Transient Pollution Events Research Articles

Trend Analysis and Spatial Source Attribution of Surface Ozone in Chaozhou, China

Surface ozone (O3), a critical air pollutant, poses significant challenges in urban environments, as exemplified by the city of Chaozhou in southeastern China. This study employs a novel combination of trend analysis and spatial source attribution techniques to evaluate the long-term dynamics of surface ozone and identify its sources. Utilizing the Kolmogorov–Zurbenko (KZ) filter and percentile regression, we analyzed the temporal trends of daily maximum 8 h moving average ozone (MDA8 O3) concentrations from 2014 to 2023. Our analysis revealed a general long-term downward trend in MDA8 O3 values alongside notable monthly fluctuations, with peak concentrations typically occurring in October and April. Additionally, the percentile regression analysis demonstrated a significant downward trend in MDA8 O3 concentrations across nearly all percentiles, with larger decline rates at higher percentiles, highlighting the effectiveness of local and regional O3 management strategies in Chaozhou. The changes in MDA8 O3 concentrations were mainly influenced by the short-term component, contributing 62.2%, while the contribution of the long-term fraction is relatively small. This suggests a significant influence of immediate meteorological conditions and transient pollution events on local O3 levels. To further elucidate the origins of high O3 concentrations, trajectory cluster analysis, trajectory sector analysis (TSA), and potential source contribution function (PSCF) analysis were conducted. The trajectory cluster analysis revealed that the northeast air mass was the main transport air mass in Chaozhou during the study period, accounting for 39.1% of occurrences. The northeast cluster C with medium-distance trajectories corresponds to higher concentration of O3, which may be the main transport pathway of O3 pollution in Chaozhou. TSA corroborates these findings, with northeast sectors 1, 2, and 3 accounting for 50.3% of trajectory residence time and contributing 52.2% to O₃ levels in Chaozhou. PSCF results further indicate potential high O₃ sources from the northeast, especially in autumn. This comprehensive analysis suggests that Chaozhou’s elevated O3 levels are influenced by both regional transport from the northeast and local emissions. These findings offer crucial insights into the temporal dynamics of surface O3 in Chaozhou, paving the way for more effective and targeted air quality management strategies.

Robust off-grid analyser for autonomous remote in-situ monitoring of nitrate and nitrite in water

An off-grid, internet-of-things (IoT) connected ion chromatography analyser was developed for the real-time automated measurement of nitrate and nitrite levels in remote surface water applications. The system used KOH eluent with an AG15 guard column to achieve anion separation, in combination with a selective 235 nm UV-LED detector. A self-cleaning 3D printed Sediment Trap was developed to filter the sample before analysis, preventing silt and sediment from causing blockages and facilitating robust performance during long-term deployments. Laboratory tests showed reductions of up to 91% of total suspended solids and 61% of turbidity within the sample after a settling time of 5 min. In controlled temperature tests (7 to 40 °C), the average error in the detected concentration levels remained below 5%, indicating robust and repeatable performance of the analyser in varying environmental conditions. Two automated in-situ analysers were deployed at remote locations in West Cork, Ireland, for a period of one month. The deployments successfully demonstrated the capability of the system to detect transient pollution events, facilitating improved water-quality management of remote catchments. The analysers were monitored in real-time using a cellular IoT module and cloud-based dashboard.

Temporal variability of two contrasting transient pollution events in a pastoral stream

Two transient pollution events were monitored in a pastoral stream in southwestern Kenya to evaluate their relative contribution to diffuse pollution. Peak loads of pollutants during storm-induced transients were within 3-4 orders of magnitude higher than the short-lived (30-60 minutes) diurnal episodes provoked by in-stream activities of people and livestock. Transient yields were striking during storm-induced events; 778,000, 8,400, 550 and 100 kg day(-1) for suspended solids, BOD(5), total P and total N, respectively, compared to wet weather base flow (150, 30, 0.8 and 1.4 kg day(-1), for the same parameters, respectively). Two forms of concentration-discharge relationships were observed: increases in concentration for turbidity, suspended solids, BOD(5), total P and the faecal indicator bacteria at the peak of the stream hydrograph, and concurrent decreases in concentration for conductivity and total N. Following each storm-induced transient event, a marked improvement in water quality was observed within 48-72 hrs of the receding limb of the stream hydrograph before the next base low was established. It was concluded that storm-induced transients are exceedingly important for the mobilization of pollutants from diffuse sources but both transient events affect stream-channel processes, especially water quality, with the possibility of attendant consequences on the health of riparian inhabitants.

