Chlordecone was applied between 1972 and 1993 in banana fields of the French West Indies. This resulted in long-term pollution of soils and contamination of waters, aquatic biota, and crops. To assess pollution level and duration according to soil type, WISORCH, a leaching model based on first-order desorption kinetics, was developed and run. Its input parameters are soil organic carbon content (SOC) and SOC/water partitioning coefficient (Koc). It accounts for current chlordecone soil contents and drainage water concentrations. The model was valid for andosol, which indicates that neither physicochemical nor microbial degradation occurred. Dilution by previous deep tillages makes soil scrapping unrealistic.Lixiviation appeared the main way to reduce pollution. Besides the SOC and rainfall increases, Koc increased from nitisol to ferralsol and then andosol while lixiviation efficiency decreased. Consequently, pollution is bound to last for several decades for nitisol, centuries for ferralsol, and half a millennium for andosol.

In the context of nonpoint source pollution the regulator can not attribute individually the responsibility of pollution because of informational asymmetry which makes the costs of monitoring of individual emission very high. This grounds a moral hazard problem. We analyse group performance based instruments to regulate this kind of informational problem. In particular, we assess randomand collective fining schemes with respect to their deterrence and efficiency. We show that a collective fine scheme is more deterrent than a random fine scheme. However, the analysis of efficiency is less categorical between these two schemes. The efficiency depends on the number of non-compliant agents. If the number of non-compliant agents is high it is better to implement a collective fine scheme. If the number of non-compliant agents is small it is better to implement a random fine scheme.

In this article we treat the problemof nonpoint source pollution as a problem of moral hazard in group. To solve this kind of problemwe consider a group performance based tax coupled to tradable permits market. The tax is activated if the group fails to meet the ambient standard. So the role of the tax is to provide an incitation to ensure that the agents provide the abatement level necessary to achieve the standard. The role of the tradable permits market is to distribute effectively this abatement level through the price of the permits which rises with the exchange of the permits.