United States Clean Research Articles

Scenario Planning Management Actions to Restore Cold Water Stream Habitat: Comparing Mechanistic and Statistical Modeling Approaches

ABSTRACTUnder the United States Clean Water Act, states are required to periodically assess state waters to determine compliance with water quality criteria (including temperature) and then to develop total maximum daily loads (TMDLs) for impaired waters as necessary to bring them into compliance. We compared the performance of mechanistic stream temperature models (HeatSource, QUAL2K, and QUAL2Kw) applied to the mainstem of three TMDL watersheds (Middle Fork John Day, OR; Wind River, WA; South Fork Nooksack, WA) with that of spatial stream network (SSN) models applied to the full watersheds and used these to evaluate the potential effectiveness of restoration strategies. SSN models performed well with slightly lesser accuracy (RMSE = 0.47–0.87) for mainstem predictions than mechanistic models (RMSE = 0.4) but provided additional benefits to inform management, including information on spatial and temporal heterogeneity of restoration effectiveness throughout the watershed. Of the four scenarios considered (restoration of riparian zones to potential natural vegetation, channel narrowing, increasing flow by restricting irrigation withdrawals, and combined applications), riparian zone restoration was consistently the most effective in reducing temperatures at the outlet, mainstem, and throughout the watersheds. Predicted restoration effectiveness for thermal regimes varied significantly both within and among watersheds. A focus on water quality criteria exceedance only at the watershed outlet or along the mainstem reach can obscure knowledge of restoration potential for fish habitat in tributaries and headwaters, potential for creation of thermal refuge areas along the mainstem critical for maintaining migration corridors, and thermal regime heterogeneity across space and time.

The US Endangered Species Act and acceptable risk

The fundamental criterion for listing or delisting species under the United States Endangered Species Act (ESA) is acceptable extinction risk. But what is the meaning of “acceptable risk”? This concept has received little attention in conservation biology, and hence, the purpose of this paper is to explain acceptable risk within the context of the ESA. All complex environmental policy decisions involve trade-offs, and hence, choosing one policy from several policy options entails a comparison of the benefits, costs, and risks of all options. Acceptable-risk problems are decision problems requiring a choice among different policy options, and an acceptable risk is defined as the risk associated with the chosen policy. In general, people will accept the risk imposed by a particular policy when that policy yields sufficient net benefits. The ESA, its legislative history, and implementing regulations clearly state that species listing determinations must be based solely on science and “without reference to possible economic or other impacts” caused by the listing of that species. If economic considerations are prohibited from influencing listing decisions, then risk reduction is not constrained by cost, and therefore, the only rational choice for acceptable extinction risk is zero risk. This outcome, known as a “stopping-point problem”, is absurd, and consequently, federal agencies responsible for listing determinations are forced to issue opaque decisions that obscure their true rationale, which in turn, lead to inconsistency and improper political influence. Illustrations of acceptable risk in null hypothesis tests, the United States Clean Air Act, and minimum viable population size are also presented.

Holistic evaluation of inlet protection devices for sediment control on construction sites

To address the deleterious impacts of excess soil erosion from the construction sites, the United States Clean Water Act requires that erosion and sediment control measures (ESCs) be implemented on construction projects disturbing more than 0.4 ha. Inlet protection devices (IPDs) are a common ESC utilized on construction projects to reduce the amount of sediment entering storm sewers. In Ohio, regulatory agencies use approved, non-proprietary IPDs made from commonly available materials (e.g., silt fence, geotextile, lumber, and aggregate) to mitigate sediment on construction projects; however, these IPDs often rely on extended ponding to remove sediment and require frequent maintenance making these unsuitable for road construction projects. Commercially manufactured (i.e., proprietary) IPDs which rely on filtration to quickly dewater following rainfall may prove more practical for road construction projects. However, little research which quantitatively compares the holistic performance of these two types of IPDs in field settings has been performed to date. To address this knowledge gap, the performance of 24 proprietary IPDs was evaluated at field-scale using simulated construction site runoff and compared to three non-proprietary IPDs currently approved for use in Ohio. Bypass flows, which typically occurred due to poor IPD fit to standard drainage inlets used in Ohio transportation settings, significantly increased effluent total suspended solids (TSS) and turbidity compared to tests of IPDs where bypass did not occur. Overflow, or intentional bypass around primary IPD flow pathways during high flows, did not significantly impact effluent water quality. Despite differences in treatment mechanisms (i.e., sedimentation versus filtration), the water quality performance of non-proprietary and proprietary IPDs were not statistically different, indicating comparable sediment removal was provided by both categories. Findings from this research can provide design engineers and state regulatory agencies the necessary tools to evaluate IPD performance in road construction settings and, ultimately, alleviate the impact of excess sediment discharged from construction sites.

