Land Contamination Study of Brickwork Factory
Executive Summary
This study investigates soil and groundwater contamination caused by the brickwork factory. The purpose is to understand how daily operations and facilities contribute to pollution, and how this impacts human health and environmental quality.
Legal Context
Risk Based Remediation Goals (RBRGs) and Guidance Notes provide the framework for assessing contamination and remediation. These guidelines protect human health and ensure environmental preservation.
1.2.1. Risk Based Remediation Goals for Contaminated Land Management
| Object | Aims | Benefit |
|---|---|---|
| A guideline about the protection of the health of humans which will be impacted by land contamination by chemicals, and this guideline can be the elevation criteria of land contamination for most of the land in Hong Kong | To protect the health of humans who are exposed to the land contamination environment | Can determine a designation level of land contamination by a digitization chemical concentrate. On the other hand, this goal is also a reminder to the government to treat the contaminated land, preserve the environmental quality and human health |
| The limitation criteria about the 54 concern chemical concentration that contains on the ground soil in different types including VOCs, metals, etc. |
1.2.2. Guidance Note for Contaminated Land Assessment and Remediation
| Object | Aims |
|---|---|
| Indicated that no matter the remediation after contamination or contamination possible case in the future, like land contamination generated by construction work conducted in the future | To provide clear guidance about the methodology to conduct site assessment, and suggest the remedial measure to clean the contaminated area to related stakeholders for reference |
| Project proponent needs to determine that it is necessary to conduct contamination assessment or not to minimize the pollution |
Sampling Strategy and Laboratory Techniques
3.1. Sampling Strategy
In the sampling location choosing strategy, this project has been chosen 2 kinds of strategies-- the sampling location that are surrounding the brickwork factory and sampling at the location that have the high risk in environment quality after polluted by chemical substances. The main reason is it is believe that sampling at the position that near the factory (pollution source) can be reflect the actual situation of land contamination, the concentration of hazard chemical in the underground soil at the position near the pollution source will be higher than the position that have a distant to pollution source, based on the chemical substance will be adsorb by soil or groundwater when the chemical substances are diffuse. In addition, chosen the location that have the high risk in environment quality after polluted by chemical substances like Rowletch Burn which impact by the surface water from green end of the site is a good opportunity to show how high level of chemical substances generate from factory influent, destroy the environment quality of those area. Although the chemical substances concentration may be decrease through the process of, but the risk of land pollution of those area is still appearing. In addition, after reviewing the underlying strata of those sampling locations, the location with thin made ground must be choose as the sampling location because of the high risk of land contamination if the made ground is thin.
Window Sampling
Window Sampling are applied in this project, to detect the chemical concentration of the underground soil at the location near the brickwork factory. Window sampling is a technique that utilize a metal tube to take the soil sample and view the soil sample by layer. The advantage of Window Sampling is these techniques can let the sampler to view the soil contamination situation immediately at the same time. In addition, Window Sampling is also a low-cost land contamination sampling method and utilize Window Sampling can sampling at different position in one day, it is convenient if it is necessary to getting the data immediately. But utilize Window Sampling can only detect the land contamination in a shallow depth, it cannot detect the contamination at deep position, let the sampling result not comprehensive.[1] For the aspect of sampling design, it is mention above that the sampling location will be choose at the location with thin made ground and near the pollution source and possible to contaminate by pollution source will be the sampling location choosing strategy of sampling design. For the aspect of the depth of sampling, the strategy will be trying to be sampling at soil layer at 4 sampling location near factory and 10mto 50m at the north of the site, the reason will be consider that chemical will be penetrate to underground soil layer at a short time when the chemical still not yet to spread out of the site. On the other hand, chemical substances may spread to surface water or underground water and then go out of the site through water flow, after the chemical substances penetrate to the soil layer, the chemical substances may spreading continue, so it is necessary to sampling at the different layer at the north of the site (the possible location of pollution by factory discharge). For the aspect of substances that will analyze for, metal is the main object to analyze, and other types of chemical like VOCs, SVOCs etc. are also the object of analyze in this sampling base on the producing work and daily operation of brickwork factory will generate a large among of hazard chemical substances and it is possible that those substances will be penetrate to underground and spread to surrounding environment.