Elucidating public perceptions of environmental behavior: a case study of Lake Lanier

Participation of stakeholders in stewardship of the aquatic environment, including participation from members of the general public, has become much more widespread than was the case a decade or so ago. With this shift, from a former predominantly technocratic stance to something of a democratic stance on the style of management, it becomes important to elucidate public perceptions of environmental behavior. The paper examines this issue: from a rather specific perspective, where the role of time is significant; with a specific purpose in mind—for defining illustrative stakeholder aspirations for the future, whose plausibility is to be assessed against a computational model of lake behavior; and for a specific case study, Lake Lanier in the Chattahoochee watershed of Georgia, USA. Perturbations and variation in the behavior of the aquatic environment span many time frames, from the very short-term response associated with storms, infrastructure failure, transient pollution events, and so on, to the much longer-term, for instance, the biogeochemical ‘ageing’ of a lake over many decades and more. Our analysis is devoted to data from a survey of stakeholder imagination and perceptions of how the future state of Lake Lanier may evolve in the relatively short term (2–5 years) and in the long term, defined as 25+ years (the span of a generation). Overall, stakeholders are pessimistic and fear that things will be worse in the longer term. Guided largely by thinking on the perspectives of the social solidarities of Cultural Theory, extraction and analysis of sub-samples of the survey responses show that this outlook over the two frames of time is persistent, irrespective of what are, in principle, rather different ‘global’ attitudes towards the man-environment relationship. Of interest inter alia to the foresight generating procedure, by which the ‘reachability’ of stakeholder-derived futures for the lake is to be assessed using a computational model of the relevant parts of the science base, is the question of whether the same small number of priorities for further research on lake behavior is robust in the face of the rich variety of aspirations for the future inevitable in a democratic community of stakeholders.

Vulnerability of water quality in intensively developing urban watersheds

As cities grow they first impose substantial stress on their surrounding water environment, but then, as comprehensive wastewater infrastructure is installed, much of that stress is removed. It becomes possible to talk of rehabilitated watersheds, in which the river network, with its re-invigorated ecological health, passes through the urban landscape of (now) potentially intense polluting activities. Surface water quality becomes vulnerable to the transient pollution events arising from all manner of accidents, faults, failures, and contaminated-runoff events associated with the city's metabolism, including unreliability in the performance of its wastewater infrastructure. The paper examines the role of High-Performance Integrated Control (H-PIC)—a combination of real-time control (RTC) and Integrated Urban Water Management (IUWM)—as an approach essential to managing water quality in such intensively developing watersheds. Rather than promoting H-PIC as the logical stage of operations that will follow planning, design, and construction in the life cycle of an infrastructure, discussion is set in the context of the sustainability of cities, in particular, in association with a measure of sustainability expressed in terms of the frequency spectrum of disturbances to which the aquatic environment is subject. In this more strategic setting, it is argued that control engineering (for achieving H-PIC) should be seen as having relevance beyond merely its conventional interpretation of closed-loop unit-process automation, e.g., in opening up analyses of the stability and ecological resilience of an entire urban water infrastructure. It is acknowledged that “integration”, as in IUWM and H-PIC, is likely to be realized in practice, because of the need for it expressed in the highest political circles of the sustainability debate. Given this, the paper examines the implications of the ongoing shift—from the technocracy of the past century to the democracy of stakeholder participation in the present century—for the more widespread use of information and communication technologies in managing water quality in urban water environments.