Demographic disparities in United States Clean Air Act PM2.5 attainment counties: assessing population living in nonattainment conditions

Demographic disparities in United States Clean Air Act PM2.5 attainment counties: assessing population living in nonattainment conditions

Disproportionate Clean Air Act violations occur in communities of color throughout the United States

The United States (U.S.) Clean Air Act seeks to prevent and abate ambient air pollution, while also providing a framework to identify and address violations. Little research has examined where or how frequently violations of the Clean Air Act occur and how marginalized communities may bear a disproportionate share of these violations, despite the fact that marginalized communities experience persistent, disproportionate pollution levels and associated health impacts. Here, we leverage data on Clean Air Act enforcement and compliance together with demographic data to show that the most serious violations of the Act—high priority violations (HPVs)—predominantly occur in communities of color throughout the U.S. Specifically, we find that the number of facilities with an HPV within communities with the largest proportion of people of color is nearly two times greater than in communities with the smallest proportion. Only 6% of facilities with an HPV address their violations within the timeframe mandated by the U.S. Environmental Protection Agency, and a larger share of facilities with an HPV in disadvantaged communities do not address their violations within this timeframe compared to facilities with an HPV in non-disadvantaged communities. Enforcing agencies should improve how violations are communicated and addressed. To this end, we suggest several ways to empower individuals and communities with easy-to-access data related to Clean Air Act violations and that enforcement practices and reporting be standardized across enforcing agencies.

The potential of carbon markets to accelerate green infrastructure based water quality trading

Green infrastructure solutions can improve in-stream water quality in lieu of building electricity-consuming gray infrastructure. Permitted under the United States Clean Water Act, these programs allow regulated utilities to trade point-source water quality obligations with non-point source mitigation efforts in the watershed. Carbon financing can provide an incentive for water quality trading. Here we combine data on impaired waters, treatment technologies, and life cycle greenhouse gas emissions in the Contiguous United States, and compare traditional treatment technologies to alternative green infrastructure. We find green infrastructure could save $15.6 billion dollars, 21.2 terawatt-hours of electricity, and 29.8 million tonnes of carbon dioxide equivalent emissions per year while sequestering over 4.2 million tonnes CO2e per year over a 40 year time horizon. Green infrastructure solutions may have the potential to generate $679 million annually in carbon credit revenue (at $20 per credit), which represents a unique opportunity to help accelerate water quality trading.

Longevity of rain gardens in Minnesota (US) as a stormwater solution: a question of homeowner motivation and satisfaction

Rain gardens are gardens with a specific purpose. Designed as a shallow depression that captures stormwater runoff from impervious surfaces, rain gardens are planted with deep-rooted, wet/dry-cycle tolerant plants that enable the water to slowly permeate and be filtered by the soil. They are used as stormwater best management practices by municipalities and organizations as part of their overall plans to meet water quality goals as mandated by the United States (US) Clean Water Act. City and watershed administrators are counting on these rain gardens to be durable, effective solutions for managing stormwater runoff. But when the rain gardens are installed in the yards of privately owned homes, control of these solutions lands on the homeowners' shoulders. How effective are the rain gardens years after installation? How do the social factors of motivation and satisfaction relate to the longevity of the rain gardens? The objective of this case study was to determine the perceived performance of residential rain gardens as well as homeowner motivation and satisfaction with them over time. Data was collected via an email survey from homeowners located in the Twin Cities of Minneapolis and St. Paul, MN, US that had installed a rain garden. Key findings include (1) almost all rain gardens performed effectively, though some were not seen as successful, (2) motivations for installing rain gardens differ widely for successful vs. challenged gardens and (3) satisfaction with the rain gardens decreases over time.