Results
Window Sampling Results (WS1–WS4)
| Analyte | WS1 Mean | WS1 Max | WS2 Mean | WS2 Max | WS3 Mean | WS3 Max | WS4 Mean | WS4 Max |
|---|---|---|---|---|---|---|---|---|
| Soil organic matter (%) | 4.93 | 5.6 | 2.56 | 2.56 | 5.16 | 7.91 | 1.76 | 2.13 |
| Arsenic (mg/kg) | 5 | 5 | 6 | 6 | 6 | 8 | 4.33 | 5 |
| Cadmium (mg/kg) | 0.2 | 0.2 | 0.3 | 0.3 | 0.43 | 0.6 | <0.2 | <0.2 |
| Chromium (mg/kg) | 17.3 | 34 | 18 | 18 | 21.6 | 26 | 24.3 | 26 |
| Copper (mg/kg) | 244 | 288 | 71 | 71 | 38.6 | 70 | 17 | 18 |
| Lead (mg/kg) | 95 | 123 | 70 | 70 | 98.6 | 264 | 12.3 | 15 |
| Mercury (mg/kg) | 0.4 | 0.9 | <0.5 | <0.5 | <0.5 | <0.5 | <0.5 | <0.5 |
| Nickel (mg/kg) | 24.7 | 34 | 32 | 32 | 29 | 45 | 26.3 | 30 |
| Selenium (mg/kg) | <0.3 | <0.3 | 0.4 | 0.4 | <0.3 | <0.3 | <0.3 | <0.3 |
| Zinc (mg/kg) | 249.3 | 345 | 112 | 112 | 279 | 1011 | 44.3 | 50 |
| Phenols (mg/kg) | <0.5 | <0.5 | <0.5 | <0.5 | 1 | 1 | <0.5 | <0.5 |
| Benzene (mg/kg) | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 |
| Toluene (mg/kg) | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 |
| Ethylbenzene (mg/kg) | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 |
| Total xylenes (mg/kg) | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 |
Sampling Results (10M–Sediment)
| Analyte | 10M | 1st | 20M | 30M | 40M | 50M | Far Bank 1 | Far Bank 2 | Sediment | Average | Maximum |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Cr | 35.2 | 36.8 | 31.2 | 31.4 | 36.8 | 37.4 | 60 | 86.7 | 33.5 | 43.2 | 86.7 |
| Co | 43.3 | 51.1 | 38.1 | 31.6 | 42.7 | 47.3 | 49.6 | 47.9 | 40 | 43.5 | 51.1 |
| Ni | 31.3 | 31.1 | 38.7 | 38.6 | 33.2 | 38.8 | 47.3 | 47.1 | 61.8 | 40.9 | 61.8 |
| Cu | 60.8 | 82.3 | 61.9 | 62 | 50.5 | 45.2 | 141.4 | 148.5 | 57 | 78.8 | 148.5 |
| Zn | 270.3 | 353.6 | 293.5 | 310 | 276.7 | 255.7 | 571.2 | 640.7 | 189.6 | 351.3 | 640.7 |
| As | 7.6 | 8 | 6 | 6.7 | 7.3 | 5.8 | 8.6 | 10.9 | 10.8 | 8.0 | 10.9 |
| Mo | 4.4 | 6.4 | 5.2 | 5 | 4.9 | 4.2 | 9.5 | 9.7 | 3.6 | 5.9 | 9.7 |
| Cd | 1.1 | 0.9 | 1.2 | 0.9 | 0.4 | 0.8 | 0.3 | 0.8 | 1 | 0.8 | 1.2 |
| Sn | 9.6 | 17.8 | 11.1 | 8.7 | 6.6 | 5.1 | 26.6 | 27.5 | 38.5 | 16.8 | 38.5 |
| Sb | 10.6 | 13.5 | 12.9 | 9.4 | 5.6 | 3.5 | 11.6 | 10.2 | 6 | 9.3 | 13.5 |
| Ba | 5445 | 4076 | 5368 | 3430 | 1223 | 876.5 | 901.3 | 946.7 | 2276 | 2726.9 | 5445 |
| Hg | 2.1 | 2.1 | 2.1 | 2.2 | 1.9 | 2 | 2.1 | 2.2 | 2.3 | 2.1 | 2.3 |
| Pb | 117.1 | 199.8 | 120.6 | 127.4 | 99.4 | 87.1 | 327.5 | 332 | 109.5 | 168.9 | 332 |
4.2. Result Description
The survey were conduct at 13 positions inside and outside the site, those surveying positions are involved different kinds of chemcial substances and measuring depth. The result has been shown in the table and graph above.
