioavailable particulate P (BPP) transport by overland flow contributed to no less than 90% by weight of total BAP, and the BPP transport by subsurface flow contributed to no less than 60% by weight of total BAP. Short-time heavy rainfall caused more BAP transport and accelerated non-point source pollution.     

Load estimation and source apportionment of nonpoint source nitrogen and phosphorus based on integrated application of SLURP model, ECM, and RUSLE: a case study in the Jinjiang River, China

The nonpoint source (NPS) pollution is difficult to manage and control due to its complicated generation and formation. Load estimation and source apportionment are an important and necessary process for efficient NPS control. Here, an integrated application of semi-distributed land use-based runoff process (SLURP) model, export coefficients model (ECM), and revise universal soil loss equation (RUSLE) for the load estimation and source apportionment of nitrogen and phosphorus was proposed. The Jinjiang River (China) was chosen for the evaluation of the method proposed here. The chosen watershed was divided into 27 subbasins. After which, the SLURP model was used to calculate land use runoff and to estimate loads of dissolved nitrogen and phosphorus, and ECM was applied to estimate dissolved loads from livestock and rural domestic sewage. Next, the RUSLE was employed for load estimation of adsorbed nitrogen and phosphorus. The results showed that the 12,029.06 t?a^?1 pollution loads of total NPS nitrogen (TN) mainly originated from dissolved nitrogen (96.24 %). The major sources of TN were land use runoff, which accounted for 45.97 % of the total, followed by livestock (32.43 %) and rural domestic sewage (17.83 %). For total NPS phosphorous (TP), its pollution loads were 570.82 t?a^?1 and made up of dissolved and adsorbed phosphorous with 66.29 and 33.71 % respectively. Soil erosion, land use runoff, rural domestic sewage, and livestock were the main sources of phosphorus with contribution ratios of 33.71, 45.73, 14.32, and 6.24 % respectively. Therefore, land use runoff, livestock, and soil erosion were identified as the main pollution sources to influence loads of NPS nitrogen and phosphorus in the Jinjiang River and should be controlled first. The method developed here provided a helpful guideline for conducting NPS pollution management in similar watershed.     

淀山湖总氮和总磷的时空模拟分布

为了解氮磷在淀山湖的时空分布特征及变化规律,运用ELCOM-CAEDYM耦合模块分析了2008年淀山湖总氮和总磷浓度的时空变异。研究表明:模型较好地模拟了淀山湖上覆水中的总氮、总磷的时空分布,总氮、总磷质量浓度总体变化趋势与实测值相一致。淀山湖春冬季总氮的质量浓度要明显高于夏秋季,3月份是淀山湖总氮质量浓度最高的时候,千墩港是淀山湖总氮质量浓度最高的区域。淀山湖总磷的分布并未表现出季节上的规律性,空间分布整体呈现北高南低的趋势。     

Water quality trends in Polyphytos reservoir, Aliakmon River, Greece

A water quality monitoring program was undertaken from June 2004 to May 2005, on a monthly basis, in Polyphytos Reservoir of Aliakmon River. Depth, water temperature, dissolved oxygen, conductivity, pH and transparency (Secchi disk) were measured in situ, while collected water samples were analyzed in the laboratory for the determination of BOD, COD, total phosphorus (TP), ortho-phosphate (OP), chlorophyll-a (Chl-a), ammonium, nitrite and nitrate, total Kappajeldahl nitrogen (TKN) and heavy metals (Fe, Mn, Cu, Cr, Pb, Ni and Cd). Measured concentrations were compared to those from two previous studies conducted in July 1987 to June 1988 and January 1991 to February 1993. The following conclusions are drawn: the effect of the watershed on the lake environment, mostly through Aliakmon River, is significant, and it accelerates the eutrophication of the lake. The anoxic zones, which were defined in the lake, reinforce this conclusion. Nitrate, nitrite and ammonia were measured at lower concentrations compared to previous studies, while total phosphorus and chlorophyll-a were found at increased concentrations. The current trophic state of Polyphytos reservoir is eutrophic, based on the OECD method and Carlson's Trophic State Indices (TSI). The concentration of BOD and COD ranged at low levels. Furthermore, the mean concentrations of metals Fe, Mn, Cu, Cr, Pb, and Cd were below the potable water standards set by WHO and EU. During most part of the study period the ratio N/P for Polyphytos reservoir was higher than 7.2:1, and therefore, phosphorus is the limiting nutrient for algal growth.     