Competition modifies the response of organisms to toxic disturbance

Transient pollution events have the potential to cause both direct and indirect effects on exposed assemblages, but the test designs used in the majority of toxicity studies have precluded an examination of potentially important indirect effects. Field experiments conducted in marine epifau- nal assemblages have revealed that pulse chemical disturbances from copper decrease the densities of large solitary ascidians while increasing the densities of serpulid polychaetes. Field manipulative experiments were carried out to test whether the positive effects of transient pollution events repre- sent the response of serpulids to the release from competition for space (an indirect effect of the tox- icant) or a direct positive response to the putative toxicant. Three species of serpulid polychaetes (Ficopomatus enigmaticus, Hydroides sp., and Pileolaria pseudomilitaris) responded positively to pulse copper exposures in the presence of competition, but did not display any density response to pulse copper exposures in the absence of competition for space from other recruits. Pomatoceros tae- niata displayed no response to copper exposure in the presence of competition, but was dramatically reduced in density in the absence of competition for space. This was the only species deemed sensi- tive to the frequency and intensity of pollution disturbance employed. There was no indication of a direct positive effect of the toxicant on any serpulid, confirming the hypothesis that positive responses of serpulids to copper exposure in the whole assemblage are an indirect effect of the toxi- cant mediated through competition for space. Our results show that the interaction between a pollu- tion disturbance and competition for a limiting resource can modify the response of organisms to a toxicant. Such results could not be predicted from conventional laboratory-based toxicity tests and they suggest that small-scale ecotoxicological field tests are a useful tool in predicting the impacts of pollution events in complex systems.

DIRECT AND INDIRECT EFFECTS OF REPEATED POLLUTION EVENTS ON MARINE HARD-SUBSTRATE ASSEMBLAGES

Testing the effects on organisms of a constant exposure to toxicants in uniform environments is unlikely to reflect accurately the majority of toxicant exposures in the field, and environmental managers need tools to help predict impacts especially of pulse toxicant inputs into highly variable natural environments. We investigated the effect of pulse copper pollution events on the development of sessile marine invertebrate assemblages at two sites in Port Phillip Bay, Victoria, Australia. Using a field dosing technique we created localized 2-d copper pollution events close to settlement plates. Pulses were delivered every 2, 4, 8, or 16 wk for the duration of the 16-wk experiments, and the assemblages allowed to develop under these dosing regimes. Pulse pollution events dramatically altered the assemblages at both sites predominantly through a direct negative effect on the densities of large space-occupying tunicates. Most other taxonomic groups responded positively to multiple copper pulses, which was considered a density-mediated indirect effect of the toxicant. In particular, organisms known to be good colonizers but poor competitors for space such as serpulid polychaetes occurred in densities an order of magnitude higher on plates exposed to copper pulses. The responses of the assemblages were predominantly independent of the frequency of pulse pollution events, although a single pulse exposure at the beginning of the experiment had no observable effect when censused at week 16. The impact of these transient pollution events were manifest as changes in the structure of invertebrate assemblages and could persist for some time after the agent of disturbance was removed. The effects of a single pulse copper pollution event on an established (8-wk-old) assemblage were evident for at least a further 8 wk after it occurred.

Can Benthic Macro‐Invertebrates Be Used to Assess the Impact of Pollution Incidents and Subsequent Recovery in Streams?

AbstractThis paper describes an investigation into the use of benthic invertebrates to assess impact and recovery following transient pollution events in watercourses. The study showed that benthic macro‐invertebrates can be used to assess pollution impact and recovery in streams, provided that (a) the BMWP score is 40 or more (prior to the incident) and (b) there are adequate reference conditions. Monitoring should cover the whole area impacted by the pollutant to allow for spatial variation in benthic macro‐invertebrate communities supported by the watercourse. A decision‐making strategy for the use of macro‐invertebrates in pollution‐incident monitoring is provided.