For the aspect of Window Sampling result at WS1, it shows that Zinc is the main chemical substances contain in the underground base on Zinc have the highest concentrate in maximum and average concentration (345mg/kg in 1.6-1.8m, 249.3 mg/kg in average) among all the chemical substances. Higher than other substances with at least 2.2% in average. It shows that Zinc are more appear at least 19.8% It shows that Zinc are more appear at WS1. For the aspect of WS2, at same as WS1, Zinc is also the chemical substances that have the highest concentration in the underground. The maximum and average concentration of Zinc at WS2 are 112mg/kg in average, it is higher than other substances with at least 57.7%. In addition, Copper and Lead are also the main contamination source at WS2, two chemical substances have the nearest concentration with 71 and 70mg/kg in average. It shows that Zinc are the main contamination source at WS2, and the mining work is conduct nearby. For the aspect of WS3, also as same as WS1 and WS2, Zinc are the highest concentration chemical substances. The maximum and average concentration of Zinc in WS3 are 279mg/kg and 1011mg/kg in 0-0.3m, it is higher than other substances with at least 183% in average. For the aspect of WS4, PAHs become the highest concentration chemical substances in the underground of WS4 with maximum and average concentration of PAHs are 232mg/kg in 1.6-2.6m and 146 mg/kg respectively with percentage 364% at least, it shows that the chemical substances in the underground of WS4 are concentration to one type of chemical substances are 232mg/kg and 146 mg/kg respectively. It is higher than other chemical with 231.8%, it shows that PAHs have the higher level of impact to underground soil and water of WS4.
To view by the percentage to RBGR limit, Lead and Zinc measure at WS3 has the highest percentage with 0.7-11.5% to 0.6-10.11%, means that the land contamination by Lead and Zinc at WS3 are closest to excess, although the percentage of concentration measured to RBRGs Limit are not high but still have the risk of land contamination impact to human health and environmental quality.
For the aspect of survey result of 10M-Sediment, it shows that Ba is the highest concentration among survey point 10M to Sediment, and also in the average concentration. In survey result in 10M-Sediment, the highest concentration of Ba was measured at 10M with 5445b mg/kg and 2726.9 mg/kg for average concentration. Then Zinc is the second highest concentration among all the chemical measured with average and maximum concentration 351.7 and 640.7mg/kg
Discussion and Recommendations
5.1 Land Contamination at factory site
To view the potential pollution sources, in window sampling, it is mentioned that the land contamination situation of WS1 and WS3 are more serious than WS2 and WS4, become the main pollution source of factory. For the aspect of WS3, the position of WS3 is located near the LPG storage tank and unsurfaced quarry plant storage area which contain mobile fuel bowser. Quarry plant storage area is a unsurfaced land area, chemical like hydrocarbon which generate by LPG leaking based on it is more easy to infiltrate to underground soil when contact with rainwater because the underground soil do not influence of site drainage to land contamination, at WS3, the potential groundwater pollution source will be from the green at the north of the site to Rowletch Burn, before the water discharge to the river Rowletch Burn, water will reduce the suspended soil through settlement system catch pit, on the other hand, a part of the water discharge will be contain on site, means that discharge water will not spread out of the site, so the measurements mention be reduce the groundwater pollution at WS3 and surrounding area at a certain level.