From lake to estuary,the tale of two waters: a study of aquatic continuum biogeochemistry

The balance of fresh and saline water is essential to estuarine ecosystem function. Along the fresh-brackish-saline water gradient within the C-43 canal/Caloosahatchee River Estuary (CRE), the quantity, timing and distribution of water, and associated water quality significantly influence ecosystem function. Long-term trends of water quality and quantity were assessed from Lake Okeechobee to the CRE between May 1978 and April 2016. Significant changes to monthly flow volumes were detected between the lake and the estuary which correspond to changes in upstream management. and climatic events. Across the 37-year period, total phosphorus (TP) flow-weighted mean (FWM) concentration significantly increased at the lake; meanwhile, total nitrogen (TN) FMW concentrations significantly declined at both the lake and estuary headwaters. Between May 1999 and April 2016, TN, TP, and total organic carbon (TOC), ortho-P, and ammonium conditions were assessed within the estuary at several monitoring locations. Generally, nutrient concentrations decreased from upstream to downstream with shifts in TN/TP from values >?20 in the freshwater portion, ~?20 in the estuarine portion, and <?20 in the marine portion indicating a spatial shift in nutrient limitations along the continuum. Aquatic productivity analysis suggests that the estuary is net heterotrophic with productivity being negatively influenced by TP, TN, and TOC likely due to a combination of effects including shading by high color dissolved organic matter. We conclude that rainfall patterns, land use, and the resulting discharges of runoff drive the ecology of the C-43/CRE aquatic continuum and associated biogeochemistry rather than water management associated with Lake Okeechobee.     

Spatial and temporal patterns of dissolved nitrogen and phosphorus in surface waters of a multi-land use basin

Research on relationships between dissolved nutrients and land-use at the watershed scale is a high priority for protecting surface water quality. We measured dissolved nitrogen (DN) and ortho-phosphorus (P) along 130 km of the Calapooia River (Oregon, USA) and 44 of its sub-basins for 3 years to test for associations with land-use. Nutrient concentrations were analyzed for spatial and seasonal patterns and for relationships with land-use and stream discharge. Ortho-P and DN were higher in lower-elevation sub-basins dominated by poorly drained soils and agricultural production compared with higher-elevation sub-basins dominated by well-drained soils and forests. Eight lower basins had at least one sample period with nitrate-N?>?10 mg L^?1. The Calapooia River had lower concentrations of dissolved nutrients compared with lower sub-basins, often by an order of magnitude. Dissolved organic N represented a greater proportion of DN in the upper forested sub-basins. Seasonal nutrient concentrations had strong positive correlations to the percent of a sub-basin that was managed for agriculture in all seasons (p?values?≤?0.019) except summer. Results suggest that agricultural lands are contributing to stream nutrient concentrations. However, poorly drained soils in agricultural areas may also contribute to the strong relationships that we found between dissolved nutrients and agriculture.     

Nonpoint source pollution loading from an undistributed tropic forest area

Water quality and unit nonpoint sources (NPS) pollution load from a forest area were studied in a mountainous watershed in Taiwan. The flow rates were measured with rectangular weirs and samples taken for water quality analysis in both non-rainy and rainy days for 2 years. The subroutine of the Hydrological Simulation Program--FORTRAN was used to simulate runoff for additional 3 years. Total annual loads of various water quality parameters were then estimated by a regression model. Most of the parameter concentrations are higher during the rainy days; their values are typically higher as compared to data from other undisturbed forest areas. Nevertheless, the concentration ratio of dissolved inorganic nitrogen to TN or PO4(3-) -P to TP shows TN or TP no correlations with the flow rates, whereas the concentrations of SS and TP are positively correlated with the flow rate. The fluctuation of annual load from this watershed is significant. For example, six major events of the entire year, for which the total duration is merely 6.4 days, contribute 42% of the annual precipitation and at least 40% of the annual NPS loads. The management for controlling the NPS pollution from this forest watershed is discussed.     