Increased Growth Synchrony of Red Spruce in Response to Acid Deposition Recovery and Climate Change across its Southern Range Extent, Southeastern USA

In a complex system of natural and human-caused disturbance, shifting climate, and documented, widespread decline and recovery of red spruce populations prior to and following the United States (US) Clean Air Act and amendments (CAAA)—all within the last century—a better understanding of the potential influence of these disturbances on the climate sensitivity and resiliency of red spruce under projected future conditions is needed. We investigated the potential recovery of annual growth in southeastern US red spruce populations following the CAAA and the influence of this recovery vs. ongoing climate change. Using a recently collected network of red spruce tree-ring data from across the southern Appalachian range, we examined temporal trends in stand-level growth and climate sensitivity in the context of acidic (acid) deposition and recovery and modern climate change. We demonstrated that in recent decades, spruce growth is becoming synchronous and climate sensitive in conjunction with a reduction in acid deposition coupled with changes in climate conditions. The emergence of synchronous growth across sites is a new phenomenon that highlights the potential of and the need for region-wide management. Our results provide a temporal perspective that can aid future management strategies in an era of reduced air pollution and a changing climate.

Mapping Health Fragility and Vulnerability in Air Pollution-Monitoring Networks in Dallas-Fort Worth.

Environmental air pollution remains a major contributor to negative health outcomes and mortality, but the relationship between socially vulnerable populations and air pollution is not well understood. Although air pollution potentially affects everyone, the combination of underlying health, socioeconomic, and demographic factors exacerbate the impact for socially vulnerable population groups, and the United States Clean Air Act (CAA) describes an obligation to protect these populations. This paper seeks to understand how air pollution monitor placement strategies and policy may neglect social vulnerabilities and therefore potentially underestimate exposure burdens in vulnerable populations. Multivariate logistic regression models were used to assess the association between being in an ozone-monitored area or not on 15 vulnerability indicators. It was found that the odds of not being in an ozone-monitored area (not covered, outside) increased for the predictor mobile homes (OR = 4.831, 95% CI [2.500-9.338] and OR = 8.066, 95% CI [4.390-14.820] for the 10 and 20 km spatial units, respectively) and decreased for the predictor multiunit structures (OR = 0.281, 95% CI [0.281-0.548] and OR = 0.130, 95% CI [0.037, 0.457] for the 10 and 20 km spatial units, respectively) and the predictor speaks English "less than well" (OR = 0.521, 95% CI [0.292-0.931] for 10 km). These results indicate that existing pollution sensor coverage may neglect areas with concentrations of highly vulnerable populations in mobile homes, and future monitoring placement policy decisions must work to address this imbalance.

Implications of Declining Ground Water and Water Quality in the US Southeastern Coastal Plain Ecoregion and Areawide Environmental Impact Statement Required for Mining in the Greater Okefenokee Swamp Basin—Part 1