Maintenance of species dominance through pulse disturbances to a sessile marine invertebrate assemblage in Port Shelter, Hong Kong

Pollution events can be considered as disturbances to an ecosystem and have the potential to be an important structuring force within assemblages of plants and animals. Our understanding of pollution impacts will benefit from the investigation of important aspects of these disturbances such as their timing and frequency. We investigated the effect of pulse copper pollution events on the development of hard-substrate invertebrate assemblages in Port Shelter, Hong Kong. Using a field dosing technique, we created single or repeated copper pollution events of less than 100 µg l -1 close to settlement plates. In short-term experiments, pulses were delivered in either the first or the second week of substrate immersion. For longer term experiments, pulses were delivered every 2, 4, 8 or 16 wk for the duration of the 16 wk experiments and the assem- blages allowed to develop under these dosing regimes. Pulse pollution events had a dramatic effect on densities of the dominant colonizer and space occupier in short-term experiments, Hydroides elegans. The impact was observed as a change in the size structure of the population with large organisms eliminated close to copper sources while new recruits were increased in densities in the same area. Reductions in densities of bryozoans and barnacles were also observed, while a feather hydroid doubled in densities on plates exposed to copper pulses. Young assemblages recovered rapidly from the impact of a copper pulse and reduced impacts were observed from a copper pulse in Week 1 of the experiments compared to exposure in Week 2. In longer-term experiments, copper pulses also dramatically altered assemblages predom- inantly through a direct negative effect on the densities of large competitively superior colonial and solitary ascidians. In the absence of a regular pollution event, colonial and solitary as- cidians and sponges were able to establish, grow-over and/or push out the smaller, more brittle H. elegans. These good competitors were unable to establish and grow to any great size on plates exposed to copper pulses every 2 or 4 wk and under the influence of repeated pulse copper exposures H. elegans maintained its initial dominance. Assemblages exposed every 8 or 16 wk were not significantly different from undosed controls. The results provide information on the type and magnitude of sessile invertebrate responses to transient pollution events as well as an assess- ment of the time expected to 'assemblage recovery' from single or repeated pulse disturbances. This is discussed in relation to the results of identical experiments conducted in temperate cli- mates.

Dynamics of diffuse pollution from US southern watersheds

To understand the effects of diffuse pollution information on the source of pollutants, quantities in transport, mode of transport, transient nature of the pollution event, and most importantly, a consideration of remediation efforts need to be known. For example, water quality research in the Yazoo Basin uplands in Mississippi has shown sediment loads from a conventional-till upland soybean watershed to be about 19,000 kg/ha/yr, and responsible for 77–96% of P and N in transport. In contrast, sediment loads from a comparable no-till soybean watershed were only 500 kg/ha/yr, transporting about 31% of P and N in transport. Sediment loads from a nearby forested area were low, about 200 kg/ha/yr, but responsible for about 47–76% of P and N in transport. Transient pollution events are responsible for the transport of large quantities of sediment, nutrients, and pesticides; in some storm events nearly the annual load. Best management practices (BMPs) must be designed to remediate diffuse pollution and the transient nature of pollution events which can have a profound effect on the ecological health of steams and reservoirs.

Effects of short‐term pulsed ammonia exposure on fish

AbstractTwo series of laboratory experiments were undertaken to investigate the influences of exposure duration and frequency on the toxicity of short‐term pulses of ammonia to rainbow trout (Oncorhynchus mykiss Walbaum) and brown trout (Salmo trutta L.). For the investigation of exposure duration, rainbow trout were exposed to a range of unionized ammonia concentrations in single pulses of 1, 6, or 24 h, and mortality was recorded as the endpoint. For the investigation of exposure frequency, brown trout were exposed to repeated sublethal ammonia pulses of different concentrations either once or three times weekly over a period of 53 d to simulate intermittent pollution episodes. A range of endpoints were measured, including growth, gill condition, blood indices, and organ‐to‐body weight ratios. The results suggest that exposure duration and frequency are both important factors influencing the severity of effect in fish exposed to short‐term ammonia peaks. Growth, gill condition, organ weights, and hematocrit were all significantly affected by repeated exposures, particularly at the higher exposure frequency. The results of this study confirm that the duration and return period of transient pollution events are critical dimensions when considering the development of environmental quality standards for intermittent pollution.

