Regional Comparison of Impacts from Seven Australian Coal Mine Wastewater Discharges on Downstream River Sediment Chemistry, Sydney Basin, New south Wales Australia

This study investigates the accumulation of licensed and regulated coal mine wastewater pollutants from seven coal mines on each mines respective receiving waterways river sediments. Results from this study shows that the coal mine wastewater pollutants are accumulating within river sediments downstream of the coal mine wastewater inflows at varying levels often greater than the ANZECC guidelines for sediment and often above reference condition sediment concentrations. This is of great concern as these pollutants will likely continue to persist in the river sediment and eventually become legacy pollutants. Coal mine wastewater discharges in New South Wales are regulated by the New South Wales Environmental Protection Authority [NSW EPA] and environmental protection of receiving waterways is implemented through Environmental Protection Licenses. Environmental Protection Licenses set discharge limits for water quality and chemical concentrations within the coal mine waste waters. Though they do not take into account river sediment concentrations. It appears water column pollution regulation at these coal mines is in fact failing to protect the environment whilst still regulated and will continue into the future post mining, licensing and regulation. Water column regulation may well be impractical in protecting the environment as it appears that water column concentrations do not portray the overall environmental impact. It is recommended that the New South Wales Environmental Protection Authority investigate these findings and continue to improve water column pollutant limits as to alleviate the continued accumulation and magnification of the contaminants.


Introduction
Coal mining practices are well documented to contribute to an array of differing environmental problems including surface and or ground water pollution. Surface water pollution is a major environmental problem associated with coal mining and it occurs through the discharge of mine waters that are contaminated by various disturbances associated with mining practices [1][2][3]. Water pollution from coal mining occurs as large volumes of surface and groundwater are required to be removed from most underground coal mines. Without this, groundwater would flood most sections of the underground mining operation [1,4].
Coal mine waste water will often be contaminated due to the disturbance of the local geology associated with mining activities. The exact nature of the water contamination will vary depending on local factors such as groundwater geochemistry, hydrology and mineralogy of the local strata [4]. Water pollution impacts attributed to treated coal mine waste waters discharged to surface waters often includes changes to pH, elevated salinity, modified stream ionic Discharges on Downstream River Sediment Chemistry, Sydney Basin, New south Wales Australia composition and elevated heavy metals [5][6][7][8][9][10].
Aquatic ecosystems are often more highly sensitive to contamination from anthropogenic activities, especially as waterways are often used as sources of discharge for many industrial wastes [11]. River sediments are often heavily polluted from the mine wastewater discharges as the heavy metals become water soluble once oxygenated and discharged, often falling out of the water column and accumulating in river sediments often remaining indefinitely [12][13][14][15][16][17]. Heavy metal contamination within aquatic environments can persist much longer than terrestrial organic pollutants. This is due to the lack of a "biodegradation function" of heavy metals in aquatic ecosystems in comparison to a terrestrial ecosystem [18,19].
The local geology of the study area is described as part of the sedimentary sequence deposited throughout the Sydney Basin. This sedimentary sequence comprises of many layers including the marine dominated Shoalhaven Group, the Illawarra Coal Measures, the Narrabeen and Hawkesbury Sandstone Groups, the Wianamatta Group and small pockets of Basalt flows [20][21]. The Illawarra Coal Measure Group is divided into two sub groups, the Nile sub group and the Charbon sub group. The Nile subgroup is described as having marine influences whilst the Charbon subgroup is described as being peat influenced and contains large deposits of economically important coal seams [20][21]. Minerology of most Australian Coals are said to be dominated by phosphates, carbonates, sulphides, silicates and other crystalline mineral groups [22].
There is a rich literature on coal mines and water pollution in some parts of the world, such as the United States which includes many regional studies of active and inactive mines [3, 23 and 24]. One major data gap is that there have been very few studies involving sediment chemistry [none in Australia] comparing sediment contamination impacts from a regional group of coal mines that discharge waste waters. This relative lack of sediment contamination studies from Australian coal mines is a large scientific gap and requires intensive research. Especially when waterways sediment legacy pollution in many other settings is so well understood.
Coal mine wastewater discharges in New South Wales are regulated by the New South Wales Environmental Protection Authority [NSW EPA] and environmental protection of receiving waterways is implemented through Environmental Protection Licenses [EPL's], under the Protection of the Environment Operations Act 1997 [POEO Act]. EPL's set discharge limits for water quality and chemical properties in which coal mine waste waters that are discharged to the environment must adhere to the studies [6 and 7].
We hypothesize that the heavy metal contamination of the water column is subsequently bioaccumulating and magnifying within the river sediments.