Multivariate analyses of the effect of an urban wastewater treatment plant on spatial and temporal variation of water quality and nutrient distribution of a tropical mid-order river

Freshwater resources are increasingly scarce due to human activities, and the understanding of water quality variations at different spatial and temporal scales is necessary for adequate management. Here, we analyze the hypotheses that (1) the presence of a wastewater treatment plant (WWTP) and (2) a polluted tributary that drains downstream from the WWTP change the spatial patterns of physicochemical variables (pH, turbidity, dissolved oxygen, and electrical conductivity) and nutrient concentrations (reactive soluble phosphorus, total phosphorus, nitrogen series, total nitrogen, and total dissolved carbon) along a mid-order river in SE Brazil and that these effects depend on rainfall regime. Six study sites were sampled along almost 4 years to evaluate the impacts of human activities, including sites upstream (1–3) and downstream (5–6) from the WWTP. The impacts were observed presenting an increasing trend from the source (site 1) towards Água Quente stream (site 4, the polluted tributary), with signs of attenuation at site 5 (downstream from both WWTP and site 4) and the river mouth (site 6). Input of nutrients by rural and urban runoff was observed mainly at sites 2 and 3, respectively. At sites 4 and 5, the inputs of both untreated and treated wastewaters increased nutrient concentrations and changed physicochemical variables, with significant impacts to Monjolinho River. Seasonal variations in the measured values were also observed, in agreement with the pluviometric indexes of the region. Univariate analyses suggested no effect of the WWTP for most variables, with continued impacts at sites downstream, but non-parametric multivariate analysis indicated that these sites were recovering to chemical characteristics similar to upstream sites, apparently due to autodepuration. Therefore, multivariate methods that allow rigorous tests of multifactor hypotheses can greatly contribute to determine effects of both point and non-point sources in river systems, thus contributing to freshwater monitoring and management.     

Response of algal metrics to nutrients and physical factors and identification of nutrient thresholds in agricultural streams

Many streams within the United States are impaired due to nutrient enrichment, particularly in agricultural settings. The present study examines the response of benthic algal communities in agricultural and minimally disturbed sites from across the western United States to a suite of environmental factors, including nutrients, collected at multiple scales. The first objective was to identify the relative importance of nutrients, habitat and watershed features, and macroinvertebrate trophic structure to explain algal metrics derived from deposition and erosion habitats. The second objective was to determine if thresholds in total nitrogen (TN) and total phosphorus (TP) related to algal metrics could be identified and how these thresholds varied across metrics and habitats. Nutrient concentrations within the agricultural areas were elevated and greater than published threshold values. All algal metrics examined responded to nutrients as hypothesized. Although nutrients typically were the most important variables in explaining the variation in each of the algal metrics, environmental factors operating at multiple scales also were important. Calculated thresholds for TN or TP based on the algal metrics generated from samples collected from erosion and deposition habitats were not significantly different. Little variability in threshold values for each metric for TN and TP was observed. The consistency of the threshold values measured across multiple metrics and habitats suggest that the thresholds identified in this study are ecologically relevant. Additional work to characterize the relationship between algal metrics, physical and chemical features, and nuisance algal growth would be of benefit to the development of nutrient thresholds and criteria.     

Stream water nutrient enrichment in a mixed-use watershed

Eutrophic conditions, in both saline and freshwater systems, result from nutrient export from upstream watersheds. The objective of this study was to quantify the surface runoff losses of nitrate-nitrogen (NO?-N), total nitrogen (TN), dissolved reactive phosphorus (DRP), and total phosphorus (TP) resulting from prevailing practices on a managed golf course. Inflow and outflow discharge waters on a sub-area of Northland Country Club (NCC) located in Duluth, Minnesota were measured for both quantity and quality from April through November from 2003 to 2008. Nutrient losses were detectable throughout the year, had a seasonal trend, and routinely exceeded recommended levels to minimize eutrophication. The median outflow TN concentration (1.04 mg L?1) was significantly greater (p < 0.05) than the median inflow (0.81 mg L?1) concentration. Similarly, the median outflow TP concentration (0.03 mg L?1) was significantly greater (p < 0.05) than the median inflow concentration (0.02 mg L?1). Maximum recorded concentrations during the study period were 1.9 mg L?1 NO?-N, 3.93 mg L?1 TN, 0.34 mg L?1 DRP, and 1.11 mg L?1 TP. Mean annual export coefficients at NCC were 0.7 kg ha?1 NO?-N (1.7% of applied), 4.43 kg ha?1 TN (10.7% of applied), 0.14 kg ha?1 DRP (2.6% of applied), and 0.25 kg ha?1 TP (4.6% of applied). The findings of this study highlight the need for adopting conservation practices aimed at reducing offsite nutrient transport.     