Risk assessment approaches for ecosystem responses to transient pollution events in urban receiving waters

Alternative risk assessment approaches are reviewed for the evaluation of the ecological status and health of urban receiving waters subject to intermittent pollution events. Performance-based criteria founded on exceedance probabilities and related to the end-of-pipe discharge of chemical-specific substances comprise the conventional basis for setting regulatory standards in both North America and Europe. The difficulties and limitations of this approach, particularly in identifying realistic chronic, sub-lethal toxic risks arising from complex effluents are discussed. The potential role of Toxicity Based Criteria (TBC) for setting ecological consent limits for stormwater effluents is considered and the capabilities and limitations of Direct Toxicity Assessment (DTA) are identified. The inability of DTA procedures to satisfactorily evaluate chronic, sub-lethal risks has led to increasing interest in the potential use of in-situ biomarker techniques for the fingerprinting of stress-response properties as a means of diagnosing risk assessment for integrated urban runoff management.

EFFECTS OF SHORT-TERM PULSED AMMONIA EXPOSURE ON FISH

Two series of laboratory experiments were undertaken to investigate the influences of exposure duration and frequency on the toxicity of short-term pulses of ammonia to rainbow trout (Oncorhynchus mykiss Walbaum) and brown trout (Salmo trutta L.). For the investigation of exposure duration, rainbow trout were exposed to a range of unionized ammonia concentrations in single pulses of 1, 6, or 24 h, and mortality was recorded as the endpoint. For the investigation of exposure frequency, brown trout were exposed to repeated sublethal ammonia pulses of different concentrations either once or three times weekly over a period of 53 d to simulate intermittent pollution episodes. A range of endpoints were measured, including growth, gill condition, blood indices, and organ-to-body weight ratios. The results suggest that exposure duration and frequency are both important factors influencing the severity of effect in fish exposed to short-term ammonia peaks. Growth, gill condition, organ weights, and hematocrit were all significantly affected by repeated exposures, particularly at the higher exposure frequency. The results of this study confirm that the duration and return period of transient pollution events are critical dimensions when considering the development of environmental quality standards for intermittent pollution.

The occurrence, distribution, and remediation of transient pollution events in agricultural and silvicultural environments

Transient pollution events occur in runoff from both agricultural and silvicultural environments. In agricultural runoff, transient pollution events may be associated with sediment, nutrients, and pesticides. Depending upon hydrological conditions, these events may be responsible for most of the yearly yield of sediment, nutrients, and pesticides, and may have a profound effect on the ecological health of streams and reservoirs, limiting seasonal primary productivity, changing the balance of functional groups, and altering reproductive cycles. Transient pollution events are most noticeable in surface runoff, but are also observable in shallow ground water. Such occurrences in both runoff and shallow ground water may be associated with natural seasonal events including the fall leaching of crop residues, or with cultural activities including the application of fertilizers and pesticides. In either case, rainfall distribution and intensity become important factors in the magnitude of the transient pollution event. Best management practices (BMPs) must be designed to remediate transient pollution in agricultural storm events. Not only must total storm agrichemical loading to aquatic ecosystems be reduced, but also the transient agrichemical concentration peaks occurring within the storm hydrograph.

The occurrence, distribution, and remediation of transient pollution events in agricultural and silvicultural environments

Transient pollution events occur in runoff from both agricultural and silvicultural environments. In agricultural runoff, transient pollution events may be associated with sediment, nutrients, and pesticides. Depending upon hydrological conditions, these events may be responsible for most of the yearly yield of sediment, nutrients, and pesticides, and may have a profound effect on the ecological health of streams and reservoirs, limiting seasonal primary productivity, changing the balance of functional groups, and altering reproductive cycles. Transient pollution events are most noticeable in surface runoff, but are also observable in shallow ground water. Such occurrences in both runoff and shallow ground water may be associated with natural seasonal events including the fall leaching of crop residues, or with cultural activities including the application of fertilizers and pesticides. In either case, rainfall distribution and intensity become important factors in the magnitude of the transient pollution event. Best management practices (BMPs) must be designed to remediate transient pollution in agricultural storm events. Not only must total storm agrichemical loading to aquatic ecosystems be reduced, but also the transient agrichemical concentration peaks occurring within the storm hydrograph.