Karst aquifers occur worldwide and exhibit groundwater flow responses that differ considerably from aquifers lacking fractures, bedding planes, and other karst conduits where significant and rapid groundwater flow can occur. The regional, karst Floridan aquifer system underlies the United States (US) Southeastern Coastal Plain Physiographic Region and exhibits hydrologic interconnections with overlying surficial aquifers and throughout other zones of the aquifer system, as is characteristic of other karst aquifer systems. Anthropogenic groundwater declines in this regional karst aquifer system have been documented in published literature for decades, but the impacts of those declines in this coastal plain region and the embedded ecosystems that provide essential and critical habitat for native, endemic, and federally endangered and threatened species have not been considered previously. Those anthropogenic groundwater declines reduce surfacewater levels and flows due to the capture of both groundwater and overland flow of surfacewater, resulting in induced recharge through semi-confining zones and interbasin flow through fractures and other karst conduits. This case study identifies examples from the Greater Okefenokee Swamp Basin study area and comparison areas of how those declines result in loss of historic base flow to surface waters and other capture of surface waters, ultimately increasing saltwater intrusion. Those results alter and degrade the physical, chemical, and biological integrity of the nation’s waters, in violation of the US Clean Water Act (CWA) of 1972. Historic groundwater declines from mining and other anthropogenic groundwater withdrawals from this regional karst aquifer system already threaten the survival and recovery of federally endangered and threatened species, as well as existing and proposed critical habitat for those species within this regional extent, in violation of the Endangered Species Act (ESA) of 1973. This case study and its companion publication (Part 2) appear to be the first to provide scientific support for this regional karst aquifer system as the unifying factor in habitat responses to irreversible groundwater impacts on aquatic and marine ecosystems. These adverse impacts strongly suggest that the extent of the regional Floridan aquifer system should be designated as the Southeastern Coastal Plain Ecoregion for the purpose of managing natural resources. Mining activities continue to expand in our study area, which is the Greater Okefenokee Swamp Basin. Despite that fact, no comprehensive Areawide Environmental Impact Statement (AEIS), similar to the AEIS required for phosphate mining within the Central Florida Phosphate District (CFPD) approximately a decade ago has been conducted for any of the numerous mining projects that are occurring and are proposed within the Greater Okefenokee Swamp Basin. This case study also provides examples of why a comprehensive AEIS is essential to consider all of the adverse direct, indirect, and cumulative impacts of those mining activities to the CWA, the ESA, and the irreversible losses to local economies, because federal agencies responsible for considering those adverse impacts rely on public comments to identify those adverse impacts. The mining activities authorized throughout the regional Floridan aquifer system under Category 44 Nationwide Permits (NWP) result in the same type of adverse impacts as the mining activities evaluated under Individual Permits in that region. Therefore, those Category 44 NWP mining activities also should be required to obtain Individual Permits and be evaluated under an AEIS in the Greater Okefenokee Swamp Basin. This case study also describes how Florida’s assumption of the CWA Section 404 regulatory authority in 2020 severs four sub-basins within the Greater Okefenokee Swamp Basin study area at the state line between Florida and Georgia.

Improving Best Management Practice Decisions in Mixed Land Use and/or Municipal Watersheds: Should Approaches Be Standardized?

Best management practices (BMP) are defined in the United States Clean Water Act (CWA) as practices or measures that have been demonstrated to be successful in protecting a given water resource from nonpoint source pollution. Unfortunately, the greatest majority of BMPs remain unvalidated in terms of demonstrations of success. Further, there is not a broadly accepted or standardized process of BMP implementation and monitoring methods. Conceivably, if standardized BMP validations were a possibility, practices would be much more transferrable, comparable, and prescriptive. The purpose of this brief communication is to present a generalized yet integrated and customizable BMP decision-making process to encourage decision makers to more deliberately work towards the establishment of standardized approaches to BMP monitoring and validation in mixed-use and/or municipal watersheds. Decision-making processes and challenges to BMP implementation and monitoring are presented that should be considered to advance the practice(s) of BMP implementation. Acceptance of standard approaches may result in more organized and transferrable BMP implementation policies and increased confidence in the responsible use of taxpayer dollars through broad acceptance of methods that yield predictable and replicable results.