At WS1, it is located at clay stockpiles, as same as WS3, the area of clay stockpiles is also an unsurfaced land, it is estimate that the land contamination situation is similar to WS3, the metal like Chromium, Cadmium, Copper etc. may be penetrate to underground soil and diffuse to underground soil at the surrounding environment. According to site conceptual model. To view the underground water pollution of WS1, the location of WS1 is near the settlement pond, the settlement pond is a pond that contain waste water that contain clay particles, it is sure that the waste water will pass through the underground of WS1 which is shown in conceptual model. The land contamination risk from chemical substances and waste water to human health and environment quality are appear. [1]
5.2. Land Contamination at the north of the site
The land contamination at the north of the site are associated with land contamination at factory site because the chemical like metal have the character of spreading that has mentioned above, the land contamination at the north of the site are also facing the risk of health damage and destroy the environment quality. According to the result, Ba at 10M is the highest concentration chemical substances with 5445 mg/kg, and the second highest concentration chemical is Zinc with 189.6-640.7. According to the conceptual model. The source of Ba and Zinc will be from the waste water discharge and land contaminants spreading by groundwater, because the location of 10M to Sediment are far from the pollution source, it is possible that the land contamination is from another place. For the relationship between land contamination to underlying strata, the underlying strata with thin made ground will be have higher risk of land contamination. According to the cross-section underlying strata model, borehole 4,5,6 have the thinnest made ground, the potential land contamination source is from metal and waste oil penetrate above the ground, although some of the chemical substances will be obstruct by made ground, but there are still have high risk in underground soil contaminate by hazard substances of metal and waste oil.
5.3. Health Impact of land contamination
The pollutants of land contamination in case mention above are mainly come from metal. Copper and Chromium are the chemical mention above and both will cause health risk to people who work or live near copper process smelter. The illness case from contact with copper for a long time can be divide into slight to serious, headache, stomachaches, diarrhea at best, damage the liver and kidney and death at worst. Copper poisoning can cause hepatic cirrhosis, brain damage etc. [2],[3] For the aspect of Chromium, excess to adsorb Chromium are carcinogenic, people who exposure under Chromium are possible to get lung cancer, liver cancer and kidney cancer, for more serious, Chromium will cause people to death. In addition, the hazard of Chromium to health can view by its oxidation state, Chromium in hexavalent form is toxic, excess to adsorb hexavalent form Chromium can be get the illness relate to throat, bronchus and Respiratory tract like wheezing and bronchospasms.
5.4. Environment Impact of land contamination
For the aspect of Copper, Copper is a metal that cannot easy to break down, so Copper will accumulate in the soil, it has very low survival opportunities of vegetations if the soil accumulates numerous of Copper, the vegetation coverage will be decrease in those places. Although Copper are attaches by organic matter and minerals when it is going into underground soil and release to groundwater, but Copper will travel for a long distance by surface water, so Copper still have a risk to water pollution of surrounding environment.[4],[5]
5.5. Recommendations
5.5.1. Cover System
The purpose to utilize Cover System in land contamination recommendation is to block the way of contaminators to pollute the receptors (soil and water), the obvious benefit of Cover System is remove the risk of chemical substances generated penetrate to underground soil and water to protect human health and environment quality like provide a suitable medium for vegetation to growth. For the aspect of material utilize as Cover System, natural soil material, clay etc. is the common material utilize, and the most effective material are membranes concrete and soils mixed with cement or bentonite because those have the character of decrease the permeability, to be a barrier between underground soil or water and contaminators above the ground, prevent cross-contamination of two things..It is sure that this is a cheaper method among all the recommendations base on this method just need to add a low permeability material although a low permeability material But the problem of cover system is cover system still not yet to solve the problem of original contamination source underground, because cover system just solve the problem of contamination from contamination source above the ground to underground, and the underground contamination source still not yet remove, contamination source will continue to spread the hazard substances to pollute the underground soil and water.
5.5.2. Vertical barrier systems
Vertical barrier systems are a system to focus on both soil and groundwater contamination include fresh water, salt water. The operation principle of Vertical barrier systems is to build a vertical underground wall to trap the horizontal flow of contaminants at underground water and soil, prevent the horizontal diffusion of contaminants at underground soil and water.[6], the hazard chemical substances contain at underground water are block by the board of vertical barrier systems, so the land contamination at underground water can be obstruct. For the aspect of cost compare to Cover System, this method may be more expensive base on this method involve to build an underground wall, dig an underground hole and build a pump house, the construction fee is expensive than utilize cover system. But the effective is higher than utilize cover system because this method is focusing on solve the underground pollution, involve take away the contaminated water let contaminated water cannot spread to underground water layer to increase the pollution rate and build a wall to isolate the polluted and unpolluted to avoid underground soil pollution.