Evaluation of preservation methods for nutrient species collected by automatic samplers

Automatic samplers are a common method of data collection for numerous monitoring projects in the South Florida region and elsewhere. Although total phosphorus (TP) is the primary parameter of interest within this region, nitrogen species such as ammonia nitrogen (NH₄-N), nitrate+nitrite nitrogen (NO_x-N), and total kjeldahl nitrogen (TKN) are also collected and analyzed. Federal and state quality assurance guidelines require nutrient samples to be preserved by acidification with H₂SO₄ to a pH < 2 and stored immediately at 4 °C. However, the remoteness of manysampling locations in South Florida makes it difficult to supplyelectricity for the refrigeration of samples collected by autosamplers. In addition, the use of propane-powered refrigerated autosamplers is a costly and ineffective solution in the South Florida climate. Consequently, while samples collected at these remote locations are routinely pre-preservedwith acid, they are not cooled to 4 °C for a period fromone to seven days. This study evaluated if a statistically significant difference ( = 0.05) existed between concentrations of nitrogen species from a common source samplethat was either: processed immediately; refrigerated to 4 °C for seven days; or not refrigerated for seven days.In all cases, the collected sample was pre-preserved by adding 1 mL of 50% H₂SO₄ to each 1 L discrete sample container before each 7 day testing period. Differences in concentrations of the calculated parameter total nitrogen (TN)were also investigated.Analyses using the Wilcoxon Signed-Rank Test showed no significant differences among the three treatment groups for NO_x-N, TKN, TN and TP. Significant differences were observedwhen the NH₄-N samples that were processed immediately werepaired with NH₄-N samples that were left unrefrigerated or refrigerated for seven days. Information from this study can be used by researchers and managers in evaluating the usefulness of nutrient water quality data that is collected when sample refrigeration is not available.     

Nutrients in the Changjiang River

N, P and SiO3-Si in the Changjiang mainstream and its major tributaries and lakes were investigated in the dry season from November to December, 1997, and in the flood season in August and October, 1998. An even distribution of SiO3-Si was found along the Changjiang River. However, the concentrations of total nitrogen, total dissolved nitrogen, dissolved inorganic nitrogen, nitrate and total phosphorus, total particulate phosphorus increased notably in the upper reaches, which reflected an increasing impact from human activities. Those concentrations in the middle and lower reaches of the Changjiang River were relatively constant. Dissolved N was the major form of N and the particulate P was the major form of P in the Changjiang River. The molar ratio of dissolved N to dissolved P was extremely high (192.5-317.5), while that of the particulate form was low (5.6-37.7). High N/P ratio reflected a significant input of anthropogenic N such as N from precipitation and N lost from water and soil etc. Dissolved N and P was in a quasi-equilibrium state in the process from precipitate to the river. In the turbid river water, light limitation, rather than P limitation, seemed more likely to be a controlling factor for the growth of phytoplankton. A positive linear correlationship between the concentration of dissolved N and the river's runoff was found, mainly in the upper reaches, which was related to the non-point sources of N. Over the past decades, N concentration has greatly increased, but the change of P concentration was not as significant as N. The nutrient fluxes of the Changjiang mainstream and tributaries were estimated, and the result showed that the nutrient fluxes were mainly controlled by the runoff, of which more than a half came from the tributaries. These investigations carried out before water storage of the Three Gorges Dam will supply a scientific base for studying the influences of the Three Gorges Dam on the ecology and environment of the Changjiang River and its estuary.     

Assessing BMP effectiveness: multiprocedure analysis of observed water quality data

Observed water quality data obtained from eight stream monitoring locations within Richland–Chambers Watershed in north central Texas were analyzed for trends using box-and-whisker plots, exceedance probability plots, and linear and Mann–Kendall statistical methods. Total suspended solids decreased at seven out of eight stations, and at two of these stations, the decrease was significant. Mixed results were obtained for nitrogen across the stations. A nonsignificant and significant increase in nitrite plus nitrate nitrogen (nitrite + nitrate N) was noticed in two stations each, whereas at the other four stations showed nonsignificant decrease. The results of organic nitrogen (Org N) was similar to nitrite + nitrate N except that the two stations that showed significant increase in nitrite + nitrate N showed nonsignificant decrease in Org N. Mixed results were also noticed for orthophosphorus (Ortho P) including nonsignificant decrease at two stations, significant decrease and increase at one station each, and nonsignificant increase in four stations. In general, total phosphorus (TP) decreased at all stations, significantly at some, except one station where it increased significantly. Decreasing trends in sediment, Org N, Ortho P, and TP were likely related to implementation of best management practices (BMPs). Increasing trends in dissolved constituents including Ortho P and nitrite + nitrate N were likely due to increased surface residue as a result of some BMPs such as conservation tillage.     