Study Sites
This study investigates river sediments from waterways receiving wastewater from seven coal mines in the Sydney Basin. Four are located within the Greater Blue Mountains area. They are Angus Place, Canyon, Clarence and Springvale Collieries. Three mines are located in the Greater Southern Highlands area, those being Berrima [Medway], Tahmoor and Westcliff Collieries [ Figure 1]. The geology of all mine locations share many similarities as they all extract coal from various seams within the Illawarra coal measures spanning the southern and western coalfields within the greater Sydney Basin [20, 21 and 22].

Sediment Sampling
Sediment samples were collected on one occasion from upstream and downstream of each coal mines wastewater inflow other than for Angus Place Colliery [Kangaroo Creek]. This was due to no upstream location being available. A nearby naturally dilute reference stream was used as its paired upstream sample location [Cox's River]. This was achieved by sampling river sediments in a zone of accumulated sediment, following standard methods recommended by the Victorian EPA [25]. Samples were placed into sealed glass sampling jars supplied by a commercial laboratory and stored. Three replicated samples were collected and analysed using standard methods [APHA 1998] by Envirolab [Chatswood, NSW] a National Associations of Testing Authorities accredited laboratory for the following pollutants [Barium, Cobalt, Copper, Lithium, Manganese, Nickel, Strontium and Zinc.].

Data Analysis and Guideline Comparison
For univariate data analysis Students t-test were used to test for differences in river sediment chemistry between samples upstream versus downstream of each mine waste inflows. Results

