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1.0 INTRODUCTION
In late 1994, Broken Hill Environmental Lead Centre (ELC) established an ambient air monitoring network consisting of twenty one (21) deposition gauges, otherwise known as gravimetric samplers.
ELC is currently employing two types of dust monitoring gauges. The first type adheres to AS 3580.10.1 - 1991 specifications found in the "Methods of sampling and analysis of ambient air ; Method 10.1: Determination of particulates - Deposited matter - Gravimetric method".
Thirteen of these formally comply with the defined Australian Standard regarding deposition gauges, as is mentioned above. Eight other gauges are considered to be ‘experimental’, as they are closer to the ground than the present standards specify; their funnel face is usually at most 200mm above the soil surface. Their objective is to intercept the movement of larger particles closer to the surface, rather than the fine airborne material which the standard gauges are designed to capture. Hence, this type will be referred to as ground gauge.
The monitoring sites are distributed around the city in a informal pattern, to provide an unbiased representation of the deposition area.
Two of these are located outside the city limits; ELC18S - Stirling Vale Station and ELC19S - Stephen’s Creek Reservoir. These sites have been chosen as controls, to provide a standard against which to compare the in-city sites.
1.1 Program Objectives
Aim of the ELC’s dust monitoring network is to acquire data, in order to:
examine the possibility of a potential relationship between dust movements and weather patterns around Broken Hill; primarily in terms of wind speed, wind direction, and rainfall events
1.2 Ancillary Data Sources
Monitoring program carried out by the ELC, at present, does not stand in isolation, whether one were to consider it from an initiating or operational point of view. Indeed, at this very moment, there are dust deposition programs being carried out by the Broken Hill City Council (BHCC), who operate twelve gauges; additionally, another fifteen or so gauges are operated by the Pasminco Mining - Broken Hill (PMBH).
From the perspective of local networking, as well as its involvement in the BHCDC, it is hoped that the ELC’s monitoring program will contribute to the further understanding of the dust deposition phenomenon. This could be achieved through the ensuing data possibly being combined with the existing pool of information , both from the PMBH and BHCC sources.
2.0 OVERVIEW OF THE REPORT
This report is intended to provide a preliminary overview of ambient dust and lead deposition in Broken Hill environs, during the monitoring period of September 1995 to August 1996 .
Section 1 will summarise statistical information gained during the monitoring period, explicitly dealing with sites monitored by the Environmental Lead Centre (ELC). As mentioned above, ELC monitors two types of gauges; the first 13 sites, are fully compliant with the Australian Standards requirements. Further 8 gauges are in place on an ‘interest only’ basis, and these do not comply with any previously established standards.
Section 2 will explore effect of distance from the Line of Lode on the dust and lead deposition amongst arbitrary groupings of monitoring gauges. This investigation is based on the combination of the ELC monitoring network and the sites serviced by the Broken Hill City Council (BHCC).
Section 3 will provide a brief indication on possible relationship in dust deposition and local weather conditions, namely wind speed and direction.
3.0 SECTION ONE: Summary of ELC Network Dust and Pb Deposition
3.1 Dust Deposition - in AS compliant gauges (refer to Figures 1 and 2)
The month of November recorded by far the highest deposition of 6.78 g/m2/month. This figure was more than quadruple the monthly average for the remaining 11 months of the monitoring period. Only two other months had a mean above 2 g/m2/month, these being February and December.
Looking at individual sites, the four highest gauges included all three South Broken Hill sites, 06S, 07S ,08S, and Stirling Vale Station site, 18S. This gauge is in a relatively exposed location, with only sparse vegetation surrounding it. All other gauges were found to have a monthly average below 2.2 g/m2/month.
3.2 Pb Deposition - in AS compliant gauges (refer to Figures 3 and 4)
Network mean in lead deposition peaked in November, followed by October, with 9.08 and 6.48 mg/m2/month, respectively. There was another noted period of deposition above 6.0 mg/m2/month, occurring between June and August. Lowest amounts were found to be in April and January, 2.02 and 1.73 mg/m2/month .
Highest individual site, 09S, recorded a mean of 18.74 mg/m2/month. A cluster of the three South Broken Hill sites, ranged between 6 and 10 mg/m2/month; with remaining gauges well below 3 mg/m2/month. Two out of town locations registered yearly network lows of 0.99 and 0.43 mg/m2/month, for 18S and 19S, respectively.