Incorporation of volcanic SO<sub>2</sub> emissions in the Hemispheric CMAQ (H-CMAQ) version 5.2 modeling system and assessing their impacts on sulfate aerosol over the Northern Hemisphere

Abstract. The state-of-the-science Community Multiscale Air Quality (CMAQ) Modeling System has recently been extended for hemispheric-scale modeling applications (referred to as H-CMAQ). In this study, satellite-constrained estimation of the degassing SO2 emissions from 50 volcanoes over the Northern Hemisphere is incorporated into H-CMAQ, and their impact on tropospheric sulfate aerosol (SO42-) levels is assessed for 2010. The volcanic degassing improves predictions of observations from the Acid Deposition Monitoring Network in East Asia (EANET), the United States Clean Air Status and Trends Network (CASTNET), and the United States Integrated Monitoring of Protected Visual Environments (IMPROVE). Over Asia, the increased SO42- concentrations were seen to correspond to the locations of volcanoes, especially over Japan and Indonesia. Over the USA, the largest impacts that occurred over the central Pacific were caused by including the Hawaiian Kilauea volcano, while the impacts on the continental USA were limited to the western portion during summertime. The emissions of the Soufrière Hills volcano located on the island of Montserrat in the Caribbean Sea affected the southeastern USA during the winter season. The analysis at specific sites in Hawaii and Florida also confirmed improvements in regional performance for modeled SO42- by including volcanoes SO2 emissions. At the edge of the western USA, monthly averaged SO42- enhancements greater than 0.1 µg m−3 were noted within the boundary layer (defined as surface to 750 hPa) during June–September. Investigating the change on SO42- concentration throughout the free troposphere revealed that although the considered volcanic SO2 emissions occurred at or below the middle of free troposphere (500 hPa), compared to the simulation without the volcanic source, SO42- enhancements of more than 10 % were detected up to the top of the free troposphere (250 hPa). Our model simulations and comparisons with measurements across the Northern Hemisphere indicate that the degassing volcanic SO2 emissions are an important source and should be considered in air quality model simulations assessing background SO42- levels and their source attribution.

The Formosa Case: A Step Forward on the Acceptance of Citizen-Collected Evidence in Environmental Litigation?

In June 2019, a landmark court decision (San Antonio Bay Estuarine Waterkeeper, et al. v. Formosa Plastics Corporation, et al., hereafter referred to as the Formosa ruling) was issued in Texas, where a judge found a petrochemical company liable for violating the United States Clean Water Act. The case—initiated by a civic group—was mostly built on citizen-collected evidence involving volunteer observations of plastic pellets, powder and flakes in the water over a considerable time span. The contamination could not be proven through existing data held by competent authorities because the company never filed any record of pollution (Formosa ruling, XI.A, p. 17).^{<a id="xrn1" href="#n1">1</a>} In contrast to the majority of environmental pollution cases to date, the monitoring and data collection for this case was conducted by local residents who gathered a wealth of evidence of plastic pollution in water. Through a traditional case law and text analysis of the Formosa ruling, complemented by the analysis of surrounding communications, we explore why and how citizen-collected evidence was admitted and influenced the judge’s ruling. Although the case has some unique features, we identify possible arguments and lessons learned for other citizen-run monitoring initiatives, to strengthen their voice within environmental litigation. We close by suggesting an avenue for future research—especially in the European context, where the discussion is still in its infancy.

Relationships between land use, predicted pollution loadings, and ecotoxicological assays in constructed wetlands