Transient pollution events: Acute risks to the aquatic environment

For the most part investments in restricting the propagation of pollutants have focused on managing a steady, invariant, average condition of the aquatic environment. In this there has been success. But the activities ofsociety, in all its forms of land use (urban, agricultural, and silvicultural), have presumably still the capacity to generate as much potential contamination of the environment as previously. It is simply that we have now placed effective barriers - our wastewater control infrastructures - between these activities of society and the surrounding environment. And just as there would be a concern for the long-term reliability of a dam structure for a water reservoir, so there must now be an increasing concern for the reliability of our wastewater control infrastructures. Such concern is generic: transient perturbations about an equilibrium are as relevant to agricultural and silvicultural control infrastructures as they are to our systems of urban sewerage and wastewater treatment. The paper assembles the diverse features of transient pollution events, their monitoring, modelling and criteria for management, in order to make a start on providing a more coherent framework for their analysis. The notion of the frequency spectrum of system perturbations is used for this purpose. In this, succinctness is achieved, so that a better appreciation of the relationships between long-term trends and high-frequency disturbances can be obtained. In particular, the problems of managing transient pollution events can be seen loosely against the backdrop of a project's life cycle, in a manner that illuminates a tension in our attitudes towards the passive and active paradigms of operating the control structures that protect the environment from pollution.

Transient pollution events: acute risks to the aquatic environment

For the most part investments in restricting the propagation of pollutants have focused on managing a steady, invariant, average condition of the aquatic environment. In this there has been success. But the activities of society, in all its forms of land use (urban, agricultural, and silvicultural), have presumably still the capacity to generate as much potential contamination of the environment as previously. It is simply that we have now placed effective barriers – our wastewater control infrastructures – between these activities of society and the surrounding environment. And just as there would be a concern for the long-term reliability of a dam structure for a water reservoir, so there must now be an increasing concern for the reliability of our wastewater control infrastructures. Such concern is generic: transient perturbations about an equilibrium are as relevant to agricultural and silvicultural control infrastructures as they are to our systems of urban sewerage and wastewater treatment. The paper assembles the diverse features of transient pollution events, their monitoring, modelling and criteria for management, in order to make a start on providing a more coherent framework for their analysis. The notion of the frequency spectrum of system perturbations is used for this purpose. In this, succinctness is achieved, so that a better appreciation of the relationships between long-term trends and high-frequency disturbances can be obtained. In particular, the problems of managing transient pollution events can be seen loosely against the backdrop of a project's life cycle, in a manner that illuminates a tension in our attitudes towards the passive and active paradigms of operating the control structures that protect the environment from pollution.

Operational Water Quality Management: Transient Events and Seasonal Variability

The practical urgency of addressing problems of the transient pollution of receiving waters by stormwater overflows has done much to assist in dismantling the restrictive assumption of a steady state that has until recently dominated analyses of water quality management. Despite this, however, there are still misconceptions about the complexity and data requirements of dynamic mathematical models, and about the capacity to exercise operational control over the hour-by-hour, day-by-day performance of a wastewater treatment plant. The paper reviews some of these misconceptions, and draws attention to the crucial need for servicing the development of models of transient behaviour with appropriately designed, specialised, monitoring exercises. Results from a case study based on the River Cam in eastern England are presented. These illustrate the impacts of stormwater discharges on the receiving water body as a function of various treatment plant designs and operational strategies. Results are also presented for a second case study, based on the Bedford Ouse River in eastern England. A dynamic model of receiving water quality has been used for assessing the scope for seasonally varying policies for the treatment of ammonium, subject to fish toxicity and in-plant oxygenation requirements. Further studies exploring the interactions between seasonally varying conditions and transient pollution events are currently in progress.