Open Parkland Again, like the category 4 screening levels there were two scenarios. The first of which is the open parkland, here parameters were used such as female children. The reason why this parameter was used is to allow the worst-case scenario to be examined. Also, children are seen to be vulnerable receptors, this means that they will be affected by the contamination more than an adult would. In addition, another factor, which will need to be used in the Clea Model is the soil pH. This has been found out by using GIS models of Hounslow Heath which detailed the different pH's. In the case of open parkland the pH is seen to be 6.7. The pH of the soil, can determine how soluble minerals are. According to Bickelhaupt (2019), the pH can be influenced as a result of external factors such as rainwater. Another parameter used in the Clea model is the soil organic matter, this involves assessing the health of the soil. It also can assess, how much organic matter is within the soil. According to Cornell University (2008) this aspect contributes to the overall "productivity" of the soil. The soil organic matter is relevant for Hounslow Heath as it means that the productivity of the soil can be examined in order to see how the contaminants can travel through them. The soil type is another aspect which can affect the contaminants travelling through the soil, although at Hounslow Heath the soil type seems to be a similar; this is sandy loam. The soil type of sandy loam is porous, this means that the contaminants can travel easily through the soils. The exposure time and exposure frequency are parameters used. These can be described to be the important, as the exposure time includes how much contamination the receptor will receive. For example, in this scenario of open parkland, it is estimated that joggers or dog walkers will use the park for roughly 2 hours per visit. In addition, exposure frequency is how often they visit the Heath, again for this scenario the potential receptors are estimated to use it for half of the year (see figure). The last elements to be included is the actual contaminants which are found on the Heath. Like the category four screening levels not all of the contaminants were able to be fed into the model, due to it being basic. However, the table shows the different routes of contamination to the receptor, this can include oral or inhalation. Both of these are measured in Mg Kg-1. In the table (see figure) it shows that the highest level of contamination orally is for the lead, this can cause potential risks for children as the value is 1048.48 mg Kg-1. According to M Assi et al. (2016), lead is considered to be one of the most "hazardous" environmental pollutants, this is due to the contaminant being able to induce "pathological" changes in the human system especially in the kidneys. With the evidence gathered