Environmental degradation related to uncontrolled development resulted in the passage of the United States Clean Water Act (CWA) in 1972, with the stated purpose “to restore and maintain the integrity of the nation’s waters”. Implementation of the CWA leads to increased research to develop multimetric indicators to better measure and understand the complex patterns of ecological responses to stress occurring across levels of biological, spatial, and temporal organization. One area of research is the use of integrated indices of chemical risk, ecotoxicological risk, and ecological risk to assess the impact of human activity across disturbance gradients of urbanization. Selecting relevant metrics for constructing a multimetric index requires identifying bioindicator organisms with capacities to detect signals from anthropogenic disturbances. This study explored the potential efficacy of a suite of higher plant ecotoxicological assays for use as bioindicators in ecological risk assessment along a gradient of urbanization in a wetland ecosystem. The study was conducted in the Pike River watershed (Racine, Wisconsin, USA) in six wetlands selected across a gradient of dominant land-use types (agricultural, commercial, residential, undeveloped, and industrial). MicroBioTest PhytotoxkitTM ecotoxicological assays, based on growth inhibition of three plants (Sinapis, Sorghum, and Lepidium) were used to assess sediment toxicity. The relationships between Phytotoxkit™ responses and predicted pollutant loadings calculated from surrounding land use provided clear signals of stress from watershed pollutants draining into the wetland sites. The potential for these ecotoxicological indicators to serve as biological response signatures is strong, and further research and calibration in field and microcosms studies will assist in calibrating responses for use in integrated monitoring efforts.

Biological Status Assessment of Coral Reefs in Southern Puerto Rico: Supporting Coral Reef Protection Under the U.S. Clean Water Act

States and other jurisdictions may protect coral reefs using biological water quality standards outlined by the United States Clean Water Act (CWA). Such protection will require long-term, regional monitoring of the resource using biological indicators and a probability-based sampling design. A 60-station survey targeting nearshore linear coral reef was conducted across southern Puerto Rico in December 2011 to document the status of reef inhabitants using a probabilistic, regional sampling design. The quantity, type and condition of stony corals, fish, gorgonians, and sponges were documented from each station, providing a robust representation of linear reef status and composition across the region. Fish represented 106 unique taxa and stony corals 32 unique taxa. Benthic organisms (stony corals, sponges, and gorgonians) averaged nearly 12 colonies per square meter, more than half of which were gorgonians. Assessment results can be used as a baseline to compare with future regional surveys to quantify change in reef condition over time (trend). Both temporal and spatial changes can be expected after large-scale disturbances like hurricanes Maria and Irma in 2017. The indicators and probabilistic sampling design support the long-term regional monitoring envisioned by the Environmental Protection Agency to implement CWA protections in Puerto Rico and elsewhere.

Beach Pollution Effects on Health and Productivity in California.

The United States (U.S.) Clean Water Act triggered over $1 trillion in investments in water pollution abatement. However, treated sewage discharge and untreated runoff water that are contaminated by fecal matter are discharged into California beach waters daily. Warnings are posted to thwart the public from contacting polluted coastal water, according to the California Code of Regulations (CCR). This paper evaluated the current policy by empirically examining the productivity loss, in the form of sick leave, which is caused by fecal-contaminated water along the California coast under the CCR. The findings of this study showed that Californians suffer productivity losses in the amount of 3.56 million sick leave days per year due to recreational beach water pollution. This paper also empirically examined the pollution-to-sickness graph that Cabelli’s classic study theoretically proposed. The results of the research assure that the existing water quality thresholds are still reasonably safe and appropriate, despite the thresholds being based on studies from the 1950s. The weakness of the CCR lies in its poor enforcement or compliance. Better compliance, in terms of posting pollution advisories and increasing public awareness regarding beach pollution effects on health, would lead to a significant decrease in sick leaves and a corresponding increase in productivity. Therefore, this study advocates for stronger enforcement by displaying pollution advisories and better public awareness of beach pollution effects on health.

Associations between Biotic Integrity and Sport Fish Populations in Upper Midwest, USA Rivers, with Emphasis on Smallmouth Bass.