Results
Barium recorded statistically significant differences between upstream and downstream samples for all mines other than Westcliff Colliery when analysed through Students t-Test [ Springvale Creek barium increased over four times from an upstream mean of 115.7 mg/kg to a mean of 490 mg/kg below the coal mine waste water discharge. Dalpura Creek reference recorded the lowest barium of this study with a mean of 1.33 mg/kg increasing to 2.8 mg/kg downstream. Wollangambe river also recorded low reference barium of 3.0 mg/kg upstream increasing eight times to 25 mg/kg below the discharge. The Wingecarribee River above Berrima [Medway] Collieries wastewater discharge recorded a mean of 41.4 mg/kg increasing over 16 times to a mean of 685 m/kg. The Bargo River reference site recorded low barium concentrations of 5.5 mg/kg similar to Dalpura Creek and the Wollanganbe River. This increased nearly ten times to a mean of 54.5 mg/kg below Tahmoor Collieries wastewater  discharge [table 1   Cobalt was found to be statistically significantly different for Sawyers Swamp, Cox's River/Kangaroo Creek, Dalpura Creek, the Wollangambe River and the Wingecarribee River between upstream and downstream sample locations when analysed with Students T-test [  Copper was found to be statistically significantly different for Sawyers Swamp, Cox's River/Kangaroo Creek, the Wollangambe River, the Wingecarribee River and the Georges River when analysed with Students T-test between upstream and downstream sample locations [table 1]. The ANZECC 2000 ISQG-Low guideline for copper in sediment is 65 mg/kg which is above the findings of this study. One sample stream, the Georges River recorded a decrease in copper concentrations in sediment. The Georges River recorded mean copper upstream of Westcliff Collieries waste water inflow of 3.5 mg/kg decreasing to 1 mg/kg downstream. Sawyers Swamp increased over 10 times from    Figure 5]. Manganese at all sample locations other than the Bargo River and the Georges River recorded statistically significant differences when analysed with Students T-test between upstream and downstream samples [table 1]. There is no ANZECC 2000 ISQG-Low guideline for manganese in sediment. Sawyers Swamp upstream was found to have a mean of 15 mg/kg of manganese whilst downstream manganese increased to 2425 mg/kg an increase over 160 times, the greatest increase in manganese at all sample locations. Springvale Creek increased from a mean of 416.7 mg/kg upstream of Springvale Collieries waste water discharge to 13300 mg/kg over 30 times higher than reference manganese. Kangaroo Creek below Angus Place Collieries wastewater inflow measured mean manganese of 2233.3 mg/kg whilst its paired reference stream was [mean 90.2 mg/kg]. Dalpura Creek upstream of the Canyon Colliery discharge was below laboratory detection limits in comparison downstream was 20.6 mg/kg. The Wollangambe River downstream of Clarence Collieries wastewater inflow recorded mean manganese in sediment of 6520 mg/kg whilst upstream manganese was 48.7 mg/kg this is an increase downstream over 120 the second highest increase recorded for manganese [table 1 and figure 6]. Nickel in sediment recorded statistically significant differences between upstream and downstream sample locations for all sites other that Bargo and Georges Rivers [  Strontium was found to be statistically significantly different when analysed with Students T-test between upstream and downstream for all sample streams other than the Georges River and Dalpura Creek. Dalpura Creek measured below detectable laboratory limits of strontium at both upstream and downstream sample locations [table 1]. There is no ANZECC 2000 ISQG-Low guideline for strontium in sediment. Sawyers Swamp increased 10 times downstream from a mean of 1.67 mg/kg to a mean of 16.6 mg/kg. Springvale Creek upstream recorded a mean of 11 mg/kg increasing over three times to a mean of 36.5 mg/kg downstream of Springvale Collieries waste water discharge. Cox's River recorded mean reference strontium of 6.2 mg/kg whilst its paired downstream site Kangaroo Creek recorded a mean of 41.3 mg/kg an increase over six times. The Wollangambe River upstream of Clarence Collieries waste water discharge recorded mean strontium in sediment of 0.67 mg/kg increasing slightly to 1.33 mg/kg downstream. The Wingecarribee River upstream of Berrima

Discussion
For the three parameters measured in this study [Copper, Nickel and Zinc] which have Australian sediment guidelines [ANZECC 2000 guidelines for toxicants] increased to varying degrees downstream of almost all the mines. Copper recorded increases in downstream sediment concentrations below four of the eight discharges excluding Canyon, Tahmoor and Westcliff collieries ranging from double and ten times the recorded upstream [reference] sediment loads. Although all the downstream samples were below the Australian guidelines such large increases from reference conditions are of concern. Nickel was found to increase in downstream sediments below seven of the eight waste water inflows from 3 times to 180 times the reference sediment concentrations. Four of the downstream sediment sample concentrations were above the Australian sediment guidelines for nickel in sediment [ Zinc is also of major concern at many of the coal mines with large increases measured downstream of six of the eight discharges. Zinc increased downstream of the six coal mines between 6

Conclusions
Results from this study shows that the coal mine waste water pollutants are accumulating within river sediments downstream of the coal mine waste water inflows at varying levels often greater than the ANZECC guidelines for sediment and often above reference condition sediment concentrations. This is of great concern as these pollutants will likely continue to persist in the river sediment and eventually become legacy pollutants. Of greatest concern are the levels of Nickel and Zinc in relation to the ANZECC guidelines with four downstream locations recording Zinc levels greater than the recommended levels and three locations for Nickel. Magnesium and strontium were also found the be of concern as they increased statistically significantly downstream of most mines and in large concentrations at times.
It appears water column pollution regulation at these coal mines is in fact failing to protect the environment whilst still regulated and will continue into the future post mining, licensing and regulation. Water column regulation may well be impractical in protecting the environment as it appears that water column concentrations do not portray the overall environmental impact. It is recommended that the New South Wales Environmental Protection Authority investigate these findings and continue to improve water column pollutant limits as to alleviate the continued accumulation and magnification of the contaminants.