Identification of spatiotemporal nutrient patterns in a coastal bay via an integrated k-means clustering and gravity model

This study presents an integrated k-means clustering and gravity model (IKCGM) for investigating the spatiotemporal patterns of nutrient and associated dissolved oxygen levels in Tampa Bay, Florida. By using a k-means clustering analysis to first partition the nutrient data into a user-specified number of subsets, it is possible to discover the spatiotemporal patterns of nutrient distribution in the bay and capture the inherent linkages of hydrodynamic and biogeochemical features. Such patterns may then be combined with a gravity model to link the nutrient source contribution from each coastal watershed to the generated clusters in the bay to aid in the source proportion analysis for environmental management. The clustering analysis was carried out based on 1 year (2008) water quality data composed of 55 sample stations throughout Tampa Bay collected by the Environmental Protection Commission of Hillsborough County. In addition, hydrological and river water quality data of the same year were acquired from the United States Geological Survey's National Water Information System to support the gravity modeling analysis. The results show that the k-means model with 8 clusters is the optimal choice, in which cluster 2 at Lower Tampa Bay had the minimum values of total nitrogen (TN) concentrations, chlorophyll a (Chl-a) concentrations, and ocean color values in every season as well as the minimum concentration of total phosphorus (TP) in three consecutive seasons in 2008. The datasets indicate that Lower Tampa Bay is an area with limited nutrient input throughout the year. Cluster 5, located in Middle Tampa Bay, displayed elevated TN concentrations, ocean color values, and Chl-a concentrations, suggesting that high values of colored dissolved organic matter are linked with some nutrient sources. The data presented by the gravity modeling analysis indicate that the Alafia River Basin is the major contributor of nutrients in terms of both TP and TN values in all seasons. With this new integration, improvements for environmental monitoring and assessment were achieved to advance our understanding of sea-land interactions and nutrient cycling in a critical coastal bay, the Gulf of Mexico.     

The temporal changes in road stormwater runoff quality and the implications to first flush control in Chongqing, China

This study investigates the quality of stormwater runoff from a driveway in the southwest mountainous urban area of Chongqing, China, from 2010 to 2011. The results showed that the mean concentrations of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) were 4.1, 2.4, and 2.2 times the grade V levels of the national surface water standard of China. The pollutant concentration peak preceded or synchronized with the rainfall intensity peak and occurred 10 min after the runoff started. The significant high pollutant concentration in the initial stage of the rainfall suggested that first flush control is necessary, especially for the most polluted constitutes, such as total suspended solids, COD, and TN. Three potential pollution sources were identified: the atmospheric dry and wet deposition (TN, NO₃ ^?-N, NH₄ ⁺-N, and DCu), the road sediment and materials (total suspended solids, COD, and TP), and the vehicle emissions (DPb and DZn). Therefore, this study indicates that reductions in road sediments and material pollution and dry and wet deposition should be the priority factors for pollution control of road stormwater runoff in mountainous urban areas.     

Natural background concentrations of nutrients in the German Bight area (North Sea)

Natural background concentrations of nutrients are needed for the assessments of eutrophication processes and their status. Natural background concentrations of total nitrogen (TN) and total phosphorus (TP) were modelled for the rivers discharging into the German Bight and the Rhine considering individual catchment sizes, freshwater flows and soil types. These data were validated by comparison with data from unpolluted rivers. The consistency of modelled and some compiled nutrient concentrations was confirmed by their area-specific load dependency on freshwater discharges. Pristine inorganic nutrient concentrations were deduced from modelled relations to TN and TP in unpolluted rivers. Pristine nutrient gradients between rivers and offshore waters were estimated by linear mixing until a salinity of 32, continued by hyperbolic fits towards recent mean offshore values (salinity 34.5?C35). Based on these gradients and recent mean salinities, maps of pristine surface gradients were plotted for the whole German Bight. Variability was transferred from recent conditions as percentage of standard deviation. Reported historical nutrient data and concentrations from unpolluted rivers, coastal and offshore North Sea waters are discussed concerning their relations to natural background conditions.