3.3 Dust Deposition - in non AS-complying gauges (refer to Figures 5 and 6)
Deposition patterns have been more evident than in the AS-complying gauges. Spring months experienced a steep rise in amount of dust collected; September beginning the trend at 8g/m2/month escalating to a peak of 33g/m2/month in December. This was immediately followed by a sharp fall in January to a mere 3g/m2/month, another summer increase took place and peaked in March at 15.5g/m2/month.
Sites 21G and 10G recorded highest averages of 18.4 and 16.4 g/m2/month, respectively. Majority of the remaining gauges were found to be under 12 g/m2/month.
It is obvious that ground gauges are prone to collect more dust than their
AS-complying equivalents. The non-compliant sites are not only capturing the air-borne dust, but are also receptive to ground-dust movement, thus increasing their total dust intake.
3.4 Pb Deposition - in non AS-complying gauges (refer to Figures 7 and 8)
Spring generated a lead deposition pattern which started in September and culminated in December, with and an all-year high of 240 mg/m2/month. Another isolated peak was in March, 140 mg/m2/month.
On individual basis, highest gauges were found to near the Line of Lode. These were 10G and 15G, recording 240 and 100 mg/m2/month in lead deposition.
As in dust deposition, ground gauges far exceeded the deposition figures found in the standardized gauges. During some months, this excess was as much as 25 times the peak period average found in the AS-compliant group.
It would be interesting to see, whether this seemingly disproportional increase is due to gauge height difference alone, or whether lead is more likely to occur in ground dusts, as opposed to air-borne dust.
Figure 2.Back
Figure 4. Back
Comparison of gauge type pairs, in regard to dust and lead deposition
Most ELC sites are sampled by either the standard or ground gauge. Currently, only three locations are simultaneously sampled by both gauges of each kind. The three sites are Lakeview Park, 668 McGowan Street, and MMM Lease, parallel to Eyre Street.
All but one site confirm that ground gauges tend to attract higher deposition rates, both in terms of dust and lead. However, in 668 McGowen Street this pattern in not as evident as in the other locations.
Possible explanation could be twofold. Firstly, the sampling area is found within a residential area, where movement and generation of dust is retarded by presence of vegetation, especially lawns. Secondly, the site is surrounded by a 1.5m high fence, thus effectively stopping any ground dust movement. It is this source which could be accounting for the higher ground gauge deposition rates in Lakeview and MMM Lease sites; both of them are located in wide open areas.
Preliminary inquiry into correlation between dust and lead deposition
Australian Standards-complying sites
Initial correlation analysis yields a coefficient of correlation, r = 0.58, a value too low to consider the relationship as statistically meaningful. However, one can not ignore the fact that the lead values are more closely correlated to dust depositions during times of high dust depositions. Specifically, this covers the months of September through to March. In fact, applying the same analysis to this period alone, results in a higher r value of 0.83.
Non Australian Standards-complying sites
Correlating the two variables resulted in a coefficient of correlation r = 0.93, suggesting a strong relationship between the two. This is more pronounced throughout the whole of the monitoring period, than in the AS-complying sites.
Figure 11. Continue on through Document
Dust deposition - the deposited matter consisting of particles which are collected in the deposit gauge, and which pass through a 1mm mesh sieve
Total lead - the mass of the lead found deposited in the gauge, containing both acid and water soluble portions
6.0 LIST OF ACRONYMS
BHCC - Broken Hill City Council, the local government authority, in whose area of jurisdiction the lead dust inquest is being investigated
BHCDC - Broken Hill Collaborative Dust Committee, a loose coalition consisting of mining interests, local and state government representations whose role is to oversee the monitoring programme in the Broken Hill area. Its members operate city wide network of dust deposition gauges, the results of which are compiled in an annual report
ELC - Environmental Lead Centre, the combined project of the New South Wales Environment Protection Authority and Far West Health Service, to address, investigate and propose solutions towards resolving the environmental lead problem in Broken Hill
PMBH - Pasminco Mining Broken Hill, the only active mining company in Broken Hill involved in zinc and lead ore extraction
4.0 SECTION TWO: Effect Of Distance From The Line Of Lode On The Dust And Lead Deposition Amongst Arbitrary Groupings Of Monitoring Gauges
Section 2 will explore effect of distance from the Line of Lode on the dust and lead deposition amongst arbitrary groupings of monitoring gauges. This investigation is based on the combination of the ELC monitoring network and the sites serviced by the Broken Hill City Council (BHCC).
January 9, 2003
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