Indices of biotic integrity (IBIs) are used to assess ecosystem health of streams and rivers. Streams and rivers with high IBI scores should support abundant and healthy populations of recreationally important sport fishes. However, the fundamental assumption that IBI scores and sport fish populations are associated needs to be examined. To verify this assumption, we tested associations between IBI scores and relative abundance of all sport fishes targeted by anglers, with emphasis on relative abundance of four size groups of smallmouth bass Micropterus dolomieu at 54 stream and river reaches in 2012 and 2013. We also tested for associations with smallmouth bass body condition and growth. A total of 13,708 fishes representing 85 species were captured including 11 sport fish species that included 571 smallmouth bass. We found that the maximum potential relative abundance of sport fishes and smallmouth bass size classes, as well as body condition of bass between 180 and 279 mm, could be predicted by IBI scores. We did not observe significant relationships with body condition of other bass size classes or with growth. Whereas abundance patterns were variable at reaches with higher IBI scores, abundance of larger, quality-sized sport fishes were more limited at reaches with IBI scores <30 that were classified as having poor biotic integrity. Maximum potential body condition was predicted to exceed 95, a condition value indicative of healthy fish, at IBI scores exceeding 50, reflective of reaches being classified as either fair, good, or excellent. These results confirm that management activities that enhance or maintain biotic integrity also support high-quality habitat for sport fish. While our findings support using IBIs as an indicator of the fishable goal specified in the United States Clean Water Act, managers should recognize that other factors not necessarily represented by the index can also limit sport fish populations.

Ecosystem services rather than designated uses should be the backbone of United States Clean Water Act programs.

Ecosystem services rather than designated uses should be the backbone of United States Clean Water Act programs.

Use of a heated graphite scrubber as a means of reducing interferences in UV-absorbance measurements of atmospheric ozone

Abstract. A new solid-phase scrubber for use in conventional ozone (O3) photometers was investigated as a means of reducing interferences from other UV-absorbing species and water vapor. It was found that when heated to 100–130 °C, a tubular graphite scrubber efficiently removed up to 500 ppb ozone and ozone monitors using the heated graphite scrubber were found to be less susceptible to interferences from water vapor, mercury vapor, and aromatic volatile organic compounds (VOCs) compared to conventional metal oxide scrubbers. Ambient measurements from a graphite scrubber-equipped photometer and a co-located Federal equivalent method (FEM) ozone analyzer showed excellent agreement over 38 days of measurements and indicated no loss in the scrubber's ability to remove ozone when operated at 130 °C. The use of a heated graphite scrubber was found to reduce the interference from mercury vapor to ≤ 3 % of that obtained using a packed-bed Hopcalite scrubber. For a series of substituted aromatic compounds (ranging in volatility and absorption cross section at 253.7 nm), the graphite scrubber was observed to consistently exhibit reduced levels of interference, typically by factors of 2.5 to 20 less than with Hopcalite. Conventional solid-phase scrubbers also exhibited complex VOC adsorption and desorption characteristics that were dependent upon the relative humidity (RH), volatility of the VOC, and the available surface area of the scrubber. This complex behavior involving humidity is avoided by use of a heated graphite scrubber. These results suggest that heated graphite scrubbers could be substituted in most ozone photometers as a means of reducing interferences from other UV-absorbing species found in the atmosphere. This could be particularly important in ozone monitoring for compliance with the United States (U.S.) Clean Air Act or for use in VOC-rich environments such as in smog chambers and monitoring indoor air quality.

Geochemistry of Trace Elements as one of the Important Coal Quality Parameter: An Example from Balingian Coal, Malaysia

Ash and sulphur are the two main variables that influence coal quality and are therefore very important contractual parameters in a coal supply agreement. Coal which is low in ash yield and sulphur content is considered as ‘cleaned coal’. Nonetheless, combustion of coal is also known to release toxic trace elements, which are known or suspected to be carcinogenic and may also cause respiratory problems, pregnancy complications, premature mortality and possibly a wide range of health problems. The two traditionally used coal quality parameters have proven to be insufficient for defining ‘cleaned coal’. This is evidenced by the low ash and low sulphur Balingian coals that is seen as relatively safe in environmental terms, but still contains high concentrations of potentially hazardous trace elements which may pose health and environmental threats during coal combustion. Therefore, a comprehensive assessment of coal quality should also include information on concentration, spatial distribution and modes of occurrence of trace elements, particularly the 15 potentially hazardous trace elements identified by the United States Clean Air Act Amendments (1990).